(4) WJEC A2 Biology 4.4 Evolution

Evolution

A change in the average phenotype of a population

Speciation

If the change in average phenotype of a population is profound enough, organisms with the altered phenotype are unable to reproduce sexually with initial pop. This is speciation: the formation of a new species.

The founder effect

When a small population is separated from the original population, it may have, by chance, a very different allele frequency compared to original. Thus, certain alleles become more frequent in the succeeding generations.

Population bottleneck

A sharp reduction in population e.g. due to disease. There may be too little genetic diversity left in the gene pool for the population to adapt therefore leading to extinction.