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1.2: Science Experiments - Biology

1.2: Science Experiments - Biology



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So what exactly is an experiment?

At first you may picture a science laboratory with microscopes and chemicals and people in white lab coats. But do all experiments have to be done in a lab? And do all scientists have to wear lab coats?

Experiments

Figure below shows a laboratory experiment involving plants. An experiment is a special type of scientific investigation that is performed under controlled conditions, usually in a laboratory. Some experiments can be very simple, but even the simplest can contribute important evidence that helps scientists better understand the natural world. An example experiment can be seen here http://www.youtube.com/watch?v=dVRBDRAsP6U or here http://www.youtube.com/watch?v=F10EyGwd57M. As many different types of of experiments are possible, an experiment must be designed to produce data that can help confirm or reject the hypothesis.

A laboratory experiment studying plant growth. What might this experiment involve?

In this experiment, a scientist is conducting research (and taking notes) while looking through a microscope.

Medicine From the Ocean Floor

Scientists at the University of California, Santa Cruz are looking to perhaps the largest resource yet to be explored for its medical potential: the ocean. And they are taping this resource with some state-of-the-art technology. These scientists are using robots to sort through thousands of marine chemicals in search of cures for diseases like cholera, breast cancer, and malaria. These experiments are described in the following KQED links:

  • www.kqed.org/quest/blog/2009/...e-ocean-floor/
  • www.kqed.org/quest/radio/medicine-from-the-ocean-floor
  • science.kqed.org/quest/slides...oor-slideshow/

Variables

An experiment generally tests how one variable is affected by another. The affected variable is called the dependent variable. In the plant experiment shown above, the dependent variable is plant growth. The variable that affects the dependent variable is called the independent variable. In the plant experiment, the independent variable could be fertilizer—some plants will get fertilizer, others will not. The scientists change the amount of the independent variable (the fertilizer) to observe the effects on the dependent variable (plant growth). An experiment needs to be run simultaneously in which no fertilizer is given to the plant. This would be known as a control experiment. In any experiment, other factors that might affect the dependent variable must be controlled. In the plant experiment, what factors do you think should be controlled? (Hint: What other factors might affect plant growth?)

Sample Size and Repetition

The sample in an experiment or other investigation consists of the individuals or events that are studied, and the size of the sample (or sample size) directly affects the interpretation of the results. Typically, the sample is much smaller than all such individuals or events that exist in the world. Whether the results based on the sample are true in general cannot be known for certain. However, the larger the sample is, the more likely it is that the results are generally true.

Similarly, the more times that an experiment is repeated (which is known as repetition) and the same results obtained, the more likely the results are valid. This is why scientific experiments should always be repeated.

Bio-Inspiration: Nature as Muse

For hundreds of years, scientists have been using design ideas from structures in nature. Now, biologists and engineers at the University of California, Berkeley are working together to design a broad range of new products, such as life-saving milli-robots modeled on the way cockroaches run and adhesives based on the amazing design of a gecko's foot. This process starts with making observations of nature, which lead to asking questions and to the additional aspects of the scientific process. Bio-Inspiration: Nature as Muse can be observed at www.kqed.org/quest/television...nature-as-muse.

Super Microscopes

Microscopes are arguably one of the most important tools of the biologist. They allow the visualization of smaller and smaller biological organisms and molecules. With greatly magnified powers, these instruments are becoming increasingly important in modern day research. See the following KQED videos for additional information on these remarkable tools.

  • Super Microscope at http://science.kqed.org/quest/video/super-microscope/.
  • The World's Most Powerful Microscope at http://www.youtube.com/watch?v=sCYX_XQgnSA.

Summary

  • An experiment is a special type of scientific investigation that is performed under controlled conditions, usually in a laboratory.
  • An experiment generally tests how one variable is affected by another.
  • The sample size in an experiment directly affects the interpretation of the results.
  • Repetition is the repeating of an experiment, validating the results.

Review

  1. What is an experiment?
  2. Compare the dependent variable to the independent variable.
  3. Identify the independent and dependent variables in the following experiment: A scientist grew bacteria on gel in her lab. She wanted to find out if the bacteria would grow faster on gel A or gel B. She placed a few bacteria on gel A and a few on gel B. After 24 hours, she observed how many bacteria were present on each type of gel.

50+ Science Experiments for 1-2 Year Olds (Toddlers)

Can you imagine! Teaching little babies’ science has become easy now.

Yes, with the help of science experiments.

I created this page to list down all Science Experiments for Toddlers (in the age group of 1-2).

I know that toddlers crave for attention and their mind is curious to explore everything they come across. Be assured, these are golden period for any kid as 80% of brain development happens below 3 years of growth. This is the right age to introduce science.

Yes, I am not joking and I have done it with my two daughters. We have collected several experiments suitable for kids of age 1 and 2. Here in this article, you will find a brief intro for the experiment and the link where you can find the detailed steps to do the activity.

Spend quality time with kids from their young age, as tender age is the right age for them to grasp things quickly.

We have crafted our toddler section having this in mind. Our activities help develop their motor skills and kindle curiosity about science. We strongly believe some of these activities will be well suited to try at your home with your little buds.


Super Cool Walking Water Experiment – A simple and beautiful look into absorption and color mixing. What a fun way to capture children’s natural curiosity.

Why Do Leaves Change Color? – This experiment answers a question that most kids ask during the fall! What a super cool, but super simple way for them to experiment and get the answer themselves.

