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55 Cards in this Set
- Front
- Back
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In vertebrates, the portion of the trunk containing visceral organs other than heart and lungs; in arthropods, the posterior portion of the body, made up of similar segments and containing the reproductive organs and part of the digestive tract.
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abdomen
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Nonliving; specifically, the nonliving components of an ecosystem, such as temperature, humidity, the mineral content of the soil, etc.
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abiotic
[Gk. a, not, without + bios, life] |
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A plant hormone that generally acts to inhibit growth, promote dormancy, and help the plant tolerate stressful conditions.
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abscisic acid (ABA)
(ab-sis-ik) [L. ab, away, off + scissio, dividing] |
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In plants, the dropping of leaves, flowers, fruits, or stems at the end of a growing season, as the result of formation of a two-layered zone of specialized cells (the abscission zone) and the action of a hormone (ethylene).
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abscission
[L. ab, away, off + scissio, dividing] |
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The movement of water and dissolved substances into a cell, tissue, or organism.
absorption spectrum |
absorption
[L. absorbere, to swallow down] |
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The range of a pigment's ability to absorb various wavelengths of light.
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absorption spectrum
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abyssal zone
(uh-bis-ul) The portion of the ocean floor where light does not penetrate and where temperatures are cold and pressures intense. |
abyssal zone
(uh-bis-ul) |
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Physiological adjustment to a change in an environmental factor.
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acclimatization
(uh-kly-mih-ty-zay-shun) |
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The automatic adjustment of an eye to focus on near objects.
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accommodation
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One of the most common neurotransmitters; functions by binding to receptors and altering the permeability of the postsynaptic membrane to specific ions, either depolarizing or hyperpolarizing the membrane.
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acetylcholine
(asset-ill-coal-een) |
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The entry compound for the Krebs cycle in cellular respiration; formed from a fragment of pyruvate attached to a coenzyme.
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acetyl CoA
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A substance that increases the hydrogen ion concentration in a solution.
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acid
[L. acidus, sour] |
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Rain, snow, or fog that is more acidic than pH 5.6.
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acid precipitation
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A solid-bodied animal lacking a cavity between the gut and outer body wall.
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acoelomate
(a-seel-oh-mate) |
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An organelle at the tip of a sperm cell that helps the sperm penetrate the egg.
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acrosome
(ak-ruh-some) |
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Abbreviation of adrenocorticotropic hormone.
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ACTH
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A hormone, produced by the anterior lobe of the pituitary gland, that stimulates the production of cortisol by the adrenal cortex.
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adrenocorticotropic hormone (ACTH)
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A globular protein that links into chains, two of which twist helically about each other, forming microfilaments in muscle and other contractile elements in cells.
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actin
[Gk. aktis, a ray] |
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A rapid change in the membrane potential of an excitable cell, caused by stimulus-triggered, selective opening and closing of voltage-sensitive gates in sodium and potassium ion channels.
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action potential
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The energy that must be possessed by atoms or molecules in order to react.
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activation energy
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The specific portion of an enzyme that attaches to the substrate by means of weak chemical bonds.
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active site
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The movement of a substance across a biological membrane against its concentration or electrochemical gradient, with the help of energy input and specific transport proteins
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active transport
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(1) The evolution of features that make a group of organisms better suited to live and reproduce in their environment. (2) A peculiarity of structure, physiology, or behavior that aids the organism in its environment.
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adaptation
[L. adaptare, to fit] |
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An equilibrium state in a population when the gene pool has allele frequencies that maximize the average fitness of a population's members.
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adaptive peak
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The emergence of numerous species from a common ancestor introduced into an environment, presenting a diversity of new opportunities and problems.
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adaptive radiation
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A nucleotide consisting of adenine, ribose, and two phosphate groups; formed by the removal of one phosphate from an ATP molecule.
