Fossil turtle, Cretaceous Period. Many types of prehistoric organisms, such as ammonites, trilobites, dinosaurs and mammoths, are...Read More >>Fossil turtle, Cretaceous Period. Many types of prehistoric organisms, such as ammonites, trilobites, dinosaurs and mammoths, are now extinct. Other types, such as sharks and turtles, have survived almost unchanged for millions of years. Others have appeared quite recently, such as human beings. Fossils provide part of the evidence for evolution—the way that living things have changed through time. Over geological time—millions, or even hundreds of millions of years—the fossil record tells us that living things (organisms) have, very gradually, changed. Animals, for example, may have grown a fin or a tail, developed wings, or lost teeth. This is all part of a process by which living things adapt to their environment. This process is known as evolution. Variations within species mean that some individuals are better suited to their lifestyle than others. These individuals are more likely to survive and reproduce, passing on the features that helped them survive. However, conditions change naturally with time: some foods may become scarcer or the climate may change. Evolution may allow some living things to survive in the new conditions.
There are two living species of elephants, African and Asian. Fossils of huge bones, teeth and tusks resembling those of today’s...Read More >>There are two living species of elephants, African and Asian. Fossils of huge bones, teeth and tusks resembling those of today’s species show that many other kinds of elephants once roamed the Earth. Each type evolved to suit the conditions of its time, such as an ice age or a warm period. But it could not adapt as conditions continued to change and so died out. Why does evolution happen? Life is a continual struggle to avoid predators and bad weather, to find food and shelter, and to breed. Living things that survive the struggle are those best suited or adapted to the conditions. However these conditions change naturally with time. Some kinds of food may become more scarce. The climate may become colder or warmer. New diseases may appear. Living things must evolve to suit the new conditions or die out.
For thousands of years, humans have bred domestic animals or crops with “desirable” features to emphasize those features in the next generation. This is called “artificial selection”.
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