How are Stalactites Formed? – Help children answer this question with a simple, hands-on science experiment! Kids will learn about saturation and mineral deposits along the way.


6 Quick and Easy Science Experiments

6. Ziplock Time Bomb

(Photo courtesy of AlphabetSummerKits.com)

I don’t think this science experiment (cleverly disguised as an awesome way to make things go BOOM) needs much more introduction than what it says in the title. Ziplock. Time. Bomb. What more do you need?

Well, maybe a quick warning: don’t do this inside. This is definitely an outdoor activity, because while the blast radius isn’t all that big, everything within it is gonna get wet. And also maybe a little smelly.

  • 1 Ziplock bag (or other plastic sandwich bag), preferably of the “Freezer” variety for extra-secure closure
  • 1/4 cup warm water
  • 1/2 cup vinegar
  • 3 teaspons baking soda
  • 1 tissue
  1. First, GO OUTSIDE.
  2. Put the warm water into the sandwich baggie (Ziplock brand or otherwise)
  3. Add in the vinegar
  4. Pour the baking soda into the middle of the tissue (Kleenex brand or otherwise)
  5. Crumple the tissue into a nice, tight ball with the baking soda safely secured in the center
  6. Zip the baggie as much closed as you can, still leaving room to put in the tissue ball
  7. Now, comes the part where you have to work fast
  8. Put the tissue into the water/vinegar-filled baggie, zip it all the way closed, and either toss it aside or run away
  9. Watch as the baggie goes boom!

Did We Learn Anything…?

Believe it or not, we did. When vinegar and baking soda come together, we get an Acid-Base reaction, which creates carbon dioxide. The gas needs room that the baggie doesn’t offer, so it grows and grows and grows, pushing the baggie out and out and out, until it finally explodes!

The tissue gives you the time to close the baggie and either toss it or run, since the baking soda can’t react with the vinegar until the tissue has dissolved or opened enough to let the two substances touch each other.

If you want to play with the “Time” part of the “Ziplock Time Bomb”, you can turn this into a kind of experiment by playing with how many tissues you can use, or what other wrapping materials might work to give you more time.

Just remember, as Uncle Ben says: with great power comes great responsibility. Use your new skills as a time bomb builder for good and never for evil. (Unless scaring the holy heck out of a sibling is considered evil… Because that’s probably okay in my book.)

5. Peep Wars

I grew up Jewish, so the only thing I know about Easter is Peeps.

And we ate a LOT of Peeps ’round Easter (even though they aren’t Kosher for Passover).

This is a quick, easy and fun science experiment regardless of your Geeky Denomination. So bust out this page whenever your Geek has had his full of Peeps or Passover has begun and there are extra Peeps lying around. Outside of eating ’em, this is the best thing to do with those pesky Peeps.

Yes, they’re delicious, in a tasteless kind of way. Yes, they’re fun to pinch, poke and squeeze. But holding your first annual Family Peep Wars is going to be so much more fun.

  • 2 Peeps (any animal and color will do, though for the sake of a fair fight, they should probably both be about the same size)
  • 2 toothpicks
  • 1 microwave
  1. Insert one toothpick into each Peep
  2. Place Peeps on a microwave-safe plate with toothpicks aimed at each other
  3. Put plate in the microwave and turn that sucker on for about 30-45 seconds
  4. Watch in wide wonder as the Peeps battle for their lives
  5. Take out plate when microwave dings and see which Peep has been stabbed by the other and exploded…
  6. Enjoy a delicious dish of Peep brûlée (if you can stomach it).

Did We Learn Anything…?

Yes! Well… Not a lot, but… Sure. We learned that Peeps expand when heated.

We also learned who among your family is the better Peep General of the bloody Peep Wars.

We also learned, after seeing the aftermath of a Peep War, that Jeff Goldblum may have actually gotten off easy in The Fly. He might have come out of that thing looking like small puddle of gooey goo.

Annnnnnd, we may also have learned that despite our sickened stomachs at having eaten so many of these guys already, the taste of warm Peep goo is definitely too good to pass up.

4. Glitter Volcano

(Photo courtesy of PreschoolPowolPackets.blogspot.com)

If your little girl isn’t terribly fond of the idea of a Ziplock Time Bomb, don’t fret. You can use the very same Acid-Base reaction principles with a different experiment.

  • 1 bottle, preferably a fancy-looking one (to increase the experiment’s fabulosity)
  • 2-3 tablespoons baking soda
  • 1/2 cup vinegar
  • 5-10 drops food coloring (any color you like!)
  • 1-3 teaspoons glitter (any color at all!) (Click Here to Buy Glitter at Amazon and Help Support GeeksRaisingGeeks!)
  • Pot, pan or aluminum foil to limit this unnatural disaster’s fabulous mess
  1. Put your fancy bottle on or in the pot, pan or aluminum foil
  2. Pour the baking soda in the bottom of your fancy bottle
  3. Add the food coloring and glitter
  4. Dump in the vinegar, stand back, and enjoy this fabulous volcano’s fabulously sparkly eruption

Did We Learn Anything…?

Sure we did! We learned, again, that when acids and bases get together, they react. Here, the vinegar and baking soda created carbon dioxide and bubbled up and over the side of the bottle.

Also, we learned how to make the prettiest darn volcano there ever was.

