We are searching data for your request:
Upon completion, a link will appear to access the found materials.
Why are e.g. ducklings, goslings, turkey and chicken chicks (partly) yellow?
What is the chemistry background to this? What compounds from the egg cause this to happen?
What is the evolutionary background to this? How could it help the bird to survive?
While domestication has led to selection of all-white adult birds and thus more common all-yellow babies, why does an all-yellow baby become an all-white adult, in terms of biochemistry?
Wild ducklings, like these baby Mallard ducks, are in fact typically only partly yellow:
Photo by TheBrockenInaGlory via Wikimedia Commons, used under the CC-By-SA 3.0 license.
While I'm no expert, I would guess that the mottled yellow-brown coloring of the juveniles is, at least partially, protective coloration, just like the somewhat similar pattern on the adult female's feathers. While it may appear conspicuous on open water, ducks in their natural habitat will often seek shelter among reeds and other vegetation, where the irregular pattern of light and shadow would create a very effective camouflage for the ducklings.
As for the all-yellow ducklings of domestic ducks, these presumably arose via elimination of the darker parts of the coloring as a result of selective breeding, perhaps as a side effect of artificial selection for the white adult plumage found in many domestic ducks today.
Specifically, according to a recent study of domestic duck genetics, it appears that the all-white plumage of domestic Pekin ducks is caused by a single recessive mutation to the MITF gene, which regulates melanin production. The mutation, when homozygous, causes the normal melanin production pathway in the skin to be almost entirely shut off, so that the adult plumage is pure white regardless of what other plumage color genes the bird may be carrying (a fact apparently known for a long time from cross-breeding experiments, even though the specific mutation behind this effect was not determined until recently).
Apparently, however, the yellow base pigmentation in young ducklings is not affected by the MITF mutation, and thus appears even in individuals homozygous for it. Presumably this is because the yellow color is produced via some other pathway, which is active in young ducks but gets shut off as they develop their adult plumage. The brown pigmentation pattern overlaid on top of it in wild-type ducklings, however, is controlled by MITF, and thus fails to appear in ducklings with two copies of the mutated version of the gene, leaving their juvenile plumage pure yellow.
As far as I can tell, the specific reason why the yellow pigmentation in ducklings is not controlled by the MITF gene still remains unknown. Or, if it is known, my Google search skills were not good enough to find it.
3.6: Punnett Squares
- Contributed by CK-12: Biology Concepts
- Sourced from CK-12 Foundation
What do you get when you cross an apple and an orange?
Though the above fruit may not result, it would be nice to scientifically predict what would result. Predicting the possible genotypes and phenotypes from a genetic cross is often aided by a Punnett square.
Baby poop color: Causes and when to see a doctor
An infant’s poop changes color and consistency during their first few days, weeks, and months of life, and a wide range of colors is normal. Below, learn to recognize unhealthy baby poop and what changes to expect as a baby grows.
In infants, age, diet, and health are the main reasons for changes in stool color. The poop of newborns is almost black, while older infants tend to have yellow or brown poop.
Breastfeeding and formula-feeding can also influence the color of a baby’s stools.
Red or white poop can indicate a health problem. Otherwise, a wide range of colors is to be expected. Anyone who suspects that a baby has diarrhea or constipation should seek medical advice.
Various factors can cause changes in the color of a baby’s stools. Common colors and their causes include:
In newborns younger than 1 week, black is a healthy color for stool. After this time, however, it could indicate a health problem.
During the first 24 hours of life, a newborn will pass meconium. This is thick, black stool. It is made up of cells, amniotic fluid, bile, and mucus ingested while in the womb. Meconium is sterile, so it usually does not smell.
Over the first few days of life, a newborn will continue to pass meconium. The color should gradually change from black to dark green, then yellow.
After 1 week of life, stool should no longer be black. If a black color persists, seek medical advice. It could mean that there is some bleeding in the digestive system.
This is a normal color of poop from a breastfed baby. Their poop tends to be dark yellow
and may have small flecks in it.
These flecks come from breastmilk and are harmless. Poop from breastfed babies is often described as “seedy.” The so-called seeds may resemble curds in cottage cheese but are yellow.
