Biology

Brachiozoa — the clade uniting brachiopods and phoronids Brachiozoa Brachiozoa is a lophotrochozoan clade that groups brachiopods and phoronids, marine lophophore-bearing animals with distinct anatomies, ecological roles, and a rich fossil and evol…

Bracket fungi (shelf fungi): characteristics, ecology, and human uses Bracket fungus Bracket fungi (shelf fungi) are wood-inhabiting basidiomycetes that form shelf- or bracket-shaped fruiting bodies. They play key roles in wood decay, forest ecology, and have tradi…

Brain: structure, function, and biological significance Brain An overview of the brain — its main parts, cellular components, functions, protection, evolution, and why it matters for behaviour, cognition and health.

Brain cell (neurons and glia) Brain cell Overview of brain cells: the neuron and glial families, their structure and functions, development and plasticity, and clinical significance in health and disease.

Brain stem: structure, functions, and clinical importance Brain stem Overview of the brain stem—its anatomy (midbrain, pons, medulla), core functions in autonomic control and cranial nerves, clinical significance, development, blood supply, and dist…

Branchiobdellida — leech-like annelids associated with crayfish Branchiobdellida Branchiobdellida are small clitellate annelids that live on freshwater crustaceans, especially crayfish. They range from mutualists to parasites and are studied for host–symbiont e…

Breast (human anatomy and function) Breast An overview of the human breast: anatomy, development, functions such as lactation, sex differences, common health issues, and cultural significance, with links to related topics.

Breast augmentation Surgical and autologous methods to increase breast volume, including implants and fat grafting; indications, techniques, risks, recovery, and long-term considerations.

Breastfeeding: physiology, benefits, challenges and public health importance Breastfeeding Breastfeeding is feeding an infant with milk from the mother's breasts. This article explains how breastfeeding works, milk composition, benefits, common difficulties, contraindica…

Breath sounds: types, how they are heard, clinical significance Breath sounds Breath sounds are noises produced by airflow in the airways and lungs. This article explains normal and abnormal sounds, how clinicians listen for them, common causes, and the role…

Breathing: how air moves through the lungs and sustains life Breathing Breathing is the continuous process of moving air into and out of the lungs to deliver oxygen and remove carbon dioxide. This article explains how breathing works, its control, var…

Breed — distinct types of domesticated animals and plants Breed A breed is a defined group within a domesticated species, shaped by selective breeding for traits such as appearance, behaviour, productivity, or hardiness. This article explains m…

Broca's area: brain region involved in speech and language production Broca's area Broca's area is a region of the dominant frontal lobe associated with speech production and certain language functions; clinically linked to expressive aphasia and studied with mod…

Bronchiole: small airways of the lung Bronchiole Bronchioles are the smallest air-conducting passages in the lungs that lack supportive cartilage; they lead to alveoli and play a central role in airflow regulation and gas exchang…

Bronchus: anatomy, function, development, and clinical significance Bronchus Comprehensive overview of the bronchus: anatomy, microstructure, development, physiology, blood supply, clinical conditions, diagnosis and common treatments. Highlights differences…

Brood parasitism Brood parasitism is a reproductive strategy in which one species tricks another into incubating and raising its young. Found in birds, fish and insects, it drives mimicry, coevolut…

Bryology: the study of mosses, liverworts and hornworts Bryology Bryology is the scientific study of bryophytes — mosses, liverworts and hornworts — covering their biology, ecology, classification, uses, and methods used by researchers and conse…

Bubo: Inflamed lymph node associated with infection and reactive lymphadenopathy Bubo A bubo is a swollen, tender lymph node arising from infection or inflammation. Historically linked to plague, buboes occur in inguinal, axillary, or cervical regions and require cl…

Budding (asexual reproduction) Budding Budding is a form of asexual reproduction in which a new individual develops from an outgrowth of the parent, producing genetically identical offspring in many plants, fungi and so…

Bulbourethral gland (Cowper's gland) Bulbourethral gland Small paired glands in the male pelvic floor that secrete a lubricating fluid into the urethra prior to ejaculation; also known as Cowper's glands and analogous to Bartholin's glan…

Burping (Eructation): Causes, Social Meaning, and Health Notes Burping Burping (eructation) is the release of gas from the stomach through the mouth. Overview of causes, physiology, social norms, prevention, and when to seek medical advice.

Burrow (animal-made hole and tunnel) Burrow A burrow is a hole or tunnel in the ground created by animals as shelter, nest, refuge or storage. Varied in size and complexity, burrows occur across many animal groups and substr…

Burst kinetics in enzymology Burst kinetics Burst kinetics describes a transient rapid phase of product formation by enzymes before a slower steady-state rate; used in pre-steady-state studies to reveal rate-limiting steps i…

Butterfly net (aerial insect net) Butterfly net A lightweight hoop-and-bag net used to catch butterflies and other flying insects; designed to protect delicate wings and adapted in size, mesh and handle for different collecting…

Byssus: mollusc attachment threads and the rare textile 'sea‑silk' Byssus Byssus refers to the bundle of silky filaments some bivalves use to anchor themselves and to the rare textile known as sea‑silk, historically prized and now rare and protected.