3. Blazing Benjamins

Money isn’t everything. Money isn’t everything. Money isn’t everything. No matter how many times you tell that to yourself, you still can’t help letting out a small squeal of pain when The Joker lights that mountain of cash on fire in The Dark Knight, can you? No, of course not.

But it’s a good lesson to learn. One your kids would do well to learn early.

This is more than a lesson, though. This is like magic. And once your kid has finished his or her own small squeal, they’ll delight in the sheer joy of the trick.

  • 1 dollar bill (any denomination will do, but the more zeroes the better for psychological effect!)
  • 1/2 cup 91% rubbing alcohol
  • 1/2 cup water
  • 1/4 teaspoon salt
  • A pair of tongs
  • Long match or long-handled lighter
  1. Fill a bowl with the alcohol, water and salt
  2. Put the bill in the bowl and let it soak for 5-7 minutes
  3. Wash your hands to get rid of all alcohol on them!
  4. Pick up bill with tongs
  5. Light it on fire
  6. Let out a small squeal
  7. Watch in amazement

Did We Learn Anything…?

Heck, yeah! We learned that we care far too much about money than we should (psychologically speaking). Because first of all, be honest, you used a one dollar bill. You didn’t take my advice and use even a Benjamin, did you? (Geez, man, where’s the trust…?)

We also learned that alcohol burns very fast. So fast, in fact, that the dollar bill (which is made from cotton, not paper) was still sopping wet when the flame burned out, leaving it free and clear of any potential burn damage.

We also might have learned (or, at least I did), that no one wants to take your money if it’s soaking wet. (Hint: only try this trick is you’re not planning on spending the Benjamin for at least an hour…)

2. Old School Secret Messages

Who doesn’t love a good spy movie? What kid has never dreamed of being the next James (or Jane) Bond? How can you become the coolest mom or dad in the world?

The answers to these three questions are:

This is a pretty old trick (one of the oldest, in fact), but it never ceases to amaze children of all ages.

  1. Write a message on the paper using lemon juice as the ink
  2. Let the secret message dry
  3. Hold paper up to light bulb, sunlight, iron (no steam!) or other source of heat
  4. Watch the secret message appear in brown

Did We Learn Anything…?

You mean besides the fact that your kids now think you’re a wicked combination of James Bond, Sirius Black and that dude with the obviously fake hair and speedily fading talent from National Treasure?

Well, yeah. Namely: paper weakened by an intruding element (say, lemon juice) will burn faster than the paper that’s unaffected. The secret message shows up in brown because that part of the paper is beginning to burn!

Some quick tips: cotton balls and Q-tips are great writing implements that can be tossed out after use, apple juice works as well as lemon juice, and be VERY careful when revealing the message–the last thing I want to be responsible for is creating a Bond/Black/Baldy who burns down the house in front of their kid… Like this parent is obviously about to do:

1. Oobleck Blech

This experiment is simultaneously AWESOME and GROSS. Oobleck is the given name for a simple substance that look and feels different under separate circumstances. One minute it can be drippy, ooey and gooey, and in the next moment it’s solid and dependable.

Follow the directions below to create your own batch of wonderfully awful oobleck.

  1. Simply mix the water and corn starch (and optional food coloring) together in the bowl
  2. Play with it!
  3. Easy-peasy

(You can also adjust the viscosity, or thickness, of the oobleck by using more or less corn starch.)

Did We Learn Anything…?

We learned that sometimes really gross things are also really cool things.

Also that a state of being can be so fragile sometimes that the heat from simple motion can change it from a solid to a liquid. I’m sure there’s also a really great lesson about emotions and talking to someone about your feelings, but really all I can think about is how that weirdly wonderful stuff felt between my fingers.

So horribly awesome and disgustingly amazing.

Final Thoughts…

So, maybe neither you nor your kid ever wanted to be Mr. Wizard, Bruce Banner or Bill Nye. Maybe that was all just me.

But, still! You can’t go through all of these wicked awesome experiments with your kids and tell me they didn’t fall head over heels in love with it. You can’t!

You are now one step closer to becoming the ultimate mom or dad. Geeks, beware! A new leader is emerging and his/her name is… YOU!


Crying over broken candy canes? Cry no more. Make art!

Candy Cane Art- image KitchenPantryScientist.com

*Melted candy can get dangerously hot, so parental supervision is required!

-candy canes (broken or whole), wrappers removed

  1. Preheat oven to 250F.
  2. Cover cookie sheet with foil
  3. Place candy canes on foil, not touching each other
  4. Bake candy canes for around 10 minutes and have an adult check them. They should be stretchy, but not too hot to touch.
  5. When the candy canes are ready, bend, fold, twist and pull them into cool shapes. Try pulling one long and wrapping it around a chopstick to make a spiral. What else could you try?
  6. If the candy gets to brittle to work with, put it back in the oven for a few minutes to make it soft again.

Candy Cane Art- image KitchenPantryScientistcom

The science behind the fun:

If you looks at the ingredients of candy canes, they’re usually made of table sugar (sucrose), corn syrup, flavoring, and food coloring. Glucose and fructose are sweet-tasting molecules that stick together to make up most of the sugars we eat, like table sugar (sucrose) and corn syrup. You can think of them as the building blocks of candy.

At room temperature, candy canes are hard and brittle, but adding heat changes the way the molecules behave. Both table sugar and corn syrup contain linked molecules of glucose and fructose, but corn syrup has much more fructose than glucose, and the fructose interferes with sugar crystal formation. According to Andrew Schloss, “the corn syrup has more fructose, which means the sugar crystals in the candy don’t fit tightly together. The crystals have space between them, which allows them to bend and move without cracking.

