Category: Biology Dictionary

Binary fission : The process by which one prokaryotic cell divides into two identical daughter cells.

 Bile : A dark green to yellowish-brown fluid, produced by the liver of most vertebrates, which aids the digestion of lipids in the small intestine. Also called gall.

Behavioral ecology : The study of the evolutionary basis for animal behavior due to ecological pressures.

Basal body : An organelle formed from a centriole, and a short cylindrical array of microtubules. Also called a basal granule, a kinetosome, and in older cytological literature, a blepharoplast.

Barr body : The inactive X chromosome in a female somatic cell, rendered inactive in a process called lyonization, in those species in which sex is determined by the presence of the Y chromosome (including humans) or W chromosome rather than by the presence of two X chromosomes or two Z chromosomes.

Bacteriophage : A virus that infects and multiplies within bacteria.

Bacteria : An enormous and diverse clade of microscopic, prokaryotic, single-celled organisms which lack a true nucleus. They represent one of the three fundamental biological domains.

B cell : A type of lymphocyte in the humoral immunity of the adaptive immune system.

Autotroph : Sometimes used interchangeably with primary producer.

An organism capable of producing complex organic compounds from simple substances present in its surroundings, generally by using energy from sunlight (as in photosynthesis) or from inorganic chemical reactions (as in chemosynthesis). Autotrophs do not need to consume another living organism in order to obtain energy or organic carbon, as opposed to heterotrophs.

Autoimmunity : The system of immune responses of an organism directed against its own healthy cells and tissues.

Astrobiology : The branch of biology concerned with the effects of outer space on living organisms and the search for extraterrestrial life.

Asexual reproduction : A type of reproduction involving a single parent that results in offspring that are genetically identical to the parent.

Artificial selection : Also called selective breeding.

The process by which humans use animal breeding and plant breeding to selectively control the development of particular phenotypic traits in organisms by choosing which individual organisms will reproduce and create offspring. While the deliberate exploitation of knowledge about genetics and reproductive biology in the hope of producing desirable characteristics is widely practiced in agriculture and experimental biology, artificial selection may also be unintentional and may produce unintended (desirable or undesirable) results.

Arachnology : The scientific study of spiders, scorpions, pseudoscorpions, and harvestmen, collectively called arachnids.

Apoptosis : A highly regulated form of programmed cell death that occurs in multicellular organisms.

Antibiotic : Also called an antibacterial.

A type of antimicrobial drug used in the treatment and prevention of bacterial infections.

Animal : Any member of a clade of multicellular eukaryotic organisms belonging to the biological kingdom Animalia. With few exceptions, animals consume organic material, breathe oxygen, are able to move, reproduce sexually, and grow from a blastula during embryonic development. An estimated 7 million distinct animal species currently exist.

Anatomy : The branch of biology that studies the structure and morphology of living organisms and their various parts.

Analogous structures : A set of morphological structures in different organisms which have similar form or function but were not present in the organisms’ last common ancestor. The cladistic term for the same phenomenon is homoplasy.

Amniote : An organism which produces an egg composed of a shell and membranes that creates a protected environment in which the embryo can develop outside of water.

Amino acid : A class of organic compounds containing an amine group and a carboxylic acid group which function as the fundamental building blocks of proteins and play important roles in many other biochemical processes.

Allopatric speciation : A form of speciation which occurs when biological populations of the same species become isolated from each other to an extent that prevents or interferes with genetic interchange.

Alga : (pl.) algae Any member of a diverse polyphyletic group of photosynthetic, eukaryotic, mostly aquatic organisms ranging from simple unicellular microalgae to massive colonial or multicellular forms such as kelp. Algae may reproduce sexually or asexually, and are often compared to plants, though they lack most of the complex cell and tissue types that characterize true plants.

Agrobiology : The study of plant nutrition and growth, especially as a way to increase crop yield.

Agriculture : The practice of cultivating land, growing food, and/or raising livestock.

Aerobiology : The study of organic particles which are passively transported by the air, including bacteria, fungal spores, very small insects, pollen grains, and viruses.

Aerobic : Capable of surviving and growing in the presence of oxygen.

Adipose tissue : A type of loose connective tissue made of mostly adipocytes and found in human and animal tissue, where it is colloquially known as body fat.

Adenosine triphosphate (ATP) : An organic compound derived from adenine that functions as the major source of energy for chemical reactions inside living cells. It is found in all forms of life and is often referred to as the “molecular currency” of intracellular energy transfer.

Adenine : A purine-derived organic compound which is one of the four canonical nucleobases used in the nucleic acids DNA and RNA. Its derivatives are involved in a wide variety of biochemical reactions, including cellular respiration.

Adaptive radiation: The process by which organisms diversify rapidly from an ancestral species into a multitude of new forms, particularly when a change in the environment makes new resources available, creates new challenges, or opens new niches

Active transport : Transport of a substance (such as a protein or drug) across a cell membrane against a concentration gradient. Unlike passive transport, active transport requires an expenditure of energy.

Active site : The part of an enzyme or antibody at which substrate molecules bind and undergo a chemical reaction.

Activation energy : The energy that an atomic system must acquire before a process (such as an emission or reaction) can occur.

Action potential : The local change in voltage that occurs when the membrane potential of a specific location along the membrane of a cell rapidly depolarizes, such as when a nerve impulse is transmitted between neurons.

Acetyl-CoA : A molecule that participates in many biochemical reactions in protein, carbohydrate, and lipid metabolism, notably the citric acid cycle.

Acclimatization : Adaptation to a new climate, as with a new temperature or altitude or environment.

Absorption spectrum : The spectrum of electromagnetic radiation that has passed through a medium which absorbs radiation of certain wavelengths.

Absorption : A process in which one substance permeates another. A fluid permeates or is dissolved by a liquid or solid. Skin absorption is a route by which substances can enter the body through the skin.

Abscission: The shedding of flowers, leaves, and/or fruit following formation of scar tissue in a plant.

Abiotic component : Any non-living chemical or physical part of the environment that affects living organisms and the functioning of ecosystems, such as the atmosphere and water resources.

Monoculture : The practice of growing or raising a single crop or livestock species, variety, or breed on a particular area of land at a time. Contrast polyculture.