Termionology

Population

The general definition of population is all the inhabitants of a particular place, however, in terms of biology it is a name given to a group of individuals of organisms which can be interbred. It is important to understand what is population in order to understand how genetic population works and what organisms are a population.

Population Genetics Introduction

Population genetics contains the study of the factors which contribute and cause changes in allele frequencies. Allele frequency is how often a certain alleles appear within a population. There are five main elements which contribute to change in allele frequency; natural selection, sexual selection, mutation, genetic drift and gene flow.

Natural Selection

Natural selection is highly linked to the theory of evolution. As organisms evolve their alleles evolve with them, alleles that produce new traits within the organism that enables it to survive better than other organisms in the population. They are then able to pass on their new more successful alleles to be passed onto the next generation. This therefore means that alleles for fitter organisms become more frequent. This can also be done in a none natural manner using genetic manipulation.

Sexual Selection

Sexual selection occurs when the organism decides who to breed with for example an organism which appears to be stronger is more likely to be desired than an organism that isn’t. This means that alleles for more sexually attractive organisms become more frequent.

Mutation

Genetic mutation occurs during meiosis, a cell alleles is damaged during the transfer process. People often associate mutation as a bad thing which hinders an organism and its chance for survival; however, genetic mutations can be highly helpful and aid survival.

For example an artic fox was originally brown, but a mutation occurred which caused a selected few to be born with white fur. The white fur made it more difficult for predators to spot the fox, making the white furred fox a better survivor compared to the original coloured fox and the white furred fox went on to reproduce and the gene carried on to next generations.

Genetic Drift

Genetic drift, also known as allelic drift is the changes in allele frequency due to random chance. Genetic drift usually occurs within small populations as the chance is a lot higher and it happens a lot quicker due to the smaller amount of organisms in the population, random fluctuations appear in the gene pool, and it is assumed that it is purely chance rather than natural selection. Those genes are then passed on causing the gene pool to drift away from the original genes. Genetic drift does not cause organisms to become fitter or weaker but simply different.

Gene Flow

Gene flow also known as gene migration causes changes in the allele frequency due to the exchange of genes between to interbreeding populations. This happens when organisms interbreed with other organisms which are from a different population who have their own allele frequencies which differ.

An example of when gene flow occurs is when organisms are forced to migrate into a different area due lack of vegetation or changes in the environment and are forced/ able to breed with other animals outside of their population.