A Little Bit More
Eggs are very much a part of our everyday lives, yet we don't pay much attention to their wonderful construction. If most people were asked enough leading questions, they would eventually acknowledge that the developing embryo must acquire oxygen through the eggshell while inside the egg; no doubt we all know this intuitively but simply haven't thought it through.
The eggshell's outer layer, the cuticle, consists of two membranes. The cuticle is an important first-line barrier to invasion by harmful organisms. These two extremely thin, transparent membranes cover the spongy egg shell but are permeable to gases. If an egg is hard-boiled, these outer membranes are damaged, which is why hard-boiled eggs don't last as long as fresh eggs in our refrigerators.
The second layer is the shell itself. The shell is made up mostly of calcium in the form of carbonate of lime. The eggshell's pores are identifiable as minute indentations on the surface of the shell and are connected to very fine air channels that run straight through the shell. These channels are large enough to allow air to reach the embryo but small enough to slow the evaporation of moisture from within, and act as a second line of defense to prevent the infiltration of organisms from without. Even though the cuticle and air channels help reduce water loss by the egg, the humidity of the air surrounding an egg plays a role in the survival and development of the chick. A parent bird's body provides enough moisture to keep the eggs from drying out; an artificial incubator must always include a water source so that the air is not only warm, but moist.
The third layer in the "egg sandwich" is the very thin double layer called the shell membrane. This layer adds greatly to the overall strength of the main shell until it is pierced by the chick's bill, when the chick pokes its bill into the air cell shortly before hatching. The double-layered shell membrane is split at the blunt end of the egg, with one layer remaining tight to the egg shell while the other slowly pulls farther away from the shell as the air cell enlarges during incubation. It is the shell membrane that sometimes causes problems when you try to peel a hard-boiled egg!
Activities
Science - Egg Close-up
Objectives: A close look at what an egg really looks like
Materials: egg, pan of water, and heating unit
Take an egg out of your refrigerator and look closely (you can use a magnifying glass if you have one) to see the many holes in the egg’s shell. Although the holes are very small, they cover the entire egg’s surface and allow enough air into and out of the egg to provide the developing chick with oxygen to survive.
Place your egg in a pan of water on the stove and bring it to a boil. As the egg heats in the water, before it actually boils, watch for the air bubbles forced out of the egg through the eggshell holes as it heats. Boil the egg for about 6 minutes until it’s hardboiled.
Once the egg is hardboiled and cool, gently crack the eggshell and remove the shell in as large a piece as possible. Now that the eggshell is removed, you can see the shape of the egg itself and should see that it isn’t the same shape (exactly) as the eggshell. An air chamber in the blunter end of the egg takes up some space so the egg’s fluid doesn’t fill the entire eggshell. The air chamber is where the developing chick takes its first breath of air.
Key Concepts
Growth and Development, Structures and Functions
Questions
Do you have a question for a naturalist? Go ahead and ask!
It's easy -- just fill out this form, submit your question and you'll receive an answer shortly.
Posted by Dane Dreblow on May 22, 2007 at 10:12 PM
Q: I am having an egg drop competition and I want to know what kind of egg would be the best- yuo know, the one that is hardest to break on impact- can you tell me what kind you would recommend and maybe where to get one?
A: Well, I certainly credit you for going one step farther to find out how to set this up to your advantage! We have an egg drop competition here in New York State each year too but I'm not familiar with the rules and regulations for this activity. It would seem to me that everyone would need to have the same kind of egg, but maybe not. So...which one would be best?
Although it might seem that one kind of bird egg would be more durable than another, there's a structural requirement that all bird eggs need to follow. Each kind of bird must lay an egg that is strong enough so when it is being incubated, the parent doesn't crush it. On the other hand, each kind of egg must have an eggshell that is thin enough so the baby inside can escape. These two requirements seem to be at odds with each other and so a "compromise" is reached - eggshell just strong enough to support parent but weak enough to allow the baby to escape. With this in mind then, although an Ostrich egg may seem extremely strong, it's a larger egg and its weight, when dropped would probably make it just as vulnerable to cracking as that of a tiny sparrow egg. In other words, I don't think the kind of egg is very important.
