A species is classed as extinct when no more individuals of that species are left. There are two ways extinction can happen:
Extinction happens naturally when a species cannot adapt to changes in the environment. A species can also become extinct due to human activity, which is preventable. Once a species becomes extinct, it is gone forever. However, some scientists are trying to use genetic engineering to bring extinct species back to life.
Species go extinct all the time. In fact, more than 99% of organisms that have lived on Earth are extinct.
Some causes of extinction are:
Some events are so catastrophic that they can wipe out entire ecosystems. For example, a meteorite colliding with Earth or a volcanic eruption. Catastrophic events can change the climate or the environment that the species lives in, therefore making them unable to survive.
Initially, a species may have defence mechanisms against particular predators in the ecosystem, so the population of the species did not drop too low. However, introducing a new predator can make this species more vulnerable, as they may not have enough time to develop new defence mechanisms. This can lead to extinction.
Human activity is introducing new predators into previously isolated ecosystems, which is leading to extinction. For example, urbanisation has caused many species to migrate, which can disrupt ecosystems.
A species will not have resistance to a new disease, which makes them more vulnerable. The species may be wiped out before they are able to develop immunity against the disease.
Human activity influences the climate and the Earth’s temperature through processes such as burning fossil fuels. When fossil fuels burn, they release carbon dioxide into the atmosphere, which contributes to global warming.
If global temperatures rise, some species may not be able to survive at higher temperatures, which can lead to extinction. A rise in temperature also destroys many habitats.
The dodo was a flightless bird that lived on the island of Mauritius. Due to the dodo being slow-moving and unafraid of humans, hunting became a major factor in its extinction. Although there may have been other contributing factors, such as disease, habitat loss and the introduction of new predators (e.g. dogs).