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Details Title: Glossary Description: Definitions Total Flash Cards: 541 Created: 03/09/2004 19:10:48	To study from this set of flash cards, or to create your own your own study flash cards, register HERE. If you are already a registered user, CLICK HERE.
Cards Term A band Definition The broad region that corresponds to the length of the thick filaments. Term A site Definition one of the three binding site for tRNA during translation, it holds the tRNA carrying the next amino acid to be added to the polypeptide chain; A stands for aminoacyl- tRNA site. Term 5' Cap Definition The 5' end of a pre-mRNA molecule modified by the addition of a cap of guanine nucleotide. Term abdominal cavity Definition The body cavity in mammals that primarily houses parts of the digestive, excretory, and reproductive systems. It is separated from the more cranial thoraic cavity by the diaphragm. Term abiotic components Definition Nonliving chemical and physical factors in the environment. Term ABO blood groups Definition genetically determined classes of human blood that are based on the presence or absence of carbohyrdrates A and B on the surface of red blood cells. The ABO blood group phenotypes, also called blood types, are A, B, AB, and O. Term abscisic acid (ABA) Definition A plant hormone that generally acts to inhibit growth, promote, dormancy, and help the plant tolerate stressful conditions. Term ABO Blood Groups Definition Genetically determined classes of human blood that are based on the presence or absence of carbohydrates A and B on the surface of red blood cells. The ABO blood group phenotypes, are also called blood types, are A, B, AB, and O. Term abscisic acid (ABA) Definition A plant hormone that generally acts to inhibit growth, promote dormacy, and help the plant tolerate stressful conditions. Term absorption Definition The uptake of small nutrient molecules by an organism's own body; the third main stage of food processing, following digestion. Term absorption spectrum Definition The range of a pigments ability to absorb various wavelengths of light. Term abyssal zone Definition The very deep benthic communities near the bottom of the ocean. This region is characterized by continuous cold, extremely high water pressure, low nutrients, and near or total absence of light. Term acanthodians Definition a group of ancient jawed fishes from the Devonian period. Term acclimitization Definition Physiological adjustment to a change in an environmental factor. Term accomodation Definition The automatic adjustment of an eye to focus on near objects. Term acetyl CoA (acetyl coenzyme A) Definition The entry compound for the krebs cycle in cellular respiration; formed from a fragment of pyruvate attached to a coenzyme. Term acetylcholine Definition One of the most common neurotransmitters; functions by binding to receptors and altering the permeability of the postsynaptic membrane to specific ions, either depolarized or hyperpolarizing the membrane. Term acid Definition a substance that increases the hydrogen concentration of a solution. Term acid chyme Definition A mixture of recently swallowed food and gastric juice. Term acid precipitation Definition rain, snow, or fog that is more acidic than pH 5.6 Term acoelomate Definition A solid-bodied animal lacking a cavity between the gut and outerbody wall. Term acrosomal reaction Definition The discharge of a sperm's acromosome when the sperm approaches the egg. Term acromosome Definition An organelle at the tip of a sperm cell that helps the sperm penetrate the egg. Term actin Definition a globular protein that links into chains, two of which twish helically about each other, forming microfilaments in muscle and other contractile elements in cells. Term Actinistia Definition the class of lobefinned fishes. Term Actinopterygii Definition The class of ray-finned fishes. Term action potential Definition A rapid change in the membrane potential of an excitable cell, caused by stimulustriggered, selective opening and closing of voltagesensitive gates in sodium and potassium ion channels. Term action spectrum Definition A profile of the relative performance of different wavelengths of light. Term activation energy Definition The amount of energy that reactants must absorb before a chemical reaction will start. Term activator Definition A transription factor that binds to an enhancer and stimulates transcription of a gene. Term active immunity Definition Immunity conferred by recovering from an infectious disease. Term active site Definition The specific portion of an enzyme that attaches to the substrate by means of weak chemical bonds. Term active site Definition The specific portion of an enzyme that attaches to the substrate by means of weak chemical bonds. Term active transport Definition 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. Term adaptive peak Definition An equilibrium state in a population when the gene pool has allele frequencies that maximize the average fitness of a population's members. Term adaptive radiation Definition The emergence of numerous species from a common ancestor introduced into an environment, presenting a diversity of new opportunities and problems. Term adenohypophysis Definition Also called the anterior pituitary, it consits of endocrine cells that synthesize and secrete several hormones directly into the blood. Term adenylyl cyclase