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adenosine diphosphate (ADP)
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A nucleotide consisting of adenine, ribose, and one phosphate group; can be formed by the removal of two phosphates from an ATP molecule; in its cyclic form, functions as a "second messenger" for a number of vertebrate hormones and neurotransmitters.
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adenosine monophosphate (AMP)
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An adenine-containing nucleoside triphosphate that releases free energy when its phosphate bonds are hydrolyzed. This energy is used to drive endergonic reactions in cells.
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adenosine triphosphate (ATP)
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An enzyme that converts ATP to cyclic AMP in response to a chemical signal.
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adenylyl cyclase
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Abbreviation of antidiuretic hormone.
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ADH
Abbreviation of antidiuretic hormone. |
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hormone important in osmoregulation.
antigen |
antidiuretic hormone (ADH)
[Gk. anti, against + diurgos, |
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A foreign macromolecule that does not belong to the host organism and that elicits an immune response.
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antigen
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The major artery in blood-circulating systems; the aorta sends blood to the other body tissues.
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aorta
(a-ore-ta) [Gk. aeirein, to lift, heave] |
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aphotic zone
The part of the ocean beneath the photic zone, where light does not penetrate sufficiently for photosynthesis to occur. |
aphotic zone
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Concentration of growth at the tip of a plant shoot, where a terminal bud partially inhibits axillary bud growth.
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apical dominance
(ay-pik-ul) [L. apex, top] |
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Embryonic plant tissue in the tips of roots and in the buds of shoots that supplies cells for the plant to grow in length.
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apical meristem
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A derived phenotypic character, or homology, that evolved after a branch diverged from a phylogenetic tree.
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apomorphic character
(ap-oh-more-fik) |
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In plants, the nonliving continuum formed by the extracellular pathway provided by the continuous matrix of cell walls.
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apoplast
(ap-oh-plast) |
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Programmed cell death brought about by signals that trigger the activation of a cascade of "suicide" proteins in the cells destined to die.
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apoptosis
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The bright coloration of animals with effective physical or chemical defenses that acts as a warning to predators.
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aposematic coloration
(ap-oh-so-mat-ik) |
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A transport protein in the plasma membranes of a plant or animal cell that specifically facilitates the diffusion of water across the membrane (osmosis).
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aquaporin
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A solution in which water is the solvent.
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aqueous solution
(ay-kwee-us) |
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Tree-dwelling.
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arboreal
[L. arbor, tree] |
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One of two prokaryotic domains, the other being the Bacteria.
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Archaea
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In plants, the female gametangium, a moist chamber in which gametes develop.
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archegonium pl. archegonia
(ar-kih-go-nee-um) [Gk. archegonos, first of a race] |
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The endoderm-lined cavity, formed during the gastrulation process, that develops into the digestive tract of an animal.
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archenteron
(ark-en-ter-on) [Gk. arch, first, or main + enteron, gut] |
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that includes diplomonads, such as Giardia; some systematists assign kingdom status to archezoans.
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Archezoa
Primitive eukaryotic group |
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A very small artery. See also artery.
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arteriole
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A vessel that carries blood away from the heart to organs throughout the body.
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artery
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A cardiovascular disease caused by the formation of hard plaques within the arteries.
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arteriosclerosis
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The selective breeding of domesticated plants and animals to encourage the occurrence of desirable traits.
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artificial selection
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A saclike spore capsule located at the tip of the ascocarp in dikaryotic hyphae; defining feature of the Ascomycota division of fungi.
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ascus pl. asci
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A type of reproduction involving only one parent that produces genetically identical offspring by budding or by the division of a single cell or the entire organism into two or more parts.
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asexual reproduction
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The energy-requiring process by which plant cells convert nitrate ions (NO3–) taken up by the roots of plants into ammonium ions (NH4+), which can then be used in the synthesis of amino acids and other nitrogenous compounds.
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assimilation
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The acquired ability to associate one stimulus with another; also called classical conditioning.
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associative learning
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