Question

Human bones and the bones of other vertebrates share the same anatomical plan. They are homologous structures rather than analogous structures such as a dragonfly wing and bird wing. Comparing and contrasting the anatomy of similar organisms assists with understanding of how the body is put together.

Check out the limbs figure on this webpage: Homologous Structures. Pick one of the animal limbs for the discussion below (horse, cat, bat, bird, or whale limb).

1. In your own words, explain two ways in which the animal limb bones are similar to human limb bones.

2. In your own words, explain two ways in which the animal limb bones are different from human limb bones.

Answer 1

FORELIMBS in human arm and bird wing are homologous. The limb serves the same function: as a forearm (not a wing) in the last common ancestor of tetrapods later on the limb diverged, taking different forms to fulfill different functions.mosaic evolution modifies different organs at different times and rates and under different selective pressures.

skeleton of land animals is also different from aquatic animals. The shoulders attached to the pectoral girdle through muscles and connective tissue, thus reducing the jarring of the skull. Because of a lateral undulating vertebral column, in early tetrapods, the limbs were splayed out to the side and movement occurred by performing “push-ups Later tetrapods have their limbs placed under their bodies, so that each stride requires less force to move forward which resulted in decreased adductor muscle size and an increased range of motion of the scapulae and also restricts the movement primarily to one plane, creating forward motion rather than moving the limbs upward as well as forward.