Definition An enzyme that converts ATP to cyclic AMP in response to a chemical signal. Term adhesion Definition The attraction between different kinds of molecules. Term adrenal gland Definition An endocrine gland located adjacent to the kidney in mammals; composed of two glandular portions; an outer cortex, which responds to endocrine signals in reacting to stress and effecting salt and water balance, and a central medulla, which responds to nervous inputs resulting from stress. Term adrenal medulla Definition The central portion of an adrenal gland, controlled by nerve signals, that secretes the fight or flight hormones epinephrine and norepinphrine. Term adrenocorticotropic hormone Definition A peptide hormone released from the anterior pituitary, it stimulates the production and secretion of steroid hormones by the adrenal cortex. Term adventitious Definition Roots extending from stems and leaves above ground. Term aerobic Definition Containing oxygen; referring to an organism, environment, or cellular process that requires oxygen. Term afferent arteriole Definition The blood vessel supplying a nephron. Term Afrotheria Definition A branch of mammals that includes sloths, anteaters, and armadillos. Term age structure Definition The relative number of individuals of each age in a population. Term agglutination Definition An antibody-mediated immune response in which bacteria or viruses are clumped together, effectively neutralized, and opsonized. Term aggregate fruit Definition A fruit such as a blackberry that develops from a single flower that has several carpels. Term agnathon Definition A member of a jawless class of vertebrates represented today by the lampreys and hagfishes. Term agonistic behavior Definition A type of behavior involving a contest of some kind that determines which competitor gains access to some resource, such as food or mates. Term AIDS (acquired immunodeficiency syndrome) Definition The name of the late stages of HIV infection; defined by a specified reduction of T cells and the appearance of characteristic secondary infections. Term alcohol fermentation Definition The conversion of pyruvate to carbon dioxide and ethyl alcohol. Term alcohols Definition Organic compounds containing hydroxyl groups. Term aldehyde Definition An organic molecule with a carbonyl group located at the end of the carbon skeleton. Term aldosterone Definition An adrenal hormone that acts on the distal tubules of the kidney to stimulate the reabsorption of the sodium (Na+) and the passive flow of water from the filtrate. Term alga (plural, algae) Definition A photosynthetic plantlike protist. Term alimentary canal Definition A digestive tract consisting of a tube running between a mouth and an anus. Term allantois Definition One of the four extra-embryonic membranes; serves as a repository for the embryo's nitrogenous waste. Term alleles Definition Alternate versions of a gene. Term allometric growth Definition The variation in the relative rates of growth of various parts of the body, which helps shape the organism. Term allopatric speciation Definition A mode of speciation induced when the ancestral population becomes segregated by a geographic barrier. Term allopolypoid Definition A common type of polypoid species resulting from two different species interbreding and combining their chromosomes. Term all-or-none-event Definition An action that occurs either completely or not at all, such as the generation of an action potential by a neutron. Term allosteric site Definition A specific receptor site on some part of an enzyme molecule remote from the active site. Term alpha helix Definition A spiral shape constituting one form of the secondary structure of proteins, arising from a specific hydrogen-bonding structure. Term vaccine Definition A harmless variant or derivative of a pathogen that stimulates a host's immune system to mount defenses against the pathogen. Term alternation of generations Definition A life cycle in which there is both a multicellular diploid form, the sporophyte, and a multicellular haploid form, the gametophyte; characteristic of plants. Term alternate RNA splicing Definition A type of regulation at the RNA- processing level in which different mRNA molecules are produced from the same primary transcript depending on which RNA segments are treated as exons ans which as introns. Term altruism Definition Behavior that reduces an individual's fitness while increasing the fitenss of another individual. Term altruistic behavior Definition The aiding of another individual at one's own risk or expense. Term Alveolata Definition A protistan clade that includes dinoflagellates, apicocomplexans, and the ciliates. Alveolates have small membrane-bounded cavities called alveoli under their cell surfaces. The function of alveoli is unknown. Term alveolus Definition (1)One of the deadend, multilobed air sacs that constitute the gas exchange surface of the lungs. (2)One of the milksecreting sacs of epithelial tissue in the mammary glands. Term amarcine cell Definition Neutrons of the retina help integrate information before it is sent to the brain. Term amine Definition An organic compound with the one or more amino groups. Term amine Definition An organic compound with one or more amino groups. Term amino acid Definition An organic molecule possessing both carboxyl and amino groups. Amino acids serve as the monomers of proteins. Term amino