What is a limb in biology?

In biology, a limb is an external, jointed body part like an arm, leg, wing, or fin that helps an animal move or handle objects.

Biology uses the term “limb” mainly for animals, especially vertebrates. Limbs are paired structures that grow from the body wall during development. They have bones or cartilage inside, muscles that move them, nerves that control them, and blood vessels that feed them. Most limbs have joints, which are flexible connections that allow bending and rotation. Because of joints, limbs can perform complex tasks, from simple walking to fine tasks like writing or playing a musical instrument.

Core biological aspects

• Structure: Bones (or cartilage), joints, muscles, tendons, ligaments, nerves, and skin.
• Types: Forelimbs (front pair) and hindlimbs (rear pair).
• Functions: Locomotion, manipulation, feeding, defense, display, and balance.
• Variation: Wings in birds and bats are modified forelimbs; flippers in whales and seals are limbs adapted to water; insect “limbs” are segmented appendages but differ from vertebrate limbs in anatomy.

Examples across groups

In short, a limb in biology is a mobile appendage that increases an animal’s ability to move and interact with its environment. Its exact form changes with lifestyle, but the core job stays the same: enable action.