1) gene flow
- it is described as the transfer of genes from one population to another population so that frequency of gene is increased.
-a zebra migrates to join a different herd of zebras.
2) natural selection
- a mechanism of evolutionary change in which individuals with advantageous traits survive and reproduce whereas the others ( those that can not adapt) eliminate from the population.
-competition for sunlight leads to taller trees.
- permanent change in the nucleotide sequence of dna ( genetic material) that could have harmful or useful consequences.
-the dna of a snake changes to make its venom stronger.
4) genetic drift - it is a random phenomenon ( that occurs by chance such as fire) that results in change in the gene frequency in a small population.
-a grassfire randomly sweeps through a population of buffalo and kills most of the animals.