Why is a polar body unable to support the development of an embryo?
832444
Nutrient material and necessary organelles are missing.
512190
Many bats also delay implantation after the eggs are fertilized.  There are also several mammal groups that have delayed fertilization, holding viable sperm for months until they are ready to begin gestation, and then an egg cell is fertilized.\n\nThis is possible in placental mammals where the egg cell is kept internal, and doesn't have a shell to protect it from the outside environment.  I doubt that it would be possible in, for example, birds, where once the egg is formed it's pretty much a done deal, and development goes ahead regardless of outside conditions.
1099085
I don't think you mean development of the zygote....that is a fertilized egg.  Do you mean all the embryological stages after fertilization? There are similarities and differences in all three of these organisms' embryology.\n\nThe starfish zygote and amphibian zygote are both slimy-jelly coated and are vulnerable to fungus-bacterial infections in the water they are laid in, and vulnerable to being eaten by misc hungry aquatic organisms. These eggs are laid and fertilized as a result of external fertilization in the water.  Starfish just release the gametes in the water at a specific time in breeding season without a mating act per se.  If you are standing on a hill above a tidepool while groups of male and female starfish shed their gametes you can see the cloudiness in the water from the huge quantities of sperm and egg they release quasi-synchronistically. \n\nFrogs and other amphibians actually have a mating act called amplexus. The male does all the ribbiting to audition for the job of dna donor.  If she is ok with it, he jumps on the back of the female and he squeezes her eggs out while he releases his sperm on them. Starfish zygotes go thru many many larval stages-metamorphoses (they are part of zooplankton) and eventually mature to the adult on the tidepool rocks.  The bipinnaria larva of echinoderms are famous for their DEUTEROSTOMATE development like other vertebrates-chordates (see below)!\n\nAmphibian zygotes eventually turn into ONE aquatic tadpole larval stage which uses gills and then grow appendages-lungs to be eventually become more terrestrial.  \n\nAmphibians do not have an amnion in their eggs and are therefore anamniotes. Birds and reptiles produce "land eggs" that can resist dessication pretty well and are therefore called AMNIOTES, those who have the amniotic sac to help protect the developing embryo from the drying air on land. The amniotic fluid is in the amniotic sac. Mammals can lay eggs (monotremes) but most are placental mammals who have the amniotic sac in the uterus, but amnion and amniotic fluid with the fetus is not inside a shelled egg like the birds and reptiles.So placental mammals are the most advanced amniotes\n\nOne way these three embryo types do NOT differ: starfish and amphibian and bird are all "deuterostomate" animals.  . All animals you listed on your question are deuterostomate. Most invertebrates are "protostomes. So it is said to be an evolutionary LINK, that the echinoderm-starfish bipinnaria larva shows deuterostomate embryology! "Proto means "first," deutero means "last" and stom means "mouth." Again, both echinoderm bipinnaria larva and chordates-vertebrates (amphibians and birds) are deuterostomate. \n\nWhen embryos change from blastulas to gastrulas, there is an early indentation-invagination process of the tissue to begin the formation of endoderm and the future GI tract from MOUTH to ANUS.  In protostomates, most invertebrates except the echinoderm-starfish group, the mouth is formed first at the first indentation or invagination of blastula to become gastrula, and the anus is formed last.  \n\nIn the deuterostomates, the mouth is formed last and the anus is formed first.  The Echinoderms which includes the starfish, are deuterosomates like the chordates (bird and amphibian), including us humans. Aren't you glad you now know that your anus formed before your mouth?
837002
1. Studies show that during the development of the embryo, it takes different forms that "recap" the evolutionary process that has produced the animal which is about to be born. For instance, during human embryogenesis, foetus exhibit a tail, a feature that our distant ancestors have had.\n\n2. No, they do not share structural similarities. So they are not closelly related.\n\n3. It's convergent evolution: even though both organs have different origins (a fin is a bone projection, while the flipper is the equivalent of our arms), evolution tried to satisfy the same need : to move in water.
332835
an embryo is a mass of cells dividing and whatnot.  a fetus is when signs of life are discernible
1007735
they aren't able to breathe or reproduce.... or grow and develop
949605
First of all, I'm pro-choice and I support embryonic stem cell research.\nSecond, it'd be impossible to get stem cells from an aborted fetus.  Embryonic stem cells come from embryos - hence the name.  The cells used  come from embryos that are less than a week old.  Older cells wouldn't work because embryonic stem cells are undifferentiated cells that haven't developed into specific adult cells yet.  So an older cell that has already developed would be useless for research purposes.
663414
No, the number of chromosomes in the two is different so it would not create a baby.
777949
Remember that meiosis is the formation of gametes from germ cells.  Our bodies begin the process of making germ cells very early in our development, and the precursors to sperm/egg cells are in tact well before puberty.  When a woman ovulates, at the end, four of these egg cells complete the maturity stage in each cycle, but only one survives to become an ovulated egg (accompanied by 3 polar bodies).  This egg (and its complement sperm) have ONE set of chromosomes each, and upon fertilization, the zygote will have 2 copies of every chromosome, one from the sperm, and one from the egg.
389656
yes can you also, email me the answer. It would be helpful in my polysci. class.
897987
Because they develop similarly. Read this: http://www.ucmp.berkeley.edu/chordata/chordata.html
643173
There are many disabilities that are not genetic. Some simply happen by chance, some because the egg was old, some are only possible if both the mother and father are carriers of the disability. If you are really concerned, you and your boyfriend can see a genetic counselor who will be able to tell you if a child produced by the two of you would be at risk.
352803
Because we are not yet an independently human being during this period of 9 months. Our body is bounded at our mother's body and the 2 bodies function like a system. When our fetus body is complete, so that we can use our own digestive system for the nutrition, comes the moment of the birth when we naturally break the connection. In this moment is beginning our own life as an independent human body (but of course we are independent only from the body-perspective, otherwise we depend of other people in the point nutrition, care etc.).\nThis theory of calculating the age is guilty only for the natural birth.I don't know how it shows in other situations : the clones, for example.
533771
You may be thinking of homeobox genes. These genes are crucial to early development and have been greatly conserved between groups of organisms. The genes tell the embryo what the basic body plan is. If there's a homebox mutation, you may end up with three arms or a leg where an arm goes, etc. These genes are very important but they aren't the only ones and I'm not sure you could say that any genes are "dedicated to protecting the substance of each biological life form."
212143
polar...water molecules "stick" to each other so to speak...
957839
Usually, cellular damage and dessication.\nIce crystals forming are like tiny spears which pierce through cell membranes and cause extensive damage.   At the same time, the freezing water causes osmotic imbalance, pulling water out of the cells and shriveling them.\nSome plant tissues combat freezing by creating various organic forms of antifreeze in their cells.  \nDid you know even some amphibians do this?  Wood frogs, for example.
825499
A fertilized egg will develop and grow and one day enter the world where it will be given a name. \n\nAnyone can argue that it is not human until it breathes but, even they must admit by aborting the fetus it is prevented from being born. \n\nA fetus has a heartbeat. Abortion stops that heartbeat. Think about it.