Brown or orange
This is a normal color of poop from a formula-fed baby.
When a baby drinks formula, their poop tends to light brown or orange. It may be slightly darker and firmer than stool from a breastfed baby.
Many babies occasionally have green poop. Some possible causes include:
- slow digestion, usually because the baby has eaten more than usual
- green foods in the diet of the breastfeeding mother
- a cold or stomach bug
- a food allergy or intolerance , either in the baby or the breastfeeding mother
- treatment for jaundice
Some infants’ poop is naturally slightly green. If the baby is putting on weight and seems content, green poop is not necessarily a cause for concern.
This is not a healthy poop color.
Poop is usually red because there is blood in it. Seek medical advice.
The baby may have a health problem, or they may have swallowed a small amount of blood. This could happen if a breastfeeding mother has cracked or bleeding nipples. Another cause of red poop is bleeding from the baby’s bottom.
This is not a healthy color for stool.
White poop is uncommon and could indicate a liver problem.
Jaundice, for example, is highly common in newborns, affecting as many as 80% of these babies in their first few days of life. It usually goes away within the first 2 weeks.
Anyone who suspects that their baby still has jaundice after 14 days should check the color of their poop. Pale or white poop may suggest liver disease. Another sign to look for is yellow pee.
If the baby has white or pale stool, the doctor may test their bilirubin levels. Bilirubin is a compound that helps the body get rid of waste. There are two types of bilirubin, and if levels of one type are too high, it can cause health problems.
Baby poop can also have a variety of textures and other features. Before an infant starts eating solid food, their poop is usually very soft.
Breastfed babies may have quite runny or stringy poop, while formula-fed babies tend to have firmer, but not solid, poop.
Mucus in a baby’s stool is also common and rarely a sign of any health issue. If the baby shows other signs of unusual behavior or illness, however, speak to a doctor. Learn more about mucus in baby poop here.
Dry or hard poop can mean that a baby is not drinking enough fluids, or they may be ill.
After an infant starts to eat solid foods, hard poop can also be a sign of constipation. Babies commonly become constipated when they eat foods that their bodies cannot yet digest properly. Here, find out more about constipation in babies.
Very watery stool can result from diarrhea. A baby with diarrhea may also poop more often than usual or have a high temperature. Diarrhea can cause dehydration, which is potentially serious for infants.
Every baby is different, and some poop more often than others. Many newborns poop after each feeding, though they tend to pass stool less frequently once they reach 6 weeks old. Breastfed babies may only poop once a week. A healthy frequency for formula-fed babies is once per day.
As a baby grows, their poop often changes color. For example, as an infant starts to eat solid foods, what they eat may affect the color of their poop. Undigested food in stool can also cause a change in color.
Unusual colors, such as green, may not signal a health issue. Stool color may vary for a short time, then return to its regular shade.
White, red, or black are the exceptions — these colors can each indicate a health problem.
Also, if a lot of mucus is present or it appears in stool on an ongoing basis, this could signal an illness.
Will the Yellowing Leaves Become Green Again?
In most cases, your yellow leaves aren’t going to bounce back and become green again – that’s the bad news. The good news is that you can easily stop the spread of the yellowing to the plant’s other leaves. A few yellow leaves here and there does not have to be the kiss of death for your plants.
If you notice a few leaves have become yellow, first, pinpoint the problem and address it accordingly. Then prune off the yellow leaves to give your plant a fresh start. You’ll be enjoying luscious green growth in no time!
Why are certain baby (water)fowl yellow? - Biology
Site Hosted by the Department of Molecular & Cellular Biology
Biochemistry basic chemistry, metabolism, enzymes, energy, & catalysis, large molecules, photosynthesis, pH & pKa, clinical correlates of pH, vitamins B12 and Folate, and regulation of carbohydrate metabolism.(en español - no português)
Chemicals & Human Health basic toxicology, lung toxicology, environmental tobacco smoke & lung development, kidneys & metals
Developmental Biology developmental mechanisms
Human Biology DNA forensics, karyotyping, genetics, blood types, reproduction, sexually transmitted diseases (en español)
Immunology, HIV, the ELISA assay, Western blotting analysis and case studies designed for advanced students.
