Evolutionary biology

Evolution is the change in the heritable characteristics of biological populations over successive generations. It occurs when evolutionary processes such as genetic drift and natural selection act on genetic variation, resulting in certain characteristics becoming more or less common within a population over successive generations. The process of evolution has given rise to biodiversity at every level of biological organisation.

thumb|right|Bust of the paleontologist Georges Cuvier (left) and a cast skeleton of [[Palaeotherium magnum (named by Cuvier in 1804, right), Cuvier Museum of Montbéliard]]

differential survival and reproduction of individuals in nature due to differences in phenotype; a key mechanism of evolution

thumb|The thylacine (Thylacinus cynocephalus) is an example of a recently extinct [[species.]] thumb|Palaeotherium is an example of an extinct [[genus that is only recorded from fossil records before the existence of hominids.]]

thumb|Three major single-chromosome mutations: deletion (genetics)|deletion (1), duplication (2) and inversion (3).

thumb|Honey bee|Honeybee workers perform the [[waggle dance to indicate the range and direction of food.]] thumb|Great crested grebes perform a complex synchronised [[courtship display.]] thumb|Male impalas fighting during the rut

thumb|400px|A comparison of phylogenetic and phenetic (character-based) concepts Systematics is the study of the diversification of living forms, both past and present, and the relationships among living things through time. Relationships are visualized as evolutionary trees (synonyms: phylogenetic trees, phylogenies). Phylogenies have two components: branching order (showing group relationships, graphically represented in cladograms) and branch length (showing amount of evolution). Phylogenetic trees of species and higher taxa are used to study the evolution of traits (e.g., anatomical or mol

organism that consists of more than one cell

In genealogy and evolutionary biology, an ancestor, also known as a forefather, fore-elder, or a forebear, is a parent or (recursively) the parent of an antecedent (i.e., a grandparent, great-grandparent, great-great-grandparent and so forth). Ancestor is "any person from whom one is descended. In law, the person from whom an estate has been inherited."

offspring of cross-species reproduction

thumb|upright=2|Stages in the origin of life process range from the well understood, such as the planetary habitability|habitable Earth and the abiotic synthesis of simple molecules, to the largely unknown, like the derivation of the [[last universal common ancestor (LUCA) with its complex molecular functionalities.]]

study of the processes that produced the diversity of life

variation in the relative frequency of different genotypes in a small population

Cladistics ( ; from Ancient Greek 'branch') is an approach to biological classification in which organisms are categorized in groups ("clades") based on hypotheses of most recent common ancestry. The evidence for hypothesized relationships is typically shared derived characteristics (synapomorphies) that are not present in more distant groups and ancestors. However, from an empirical perspective, common ancestors are inferences based on a cladistic hypothesis of relationships of taxa whose character states can be observed. Theoretically, a last common ancestor and all its descendants constitut

widespread and rapid decrease in the amount of life on earth

Speciation is the evolutionary process by which populations evolve to become distinct species. The biologist Orator F. Cook coined the term in 1906 for cladogenesis, the splitting of lineages, as opposed to anagenesis, phyletic evolution within lineages. Charles Darwin was the first to describe the role of natural selection in speciation in his 1859 book On the Origin of Species. He also identified sexual selection as a likely mechanism, but found it problematic.

branch of psychology

subfield of genetics that deals with genetic differences of populations, part of evolutionary biology

Sociobiology is a field of biology that aims to explain social behavior in terms of evolution. It draws from disciplines including psychology, ethology, anthropology, evolution, zoology, archaeology, and population genetics. Within the study of human societies, sociobiology is closely related to evolutionary anthropology, human behavioral ecology, evolutionary psychology, and sociology.

resistance of microbes to drugs directed against them

A karyotype is the general appearance of the complete set of chromosomes in the cells of a species or in an individual organism, mainly including their sizes, numbers, and shapes. Karyotyping is the process by which a karyotype is discerned by determining the chromosome complement of an individual, including the number of chromosomes and any abnormalities. thumb|Micrographic karyogram of human male using [[Giemsa staining]] thumb|Schematic karyogram demonstrating the basic knowledge needed to read a karyotype A karyogram or idiogram is a graphical depiction of a karyotype, wherein chromosomes

set of all genes in a population

thumb|Early embryos of various species display some ancestral features, like the tail on this human embryo. These features normally disappear in later development, but it may not happen if the animal has an atavism.