Here’s a great article on the science of candy-making.

If you’re looking for holiday gifts for a science-loving kid, my books Chemistry Lab for Kids , Kitchen Science Lab for Kids and Outdoor Science Lab for Kids include over 100 fun family-friendly experiments! They’re available wherever books are sold.


Learn about water absorption and colour blending with these simple experiments:

And lastly, there’s this classic science experiment. Dyeing flowers with water and food colouring. I haven’t a post to go along with this photo of mine, so I’ll send you over to Twig and Toadstool to see how they recently coloured a bouquet of rainbow daisies.


27 Cool Second Grade Science Experiments and Activities For The Classroom and Beyond

These simple ideas will help kids fall in love with science!

Science is best with hands-on experience. That’s why we’re such fans of these second grade science projects, demos, and experiments. Students gain a deeper understanding of the properties of matter, earth science, and a whole lot more, and every idea is simple enough for any teacher to handle!


1. Experimentation and Causal Reasoning

1.1 Mill&rsquos Methods in Experimental Biology

Causal reasoning approaches try to reconstruct and sometimes justify the rules that allow scientists to infer causal relationships from data, including experimental data. One of the oldest such attempts is due to John Stuart Mill (1996 [1843]), who presented a systematic account of causal inference that consisted of five different so-called &ldquomethods&rdquo: The Method of Agreement, the Method of Difference, the Joint Method of Agreement and of Difference, the Method of Residues, and the Method Concomitant Variation. While some of these &ldquomethods&rdquo pertain more to observation, the Method of Difference in particular is widely seen as encapsulating an important principle of scientific reasoning based on experiment. Mill himself characterized it thus: &ldquoIf an instance in which the phenomenon under investigation occurs, and an instance in which it does not occur, have every circumstance in common save one, that one occurring only in the former the circumstance in which alone the two instances differ, is the effect, or the cause, or an indispensable part of the cause, of the phenomenon&rdquo (Mill 1996 [1843], Ch. 8, §2). Thus, Mill&rsquos method of difference asks us to look at two situations: one in which the phenomenon under investigation occurs, and one in which it does not occur. If a factor can be identified that is the only other difference between the two situations, then this factor must be causally relevant.

As Mill noted, the method of difference is particularly germane to experimental inquiry because such a difference as is required by this method can often be produced by an experimental intervention. Indeed, according to a position known as interventionism about causality there is a tight connection between the concept of cause and experimental interventions (Woodward 2003).

Mill&rsquos method of difference captures an important kind of reasoning that is used frequently in biological experiments. Let&rsquos suppose we want to find out if a newly discovered compound is an antibiotic, i.e., inhibits the growth of certain bacteria. We start by dividing a bacterial cell culture into several aliquots (samples of same size derived from a homogeneous solution). Then, we add to one group of aliquots the suspected antibiotic that is dissolved in phosphate buffer (&ldquotreatment&rdquo). To the other group, we add only the phosphate buffer (&ldquocontrol&rdquo). Then we record bacterial growth in all the samples (e.g., by measuring the increase in optical density as the culture medium clouds up due to the bacteria). This experimental setup makes sure that the treatment and control samples differ only in the presence or absence of the antibiotic, thus ruling out that any observed difference in growth between the treatment and control aliquots is caused not by the suspected antibiotic but by the buffer solution. Let us denote the antibiotic as &ldquoA&rdquo and the growth inhibition as &ldquoW&rdquo. Biologists would thus infer from this experiment that A is an antibiotic if W is observed in the samples containing A but not in the samples not containing A.

Mill construed this &ldquomethod&rdquo in terms of a principle of inductive inference that can be justified pragmatically. However, it is interesting to note that the principle can also be viewed as instantiating a form of deductive inference.

To this end, of course, the Method of Difference must be strengthened with additional premises. Here is one way how this can be done (adapted from Hofmann and Baumgartner 2011):

  1. S1 and S2 are two homogeneous test situations (assumption)
  2. Two factors A and W both occur in S1 both not in S2 (exp. result)
  3. W is an effect in a deterministic causal structure (assumption)
  4. In S1 there exists a cause of the occurrence of W (from 2, 3)
  5. In S2 there exists no cause of the occurrence of W (from 2,3)
  6. S2 contains no confounder of W (from 5)
  7. S1 contains no confounder of W (from 1,6)
  8. The cause of W belongs to the set (from 4, 7)
  9. W does not cause itself (assumption)
  10. A is the cause or a part of the cause existing in S1

Some of the terms used in this deduction require explication. Two test situations are homogeneous on the condition that, if a factor is causally relevant and is present in test situation S1, then it is also present in test situation S2, and vice versa. A confounder would be a causally relevant factor that does not belong to the set . The presence of such a confounder is excluded by the assumption of causal homogeneity (1). In practical situations, a confounder might be an unknown or uncontrolled (i.e., not measurable or not measured) factor that is present in only one of the test situations. In our antibiotics example, this could be some chemical that was put into just one aliquot inadvertently or without knowledge of the experimenter. In fact, the risk of a confounder is precisely why our biological experimenter will divide up the mother culture into aliquots just before putting in the substance to be tested. This makes it unlikely that one aliquot contains an uncontrolled chemical that the other does not contain. Furthermore, a skilled experimenter will make sure that the cultures are well stirred, thus preventing a physical-chemical inhomogeneity of the culture (e.g., some chemical or temperature gradient). Thus, there are typical laboratory manipulations and procedures that reduce the risk of confounders.

