Ecology and Evolution

allele frequency

the rate at which a specific allele appears within a population

Georges Cuvier

paleontologist that was the first to formally recognize extinction

Charles Darwin

conceived and described (independently with Alfred Russel Wallace) natural selection as a mechanism for evolution

evolution

change in allele frequencies of a population across generations

fitness

an individual’s ability to survive and reproduce

fossil

the preserved remains (body fossils) or traces (trace fossils) of organisms from prehistoric time

homology

similarity between species due to inheritance from a common ancestor

James Hutton

geologist that proposed that geological change occurs gradually by accumulating small changes from processes like erosions and uplift

Jean Baptiste de Lamarck

He proposed inheritance of acquired characteristics as the mechanism for evolution. Although the theory was flawed, it was an important step toward describing how evolution could occur.

Law of Superposition

layers of rock are arranged in a time sequence, with younger layers near top

Charles Lyell

A geologist who shared the gradualism view of Hutton, played a role in the joint publication of the theory of natural selection

macroevolution

broader scale evolutionary changes that scientists see over paleontological time

Malthusian catastrophe

occurs when population size exceeds resource availability, leading to intense competition and crash of population size

Gregor Mendel

A geneticist who first described many characteristics of heredity

microevolution

changes in a population’s genetic structure over short time scales (as little as one generation to the next)

modern synthesis

An overarching evolutionary paradigm that took shape by the 1940s, and scientists generally accept today

permineralization

fossilization process in which minerals enter dead organic material and forms an internal cast

Nicholas Steno

first to formally recognize that fossils are the remains of organisms

transitional feature

A trait in a fossil that is intermediate between ancestral (older) and derived (newer) species

vestigial structure

physical structure present in an organism, but has no (or little) apparent function, and appears to be from a functional structure in a distant ancestor

Alfred Russel Wallace

conceived and described (independently with Charles Darwin) natural selection as a mechanism for evolution

adaptation

heritable trait or behavior in an organism that aids in its survival and reproduction in its present environment

artificial selection

deliberate manipulation of fitness by humans through selective breeding

directional selection

selection that favors phenotypes at one end of the spectrum of existing variation

diversifying selection

selection that favors two or more distinct phenotypes

frequency-dependent selection

selection that favors phenotypes that are either common (positive frequency-dependent selection) or rare (negative frequency-dependent selection)

Rosemary and Peter Grant

study Darwin’s finches on the Galapagos Islands and have measured evolution by natural selection over short time scales

good genes hypothesis

theory of sexual selection that argues individuals develop impressive ornaments to show off their efficient metabolism or ability to fight disease

handicap principle

theory of sexual selection that argues only the fittest individuals can afford costly traits

heredity

the transmission of genetic characteristics from parent to offspring

heritability

fraction of population variation that can be attributed to its genetic variance

honest signal

trait that gives a truthful impression of an individual’s fitness

natural selection

the non-random and differential reproduction of different genotypes acting to preserve variants and to eliminate less favorable variants

pleiotropy

when a single gene affects multiple traits

polygenic trait

a trait that is controlled by multiple genes

relative fitness

individual’s ability to survive and reproduce relative to the rest of the population

selective pressure

environmental factor that causes one phenotype to be better than another

sexual dimorphism

phenotypic difference between a population’s males and females

sexual selection

selection that favors phenotypes that increase ability to obtain or choose good mates

stabilizing selection

selection that favors average phenotypes

4 processes of natural selection

variation, inheritance, overproduction/struggle for survival (competition), differential survival & reproduction (adaptation)

bottleneck effect

magnification of genetic drift as a result of natural events or catastrophes

founder effect

event that initiates an allele frequency change in part of the population, which is not typical of the original population

genetic drift

effect of chance of a population’s gene pool

migration (gene flow)

flow of alleles in and out of a population due to the movement of individuals or gametes

mutations

changes to an organism’s DNA; changes that have no effect on fitness are neutral and those that reduce fitness are deleterious