A question about the clarity of certain terms

A question about the clarity of certain terms

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In the Red Queen's depiction, a population must evolve just to be able to survive its ever-evolving natural enemies. I'm trying to refer to a state in which many natural enemies have evolved adaptive advantages against individuals in the population (as opposed to a state in which most individuals in the population are able to survive their natural enemies with little difficulty). When parasites have evolved adaptations that are dangerous to most individuals, I say they are virulent. When predators have evolved adaptations that are dangerous to most individuals, I say they are well-adapted. Is this clear?

Important Questions for CBSE Class 12 Biology Post-Fertilisation : Structures and Events

1.After double fertilisation, the following changes occur:
(i)Endosperm and embryo development.
(ii)Maturation of ovule(s) into seed(s).
(iii)Maturation of ovary into fruit.
These are collectively termed post-fertilisation events.

2.Post-fertilisation changes in floral parts:
(i)Sepals fall down or persist in few.
(ii)Petals, stamen, stigma and style fall down.
(iii)Ovary changes into fruit.
(iv)Ovules become seeds.
(v) Synergids and antipodal cells degenerate.
(vi) Central cell become endosperm. May persist or get consumed.

3.Endosperm development takes place by three methods:
(i)Nuclear type (ii)Cellular type (iii)Helobial type
(a)In nuclear type, which is a common method, the Primary Endosperm Nucleus (PEN) undergoes repeated mitotic division without cytokinesis. At this stage, the endosperm is called free nuclear endosperm.
(b)Cell wall formation occurs and the endosperm becomes cellular type. The number of free nuclei formed before cellularisation varies greatly, e.g. in coconut the water is free nuclear endosperm and surrounding white kernel is cellular endosperm

4.Embryo formation occurs when certain amount of endosperm is formed.
(i) Zygote divides by mitosis and forms proembiyo.
(ii)This results in the formation of globular and heart-shaped embryo that finally becomes horse shoe-shaped (mature embryo) having cotyledon.

5.Dicot embryo consists of two cotyledons and an embryonal axis between them:
(i)The part of embryonal axis above the level of cotyledons is the epicotyl which becomes plumule (shoot).
(ii)The part of embryonal axis below the level of cotyledons is the hypocotyl which becomes radicle (root).

6.Monocot embryo consists of only one cotyledon (called scutellum in grass family),
e.g. rice, maize plants, etc.
(i)Embryonal axis has the radicle on its lower end (hypocotyl), the radicle is covered over by an undifferentiated sheath called coleorhiza.
(ii)At the upper end (epicotyl), the embryonal axis has plumule. It is covered by a hollow foliar sheath called coleoptile.

7.Seed or fertilised ovule is the final product of sexual reproduction:
(i)It consists of seed coat, cotyledons and an embryo axis.
(ii)Non-albuminous seeds have no residual endosperm as it is completely consumed in embryo development, e.g. pea, groundnut.
(iii)Albuminous seeds retain a part of endosperm as it is not completely used up during embryo development, e.g. wheat, maize, castor, sunflower, etc.
(iv)In some seeds such as black pepper and beet, remnants of nucellus are also persistent (perisperm). Integuments of ovules harden as tough protective seed coat.
(v) Micropyle remains as a small pore in the seed coat to allow the entry of oxygen and water.
(vi) On the availability of favourable conditions, seeds germinate and later dispersed by abiotic and biotic agents.
Seeds have following advantages:
(i)Seeds help the species to spread in other areas by dispersal.
(ii)They generate new combinations leading to variations.
(iii)Seeds are stored and used as food throughout the year.
(iv)They can be used in favourable seasons depending on their viability.

8.Ovary develops into a fruit. The wall of the ovary develops into the fruit wall called
pericarp. Types of fruits:
(i)False fruits Thalamus also contributes in fruit formation, e.g. apple, strawberry, cashewnuts, etc.
(ii)True fruits These fruits develop from ovary, e.g. grapes, cucumber, etc.
(iii) Parthenocarpic fruits These fruits develop without fertilisation, e.g. banana. parthenocarpy can be induced through growth hormones and such fruits are seedless.

9.Special Cases
(i)Apomixis is the special mechanism to produce seeds without fertilisation, e.g. grass. It is a form of asexual reproduction that mimics sexual reproduction. It is useful for the hybrid industry.
The modes by which apomictic seeds can be produced are agamospery, adventive embryony, etc.
(ii)Polyembryony is the presence of more than one embryo in a seed. In many Citrus and mango varieties, some of the nucellar cells surrounding the embryo sac start dividing, protrude into the embryo sac and develop into embryos.

Previous Year Examination Questions

1 Mark Questions

1.Banana is a true fruit but is also a parthenocarpic fruit. Give reason.[Foreign 2010]
Ans.The fruit of banana is formed from the ovary, so it is a true fruit. It is a parthenocarpic fruit because the ovary develops into fruit without fertilisation and is thus, seedless.

2.Why is apple referred to as a false fruit? [HOTS All India 2010 C]
Ans.In apple, the thalamus also contributes to fruit formation. So, apples are called false fruits.

3.Name the mechanism responsible for the formation of seed without fertilisation in angiosperms. Give an example of a species of flowering plants with such seed formation.[Delhi 2010]
Ans.Apomixis is the mechanism responsible for the formation of seeds without fertilisation in angiosperms, e.g. grasses.

4.Name the part of flower that contributes to fruit formation in strawberry and guava respectively.[All India 2009 C]
Ans.(i)In strawberry, the fruit develops from the ovary, other floral parts degenerate and fall off. Thalamus also contributes to fruit formation.
(ii)In guava, the wall of ovary develops into the wall of fruit called pericarp.

2 Marks Questions

5.List the post-fertilisation events in angiosperms.[Delhi 2014]
Ans.The post-fertilisation events in angiosperms include:
(i)Endosperm and embryo development.
(ii)Maturation of ovule into seed.
(iii)Maturation of ovary into fruit

6.Some angiosperm seeds are said to be ‘albuminous’, whereas few others are said to have a perisperm, Explain each with the help of an example. [Foreign 2012]
Ans.Some angiospermic seeds are albuminous as they retain endosperm even after embryo development, i.e. not completely consumed by embryo, e.g. wheat, maize, castor.While in some angiospermic seeds remnants of nucellus are persistent which is referred to as perisperm, e.g. black pepper and beet.

7.Draw a labelled diagram of a matured embryo of a dicotyledonous plant.[All India 2014 C]
Ans.The labelled diagram of a mature embryo of a dicotyledonous plant is as given below.

8.Differentiate between albuminous and non-albuminous seeds, giving one example of each. [Delhi 2011]
Ans. Difference between albuminous and non-albuminous seeds are:

9.Banana is a parthenocarpic fruit, whereas oranges show polyembryony. How are they different from each other with respect to seeds? [hots Delhi 2009]
Ans.Since, banana is a parthenocarpic fruit, it is seedless, whereas oranges show polyembryony that leads to formation of many seeds

10.Name the cell from which the endosperm of coconut develops. Give the characteristic features of endosperm of coconut. [Delhi 2009]
Ans.In cpconut, cell formation occurs and the endosperm becomes cellular. The number of free nuclei formed before cellularisation varies greatly. The coconut water is free nuclear endosperm. It is made up of thousands of nuclei and the surrounding white kernel is the cellular endosperm.

11.Name the blank spaces A, B, C and D from the table given below.

Ans.A — Fruit wall, B — Scutellum
C — Plumule and radicle, D — Perisperm

3 Marks Questions

12.Describe endosperm development in angiosperm. [Foreign 2014]
Ans.(i)Embryo development occurs after endosperm development in angiosperms.
(ii) The three methods of endosperm development are:
(a)nuclear type (b) cellular type
(c)helobial type
(iii) Nuclear type is the common method in which triploid Primary Endosperm Nucleus (PEN) undergoes repeated mitotic division without cytokinesis. This stage is called free-nuclear endosperm.
(iv)Cell wall formation starts from the periphery and the endosperm becomes completely cellular, e.g. coconut, rice, etc.
(v)Cells of the endosperm store food materials.
(vi)Endosperm may be completely utilised by the developing embryo before the maturation of seeds as in pea, bean, mustard, etc. These seeds are called non-albuminous or endospermic seeds.
(vii) In seeds like castor, maize, coconut, rice, etc., a portion of it may remain in the mature seeds, such seeds are called albuminous or endospermic seeds

13.(i) How is apomixis different from parthenocarpy?
(ii) Describe any two modes by which apomictic seeds can be produced.[Delhi 2014 C]
Ans.(i)Parthenocarpy is development and production of seedless fruits in the absence of fertilisation, whereas apomixis refers to development of seeds and fruits, without fertilisation. So, the main difference between apomixis and parthenocarpy is that seeds are formed in former, while absent in later.
(ii) The two modes by which apomictic seeds can be produced are:
(a)Agamospermy In which the seed or embryo is derived from diploid egg ceil, formed without meiosis and syngamy. This diploid egg cell develops into embryo without undergoing fertilisation, e.g. apple,
(b)Adventive embryony The method in which diploid cells surrounding the embryo sac, e.g nucellus and integument protrude into the sac and develops into embryo. This may also lead to formation of more than one embryos in an embryo sac or ovule, leading to condition called polyembryony, e.g. Citrus,Opuntia.

14.(i) Describe the endosperm development in coconut.
(ii)Why is tender coconut considered as healthy source of nutrition?
(iii)How are pea seeds different from castor seeds with respect to endosperm? [All India 2013]
Ans.(i)Coconut endosperm formation is nuclear type. The primary endosperm nucleus undergoes nuclear division without cell wall formation.
(ii) Soft coconut is an endosperm. It is rich in nutrients like fats, proteins, carbohydrates, minerals, vitamins, etc. Hence, it is considered as a healthy source of nutrition.
(iii)The seeds of pea are non-endospermic, while castor seeds are endospermic. The endosperm in pea seeds is consumed completely during embryo development, but endosperm is not utilised in castor seeds.

15.Differentiate between perisperm and endosperm giving one example of each. [All India 2012]

16.LS of a maize grain is given below. Label the parts A, B, C and D in it. [All India 2012]

Ans.A — Pericarp
B — Scutellum (cotyledon)
C — Coleoptile
D — Coleorhiza

17.With the help of an example of each explain the following Apomixis, parthenocarpy, polyembryony. [All India 2012 c]
Ans.Apomixis The phenomenon in which seeds are produced without fertilisation is called apomixis or agamospermy, e.g. grass.
Parthenocarpy It is a commercially important process in which seedless fruit is formed without fertilisation, e.g. banana.
Polyembryony The occurrence of more than one embryo in a seed is known as polyembryony, e.g. orange.

18.Fertilisation is essential for the production of seed, but in some angiosperms seeds develop without fertilisation.
(i)Give an example of an angiosperm that produces seeds without fertilisation. Name the process.
(ii)Explain the two ways by which seeds develop without fertilisation.[All India 2009]
(i)The members of Asteraceae like sunflower produce seeds without fertilisation. The process is called apomixis.
(ii) The two ways by which cells develop without fertilisations are:
(a)A diploid egg cell is formed without meiosis and it develops without fertilisation into an embryo in some cases.
(b)In some cases, some of the cells of nucellus around the embryo sac develop into embryo, e.g. mango and citrus.

5 Marks Questions

19.(i) Explain the different ways apomictic seeds can develop. Give an example of each.
(ii)Mention one advantage of apomictic seeds to farmers.
(iii)Draw a labelled mature stage of a dicotyledonous embryo.[All India 2014]
Ans.(i) The two modes by which apomictic seeds can be produced are:
(a)Agamospermy In which the seed or embryo is derived from diploid egg ceil, formed without meiosis and syngamy. This diploid egg cell develops into embryo without undergoing fertilisation, e.g. apple,
(b)Adventive embryony The method in which diploid cells surrounding the embryo sac, e.g nucellus and integument protrude into the sac and develops into embryo. This may also lead to formation of more than one embryos in an embryo sac or ovule, leading to condition called polyembryony, e.g. Citrus,Opuntia.
(ii)The introduction of apomixis genes into hybrid seeds results in apomictic seeds, which results in asexual reproduction or production of cloned seed. But the main advantage by which these apomictic seeds are advantageous to farmers as they lower the cost of production and increase the yield. Also unlike hybrid seeds they don’t have to be produced every year and can be stored, thus saving time and money.
(iii)The labelled diagram of a mature embryo of a dicotyledonous plant is as given below.

20.(i) Why does endosperm development precede embryo development in angiosperm seeds? State the role of endosperm in mature albuminous seeds.
(ii) Describe with the help of three labelled diagrams the different embryonic stages that include mature embryo of dicot plants.[Delhi 2014]
Ans.(i)The embryo development starts only after a certain amount of endosperm is formed. It is an adaptation for assured nutrition of the developing embryo. Therefore, endosperm development precedes embryo development. The role of endosperm in mature albuminous seeds is storage of reserve food for growing embryo.
(ii)The embryonic stages during the development of mature embryo sac are:

21.(i) Mature seeds of legumes are non-albuminous. Then, can it be assumed that double fertilisation does not occur in legumes? Explain your answer,
(ii) List the differences between the embryos of dicot (pea) and monocot (grass family).[Delhi 2014 C]
Ans.(i)Seeds of legumes are non-albuminous that implies that endosperm in such seeds is completely used up in providing nutrition to developing embryo. The endosperm is formed as a result of triploid fusion, i.e. between a male gamete and two polar nuclei. This making it obvious that it cannot be formed in the absence of double fertilisation.Therefore, though the seeds of legumes are non-albuminous, it clearly states the occurrence of double fertilisation in them.
(ii) The differences between the embryos of pea and grass can be summarised as:

22.(i) Why are seeds of some grasses called apomictic? Explain.
(ii) State two reasons to convince a farmer to use a apomictic crop.[Delhi 2014 C]
Ans.(i)The seeds of some grasses develop seeds without fertilisation. It may be because a diploid egg cell develops into a embryo directly (without undergoing meiosis and syngamy) or some diploid cells of nucellus or integument surrounding the embryo sac, protrude inside and develop into embryos. This phenomenon of developing embryo and seeds without fertilisation is called apomixis and such seeds produced are referred to as apomictic.
(ii) The introduction of apomixis genes into hybrid seeds results in apomictic seeds, which results in asexual reproduction or production of cloned seed. But the main advantage by which these apomictic seeds are advantageous to farmers as they lower the cost of production and increase the yield. Also unlike hybrid seeds they don’t have to be produced every year and can be stored, thus saving time and money.

