Key Concepts in Evolution and Natural Selection

Evolution

Populations change over time

Population

A group of organisms from same species in a particular area

Species

Similar organisms capable of interbreeding to create a viable offspring

Gene Pool

Set of genes found in a population

Gene Frequency

Frequency of allele in a population

Genetic Drift

How allele frequencies change as a result of random events

Adaptation

A genetic trait that aids survival and reproduction

Fitness

A measure of success of an organism to survive and reproduce

Polygenic Traits

Many genes determine these traits

Directional Selection

Individuals at one end of the phenotypes have great fitness

Stabilizing Selection

Medium phenotype is best fit for environment

Disruptive Selection

Individuals at opposite ends of phenotypes spectrum are most fit

Niche

An organism's 'job or 'role' in the environment

Hardy-Weinberg Equilibrium

If a population is in HW equilibrium it does not see a change in allele frequency from one generation to the next.

Allele Frequency Equation

P + Q = 1

Genotype Frequency

P2 + 2PQ + Q2 = 1

Speciation

Reproductive isolation is the most common way

Allopatric Speciation

A population becomes physically separated by a physical geographic barrier

Sympatric Speciation

Behavioral barriers (i.e. different mating dances)

Coevolution

Closely interacting species evolve together

Convergent Evolution

Species not closely related that change and adapt in similar ways

Divergent Evolution

Two or more related groups of species become more and more dissimilar due to different habitats

Adaptive Radiation

Is what happens when many species evolve and adapt from a common ancestor.

Gradualism

Darwin's idea that species change slowly and gradually over time

Punctuated Equilibrium

Fossils records support that species are stable for periods of time and then change rapidly