Extinction and biodiversity

1Extinction

A species is extinct when its last individual dies: it can never come back. The last passenger pigeon died in 1914. Most species that have ever lived on Earth are now extinct.

extinct

2A changing environment

When the environment changes, some individuals may be less well adapted to compete and reproduce. As the climate warms, mountain-top species have nowhere cooler to go. If none can cope, the species dies out.

3Variation helps

A species with plenty of variation is more likely to include some individuals that cope with a change. They survive and breed, so the species adapts. With little variation, it may die out.

4Causes of extinction

Extinctions can be caused by sudden disasters, new predators or diseases, competition, hunting, habitat destruction and climate change. Today, human activity causes most of them.

5Biodiversity

Biodiversity is the variety of living things in an area, including the variation within each species. It keeps food webs stable and gives us food, materials and medicines.

Biodiversity

6Gene banks

A gene bank stores genetic material so it isn't lost. Seed banks keep dried, frozen seeds. Sperm, eggs and embryos of endangered animals are frozen in liquid nitrogen, at −196 °C.

gene bank

7Protecting species

We can protect species by saving habitats in nature reserves, breeding animals in zoos and releasing them, banning hunting and trade, and restoring lost habitats.