23.Give reasons why?
(i)Most zygotes in angiosperms divide only after certain amount of endosperm is formed.
(ii)Groundnut seeds are exalbuminous and castor seeds are albuminous.
(iii)Micropyle remains as a small pore in the seed coat of a seed.
(iv)Integuments of an ovule hardens and the water content is highly reduced as the seed matures.
(v)Apple and cashewnuts are not called true fruits.[All India 2011,2008]
Ans.(i)Zygotes in angiosperms mostly divide only after a certain amount of endosperm is formed as an adaptation strategy to assure nutrition for the developing embryo.
(ii) (a) Groundnut seeds are exalbuminous because the developing embryo utilises the endosperm completely. So, there is no endosperm left in the seed.
(b)Castor seeds are albuminous because endosperm is not completely used up by the developing embryo. There is some amount of endosperm left in the seeds always.
(iii) Micropyle allows entry of water and oxygen during seed germination.
(iv) During unfavourable conditions, seeds become dormant. The loss of water reduces the metabolic activity of seeds and hardens the integuments.
(v)In these fruits, thalamus contributes in fruit formation. So, they are not called true fruits

24.(i)Draw a labelled longitudinal view of an albuminous seed.
(ii) How are seeds advantageous to flowering plants?[All India 2010,2008]
Ans.(i) LS of an albuminous seed is

(ii)Advantages of seeds to flowering plants are:
(a)Provides protection to embryo in most delicate stage.
(b)Help in dispersal to spread in new habitats.
(c)Contain sufficient food reserves.
(d)Produce genetic variations.
(e)Seeds are related to pollination and fertilisation.

25.Explain the development of the zygote into an embryo and of the primary endospermic nucleus into an endosperm in a fertilised embryo sac of a dicot plant. [All India 2010 c]
Ans.Development of endosperm
(i)Embryo development occurs after endosperm development in angiosperms.
(ii) The three methods of endosperm development are:
(a)nuclear type (b) cellular type
(c)helobial type
(iii) Nuclear type is the common method in which triploid Primary Endosperm Nucleus (PEN) undergoes repeated mitotic division without cytokinesis. This stage is called free-nuclear endosperm.
(iv)Cell wall formation starts from the periphery and the endosperm becomes completely cellular, e.g. coconut, rice, etc.
(v)Cells of the endosperm store food materials.
(vi)Endosperm may be completely utilised by the developing embryo before the maturation of seeds as in pea, bean, mustard, etc. These seeds are called non-albuminous or endospermic seeds.
(vii) In seeds like castor, maize, coconut, rice, etc., a portion of it may remain in the mature seeds, such seeds are called albuminous or endospermic seeds
Embryo development in dicot plant
(i) Embryo formation starts after a certain amount of endosperm is formed.
(ii) Zygote divides by mitosis to form a proembryo.
(iii) Formation of globular and heart-shaped embryo occurs which finally becomes horse shoe-shaped mature embryo.
(iv) In dicot plant, embryo consists of two cotyledons and an embryonal axis between them.
(v)The portion of embryonal axis above the level of attachment of cotyledons is epicotyl and terminates in the plumule.
(vi)The portion of embryonal axis below the level of attachment of cotyledon is the hypocotyl, it becomes radicle (root tip).

26.(i) Trace the development of embryo after syngamy in a dicot plant.
(ii)Endosperm development precedes embryo development. Explain.
(iii)Draw a diagram of a mature dicot embryo and label cotyledons, plumule, radicle and hypocotyl in it. [All India 2009,2008]
Ans.(i) Development of embryo after syngamy.
(a)The embryo development starts only after a certain amount of endosperm is formed. It is an adaptation for assured nutrition of the developing embryo. Therefore, endosperm development precedes embryo development. The role of endosperm in mature albuminous seeds is storage of reserve food for growing embryo.
(b)The embryonic stages during the development of mature embryo sac are:

(ii) (a)The embryo development starts only after a certain amount of endosperm is formed. It is an adaptation for assured nutrition of the developing embryo. Therefore, endosperm development precedes embryo development. The role of endosperm in mature albuminous seeds is storage of reserve food for growing embryo.
(b)The embryonic stages during the development of mature embryo sac are:

(iii) Mature dicot embryo.
The labelled diagram of a mature embryo of a dicotyledonous plant is as given below.

Miscellaneous Questions

5 Marks Questions

1.(i) Draw a LS of a pistil showing pollen tube entering the embryo sac in an angiosperm and label and six parts other than stigma, style and ovary.
(ii) Write the changes a fertilised ovule undergoes within the ovary in an angiosperm plant. [All India 2013]
Ans.(i)The embryonic stages during the development of mature embryo sac are:

(ii)Changes taking place in a fertilised ovule within the ovary in an angiosperm plant are:
Unfertilised ovule —Seed
Funiculus —Present
Integument —Seed coat
(a)outer —Testa
(b)inner —Tegman
Polar nuclei —Endosperm
Nucellus —Utilised or remaining perisperm
Antipodal —Degenerate
Synergid —Degenerate
Egg —Embryo

2.(i) Name the structures which the parts A and B shown in the diagram alongside respectively develop into.
(ii)Explain the process of development which B undergoes in albuminous and exalbuminous seeds. Give one example of each of these seeds. [Foreign 2011]

Ans.(i)The part A develops into the embryo. The part B develops into the endosperm.
(ii) Endosperm formation
(a)Primary endosperm cell divides repeatedly and forms triploid endosperm nucleus.
(b)Primary endosperm nucleus undergoes successive free nuclear divisions to give rise to a number of free nuclei. At this stage, it is called free nuclear endosperm.
(c)Wall formation takes place from the periphery and proceeds towards the centre and the endosperm becomes cellular.
(d)In albuminous seeds, some amount of endosperm persists in the mature seed as the developing embryo does not consume it completely,
e.g. wheat /maize.
(e)In exalbuminous seeds, the endosperm is completely consumed by the developing embryo before seed maturation,
e.g. in pea/groundnut.

3.(i) Draw a labelled diagram of LS of an embryo of grass (any six labels).
(ii) Give reason for each of the following:
(a)Anthers of angiosperm flowers are described as dithecous.
(b)Hybrid seeds have to be produced year after year. [All India 2011]
Ans.(i) LS of grass embryo.

(ii) (a) A typical angiosperm anther is bilobed with each lobe having two thecae. So, anther is called dithecous.
(b) Hybrid seeds show segregation of traits and do not maintain the hybrid character in plants. So, they need to be produced every year and cannot be stored.

4.Explain double fertilisation and trace the post fertilisation events in sequential order leading to seed formation in a typical dicotyledonous plant.[All India 2008 C Foreign 2010]
Ans.(i) Post-fertilisation events can be traced as:

  • Development of endosperm, enlargement of seeds and fruit formation.
  • Zygote develops into an embryo.
  • Central cell becomes primary endosperm cell and the primary endosperm nucleus develops into the endosperm.
  • Antipodals and synergids degenerate.
  • Integuments develop into seed coat.
  • Ovules ripen into seeds.
  • Ovary ripens to form the fruit.

Embryo development in dicot plant
(i) Embryo formation starts after a certain amount of endosperm is formed.
(ii) Zygote divides by mitosis to form a proembryo.
(iii) Formation of globular and heart-shaped embryo occurs which finally becomes horse shoe-shaped mature embryo.
(iv) In dicot plant, embryo consists of two cotyledons and an embryonal axis between them.
(v)The portion of embryonal axis above the level of attachment of cotyledons is epicotyl and terminates in the plumule.
(vi)The portion of embryonal axis below the level of attachment of cotyledon is the hypocotyl, it becomes radicle (root tip).
Important Questions for Class 12 BiologyClass 12 BiologyNCERT Solutions Home Page


Q. 1 (a) Name the following:

(i) The process of transformation of several glucose molecules into one molecule of starch.

(ii) The point of attachment of two chromatids.

(iii) The iron containing pigment in erythrocytes.

(iv) The duct which transports urine from the kidney to the urinary bladder.

(v) The part of the brain which is concerned with memory.

(b) Explain the following terms:

(c) Given below are certain groups of terms. In each group the first pair indicates a relationship between the two terms. Rewrite and complete the second pair on a similar basis.

Example: Cytoplasm : Cytokinesis :: Nucleus : Karyokinesis.

(i) Widening of hips: Oestrogen :: Deepening of voice in males :___________.

(ii) Brain : Meninges :: Heart : ___________.

(iii) Insulin : Beta-cells :: Glucagon : _____________.

(iv) Kidney: Renal artery :: Liver : _____________.

(v) Uterus : Implantation :: Fallopian tube : __________.

(d) Given below are sets of five terms each. Rewrite the terms in correct order in a logical sequence beginning with the first word that is underlined:

(i) Stimulus, Response, Receptor, Effector, Spinal cord.

(ii) Root hair, Endodermis, Epidermis, Xylem, Cortex.

(iii) Conjunctiva, Yellow spot, Pupil, Vitreous Humour, Aqueous Humour.

(iv) Australopithecus, Cro-Magnon Man, Homo erectus, Neanderthal Man, Homo sapiens.

(v) Artery, Capillaries, Venule, Vein, Arteriole.

(e) Choose the correct answer from the four options given below:

(i) The fusion of the sperm and ovum is termed as:

(iii) Which of the following is not a natural reflex action?

B. Blinking of eyes due to strong light

C. Salivation at the sight of food

D. Sneezing when any irritant enters the nose

(iv) The structural and functional units of excretion in the human kidney is the:

(v) In a human female, ovum consists of:

B. 22 pairs of autosomes and 1 pair of sex chromosomes

C. 22 autosomes and 1 Y-chromosome

D. 22 autosomes and 1 X-chromosome

(f) Identify the ODD term in each set and name the CATEGORY to which the remaining three belong:

(i) Auxin, Ethylene, Adrenaline, Cytokinin

(ii) Tympanum, Ear ossicles, Auditory canal, Pinna

(iii) Syringes, Soiled dressings, Discarded needles, Household detergents

(iv) Exophthalmic Goiter, Simple Goitre, Cretinism, Myxoedema

(v) Adenine, Guanine, Creatinine, Cytosine

(g) Match the items given in column A with the most appropriate ones in Column B and REWRITE the correct matching pairs:

Column A Column B

(i) Biston betularia – Calcium

(ii) Testes – balance of the body

(iii) Clotting of blood – Light independent reaction

(iv) Stroma – diffusion of gases

(h) The diagram given below represents a plant movement. Answer the following question

(i) Name the tropic movement shown in the diagram.

(ii) Explain the tropic movement mentioned in (i).

(iii) Label the part marked ‘A’.

(iv) What is part A attracted to?

(v) Give an example of a plant which shows Thigmotropism.

Q. 2 (a) The diagram given below represents an experiment to prove the importance

A factor in photosynthesis. Answer the questions that follow:

(i) Which factor is being studied here?

(ii) What is the purpose of keeping KOH in the flask?

(iii) Explain the term Photosynthesis.

(iv) What will you observe when the leaf A is tested for starch?

(v) Write a well balanced chemical equation for the process of

(b) The diagram given below represents the simplified pathway of the circulation of blood. Answer the questions that follow:

(i) Name the blood vessels labelled 1 to 4.

(ii) Which blood vessel supplies oxygenated blood to the muscles of the heart? (iii) What is the importance of blood vessel labelled 5?

(iv) What is the type of blood circulation that takes place between the heart and the lungs?

(v) Draw a diagram of the different blood cells as seen in a smear of human blood.

Q. 3 (a) The diagram given below depicts a defect of the human eye which has been corrected by using a suitable lens. Answer the following questions:

(i) Name the defect that has been corrected. Which type of lens has been used for the correction?

(ii) Mention one cause for the above defect.

(iii) Where would the image have formed if the above lens was not used for correction?

(iv) Name the three concentric layers of the eyeball.

(v) Draw a neat, labelled diagram of a neuron.

(b) Give the biological reasons for the following statements:

(i) It is advisable to keep green plants in an aquarium.

(ii) Water pollution is a major cause of concern in our country.

(iii) We cannot distinguish colours in dim light.

(iv) Medical discoveries such as antibiotics and vaccinations have indirectly contributed to the sharp rise in human population.

(v) Homo sapiens sapiens is the most highly evolved form of man.

Q. 4 (a) The figure given below shows a part of a nephron. Answer the questions that follow:

(i) In which region of the kidney is the above structure present?

(ii) Label the parts numbered 1 to 4.

(iii)What is the technical term for the process that occurs in part 3?

