Exam 17: The Origin of Species

Two populations of plants look identical but their flowers are fertilized by different pollinators-one by a night-flying hummingbird moth, the other by honeybees. These two populations of flowers are examples of

In the late 1700s, two populations of minnows became isolated when an earthquake altered the path of a river. Now the populations can no longer successfully breed with each other even when they are both moved to the same pond. These organisms have undergone _________speciation.

A horse has a diploid number (2n) of 64 and a donkey has 2n = 62. The hybrid of these two species, mules, have 2n = 63 and are sterile. Why are mules sterile?

From an evolutionary perspective, explain how three species of large, flightless birds (ostriches, rheas, and emus) came to occupy the widely separated landmasses of Africa, South America, and Australia.

When offspring are infertile after breeding occurs between individuals of different species, the genetic identities of the two populations are protected by

What are the five premating isolating mechanisms that keep different species from successfully mating?

Two fossils may be assigned to different species if

The immediate cause of most extinctions is

Researchers believe that at least_________ % of the species that have lived on Earth have become extinct.