Evidence for Evolution and Natural Selection

Vocabulary flashcards covering the definition of evolution, lines of evidence including structural, developmental, molecular, and vestigial homologies, transitional forms, and the mechanism of natural selection.

Evolution (genetic definition)

The change in allele frequency in a population over time.

The Theory of Evolution

The proposition that all organisms on Earth are related by common ancestry (unity) and have changed over time (diversity), characterized as "descent with modification" from a common ancestor.

Homologies (Homologous features)

Similarities among organisms that are due to inheritance from common ancestors.

Structural homologies

Similarities in body parts of adults from different species that occur because of common ancestry, such as vertebrate forelimbs.

Analogous structures

Structures that may be similar due to environmental constraints rather than recent common ancestry, such as insect wings and bat wings.

Developmental homology

Similarity in embryonic form or developmental processes due to common ancestry.

Cellular/molecular homology

Similarity in DNA sequences (genes) due to common ancestry and a common genetic code across species used for expressing amino acids and building proteins.

Vestigial structures

Body parts with reduced or no function in one species that are similar to functioning structures in an ancestral or closely related species, such as the human appendix, snake pelvic bone and "legs," and wings in flightless birds.

Transitional forms

"Intermediate" forms in the fossil record found between the ancestral trait and the more recent version, such as whale nostril location and human skulls.

Natural selection

A mechanism of evolution where heritable random variation exists in a population, and individuals with traits well suited to an environment survive and reproduce more, passing on their alleles at a higher rate and shifting allele frequency for genes under selective pressure.

Reproductive fitness

A measure of reproductive success tied to a particular environmental context, where a trait may grant high fitness in one environment but low fitness in another.