(iv)Why is fluid X not called urine? Justify your answer.

(v) Draw a neat, labelled diagram of the urinary system of man.

(b) Differentiate between the following pairs on the basis of what is mentioned in the brackets:

(i) Transpiration and Guttation (place of occurrence)

(ii) Biodegradable waste and Non-biodegradable waste (One example)

(iii) Population control and Swachh Bharat Abhiyan (One objective)

(iv) Osmosis and Active Transport (Substances undergoing movement)

(v) Metaphase and Anaphase (Position of chromosomes)

Q. 5 (a) The diagram below represents an experiment to demonstrate a certain phenomenon in a green plant:

(i) Will the level of mercury in the glass tubing rise or fall?

Which conducting tissue of the plant does the glass-tubing represent?

(iii) How will the rate of the above process differ if the environment of the plant has:

(iv) State any two advantages of transpiration to the plant.

(v) Draw a neat labelled diagram of a Plasmolysed cell.

(b) Give appropriate biological/ technical terms for the following:

(i) The sensory organ in Cochlea.

(ii) Number of live births per 1000 people per year.

(iii) The point of contact between two neurons.

(iv) The accessory gland in human males whose secretion neutralises the acid in the vagina.

(v) Condition when blood sugar level is lowered in the blood.

(vi) Structure which helps in the adjustment of the size of the pupil.

(vii) A surgical method of fertility control in human males.

(viii) Process by which leucocytes migrate through the walls of capillaries.

(ix) A sudden inheritable change in one or more genes.

(x) A non-dividing phase of the cell cycle where more DNA is synthesised.

Q. 6 (a) State two functions of:

Name of the HormoneEndocrine GlandFunction
(i) (ii)Deposits extra glucose of blood as glycogen
Growth Hormone(iii) (iv)
(v) Thyroid (vi)
(vii) (viii) Prepare body for any emergency
Oxytocin (ix) (x)

Q. 7 (a) A homozygous dominant tall pea plant bearing red flowers (TTRR) is crossed with a homozygous recessive dwarf pea plant bearing white flowers (ttrr).

(i) What is the phenotype and genotype of F1 individuals?

(ii) Write the possible combination of gametes that are obtained when two F1 hybrid plants are crossed.

(iii) Mention the phenotypic ratio of the F2 generation.

(iv) State Mendel’s Law of Independent Assortment.

(v) Name two X-linked disorders found in humans.

(b) The diagram given below is that of a developing human foetus. Answer the questions that follow:

Solving the Reproduction in Organisms Multiple Choice Questions of Class 12 Biology Chapter 1 MCQ can be of extreme help as you will be aware of all the concepts. These MCQ Questions on Reproduction in Organisms Class 12 with answers pave for a quick revision of the Chapter thereby helping you to enhance subject knowledge. Have a glance at the MCQ of Chapter 1 Biology Class 12 and cross-check your answers during preparation.

Select the correct answer

Question 1.
A few statements describing certain features of reproduction are given below:
(i) Gametic fusion takes place
(ii) Transfer of genetic material takes place
(iii) Reduction division takes place
(iv) Progeny have some resemblance with parents
Select the options that are true for both asexual and sexual reproduction from the options given below:
(a) i and iii
(b) ii and iii
(c) ii and iv
(d) i and iii

Question 2.
The term ‘clone’ cannot be applied to offspring formed by sexual reproduction because:
(a) Offspring do not possess exact copies of parental DNA.
(b) DNA of only one parent is copied and passed on to the offspring.
(c) Offspring are formed at different times
(d) DNA of parent and DNA of offspring are completely different.

Answer: (a) Offspring do not possess exact copies of parental DNA.

Question 3.
Amoeba and Yeast reproduce asexually by fission and budding respectively, because they are:
(a) Microscopic organisms
(b) Heterotrophic organisms
(c) Unicellular organisms
(d) Uninucleate organisms.

Answer: (c) Unicellular organisms

Question 4.
A few statements with regard to sexual reproduction are given below:
(i) Sexual reproduction does not always require two individuals.
(ii) Sexual reproduction generally involves gametic fusion.
(iii) Meiosis never occurs during sexual reproduction
(Iv) External fertilisation is a rule during sexual reproduction.
Choose the correct statements from the options below:
(a) i and iv
(b) i and ii
(c) ii and iii
(d) i and iv

Question 5.
A multicellular, filamentous alga exhibits a type of sexual life cycle in which the meiotic division occurs after the formation of zygote. The adult filament of this alga has
(a) Haploid vegetative cells and diploid gametangia
(b) Diploid vegetative cells and diploid gametangia
(c) Diploid vegetative cells and haploid gametangia
(d) Haploid vegetative cells and haploid gametangia.

Answer: (d) Haploid vegetative cells and haploid gametangia.

Question 6.
The male gametes of rice plant have 12 chromosomes in their nucleus. The chromosome number in the female gamete, zygote and the cells of the seedling will be respectively
(a) 12, 24, 12
(b) 24, 12, 12
(c) 12, 24, 24
(d) 24, 12, 24

Question 7.
Given below are a few statements related to external fertilisation. Choose the correct statements.
(i) The male and female gametes are formed and released simultaneously.
(ii) Only a few gametes are released into the medium.
(iii) Water is the medium in a majority of organisms exhibiting external fertilisation.
(iv) Offspring formed as a result of external fertilisation have better chance of survival than those formed inside an organism.
(a) iii and iv
(b) i and iii
(c) ii and iv
(d) i and iv

Question 8.
The statements given below describe certain features that are observed in the pistil of flowers.
(i) Pistil may have many carpels
(ii) Each carpel may have more than one ovule
(iii) Each carpel has only one ovule
(iv) Pistil has only one carprel
Choose the statements that are true from the options below:
(a) i and ii
(b) i and iii
(c) ii and iv
(d) iii and iv

Question 9.
Which of the following situations correctly describe the similarity between an angiosperm egg and a human egg?
(i) Eggs of both are formed only once in a lifetime
(ii) Both the angiosperm egg and human egg are stationary
(iii) Both the angiosperm egg and human egg are motile.
(iv) Syngamy in both results in the formation of zygote
Choose the correct answer from the options given below:
(a) ii and iv
(b) iv only
(c) iii and iv
(d) i and iv

Question 10.
Appearance of vegetative propagules from the nodes of plants such as surgarcane and ginger is mainly because:
(a) Nodes are shorter than internodes
(b) Nodes have meristematic cells
(c) Nodes are located near the soil
(d) Nodes have non-photosynthetic cells

Answer: (b) Nodes have meristematic cells

Question 11.
Which of the following statements supports the view that elaborate sexual reproductive process appeared much later in the organic evolution?
(i) Lower groups of organisms have simpler body design
(ii) Asexual reproduction is common in lower groups
(iii) Asexual reproduction is common in higher groups of organisms
(iv) There is high incidence of sexual reproduction in angiosperms and vertebrates.
Choose the correct answer from the options given below:
(a) i and ii
(b) i and iii
(c) ii and iv
(d) ii and iii

Question 12.
Offspring formed by sexual reproduction exhibit more variations than those formed by asexual reproduction because:
(a) Sexual reproduction is a lengthy process
(b) Gametes of parents have qualitatively different genetic composition
(c) Genetic material comes from parents of two different species
(d) Greater amount of DNA is involved in sexual reproduction.

Answer: (b) Gametes of parents have qualitatively different genetic composition

Question 13.
Choose the correct statement from amongst the following:
(a) Dioecious (hermaphrodite) organisms are seen only in animals
(b) Dioecious organisms are seen only in plants
(c) Dioecious organisms are seen in both plants and animals
(d) Dioecious organisms are seen only in vertebrates.

Answer: (c) Dioecious organisms are seen in both plants and animals

Question 14.
There is no natural death in single celled organisms like Amoeba and bacteria because:
(a) They cannot reproduce sexually
(b) They reproduce by binary fission
(c) Parental body is distributed among the offspring
(d) They are microscopic.

Answer: (c) Parental body is distributed among the offspring

Question 15.
There are various types of reproduction. The type of reproduction adopted by an organism depends on:
(a) The habitat and morphology of the organism
(b) Morphology of the organism
(c) Morphology and physiology of the organisms
(d) The organism’s habitat, physiology and genetic makeup

Answer: (d) The organism’s habitat, physiology and genetic makeup

Question 16.
Identify the incorrect statement.
(a) In asexual reproduction, the offspring produced are morphologically and genetically identical to the parent
(b) Zoospores are sexual reproductive structures
(c) In asexual reproduction, a single parent produces offspring with or without the formation of gametes
(d) Conidia are asexual structures in Penicillium

Answer: (b) Zoospores are sexual reproductive structures

Question 17.
Which of the following is a postfertilisation event in flowering plants?
(a) Transfer of pollen grains
(b) Embryo development
(c) Formation of flower
(d) Formation of pollen grains

Answer: (b) Embryo development

Question 18.
The number of chromosomes in the shoot tip cells of a maize plant is 20. The number of chromosomes in the microspore mother cells of the same plant shall be :
(a) 20
(b) 10
(c) 40
(d) 15

Assertion and Reason Type Questions

These questions consist of two statements each, printed as Assertion and Reason. While answering these questions you are required to choose any one of the following four responses.
(a) If both Assertion and Reason are true and the Reason is a correct explanation of the Assertion.
(b) If both Assertion and Reason are true but Reason is not a correct explanation of the Assertion.
(c) If Assertion is true but the Reason is false.
(d) If both Assertion and Reason are false.
Question 19.
Assertion: Sexual reproduction is
advantageous than asexual reproduction. Reason: Sexual reproduction is rapid mode of reproduction, while asexual reproduction is slow mode of reproduction.

Answer: (c) If Assertion is true but the Reason is false.

Question 20.
Assertion: Individuals produced by asexual reproduction are genetically similar to parents.
Reason: Asexual reproduction involves only mitotic divisions.

Answer: (a) If both Assertion and Reason are true and the Reason is a correct explanation of the Assertion.

Question 21.
Assertion: Stigma of pistil receives the pollen during pollination.
Reason: Pollen grains are produced in ovary of gynoecium.

Answer: (c) If Assertion is true but the Reason is false.

Question 22.
Assertion: In wheat and sugarcane, pollination takes place by water.
Reason: Water is not required for irrigation of wheat and sugarcane.

Answer: (d) If both Assertion and Reason are false.

Question 23.
Assertion: Continued self-pollination generation after generation results in pure line formation.
Reason: By continued self-pollination, plant becomes pure or homozygous for its characters.

Answer: (a) If both Assertion and Reason are true and the Reason is a correct explanation of the Assertion.

Question 24.
Assertion: Many single-celled organisms reproduce by binary fission.
Reason: In binary fission a cell divides into two halves and each rapidly grows into an adult.

Answer: (b) If both Assertion and Reason are true but Reason is not a correct explanation of the Assertion.

Question 25.
Assertion: In viviparous animals, the zygote develops into a young one inside the body of the female organism.
Reason: Because of proper embryonic care and protection, the chances of survival of young ones are greater in viviparous organisms.

Answer: (b) If both Assertion and Reason are true but Reason is not a correct explanation of the Assertion.

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A question about the clarity of certain terms - Biology

[ Table of Contents ] [ PDF Version ]

| Get Your Thoughts Organized | Who is Your Audience? | Prose and Style | Abbreviations and Tense |
First vs. Third Person | Use Active Verbs | References | Plagiarism


A critical aspect of the scientific process is the reporting of new results in scientific journals in order to disseminate that information to the larger community of scientists. Communication of your results contributes to the pool of knowledge within your discipline (and others!) and very often provides information that helps others interpret their own experimental results. Most journals accept papers for publication only after peer review by a small group of scientists who work in the same field and who recommend the paper be published (usually with some revision).

The format and structure presented here is a general one the various scientific journals, and oftentimes specific disciplines, utilize slightly different formats and/or writing styles. Mastery of the format presented here will enable you to adapt easily to most journal- or discipline-specific formats. While this guide (a others like it) is a necessary tool of learning the scientific writing style and format, it is not sufficient, by itself, to make you an accomplished writer. This guide will not teach you how to write in the English language, i.e., it is not a grammar book. You, the writer, must practice writing and thinking within this structure, and , learn by example from the writings of others learning the nuances of this style and format will be enhanced as you read the scientific literature - pay attention to how professional scientists write about their work . You will see improvement in your own scientific writing skills by repeatedly practicing reading, writing, and critiquing of other’s writing.

Top of Page

The guide addresses four major aspects of writing journal-style scientific papers:

(1) fundamental style considerations (2) a suggested strategy for efficiently writing up research results (3) the nuts and bolts of format and content of each section of a paper (part of learning to write a scientific paper is learning how to follow instructions precisely), and, (4) basic information regarding peer critiques of scientific writing. ALL journals have a set of instructions for authors which explicitly state how their paper should be formatted for submission. Consider this guide to be your instructions when writing lab reports for the Biology core courses. We encourage you to follow the directions carefully and to make full use of this guide and the writing support system (TWAs, instructors, and Writing Workshop staff tutors) as you prepare your papers. Please ask for help if you have questions about format, style, or content. Above all, remember to write with precision , clarity , and economy .

Top of Page

Getting Started

The first task to accomplish as you begin the process of writing is to order and organize the information you wish to present. Some people work well from an outline, others do not. Some people write first to discover the points, then rearrange them using an after-the-fact outline. Whatever process you may use, be aware that scientific writing requires special attention to order and organization . Because the paper will be divided into sections, you need to know what information will go into each. If you don't normally work from an outline, this may be an occasion when you'll at least want to develop a list of the major points to be included in each section, before you begin to write. If the paper has multiple authors, then this is a good time to work (and negotiate!) with your collaborators to insure that all the points the group wants to make get listed.