Mendelian Genetics monohybrid cross, dihybrid cross, sex-linked inheritance (en español - in italiano)
Molecular Biology nucleic acids, genetics of prokaryotes, genetics of eukaryotes, recombinant DNA. (en español -in italiano)
All contents copyright © 2001-02-03-04
All rights reserved.
Look under "Activities" for K-8 lesson plans in:
Science & Math
Music & Art
Click here to order our latest book, A Handy Guide to Ancestry and Relationship DNA Tests
I know that a person is 50% related to their mom and 50% related to their dad. My question is whether or not siblings could range from 0-100% related? Is the 50% that people talk about with brothers and sisters just a mean value?
-A high school student from the United Kingdom
You are right. Everyone is more or less 50% related to each of their parents but can be anywhere from 0-100% related to their siblings. But for reasons we will talk about in a bit, it turns out we are all pretty much 50% related to our brothers and sisters too.
Both of these are true because of how DNA is passed from one generation to the next. We get half our DNA from our moms and half from our dads which is why simple biology says we are more or less 50% related to our parents.
The more or less comes from the X and Y chromosomes that come from dad and the mitochondrial DNA that comes from mom. These slightly change the 50% but they do so in a consistent way.
Boys are always related to their dads at a certain percentage and their moms at a different percentage. Same thing with daughters and their moms and dads.
The situation is much more variable with siblings. Theoretically you could be totally unrelated to your sister or share the exact same DNA as your brother. But because we are talking about so much DNA and so many different possible combinations, the percentage usually comes out to about 50%.
Think about it like flipping a coin. Imagine mom is heads and dad is tails. If you flip the coin just twice, then you have a 1 in 4 chance of getting two heads, a 1 in 4 chance of getting two tails and a 2 in 4 (or 1 in 2) chance of getting a head and a tail. You’d have a pretty good shot at being the same as one parent or the other.
But if you flip a coin a thousand times, the odds of getting all heads or all tails is pretty close to zero. Not exactly zero, but very close. Here is what the graph of probabilities looks like for a thousand coin flips:
You can see that 499 heads and 501 tails isn’t that much less likely than 500 of each. Once you get to 450 heads, though, you get down to very low probabilities. And at one or zero heads, you are a whisker above zero.
The same sort of thing is true with our DNA. Because there are so many possible combinations of mom’s and dad’s DNA in each sibling, the siblings all tend to be pretty close to 50% related. Here is what the graph would look like:
Around 50% Related
Our DNA is packaged in 23 pairs of chromosomes. We get one of each pair from mom and one from dad. This is how we get to 46 chromosomes.
It is also why we are 50% related to mom and 50% related to dad. One chromosome from each pair comes from each parent. But it doesn’t work like you might think.
See, the chromosome you get from mom is actually a mix of both chromosomes in the pair. It goes something like this:
When you get this chromosome from mom, it is still all mom DNA. So when it pairs up with the one from dad, you end up with half your DNA from mom and half from dad. The same thing happens with 21 of your other pairs (we’ll deal with the 23 rd pair and a bit of DNA from the mitochondria called mtDNA later).
The way I drew the mixing is just one of an infinite variety of ways the DNA could have mixed. Here are four more:
This sort of recombination is why siblings don’t have to be exactly 50% related. Let’s go through a couple of examples to see why.
Imagine that mom’s chromosomes mix in the way shown below for a brother and a sister:
As you can see, by chance they share no DNA on this chromosome. The brother got the top and bottom half of the blue chromosome and the middle of the red one. By chance, the sister got just the opposite. If this were to happen with the rest of the chromosomes, then by chance they’d share no DNA from mom!
Let’s look at this example:
Now they each got the same DNA from mom and so happen to share all of their DNA on this chromosome. If this were to happen on all of the chromosomes too, then these two would be 100% identical for mom’s DNA.
