Intraspecific Variation

Vasquez

Variation is the differences that occur between different individuals. There are two types;

Intraspecific – the differences that occur within a species.

Interspecific – the differences that occur between members of different species.

Variations can be recognised through physical appearance or genetic factors. The terms Genotype and Phenotype are used to describe these variations.

Intraspecific variation is caused by genetic and environmental factors;Intraspecific variation (variation that occurs within a species) can be caused by a number of environmental and genetic factors.

Genetic – all members of the same species have the same genes, however they have different forms of these genes called alleles. The different alleles cause variations in an organism’s phenotype (physical appearance). Examples of variation caused by genetic factors include eye colour and blood group. Genetic variation is inherited, as certain genetic factors can be passed on in families.

Environmental – the phenotype of an organism can also be affected by environmental factors. For example, plant growth is affected by the amount of minerals, such as nitrate and phosphate in the soil. Another example is Himalayan rabbits. These rabbits are affected by temperature. Their fur turns black when temperatures reach below 25 degrees.

Variation is often a combination of both genetic and environmental factors;

An example of this would be height. In animals, such as humans, genetics will decide the potential height that a person can grow, but environmental factors will decide whether that person will grow to their potential or not. Malnutrition or illness caused by environmental factors could cause a person not to grow to their full potential. Height usually runs in families.

Measuring genetic variation Measurement - Genetic variation within a population is commonly measured as the percentage of gene loci that are polymorphic or the percentage of gene loci in individuals that are heterozygous.

variation between populations – variation within populations

variation between populationsF st =

Hs – average heterozygosity in the subpopulationHt – average heterozygosity in the metapopulationFst – the reduction in heterozygosity that is due to the structure of the population

Genetic ecological processes

• Genetic drift – randam change of in allele frequencies in a population from generation to generation due to finite population size.

• Mutation - an error in the replication of DNA that causes a structural change in a gene. Only source of new genetic variation in populations (sex cells only).

• Gene Flow - exchange of genetic information among population via migration of individuals.

• Natural Selection – differential contribution of genotypes to the next generation due to differences in survival and reproduction.