During puberty, some primary oocytes will divid meiotically to produce a larger secondary oocyte and a smaller cell called a polar body. If the secondary oocyte is fertilized by a sperm cell, the secondary oocyte will undergo a second meiotic division to produce an ovum and another polar body...
According to the article, egg and sperm donor profiles are sent to prospective recipients. As soon as CC received a “buy-in” from a few patients, the “donor embryos” were created from the donor eggs and sperm. Who made the decision to combine these two donors? What happens to the l...
Traits that exhibit these differences are called sexually dimorphic. They are usually in some way related to how aspects of reprodution occur for a particular species: attracting a mate, the act of mating, birthing offspring or laying eggs and also offspring rearing....
The benefit of not doing so is that the non-helmeted females are able to devote their resources to making many more eggs in adulthood (Laforsch et al., 2006). The trade-off between forming a helmet or not is between present survival and future reproduction. In the presence of the ...
Why do platypuses lay eggs? Platypuses are one of the world's fivemonotremes, or egg-laying mammals. Platypuses' distant ancestors,mammal-like reptiles, split from reptiles roughly 280 million years ago, giving way to the monotremes. Scientists think they evolved before marsupials or p...
‘local’ gamete competition, like gamete competition more generally, is stronger among sperm than among eggs because sperm are more numerous under anisogamy13,14. Consequently, as in Model 1, Bateman gradients are always steeper in males (Fig.1C, D). Recall that the results of the above ...
It is entirely normal for one testicle to be bigger than the other. Many people find that the right testicle is slightly larger and the left hangs lower. A
For sea cucumbers, plastic particles may simply be larger and easier to grab with their feeding tentacles than more conventional food items, but in other species there are indications that plastic consumption is more than just a passive process. Many animals appear to be choosing this diet. To ...
The ova are, however, in an immature form and require further development to reach a stage that can be fertilized by sperm cells. When a cat's heat cycle starts, hormones stimulate the maturation of some of the ova or eggs. Cats are "spontaneous/induced ovulators." This means that a ...
sperm competition between the male that sacrifices himself and other males that appear later; some studies have shown that females do not mate for a time after consuming a male partner, and, thus, other males that follow are less likely to share in the fertilization of the female’s eggs. ...