For the siblings to share all or none of their DNA, the same sort of things would have to happen with dad’s chromosomes too. The odds are very much against the exact same mixing happening on all 46 chromosomes in each of the siblings. So unlikely that I have never seen a report of where such a thing has happened (although something called uniparental disomy can make a child share more DNA with one parent).
What happens in real life is that there are different amounts of mixing that when averaged over the 46 chromosomes comes to about 50%. You can see this is in these two real life examples:
In this picture, we are comparing a sister to two different brothers. It is presented in sort of a weird way because of the way this company is able to look at the DNA but the bottom line is that even though the patterns are very different, each brother shares about the same amount of DNA with their sister. Let’s look at these results in a little more detail.
Wherever part of a chromosome is black, that means the two people share DNA from both parents in this pair of chromosomes. In other words, they happened to get the same chunk of DNA from mom and dad. They are completely identical at this spot.
In the gray parts, they are half identical which means they share DNA from either mom or dad at this spot but got different DNA from the other parent. And if the DNA is white, they got different DNA from both parents.
OK, I know what that is supposed to mean and I’m a little confused. Let me take chromosome 2 from the first set and try to show you what it means.
First, let’s take their chromosome and flip it so it is like the others in the answer so far. Here is what that will look like:
OK, so this is actually four separate chromosomes all being compared at once. The first step is to pull those four out like this:
Now let’s add in mom and dad’s DNA. We will make each one of their chromosomes a different color.
What I have also done is to show one way mom and dad’s DNA might have mixed in this brother and sister to give the result on the left. This isn’t the only way it could happen but it’ll help us understand the results (I hope!). Let’s go through and see how it works.
What I have done is to box in the areas where the brother and sister have half identical DNA on both the 23andMe diagram and my example. Notice the top box that is supposed to match up with the top light blue in the chromosome on the left. (I ignored the little white patch for simplicity.)
Both brother and sister got green from dad in this section but the brother got blue from mom and the sister got red. So they are different at mom’s chromosomes and the same at dad’s. They are half identical.
Same thing with the next box except here they share mom’s red DNA but have different dad’s DNA. Again, they are half identical.
Here is an image where the nonidentical DNA has been boxed:
Let’s look at the uppermost box. Notice that none of the brother’s and sister’s DNA matches up. The brother got blue from mom and yellow from dad and the sister got red from mom and green from dad. They are nonidentical here.
Finally let’s look at the areas where their DNA is identical.
Notice how in the uppermost box, the brother and the sister both got red from mom and yellow from dad. They are identical at this pair of chromosomes.
OK, now maybe the data below is easier to understand!
The key point here is that even though the two brothers have a very different pattern when compared to their sister, they share about the same amount of DNA with her.
If you look at the box in each figure, you’ll see how many gigabases (or billions of bases of DNA) the two share. This sister shares 1.98 with one brother and 1.93 with the other. Nearly identical amounts!
Again, this is because there are so many different combinations that it all sort of balances out in the end. Kind of like doing thousands of coin flips. And these results are pretty typical.
So for the first 22 pairs of chromosomes which represent most of our DNA, two siblings are going to share right around half of their DNA. Not exactly half, but pretty close.
Since these chromosomes make up the lion share of our DNA, we could be done here. But for completeness sake, we’ll include a short section on the 23 rd pair and the DNA from the mitochondria. Different siblings share a definite amount of each of these.
X, Y, and mtDNA
We’ll start with the easy one first, the mitochondrial (mtDNA). Since mtDNA is only passed from mother to child, all siblings share the same amount of this DNA.
This DNA isn’t really that significant in terms of percentages. The mtDNA only makes up a little less that 0.0003% of your total DNA so this isn’t going to move the percentage too far one way or the other.
The other important differences are the X that dads pass to their daughters and the Y’s they pass to their sons. Because these don’t recombine, sisters pretty much share 100% of their X chromosomes and brothers share 100% of their Y chromosomes with their dads.
In the F2 generation, only 1 of the 4 boxes produced green peas. In other words, 25% of the offspring had green peas. This number tells you the probability, or likelihood, that an offspring will produce green or yellow peas.
