What is Evolution

In biology, evolution is the change in the characteristics of a species over several generations and relies on the process of natural selection.

The theory of evolution is based on the idea that all species are related and gradually change over time.
Evolution relies on there being genetic variation in a population which affects the physical characteristics (phenotype) of an organism.
Some of these characteristics may give the individual an advantage over other individuals which they can then pass on to their offspring.

What is natural selection?
Charles Darwin’s theory of evolution states that evolution happens by natural selection.
Individuals in a species show variation in physical characteristics. This variation is because of differences in their genes?.
Individuals with characteristics best suited to their environment are more likely to survive, finding food, avoiding predators and resisting disease. These individuals are more likely to reproduce and pass their genes on to their children.
Individuals that are poorly adapted to their environment are less likely to survive and reproduce. Therefore their genes are less likely to be passed on to the next generation.
As a consequence those individuals most suited to their environment survive and, given enough time, the species will gradually evolve.

Different types of evolution
Convergent evolution
When the same adaptations evolve independently, under similar selection pressures.
For example, flying insects, birds and bats have all evolved the ability to fly, but independently of each other.

Co-evolution
When two species or groups of species have evolved alongside each other where one adapts to changes in the other.
For example, flowering plants and pollinating insects such as bees.

Adaptive radiation
When a species splits into a number of new forms when a change in the environment makes new resources available or creates new environmental challenges.
For example, finches on the Galapagos Islands have developed different shaped beaks to take advantage of the different kinds of food available on different islands.