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theory

a widely accepted explanation of a biological phenomenon based on sound evidence from rigorous empirical experiments and scientific observations.

fitness

the quantitative representation of individual reproductive success. It is also equal to the average contribution to the gene pool of the next generation, made by the same individuals of the specified genotype or phenotype.

competition

Competition is an interaction between organisms or species in which both require a resource that is in limited supply. Competition lowers the fitness of both organisms involved since the presence of one of the organisms always reduces the amount of the resource available to the other

adaptation

 the dynamic evolutionary process of natural selection that fits organisms to their environment, enhancing their evolutionary fitness

descent with modification

passing traits from parent to offspring, 

natural selection

 the differential survival and reproduction of individuals due to differences in phenotype. It is a key mechanism of evolution, the change in the heritable traits characteristic of a population over generations

variation

 **any difference between cells, individual organisms, or groups of organisms of any species caused either by genetic differences** ...

speciation

when a group within a species separates from other members of its species and develops its own unique characteristics.

gene pool

 the combination of all the genes (including alleles) present in a reproducing population or species.

artificial selection

the identification by humans of desirable traits in plants and animals, and the steps taken to enhance and perpetuate those traits in future generations.

sexual selection

theory in postulating that the evolution of certain conspicuous physical traits—such as pronounced coloration, increased size, or striking adornments—in animals may grant the possessors of these traits greater success in obtaining mates.

genetic equilibrium

The condition where a gene pool is not changing in frequency across generations 

gradualism

a pattern of sustained, directional, and incremental evolutionary change over a long period during the history of a species.

punctuated equilibrium

the hypothesis that evolutionary development is marked by isolated episodes of rapid speciation between long periods of little or no change.

gene flow

he transfer of genetic material from one population to another

immigration

 an animal establishes a home in a habitat because it has resources it can utilize or because the habitat is ideal for them. 

emigration

an animal leaves its home because the habitat is no longer ideal for them and they need to find a more suitable environment.

bottleneck effect

 the way in which a reduction and subsequent increase in a population's size affects the distribution of genetic variation among its individuals.

coevolution

**the process of reciprocal evolutionary change that occurs between pairs of species or among groups of species as they interact with one another** ...

vestigial structures

a feature that a species inherited from an ancestor but that is now less elaborate and functional than in the ancestor.

analogous structures

features of different species that are similar in function but not necessarily in structure and which do not derive from a common ancestral feature (compare to homologous structures) and which evolved in response to a similar environmental challenge.

homologous structures

similar physical features in organisms that share a common ancestor, but the features serve completely different functions

biogeography

biogeography

endosymbiotic theory

 a class of hypotheses that view various organelles in eukaryotic cells as descendants of endosymbionts

fossils

the geologically altered remains of a once-living organism and/or its behaviour