Audience : Who will be reading your paper? Usually you will be writing to your peers. Simple advice: address your paper to another interested biology student, or lab group, in this course or major, and assume they have at least the same knowledge and expertise base as you. Knowing your audience helps you to decide what information to include--you would write a very different article for a narrow, highly technical, disciplinary journal vs. one that went out to a broad range of disciplines. Similarly, you would write a paper for an audience of other biology majors very differently than one you would write for a cross section of the college. Do not write your paper specifically for your instructor.

Top of Page


  • You do not have to try to impress people by using words most people have never heard of. Many published articles are like this, and they are poor papers on account of it.
  • Do not use colloquial speech, slang, or "childish" words or phrases.
  • Do not use contractions: for example , " don't " must be " do not " and "isn't " must be " is not " etc.

Plagiarism (use of others words, ideas, images, etc. without citation) is not to be tolerated and can be easily avoided by adequately referencing any and all information you use from other sources. In the strictest sense, plagiarism is representation of the work of others as being your work. Paraphrasing other's words too closely may be construed as plagiarism in some circumstances. In journal style papers there is virtually no circumstance in which the findings of someone else cannot be expressed in your own words with a proper citation of the source. Refer to: The Bates College Statement On Plagiarism and a Guide to Source Acknowledgment .) If you are unclear about what constitutes plagiarism, please confer with your instructor.

Modified 11-7-11
Department of Biology, Bates College, Lewiston, ME 04240

“Is this relationship exactly like all my past relationships?”

If you notice that you’ve been repeating old relationship patterns with your new partner, “it is most likely an enactment of something else in your earlier life,” Engler says. “In that case, it would be best to explore things that might be going on within you before making a firm decision about the relationship.”

This is especially true if your partner and your relationship seems really “good on paper” — meaning your partner is loving, supportive, committed, etc. — and yet you still can’t shake the feeling that sometimes is wrong.

It may help to get an outside perspective, whether it’s from a friend, your mom, or a therapist. Talk about your doubts while including an honest take on your partner. “You may still end it,” Engler says, but you also might realize you just needed to work on healing old hurts in order to be fully happy.

How to Write a Research Question

What is a research question?
A research question is the question around which you center your research. It should be:

  • clear: it provides enough specifics that one&rsquos audience can easily understand its purpose without needing additional explanation.
  • focused: it is narrow enough that it can be answered thoroughly in the space the writing task allows.
  • concise: it is expressed in the fewest possible words.
  • complex: it is not answerable with a simple &ldquoyes&rdquo or &ldquono,&rdquo but rather requires synthesis and analysis of ideas and sources prior to composition of an answer.
  • arguable: its potential answers are open to debate rather than accepted facts.

You should ask a question about an issue that you are genuinely curious and/or passionate about.

The question you ask should be developed for the discipline you are studying. A question appropriate for Biology, for instance, is different from an appropriate one in Political Science or Sociology. If you are developing your question for a course other than first-year composition, you may want to discuss your ideas for a research question with your professor.

Why is a research question essential to the research process?
Research questions help writers focus their research by providing a path through the research and writing process. The specificity of a well-developed research question helps writers avoid the &ldquoall-about&rdquo paper and work toward supporting a specific, arguable thesis.

Steps to developing a research question:

  1. Choose an interesting general topic. Most professional researchers focus on topics they are genuinely interested in studying. Writers should choose a broad topic about which they genuinely would like to know more. An example of a general topic might be &ldquoSlavery in the American South&rdquo or &ldquoFilms of the 1930s.&rdquo
  2. Do some preliminary research on your general topic. Do a few quick searches in current periodicals and journals on your topic to see what&rsquos already been done and to help you narrow your focus. What issues are scholars and researchers discussing, when it comes to your topic? What questions occur to you as you read these articles?
  3. Consider your audience. For most college papers, your audience will be academic, but always keep your audience in mind when narrowing your topic and developing your question. Would that particular audience be interested in the question you are developing?
  4. Start asking questions. Taking into consideration all of the above, start asking yourself open-ended &ldquohow&rdquo and &ldquowhy&rdquo questions about your general topic. For example, &ldquoWhy were slave narratives effective tools in working toward the abolishment of slavery?&rdquo or &ldquoHow did the films of the 1930s reflect or respond to the conditions of the Great Depression?&rdquo
  5. Evaluate your question. After you&rsquove put a question or even a couple of questions down on paper, evaluate these questions to determine whether they would be effective research questions or whether they need more revising and refining.
    • Is your research question clear? With so much research available on any given topic, research questions must be as clear as possible in order to be effective in helping the writer direct his or her research.
    • Is your research question focused? Research questions must be specific enough to be well covered in the space available.
    • Is your research question complex? Research questions should not be answerable with a simple &ldquoyes&rdquo or &ldquono&rdquo or by easily-found facts. They should, instead, require both research and analysis on the part of the writer. They often begin with &ldquoHow&rdquo or &ldquoWhy.&rdquo
  6. Begin your research. After you&rsquove come up with a question, think about the possible paths your research could take. What sources should you consult as you seek answers to your question? What research process will ensure that you find a variety of perspectives and responses to your question?

Sample Research Questions

Unclear: How should social networking sites address the harm they cause?
Clear: What action should social networking sites like MySpace and Facebook take to protect users&rsquo personal information and privacy?

The unclear version of this question doesn&rsquot specify which social networking sites or suggest what kind of harm the sites might be causing. It also assumes that this &ldquoharm&rdquo is proven and/or accepted. The clearer version specifies sites (MySpace and Facebook), the type of potential harm (privacy issues), and who may be experiencing that harm (users). A strong research question should never leave room for ambiguity or interpretation.

What is the effect on the environment from global warming?
Focused: What is the most significant effect of glacial melting on the lives of penguins in Antarctica?

The unfocused research question is so broad that it couldn&rsquot be adequately answered in a book-length piece, let alone a standard college-level paper. The focused version narrows down to a specific effect of global warming (glacial melting), a specific place (Antarctica), and a specific animal that is affected (penguins). It also requires the writer to take a stance on which effect has the greatest impact on the affected animal. When in doubt, make a research question as narrow and focused as possible.

Too simple: How are doctors addressing diabetes in the U.S.?
Appropriately Complex: What main environmental, behavioral, and genetic factors predict whether Americans will develop diabetes, and how can these commonalities be used to aid the medical community in prevention of the disease?

The simple version of this question can be looked up online and answered in a few factual sentences it leaves no room for analysis. The more complex version is written in two parts it is thought provoking and requires both significant investigation and evaluation from the writer. As a general rule of thumb, if a quick Google search can answer a research question, it&rsquos likely not very effective.

A question about the clarity of certain terms - Biology

Rational Presentation and the Principle of Clarity

The Principle of Clarity

Although reasoning is something that you can do in the relative privacy of your own mind, it is more commonly an act of communication. Usually it is to others that we justify our beliefs and with others that we attempt to understand the world. As such, reasoning is a cooperative undertaking that requires clarity on the part of those who supply it, and charity on the part of those who receive it. So far we have focused on the importance of charity as a guide to the reconstruction and evaluation of rationales. We now turn to the importance of clarity in the actual formulation and presentation of reasoning.

Like the Principle of Charity, the Principle of Clarity can be formulated in the language of the Golden Rule: Reason unto others as you would have them reason unto you. But, again just the Principle of Charity, this formulation works only for those who are comfortable approaching reasoning from a logical point of view. Someone who reasons "You should wear the black dress. The one you're wearing makes you look a lot fatter than you are," is quite a bit clearer than someone who reasons "That's a really pretty dress, but maybe you should wear the black one tonight instead. It shows off your figure even better." But there are times in life when clarity isn't the most important thing.

It is worth noting here that while we will usually speak of clarity as a presentational virtue and charity as an interpretive virtue, both principles really aim at the same thing. To be charitable is to provide the clearest possible interpretation to be clear is to reason in a way that facilitates charitable interpretation. So the Principle of Charity and the Principle of Clarity are just two ways of expressing a more fundamental commitment to rational communication and inquiry.

Exploiting Context 1: Innuendo and Equivocation

Human beings have an extraordinary ability to communicate things that they don't actually say. Of course, other animals are good at this, too, since they communicate without saying anything at all. But we are unique in that we can use language to communicate things that we don't say. This is actually a nice way to understand the purpose of implication. Because we are able to detect logical relationships, we are able to draw conclusions that are logically implied, but not stated. For example:

  • Simone: I busted my hump cleaning the house this morning and when I left here this place was spotless. Someone really did a number on this place, and you, Dirk Bag, are the only one who has been here all day.
  • Dirk: So, what are you trying to say?

Short of explicitly ruling out the possibility that the house messed itself up, Simone has given Dirk all the information he needs to understand that Simone believes Dirk messed up the house. Her statements, properly interpreted, logically imply this. But we rarely need to be this explicit. We can get people to draw conclusions that are neither stated nor logically implied, but merely suggested. For example:

  • Mom: Honey, you were out awfully late last night. I hope you weren't at Vinny's again. You know how your father and I disapprove of him.
  • Rachel: Mom, I swear, I was not at Vinny's. I went to the movies with Bruce.
  • Mom: Bruce? I like Bruce. Why don't we have him for dinner sometime?
  • Rachel: Mom, we're vegetarians, remember?

Rachel has just convinced her mom that she wasn't with Vinny even though she didn't say that or anything that strictly implied that. The truth is that she was with Vinny. She and her friend Lynn went with Vinny and Bruce to the movies, and later on they went back to Lynn's house, where Rachel had precisely the sort of interaction with Vinny that she knows her mom disapproves of.

If Rachel feels any guilt about how she answered her mother's question, she may seek consolation in the fact that she didn't literally lie to her. After all, Mom asked if Rachel was at Vinny's house, not if she was with Vinny. And Rachel did, in a sense, go to the movies with Bruce (after all, he was there), it just so happens that she was with Vinny. Of course, if Rachel is honest with herself she will realize that whether she calls it lying or not, she certainly deceived her mother. She did so by taking advantage of a context in which it was perfectly reasonable to conclude from what Rachel said that she had not been with Vinny at all.

Rachel succeeded in obfuscating her relationship with Vinny in two ways.

First, she took advantage of the context by making claims that were literally true, but which suggested things that were actually false i.e., it is true that she was not at Vinny's house, but in the context, this suggested the false conclusion that she was not with Vinny at all.

Second, she made statements whose truth depended on certain words being interpreted in a way that was not appropriate to the context i.e., Rachel said that she had been "with" Bruce in a context that suggested that she had been with Bruce in particular rather than merely traveling in the same group. (Rachel's vegetarian joke also traded on using the phrase "have for dinner" in a way that was different than her mom intended, though this didn't contribute to the obfuscation.)

These two ways of taking advantage of unstated contextual assumptions can be formalized as follows.

  • Definition: Exploiting contextual assumptions to suggest a conclusion that has been neither stated nor logically implied, and under conditions that suggest that one would be reluctant to claim it explicitly.
  • Identification: Identify the suggested conclusion, showing how, in the given context, it might be reasonably inferred despite the fact that it was neither stated nor implied. Give reasons for doubting that it's author would claim it explicitly.
  • Definition: Using a word or expression in a sense that is alien to the given context without adequate notice or justification.
  • Identification: Identify the word or expression in question and identify the two different senses that have been equivocated upon: (1) the sense that would normally be assumed in the given context and (2) the sense that is being assigned without adequate notice or justification.

Identification : This is a simple example of innuendo. With her question, Melanie suggests the conclusion that they are eating Frieda's dead dog. She suggests this without claiming it explicitly, because it is funnier that way.

Identification: This is a simple example of equivocation. Two words have been equivocated upon: "doing" and "art". Melanie uses the terms to express her enjoyment of artistic activities. Frieda assigned different meanings to suggest that what Melanie was expressing was her satisfying sexual activities with a man named Art.

  • Melanie: Is something wrong? You've really been acting different lately.
  • Frieda: What are you trying to say? I thought being different is what you liked about me.

Identification This example contains both equivocation and innuendo. Frieda equivocates on the term "different." Melanie originally used the term to mean that Frieda's behavior has changed. Frieda's response shows that she has interpreted Melanie's remark as a complaint that Frieda is different from other people. Frieda's hypersensitive response also contains an innuendo because it suggests, without implying or claiming explicitly, that Melanie is criticizing her unfairly, and that perhaps it is really Melanie who has changed. It is not clear that Frieda would claim this explicitly, since her only basis for saying it is her own misinterpretation of an expression of concern for a criticism.

  • Frieda: Did you know that Martha and I are the only ones who are getting an A in logic?
  • Melanie: No, I didn't know that, but it sure doesn't surprise me that you guys are getting exactly the same grade, since you always seem to get exactly the same score on all of your assignments.

Identification: Innuendo. This is a straightforward case of Melanie insinuating, without claiming explicitly, that Melanie is getting an A in logic because she copies Martha's assignments.