group Definition A functional group that consists of a nitrogen atom bounded to two hyrdrogen atoms; can act as a base in solution, accepting a hydrogen ion and acquiring a charge of +1. Term aminoacyl-tRNA synthesase Definition An enzyme that joins each amino acid to the correct tRNA. Term aminopeptidase Definition An enzyme found within the snall intestine that splits off one amino acid at a time, beginning at the opposite end of the polypeptide containing a free carboxyl group. Term ammonia Definition A small and very toxic nitrogenous waste produced by metabolism. Term ammonites Definition Shelled cephalopod animals that were the dominant invertebrate predators for millions of years ending with themass extinctions at the end of the Cretaceous period. Term amniocentesis Definition A technique for determining genetic abnormalities in a fetus by the presence of certain chemicals or defective fetal cells in the amniotic fluid, obtained by aspiration from a needle inserted into the uterus. Term amnion Definition The innermost of four extraembryonic membranes; encloses a fluid-filled sac in which the embryo is suspended. Term amniote Definition A vertebrate possessing an amnion surrounding the embryo; reptiles, birds, and mammals are amniotes. Term amniotic egg Definition A shelled, water-retaininig egg that enables reptiles, birds, and egg-laying mammals to complete their life cycles on dry land. Term amoeba Definition A type of protist characterized by great flexibility and the presence of pseudopodia. Term amoebocyte Definition An amoebalike cell that moves by pseudopodia, found in most animals; depending on the species, may digest and distribute food, dispose of wastes, form skeletal fibers, fight infections, and change into other cell types. Term amoebocyte Definition An amoebalike cell that moves by pseudopodia, found in most animals; depending on the species, may digest and distribute food, dispose of wastes, form skeletal fibers, fight infections, and change into other cell types. Term Amphibia Definition The vertebrate class of amphibians, represented by frogs, salamanders, and caecilians. Term amphipathic molecule Definition A molecule that has both a hydrophillic region and a hydrophobic region. Term amplification Definition The strengthening of stimulus energy that is otherwise too weak to be carried into the nervous system. Term anabolic pathway Definition A metabollic pathway that synthesizes a complex molecule from simpler compounds. Term anaerobic Definition lacking oxygen; referring to an organism, environment, or cellular process that lacks oxygen to accept electrons at the "downhill" end of electron transport chains. Term anagenesis Definition A pattern of evolutionary change involving the transformation of an entire population, sometimes to a state different enough from the ancestral population to justify renaming it as a separate species; also called phyletic evolution. Term analogy Definition The similarity of structure between two species that are not closely related; attributable to convergent evolution. Term anaphase Definition the fourth subphase of mitosis, in which the chromatids of each chromosome have separated and the daughter chromosomes are moving to the poles of the cell. Term anaphylactic shock Definition An acute, life threatening, allergic response. Term anapsids Definition One of three groups of amniotes based on key differences between their skulls. Term anatomically modern humans Definition Fully modern humans. Term anatomy Definition The study of the structure of an organism. Term anchorage dependence Definition The requirement that to divide, a cell must be attached to the substratum. Term androgens Definition The principal male steroid hormones, such as testosterone, which stimulate the development and maintenance of the male reproductive system and secondary sex characteristics. Term aneuploidy Definition A chromosomal aberration in which certain chromosomes are present in extra copies or are deficient in number. Term angiosperm Definition A flowering plant, which forms seeds inside a protective chamber called an ovary. Term anhydrobiosis Definition The ability to survive in a dormant state when an organism's habitat dries up. Also called cryptobiosis. Term animal pole Definition The portion of the egg where the least yolk is concentrated. Opposite of the veggetal pole. Term anion Definition A negatively charged ion. Term annual Definition A plant that completes its entire life cycle in a single year or growing season. Term antennae Definition Sensory appendages found in uniramians and crustaceans. Term anterior Definition Referring to the head end of a bilaterally symmetrical animal. Term anterior pituitary Definition Also called the adenohypophysis, it consists of endocrine cells that synthesize and secrete several hormones directly into the blood. Term anther Definition Ther terminal pollen sac of a stamen, inside which pollen grains with male gametes form in the flower of an angiosperm. Term antheridium Definition In plants, the male gametangium, a moist chamber in which gametes develop. Term Anthocerophyta Definition The phylum of hornworts, small herbaccous (nonwoody) plants. Term Anthophyta Definition The phylum containing all angiosperms. Term anthropoid Definition A member of a primate group made up of the apes (gibbon, orangutan, gorilla, chimpanzee, and bonobo), monkeys, and humans. Term antibiotic