Question

Sort the examples into proper mechanisms of reproductive isolation.

prezygotic postzygotic






the inability of red and purple
sea urchins to mate due to
gametic incompatibility


a sterile zonkey formed from
the mating of a donkey and
a zebra


different mating calls for two
different grasshopper species


the death of a zygote after
few weeks of formation

Answer 1

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.

Answer 2

PRE

1.) the inability of red and purple

sea urchins to mate due to

gametic incompatibility

3.)different mating calls for two

different grasshopper species

POST

4.)the death of a zygote after

few weeks of formation

2.)a sterile zonkey formed from

the mating of a donkey and

a zebra