Calvin cycle Biochemical pathway in chloroplast stroma that fixes atmospheric CO2 into triose phosphates using ATP and NADPH from the light reactions; central to C3 photosynthesis and many auto…

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…

Campylobacter — common bacterial cause of gastroenteritis Campylobacter Campylobacter is a genus of curved, motile bacteria commonly carried by animals and a leading cause of bacterial gastroenteritis in humans; transmitted chiefly via contaminated pou…

Candidatus: provisional names for uncultured bacteria and other prokaryotes Candidatus Candidatus is a provisional taxonomic label for prokaryotes known from molecular, microscopic, or ecological evidence but not maintained in pure culture. It signals an incompletely…

Capillary (microvessel) Capillary Smallest blood vessels in animals that permit exchange of gases, nutrients and fluids between blood and tissues; single-cell endothelial walls with several specialised types.

Capsid (viral protein shell) Capsid A capsid is the protein shell that encloses a virus's genetic material. This article outlines its structure, assembly, biological roles, types, and relevance for medicine and biote…

Biological carbon fixation: pathways, mechanisms, and ecological significance Carbon fixation Overview of biological carbon fixation: enzymatic pathways (Calvin cycle, reverse TCA, Wood–Ljungdahl), mechanisms of CO2 incorporation, where it occurs, and its ecological and bio…

Carcass: definition, decomposition, ecological role, and terminology Carcass A carcass is the dead body of an animal or human. This article explains the term, physical changes after death, ecological and practical roles, historical usage, and distinctions f…

Cardiac muscle (myocardium): structure, function, and clinical importance Cardiac muscle Cardiac muscle (myocardium) is the involuntary, striated muscle of the heart. This article explains its structure, cellular features, physiology, blood supply, embryology, and how…

Carnassial teeth Carnassial Carnassials are specialized shearing teeth of many meat-eating mammals, adapted for slicing flesh and crushing bone; they vary in position and form across groups and are important…

Carotenoids: natural pigments, functions, and significance Carotenoid Carotenoids are organic pigments in plants, algae, bacteria and fungi that harvest light, protect tissues from photooxidation, contribute to coloration and nutrition, and have indu…

Carpals (Wrist Bones): Structure, Function, and Clinical Notes Carpals The carpals are eight small bones that form the wrist. This entry summarizes their arrangement, articulations, function, development, common injuries, and useful clinical mnemonics…

Candidatus Carsonella ruddii: an obligate endosymbiont with a minimal genome Carsonella ruddii An overview of Candidatus Carsonella ruddii — its biology, extremely reduced genome, symbiotic role in psyllids, evolutionary implications and why it challenges definitions of bact…

Cartilage: structure, types, function, development and clinical importance Cartilage Cartilage is a flexible, avascular connective tissue that supports shape and motion. This article explains its types, cellular makeup, roles in growth and joints, and clinical issu…

Caste (biology) A caste is a specialized morphological or behavioral group within a social animal population—common in social insects—defined by role, reproductive status and development, and shap…

Castorimorpha: the beavers, pocket gophers and kangaroo rats Castorimorpha Castorimorpha is a suborder of rodents that includes semiaquatic beavers, burrowing pocket gophers and arid-adapted kangaroo rats. Overview of classification, anatomy, evolution, e…

Catabolism: the biochemical breakdown of molecules for energy Catabolism Catabolism is the component of metabolism that breaks down complex molecules into smaller ones, releasing energy used for cellular work, heat, and biosynthesis intermediates.

Cell (biology): structure, function, and main types Cell A concise encyclopedia overview of the biological cell: definition, key parts and organelles, major types (prokaryotic vs eukaryotic), reproduction, evolution, and why cells matter…

Cell Biology: structure, molecules, and cellular processes Cell biology A clear introduction to cell biology: its scope, principal molecules and organelles, origins of eukaryotic complexity, cell division, and the methods and importance of studying cel…

Cell differentiation: how cells acquire specialized identities Cell differentiation Cell differentiation is the process by which unspecialized cells become specialized in form and function, driven by regulated gene expression, signaling and epigenetic changes; ess…

Cell division: processes, types, and biological significance Cell division Overview of how cells divide, the cell cycle and its stages, mitosis and meiosis, regulation and biological roles including growth, repair, reproduction, and consequences of errors…

Cell Growth (Interphase): processes, regulation, and biological importance Cell growth Overview of cell growth during interphase: stages, molecular controls, differences from division, examples in development and disease, and common ways scientists study growth.

Cell membrane (plasma membrane): structure, function and diversity Cell membrane Overview of the cell (plasma) membrane: its structure, components, transport roles, variation among organisms, and biological importance.