If I were doing this, I think I'd look for an egg from a bird that hasn't simply been bred for egg production - I'd look for an "all around kind of " bird. I'd get an egg from a free range chicken figuring that it's eggs are more "typical" of all bird eggs and would be more likely to hold up when dropped. Typical store bought eggs are from chickens that were bred for exclusive egg production and I can easily believe that their egg shells are not all that well constructed. Hope this makes sense. Best of luck to you with your egg drop.
Posted by Judy Mackles on August 04, 2006 at 08:28 PM
Q: My daughter has wild mallard ducks that swim in her pond in South La. They are losing their feathers and she is concerned. Do you know what can be causing this?
A: Ducks molt in late summer each year. They lose their old feathers that are quite worn out by now and grow new ones. The ducks lose their flight feathers pretty much all at one time and are flightless for a while. At these times, these birds congregate in places that are especially safe so they can avoid predators until new flight feathers grow back and they can fly again. Not all birds lose all of their flight feathers at once but all birds do molt. Hope this helps.
Posted by Morgan Sthele on June 20, 2006 at 01:47 PM
Q: How do you know if a refrigerated egg is fertile or not to hatch as a chick?
A: You can't tell by looking but you may be able to figure it out if you know where the egg came from. For most large-egg producers, the hens are kept in cages and no males are ever present; therefore, no fertile eggs. I'm guessing that most/all typical grocery store eggs are non-fertile. If, however, your eggs came from a farmer or "organic-oriented" store, there's much more likelihood that a rooster was mixed with the hens so eggs MAY be fertile. To be sure about the eggs, I'd go to the source and ask. Best of luck to you.
Posted by greta haines on May 17, 2006 at 12:04 PM
Q: I have heard that female black/white ducks are sterile is that true? I have 13 ducks 2 are males the rest are females they have about 4 nests going and I don't know which are fertile and which aren't the males seem to have there share of each female. Will I have to candle each egg I don't what rotten eggs left everywhere, Help!
A: That's a new one on me - I don't think it's true at all that black and white ducks are sterile! My guess is that your duck eggs are probably fertile and the eggs in the nests are likely to hatch. Your duck eggs should hatch in 26-30 days after incubation has started. If after this time the eggs are still unhatched, you can then pitch them - they shouldn't be smelly yet. You can candle the eggs but I'd be hesitant to disturb the nest. Why not just wait and see - I predict that you're going to have lots more ducks.
Posted by Ashley Parker on April 26, 2006 at 12:52 PM
Q: Can you hatch a chicken from an egg in your refrigerator?
A: Yes you can but only if your egg is fertile to begin with. Most of the eggs sold in stores come from large chicken farms where the hens are maintained totally separate from males. No males, no fertile eggs! If you get eggs from chickens that are free range, then there is a good, or at least better, chance that you'll have fertile eggs. An egg can be quite cool BEFORE incubation starts but once it has started, you'd need to maintain a reasonably constant warm temperature. Hope this helps.
Posted by David Smith on April 20, 2006 at 09:11 PM
Q: can a bird egg rotate clockwise to hatch, even if it's head is under right wing? It seems to me that it would be almost impossible for a bird embryo to hatch clockwish because of the head position. Can you help me?
A: Oh my, I need to do a bit of research to give you an answer. I'll get back to you ASAP.
Posted by David Smith on April 20, 2006 at 09:11 PM
Q: can a bird egg rotate clockwise to hatch, even if it's head is under right wing? It seems to me that it would be almost impossible for a bird embryo to hatch clockwish because of the head position. Can you help me?
A: Boy, you made me work on this one!! I spoke with someone at Cornell University's Poultry Science to get some answers.
According to my source, birds do not rotate within the egg under their own power but only turn in the egg when the egg is turned by the mother/father or by hand. Also, although the head is turned back toward its body, its bill is not "under" the wing.
