76) Describe the difference between homologous and analogous structures in organisms, and give an example of each.

77) Temporal and behavioral isolation are examples of premating isolating mechanisms. Mechanical isolation, gametic isolation, and hybrid inviability are examples of postmating isolating mechanisms. Premating isolating mechanisms are considered much more important in keeping closely related species genetically separate than are postmating isolating mechanisms. Do you agree? Why or why not?

78) In the early nineteenth century, the French scientist Georges Cuvier provided conclusive evidence of the extinction of species on Earth. Although Cuvier correctly asserted that a series of catastrophes led to these extinctions, he could not provide a testable explanation of the source of the new animals and plants that appeared after the extinction of older forms. How would you argue that modern evolutionary theory provides an explanation for the proliferation of new forms of life after mass extinctions?

Refer to the figure below, and then answer the question that follows.

79) Migration of the salamander Ensatina eschscholtzii separated an original population as they moved either west or east of the Central Valley of California. Eastern and western species then evolved. The Central Valley is an example of a/an:

A) temporal isolating mechanism.

B) mechanical isolating mechanism.

C) extrinsic isolating mechanism.

D) intrinsic isolating mechanism.

Refer to the figure below, and then answer the question that follows.

80) Which of the following pairs are most closely related?

A) crocodiles and dinosaurs

B) turtles and snakes

C) mammals and birds

D) dinosaurs and birds