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Variation and natural selection (CCEA)Extinction

Organisms of the same species vary in many ways. There are two types of variation – continuous and discontinuous. Natural selection explains how evolution occurs.

Part of Combined ScienceGenetics

Extinction

are extinct if there are no living individuals left.

Extinction happens if a species fails to adapt to changes in its environment.

Fossils have provided us with information on some extinct species.

A dinosaur fossil

Extinct species include dinosaurs (caused by a meteor strike) and dodos (hunted by humans).

A dodo skeleton

Species that are at risk of becoming extinct are known as endangered.

A species can become extinct for many reasons, including:

  • Climate change.
  • Natural disaster.
  • Hunted by humans.
  • Hunted by non-native animals (introduced by humans).
  • Disease.
  • Loss of habitat (e.g. deforestation).

Extinction can be avoided by:

  • Legislation preventing the hunting of endangered species.
  • International agreements, including those that plan to limit climate change.
  • Special programmes such as creating nature reserves to protect habitats.
  • Education that encourages people to do their part in protecting the environment.

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