Biology | Answers to Review Questions

Author Dr. George B. Johnson, Washington University
Author Dr. Peter H. Raven, Missouri Botanical Gardens & Washington University
Contributor Dr. Susan Singer, Carleton College
Contributor Dr. Jonathan Losos, Washington University

Answers to Review Questions

Chapter 42 (p. 852)

1. Nine characteristics are flowers, gamete transfer (without requiring water ), outcrossing, fruit dispersal, tough leaves, leaves with stomata, leaves with cuticles, specialized conducting elements, and production of natural insecticides.

2. The corolla is collectively made up of petals. The petals of most flowers are homologous with stamens in that both are affected by genes that do not affect either carpels or sepals.

3. An androecium is the male reproductive structure, and it is composed of the stamens.

4. Dichogamous plants are functionally staminate at one point in time and functionally pistillate at others; that is to say, the plant has both male and female parts, but they are not fertile at the same time. The advantage to this is that it promotes outcrossing, leading to more genetic diversity in the population.

5. Solitary bees have only a single brood to raise and use only a single type of flower. It is more likely that this flower will be visited by a solitary bee because it visits only a single type of flower; thus they can evolve together.

6. Asexual reproduction is advantageous to a well-adapted plant in an unchanging environment because it eliminates the risk of variability caused by sexual reproduction.

7. Apomixis is essentially self-cloning by a plant. A seed results that has all of the qualities of the parent plant and the advantages inherent in seeds, such as dispersal mechanisms and dormancy. This would insure repeated crops of the same quality.

8. Annuals have the advantage of spending bad times as a dormant seed and taking rapid advantage of good conditions. Perennials must endure bad times but are equipped for food storage and are not dependent on germinating conditions for survival.

9. When hormonal changes such as reduction in cytokinin production take place in the leaf, the abscission zone becomes active. A protective layer of suberin-filled cells develops on the stem side of the petiole base. A separation layer develops on the leaf side of the petiole. This layer, which contains pectin, may swell or become gelatinous. With deteriorating weather conditions, an enzyme breaks down the pectin in the separation layer and wind or rain separates the leaf from the stem. Abscission rids the plant of the energy drain of parts that are no longer useful.