Evolution and Speciation Concepts in Biology

evolution

The change in the heritable characteristics of biological populations over successive generations.

paleontology

The scientific study of the history of life on Earth through the examination of plant and animal fossils.

binomial nomenclature

A formal system of naming species of living things by giving each a name composed of two parts.

Charles Darwin

An English naturalist known for his contributions to the understanding of evolution and natural selection.

Charles Lyell

A geologist who is known for his work in establishing the principles of geology and the concept of uniformitarianism.

Alfred Russel Wallace

A naturalist who independently conceived the theory of evolution through natural selection.

Jean Baptiste Lamarck

A biologist known for his early theory of evolution that proposed the inheritance of acquired characteristics.

HMS Beagle

The ship on which Charles Darwin made his famous voyage that contributed to his theory of evolution.

adaptation

A trait that helps an organism survive and reproduce in its environment.

biogeography

The study of the distribution of species and ecosystems in geographic space and through geological time.

natural selection

The process whereby organisms better adapted to their environment tend to survive and produce more offspring.

The Origin of Species

A book by Charles Darwin that introduced the scientific theory of evolution by natural selection.

artificial selection

The intentional reproduction of individuals in a population that have desirable traits.

Darwin's observations

The insights and findings made by Charles Darwin during his studies of species variations.

vestigial structure

A structure that has lost most or all of its original function in a species.

phylogeny

The evolutionary history and relationships among individuals or groups of organisms.

convergent evolution

The process where organisms not closely related independently evolve similar traits.

homologous/analogous structures

Homologous structures are similar due to shared ancestry, while analogous structures are similar due to convergent evolution.

microevolution

Small-scale evolutionary changes typically seen within a species.

genetic variation

Differences in DNA sequences among individuals within a population.

geographic variation

Differences in the genetic composition of populations that are separated by geographical barriers.

cline

A gradual change in a trait or characteristic over a geographical area.

population

A group of individuals of the same species that live in the same area and interbreed.

gene pool

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

Hardy-Weinberg

A principle that describes the genetic equilibrium within a population.

Hardy-Weinberg conditions

The five conditions required for a population to be in Hardy-Weinberg equilibrium: no mutations, random mating, no natural selection, extremely large population size, and no gene flow.

genetic drift

Random changes in allele frequencies in a population, often having a significant effect in small populations.

founder effect

A form of genetic drift that occurs when a small group of individuals establishes a new population.

bottleneck effect

A sharp reduction in the size of a population due to environmental events or human activities.

gene flow

The transfer of genetic variation from one population to another.

five fingers of microevolution

A mnemonic for the five agents of microevolution: mutation, gene flow, genetic drift, non-random mating, and natural selection.

fitness

The ability of an organism to survive and reproduce in its environment.

sexual selection

A mode of natural selection where typically members of one gender choose mates of the other gender.

directional selection

A type of natural selection that favors one extreme phenotype over the mean or other extreme.

disruptive/diversifying selection

A type of selection that favors extreme values for a trait over intermediate values.

stabilizing selection

A type of natural selection that favors average phenotypes and selects against extremes.

sexual dimorphism

The differences in appearance between male and female members of the same species.

intra/intersexual selection

Intrasexual selection involves competition among the same sex, while intersexual selection involves mate choice.

neutral variation

Genetic variation that does not confer a selective advantage or disadvantage.

balancing selection

A type of natural selection that maintains genetic diversity in a population.

heterozygote advantage

When heterozygous individuals have a higher fitness than homozygous individuals.

speciation

The process by which new and distinct species evolve.

biological species

A group of individuals that can interbreed and produce fertile offspring.

reproductive isolation

A set of conditions that prevent members of different species from interbreeding.

prezygotic/postzygotic barriers

Prezygotic barriers prevent mating or fertilization, while postzygotic barriers occur after fertilization.

hybrids

Offspring resulting from the cross-breeding of two different species.

allopatric speciation

Speciation that occurs when populations are geographically isolated.

sympatric speciation

Speciation that occurs without geographic separation.

polyploidy

The condition of having more than two complete sets of chromosomes.

hybrid zone

A region where two different species meet and mate, producing hybrid offspring.

gradualism

The theory that evolution occurs slowly and steadily over long periods of time.

punctuated equilibrium

The theory that evolution is marked by long periods of stability interrupted by brief periods of rapid change.

macroevolution

Large-scale evolutionary changes that occur over long periods of time.

protocells

Simple vesicle-like structures that are thought to be precursors to living cells.

radiometric dating/half-life

A method used to date materials by comparing the abundance of a radioactive isotope to its decay products.

ribozymes

RNA molecules that can catalyze chemical reactions.

fossil record

The history of life as documented by fossils.

geologic record

The history of Earth as recorded in the layers of rock.

stromatolites

Layered structures formed by the activity of microorganisms, particularly cyanobacteria.

endosymbiosis

The theory that certain organelles in eukaryotic cells originated as symbiotic prokaryotes.

Cambrian explosion

A period of rapid diversification of life forms that occurred approximately 541 million years ago.

plate tectonics

The theory that the Earth's outer shell is divided into several plates that glide over the mantle.

Pangea

A supercontinent that existed during the late Paleozoic and early Mesozoic eras.

mass extinction

A widespread and rapid decrease in the biodiversity on Earth.

adaptive radiations

The rapid evolution of diversely adapted species from a common ancestor.

heterochrony

An evolutionary change in the timing or rate of developmental events.

Hox genes

A group of genes that control the body plan of an embryo along the head-tail axis.

phylogenetic tree

A diagram that represents evolutionary relationships among various biological species.

homology

The existence of shared ancestry between a pair of structures, or genes, in different taxa.

analogy

The similarity in function of body parts that have different evolutionary origins.

clade

A group of organisms that includes an ancestor and all its descendants.

monophyletic

A group of organisms that consists of a common ancestor and all its lineal descendants.

shared derived characters

Traits that are shared by a group of organisms and are derived from a common ancestor.

domains

The highest taxonomic rank in the hierarchical biological classification system.

outgroup

A group of organisms that is used as a reference group when determining the evolutionary relationships among a set of organisms.

horizontal gene transfer

The transfer of genetic material between organisms in a manner other than traditional reproduction.