Chapter 20
Extinction and Conservation
Extinction of species
In the past, extinction has been closely related to climate changes.
Ectothermic animals (reptiles, amphibians, fish and all of the invertebrates) cannot
regulate their body temperature by physiological means. Their body temperature varies
directly with that of their external environment. Dinosaurs were ectothermic. This raises
problems if the external temperature alters considerably. It has also been shown that
temperature changes can affect the development of certain reptile eggs so that only
one sex results in the offspring.
Endothermic animals are able to maintain their body temperature at a relatively
constant level which does not depend on the temperature of the external environment.
Mammals have achieved success because of their ability to withstand extremes of
temperatures in their surroundings and because they have developed the ability to
provide milk for their young and provide parental care.
Effect of Human Activities
More recently, extinction of species has been related to human activities such as

Over-hunting

Habitat destruction
Conservation of Species

Wildlife reserves

Captive breeding programmes

Cell banks
Consider why there is a need for conservation of species and make a note about the
maintenance of genetic diversity (biodiversity). See p 146 Torrance.
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