Natural Selection / Key Terms

Natural Selection

Explains changes in a population that occur when organisms with favorable variations survive.

Survival of the fittest

Some organisms have an advantage over others.

Results in adaptations that allow populations to survive in their environments.

Natural Selection Trends

Trends may occur in different directions; decreasing a species or increasing a species.

Increasing the genotype and phenotype may result in a new species.

Natural Selection - Definition

The process by which forms of life having traits that better enable them to adapt to specific environmental pressures, as predators, changes in climate, or competition for food or mates, will tend to survive and reproduce in greater numbers than others of their kind, thus ensuring the perpetuation of those favorable traits in succeeding generations.

Fitness - Definition

The genetic contribution of an individual to the next generation's gene pool relative to the average for the population, usually measured by the number of offspring or close kin that survive to reproductive age.

Adaptation - Definition

Any alteration in the structure or function of an organism or any of its parts that results from natural selection and by which the organism becomes better fitted to survive and multiply in its environment.

Traits - Definition

A distinguishing characteristic or quality.

Survival of The Fittest - Definition

Natural Selection

"A 19th-century concept of human society, inspired by the principle of natural selection, postulating that those who are eliminated in the struggle for existence are the unfit."

Descent with Modification - Definition

Change in the genetic composition of a population during successive generations, as a result of natural selection acting on the genetic variation among individuals, and resulting in the development of new species.

Speciation - Definition

The formation of new species as a result of geographic, physiological, anatomical, or behavioral factors that prevent previously interbreeding populations from breeding with each other.

Genetic Variation - Definition

Level of biodiversity, refers to the total number of genetic characteristics in the genetic makeup of a species

Adaptive Radiation - Definition

A process in which organisms diversify rapidly into a multitude of new forms, particularly when a change in the environment makes new resources available and opens environmental niches.

Convergent Evolution - Definition

Describes the independent evolution of similar features in species of different lineages.

Geographic Evolution - Definition

how species evolve, disperse, and diversify across changing landscapes over time

Gradualism - Definition

Belief that change ought to be brought about in small, discrete increments rather than in abrupt strokes such as revolutions or uprisings.

Punctuated Equilibrium - Definition

Theory in evolutionary biology which proposes that most species will exhibit little net evolutionary change for most of their geological history, remaining in an extended state called stasis.

Cladogram - Definition

Approach to biological classification in which items are grouped together based on whether or not they have one or more shared unique characteristics that come from the group's last common ancestor and are not present in more distant ancestors.

Extinction - Definition

The end of an organism or of a group of organisms.

Vestigial - Definition

Occurring or persisting as a rudimentary or degenerate structure.

Reproductive Isolation - Definition

Collection of mechanisms, behaviors and physiological processes that prevent the members of two different species that cross or mate from producing offspring

Mutation - Definition

A sudden departure from the parent type in one or more heritable characteristics, caused by a change in a gene or a chromosome.

Genetic Drift - Definition

Random fluctuations in the frequency of the appearance of a gene in a small isolated population, presumably owing to chance rather than natural selection.

Genetic Recombination - Definition

Production of new combinations of alleles, encoding a novel set of genetic information