Evolution by natural selectionSpec 4.2
Evolution is a change in the inherited characteristics of a population over many generations. Darwin explained how it happens using natural selection.
- Individuals in a population show variation. Some of this is genetic, caused by differences in alleles, which arise by mutation.
- More offspring are born than can survive, so individuals compete for resources such as food, space and mates, and some are eaten or die of disease.
- Individuals with characteristics that suit their environment are more likely to survive and reproduce.
- They pass on the alleles for those characteristics to their offspring.
- Over many generations, the proportion of the population with the advantageous alleles increases.
Individuals with a characteristic that gives an advantage are sometimes described as the 'fittest'. This means best suited to their environment, not strongest.
- Natural selection
- The process by which organisms better adapted to their environment are more likely to survive, reproduce and pass on their alleles.
- Evolution
- A change in the inherited characteristics of a population over many generations.