Evolution unit- nelson biology 11: definitions

Extinct

Describes a species that has completely disappeared from the earth

Adaptation

A structure behaviour, or physiological process that helps an organism survive and reproduce in a particular environment

Mimicry

A structural adaptation in which a harmless species resembles a harmful species in coloration or structure

Variation

Differences between individuals, which may be structural, functional, or physiological

Selective advantage

A genetic advantage that improves an organism’s chance of survival, unusually in a changing environment

Natural selection

The process by which characteristics of a population change over many generations as organisms with heritable traits survive and reproduce, passing their traits to their offspring

Selective pressure

Environmental conditions that select for certain characteristics of individuals and against other characteristics

Fitness

The relative contribution an individual makes to the next generation by producing offspring that will survive long enough to reproduce

Artificial selection

Selective pressure exerted by humans on populations in order to improve or modify particular desirable traits

Biotechnology

The use of technology and organisms to produce useful products

Monoculture

Extensive plantings of the same varieties of a species over a large plot of land

Catastrophism

The idea that catastrophes such as floods, diseases, and droughts periodically destroyed species in a region, allowing for new species to repopulate the area

Uniformitarianism

Charles Lyell’s theory that geological processes operated at the same rates in the past as they do today

Inheritance of acquired characteristics

The idea that characteristics acquired during an organisms lifetime can be passed onto their offspring

Theory of evolution by natural selection

Theory explaining how life has changed, and continues to change

Evolution

The process of genetic change in a population over time

Survival of the fittest

The idea that the fittest organisms leave the most offspring

Descent with modification

Darwin’s theory that natural selection does not demonstrate progress, but merely results from a species ability to survive at a specific time

Fossil record

The remains and traces of past life that are found in sedimentary rock; it reveals the history of life on Earth and the kinds of organisms that were alive in the past

Transitional fossil

A fossil that shows links between two groups of organisms

Vestigial structure

A structure that is a reduced version of a structure that used to be functional in an organisms lifetime can (ex: leg bones in a whale)

Biogeography

The study of the past and present geographical distributions of species populations

Homologous structures

Structures that have similar structure and origin but different function

Analogous structures

Structures of organisms that do not have a common origin but perform the same function

Embryology

The study of early, pre-birth of an organisms development

Gene flow

The net movement of alleles from one population to another due to the migration of individuals

Non random mating

Mating among individuals on the basis of mate selection for a particular phenotype due to inbreeding

Genetic drift

The change in frequencies of alleles due to chance events in a breeding population

Founder effect

A change in a gene pool that occurs when a few individuals start a new isolated population

Bottleneck effect

Changes in gene distribution that result from a rapid decrease in population size

Stabilizing selection

Natural selection that favours intermediate phenotypes and reacts against extreme variants (A normal mouse does better than a fat mouse and a frail mouse)

Directional selection

Natural selection that prefers one extreme of a phenotype (Humans with more endurance last longest)

Disruptive selection

Natural selection that favours the extremes of a range of phenotypes over intermediate phenotypes (Small salmon are good at sneaking for access to females eggs while large salmon are good at fighting for access to females eggs)

Sexual selection

Natural selection for mating based in competition between males for females

Speciation

The formation of new species from existing species

Pre-zygotic isolating mechanism

a barrier that either impedes mating between species or prevents fertilization of the eggs if individuals from different species attempt to mate; also called pre-fertilization barrier

Post zygotic isolating mechanism

a barrier that prevents hybrid zygotes from developing into viable, fertile individuals; also called post-fertilization barrier

sympatric speciation

speciation in which populations within the same geographical areas diverge and become reproductively isolated

allopatric speciation

speciation in which a population is split into two or more isolated groups by a geographical barrier; also called geographical speciation

ecological niche

the ecological role and physical distribution of a species in its environment

adaptive radiation

the diversification of a common ancestral species into a variety of differently adapted species

divergent evolution

a pattern of evolution in which species that were once similar to an ancestral species diverge, or become increasingly distinct

convergent evolution

a pattern of evolution in which similar traits arise because different species have independently adapted to similar environmental conditions

gradualism

a model of evolution that views evolutionary change as slow and steady, before and after a divergence

punctuated equilibrium

a model of evolution that views evolutionary history as long periods of stasis, or equilibrium, that are interrupted by periods of divergence