Why are egg cells in birds relatively few in number and large in size?
348052
I think they're few in number because birds really don't live that long, or have too many babies, so they only need a certain number.  I'm sure they're large in size because they have to nourish the baby birds inside after the egg leaves the mom's body, unlike human babies, who get their nourishment straight from the mother.\n\nI'm not sure if that's right, but I hope it helped.
417879
This question appears regularly in the question file, so let's take a shot at it. \n\nIn nature, living things evolve through changes in their DNA. In an animal like a chicken, DNA from a male sperm cell and a female ovum meet and combine to form a zygote -- the first cell of a new baby chicken. This first cell divides innumerable times to form all of the cells of the complete animal. In any animal, every cell contains exactly the same DNA, and that DNA comes from the zygote. \n\nChickens evolved from non-chickens through small changes caused by the mixing of male and female DNA or by mutations to the DNA that produced the zygote. These changes and mutations only have an effect at the point where a new zygote is created. That is, two non-chickens mated and the DNA in their new zygote contained the mutation(s) that produced the first true chicken. That one zygote cell divided to produce the first true chicken. \n\nPrior to that first true chicken zygote, there were only non-chickens. The zygote cell is the only place where DNA mutations could produce a new animal, and the zygote cell is housed in the chicken's egg. So, the egg must have come first.
864367
D.  The egg is a gamete, which contains half the amount of chromosomes that the body cell normally carries.
995613
Well, Studies have shown that life started with a single cell organism. This was figured by the adaptation that they grew to multiple cells which were mammals. So the correct answer would be "The chicken came before the egg.
339217
Maybe those 3 eggs were unfertilized.  The hen that laid them may be part of the group of hens that are kept separate from roosters so that their eggs are kept unfertilized in order to sell them to markets without having to worry about the possibility of having a chick in it.  Or if there were chicks maybe they never developed.  This is why they say "Never count your chickens before they hatch".
750402
With the increase in cell size the ratio between surface area and volume decreases. A large cell will therefore  have less surface area compared to the volume to  cope with the demands of the cell as far as the exchange of materials between the extracellular environment and the cytoplasm is concerned.On the other hand a smaller cell will have large surface area to adequately meet the demands of the volume of the  cytoplasm.The cell volume depends upon r to the power 3 and the cell surface depends upon r(radius) to the power 2. This becomes the limiting factor for the growth of the cell.
708263
Suface Area and Transport Distance. I Strongly Suspect the Reason Prokaryotic/Eukaryotic Cells Are the Size they Are is Because of Evolutionary Optimization by Natural Selection.
692674
Fertilisation occurs before formation of the shell. However, many times, birds lay eggs that are not fertilised (take chicken eggs for example).
1008328
an egg, but im not sure how big
655003
When the egg and the sperm fuse (in sexual reproduction) a single cell is formed.  That cell divides and divides and keeps on dividing until a full sized critter or plant is formed.\n\nSingle celled creatures reproduce by splitting in half to make two new critters.
40671
Because only triploblasts (with mesoderm) are able to produce a coelom. And maybe, because we triploblasts seem to be the majority ;)
474554
egg.........\n\nthe progenitors would not (quite) be chickens...
760868
Organelles don't have much of an effect on cell function--mostly it's its shape. More active cells are smaller than less active cells so information can quickly pass through the cytoplasm and into the nucleus. This explains why muscle cells are long, small and slender, and fat cells are large and bulky. \n\nThe membrane of smaller cells has many exterior folds to increase its surface area and ablitily to collect nutrients necessary for cell function.
474939
Depends on the bird. Usually it is inversly proportional to the size of the cache of eggs. Chickens for example lay a great number of eggs because they are flightless and pretty much defenseless. Mortality is high so the species compensates with prodicious egg laying. Interestingly this makes them an excellent livestock choice which has certainly contributed to the survival of the species.
430415
To answer your question....yes.  The egg cells of the female all carry X chromosomes.  The sperm cells can carry either X or Y.  So basically, the sex of a mammal depends on the male, and which particular sperm fertilizes the egg (X).  If an X sperm fertilizes the egg, you have XX, which is a female, and if a Y sperm fertilizes it, you have XY, which is male.  This is why some sex-linked traits are more visible in males, such as color blindness, but that's a whole different post.
145878
In nature, living things evolve through changes in their DNA. In an animal like a chicken, DNA from a male sperm cell and a female ovum meet and combine to form a zygote -- the first cell of a new baby chicken. This first cell divides innumerable times to form all of the cells of the complete animal. In any animal, every cell contains exactly the same DNA, and that DNA comes from the zygote. \n\nChickens evolved from non-chickens through small changes caused by the mixing of male and female DNA or by mutations to the DNA that produced the zygote. These changes and mutations only have an effect at the point where a new zygote is created. That is, two non-chickens mated and the DNA in their new zygote contained the mutation(s) that produced the first true chicken. That one zygote cell divided to produce the first true chicken. \n\nPrior to that first true chicken zygote, there were only non-chickens. The zygote cell is the only place where DNA mutations could produce a new animal, and the zygote cell is housed in the chicken's egg. So, the egg must have come first.
363791
Fertilized eggs can be easily maintained in humidified incubators and during early stages of development the embryo floats on to of the egg yolk that it is using for nutrition. As the embryo grows it sinks into, or below the, yolk. The regular appearance of somites allowed early experimenters to acurately stage the embryo. The embryo was accessible and easy to manipulate (limb grafts/removal etc) that were informative about developmental processes. Chicken cells and tissues (neural ganglia/fragments) are also easy to grow in tissue culture. The discovery that quail cells have a different nuclear appearance meant that transplanted cells (chick/quail chimeras) could be tracked during development.