We can use the probability to predict how many offspring are likely to have certain phenotype when mating plants or animals with different traits. Just take the probability of a phenotype and multiply it by the total number of offspring. Let's imagine there were 160 total offspring in Mendel's F2 generation. How many peas are likely to be green?
25% green peas x 160 total offspring = 40 green pea offspring
View illustrations, full-color photos, and video footage of each species. Learn more about their behavior, migration patterns, and the sounds they make. Study flock patterns and wing characteristics. Our Waterfowl ID guide has everything you need to recognize ducks, swans and geese in the field or on the fly!
Identification is Important
Identifying waterfowl gives many hours of enjoyment to millions of people. This guide will help you recognize birds on the wing—it emphasizes their fall and winter plumage patterns as well as size, shape, and flight characteristics. It does not include local names.
Recognizing the species of ducks and geese can be rewarding to bird watchers and hunters—and the ducks.
Hunters can contribute to their own sport by not firing at those species that are either protected or scarce, and needed as breeders to restore the flocks. It can add to their daily limit when extra birds of certain species can be taken legally, hunters who know their ducks on the wing come out ahead.
Most ducks shed their body feathers twice each year. Nearly all drakes lose their bright plumage after mating, and for a few weeks resemble females. This hen-like appearance is called the eclipse plumage. The return to breeding coloration varies in species and individuals of each species. Blue-winged teal and shovelers may retain the eclipse plumage until well into the winter.
Wing feathers are shed only once a year wing colors are always the same.
Differences in size, shape, plumage patterns and colors, wing beat, flocking behavior, voice, and habitat—all help to distinguish one species from another.
Flock maneuvers in the air are clues. Mallards, pintails, and wigeon form loose groups teal and shovelers flash by in small, compact bunches at a distance, canvasbacks shift from waving lines to temporary V's.
Closer up, individual silhouettes are important. Variations of head shapes and sizes, lengths of wings and tails, and fat bodies or slim can be seen.
Within shotgun range, color areas can be important. Light conditions might make them look different, but their size and location are positive keys. The sound of their wings can help as much as their calls. Flying goldeneyes make a whistling sound wood ducks move with a swish canvasbacks make a steady rushing sound. Not all ducks quack many whistle, squeal, or grunt.
Although not a hard and fast rule, different species tend to use different types of habitat. Puddle ducks like shallow marshes and creeks while divers prefer larger, deeper, and more open waters.
Explore the various species of North American waterfowl divided into these five categories.
Dabbling ducks are typically birds of fresh, shallow marshes and rivers rather than of large lakes and bays. They are good divers, but usually feed by dabbling or tipping rather than submerging.
The speculum, or colored wing patch, Is generally irrldescent and bright, and often a telltale field mark.
Any duck feeding In croplands will likely be a dabbling duck, for most of this group are sure-footed and can walk and run well on land. Their diet Is mostly vegetable, and grain-fed mallards or plntails or acorn-fattened wood ducks are highly regarded as food.
Diving ducks frequent the larger, deeper lakes and rivers, and coastal bays and inlets.
The colored wing patches of these birds lack the brilliance of the speculums of puddle ducks. Since many of them have short tails, their huge, paddle feet may be used as rudders in flight, and are often visible on flying birds. When launching into flight, most of this group patter along the water before becoming airborne.
They feed by diving, often to considerable depths. To escape danger, they can travel great distances underwater, emerging only enough to show their head before submerging again.
Their diets of fish, shellfish, mollusks, and aquatic plants make then second choice, as a group, for sportsmen. Canvasbacks and redheads fattened on eel grass or wild celery are notable exceptions.
Since their wings are smaller in proportion to the size and weight of their bodies, they have a more rapid wingbeat than puddle ducks
Swans and geese are the largest members of the duck family, and swans are among the largest of all flying birds. Swans are larger in size and have proportionally larger feet and longer necks than geese, which are closely related. The plumage of both sexes of swans and geese are similar, although males in both groups are generally larger than females.
Swans eat mostly plant materials, which they find in the water and on land. They do most of their foraging in the water, by tipping up or dabbling, much like dabbling ducks. They do occasionally eat small aquatic animals. Swans form tight pair bonds that often last for life. Bonded pairs stay together year-round.
