microevolution

Microevolution

evolutionary change within a species or small group of organisms, especially over a short period.

what is the role of an individual in evolution?

the individual contributes to population level

species

individuals who reproduce together to make viable offspring

variation

differences in physical traits of an individual from the group to which it belongs (must be heritable for evolution)

continuous variation

variation along a whole spectrum
ex: human height

Discrete variation

variation in a heritable characteristic that has an either/or form, such as either being albino or not being albino

morphs

a visual or behavioral difference between organisms of distinct populations in a species

Polymorphism

The coexistence of two or more distinct forms in the same population.

Hardy-Weinberg Principle

principle that states that allele frequencies in a population remain constant unless one or more factors cause those frequencies to change
ex: bucket analogy: different genotypes and distribution of genes show that it has been changed

Requirements for maintaining equilibrium

1. no selection on that gene, equal fitness for all genotypes
2. random mating- each next generation individual with respect to gene
3. population needs to be big
4. no migration (no gene flow)
5. no mutations

Breaking "no natural selection" rule

rapid transmission rates and strong selection pressure (when only a few individuals can reproduce)

Breaking "mating is random" rule

nonrandom mating
- picks mate with better tail which increases the chance of that colorful tail to evolve in the species
- allele changes when similar people mate offer evolution and variation

assortative mating

the type of mating that occurs when an organism selects a mating partner that resembles itself

directional sexual Selection

"winning" strategy (better traits=more likely to get a mate)

Breaking "population sizes are large" rule

Genetic drift
- occurs in all populations, but is STRONGER on small populations
- once certain alleles are gone (if they die), they're GONE
- reduces genetic diversity
-maladaptive traits decrease until removed (loss of diversity)

genetic drift

A change in the allele frequency of a population as a result of chance events rather than natural selection.

Breaking "no mutation" rule

- change in nucleotide sequence (occurs during meiosis or mitosis in replication stage)
- mutations are raw material for evolution (variation leads to change over time)
- most mutations do NOT affect fitness

neutral mutation

most common. Not passed on and does not affect fitness

maladaptive mutation

decreases the likelihood of survival/reproduction in the individual expressing it (affects fitness!)

adaptive mutation

least common, novel trait

How can random mutations contribute to evolution of functional complex traits?

mutation provides variation, selection increases/decreases frequency