In spite of these control procedures, it is clear that the derivation of a causal factor from a Millean difference test presupposes strong assumptions. In particular, it must be assumed that we are dealing with a deterministic causal structure (3) and that nothing happens uncaused (4). In our simple example, this amounts to assuming that the bacteria don&rsquot exhibit any kind of spontaneity, in other words, their growth behavior is assumed to be determined by their genetic constitution and their environment (although most biologists are convinced that their experimental organisms have good and bad days just like themselves!).

If we thus construe Millean causal reasoning as deductive reasoning, all the inferential risks are shifted from the induction rules into the premises such as causal homogeneity, determinism and the principle of universal causality. It is a characteristic feature of inductive inference that this is always possible (Norton 2003). A justification of these premises, of course, does not exist. They may be viewed as being part and parcel of a certain kind of experimental practice that is vindicated as a whole by its fruitfulness for research (see Section 5).

1.2 Generalizations of Mill&rsquos Methods

Mill&rsquos methods can be formalized and generalized into rich and sophisticated methodologies of causal reasoning (e.g., Ragin 1987, Baumgartner 2009, Graßhoff 2011, Beirlaen, Leuridan and Van De Putte 2018). Such accounts haven been successfully used in the reconstruction of historical episodes such as the discovery of the urea cycle (Graßhoff, Casties and Nickelsen 2000 Grasshoff and May 1995).

Mill&rsquos methods and their generalized versions may even be viewed as providing some kind of a logic of discovery (see also Schaffner 1974), the existence of which has long been controversial (Nickles 1980). However, it should be noted that the methods of causal reasoning do not generate causal knowledge from scratch, as it were. They already take causal hypotheses as inputs and refine them in an iterative way (Grasshoff 2011). While some formulations (including Mill&rsquos own mentioned above) may suggest that the inputs to Mill&rsquos methods are mere associations or regularities, it should be clear by now that the method is only reliable if some kind of causal knowledge is already at hand. In our example above, the causal assumption is that of causal homogeneity, which obviously has causal content. This vindicates the slogan &ldquono causes in, no causes out&rdquo (Cartwright 1989, Ch. 2).

This discussion has focused on deterministic causal reasoning, which is widespread in experimental biology. It should be mentioned that, of course, there are also statistical inference methods of the kind formalized in Spirtes, Glymour and Scheines (2000) in use, in particular regression analysis and analysis of variance, which are frequently used in biological field experiments. Wet lab experiments, by contrast, rarely require such techniques.

Some enthusiasts of causal inference methods believe that a sophisticated version of Mill&rsquos methods (and their statistical counterparts) are basically all that is needed in order to account for experimental practice (e.g., Graßhoff 2011). An attraction of this view is that it can be construed essentially as requiring only deduction and no cumbersome inductive methods.

1.3 Mechanistic Constitution and Interlevel Experiments

Experimental methodology has traditionally been mainly concerned with inferring causal dependencies. However, recent research suggests that we need to broaden its scope. A considerable body of scholarship documents that much biological research is best described in terms of the search for mechanisms, which may be understood as collections of entities and activities that produce a phenomenon that biologists want to understand (e.g., Wimsatt 1974, Machamer, Darden and Craver 2000, Glennan 2005, Bechtel 2006, Craver 2007a). Mechanisms are both what biological science is aiming at and a means to this end, for sketches or schemes of mechanisms can guide scientists in the discovery of missing parts (Darden and Craver 2002, Scholl and Nickelsen 2015).

According to Craver (2007b), we should distinguish between two kinds of relations that make up mechanisms: (1) causal and (2) constitutive relations. The former may hold between different parts of a mechanism. For example, in the basic mechanism of synaptic transmission at the terminal part of a neuron, the influx of calcium causes the release of neurotransmitter in the space between the synaptic terminal and the postsynaptic cell membrane. This causal link can be understood pretty much as discussed in the last two sections. The other kind of relation, mechanistic constitutive relevance (or just mechanistic constitution) holds between the parts and of a mechanism and the phenomenon the mechanism is for. For example, the influx of calcium into an axon terminal, together with other events, constitutes the phenomenon of synaptic transmission. Craver (2007b) contends that this is not a causal relation because the relata cannot be viewed as distinct and non-overlapping.

But what defines constitutive relevance? Inspired by interventionism about causality, Craver argued that it is best defined by the kinds of interventions that are used by biologists in order to find out whether some entity and an associated activity are part of a mechanism: by certain kinds of experiments. In particular, there are two kinds of so-called interlevel experiments the combination of which establishes (and defines) constitutive relevance. In the first kind, an intervention is performed on some part and an ensuing change is observed in the phenomenon under study. To return to our synaptic example, a calcium antagonist may be used to show that preventing the binding of calcium ions to their receptors prevents the release of neurotransmitter. This is a bottom-up experiment. The second kind of inter-level experiment intervenes on the phenomenon as a whole in order to see some change in the parts. For example, stimulating synaptic transmission by increasing the rate by which action potentials arrive at the terminal will lead to a measurable increase in calcium influx at this terminal. This can be done, for example, by asking a subject to perform a cognitive task (such as trying to memorize something) and by observing changes in calcium concentration by functional magnetic resonance imaging (fMRI). Thus, mechanistic constitution is defined by the mutual manipulability of the parts of mechanisms and the mechanism as a whole.