Geese have shorter necks and longer legs than swans. They spend much more time on land than swans, and they graze on grasses and other land plants, in addition to eating some aquatic plants. Geese mate for life and both parents care for the young.
Watch Out for Look-alikes!
Some kinds of geese and swans look very similar to each other, and also look similar to the highly endangered whooping crane, so take care to make positive identification of your target when hunting. Review the individual species pages for more details.
This Web-based guide is adapted from: Hines, Robert W. Ducks at a distance: A waterfowl identification guide.
Feeding a premature baby
Your specialist team will be working towards the day you take your baby home. Often there will be a transition stage between being on a special neonatal unit and going home. During this stage you will be the main carer for your baby, but in a hospital environment where there is support in case of any problems. This can help build up your confidence and skill in looking after your newborn baby. Before you go home, your specialist team will make sure you know how to feed your baby, how to give any medicines or treatment still required, when you should ask for medical help and how to access it.
Use a giant cell—a de-shelled chicken egg—to explore the comings and goings of cellular substances.
Tools and Materials
- Several chicken eggs
- Large container, such as a wash basin or large bowl
- Pencil and notepaper (or similar) for recording information
- Several substances in which to soak or bury the de-shelled eggs, such as distilled water, dry salt or saltwater solutions, colored water, corn syrup, rubbing alcohol, cornstarch, or baking soda
- Containers to hold the soaking eggs
- Plastic wrap (not shown)
- Masking tape and marker for labeling containers
- Optional: nitrile or latex gloves for handling eggs, glass jars or other small objects to hold down floating eggs
- De-shell the eggs by placing them in a large container so that they touch as little as possible. Add vinegar to cover the eggs (see photo below), and cover the container. Allow the eggs to sit for 24 to 48 hours at room temperature. Note: Changing out the vinegar halfway through and replacing it with fresh vinegar will speed up the process.
To Do and Notice
Use a scale to find the mass of each de-shelled egg before treatment. Record the result on notepaper.
Place one egg in a labeled container and cover it with your chosen treatment. (If the egg floats, you may use something to hold it down, such as a glass jar see photo below.) Repeat for each of the remaining treatments. Be sure to set aside an untreated "control" egg. After taking its mass, cover the control egg with plastic wrap, and set it in a container alongside the treatment eggs.
Place the treatment containers somewhere they can sit for at least a day at room temperature. Observe any changes that occur in the eggs during the first hour or so of soaking and record your observations.
Observe any changes in the color, size, or shape of your experimental eggs. Record your observations. Then, gently remove your sample eggs from their treatments to measure and record the mass of each one (see photo below). Remove the plastic wrap from the control egg and measure its mass too. Calculate the percentage change in mass for each egg by dividing the final mass by the starting mass and multiplying by one hundred percent.
In a separate bowl, carefully dissect the egg by piercing the membrane. Record your observations.
How did each egg change? Did its mass increase or decrease? Do you see anything in common with the treatments that enlarged the eggs? Which treatments made the eggs shrink, and which did not?
What’s Going On?
In general, the most dramatic changes to the mass, color, and shape of the eggs will occur within the first 24 hours of the experiment. Eggs submerged in corn syrup will have lost considerable mass and have the appearance of flabby sacks. Eggs soaked in distilled water will gain mass and appear dramatically swollen. Eggs in dilute salt solutions will gain mass, and even those in very concentrated solutions might gain mass. Eggs buried in salt or other dry media should lose mass.
The de-shelled eggs serve as good models of human cells. After the eggshell is removed, a thin membrane (actually, two membranes held tightly together) remains. This membrane, like those in human cells, is selectively permeable, allowing certain substances to pass through while blocking others.
Substances that can pass easily through the membrane of the egg will follow the principles of diffusion. They will move through the membrane from the side where they are at a higher concentration to the side where they are at a lower concentration (click to enlarge the diagram below). This movement will continue until the concentration on both sides is the same. While random molecular motion will cause individual molecules to continue moving back and forth across the membrane, the overall concentration on each side will remain in equilibrium, with equal concentrations on both sides.
