AP Biology 3.5 Evolution

And here are the potential answers: Many species are seasonal breeders based on

favorable conditions, such as abundant food and water supplies.

Many species’ wives wish they were romantic breeders who would bring home flowers and [Rhino wife wishing for more romantic Rhino husband]

chocolates once in a while.

Species like ring-tailed lemurs, horses, hamsters, and groundhogs prefer breeding in spring, [two groundhogs together in a forest]

while sheep, goats, elk, and mice prefer the fall.

Rabbits, however, pay no attention to the calendar. [lots of rabbits together]

Though is this seasonal reproductive barrier best described as “mechanical”?

Well, “mechanical” refers to the fact that some species are unable to mate with [A snake and a turtle side by side]

other species because…well, physically they just can’t.

The mechanics of the process are incompatible, which means A is incorrect.

How about B?

Is seasonal mating a geographical reproductive barrier?

Let’s say a body of water separates one herd of hippos from another. [Two hippo's either side of a body of water]

While that would be a darn shame, it wouldn’t have anything to do with the seasons.

So B isn’t our answer, either. [Hippo entering the ocean]

Let’s look at answer “D”.

A hybrid zygote is formed when no barriers exist to interspecies mating. [A zebra and a horse together and a hybrid of the two appears]

Since this is a pretty big no-no in nature, a post-zygotic reproductive barrier kicks

in to insure that the hybrid is infertile and won’t reproduce. [Hybrid of zebra and horse disappears]

Since “D” is all about isolation mechanisms, we can eliminate it as our correct answer.

That leaves us just with “C,” temporal.

Temporal separation is defined as a mating barrier achieved by differences in the timing

of species’ mating seasons.

Looks like C is our right answer.

Now will someone please get that poor rhino a box of chocolates…? [Two rhinos sniffing for chocolates]