<span>are we talking human reproduction? in this case only 1 egg is implanted. in unusual cases there could be 2 eggs implanted meaning fraternal twins. if 1 egg splits, we get identical twins. with only one egg implanted, there is only 1 kid being produced.
the female has eggs stored from birth. 1 ovary 'pops' once a month to either be discarded via a period or implanted after fertilization. multiple eggs released is usually the effect of fertility drugs making many eggs get released at once. this is unusual unless fertility drugs are in use</span>
Answer:
Because the offspring of a male and female are always going to be xx, xx, xy, or xy.
Explanation:
Remember that men have different reproductive chromesomes than women. Women have 2 x chromesomes(xx) while men have 1 x and 1 y(xy). These are given down to their offspring.
So we can write the this out in a punnet square as(link down below).
After you see the visual, you will find that the genotypes are xx, xx, xy, xy.
As I said above, women have sex chromesomes xx, while men have sex chromesomes xy. When you match the genotypes on the punnet square with the ones we know from men and women, we find that two of them match with men and two match with female.
So with this, we can conclude that 2/4 of offspring will always be male and 2 will be female. And as you well know 2/4 is 1/2 which is 50%.
I think homologous structures is a great example and idea that supports the theory of evolution. Homologous structures shows us how our futures evolved by natural selection.
the key element in the ecological concept of species is that individuals within a species can successfully interbreed and conceive healthy offspring