  • Frieda: That was Martha. Did you know that Martha truly believes that Derrick is in love with her?
  • Melanie: Wow, Sammy is going to be upset. Aren't Sammy and Derrick like practically engaged?
  • Frieda: Yeah, but Sammy won't be upset. It's no skin off her nose.
  • Melanie: What do you mean. I'd be upset if Lennny was two-timing me.
  • Frieda: What? Derrick isn't two-timing Sammy.
  • Melanie: You just said Derrick is in love with Martha.
  • Frieda: No I didn't! I said Martha believes that.
  • Melanie: You said she believes it and that it's true.
  • Frieda. No, I said she truly believes that.
  • Melanie: Right! So it's true.
  • Frieda: No, she just really, sincerely believes it!
  • Melanie: Well, you should have said that.

Identification: This is obviously an example of equivocation on the phrase "truly believes". Frieda uses the phrase to mean "sincerely believes" but Melanie understands it to mean "has a true belief that". Of course, this is not a very serious example. It's more of a comedy of errors in the vein of Abbot and Costello's Who's on First? Although for us it does serve as another illustration of the difference between asserting that someone believes something and asserting that what they believe is true. And, in fact, the equivocal meaning of the phrase "truly believe" is easily exploited to give specious plausibility to certain sincerely held beliefs for which there is actually very little evidence.

  • It was probably inevitable that Barack Obama's speech on race would be dissected during another race, the race for the U.S. presidency.

Identification: This example may appear to commit equivocation but it does not. Here, the author clearly uses the term 'race' in two different sense. But she does this just to be cute. Nobody who understands English will confuse one usage with the other. It is important to remember that equivocation only occurs when the meanings of the words are being conflated.

  • Helena: Melissa, are you seriously asking me whether any men find you attractive? That guy just held the door open for you when you were still 30 feet away, and then practically wet himself when you winked at him. I know you're blonde, but you're not blind are you?

Identification: This may seem like an innuendo, because it strongly suggests that men find Melissa attractive without saying it. But Helena clearly believes Melissa is attractive, so it does not conform to the definition. The moral here is that we often suggest things that we really would state explicitly, just because suggestion is more fun, or explicit statement is deemed unnecessary. (Note, that you might say that there is an innuendo here that blondes are stupid.)

Exploiting Context 2: Similarity and Difference

Rational inquiry is often initiated by the detection of an unusual similarity or difference. In Example 3, Melanie's question was triggered by her perception that Frieda had been acting different. In Example 4 Frieda's innuendo was prompted by a strange similarity between Martha and Frieda's grades. The meanings of comparative claims are highly context sensitive, and they are easily manipulated by implicitly adopting stronger or weaker standards of comparison than are warranted by the context.

Reasoning that depends on reasons that make explicit claims about similarity and difference is called analogical reasoning. Two analogical arguments can be distilled from the following example.

  • Rachel : Dad, why does Jessie get to go out tonight? He didn't finish his homework this week either.
  • Dad : I know that, but Jessie happens to be getting straight A's and he didn't finish his homework because he was helping me fix the car. You just spent too much time on the phone. And Jessie and Mike aren't just going out tonight, they're going to help with the homecoming float.
  • Rachel: But I want to help with the float, too!
  • Dad: Well, that's interesting. That's not what you wanted to do before I grounded you. Your mother tells me you were going to the movies with Vile Vinny.
  • Rachel: It wasn't Vinny and he's not vile! See, you're not grounding me because I didn't do my homework, you're grounding me because you thought I was going out with Vinny!

Rachel is grounded for doing the same thing that Jessie did.

Jessie should be grounded tonight.

P1. If x is being treated in manner y because of z, and z does not apply to u, then u should not be treated like x.
Argument Dad
Jessie should not be grounded tonight.

The things for which Rachel is being grounded do not apply to Jessie.

The respective principles in the above rationales are typical variations on the following two analogical principles.

  • Principle of Similarity: If x and y are the same, then x and y should be (or are) treated the same.
  • Principle of Difference: If x and y are different, then x and y should be (or are) treated differently.

These principles sound sensible, and when the terms "same" and "different" are interpreted very strongly (e.g., if "same" means "identical" or "sharing every single property to the same degree" and "different" means "absolutely distinct" or "having absolutely no properties in common.") they have some obviously sound application.

For example, if you have the job of grading apples for quality and you see two apples that seem to be identical in every respect they should get the same grade. On the other hand, if you are just looking for an apple to eat and you are given these two apples to choose from, so that there is no legitimate to prefer one to the other, you still aren't going to treat them totally the same, since you are going to eat only one of them.

Similarly, if your job is to separate apples from oranges, then if you see an apple and an orange you will treat them differently by putting the apple in the apple box and the orange orange box. But, if you are hungry for an apple and an orange, then you might eat them both, thereby violating the principle of difference which instruct you to treat them differently.

In ordinary contexts the situation gets quite a bit murkier because "same" and "different" are usually used to mean "having some of the same properties" or "having some different properties." And the problem here is that just about any two objects in the world have some similar properties and some of the same properties. Your brain and a marshmallow are similar in that they both contain a lot of carbon and they will both fit in inside a large jack-o-lantern. On the other hand, they are different in that marshmallows can't solve logic problems and your brain has more calories.

All this means that analogical reasoning is often very unreliable no matter how careful you are, but to give it the best chance of being useful we need to be sure that claims about similarity and difference are appropriate to the context of comparison. In the example above, it's easy to see that Rachel and Dad differ, not so much about the actual similarities and differences, but about which similarities and differences are strongest and most relevant in the given context to the conclusion being drawn. Rachel claims that the similarity between Jessie and Rachel is strongest and most relevant, and that is why Jessie and Rachel should be treated the same. Dad claims that the differences between Jessie and Rachel are strongest and most relevant in this context, and that is why they should be treated differently.

This, of course, just raises the further question how one establishes strength and relevance in a context. Here the matter is pretty easily resolved. The differences between Jessie and Rachel are relevant to differential grounding because grounding in this context is ultimately for the purpose of behavior modification, and Rachel's behavior is clearly in greater need of modification than Jessie's. The differences are stronger, because So Dad appears to be right this time. But things might have been different. If, for example, there had been an explicit household rule that "If child x doesn't do x's homework, then x is grounded for the following weekend," then Rachel's similarity really should have carried the day. Even though the rule is still ultimately about behavior modification, another issue would have had even greater relevance, and that is logical consistency and respect for the rule of law. (Relevance and Logical Consistency will be treated in greater detail below.) This discussion lead us to codify the following two errors.

  • Basing a conclusion on an alleged similarity between two or more things when it is not clear that the similarity in question is (a) sufficiently strong or (b) sufficiently relevant to the context to provide adequate support for conclusion.

Identification: Explicitly identify the similarity in question and identify why you think it is insufficiently strong or insufficiently relevant to the context to warrant the conclusion.

  • Basing a conclusion on an alleged distinction between two or more things when it is not clear that the distinction in question is (a) sufficiently strong or (b) sufficiently relevant to the context to provide adequate support the conclusion.

Identification: Explicitly identify the distinction in question and identify why you think it is insufficiently strong or insufficiently relevant to the context to adequately support the conclusion.

These errors are obviously very similar in some ways, but their differences are very strong and very relevant to this context!

  • Fletch: I don't care who wins the election. All politicians are the same. They're all liars and crooks.

Identification: This is a weak comparison. The similarity is relevant to the context, but not particularly strong. Even if it were true that all politicians are the same in the sense of being liars and crooks, some liars and crooks may be better or worse politicians than other liars and crooks. For example, both Richard Nixon and Bill Clinton apparently lied to congress and broke the law. But they were not equally good or bad presidents because of this.

  • Amanda: Ashley, I don't know how you can keep talking on the cell phone while you're driving when you know how dangerous it is. It kills more people than drunk driving. You're basically a murder waiting to happen.
  • Ash: I know, but it really isn't that dangerous. The reason it kills that many more people is because there's a lot more cell phone users than drunk drivers. Every one who drives rather than walks is a murder waiting to happen if you want to think that way. Besides, I use a hands free cell phone.
  • Amanda: You still shouldn't do it. That study we read said that there's no difference between hand-held sets and hand free sets.
  • Ash: Well, that can't be right. It's just common sense that a hands free is safer. After all, you've got both hands on the wheel. I know that I am very much in control.
  • Amanda: Ashley, watch ou.

It's worth noting that Ashley's first point is actually quite legitimate. It's not nearly as dangerous for a single individual to talk on the cell phone while driving as it is to be intoxicated while driving, and that seems to be the relevant context for individual decision making. But Ashley does makes a questionable distinction between the two kinds of cell phones. She is rejecting the data that show that there is no measurable difference between the two types of cell phone as it relates to traffic accidents simply because she feels it's wrong. So, the proper identification here would be:

Identification: This is a weak distinction. Ashley makes a distinction between hands free cell phones and hand held cell phones with respect to safety. This is a relevant difference, but it is weak since there is evidence against it, and the evidence she gives in support of her view is just her own subjective feeling of safety.

  • Spud: Jeez, we sure ain't in Kansas anymore. I never seen so many colored people in all my life!
  • Francis: You keep talkin' like that and you're going to get our butts kicked all the way back to Kansas. They aren't colored people Spud, they're people of color.
  • Spud: Colored people, people of color, what the hell is the difference?
  • Francis: Right, that's what you said before we moved out here. Your very words: "California, Kansas what the hell is the difference?" and here you are today pointing out differences every time we go out the house.
  • Spud: I still don't see the difference between colored people and people of color.
  • Francis: Well, if you can't tell the difference between getting your ass kicked and not, then God help you.

I n this example, Francis has given Spud some good advice, but he has presented it in a confusing way. He speaks as if the term "colored people" refers to a certain group, and "people of color" refers to a different group. Of course, both terms refer to the same group, namely, non Caucasians. However, one term is offensive to people and the other term is not. This is what logicians sometimes call a distinction without a difference, a purely verbal distinction that doesn't correspond to any difference in reality. Francis has also made a questionable comparison, as indicated below.

Identification 1: Weak distinction. Francis distinguishes between colored people and people of color as if this corresponds to a difference in the world, when in fact they are simply two different ways (one offensive, the other not) of referring to exactly the same group.

Identification 2: Weak comparison. Francis claims that Spud has made two similar mistakes. The first mistake is in believing that there is no difference between Kansas and California. The second mistake is in believing there is no difference between "colored people" and "people of color." But in the context, these mistakes are not relevantly similar. Spud's first mistake reflected ignorance about the world. Spud's second mistake reflected ignorance about linguistic propriety.

  • Gay: Hi Klaus, I'm Gay.
  • Klaus: Really? That's cool. You know, I used to really think that being gay was totally perverted and wrong. You know, especially just the thought of guys going at each other like that, it really made me want to puke. But I'm majoring in biology now, and I'm getting like this whole different perspective. I've been reading how common homosexual behavior is in all sorts of other species. So I'm really starting to see that homosexuality is just a totally natural phenomenon, and that we shouldn't be so judgmental about it.

Identification: Weak Comparison. Klaus compares homosexuality in humans to homosexuality in other animals, arguing that since homosexuality isn't wrong in animals, it isn't wrong in people either. This relies on the assumption that human homosexual behavior is like the homosexual behavior of other species, as the rational below demonstrates:

Human HS behavior is like the HS behavior in other species, and the HS behavior in other species is not morally wrong.

The two behaviors, while physically similar, are not similar in a way that is relevant to drawing moral conclusions. This is because the behavior of non human animals is not subject to moral evaluation.

  • Fayanne: You know, I just voted and it really made me want to cry. There were these people in line who obviously had no idea what they were doing. The whole time I'm thinking, my vote counts the same as these idiots?
  • Gabriela: Oh God, totally. I don't even get why people like that should have the right to vote. I think there should be some kind of test you have to pass, like our driving test. Bad voters do just as much harm as bad drivers, right? Why shouldn't they have to get a license to vote, too?

Identification: Weak Comparison. Gabriela argues that people should not have the right to vote, rather that they should first have to demonstrate competency by passing a test. Her reason for this is that ignorant voting is like bad driving with respect to the degree of harm that can be done, and a test is required of all prospective drivers. This is a rather weak comparison because (a) a bad driver can do much more harm than a bad voter and (b) the effectiveness and fairness of a driver competency test is more easily established than the effectiveness and fairness of a voter competency test.

After you examine a bunch of comparisons and distinctions critically it's easy to start assuming that most comparisons and criticisms are weak, which of course is not correct. The next two examples provide an antidote to this tendency.

  • Seymour: Don't you think it's funny the way people are all down on kids playing computers and video games because we should be outside playing, but then when they hear about some kid who has his nose in a book all the time and they're all "Oh, that's so wonderful. I wish my Seymour would read more." Seymour, read more? Pretty good, huh?
  • Dagwood: Yeah, wipe off the joystick. You got Cheetos gunk on it again.

Identification: This is actually a strong comparison. Seymour argues that reading and playing computer and video games are similar insofar as they are both sedentary activities. It's possible that reading has other benefits that video games doesn't, but that's not relevant to his rather limited point.

  • Lars: Olaf, you know what you said about Gustav saying he was going after my girl Gretchen? I went to kick his ass, and he said he doesn't even know Gretchen.
  • Olaf: So, what, he's calling me a liar?
  • Lars: He said it wasn't true. He said he has his eye on Hilda.
  • Olaf: He's calling me a liar. Damn, now, I have to go kick his ass.
  • Lars: OK.

Identification: This is not a weak distinction. There is a very important difference between lying and saying something that isn't true, which is highly relevant to the context. Lying consists in willful deceit, but one can say something false by accident.

One common form of confusion is confusion about the issue at hand. In order to discuss this problem clearly we introduce the following definition:

  • Definition: An issue is the problem being addressed by a particular rationale. Arguments and explanation address different problems, hence the issues are formulated differently.
    • In an argument, the issue with respect to some conclusion C is best expressed as 'whether or not C."
      • Example: "The issue the argument is addressing is whether or not the President lied."
      • Example: The issue the explanation is addressing is why the President lied.

