Answer: Genus
From largest to smallest, the pyramid of binomial nomenclature goes: kingdom, phylum, class, order, family, genus, species.
Pangea was the supercontinent that had all the landmasses of earth together before the Triassic period and that broke up into Laurasia and Gondwanan. However, Panthalassa is a prehistoric ocean that was surrounding Pangea.
Hope this helps!
The mechanisms of reproductive isolation prevent the reproduction of two individuals from different species. The prezygotic mechanisms disrupt the stages of reproduction before the forming of the zygote or prevent the mating at the start, and the postzygotic mechanisms affect the stages of reproduction after the forming of the zygote.
So, the first and the third example (the urchins and the grasshoppers) show the prezygotic mechanism, as the two individuals are not able to mate or form a zygote.
The second and the fourth example ( zonkey and the death of a zygote) show the working of the postzygotic mechanisms, as the zygote is formed, but it seems to be inviable, and the zonkeys are sterile, preventing the individual to reproduce.
Most scientific questions are based off of theory.
