Biology: Evolution, Natural Selection, and Speciation Key Terms

Adaptation

a heritable trait that enhances an individual's fitness

adaptive radiation

The emergence of numerous species from a common ancestor introduced into an environment, presenting a diversity of new opportunities and problems.

Allele

alternative versions of a gene that produce distinguishable phenotypic effects.

allopatric speciation

A mode of speciation induced when an ancestral population becomes segregated by a geographic barrier or is itself divided into two or more geographically isolated subpopulations.

analogous structure

similar structures that evolved separately in different lineages

antibiotic resistance

the ability of a microorganism to resist the effects of an antibiotic to which they were once sensitive

artificial selection

the selective breeding of domesticated plants and animals to encourage the occurrence of desirable traits.

bottleneck effect

Genetic drift resulting from the reduction of a population, typically by a natural disaster, such that the surviving population is no longer genetically representative of the original population.

Cladogram

diagram depicting patterns of shared characteristics among species

Clades

a group of species that includes an ancestral species and all its descendants

common ancestor

an organism that is an ancestor of two different organisms that are not related to each other

convergent evolution

process whereby organisms, not closely related, independently evolve similar traits as a result of adapting to similar environment's

directional selection

Natural selection that favors individuals at one end of the phenotypic range.

disruptive selection

Natural selection that favors individuals on both extremes of a phenotypic range over intermediate phenotypes.

divergent evolution

process by which interbreeding populations or species diverges into two or more descendent species, resulting in becoming more dissimilar

emigration

movement of individuals out of a population

evolution

All the changes that have transformed life on Earth from its earliest beginnings to the diversity that characterizes it today

fertility

ability to produce offspring

founder effect

Genetic drift that occurs when a few individuals become isolated from a larger population, with the result that the new population's gene pool is not reflective of the original population.

gene flow

Genetic additions to or subtractions from a population resulting from the movement of fertile individuals or gametes.

gene pool

The total aggregate of genes in a population at any one time.

genetic drift

Unpredictable fluctuations in allele frequencies from one generation to the next because of a population's finite size.

homologous structures

structures in different species that are similar because of common ancestry

hybrid

an offspring that was given different genetic information for a trait from each parent

immigration

the influx of new individuals from other areas

isolation types

six different mechanisms that prevent the sperm and egg from coming together

limited resources

a resource which cannot be made available on a scale which can sustain its composition rate

mutation

A rare change in the DNA of a gene ultimately creating genetic diversity.

natural selection

Differential success in the reproduction of different phenotypes resulting from the interaction of organisms with their environment. Evolution occurs when natural selection causes changes in relative frequencies of alleles in the gene pool.

Outgroup

A species or group of species that is closely related to the group of species being studied, but clearly not as closely related as any study-group members are to each other.

Phenotype

the physical and physiological traits of an organism, which are determined by its genetic makeup

phylogenetic tree

A branching diagram that represents a hypothesis about evolutionary relationships.

Population

A localized group of individuals that belong to the same biological species (that are capable of interbreeding and producing fertile offspring).

Protobiont

An aggregate of abiotically produced molecules surrounded by a membrane or membrane-like structure

random mating

the choice of mates in which chance plays the biggest part

reproductive isolation

the existence of biological factors (barriers) that impede members of two species from producing viable, fertile hybrids

serial endosymbiosis

A model of the origin of eukaryotes consisting of a sequence of endosymbiotic events in which mitochondria, chloroplasts, and perhaps other cellular structures were derived from small prokaryotes that had been engulfed by larger cells.

sexual selection

natural selection for mating success

speciation

origin of new species in evolution

species

A group whose members possess similar anatomical characteristics and have the ability to interbreed.

stabilizing selection

natural selection that favors intermediate variants by acting against extreme phenotypes

sterility

incapable of producing offspring

sympatric speciation

a mode of speciation occurring as a result of a radical change in the genome of a subpopulation, reproductively isolating the subpopulation from the parent population

variation

differences between members of the same species

vestigial organs

Structures of marginal, if any, importance to an organism. They are historical remnants of structures that had important functions in ancestors.

Viability

capable of living