Final answer:
Analogous structures are structural similarities based on common function and not common evolutionary descent. They evolve independently in different lineages, as adaptations to similar environmental conditions. An example is the streamlined body shapes and fins in fishes and whales, both adaptations to moving in water.
Step-by-step explanation:
Analogous structures are structural similarities between species that are based on common function and not on common evolutionary descent. These structures evolve independently in different lineages and are adaptations to similar environmental conditions. For example, the streamlined body shapes, fins, and tails in fishes and whales are analogous structures because they are adaptations to moving and maneuvering in water.