Definition A chemical that kills bacteria or inhibits growth. Term antibody Definition An antigen-binding immunoglobulin produced by B cells, that functions as the effector in an immune response. Term anticodon Definition A specialized base triplet at one end of a tRNA molecule that recognizes a particular complementary codon on an mRNA molecule. Term antidiuretic hormone Definition A hormone that is part of an elaborate feedback scheme that helps regulate the osmolarity of the blood. Term antigen Definition A foreign macromolecule that does not belong to the host organism and that elicits an immune response. Term antigen presentation Definition The process by which an MHC molecule cradles a fragment of an intercellular protein antigen in its hammocklike groove, carries it to the cell surface, and "presents the protein to an antigen receptor on a nearby T cell. Term antigen receptor Definition Transmembrane versions of antibody molecules that B cells and T cells use to recognize specific antigens. Also called membrane antibodies. Term antigen-presenting cell (APC's) Definition Cells that ingest bacteria and viruses and then destroy them. Class II MHC molecules in these cells collect peptide remnants of this degradation and present them to help T cells. Term anura Definition The order of frogs and toads that includes tailless tetrapod amphibians. Term anurans Definition The group of frogs and toads. Term aphotic zone Definition The part of the ocean beneath the photic zone, where light does not penetrate sufficiently for photosynthesis to occur. Term apical dominance Definition Concentration of growth at the tip of a plant shoot, where a terminal bud partially inhibits axillary bud growth. Term apical ectodermal ridge Definition A limp-bud organizing region consisting of a thickened area of ectoderm at the tip of a limp bud. Term apical meristem Definition Embryonic plant tissure in the tips of roots and in the buds of shoots that supplies cells for the plant to grow in length. Term apicomplexan Definition One of a group of parasitic protozoans, some of which cause human diseases. Term apoda Definition The order of caecilians that includes legless amphibians. Term apodans Definition The group of caecilians. Term apomixis Definition The asexual production of seeds. Term apomorphic character Definition A derived phenotypic character, or homology, that evolved after a branch derived from a phylogenetic tree. Term apoplast Definition In plants, the nonliving continuum formed by the extracellular pathway provided by the continuous matrix of cell walls. Term apoptosis Definition Programmed cell death brought about by signals that trigger the activation of a cascade of "suicide" proteins in the cells destined to die. Term aposematic coloration Definition The bright coloration of animals with effective physical or chemical defenses that acts as a werning to predators. Term appendix Definition A small, fingerlike extension of the vertebrate cecum; contains a mass of white blood cells that contribute to immunity. Term aquaporin Definition A transport protein in the plasma membrane of a plant or animal cell that specifially facilitates the diffusion of water across the membrane.(osmosis) Term aqueous humor Definition Plasmalike liquid in the space between the lens and the cornea in the vertebrate eye; helps maintain the shape of the eye, supplies nutrients and oxygen to its tissues, and disposes of its wastes. Term aqueous solution Definition A solution in which water is the solvent. Term Arachida Definition The animal class that includes scorpions, spiders, ticks, and mites. Term Archaea Definition One of two prokaryotic domains, the other being the Bacteria. Term Archaezoa Definition Primitive eukaryotic group that includes diplomonads, such as Giardia; some systematists assign kingdom status to archezoans. Term archegonium (plural, archegonia) Definition In plants, the female gametangium, a moist chamber in which gametes develop. Term archenteron Definition The endoderm-lined cavity, formed during the gastrulation process, that develops into the digestive tract of an animal. Term archosaurs Definition The reptilian group that includes crocodiles, alligators, dinosaurs, and birds. Term arteriole Definition A vessel that conveys blood between an artery and a capillary bed. Term arteriosclerosis Definition A cardiovascular disease caused by the formation of hard plaques within the arteries. Term artery Definition A vessel that carries blood away from the heart to organs throughout the body. Term anthropod Definition Segmented coelomates with exoskeletons and jointed appendages. Term Arthropoda Definition The most diverse phylum in the animal kingdom; includes the horseshoe crabm arachnids (e.g., spiders, ticks, scorpions, and mites) , crustaceans (e.g., crayfish, lobsters, crabs, barnacles), millipedes, centipedes, and insects. Arthropods are characterized by a chitinous exoskeleton, molting, jointed appendages, and a body formed of distinct groups of segments. Term artificial selection Definition The selective breeding of domesticated plants and animals to encourage the ocurrence of desirable traits. Term ascocarps Definition Macroscopic fruiting bodies of sac fungi. Term ascus (plural, asci) Definition A saclike spore capsule located at the tip of the asocarp in dikaryotic hyphae; defining feature of the Ascomycota division of fungi. Term asexual reproduction Definition 