The egg’s membrane is permeable to water. Movement of a solvent (such as water) across a semipermeable membrane from a less concentrated solution to a more concentrated one is called osmosis. When an egg is soaked in a solution that has a higher solute concentration (the relative amount of dissolved stuff) than the solute concentration inside the egg, water moves out of the egg and into the solution (see diagram below).
As a result, the egg loses mass and ends up looking deflated. An egg naturally has a lot of stuff inside, so the outside solution has to be very concentrated for this to happen. That’s the case when an egg is treated with corn syrup or buried in salt. By contrast, when an egg is treated with distilled water, or a dilute salt solution, the solute concentration is higher inside the egg than out, so the water moves into the egg, increasing its mass. It may be easier to think about osmosis in terms of water concentration rather than solute concentration. If the solute concentration is high, then the water concentration will be low by comparison.
Rubbing, or isopropyl, alcohol is at least 70% alcohol and therefore less than 30% water. This should cause water to move from the egg into the solution, and the egg should lose mass. In addition, the egg may appear white and rubbery. Alcohol that diffuses into the egg can denature the proteins, unraveling their three-dimensional structure and causing them to coagulate or join together. Egg proteins turn from translucent to white when they are denatured. In cooking, temperature is used to denature these proteins, but you may have noticed that alcohol has also "cooked" the egg and caused it to look hard-boiled.
The plasma membranes of your cells behave much like those of the egg. All of the trillions of cells in your body are like busy seaports with materials coming in and going out. Water, oxygen, and nutrients must pass through the plasma membrane into your cells, and wastes must leave. When the concentration of oxygen is higher in your lungs than it is in your blood, for example, the oxygen diffuses into red blood cells through capillary walls. Your flowing blood then transports that oxygen to your tissues. From there, the oxygen diffuses into other cells to be used in cellular respiration. Through a similar process, water in the stomach moves into the bloodstream and is then carried to the cells, where it supports a variety of essential bodily functions.
Predict what would happen if you placed the shrunken eggs in plain water overnight. Do the experiment and explain your results.
In this activity, not only can you measure how much material moved into or out of a treated egg, but you can also chemically determine whether molecules moved across the membrane. If you break the egg into a dish, or save some of the soaking solution, you can use chemical tests to see what’s there. For example, you can use Benedict’s solution to test for simple sugars, iodine to test for starch, or Biuret solution to determine whether or not protein exited the egg as it soaked.
When using this activity with large groups of students or multiple classes, have each group apply only one treatment, and then analyze the data collected from all groups. Having each small group design an experiment with one egg will allow you to do the activity with fewer eggs per class, and collecting several sets of data will enable students to identify any outliers.
This Snack is an excellent activity for introducing diffusion, osmosis, and the semipermeability of membranes and allows learners to engage in the NGSS Science and Engineering Practices. By collecting data from multiple classes, you can facilitate a discussion about what and how much data is necessary to count as evidence. Students can also use the evidence about what and how much material moves into and out of the egg to formulate a revisable model about how osmosis occurs and what might prevent or allow molecules to move through membranes. By incorporating related activities, such as the Cellular Soap Opera Snack, students can form a more complete conceptual model of the cell membrane and how molecules move along concentration gradients.
Note that it’s also important to discuss the idea that models such as this one have limitations. There are structural differences between the membranes of chicken eggs and human cells that result in differences in permeability. Some of the molecules that pass through the egg’s membrane in this activity would not pass through a human cell membrane because of their size (such as cornstarch) or their charge (such as Na + and Cl - from the salt).
Ducks such as harlequins, which live in areas noted for food scarcity, have adaptations designed to help them stay alive. Male harlequins leave the nest earlier than most male ducks do, reducing competition for food resources. Harlequins also lay fewer eggs than other duck species, making it easier for mother ducks to keep their offspring alive.
Mallard ducks have various behavioral adaptations that help protect their young. When a nest is threatened, female mallards swim or fly away from the nest, often acting injured. The predator, assuming the duck an easy kill on account of its “injury,” follows the mother away from the nest. Baby ducks remain silent in such instances, a safety adaptation.