Answer:
Rocks from retreating glaciers
MAOI's work better with patients whose depression becomes more acute as the day progresses. An enzyme named monoamine oxidase is intricate in eliminating the serotonin, neurotransmitters norepinephrine and dopamine to the brain. MAOIs avoid this from happening which makes more of these brain chemicals obtainable to effect alterations in together cells and circuits that have been obstructed by depression.
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.