Recent debate has challenged the mutual manipulability account (Leuridan 2012, Harinen 2018, Romero 2015). One issue is that inter-level experiments are necessarily &ldquofat-handed&rdquo (Baumgartner and Gebharter 2016) because they change the values of at least two different variables residing at different levels (e.g., calcium binding and synaptic transmission, where the former is a part of the latter). But this threatens to undermine the inferences to mechanistic constitution. A possible solution might consist in inferring constituents abductively, by positing constitutive relations as the best explanation for the presence of common causes that unbreakably correlate phenomena and their constituents (Baumgartner and Casini 2017).

Thus, the discovery of mechanisms in biology may require a set of experimental reasoning principles that must supplement Mill&rsquos methods, even if there are considerable similarities between these principles and the better-known principles of causal inference (Harbecke 2015).


Extract DNA From a Banana

Introduction

Extract DNA From a Banana: What do you have in common with a banana? Even though we might not look alike, all living things—bananas and people included—are made up of the same basic material.

Just like houses are made up of smaller units such as bricks, all living things are made up trillions of microscopic building blocks called cells. Within an organism, each cell contains a complete set of “blueprints”. These directions determine the organism’s characteristics.

Background

If we could zoom in on a single, tiny cell, we could see an even teenier “container” inside called a nucleus. It holds a stringy substance called DNA, which is like a set of blueprints, or instructions. DNA contains a code for how to build a life-form and put together the features that make that organism unique. Segments, or pieces, of DNA are called “genes”. In living things, such as us, each gene determines something about our bodies—a trait. In our DNA there are genes that are responsible for hair color, eye color, earlobe shape and so on. We get our DNA from our parents. Some characteristics, like eye color, are pretty much entirely determined by DNA. Some are determined both by DNA and by your environment as you grow up, like how tall you will be as an adult. And some traits are not very directly tied to DNA at all, like the kind of books you like to read.

Just like us, banana plants have genes and DNA in their cells, and just like us, their DNA determines their traits. Using only our eyes, we couldn’t see a single cell or the DNA inside of it. If we remove DNA from millions of cells, however, we will be able to view it without a microscope. That is what we will do today!

Materials & Tools:

Onion (2),Ethanol, Water, Dish Washing Liquid, Salt ,Petri Dish, Beakers, Cutting Board, Tea Strainer, Cutter, Tea Spoon, Match Box, Spirit Lamp, Tripod Stand with Wire Gauze, Blender/Mixer


List of 16 Science Experiments

1. COKE AND MENTOS EXPERIMENT FOR KIDS

This is a reaction between Mentos candy and cola. The experiment involves dropping several Mentos candies (usually 5–8) into a bottle of diet cola resulting in an eruption occurring because of rapidly expanding carbon dioxide bubbles on the surface of the Mentos.

If you want an explanation:

There are various theories being debated as to the exact scientific explanation of the phenomenon, many scientists claim that it is a physical reaction and not a chemical one. Water molecules strongly attract each other, linking together to form a tight connection around each bubble of carbon dioxide gas in the soda. To form a new bubble, water molecules must push away from one another. It takes extra energy to break this surface tension. So, in other words, water resists the expansion of bubbles in the soda.

When Mentos are dropped into soda, the gellan gum and gum arabic of the candy dissolves and breaks the surface tension. This disturbs the water connection so that it takes less work to expand and form new bubbles. Each Mentos candy has thousands of tiny pores over its surface. These tiny pores function as nucleation sites, perfect places for carbon dioxide bubbles to form. As soon as the Mentos enter the soda, bubbles form all over their surface. They quickly sink to the bottom, causing carbon dioxide to be released by the carbonated liquid with which they come into contact along the way. The sudden increase in pressure pushes all of the liquid up and out of the bottle.

2. ALKA-SELTZER ROCKET EXPERIMENT

A model rocket fashioned from a 35mm film canister and propelled by the generation of gas from an effervescent liquid. It is often used in science classes to demonstrate principles of chemistry and physics to students.

1. In the experiment, a film canister is filled with water and an effervescent tablet (commonly Alka-Seltzer) and tightly sealed.

2. After a short time, the evolved carbon dioxide reaches sufficient pressure to cause the body of the canister to be launched into the air with a popping sound.

3. The canister may be elaborated with paper fins to resemble more closely af real rocket.

(K-A tested) MORE SIMPLE ROCKET LAUNCH… Fill a small plastic film canister (Fuji works well) with one teaspoon of water. Quickly add one Alka-Seltzer tablet, put the lid on and place the canister on the floor with the lid side down. Wait about 10 seconds and whoosh! Your rocket should fly into the air.

3. BUILDING A MACARONI SKELETON

✓ Black construction paper (approximately 6″ x 11.5″) ✓ Glue that will dry clear ✓ Lima beans (head, thorax, hips) ✓ Short, small macaroni in a tube (spine) ✓ Thin twisted macaroni (arms, legs) ✓ Elbow noodles (ribs) ✓ Small shells (joints) ✓ Spaghetti (fingers, toes) ✓ Black permanent marker

  1. Build a sample skeleton for the children to copy from. Review the key features with them.
  2. Guide children to build their skeleton working from the head down (i.e., head, neck/trunk, ribs, etc.), gluing the macaroni and beans to the paper as they go.
  3. When the glue and macaroni have set, have them draw a smile and eyes on the “head”.

