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.
The answer is ‘panthers will become extinct due to the lack of genetic diversity’. The population will enter what is referred to an extinction vortex. This is when environmental, demographic and genetic factors interact and reinforce each other in a downward spiral of a species. The lack of genetic diversity in the population causes inbreeding and lack of diversity on which natural selection can act upon for the population to adapt.
