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Extinction is when an entire population of a particular creature disappears from Earth. Though it sounds drastic, extinctions are quite common in Earth’s history. Scientists believe that 99 per cent – over five billion species that ever lived – have become extinct since the beginning of life. This could have happened due to reasons of lack of food or disastrous events like asteroids hitting Earth. In recent times, the speed at which species are becoming extinct has increased due to human activity. |
The most common cause of extinction is a sudden, serious change in a species’ habitat. A habitat is the surroundings in which an animal lives. Animals can rarely survive such sudden change. Their food supply may be wiped out. They may also lose shelter or other things that they need to survive.
Many things can change a species’ habitat. Floods, fires, droughts, volcanoes, and other natural events may be causes. People also change the environment in ways that drastically affect animals. People clear forests and drain wetlands. They build dams that disrupt the flow of rivers. They build cities on land that animals need to survive. They also create harmful pollution.
Some changes that cause extinction affect only a small area. Others are large enough to affect the entire world. A fire or other local event may cause the extinction of animals that live only in that region. A sudden change in the global climate might wipe out an animal species that lives in many parts of the world.
People can cause extinctions more directly as well. Some species have been hunted to extinction. The passenger pigeon is one example of this. Humans killed millions of the birds over many years. The last one died in the early 1900s.
Dinosaurs first appeared on Earth about 215 million years ago. They were the most important land animals for more than 150 million years. By 65 million years ago, however, the dinosaurs had died out.
Many scientists believe that a large asteroid, or rock from space, caused this mass extinction. When the asteroid hit Earth, the impact caused drastic changes. Thick dust and other materials blocked the sun. Temperatures dropped, and plants could not grow. The dinosaurs could not survive the cold temperatures and lack of food. But early species of birds and mammals did survive.
Credit: Kids Britannica
Picture Credit : Google
