3.1.17 (HL)—Mass extinction and speciation

A mass extinction removes many species and roles rapidly; survivors may diversify into newly vacant niches.

Physical drivers can interact—tectonics, eruptions, climate, sea level or impact. Afterward, reduced competition and divergent selection can support adaptive radiation. The current crisis is dominated by human pressures.

If a lineage survives while major competitors disappear, descendants may split into forms using different resources.

Extinction first removes functions and stability; diversification takes many generations and is uncertain.

Vacant niches do not guarantee recovery; suitable conditions, variation and time are required.