Introduction
Animals, like plants, show structural and behavioural features that fit them to their particular way of life, and their populations are increasingly shaped by human-caused changes to the environment. This unit covers three connected themes: animal adaptation to different habitats, animal behaviour including migration, and environmental pollution and its control.
Animal adaptation
Adaptation is any structural, physiological or behavioural modification that helps an animal survive and reproduce successfully in its particular habitat.
Aquatic adaptation
- Primary aquatic adaptation: seen in animals that have always lived in water and never had a terrestrial ancestor, such as fish. Features include a streamlined, spindle-shaped body to reduce water resistance, gills for extracting dissolved oxygen from water, fins for propulsion and steering, and a lateral line system to detect water movement/pressure changes.
- Secondary aquatic adaptation: seen in animals whose ancestors were terrestrial but which later re-adapted to an aquatic life, such as whales, dolphins, seals and aquatic reptiles/birds (turtles, penguins). Because their ancestry is terrestrial, they still breathe air with lungs (surfacing periodically), but show convergent adaptations such as a streamlined body, limbs modified into paddles or flippers, a thick fat (blubber) layer for insulation and buoyancy, and, in whales, the loss of hind limbs altogether.
Terrestrial adaptation
- Cursorial adaptation: modification for fast running on land, seen in animals such as the horse, deer and cheetah. Features include a streamlined body, long and powerful limbs, reduction in the number of toes, and digitigrade or unguligrade locomotion (walking on the toes or hooves rather than the flat foot) to increase stride length and speed.
- Fossorial adaptation: modification for a digging, burrowing life underground, seen in animals such as the mole, rabbit and mole-rat. Features include a small, tapering head that acts like a wedge, short but powerful forelimbs with strong digging claws, reduced or absent external ears and eyes, and a cylindrical, compact body suited to moving through narrow tunnels.
- Arboreal adaptation: modification for climbing and living in trees, seen in animals such as the squirrel, chameleon and monkey. Features include grasping hands/feet or claws for gripping branches, a long, often prehensile tail used for balance or as an extra grasping limb, and, in some primates, forward-facing eyes for the depth perception needed in climbing and jumping.