9th Grade Biology - Evolution and Natural Selection (copy)

Evolution

Evolution

the process of change in a population over time

Adaptation

a characteristic that improves an organism's chance of survival

Fitness

ability to survive and improving their chance to pass on their genes to the next generation

Evidence for evolution

fossils, homologous structures, vestigial structures

Homologous structures

Similar structure resulting from common ancestry but different function

Vestigial structures

useless structures (snake and whale leg bones, human appendix) that were used by ancestors

Lamarks Theory of Evolution

organisms have an internal drive to become more perfect, and can selectively use and disuse parts of their body throughout their life. These acquired characteristics can then be passed onto offspring.

Directional Selection

when conditions favor individuals exhibiting one extreme of a phenotype

Stabilizing Selection

when conditions favor the most common phenotype

Disruptive selection

when conditions slop to favor the different extreams

Genetic drift

a random change of population

Founder effect

when a small number of individuals leave a large population to colonize a new area and bring with them only a small amount of genetic variation

Bottleneck effect

genetic drift occurs because of a natural disaster that wipes out the most individuals by chance, affects smaller populations

reproductive barriers

When species can not reproduce because of their genes

behavioral barriers

2 populations that are capable of interbreeding develop differences in courtship rituals or other behaviors

geographic barriers

2 populations are separated by geographic barriers

time barriers

Species reproduce at different times

Anatomy barriers

When species' bodies cannot reproduce based on anatomy

Cladograms

models that show possible evolutionary relationships between species

Common ancestor

The shared ancestor of species

natural selection

A process resulting in the evolution of organisms best fitted to the environment that can survive and pass on genes in a population

Analogous structures

Body parts in a species that share a common function, but not structure meaning they do not share a common ancestor

Speciation

the formation of new species in the course of evolution.