Evolution Evidence shows that the earliest living things on Earth were very simple organisms. In the billions of years that have passed, organisms have become more and more complex. Many species have become extinct and others have taken their place. A species is a group of organisms that look alike and can reproduce among themselves. Most scientists believe that new species develop from older species as a result of gradual change, or evolution. Evolution is the process by which living things over time.
Adaptations Living things can be found everywhere on earth, from the highest mountaintops to the deepest oceans, and from hot, dry desert to polar ice caps. Some bacteria live in rocks 1,609 m deep in Earth’s crust. How do different organisms survive such a wide variety of conditions?
Mutations Species evolve over time. Generally, a change in a species is caused by genetics. The each new generation, there is a new combination of genes. In time, new species can develop that will be different from their ancestors. Such changes take place over a very long period of time. These changes are needed to adapt to new environments.
Sometimes, however, something may cause a gene to change suddenly. A sudden change in the gene is called a mutation. If the mutation is helpful to the organism, it may be kept and passed on to the future generations. Eventually, the species changes. This may result in the evolution of a new species. If the mutation is harmful, the individual will probably die without passing the trait on.
The white python in the picture is an albino. Albino organisms do not have any pigments in their skin. It is a harmful mutation.
4-1 What is evolution?
Write true if the statement is true. If the statement is false, change the underlined term to make the statement true.