Avoiding extinction
If you look at rocks in the ground, you may find fossils in them. The fossils are the remains of plants and animals preserved in stone. Most fossils are formed from the hard parts of a living thing such as its bones or shell. When you look at the rocks in a cliff you can sometimes see that the rocks are arranged in layers ??like?the layers of bread and meat in a double beefburger. Each layer in the rocks may hold fossils. Generally, the lowest layers are older than the layers above them and each layer may take millions of years to form. This means that when you look at the fossils in the different layers you can see what living things were like at different times in the past.

As you look through the layers, starting at the bottom, you may find the fossils of a certain animal. You may find it for several layers and then it cannot be found any more no matter how high you look in the cliff. You cannot find it because the animal became extinct.

As you look in the higher layers, you may find new fossils which were not present in the lower layers. Scientists believe that these new fossils come from animals which newly developed at that time. The fossils may be found for several layers then suddenly they vanish, as you look in the highest layers. You cannot find them because they also have become extinct. The developing of new life forms and extinction are processes which have taken place on the Earth since life first began. They are natural processes.

In certain parts of the world tar forms naturally. It collects in tar pits. When animals fall into the tar, they die and their bodies become fossils. When scientists examined the fossils in tar pits they made a discovery. At the greatest depths there were fossils of a large number of different animals. As they moved up through the tar, the number of different animal fossils rapidly fell. This meant that a large number of animals were becoming extinct at the same time. This did not seem natural.

Scientist also discovered something else in the tar beside the fossils of animals. They found the remains of Stone Age tools made by humans. From this they found an explanation for the cause of so many extinctions. The animals began to become extinct when humans arrived in their habitats thousands of years ago. The humans hunted the animals until the animals became extinct. Today humans are causing the extinction of plants and animals but on a much larger scale than in the times of our Stone Age ancestors. Then the people did not know about extinction or what caused it. They simply wanted to survive. We want to survive too but we know much more about the world. We know enough to stop animals and plants becoming extinct. We must act now to save them.

When a living thing dies does it become extinct?
When an individual plant or animal dies it ceases to exist but we do not say it is extinct. We say it is dead. Living things are arranged into groups called species. In this group all the animals and plants are very similar and the males and females can breed together and produce offspring that can also breed. Nearly two million species have been identified on the planet and there may be a few more million yet to be discovered. Examples of plant species are the daisy, dandelion and oak. Examples of animal species are the lion, the chimpanzee and the human. We use the word extinction when all the members of a species die out. This means that there are no more males and females to produce offspring. The species has gone forever.

Why do living things become extinct naturally?
Every living thing has features that help it survive in a particular habitat. If conditions change in the habitat due to changes in the climate, then the living thing may not be able to survive. If this happens, all the members of the species die and the species becomes extinct.

Do extinctions occur steadily over a long time?
Yes, they do, but sometimes there are large numbers of extinctions at once. These extinctions are called mass extinctions. In the past they were caused by a major change in the climate of the Earth. The most famous mass extinction is the extinction of the dinosaurs, which happened sixty five million years ago. This is thought to have occurred because a large asteroid or comet hit the Earth. The collision brought widespread devastation and changed the Earth's climate so many animals and plants became extinct at once.

Is there a mass extinction occurring today?
Some scientists believe there is a mass extinction occurring. It is not due to a change in the climate but due to the activity of humans. They are causing the extinction of thousands of living things each year.

Why are humans causing such a huge rate of extinction?
They are causing it by destroying the habitats of many living things. The habitats are destroyed to make way for towns and farms. They are destroyed so we can gather raw materials such as wood. Forest habitats may also be cleared to obtain metal ores in the ground.

How fast are habitats being destroyed?
It varies, but one of the fastest disappearing habitats is the rainforest. Count one and two and three. In the time it took you to count, an area of rainforest the size of three football pitches has been destroyed. As you read the last sentence and this one, perhaps another area the size of five football pitches has been destroyed. This rate of destruction is going on every day of your life.

Can anything be done to slow down the rate of extinction?
Yes. The most useful thing to do would be for all countries to set aside large areas of land as wilderness areas. In these areas the habitats would not be destroyed by farms and towns or by digging up the ground to find metal ores. Wild animals would not be hunted and the numbers of living things would be checked regularly to see that they were surviving satisfactorily. Zoos have a use too. They can provide a secure environment in which very rare species could breed. This would increase the chances of the survival of the young. When the numbers of a rare species rise in a zoo, some can be returned to the wilderness areas.

Does it really matter that living things are becoming extinct so quickly?
Yes, it does. Living things in a habitat affect each other. A tree may provide shelter for an animal to rear its young. A particular insect may visit a particular plant and carry its pollen from flower to flower so the plant can breed. We know of many ways in which living things affect each other but we do not know them all. If we allow large numbers of living things to die out, we may find the way they were linked was so important that the rest of the living things, including ourselves, cannot survive without them.