So it seems that clockwise or counterclockwise motion within the egg is not an issue for hatching success. However my source did say that if a chick does end up with its head away from the blunt end of the egg (where the air cell is located, it will not survive.
I sure learned a lot. Thanks for your questions and I hope this helps.
Posted by Jake Ricks on March 27, 2006 at 08:38 PM
Q: I have candeled my eggs and my large fowl eggs are easy but my bantam eggs all look unfertile. Are bantam eggs harder or do I need to wait longer to candel them?
A: I'm certainly no expert at candeling eggs but I wonder if the problem is the eggshell pigment of the bantam eggs? As I recall, bantam eggs shells are colored (not white) and this may be making it a wee bit more difficult to candle. You're correct in thinking that you may be too early to candle the eggs as initially, the development is much too small to see. Give your eggs a few more days and try again. If you think that the egg shell pigment is the problem, maybe using a brighter light will do the trick. I have candled crane eggs so I do know that even their eggs (these have thick shells with some color and blotching) can be candled so I would assume it's just a matter of getting it right so you can see well into your bantam eggs. Best of luck.
Posted by anita puppe on September 16, 2005 at 09:04 PM
Q: 1. what came first, the chicken or the egg?
A: This is an age-old question that is usually looked at as having no answer! However, if we look at this question from a scientific viewpoint, then the egg came first. The parents of the very first chicken were almost chickens but not quite. Their baby chicken (the egg) was the result of the combination of the father and mother's genetic material that resulted in the very first chicken.
Thanks for your question.
Posted by Shelby Colson on September 04, 2005 at 08:56 PM
Q: I found two eggs in my garage with no nest they were just sitting next to a shelf. Can you tell me what kind of eggs these are?
A: Identifying eggs is especially difficult and one needs to consider nest construction, habitat, size of eggs, number of eggs,color/pattern of eggs, and geographic location to make an informed decision. But...with just what you've shared, it would seem that you probably have a couple of House Sparrow eggs. It's difficult to say why these eggs were not in a nest. Finding an egg that is in an unusual location is not so uncommon, but finding two is a bit surprising. Take a look at this site I've included and scroll down to the House Sparrow eggs shown to see if they look like your eggs. www.sialis.org
Hope this helps you out. Thanks for asking.
Posted by Stef Shubert on August 21, 2005 at 08:24 PM
Q: how does a drake fertilize an egg?
A: Bird eggs are fertilized while still inside the female, internal fertilization, and BEFORE the shell is formed. It's a bit confusing when you realize that fish and amphibians do fertilize eggs AFTER they have been laid but the reptiles, birds, and mammals all have internal fertilization.
Thanks for asking.
Posted by Russell French on August 05, 2005 at 05:41 PM
Q: do female ducks lay eggs when they are not fertilized by a male duck?
A: They sure do. Most of the chicken eggs you buy at the store are unfertilized - the hens are never with any roosters but they lay eggs anyway. A female duck that is not with a male in the spring will also lay eggs even though her eggs are not fertilized. Domesticated ducks and chickens are much more "programmed" to lay eggs, regardless of other factors, than are wild ducks and chickens so you may find a difference if you're talking about domestic ducks rather than wild ones. Thanks for your question.
Posted by kim koh on July 14, 2005 at 05:01 AM
Q: when a chick hatches from an egg , the egg yolk and egg white are no longer there.what do you think has happened to them ?
A: Most of the egg white and the yolk are absorbed by the chick during its development. The egg white is basically water so any moisture the chick needs is available as it grows. A wee bit is lost through the shell too. If you have seen a chick hatch, you'll notice that it is wet! Still some of the egg white around the chick.
The egg yolk, on the other hand, is food (energy) for the developing chick. Just before the chick hatches the yolk, which is now quite small at this point, is pulled up into its body at the "belly button". The first day or so after a chick is hatched, it really doesn't need food since it still has the last of the yolk in its body, still providing food. So, by the time a chick hatches, the egg white and egg yolk are basically gone (no wonder you asked!).
Thanks for your thoughtful question.
