Adaptations: Built for Water, Land and Air

In the paper

Unit 8 carries 2 of the 40 Zoology marks; averaged over its four chapters that is half a mark per chapter (MEC publishes weights by unit, not by chapter). MEC scope: "Adaptations: Aquatic, Terrestrial, Volant." Items come in three forms:

• Recall — the organ that does a job (swim bladder, lateral line, keel, air sacs), the term for a way of life (cursorial, fossorial, arboreal).
• Understanding — why a whale must surface, why ostriches lack a keel, why a camel lets its body heat up.
• Application — a described skeleton or animal whose habitat you must infer.

An adaptation is an inherited structural, physiological or behavioural feature that improves survival and reproduction in a particular habitat. Unrelated animals in the same habitat often look alike (shark, extinct ichthyosaur and dolphin): this is convergent evolution, and their shared features are analogous, not homologous.