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. Term aspartate Definition An amino acid that functions as a CNS neurotransmitter. Term associative learning Definition The acquired ability to associate one stimulus with another; also called classical conditioning. Term assortative mating Definition A type of nonrandom mating in which mating partners resemble each other in certain phenotypic characters. Term astrocytes Definition Glial cells that provide structural and metabolic support for neurons. Term asymmetric carbon Definition A carbon atom covalently bonded to four different atoms or groups of atoms. Term asymmetric cell division Definition Cell division in which one daughter cell receives more cytoplasm than the other during mitosis. Term atherosclerosis Definition A cardiovascular disease in which growths called plaques develop on the inner walls of the arteries, narrowing their inner diameters. Term atom Definition The smallest unit of matter that retains the properties of an element. Term atomic nucleus Definition An atom's core, containing protons and neutrons. Term atomic number Definition The number of protons in the nucleus of an atom, unique for each element and designated by a subscript to the left of the elemental symbol. Term atomic weight Definition The total atomic mass, which is the mass in grams of one mole of the atom. Term ATP (adenosine triphosphate) Definition 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. Term ATP synthase Definition A cluster of several membrane proteins found in the mitochondrial crista (and bacterial plasma membrane) that function in chemiosmosis with adjacent electron transport chains, using the energy of a hydrogen ion concentration gradient to make ATP. ATP synthases provide a port through which hyrdrogen ions diffuse into the matrix of a mitochondrion. Term atrial natriuretic factor Definition A peptide hormone that opposes the renin-angiotensin-aldosterone system (RAAS). Term atrioventricular valve Definition A valve in the heart between each atrium and ventricle that prevents a backflow of blood when the ventricles contract. Term atrium (plural, atria) Definition A chamber that receives blood returning to the vertebrate heart. Term autogenesis model Definition According to this model, eukaryotic cells evolved by the specialization of internal membranes originally derived from prokaryotic plasma membranes. Term autoimmune disease Definition An immunological disorder in which the immune system turns against itself. Term autonomic nervous system Definition A subdivision of the motor nervous system of vertebrates that regulates the internal environment; consists of the sympathetic and parasympathetic divisions. Term autopolyploid Definition A type of polyploid species resulting from one species doubling its chromosome number to become tetraploid, which may self-fertilize or mate with other tetraploids. Term autosome Definition A chromosome that is not directly involved in determining sex, as opposed to a sex chromosome. Term autotroph Definition An organism that obtains organic food molecules without eating other organisms or substances derived from other organisms. Autotrophs use energy from the sun or from the oxidation of inorganic substances to make organic molecules from inorganic ones. Term auxins Definition A class of plant hormones, including indoleacetic acid (IAA), having a variety if effects, such as phototropic response through the stimulation of cell elongation, stimulation of secondary growth, and the development of leaf traces and fruit. Term auxotroph Definition A nutritional mutant that is unable to synthesize and that cannot grow on media lacking certain essential molecules normally synthesized by wild-type strains of the same species. Term Aves Definition The vertebrate class of birds, characterized by feathers and other flight adaptations. Term axillary bud Definition A structure that has the potential to form a vegetative branch. The bud appears in the angle formed between a leaf and a stem. Term axon Definition A typically long extension, or process from a neuron that carries nerve impulses away from the cell body toward target cells. Term B lymphocyte (B cell) Definition A type of lymphocyte that develops in the bone marrow and later produces antibodies, which mediate humoral immunity. Term Bacteria Definition One of two prokaryotic domains, the other being the Archaea. Term bacterial artificial chromosome (BAC) Definition An artificial version of a bacterial chromosome that can carry inserts of 100,000- 500,000 base pairs. Term bacteriophage Definition A virus that infects bacteria; also called a phage. Term bacteriohodopsin Definition A photosynthetic pigment found in halophiles. It is very similar to the visual pigments in the retinas of our eyes. Term bacterium (plural, bacteria) Definition A prokaryotic microorganism in Domain Bacteria. Term bacteroids Definition A form of Rhizobium contained within the vesicles formed by the root cells of a root nodule. Term baculum Definition A bone that is contained in, and helps stiffen, the penis of rodents, raccoons, walruses, and several other mammals. Term balanced polymorphism Definition The ability of natural selection to maintain diversity in a population. Term bark Definition All tissues external to the vascular cambium in a plant growing in thickness, consisting of phloem, phelloderm, cork cambium, and cork. Term