Evolutionary Biology

Adaptation (biology) Adaptation Adaptation is the evolutionary process by which populations become better suited to their environment through heritable changes. Covers mechanisms, types, examples, constraints and…

Adaptive radiation: rapid diversification of lineages Adaptive radiation Adaptive radiation is the rapid diversification of a lineage into multiple species that occupy different ecological roles, often after new opportunities, innovations, or extinction…

Ageing: biological mechanisms, evolutionary explanations, and societal effects Ageing A clear overview of ageing (senescence): its biological basis, evolutionary theories, population patterns, medical relevance, and distinctions between ageing, disease, and non‑agei…

Alfred Russel Wallace: naturalist, biogeographer and co-discoverer of natural selection Alfred Russel Wallace British naturalist (1823–1913) who independently proposed natural selection, mapped the Wallace Line, and pioneered biogeography through extensive fieldwork in the Amazon and Malay…

Allele: variant forms of a gene at a chromosomal locus Allele An allele is a specific variant of a gene at a particular location on a chromosome. Alleles determine genetic variation, influence traits, and are central to inheritance, populatio…

Amniote — Vertebrates Defined by the Amniotic Egg Amniote Amniotes are tetrapod vertebrates whose embryos develop with extraembryonic membranes (the amniotic egg), enabling a fully terrestrial life history; groups include mammals, birds a…

Amotz Zahavi: Israeli evolutionary biologist and originator of the handicap principle Amotz Zahavi Israeli evolutionary biologist Amotz Zahavi (1928–2017) proposed the handicap principle to explain honest biological signalling; he taught at Tel Aviv University and co-founded the…

Amphibian: biology, life cycle, evolution and conservation Amphibian Overview of amphibians (class Amphibia): major groups, anatomy, life cycle, fossil origins, diversity, habitats and modern conservation challenges.

Apomorphy (biology): derived traits and their role in phylogeny Apomorphy An apomorphy is a derived character state that distinguishes a clade. This article explains definitions, types (synapomorphy, autapomorphy), examples, phylogenetic use, and complic…

Archaea Archaea are a domain of microscopic single-celled life distinct from bacteria and eukaryotes, notable for unusual cell chemistry, early evolutionary importance, and many species ad…

B chromosome (supernumerary or accessory chromosome) B chromosome Extra chromosomes found in some individuals of a species that are not necessary for survival; often heterochromatic, variably inherited, and of evolutionary and ecological interest…

Beetle (Order Coleoptera): Diversity, Biology, and Importance Beetle Beetles (Coleoptera) are the largest order of insects, with hundreds of thousands of described species and great ecological, economic, and evolutionary significance worldwide.

Biological classification: principles, ranks, history and modern methods Biological classification Overview of biological classification (taxonomy): aims, hierarchical ranks, historical roots, modern phylogenetic methods, naming rules, species concepts, and practical uses in sci…

Butterfly: biology, life cycle, evolution, and human interactions Butterfly An accessible overview of butterflies: their classification, anatomy, life cycle, evolution with flowering plants, roles as pollinators, and human interest and conservation.

Cambrian explosion: rapid diversification of animal life in the early Paleozoic Cambrian explosion The Cambrian explosion refers to the relatively brief geological interval around 541 million years ago when most major animal body plans first appear in the fossil record, promptin…

Cephalopod (Cephalopoda): biology, evolution, behavior and human uses Cephalopod Cephalopods are a diverse class of marine molluscs—octopus, squid, cuttlefish and nautilus—known for intelligence, camouflage, jet propulsion and a rich fossil record including amm…

Charles Darwin's Books: scope, major works and lasting influence Charles Darwin's books Survey of Charles Darwin's principal books, their subjects, structure, historical context, and influence on sciences such as geology, zoology, botany and evolutionary biology.

Chelicerata: anatomy, evolution, diversity and ecological roles Chelicerata Chelicerata are a major arthropod subphylum including arachnids and horseshoe crabs, defined by chelicerae and a two-part body; they have a long fossil record and play key ecologic…

Cline (biology) — Gradients of variation across populations Cline A cline is a continuous change in a trait or gene frequency across geographic or environmental space, arising from selection, gene flow, and history. It helps explain adaptation, s…

Darwin's finches: Galápagos birds and a classic example of adaptive radiation Darwin's finches A concise overview of Darwin's finches: their diversity, distinctive beaks, role in the study of natural selection, later research, and their continuing importance for evolutionary…

Evolution (biological process) Evolution Biological evolution is the change in populations of organisms over generations through mechanisms such as natural selection, mutation and drift; it explains biodiversity, common a…

Monophyly in Evolutionary Biology: Defining Clades, Paraphyly, and Polyphyly Monophyly Overview of monophyly in evolutionary biology: what defines a clade and how paraphyly and polyphyly differ, with examples, classification implications, and molecular evidence.

Natural selection: the mechanism of adaptive evolution Natural selection Natural selection is the process by which heritable traits that improve survival or reproduction become more common in populations, driving adaptation and shaping biological divers…

Secondary sex characteristics: definition, examples, and significance Secondary sex characteristic Traits that distinguish the sexes of a species but are not directly part of the reproductive organs; includes examples, development at puberty, evolutionary roles, and human featur…

Tree of life (biology): evolutionary relationships and phylogenetic concepts Tree of life (biology) A summary of the biological 'tree of life' concept: its meaning, history, data and methods, limits such as horizontal gene transfer, and its uses in classification and research.