As preparation for this project, study the human skeleton. Talk about symmetry between the two sides of the body, and how many ribs, fingers, and toes we have. Source: Kaboose.com

4. EGG DROP SCIENCE EXPERIMENT

(K-A tested-the grade school and middle school kids loved it!)

Each student works within guidelines to fashion a container for an egg so that the egg won’t break when the student drops it from an established height…

Use hard-boiled eggs (you could probably do raw-but be cautious of Salmonella and spoilage!).

Have each child create their own container for the egg — with the purpose of the egg not breaking. Some kids have used “parachutes,” and cans with foam. It can be a lot of fun!

Of course, everyone’s hypothesis should be that their egg won’t break.

The testing is the fun part—when the kids see if their egg remains intact! For this, you want to drop the egg container from the highest available point. A second-floor balcony, off the top bleacher of the football field or by a teacher on a ladder?

*Even though this is for older students, it can be adapted to the lower grades without going into weight and velocity.

5. INVISIBLE INK SCIENCE EXPERIMENT

✓ 2 tablespoons of pure lemon juice ✓ cotton swabs

  1. Pour the lemon juice into a small dish.
  2. Soak the end of a cotton swab in the lemon juice and use it to write a secret message or a picture.
  3. To read or see your secret message, hold the paper near a warm light bulb, burner, or toaster.
  4. The heat will turn the invisible writing brown and you can see it!

6. SPIN EXPERIMENT FOR KIDS (HOW LONG CAN YOU SPIN?)

✓ Film canister lid ✓ Construction paper ✓ Bamboo skewer ✓ Tape ✓ Scissors

1. Cut a circle out of construction paper, about the size of a DVD or CD.

2. Tape a film canister lid to the center of the paper circle. (You can draw a design on it-that would look interesting spinning)

3. With an adult- poke or drill a hole through the film canister lid.

4. Poke the skewer through the hole in the lid.

5. Keep the paper circle near the point of the skewer. Give the skewer a twirl.

HOW DOES IT WORK?

The paper circle gives the skewer extra mass. When you twirl the skewer, you also twirl all the mass of the paper circle. A spinning mass tends to keep spinning unless something like friction slows it down.

About 72% of kids can make it spin MORE than 10 seconds…

7. CENTER OF GRAVITY EXPERIMENT

Even George Washington couldn’t do this dollar pick-up trick!Tell the children you’ll give them each a dollar if they can pick it up from the floor. But there is a catch: They have to pick it up using your instructions. You’ll have fun fooling them with this easy indoor game for kids.

You’ll need a dollar bill and a wall…

Step 1: Have children stand with their feet together and heels up against a wall.

Step 2: Put dollar bills on the floor 12 inches in front of their feet.

Step 3: Tell them to pick up the dollars without bending their knees or moving their feet.

It is impossible to do! Why? When you are standing against a wall, your center of gravity is over your feet. If you bend forward, you have to move your center of gravity forward to keep your balance. Since you can’t move your feet during this trick, you’re flat out of luck. But that’s better than being flat on your face!

8. RINGING EARS — SIMPLE SOUND EXPERIMENTS FOR KIDS

✓ A Fork ✓ A Spoon ✓ 3 feet of String/Thread

  1. Take the string and tie the fork to the center of the string/thread.
  2. Take one end of the string/thread and tie it around your right index finger (pointer), then tie the other end of the string/thread around your left index (pointer) finger.
  3. Place your fingers (index/pointer) to your ears and let the fork dangle in front of you.
  4. Get someone to tap the fork with the spoon. You should hear loud ringing in your ears.

The ringing sound travels up the string/thread to your ears.

You could tie other metal objects to the string/thread to see what sounds travel to your ears.

9. MUMMIFICATION SCIENCE EXPERIMENT

Discover how the Ancient Egyptians used drying as one step

#1 EXPERIMENT: FISH MUMMY

✓ l raw fish from the market ✓ Two boxes of baking soda ✓ Kitchen scale ✓ Plastic container with a lid

Instructions

  1. Weigh the fish on a kitchen scale.
  2. Coat the fish inside and out with baking soda, and bury it completely in baking soda in the plastic container. Let it sit this way for a week in a cool shady place (in a refrigerator, if you like).
  3. After a week, take it out, dust it off, and weigh it again. Re-bury it in fresh baking soda, for another whole week.
  4. Take it out and weigh it once more.

What does the fish look, feel, and smell like?

HOW’S IT WORK?

Baking soda (PDF) acts as a preservative and drying agent. The weight loss you noticed is due to the removal of water by the baking soda. Drying the fish is essential to making it a mummy. What happened after the first week? After the second week?

10. SINK OR FLOAT — WATER BUOYANCY EXPERIMENTS

CAN YOU SINK AN ORANGE?

Instructions

  1. Fill the bowl with water.
  2. Put in the orange…What happens to the orange? See if you can get the orange to sink.
  3. Take the orange and peel it.
  4. Place the peeled orange back in the bowl of water. What happens this time?
  5. The orange sinks because the orange peel if full of trapped air pockets, therefore making the orange light for its size (so it floats).
  6. When you remove the peel (including the air pockets) the orange weighs a lot for it.

Along with the above experiment try a ‘Sink or Float with a Pumpkin or Watermelon!

