Adaptation, Natural Selection and Evolution

the number of different alleles of genes in a population

an alternative form of a gene

Process by which species evolve. Results in species that are better adapted to their environment, adaptations may be anatomical, physiological or behavioural

Random mutation occurs resulting in new allele. This new allele is beneficial to the organism, so they are better adapted to survive. As a result they live longer and are more likely to reproduce Therefore the new beneficial allele is passed down to their offspring Over many generation the advantageous allele increases in frequency in the population

A change in the environment leads to a phenotype to the left or right of the mean being best suited to survive, reproduce and pass on their alleles. As a result the mean of the population moves in the direction of the favoured phenotype. Example: tall giraffes best suited to survive, so they have greater reproductive success so the mean height of the population of giraffes increases.

Stable environmental conditions result in the phenotypes closest to the mean being favoured. As a result those with phenotypes closer to the mean are more likely to survive, reproduce and pass on the allele. Phenotypes towards the extreme are likely to be eliminated. Example: human birth weights, too large and too small risky for survival of baby, so the phenotype causing the mean birth weight is favoured as they are more likely to survive, reproduce and pass on their alleles