Posted by Bridget on May 12, 2005 at 01:17 PM
Q: At my office, a Mallard Duck (I think) has made a nest under a bush just next to my parking space. I have been watching her sit on her eggs since the last week of March. It was still pretty cold then, so she rarely left them, except when startled by me getting into and out of my car. Now she only leaves them to eat, etc. and doesn't leave when I walk to my car. I am just wondering if the eggs are going to hatch at all because it's been much longer than 28 days when I first saw the eggs. Will she still sit on dead eggs? Thanks.
A: Bridget:
Thanks for describing the situation so well. A couple of questions though:
Is there a male on the scene? An "unattached" female may lay a clutch of eggs even if she has no mate. This of course would lead to clutch failure.
Did you begin your incubation day count from when the last egg was laid? Incubation starts the first day after the full clutch is laid. This ensures the chicks will all hatch at the same time.
The coolness of the weather shouldn't matter in this situation unless the eggs temperature was allowed to drop to near freezing for an extended period of time.
If there is a male present and she's been incubating for more than 25 days, then it's likely this nesting was a failure.
I hope this helps.
Posted by Kathryn Trout on May 07, 2005 at 06:46 PM
Q: I know this sounds like a silly question..so dont laugh...but how exactly does an eggshell form inside its mother.
A: Kathryn: without getting too deep into the physiology of the subject, suffice it to say that after an uncalcified egg is formed in the bird's uterus it enters the oviduct. At this point it is yolk and albumen. The yolk is the yellow part of the egg and it is surrounded by the albumen, or white part of the egg.
The shell membranes are then deposited on the outside of the albumen in the
isthmus region of the oviduct.
Calcification begins at the junction of the
isthmus and the shell gland in the tubular shell gland region of the
isthmus. Hen's eggs spend about 15 to 20 minutes in the region during
formation.
Posted by Lillie on May 04, 2005 at 12:57 PM
Q: I found an abandond MALLARD DUCK egg and I don't know what to do. I love animals and can't stan to see it die. What should I do??? Can you please help me I'm just a young lady who dosen't want this bird to die and have no idea what to do. Thanks - Lillie
A: Lillie, Thank you for your concern about the Mallard egg you found. Unfortunately, your experience is not uncommon. Mallards are notorious for "dumping" eggs before they have a nest. Especially young birds who have never nested before.
It was not meant to be for this egg to ever hatch and the chick to be part of a brood.
Try calling your local nature center or humane society to find out if anyone in your area takes eggs like this. There is an outside chance that someone in your area has the necessary permits to raise and release wildlife. If so, that person will have dealt with the same problem you have. Good luck to you.
Posted by val williams on May 03, 2005 at 11:25 AM
Q: HI. We are in the process of hatching chicken eggs and ducklings in a reliable incubator in a 5th grade classroom. We weighed the eggs before we set them and again today, after a week. The eggs that we have determined to be fertile have lost between 2 - 3 grams of wieght. Is this normal? And what would the explanation behind it be?
A: Val, this is a good observation. Yes, I think weight loss like what you describe would be normal. Everything a developing chick embryo needs to grow must be present and available to the embryo at the time the egg is laid, except oxygen and water vapor (which pass through tiny pores in the shell into the egg as the embryo develops). Most of this food is in the yolk. A fast-growing chick embryo uses up this food supply, and produces waste products. Some of these waste products stay inside the egg until it hatches, but others leave the egg through those pores I mentioned. These include carbon dioxide and water vapor. Both these gases have mass, and probably account for the weight loss you have observed.
Posted by Chris Reynolds on April 27, 2005 at 04:02 AM
Q:
i have been using a candler to see if my eggs are fertile or not, but i really dont know what im looking for,
A: You're looking to see if there has been any embryonic development within the egg. It takes a few days before there is enough development to see but you should be able to see a "spider web" of blood vessels within the shell surrounding the yolk. If nothing is happening, then the egg is probably infertile. I found an online site that talks about making a candler and also what to look for so hope this helps you out. This site also has some links that should help too. Take a look at: www.ehow.com
Good luck to you
Posted by jane on April 22, 2005 at 12:20 PM
Q: To prevent osteoporosis, calcium needs to be consumed. Can calcium present in the egg shell be used as a supplement in our diet?
