Microevolution

Mutations

Are changes in the DNA of an organism

Genetic Drift on small populations Can affect the evolution of populations in 2 ways: Second Way

Can lead to the fixation of alleles that are neutral, harmful, or beneficial. Only natural selection consistently leads to adaptive evolution.

The main causes of microevolution are

Gene flow. Genetic drift. Mutations. Natural selection

Genetic drift

Is a change in the gene pool of a small population due to chance.

A population

Is a group of individuals of the same species living in the same place at the same time. Is the smallest biological unit that can evolve.

The bottleneck effect

Is an example of genetic drift. Results from a drastic reduction in population size. Can threaten the survival of populations Bottlenecking in a population usually reduces genetic variation.

Gene flow

Is genetic exchange with another population. Tends to reduce genetic differences between populations.

Individual variation abounds in populations

Not all of this variation is heritable. Only the genetic component of variation is relevant to natural selection.

Mutations and sexual recombination

Produce genetic variation

Genetic Drift on small populations Can affect the evolution of populations in 2 ways: One way

Reduces genetic variation within small populations because chance alone eventually causes one of the alleles to reach fixation. This occurs at a faster rate in small populations compared to large populations.

Sexual recombination

Shuffles alleles during meiosis

Microevolution refers to these changes in allele frequencies over time.

The frequencies of alleles in populations can change from generation to generation

Microevolution

small-scale evolutionary changes

Genotype frequency-

the proportion or percentage in a population of a genotype, such as AA, Aa, or aa.

Allele frequency

the proportion or percentage in a population of a particular allele, such as A or a allele.

To determine if a population is evolving

we need to look at the allele frequencies.

Evolution

change in the genetic characteristics of a population of organisms over timePopulations evolve, not individuals

Population genetics

Focuses on populations as the evolutionary units. Tracks the genetic makeup of populations over time

The founder effect

Is genetic drift in a new colony.

Microevolution is defined as

A generation-to-generation change in a population's frequencies of alleles. Variation exists among individuals in a population. Much of this variation is heritable.