1. Biological extinction – Disappearance of species unable to adapt
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2. Biological extinction is a natural evolutionary process but accelerated by human activities (biological extermination)
3. Phases of biological extermination
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(a) Regional extermination – disappearance from part of its normal range
(b) Ecologically exterminated – too few individuals left to have any significant impact on the ecology of their habitat
4. IUCN has identified four categories of species heading towards extermination.
(a) Endangered species – one in immediate danger of extermination (extinction) e.g. Everglades kite, blue whale.
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(b) Critically endangered species – will not survive without direct human intervention and protection e.g. Californian condor and whooping crane.
(c) Threatened species – so called because of decline in numbers, e.g. grizzly bear, sandhill crane green turtle.
(d) Rare species – not presently in danger but are subject to risk.