As readers of the evolution section of this book know, a lack of genetic diversity can be harmful to a population of living things (see Chapter 17, page 308, for more). Can you think of an aspect of plant functioning that (a) has grown more sophisticated over evolutionary time and that (b) helps ensure genetic diversity among plants?

Plants (select all that apply):

a. obtain nutrition by consuming existing organic material.

b. obtain nutrition by performing photosynthesis.

c. produce much of Earth’s oxygen.

d. absorb atmospheric carbon dioxide.

e. are a cause of soil erosion.

Defining characteristics of plants include (select all that apply):

a. multicelled

b. hyphae

c. cell walls

d. reproduction through fruiting bodies

e. land-dwelling

In the alternation of generations seen in plants (select all that apply):

a. one generation produces flowers, the next does not.

b. one generation produces spores, the next produces eggs and sperm.

c. succeeding generations tend to be about the same size.

d. succeeding generations tend to differ in size.

e. all generations produce spores.

Only angiosperms (select all that apply):

a. perform photosynthesis.

b. produce seeds.

c. encase seeds in fruit.

d. have seeds containing endosperm.

e. have eggs encased in pollen grains.

Pollen grains contain:

a. hormones.

b. food for the new plant generation.

c. eggs that will be fertilized by sperm.

d. sperm.

e. chloroplasts.

Phototropism and gravitropism lead to the bending of shoots or roots toward or away from a stimulus (light or gravity, respectively). Such bending is brought about by:

a. increased growth over the general surface of the root or shoot.

b. differential growth on opposite sides of the root or shoot.

c. muscular contractions, leading to a curvature in the root or shoot.

d. loss of water into the atmosphere.

e. all of the above.

Photoperiodism allows some plants to respond to _________ by timing such things as ________ in accordance with the amount of _________ they are exposed to.

a. predators; dormancy; moisture

b. competition; growth; moisture

c. the seasons; growth; toxins

d. other plants; flowering; IAA

e. the seasons; flowering; darkness