      Issue confusion is often the result of the failure to grasp the nature of the rationale being proposed. For example:

      • Fitz: You know, you could have avoided that accident if you'd been more careful. I notice you usually just take off when the light turns green. I always look both ways to make sure no one is coming.
      • Marcy: Fitz, just go to hell, ok? Is that the kind of thing that friends say to each other? Here I am with whiplash, three cracked ribs and no car and all you can think to say is that it was all my fault. I had a green light! That guy just came out of nowhere.

      This example might be analyzed as a straw man, i.e., we might say that Marcy misrepresents what Fitz is saying in a weakened form. But another way to analyze this is to say that Marcy is actually confused about the issue Fitz is addressing. Fitz is addressing the issue whether or not Marcy could have avoided the accident. Marcy is addressing the issue whether or not the accident was legally her fault. These issues are distinct, though of course they are on the same general subject, namely Marcy's automobile accident. Marcy's response is a pretty good example of what's known as a Red Herring which we define as follows:

      • Definition: Distracting attention from an issue by confusing it with a different issue that is irrelevant or only superficially related to the one at hand.
      • Identification: Identify the issue at hand and identify the irrelevant issue being introduced. Show why the new issue is irrelevant and why introducing the irrelevant issue has the effect of confusing the two issues, rather than simply explicitly refocusing attention on the new issue.

      Red Herrings are fairly common, but it is also a very easy criticism to abuse. The reason for this is that its easy to make what someone is saying appear to be irrelevant by just arbitrarily defining the issue very narrowly. Here's is an example of a totally bogus Red Herring criticism:

      • Mo: I really don't think it's a good idea for the kids to be visiting Aunt Margaret when they're still getting over the flu. She's very old and frail, and the flu can be fatal for someone like that.
      • Fran: Well, if that's how you feel about it then I don't think we should take this trip at all. I mean the whole point of going back home was for the kids to see Aunt Margaret.

      Identification: You could characterize Fran's response as a Red Herring as follows: Mo's original issue is whether or not the kids should go to Aunt Margaret's. "Fran distracts attention from this issue by confusing it with the issue whether or not they should go on a trip at all. This has nothing to do with Mo's issue, since they could simply go on the trip without visiting Aunt Margaret." The problem with this criticism is that Fran has not introduced an irrelevant issue at all. It's easy to make it sound that way, but if it is really true that the whole point of taking the trip was to see Aunt Margaret, then the two issues are intimately related. Whether or not they should go on the trip depends on whether or not the kids will be able to see Aunt Margaret.

      The Red Herring criticism is only legitimate when an issue has been clearly defined. For example, if you are attempting to carry out a particular well-defined task, and you begin to make considerations that really have nothing to do with that task, then you are in Red Herring territory. For example:

      • Bean: OK, we're going to go for Sorensen as our first round draft pick. We're agreed that we need the best defensive catcher out there and this guy has the best defensive numbers in all of Division 1 college, except for Lovitt who doesn't have as much experience and who we know is not going to sign this year anyway.
      • Brown: It's your call, but I can't really say I agree with you. I've seen this guy in person, and he just does not look like a ball player to me.

      Identification: Red Herring. The issue is whether or not Sorensen is the best defensive catcher. Brown introduces an irrelevant issue, which is whether Sorensen looks like a ball player. This is a confusion, since Brown seems to think of this as a reason for doubting that Sorensen is a good defensive catcher.

      There is a very strong connection between the idea of Red Herring and Weak Principle. In fact, Red Herring is really just a version of the Weak Principle criticism. When we say that what someone has said is irrelevant, what we are really saying is that if we make a charitable attempt to formulate a rationale out of what the person said, they end up being committed to a principle that is so weak that no informed, reasonable person would endorse it. For example, if we took Brown's reasoning above seriously, then we would have to stick him with a rationale like this:

      Sorensen has the best defensive statistics but he does not look like a ballplayer.

      Sorensen is not the best defensive catcher in the draft.

      This principle is intelligible, but in the end, it does not seem particularly charitable to attribute it to Brown. So we conclude that what he is saying is not really relevant to the issue whether or not Sorensen is the best defensive catcher, but rather some other issue, like whether or not Sorensen's defensive numbers predict that he will perform well at a higher level.

      • Juror 1: Well, this was a pretty straightforward trial. Three witnesses identified the defendant as the shooter her prints were on the gun that fired the bullet, and they found the cash from the store in her mother's apartment. I'd say this is open and shut.
      • Juror 7: I don't agree. If we convict, this will be her third strike, and they're going to put this poor gal away for life. She's got three kids. I'm not going to be any part of separating them from their momma for life.

      Identification: Red Herring: The issue here is whether the defendant committed the crime. Juror 7 raises a different issue, which is what will happen to the defendant and her kids if found guilty. Juror 7 seems to be confusing the two issues, because 7 seems to think that the existence of the three strikes law bears on the question whether the defendant is guilty of committing the crime.

      Although this is the sort of example that is typically regarded as a classic Red Herring, the truth is that the Red Herring analysis may simply be uncharitable. We might simply think of juror 7 as acknowledging the defendant's guilt, but as arguing that she should still not be convicted because the three strikes law is wrong.

      • Teller: I'll go out for coffee with you but only on the condition that we go somewhere besides the Common Ground again. That place is so expensive, I just can't afford it. Besides, I don't like their coffee and I don't like their snooty politically correct attitude, either.
      • Winnie: How can you say that? Their coffee is expensive because they only buy beans from producers that agree not to use illegal pesticides or hire child labor. That really means a lot to me.

      Identification: Red Herring. Teller's issue is why Teller does not like going to the Common Ground for coffee. Winnie distracts attention from this issue by confusing it with the question why Winnie does like going to the Common Ground for coffee. The two issues are confused because Winnie appears to be interpreting Teller's own preferences as if they are offered as a criticism of hers. But this isn't how he represents them.

      Vincenzo: I don't care how many children's books Tookie Williams has written, or how much he's spoken against gangs, the fact is that he killed four people in cold blood. Justice requires that when a person is convicted of a crime, that they serve their sentence

      Resendes: I don't understand how you could possibly say that! His books have brought smiles to the faces of every little child in America. Do you actually want someone to kill Tookie, and make little Johnny cry?

      Q: The owner of Time Traders requested you to calculate the net profit for the year ended30 June 2020. .

      A: Formula: Net Profit = Ending owners capital + Drawings - Beginning owners capital Deduction of Begin.

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      Q: Bernard Creighton is the controller for Creighton Hardware Store. In puttingtogether the cash budget.

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      Q: An item of inventory was purchased for $10. However, due to a fall in demand, its selling price will.

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      Q: Jen, Raks, and Fred are partners with average capital balances during 2019 of P945,000, P477,300, an.

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      Q: Martinez Co. borrowed $58,220 on March 1 of the current year by signing a 60-day, 11%, interest-bear.

      A: Notes payable is a negotiable instrument signed by the promisor who agreed to pay a certain amount a.

      Q: Alps Ltd has a net income after tax of $1 500 000 for the year ended 30 June 2019. At the beginning .

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      A: The net present value method is used to evaluate the investment projects. We can evaluate the projec.

      Q: On March 2020, George Construction Company entered into a fixed price contract to construct a commer.

      A: The contract costs refer to the cost incurred on the contract by the owner of the property.

      Biology Questions and Answers Form 1 - Biology Form One Notes

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      KCSE Revision Questions and Answers

      Biology Notes Form 1 - Biology Form 1 Notes - Form 1 Biology Notes

      Introduction to Biology

      Biology is a branch of science that deals with the study of living things. There are diverse forms of life on earth ranging from the invisible microscopic living things to the gigantic life forms. It aims at explaining the living world in terms of scientific principles.

      It is important to note, however, that living things interact with the non living things in the environment as Well. Biology, therefore also entails the study of non living things as well.

      The role of human beings in shaping the environment is also investigated in biology.

      In summary, biology deals with the study of origins, types, nature, growth, development, interactions and maintenance of all life forms on earth.

      Biology is such a broad field of knowledge. It is divided into two broad branches

      1. Zoology- This is a branch of biology that deals with the study of animal life.

      2. Botany- This is a branch of biology that deals with the study of plant life.

      Within the two branches, there exist even smaller branches because the branches (botany and Zoology) are very wide and complex.

      The smaller branches of biology include:

      a) Ecology- This is the study of the interrelationships between organisms and their environment. Ecology aims at establishing how organisms are related to each other and their environment.

      Ecology is further subdivided into smaller branches. These can be forest ecology, marine ecology, rangeland ecology etc.

      b) Genetics- This sub-branch of biology deals with the study of inheritance and variation. It deals with the study of how variations (differences) occur between parents and their offspring. It is also concerned with how various characteristics are passed on from parents to offspring.

      c) Entomology- This is the study of insects.

      d) Parasitology- This is the study of parasites.

      e) Physiology- This deals with the study of the functions of various structures of an organism. It deals with the processes that take place in the body of organisms.

      f) Anatomy- The study of the internal structure of organisms

      g) Microbiology- This is the study of microorganisms

      h) Bacteriology- The study of bacteria

      i) Ornithology- This is the study of birds

      j) Itchthology-This is the study of fishes

      This list is in-exhaustive as there are very many other branches of biology.

      Importance of biology

      > Joint development of HIV/AIDS vaccine by Kenyan and British scientists.

      > The coordinated fight against Severe Acute Respiratory Syndrome involving scientist all over the world.

      > The fight to save the ozone layer from depletion through various international agreements such as the Kyoto protocol.

      > Management of resources through international treaties such as the CITES (Convention against International Trade on Endangered Species).

      Characteristics Of Living Things

      Living things share a lot of characteristics in common. These characteristics are discussed below.

      Nutrition is the process by which living things obtain and assimilate (utilize) nutrients. Living things require nutrients for various purposes growth, repair of worn out tissues and for provision of energy. Plants manufacture their own food using light energy, carbon (IV) oxide, water and mineral salts through the process of photosynthesis. Conversely, animals feed on already manufactured foods from plants and other animals.

      Respiration is the process by which food substances are chemically broken down to release energy. During respiration, oxygen is used while energy, carbon (IV) oxide and water are released. Respiration occurs in all living cells.

      The energy produced in living things is very useful as it enables the living things carry out some of their physiological processes.

      The energy is also required for growth and development, movement and repair of worn out tissues.

      Gaseous exchange refers to the process by which living things exchange oxygen and carbon (IV) oxide across the respiratory surfaces. Animals always take in air rich in oxygen and give out air rich in carbon (IV) oxide.

      Carbon (IV) oxide is a waste product of chemical reactions in the body. Animals require oxygen for respiration. Gaseous exchange, therefore, enables animals obtain oxygen for respiration and get rid of carbon (IV) oxide, a waste product.

      Plants, however, require carbon (IV) oxide for photosynthesis during the day. They give away oxygen as a by-product. The plants equally require oxygen for respiration and give away carbon (IV) oxide.

      This is the process by which living things separate and eliminate the waste or harmful materials resulting from chemical reactions Within the cells. These harmful waste products of metabolism maybe toxic to the body if they are left to accumulate in the cells of the living things

      e) Growth and Development

      Growth refers to an irreversible increase in size and mass while development refers to the irreversible change in complexity of the structure of living things. Growth and development of living things is essential as it enables the living things to attain maximum size that can enable them to perform their functions and roles.

      This is the process by which living things give rise to new individuals of the same kind. All living things reproduce. Reproduction is essential as it leads to perpetuation of species and it avoids extinction of certain animals and plants.

      This is the ability of living things to perceive (detect) changes in their environment and respond to them appropriately. Living things respond to changes in temperature, humidity, light, presence or absence of certain chemicals.

      Response of organisms to these changes is crucial as it enables them to escape from harmful stimuli. Ability to detect changes in the environment also enables organisms to obtain resources in their environment.

      Movement refers to change is position (displacement) of a part or parts of an organism. Movement in plants includes folding of leaves, closing of flowers and growing of shoots towards light. The change of position of an entire organism from one position to another is locomotion.

      a) Motor vehicles move, use energy and produce carbon dioxide and water. Similar characteristics occur in living organisms yet motor vehicles are not classified as living. List the other characteristics of living things that do NOT occur in motor vehicles.

      b) Give the name to the study of:

      Collection of Specimen

      We have defined biology as the study of living things. For effective study, a biologist may have to collect some living things or some parts of living things for observation and analysis. The living things or parts of living things that are used for biological study are called specimens.

      Biological studies always take place in laboratories. A laboratory is a building or a room that is designed and equipped for scientific studies.

      Collections of living things especially animals may not be very easy. Some of the animals are not easy to catch while some are quite dangerous. Knowledge on proper specimen collection and handling of is very important. We will discuss some of the apparatus used in specimen collection.

      a) Sweep net- This is used for catching flying insects.

      b) Fish net- This is used for trapping small fish and other small Water animals.

      c) Pooter- This is used for sucking small animals from rock surfaces or barks of trees.

      d) Bait trap- This is used for attracting and trapping small animals including rats.

      e) Pit fall trap- This is used for catching crawling animals.

      f) Pair of forceps- This is an apparatus used for picking up small crawling animals e.g. stinging insects.

      g) Specimen bottles- These are bottles used for keeping collected specimen. They are of different sizes depending on the size of the specimen being studied.

      h) Magnifying lens- This is used to enlarge small objects. A hand lens is a common magnifying lens used in the laboratory. The magnifying power of the hand lenses is always indicated on the lens e. g. X10, X5, X8. The magnifying power of a lens shows how many times the image will be enlarged compared to the object.

