AP BIOLOGY

Detailed explanation-1: -If two or more species share a unique physical trait they may all have inherited this trait from a common ancestor. Traits that are shared due to common ancestry are homologous structures. The similar bone arrangement of the human, bird, and whale forelimb is a structural homology.

Detailed explanation-2: -Cetacean flippers have the same bones as the forelimbs of other mammals. The humerus, radius, ulna, carpals, metacarpals and phalanges are all present. However, in cetaceans the radius and ulna (forearm) and humerus (upper arm) are fused. Thus, they don’t have elbows.

Detailed explanation-3: -The flippers in whales and the wings in the birds are referred to as homologous because these organs have arisen through divergent evolution. These organisms, therefore, have a common ancestor.

Detailed explanation-4: -An example of homologous structures are the limbs of humans, cats, whales, and bats. Regardless of whether it is an arm, leg, flipper or wing, these structures are built upon the same bone structure. Homologies are the result of divergent evolution.

Detailed explanation-5: -Explanation: When parts of an animal serve different functions but have similar placement and bone structure (such as a wolf forearm and a whale flipper) and are derived from a common ancestor, these two structures are homologous.