UNITS 7 Natural Selection

natural selection

A population can change over time if individuals with more fit traits leave more offspring than less fit individuals.

artificial selection

Humans modifying species for desired traits through selective breeding.

fitness

Individuals whose inherited traits confer an advantage have a better chance of surviving in a given environment and will leave more offspring.

comparative embryology

Embryos of vertebrates share many anatomical homologies.

vestigial structures

Are of little or no importance to organisms, but remain from an ancestor.

biogeography

Geographic distribution of species.

population

Group of individuals of the same species living in the same area.

gene pool

All the genes in a given population at a given time.

Hardy-Weinberg Theorem

Helps measure changes in allele frequencies over time. Provides an 'ideal' population to use as a basis of comparison.

mutation

Changes in the nucleotide sequence in DNA.

sexual recombination

Crossing over and shuffling of genes during meiosis.

genetic drift

Change in allele frequencies due to chance.

bottleneck effect

When a population has been dramatically reduced, and the gene pool is no longer reflective of the original population's.

genetic variation

Heritable variations in a population.

directional selection

Shift toward a favorable variation.

disruptive selection

Shift toward the extremes.

stabilizing selection

Shift that favors the mean.

reproductive isolation

Barriers that impede members of two different species from producing fertile offspring.

temporal isolation

When two species breed at different times of day, season, or years.

behavioral isolation

Incompatible courtship rituals, pheromones, or bird songs.

mechanical isolation

Morphological differences prevent fertilization.

allopatric speciation

When a population is divided by some geographic barrier; leads to speciation.

sympatric speciation

Speciation without a divided population.

adaptive radiation

Evolution of many new species from a common ancestor as a result of introduction to new environments.

phylogeny

Evolutionary history of a species or group of species.

analogous structures

Anatomical similarity due to convergent evolution.

phylogenetic trees

Branching diagrams that depict hypotheses about evolutionary relationships.

cladogram

Diagram that shows patterns of shared characteristics.

Miller & Urey Experiment

Experiment that found that organic molecules can form in a strongly reducing atmosphere.

radiometric dating

Dating using decay of radioactive isotopes.