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.
Habitat isolation, temporal isolat â¦ ion, and gametic isolation are examples of prezygotic reproductive barriers, meaning that they impede mating or hinder fertilization if mating does occur. barrier is an impediment or obstacle. Physical barriers can include walls or protective enclosures; materials that prevent the passage of substances; or a geographic separ â¦ ation of regions.