A fossil is any evidence from an animal or plant that lived ages ago
The basic idea behind the theory of evolution is that all the different species have evolved from simple life forms. These simple life forms first developed more than three billion years ago - the Earth is about 4.5 billion years old.
The theory of evolution states that evolution happens by natural selection. Here are the key points:
- Individuals in a species show a wide range of variation.
- This variation is because of differences in genes.
- Individuals with characteristics most suited to the environment are more likely to survive and reproduce.
- The genes that allowed the individuals to be successful are passed to the offspring in the next generation.
Individuals that are poorly adapted to their environment are less likely to survive and reproduce than those that are well adapted. Similarly, it is possible that a species that is poorly adapted to its environment will not survive and will become extinct.
A species can become extinct by:
- changes to the environment, such as a change in climate
- new diseases
- new predators
An organism's DNA can change (called a mutation). Most of the time, mutations have no effect.
Charles Darwin came up with the idea of Natural Selection.
Whereas Lemarck came up with the idea of 'aquired characteristics' this meant that over a long period of time the changes have just been made and happened through mutations.