A: Excellent question, but I don't have an answer! Whether we have adequate calcium in our diet to prevent osteoporosis or not hindges on how we obtain it and then once obtained, is it bio-available. There are some products that may have lots of calcium (good source of calcium)in them but if we can't assimilate it (if it's not bio-available)into our bodies, it's worthless as a calcium source. Humans are able to obtain calcium from some sources but not others and this is why it isn't enough to simply ingest calcium, one must ingest bio-available calcium.
The medical community or nutritional community would be much better able to address your question about eggshell bio-availability, although I'm not sure how you plan on getting those eggshells into someone. Are you thinking of grinding up eggshells? Again though, ingesting the eggshells is only the first step, your body must then be able to assimilate that calcium to have it provide any benefit and I'm not sure that eggshells ARE bio-available.
Sorry I haven't answered your question but I hope it provides you with a bit more information and helps you ask someone who can.
Posted by Melinda Grimes on April 10, 2005 at 09:57 AM
Q: How does the eggshell form inside the chickens body? p.s. the reason i'm asking this is because i'm doing this project for science fair.I'm also bringing my pet chicken Patches.
A: The eggshell is produced in the uterus of a bird. The shell of a typical chicken egg (chickens have been studied the most) is made up of about 94% calcium carbonate and most of this comes from food the hen has eaten although some also comes from stored calcium stored in the large bones of its body. One researcher found that about 11% of the total egg was mineral.
Hope this helps.
Posted by Annonmanous on March 27, 2005 at 01:01 PM
Q: I found an egg in my garden and cannot tell whether it is a bird or duck egg, how can i tell the difference? It is approximatley 6cm in height!...Also, if it has been left outside all night will it definately be dead?
A: Take a look at Helen Fitch's question/answer in the unit's Q&A (www.enaturalist.org so you'll better understand about the egg being left untended outside.
From the size of your egg, it sounds as though it could be a duck or even chicken egg but it's very difficult to identify an egg without something to compare it to. You might want to get an egg from the refrigerator and compare it with your "unknown egg" and see how they compare. Duck eggs are often a bit larger than chicken eggs and are also a little more oblong. If you have a way to incubate the egg you may even be able get it to hatch.
Keep in mind that it is common for ducks (maybe chickens too) to drop a few eggs here and there before they establish a nest. If you've had some ducks around your area lately, I'd guess your egg is a duck egg. Good luck.
Posted by Helen Fitch on March 26, 2005 at 09:38 PM
Q: If a hen lays an egg a day for 13 day- how does she care for them for the 13 days. how does she care for them until she is ready to incubate them?
A: A chicken's egg can remain in a nest for days, as you've already noted, without any outside heat and stay alive. A hen gives her first 12 eggs (this number varies) no care at all until number 13 is laid and then she begins incubation. Once the hen decides to incubate (we're not sure exactly what tells her she now has "enough" eggs) and the embryo starts developing,however, the egg must remain relatively warm or it will not continue development and will die. This arrangement allows all of the chicks to hatch at the same time rather than having the first chick hatch 13 days, for example, ahead of the last chick - pretty neat!
Posted by Anonymous on March 20, 2005 at 08:15 PM
Q: how long dose it take a egg to hatch
A: That all depends on the kind of egg you're talking about. Chickens take about 21 days, Mallard Ducks take about 28 days, Ruby-throated Hummingbirds take about 13 days, and the Royal Albatross takes 84 days - quite a bit of variation.
Posted by Marilu on March 13, 2005 at 05:11 PM
Q: If you float an egg in warm water and it floats is it fertile? Or if you try and float an egg in warm water and
it sinks is it a dud, or is it the other way around?
CONFUSED!
Marilu
A: If you float a fresh egg in freshwater, it will sink, whether it's fertile or not, because it is denser than water. The only difference between a fertile and an infertile egg is one tiny sperm cell. However, it would seem to me that as the embryo developed within the egg during incubation, the egg would lose some water and would be less dense over time and just might float - I've never tried this however. But testing recently laid eggs to determine their fertility status won't work with the float technique.