      How to use a magnifying lens

      To use a magnifying lens, place the object to be enlarged on the bench. Hold the magnifying lens on one hand and while closing one eye, move the lens towards the object until the image comes into clear focus.

      If a magnifying lens is used to make a drawing of a specimen, the magnification of the drawing will have no relation with the size of the drawing.

      The magnification of the drawing can be calculated using the formula shown below.

      Drawing magnification: Length of drawing divided by Length of the actual object

      The sign of “times” must come before the magnification value e. g. X10, X5, X15 etc.

      Precautions During Collection and Observation of Specimen

      While collecting specimen for observation, a biologist should play close attention to the following:

      Comparison Between Plants and Animals

      Chapter Two: Classification 1

      In particular, animals and plants are all living things yet they differ in many aspects. Amongst animals and plants also there exist a lot of differences.

      There are millions of different plant and animal types exhibiting a range of differences. This created a need for a classification system of living things to make study of the living organisms easier.

      External features of plants used in classification

      External features of animals used in classification

      Importance of Classification

      Historical background of Classification

      b) Flowering or non-flowering

      Taxonomic Units of Classification

      2. Phylum (animals)/division (plants)

      All living organisms are classified into five major kingdoms:

      a) Kingdom Monera- This is composed of microscopic unicellular organisms mainly bacteria e.g amoeba.

      b) Kingdom Protoctista- This kingdom is comprised of members who are microscopic. Though, some are large enough to be seen with the naked eyes.

      Members of this kingdom include algae and protozoa.

      c) Kingdom Fungi- Members of this kingdom comprises the mushrooms, toadstools, moulds and yeast.

      d) Kingdom Plantae- This kingdom comprises the moss plant, ferns, maize plants, hibiscus, meru oak tree etc.

      e) Kingdom Animalia — Members of this kingdom include the tapeworms, hydra, fishes, human beings, lizards, earthworms etc.

      In hierarchy of classification, a kingdom is further divided into several phyla (plural of phylum) or divisions (in plants). Within the phyla or divisions, organisms are further sorted out into groups known as classes based on their similarities and mode of life.

      Each class is further subdivided into small groups called orders based on structural similarities. Orders subdivide into families which subdivide into genera (plural for genus).

      Genera are then subdivided into smaller units of classification called the species.

      Species is the smallest unit of classification whose members share many similarities and can freely interbreed to give rise to fertile or viable offspring.

      Members of a particular species can, however, exhibit various differences e. g. differences in skin colour or body forms. Within the species, organisms can further be classified based on the differences in colour or forms.

      In humans, this gives the races, in animals the term used is breed while in plants, variety is preferred. In bacteria, the term strain is used to describe the variant forms.

      Members of different but very closely related species can breed but the resulting offspring will be sterile (infertile). In particular, a mule is a sterile offspring between a horse and a donkey.

      Moving from kingdom to species, it is important to note that the number of organisms in each taxon decreases. The similarities, however, increase as one moves from kingdom to species.

      Scientific Naming of Living Organisms

      Rules of Binomial Nomenclature

      Binomial nomenclature requires that:

      a) The first part of the scientific name is that of the genus name which should begin with a capital letter. The second name is that of species. The species name should be written in small letters e. g.

      c) Leopard- Panthera pardus

      d) Domestic dog- Canisfamiliaris

      e) Human being- Homo sapiens

      b) When printed in books and other printed works, the scientific names should be printed in italics. However, in handwritten manuscripts and typed works, the genus and species names should be lined separately.

      Printed work- Homo sapiens

      c) The specific name is frequently written with the name of the scientist who first adequately described and named the organism e. g. Balanus balanoides Linneaus. d) Scientists must give a latinised name for a newly described animal or plant species where a Latin name is missing e,g.

      Aloe kilzfiensis- A type of aloe found in kilifi

      Meladogyne kikuyuensis- A nematode found in kikuyu.

      Origin of scientific names

      Scientific names assigned to organisms can be:

      Chapter Three: The Cell

      Magnification=Eyepiece magnification X Objective lens magnification

      Figure 1. The light microscope

      Handling and Care of the Microscope

      Part of the microscope: Limb

      function: supports the body tube and stage

      function: provides firm and steady support to the microscope

      function: holds the eyepiece and the revolving nose piece

      Coarse adjustment knob:

      function: raises or lowers the body tube through longer distances to bring the image into sharper focus

      function: raises or lowers the body tube through smaller distances to bring the image into sharper focus. it is mostly used with the high power objective lens

      function: an aperture that regulates the amount of light passing through the condenser to illuminate the specimen

      function: contains a lens which contributes to the magnification of the specimen under review

      function: bring image into focus and magnifies it.

      function: reflects light through the condenser to the object on the stage

      function: holds the objective lenses in place and enables the change from one objective lens to the other

      function: concentrates light on the object on stage

      function: flat platform where specimen on the slide is has two clips to hold the slide into position

      The following rules should be observed when handling the microscope:

      > Always use both hands when carrying the microscope. One hand should hold the base to provide support while the other hand holds the limb.

      > Never place the microscope too close to the edge of the working bench or table.

      > Do not touch the mirror or the lenses with your fingers.

      > Dirty lenses should be cleaned using a special soft lens tissue paper or tissue paper moistened with ethanol. The other parts of the microscope may be cleaned using a microscope.

      > Do not wet any part of the microscope.

      > Make sure the low power objective lens clicks into position in line with the eye piece before and after use.

      > After use, always clean and store the microscope in a safe place, free from moisture and dust.

      How to use the Microscope

      Cell Structures as seen under the Light Microscope

      Figure 2 Plant and animal cells as seen under the light microscope

      The cell as seen under the Electron Microscope

      Structure and Functions of the Cell Organelles

      > Mitochondria are self replicative that is they can divide to form new ones.

      Figure 5. The Mitochondrion (Animal)

      Figure 6, (generalize(lmage23 mitochondrion Structure)

      d) Endoplasmic Reticulum

      g)Golgi bodies/Golgi apparatus

      1) They package and transport glycoproteins.

      2) They are involved in secretion of synthesized proteins and carbohydrates.

      3) They manufacture lysosomes.

      Note: Golgi bodies are abundant in cells that are active in secretion. For instance pancreatic cells which secrete enzymes and the nerve cells which secrete neurotransmitter substances.

      1. It gives plant cells their definite shape

      2. It provides mechanical support and protection against mechanical injury.

      3. The cell wall allows gases, water and other substances to pass through it.

      Comparison between Plant Cells and Animal Cells

      While there exist many similarities between plant and animal cells, there are a number of differences.

      Estimation of Cell Size

      The light microscope can be used to estimate the size of a cell. Most cells have diameters smaller than a millimeter. Due to this, cell sizes are always measures in smaller units.

      These are micrometres and nanometers. These units of measurements are related as shown below.

      1 millimeter (mm) = 1000 micrometres (pm).

      1 micrometer (pm) = 1000 nanometres (nm).

      Procedure in cell size estimation

      cell diameter = diameter of the field of view in micrometers divided by number of cells.

      Cell Specialization. Tissues. Organs and Organ Systems

      Cell Specialization/Cell Differentiation

      a) Tissue types in animals

      1. Epithelial tissue- This is a thin continuous layer of cells for lining and protection of internal and external surfaces.

      2. Skeletal muscle- This is a bundle or sheets of elongated cells with fibres that can contract. Its contraction and relaxation brings about movement.

      4. Blood tissue- This is a fluid containing red blood cells, white blood cells and platelets.

      The main functions of blood tissue are transportation of nutrients and gases as well as protection of the body against infections.

      5. Connective tissue- This tissue consists of strong fibres that connects other tissues and organs thereby holding them in position.

      b)Tissue types in plants

      1. Epidermal tissue- This is a single thin layer of cells covering the outer surfaces. It protects inner tissues of plants from mechanical damage and infection.

      2. Palisade tissue- This is a group of cells rich in chloroplasts containing chlorophyll. It has a site for the absorption of light energy and manufacture of food by photosynthesis.

      3. Parenchyma tissue- This tissue consists of special thin walled irregularly shaped cells. They form packaging and storage cells.

      4.Conducting tissue/Vascular bundle- This tissue consists of xylem and phloem. Xylem conducts water and dissolved mineral salts in a plant while phloem conducts food substances in solution.

      a) Heart- composed of connective, muscle, epithelial and blood tissues.

      b) Kidney- Composed of connective, epithelial and muscle tissues

      c) Brain- Composed of epithelial, connective tissues

      d) Lungs- Composed of epithelial, connective tissues.

      a) Roots- composed of epidermal, conducting and parenchyma tissues.

      b) Flowers- This is composed of epidermal, conducting tissues.

      c) Stem- Composed of conducting, parenchyma, and epidermal tissues and palisade tissues in some cases

      d) Leaves- Composed of palisade, conducting and epidermal tissues.

      This is a group of organs Whose functions are coordinated and synchronized to perform the same function.

      Organ systems are more pronounced in animals than in plants

      Organ systems in animals include

      a) Digestive system composed of organs such as oesophagus, stomach, intestines and their associated glands.

      b) Circulatory system composed of the heart, blood vessels (arteries, veins, capillaries). c) Excretory this is composed of kidney, liver, and blood vessels.

      d) Respiratory system composed of trachea, bronchus, and lungs.

      e) Reproductive system composed of the reproductive organs and associated glands.

      f) Nervous systems composed of the brain, spinal cord, eye, ear organs.

      Chapter Four: Cell Physiology

      a) Chloroplasts play a vital role in carbohydrate synthesis.

      b) Mitochondrion produces energy required to carry out life processes.

      c) Ribosomes manufacture of proteins.

      Structure of the membrane

      Properties of the cell membrane

      a) The cell membrane is semi permeable- The pores that occur on the cell membrane allows the passage of the small size molecules but does not allow the passage of the large sized molecules.

      Such a membrane is said to be selectively permeable or semi-permeable. In particular, when a cell is surrounded by a dilute sugar solution, the small sized water molecules will enter the cell but the larger sugar molecules will not pass through the cell membrane.

      In contrast, the cell wall is permeable as it allows both sugar and water molecules to pass through it it has larger pores. This property of selectively permeability enables the cell membrane to select what enters and leaves the cell.

      b)The cell membrane is sensitive to changes in temperature and pH- Cell membranes are made up of protein. Proteins are adversely affected by extreme changes in temperature and pH.

      Changes in temperature and pH will alter the structure of the cell membrane thereby hindering the normal functioning of the cell membrane. High temperature denatures (destroys) the proteins thereby impairing the functions of the cell membrane.

      c)The cell membrane possesses electric charges- The cell membrane has both positive and negative charges. These charges affect the manner in which substances move in and out of the ells. The charges also enable the cell to detect changes in the environment.

      Physiological Processes of the Cell membrane

      Demonstration of the process of diffusion using_potassium manganate (VII)

      Requirements: potassium manganate (VII) crystals, glass tubing, 100 cm3 beaker and water.

      a) Hold the glass tubing vertically in a beaker so that one end of the tubing rests on the bottom of the beaker.

      b) Cautiously and quickly drop a crystal of potassium manganate (VII) through the upper opening of the glass tubing.

      c) Close the upper hand of the glass tubing with the thumb.

      d) Half fill the beaker with water.

      e) Carefully withdraw vertically the glass tubing so that the crystal is left undisturbed at the bottom of the beaker.

      f) Record your observations for the first 15 minutes.

      g) Explain your observations.

      Expected observations

      The Role of Diffusion in Living Organisms

      Diffusion plays an important role in plants in that:

      In animals diffusion plays the following important roles

      Factors affecting the rate of Diffusion

      b) Surface area to volume ratio

      c) Thickness of membranes and tissues

      Demonstration of Osmosis Using a Visking Tubing

      5OOcm3 beaker, visking tubing, a piece of thread, glass rod, concentrated sugar solution, 500 cm3 distilled Water.

      1. Into the beaker, put 350 cm3 of the distilled water.

      2. Dip the visking tubing in water to moisten it. Open the visking tubing and tie one end with the thread provided.

      3. Half fill the visking tubing with the sugar solution provided and then tie the open end of the tubing. Ensure no sugar solution spills out of the tubing.

      4. Immerse the visking tubing into the distilled water in the beaker and suspend it using the glass rod provided.

      5. Leave the set up for about 30 minutes.

      6. Record your observations.

      7.Explain the observations made.

      Even though there is a higher concentration of sugar molecules in the visking tubing, they were not able to diffuse out of the visking tubing due to their large molecular sizes. The visking tubing is semi permeable.

      Water Relations in Animals

      a) Red blood cell in hypotonic solution e. g. distilled water

      When a red blood cell is placed in a hypotonic solution, water will move into the cell through osmosis. The cell will swell and burst. Swelling of red blood cell when placed in a hypotonic solution is referred to as haemolysis. The cell is said to be haemolysed.

      b) Red blood cell in hypertonic solution

      Water will, therefore, be drawn out of the cell into the hypertonic solution. The cell will shrink and become small. The cell is said to be crenated.

      The process by which animal cells shrink and become smaller when placed in hypertonic solutions is referred to as crenation.

      c) Red blood cell in isotonic solution

      When placed in an isotonic solution, the cell remains unchanged. This is because there will be no net inflow or outflow of water between the cell and the solution.