Psychological ethological theory about human relationships

most recent common ancestor of all current life on Earth

thumb|upright=1.5|The pollinating wasp Dasyscolia ciliata in [[pseudocopulation with a flower of Ophrys speculum]] In biology, coevolution occurs when two or more species reciprocally affect each other's evolution through the process of natural selection. The term sometimes is used for two traits in the same species affecting each other's evolution, as well as gene-culture coevolution.

shared ancestry of organisms from different species

Macroevolution comprises the evolutionary processes and patterns which occur at and above the species level. In contrast, microevolution is evolution occurring within the population(s) of a single species. In other words, microevolution is the scale of evolution that is limited to intraspecific (within-species) variation, while macroevolution extends to interspecific (between-species) variation. The evolution of new species (speciation) is an example of macroevolution. This is the common definition for 'macroevolution' used by contemporary scientists. However, the exact usage of the term has v

thumb| axons|Giant axons of the [[longfin inshore squid (Doryteuthis pealeii) were crucial for scientists to understand the action potential.]]

Neoteny (), also called juvenilization, is the delaying or slowing of the physiological, or somatic, development of an organism, typically an animal. Neoteny in modern humans is more significant than in other primates. In progenesis or paedogenesis, sexual development is accelerated.

type of speciation caused by geographic isolation between populations

closest relative(s) of another given taxon in a phylogenetic tree

series of neighboring populations, each of which can interbreed with closely sited populations, but for which the 2 end populations in the series are too distantly related to interbreed, despite potential gene flow between each linked population

loss of genetic variation that occurs when a new population is established by a very small number of individuals

most recent individual from which all organisms in a group are directly descended

accumulation of differences between closely related species populations, leading to speciation

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processes by which organisms evolved on Earth

the evolutionary strategy that favours the reproductive success of an organism's relatives, even at a cost to the organism's own survival and reproduction

220px|thumb|right|The American lobster#Coloration|blue lobster, an example of a mutant thumb|right|220px|Wild-type Physcomitrella patens|Physcomitrella and [[knockout mosses: Deviating phenotypes induced in gene-disruption library transformants. Physcomitrella wild-type and transformed plants were grown on minimal Knop medium to induce differentiation and development of gametophores. For each plant, an overview (upper row, scale bar corresponds to 1 mm) and a close-up (bottom row, scale bar equals 0.5 mm) is shown. A, Haploid wild-type moss plant completely covered with leafy gametophores and

form of phyletic dwarfism

organic compound that is not directly involved in the normal growth, development, or reproduction of an organism

thumb|right|Vein skeleton of a Hydrangea leaf showing anastomoses of veins

similar development of a trait in distinct species that are not not closely related, in response to similar evolutionary pressure

theory in evolutionary biology

geometric symmetry in living beings

thumb|upright=2.2|In the theory of symbiogenesis, a merger of an archaean and an aerobic bacterium created the eukaryotes, with aerobic mitochondria; a second merger added [[chloroplasts, creating the green plants. The original theory by Lynn Margulis proposed an additional preliminary merger, but this is poorly supported and not now generally believed.]] Symbiogenesis (endosymbiotic theory, or serial endosymbiotic theory) is the leading evolutionary theory of the origin of eukaryotic cells from prokaryotic organisms. The theory holds that mitochondria, plastids such as chloroplasts, and possi

the ability of an organism to change its phenotype in response to the environment

evidence demonstrating that all life on Earth comes from a single ancestor

informal grouping of taxa

process through which new species evolve from a single ancestral species while inhabiting the same geographic region

thumb|Bee pollinating a flower thumb|Soldier beetle covered with pollen

thumb|upright|Friedrich Leopold August Weismann, considered the "founder of Neo-Darwinism" for expanding Darwin's theory along genetic lines thumb|upright|George John Romanes originally used Neo-Darwinism in 1895 to refer to an early modification of Darwin's theory. Photograph by Elliott & Fry (1896)

transition of human species to anthropologically modern behavior

thumb|upright=2|Charles Darwin's pangenesis theory postulated that every part of the body emits tiny particles called gemmules which migrate to the [[gonads and are transferred to offspring. Gemmules were thought to develop into their associated body parts as offspring matures. The theory implied that changes to the body during an organism's life would be inherited, as proposed in Lamarckism.]]

monophyletic closure of a set of living species

evolutionary mechanism for speciation

A protocell (or protobiont) is a self-organized, membrane-bound or membraneless compartment that concentrates biomolecules, proposed as a rudimentary precursor to cells during the origin of life. A central question in evolution is how simple protocells first arose and how their progeny could diversify, thus enabling the accumulation of novel biological emergences over time (i.e. biological evolution). Although a functional protocell has not yet been achieved in a laboratory setting, the goal to understand the process appears well within reach.

theoretical conditions under which life on earth might have begun

gradual variation of the characteristics of a species along its territory