Glossary: the evolutionary causes of biodiversity

All of the following terms appear in the videos or articles for this tutorial on the evolutionary causes of biodiversity. The terms are arranged here in alphabetical order, and nouns are given in just their singular form unless the plural of the term is unusual.

acid: any liquid or substance with a pH less than 7

adaptation: a physical or behavioral trait of an organism that makes it well-suited to its environment and more likely to survive and reproduce

allele: one of several forms of the same gene that carries the genetic information (codes) for a particular trait

artificial selection: selection by humans for a desired trait or combination of traits in a type of organism by controlling which individuals are allowed to produce offspring

biodiversity: the variety of life on Earth or some specified geographic area of the planet; the diversity of life occurs at the genetic level, at the species level, at the ecosystem level, and in evolutionary lineages

cell: the smallest structural and functional unit or part of an organism; all living organisms are made up of one or more cells

cell division: the process in which one parent cell divides into two or more daughter cells

chromosome: the structure in the nucleus of a cell that contains the DNA; different species have different specific numbers of chromosomes

deoxyribonucleic acid (DNA): the molecule that carries genetic information in all living systems

divergence: in general, splitting or branching off in two directions; in evolution, refers to populations becoming more and more different from each other over time when the gene flow between them is restricted

evolution: the changes in heritable traits of a population over time

evolutionary: related to evolution, the changes in heritable traits of a population over time

evolutionary tree: a branching diagram that shows the evolutionary relationships between organisms based on similarities and differences of their physical and genetic characteristics; also known as a phylogenetic tree

fitness: a measure of the ability of an organism to survive and produce viable offspring in a particular environment; a measure of the reproductive success of an organism in a particular environment

gene: a segment of DNA at a specific location on a chromosome that is the basic unit of heredity; each gene controls some specific trait

genetic sequencing: the process of determining the precise order of nucleotides in a DNA molecule or DNA fragment

genetic variation: the diversity in the genetic information of a population or species; the variation comes from processes such as mutations and the shuffling of genes during the production of sex cells and their recombination at fertilization

mutation: a change in the genetic information of an organism; the nucleotide sequence is changed or the structure of the chromosome itself

nucleotide: the building block of DNA; each nucleotide contains the 5-carbon sugar deoxyribose, one of four different nitrogen-containing (nitrogenous) bases, and a phosphate group; there can be thousands of nucleotides in a single gene

phenotype: all the observable traits of an organism; determined by its genetic makeup and the influence of the environment

population: all the individuals of a particular species that live in a specific geographic area; a species may be made up of one or more populations

population size: the number of individuals in a particular population of organisms

species: a distinct type of organism

species richness: the number of different species in a given geographic area