  • Fill a bin or aquarium or tub half full of water. Place everyday items near the bin. Get the kids to guess which items would sink and which ones would float. Have youth write their guesses in their notebooks. Then do the experiments to determine if they were right or not.
  • Be sure to add watermelon to the guess! (You can eat it afterward!) Pumpkins are also fun. The pumpkin and watermelon will float because its mass is less than the mass of water it displaces. This is due primarily because the inside of the pumpkin and melon are hollow. It is mostly air, which has a much lower mass than water.

11. CRYSTAL GROWING EXPERIMENTS

✓ Epsom salt ✓ a tablespoon ✓ a cup of water ✓ a paper circle ✓ a jar lid

Instructions

  1. Cut out a paper circle the same size as the jar lid. Put the circle in the lid.
  2. Measure 4 big tablespoons of Epsom salt. Don’t worry if you add too much – the more, the better.
  3. Dissolve all 4 tablespoons in the water and stir the mixture thoroughly.
  4. Pour the water mixture into the jar lid. Stick the lid in a place where it won’t be disturbed. It will take a few days, but let the water evaporate and see what happens!

HOW’S IT WORK?

In a few days, the water will evaporate from the lid. But the Epsom salt will be left behind. The salt will build up into its own unique crystal shape. You can make a miniature rock forest.

12. BAKING SODA AND VINEGAR EXPERIMENT VOLCANO (IN DISH)

This is a classic science experiment and an easy one. To make the volcano, mix 6 cups flour, 2 cups salt, 4 tablespoons cooking oil, and 2 cups of water. The mixture should be smooth and firm.

Stand a large soda bottle in a baking pan or shallow dish, and begin to shape the dough around it. Don’t cover the hole and don’t drop any of the dough into it. Fill the bottle about three-quarters full with warm water and a few drops of red food coloring. Add 6 drops of liquid detergent to the bottle, and 2 tablespoons of baking soda.

Slowly pour vinegar into the bottle and step back!

13. DANCING POPCORN

Fill a clear cup 3/4 full with vinegar. Add 1/2 teaspoon baking soda. Drop-in a few kernels of unpopped popcorn. Watch as the kernels rise and fall.

Variations: Try substituting club soda for the vinegar and baking soda. You can also try using other objects like buttons or pebbles.

14. BREAD MOLD EXPERIMENT

This is a very easy science experiment. The most difficult part is the patience to see the experiment through!

Children seem to love watching mold grow. Here is a safe way to experiment with mold.

  • Give children a small zip-lock bag and a piece of bread.
  • Have them place the bread into the bag and then add a teaspoon of water. Zip up the bag and set out the bag to observe.
  • After a few days, mold will appear on the bread.
  • Discard bags unopened, when the experiment is over.
  • Variation: You may want to repeat this experiment, but this time make two bags of water and bread and put one in the center and one in the refrigerator. Which one grows mold the fastest?

15. FINGERPRINT LIFT EXPERIMENT

Here’s an amazing trick that lets children try their hands at a little forensic science by lifting their own fingerprints.

1. Individually, have each child press their fingertip on a pocket mirror.

2. Cover the entire print with graphite dust by rubbing a soft pencil with sandpaper.

3. Blow gently to remove excess dust.

4. Now carefully stick a strip of tape to the print and slowly peel it off. Stick the tape to a piece of white paper, and the print should be distinct. You can inspect the fingerprint under a magnifying glass, or just with the eye. If you go to the wiki website, I you can decide whether the fingerprints are ‘s’ whirl, loop, or an arch.

16. MAKE A ‘NAKED EGG’ — EGG IN VINEGAR EXPERIMENT

A naked egg is an egg without a shell. Using vinegar, you can dissolve the eggshell–without breaking the membrane that contains the egg.

✓ Eggs ✓ White vinegar ✓ A container big enough to hold all the eggs a cover for the container ✓ A big spoon

Instructions

  1. Place eggs in the container so that they are not touching.
  2. Add enough vinegar to cover the eggs. Notice that bubbles form on the eggs. Cover the container and put it in the refrigerator. Let the eggs sit in the vinegar for 24 hours.
  3. Using the spoon, scoop the eggs out of the vinegar. Be careful–the eggshell has been dissolving. The egg membrane, which is not as durable as the shell, maybe the only thing holding the egg together.
  4. Carefully dump out the vinegar. Put the eggs back in the container and cover them with fresh vinegar. Leave the eggs in the refrigerator for another 24 hours.
  5. Scoop the eggs out again and rinse them carefully. Throw out the eggs where the membranes have broken and are oozing out.
  6. When complete, there will be an egg without a shell. It looks like an egg but is translucent. The membrane will flex when squeezed.

EXPLANATION:

An eggs shell dissolves when submerged in vinegar.

Vinegar contains acetic acid, which breaks apart the solid calcium carbonate crystals that make up the eggshell– into their calcium and carbonate parts.

The calcium ions float free (calcium ions are atoms that are missing electrons), while the carbonate goes to make carbon dioxide.(Those are the bubbles that you see)

Note: The shell dissolved in 24 hours. Although directions say to put the egg in the refrigerator, I forgot to. (It still came out fine) The remainder of the experiment was followed as directed. After a couple of days, you could actually see the yolk floating within the membrane. Both kids and adults liked this one! The egg feels rubbery–but it does ‘splat’ when dropped. Barb


Watch the video: Apologia general science experiment (August 2022).