Bio 30: Chap 19 pt2 Causes of Gene Pool Change

Genetic Diversity

• degree of genetic variation within a species/population

> high genetic diversity = more variation

> low genetic diversity = less variation

Mutations/ Genetic mutations

• changes that occur in the DNA of an indv

• germ-line ( gametes ) mutation had the potential to affect an entire gene pool

> some are harmful, beneficial, neutral

• Back mutations > reverses effects of former mutations

• inheritable mutations may diversify a gene pool

!! more genetic variation in a population = greater chance that a variation will be present & provide a selective advantage in a changing environment

Gene Flow

• net movement of alles from one population to another, due to the MIGRATION of individuals

> increases genetic diversity, but reduced genetic differences

> + genetic variety, - genetic differences (share many of the same alleles)

Non-random mating

• choosing mates based off their physical and behavioural traits

> preferred phenotypes

> inbreeding: closely related indv mate together

.. increases frequency if homozygous genotypes

.. positive effect if the homo recessive indvs fail to breed and no harmful recessive traits are in the gene pool

.. negative effect in the sense that purebred farm animals = prone to deformities & health problems

Genetic Drift

• change in allele frequencies due to the chance events in a small population

!! SMALL populations are more likely to lose alleles from its gene pool than a large population

founder effect

• gene pool change thet occurs when a few indv start a new isolated population

> limits genetic diversity, for it does not typically represent all the alleles from the original population

Bottleneck effect

• gene pool change that results from a rapid decrease in population size

> usually form natural disasters, disease, etc

.. when a population declines = some indv dont survive, but those that survive are left w/ a limited set of genes

USUALLY SEEN IN SPECIES CLOSE TO EXTINCTION

natural selection

• process of adaptation and evolution

  > indv with greater/beneficial traits are favoured and passed onto next gen (survival advantage)

• ENVIRONMENT is what makes certain mutations relatively beneficial, netural, harmful

• !! if a populations gene pool is small = lacking genetic diversity.. population may be unable to adapt to envt changes

Sexual selection

• form of non-random mating

> survival advantages show why some lethal recessive alleles remain in the human gene pool rather than being eliminated overtime

> alleles related to genetic health conditions = provide heterozygous advantage: harmful recessive allele provides an advantage to survival over homo dom alleles

Human Activities

• habitats = fragmented when humans convert large stretches of wilderness into human-made barriers