Learning Objectives

7.3.1 Contrast the benefits and costs associated with small size in early life cycle stages.

7.3.2 Explain how adaptations at specific stages in a complex life cycle may benefit the species.

7.3.3 Compare the benefits of semelparity and iteroparity in the context of total lifetime reproduction of an organism.

In Concept 7.1, we saw that an organism's size and form may vary greatly over the course of its life cycle. Each life cycle stage may have different habitat preferences, food preferences, and vulnerability to predation. These differences suggest that different morphologies and behaviors are adaptive at different life cycle stages. Differences in selection pressures over the course of the life cycle are responsible for some of the most distinctive patterns in the life histories of organisms.