Why Species Become Extinct

Extinction may be caused by:
− changes to the environment    − new predators    − new diseases    − new competitors.

A species becomes extinct when the last individual of that species dies. Extinction is a natural thing. It is estimated that 99.9% of species that have aver existed are now extinct.

So why do species die out?

Changes to the Environment Thanks to evolution most species are highly adapted to survive in a particular environment. If that environment changes then the species may not be able to adapt. Changes might be the environment getting warmer or cooler, a certain source of food disappearing. Toxic pollution could make a habitat unliveable very quickly.	New Predators When white settlers landed in New Zealand they brought with them a variety of species such as rats and cats. These hunters soon finished off many of the species that had never been hunted before such as the Dodo.
It is believed that dinosaurs became extinct due to the effects of a giant meteorite hitting the Earth.	The Bali Tiger. Hunted to extinction.
New Diseases A disease may be brought to an environment from outside, e.g. when white sailors first arrived on Polynesian islands bringing many germs for which the locals had no immunity. Microbes evolve very quickly as they reproduce so rapidly. A new virus could wipe out a whole species.	New Competitors There is usually a limited amount of resources (food, water, space etc) in certain habitat. If the amount of competition for these resources increases then a species which relies on them may die out.
Many of the worlds frogs are threatened by new fungal infections.	Not only are sharks themselves hunted but their food supply is dwindling due to overfishing.