      This will prevent bursting or shrinking of the cells that would otherwise impair their physiology.

      Water Relations in Plants

      a) Plant cell in hvpotonic solution e. g. distilled water

      Role of Osmosis in Organisms

      As glucose accumulates in the guard cells, the osmotic pressure of the guard cells increase making them to draw water from adjacent cells through osmosis. When the guard cells become turgid, they bulge outwards leading to opening of the stomata.

      Opening of the stomata is crucial as it allows for gaseous exchange in plants. At night, there is no glucose synthesis.

      The glucose available in the guard cells is respired on leading to reduction of glucose and consequently reduction in osmotic pressure. The guard cells lose turgidity and close the stomata.

      Factors Affecting the Rate of Osmosis

      Role of active transport in living organisms

      Factors affecting the rate of Active Transport

      a) Oxygen concentration

      Oxygen is required in respiration process that yields energy for active transport. Under low oxygen concentration, the rate of respiration will be low hence there will be production of little energy leading to low rate of active transport. Increase in oxygen concentration translates into a higher energy production leading to high rate of active transport.

      Change in pH affects the respiratory process which is enzyme controlled. Respiratory enzymes require optimum pH for their efficient activity. Extreme pH conditions will increase lower the rate of active transport since the enzymes controlling respiration Will be denatured.

      c) Glucose concentration

      Glucose is the chief respiratory substrate. At low glucose concentration, there will b less production of energy leading to decreased rate of active transport. Rate of active transport increases with increase in glucose concentration due to increase in the rate of energy production.

      Temperature affects the enzyme controlled respiration process. At low temperatures, the enzymes are inactive hence the rate of respiration will be low resulting into low rate of active transport since there will be less production of energy. An increase in temperature increases the rate of respiration since the enzymes become more activated. At temperatures beyond 40 degrees celcius, the enzymes become denatured, respiration stops and so does active transport.

      e) Presence of metabolic inhibitors e. g. cyanide.

      These are substances which act as metabolic poisons. They stop the rate of respiration leading to production of no energy. Active transport is, thus, stopped.

      Nutrition Plants And Animals

      a) The nutrients are required for growth and development of the living organisms.

      b) The nutrients are required for energy provision as they are broken down to release energy.

      c) They nutrients are also required for repair of worn out tissues

      d) Nutrients are required for synthesis of very vital macromolecules in the body such as hormones and enzymes.

      There are two main nutrition modes:

      a) Autotrophism mode of nutrition through which living organisms manufacture their own food from simple inorganic substances in the environment such as carbon (IV) oxide, water and mineral ions. Organisms that make their own food through this mode are autotrophs.

      b) Heterotrophism mode of nutrition in which living organisms depend on already manufactured food materials from other living organisms. Heterotrophs are the organisms that feed on already manufactured food materials.

      In this mode of nutrition, organisms manufacture their own food from readily available materials in the environment. These organisms use energy to combine carbon (IV) oxide, water and mineral salts in complex reactions to manufacture food substances. Depending on the source of energy used to manufacture the food, there are two types of autotrophism:


      This is the process whereby some organisms utilize energy derived from chemical reactions in their bodies to manufacture food from simple substances in the environment. This nutrition mode is common in non green plants and some bacteria which lack the sun trapping chlorophyll molecule.

      b) Photosynthesis

      Importance of Photosynthesis

      1. Photosynthesis helps in regulation of carbon (IV) oxide and oxygen gases in the environment.

      2. Photosynthesis enables autotrophs make their own food, thus, meet their nutritional requirements.

      3. Photosynthesis converts sunlight energy into a form (chemical energy) that can be utilized by other organisms that are unable to manufacture their own food.

      External leaf structure

      This helps reduce the rate of water loss in such plants. However, the plants in areas of water abundance have broad leaves to enable them lose the excess Water.

      Functions of the cuticle

      a) Being waterproof, it minimizes water loss from the leaf cells to the environment through transpiration and evaporation.

      b) It protects the inner leaf tissues from mechanical damage.

      c) It prevents entry of pathogenic microorganisms into the leaf.

      Functions of the epidermis:

      a) It protects the leaf from mechanical damage.

      b) It also protects the leaf from entry of disease-causing microorganisms.

      c) It secretes the cuticle.

      Adaptations of the guard cells

      c) Palisade mesophyll

      d) Spongy mesophyll layer

      e) Vascular bundle/tissue

      Adaptations of the leaf to photosynthesis

      Raw materials for photosynthesis

      Conditions for photosynthesis

      Photosynthesis Process

      a)Light reaction/Light stage

      i) Photolysis of water

      Water-- Hydrogen atoms + Oxygen gas

      ii) Formation of adenosine triphosphate (ATP)

      b) Dark reaction/Dark stage

      Testing for starch in a leaf

      Factors affecting the rate of photosynthesis

      a) Carbon (IV) oxide concentration

      At this point, other factors such as light intensity, water and temperature become limiting factors.

      Rate of photosynthesis is optimum at (35-40) °C. Beyond 40°C the rate of photosynthesis decreases and eventually stops since the enzymes become denatured.

      Experiment to investigate the gas produced during photosynthesis

      a) Set up the apparatus as shown in the figure below

      b) Place the set up in the sunlight to allow photosynthesis to take place.

      c) Leave the set up in the sun until sufficient gas has collected in the test tube.

      d) Test the gas collected with a glowing splint.

      e) Record your observations.

      1) Carbon (IV) oxide concentration: Carry out the experiment using different amounts of dissolved sodium hydrogen carbonate e. g 5 g, 10g, 15g, 20g and examine the rate at which the gas collects.

      2) Light intensity: An artificial light source can be used. Illuminate the plant and vary the distance between the set up and the light source While recording the time it takes for the gas jar to fill or counting the number of bubbles peer unit time.

      3) Temperature: carry out the experiment at varying temperatures and record the rate at which the gas collects.

      Experiments on factors necessary for photosynthesis

      Carbon (IV) oxide

      Properties of Monosaccharides

      Properties of Disaccharides

      Properties of polysaccharides

      Examples of polysaccharides

      a) Starch- Made by linking numerous glucose molecules. It is a form in which carbohydrates are stored in plants.

      b) Glycogen- Is a storage carbohydrate in liver and muscles of animals. It is broken down to glucose in animals when blood glucose falls.

      c) Cellulose- This is a structural polysaccharide in plants. It is a component of the cell wall

      d) Chitin- A structural carbohydrate found in cell wall of fungi and arthropod exoskeletons

      Functions of polysaccharides

      a) Essential- These are those amino acids that cannot be synthesized by the body systems hence have to be supplied in the diet.

      b) Non essential- These are amino acids that can be synthesized by the body mechanisms hence do not need to be supplied in the diet.

      a) First class proteins- Contain all essential amino acids

      b) Second class proteins- Proteins lack one or more essential amino acids

      Properties of Proteins

      Functions of proteins

      a) They are structural compounds of the body. Cell membrane is protein in nature. Hair, nails and hooves are made up of protein keratin.

      b) Proteins are broken down to release energy during starvation when all carbohydrate and lipid reserves are depleted.

      c) Functional proteins play vital roles in metabolic regulation. Hormones are chemical messengers while enzymes regulate the speed of metabolic reactions.

      d) Proteins such as antibodies provide protection to the body against infections

      e) Some protein molecules are transport molecules. Haemoglobin molecule plays a crucial role in transportation of respiratory gases.

      f) Proteins play a vital role in blood clotting e. g. fibrinogen.

      g) Contractile proteins such as actin and myosin bring about movement.

      What are enzymes?

      a) Extracellular: Are produced within the cells but used outside the cells e. g. digestive enzymes.

      b) Intracellular: Are enzymes produced and used within the cells e. g. respiratory enzymes.

      Importance of Enzymes

      Hydrolysis . ..hydrolase

      Reduction . ..reductase

      Oxidation . ..oxidase

      Mechanism of action of Enzymes

      Properties of Enzymes

      Factors affecting enzyme activity

      d)Substrate Concentration

      e) Enzyme Concentration

      NAD- Nicotine Adenine Dinucleotide.

      FAD- Flavine Adenine Dinucleotide.

      NADP- Nicotine Adenine Dinucleotide Phosphate.

      Competitive inhibitors

      Non competitive inhibitors

      Examples of non competitive inhibitors

      Heavy metals (such as lead, mercury, silver), Cyanide, organophosphates such as malathion.

      Modes of Heterotrophism

      > Rhizobium and leguminous plants: rhizobium fixes nitrogen for the legume while the bacteria obtains manufactured food from the legumes.

      > Lichen: association of fungi (absorbing water and nutrients) and algae (manufacturing food for the association.

      > Catalase digesting bacteria and ruminants.

      b. Premolar and molar

      Classes of Holozoic Heterotrophs

      a) Herbivores: heterotrophs that exclusively feed on vegetation.

      b) Carnivores: heterotrophs exclusively feed on flesh.

      c) Omnivores: heterotrophs that feed on both flesh and vegetation.

      a) Write down its dental formula.

      b) State its mode of feeding.

      b) Periodontal Diseases

      a) Gingivitis- Characterized by reddening of gums, bleeding and pus in the gums.

      b) Pyorrhea- The teeth become loose due to infection of the fibres holding the teeth in the sockets.

      Digestion in the mouth

      a) Sublingual salivary gland beneath the tongue

      b) Sub mandibular gland: under the jaw

      c) Parotid gland: Found in the cheeks in front of the ears.

      Digestion in the stomach

      a) Pepsinogen-This is activated to pepsin which breaks down proteins to peptides.

      b) Rennin- Digests caseinogens protein in milk to casein (curd).

      e) Hydrochloric acid- This:

      d) Mucus- Forms a protective barrier to the stomach wall against corrosion by the HC1. Mucus is secreted by goblet cells in the epithelial membrane of the alimentary canal.

      a) Gall bladder in the liver- Secretes bile.

      b) Pancreas- Secrete hormones and digestive enzymes.

      i. Secretin hormone from the pancreas: Secretin stimulates secretion of pancreatic juice into the duodenum

      ii. Cholecystokinin from the duodenal wall: This stimulates secretion of bile from the gall bladder.

      a) Pancreatic amylase- This facilitates breakdown of the remaining starch into maltose

      b) Trypsin- Digests proteins into peptides.

      c) Pancreatic juice-Digests lipids into fatty acids and glycerol

      d) Sodium hydrogen carbonate- This:

      Provides alkaline medium for activity of the duodenum enzymes.

      i. Aid in emulsification (breakdown of fat molecules into tiny fat droplets to increase surface area for digestion).

      ii. The salts also provide a suitable alkaline medium for action of the duodenal enzymes.

      iii. In addition they neutralize the acidic chyme.

      Digestion in the ileum

      a) Maltase: speeds up breakdown of maltose to glucose

      b) Sucrase: speeds breakdown of sucrose to glucose and fructose

      c) Peptidase: speeds breakdown of peptides to amino acids

      d) Lipase: speeds breakdown of lipids to fatty acids and glycerol.

      e) Lactase: speeds breakdown of lactose to glucose and galactose.

      f) Polypeptidase: speeds breakdown of plypeptides into amino acids

      The mucus secreted by the goblet cells lubricates food along the alimentary canal and also protect the canal from being digested by enzymes.

      At the end of digestion in the ileum, the resulting watery emulsion is called chyle it contains soluble end products of digestion ready to be absorbed.

      a) It is long to provide a large surface area for absorption

      b) It has a narrow lumen so as to bring the digested food into close contact with the walls of the ileum for easier absorption

      c) It is highly coiled to slow down movement of food thus allowing more time for digestion and absorption of food.

      d) The inner surfaces have numerous villi and microvilli to increase surface area for absorption of end products of digestion.

      e) The epithelial lining is one cell thick to reduce the distance through which digested food diffuses.

      f) Has a dense network of blood capillaries into which digested food materials diffuse to increase transport and thus maintain a steep concentration gradient.

      g) Have lacteal vessels in the villi for absorption of fatty acids and glycerol.

      > This is the process through which the undigested and indigestible food substances are eliminated from the body. Caecum and Appendix

      b) Fatty acids and glycerol

      a) Fat soluble vitamins- They dissolve in fats and are often stored in the liver. Include Vitamins A, D, E, K.

      b) Water soluble vitamins- Dissolve in water. Include vitamins B1, B2, B5, B12 and C.

      deficiency disease symptoms

      Vitamine B2 (riboflavine and nicotinic acid)

      deficiency disease symptoms

      Vitamin B5 (pentathonic acid)

      deficiency disease symptoms

      deficiency disease symptoms

      Vitamin C (absorbic acid)

      deficiency disease symptoms

      deficiency disease symptoms

      deficiency disease symptoms

      deficiency disease symptoms

      a) Macro-nutrients: Nutrients required in large quantities. These include nitrogen, sulphur, phosphorous, calcium, sodium, iron and magnesium.

      b) Micro-nutrients: Nutrients required in small quantities. Include copper, manganese, boron, iodine and cobalt.

      Importance of roughage

      a) It rubs against the walls of the alimentary canal stimulating secretion of digestive enzymes and mucus to lubricate the epithelial lining.

      b) Roughage enhance peristalsis since as they rub against the walls of the alimentary canal, they stimulate contraction and relaxation of the muscles.

      c) Roughage is an absorbent it extracts water from the alimentary canal making the fecal matter bulky and moist hence can be easily propelled by peristaltic movements. This prevents constipation.

      Factors affecting energy requirements in humans

      Discuss how the following factors affect energy requirements in humans:

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