Posted by Dawn on February 01, 2005 at 07:47 PM
Q: Why are eggs that we eat not fertilized?
A: The answer is quite simple - the chickens that produce most of the eggs we buy are kept in cages that are female only, no males allowed.
Posted by analeis on October 30, 2004 at 09:02 PM
Q: I have some more questions on egg shells. How does the calcium carbonate get into the eggshell? Is it different between organic eggs, free range eggs and commercial eggs? which one would have more calcium carbonate in the egg shell? During the making of the egg, in which process is calcium carbonate absorbed into the eggshell?
thanks so much!
A: Let's take your questions in order:
1.) How does the calcium carbonate get into the eggshell?
The calcium in the shell comes partly from the feed, which for a laying hen
should be 3 grams per day and partly from the bones, which act as a
reservoir. Adult female birds store calcium in the spongy calcified
material at the center of the bones. The transporting mechanism is the
blood.
The carbonate in the shell comes from bicarbonate ions in the blood or, more
likely, from carbon dioxide in the ovarian tissue.
A captive chicken gets the calcium from the packaged feed, a free range
chicken gets it from the soil, seed, insects, etc. that it eats.
2.) Is it different between organic eggs, free range eggs and commercial
eggs?
No, it is not.
3.) Which one would have more calcium carbonate in the egg shell?
Neither, it would be the same. Shell strength depends partly on genetic
factors. In a thorough review of genetic studies, Hunton (1982) concluded
that 50% or less of the variation in egg shell quality is genetic in origin.
It is therefore possible to control egg shell quality to some extent by
breeding.
There is evidence that insecticides or fungicides in the diets of laying
birds can lead to the thinning of their egg shells.
4.). During the making of the egg, in which process is calcium carbonate
absorbed into the eggshell?
The shell membranes are deposited on the outside of the albumen in the
isthmus region of the oviduct. Calcification begins at the junction of the
isthmus and the shell gland in the tubular shell gland region of the
isthmus. Hen's eggs spend about 15 to 20 minutes in the region during
formation.
In birds eggs, 3.9 percent of the dry weight of an egg is made up of calcium
carbonate. Of just the egg shell itself, 97 percent of it is calcium
carbonate. This calcium comes from the mineral calcite that the bird
absorbs through its diet.
Posted by Hayley on October 04, 2004 at 08:34 PM
Q: When a farmer's collecting eggs, how does he know which ones to hatch, and which ones to sell?
A: There are several answers to your very good question. The modern farmer does not expose his/her hens (females) to the rooster (male) if he/she intends to sell the eggs for people to eat. Also, the modern farmer that wants to hatch eggs will breed the hens with the rooster then collects all the fertilized eggs. These eggs go into an "incubator" for hatching.
A traditional farmer will keep the rooster with the hens and only collect the eggs he/she wants to sell. The hen incubates the remaining eggs. The eggs sold to people will then be fertilized, but not incubated. No fertilized eggs are sold in stores. If you buy fertilized eggs for eating you're buying them directly from the farm.
Posted by moose on August 25, 2004 at 05:57 PM
Q: I have some questions on egg shells i hope maybe you could help me with. thanks for any help.
1.How is an egg shell formed?
2.How long dose it take to get hard?
3.Is it hard when it comes out?
thanks again
moose
A: The eggshell is produced by the uterus of the bird. The mineral involved is mostly calcium carbonate that the female gets from her diet (about 2/3), but the rest (1/3) is removed from her bones.
The shell quickly hardens (within minutes) as it is being laid down around the egg yolk and egg white (albumin). This takes place within the female's body.
Yes, the egg is fully developed BEFORE it is laid.
Posted by Evelyn on April 11, 2004 at 02:19 PM
Q: Can you see the embryo on a barely laid egg from a female duck?
