Navy blue. For other uses, see Navy blue (disambiguation). Navy blue is a very dark shade of the color blue. French sailor in dark blue uniform. Navy blue got its name from the dark blue (contrasted with white) worn by officers in the British Royal Navy since 1748 and subsequently adopted by other navies around the world.
Hybrid sterility is what results when individuals from two. different species are able to mate but their offspring is infertile, meaning that their. offspring are not able to reproduce. Because this occurs after the formation of the. zygote, this is a postzygotic isolating mechanism, not a prezygotic mechanism.
Postzygotic Barrier. Reproductive isolation mechanism that acts after the point of conception. Postzygotic reproductive barriers act after the point of production of the zygote, contrasting prezygotic barriers which instead act to prevent conception.This represents a fundamental difference because up to the point of conception no eggs have been wasted nor progeny.he mule is the classic example of a postzygotic barrier as they almost always display a reduced hybrid fertility, and this is despite the fact that mules are otherwise impressively robust animals. For more on this topic, see Wikipedia and Google. Contact web master.