Evolution Study Guide

Gradualism

The idea that the Earth has been slowly shaped over time.

Uniformitarianism

The principle that geological processes today operated similarly in the past.

Catastrophism

The idea that Earth’s history has been shaped by sudden catastrophic events.

Inheritance of Acquired Traits

Lamarck’s incorrect idea that traits gained during life can be inherited.

Use and Disuse

Lamarck’s idea that body parts strengthen with use and weaken without use.

Population Pressure

Competition caused by populations growing faster than resources.

Extinction

The complete disappearance of a species.

Adaptation

An inherited trait that increases an organism’s chance of survival and reproduction.

Natural Selection

The process in which organisms with favorable traits survive and reproduce more successfully.

Variation

Differences among individuals in a population.

Fitness

An organism’s ability to survive and reproduce in its environment.

Speciation

The formation of new species over time.

Adaptive Radiation

The evolution of many species from a common ancestor to fill different ecological niches.

Selective Pressure

An environmental factor influencing survival and reproduction.

Survival of the Fittest

The idea that organisms best adapted to their environment reproduce more successfully.

Tree of Life

A diagram showing that all living species originally evolved from a single common ancestor, demonstrating descent with modification.

Fossil

Preserved remains or traces of ancient organisms.

Transitional Fossil

A fossil showing traits intermediate between ancestral and derived groups.

Homologous Structures

Structures with similar anatomy inherited from a common ancestor.

Analogous Structures

Structures with similar functions but different evolutionary origins.

Vestigial Structures

Reduced structures that have little or no current function.

Biogeography

The study of the geographic distribution of organisms.

Embryology

The study of embryos and their development.

Comparative Anatomy

The comparison of body structures among organisms.

Common Ancestry

The concept that organisms share evolutionary ancestors.

Convergent Evolution

The independent evolution of similar traits in unrelated organisms.

Coevolution

The process in which two species evolve in response to one another.

Mutualism

A relationship in which both species benefit.

Microevolution

Small-scale evolutionary change within populations.

Macroevolution

Large-scale evolutionary change above the species level.

Punctuated Equilibrium

Long periods of relatively little evolutionary change followed by periods of rapid speciation.

Directional Selection

Selection favoring one extreme phenotype.

Stabilizing Selection

Selection favoring average phenotypes.

Disruptive Selection

Selection favoring both extreme phenotypes.

Reproductive Isolation

The prevention of interbreeding between populations.

Behavioral Isolation

Isolation caused by differences in courtship or mating behaviors.

Geographic Isolation

Isolation caused by physical barriers such as mountains or rivers.

Temporal Isolation

Isolation caused by reproduction occurring at different times.

Mechanical Isolation

Isolation caused by incompatible reproductive structures.

Gametic Isolation

Isolation caused when gametes cannot successfully fuse.

Allopatric Speciation

Speciation due to geographic separation.

Sympatric Speciation

Speciation occurring without geographic separation.

Abiogenesis

The Theory of how Life could have arisen from previously non-living components.

Prokaryote

A simple cell lacking a nucleus (Includes Archaea and Bacteria).

Eukaryote

A cell containing a nucleus and membrane-bound organelles.

Cambrian Explosion

A period of rapid diversification of animal life.

Mass Extinction

A widespread event causing the extinction of many species.