Lesson 5 - Mechanisms of Evolution

Only mutations within sex cells can be passed on

New alleles

When populations are small, chance fluctuations can cause changes in allele frequencies. When mating is nonrandom, individuals that are preferred mates will pass on more alleles. Mutations may cause new alleles to be created or changed, causing a change in allele frequency. Migration will remove alleles from one population and add them to another Natural selection causes certain alleles to be passed on increasing the relative frequency of alleles in the next generation.

Increment of change is small compared to time

Increment of change is large compared to time

most common phenotypes within a population are most favoured

environment favours individuals with more extreme variations

variations at opposite extremes

favours the selection for any trait that influences the mating success of the individual

small changes accumulate over time because of their selective advantage

Changes to allele frequency as a result of chance.

severe event results in a drastic reduction in numbers very small sample of alleles survives to establish a new population

Genetic drift that results when a small # of individuals separate from their original population.

The movement of alleles from one population to another through the movement of individuals.

on DNA in units called GENES. Genes are located at specific LOCI

All individuals of the same species share a common GENOME (complete set of chromosomes) However, each will have a different GENOTYPE (Combination of alleles at specific loci).