A: It takes several days before the embryo is large enough to been seen. I assume you know about candeling an egg (shining a light through the egg so you can see the silhouette of the embryo)and have been looking to see if your egg is fertile and a duckling is growing inside. If you are incubating the egg artifically, you can easily candle the egg daily (egg should be turned a couple of times daily, anyway), but if the egg is being incubated by the female, don't disturb her too often or she may abandon the nest. Good luck!
Posted by Anonymous on February 27, 2004 at 02:12 PM
Q: Our class would like to know where the water goes when the egg is boiled. We massed three eggs and then boiled them. The average mass increase was 4%. How does the "white" watery part of the egg become solid and what happened to the water?
Earhart Environmental School
4th-5th grade class
Wichita, KS
A: I'm unsure what you mean by "massed 3 eggs" and "mass increase" but I think I can tell you what happens to the water. The white part of the egg, the albumin, is mostly water with a little bit of protein. When you cooked the egg, the heat caused the albumin to change into a white, soft yet firm mass. This happens whenever you fry an egg on the stove and you can see it happening as the egg cooks. The water is still there but the protein has caused a different structural arrangement than before so instead of a clear substance, it is a white opaque material.
Thanks for your question. Hope this helps.
Posted by Anita Puppe on January 10, 2004 at 09:08 AM
Q: 1. for what purpose do people use egg yolks? for what purpose do developing chicks use egg yolks?
2. is a egg an organelle, a cell, a tissue, organ or organ system?
A: Answer 1: If I understand your question correctly, people use egg yolks as a food source. Developing chicks also use the yolk in an egg as their food (energy) source. Remember, a developing chick has no other outside source of food, unlike mammals.
Answer 2: A chicken egg has an individual cell plus food source enclosed within the shell. If it is a fertilized egg - not all chicken eggs are fertile - the cell has half of its chromosomes from the mother and half from the father - the two halves added together make up all the requirements for the chicken that will develop. The bulk of a chicken egg, however, is egg yolk and albumin - the cell is too small to be seen with the naked eye.
Posted by L.S. on June 09, 2003 at 01:10 AM
Q: Is it possible for an embryo to survive if the egg's shell is slightly damaged?
A: I personally know of one time when a slightly damaged egg did hatch. When I worked for the International Crane Foundation, one of our artifically incubated eggs became slightly damaged in the incubator but did hatch into a healthy chick. That egg was well along on development when it was damaged so not sure what might have happened if it had been damaged early on.
If the damage isn't too great and bacteria don't get to the embryo too quickly, it seems an embryo can develop completely - at least sometimes. There are probably many factors that influence "hatchability" when damaged.
Posted by Sue Lin on March 05, 2003 at 05:52 AM
Q: Does the size of the air chamber of an egg differ depend on its freshness?
A: When an egg is first laid, it is warm. As it cools, the contents contract and the inner shell membrane separates from the outer shell membrane to form
an air cell in the larger end of the egg. At first, in an egg of highest quality (Grade AA) the air cell may be up to the size of a dime and not more
than 1/8" thick.
As the egg ages, moisture and carbon dioxide leave through the pores of the shell, air enters to replace them and the air cell becomes larger.
So, yes, the size of an egg's air cell does depend on its freshness. The fresher the egg, the smaller the air cell.
Posted by Niki Ellender on February 24, 2003 at 09:29 AM
Q: Why is water important when a chick is developing inside its egg?
A: As an embryo develops, it does so within an aquatic (water) environment. Even baby humans develop within a water environment inside the uterus that is kept constant by the mother. Some of a chick's development draws upon the water within the egg (a bird is about 70% water) and the moisture surrounding a chick allows for the chick's rotation within the egg and the exchange of gases (oxygen in and carbon dioxide out) as well.
The references to moisture being necessary in incubators points out that without proper moisture, hatching success is greatly decreased. Hatching facilities are especially aware of this as they try to maximize their hatching success.
It's interesting to note that Mallard Duck females incubate their eggs for the last few incubation days by periodically wetting their feathers prior to sitting on their clutch. This marked increase in moisture appears to be important in providing the right environment for their eggs to hatch. So, even an outside environment is important to the chicks within each egg if proper development is to be achieved.