Glossary Pronunciation Key accessory fruit A fruit, or assemblage of fruits, adaptation Inherited characteristic of an organ- Pronounce in which the fleshy parts are derived largely or ism that enhances its survival and reproduc- a- as in ace entirely from tissues other than the ovary. tion in a specific environment. – Glossary Ј Ј a/ah ash acclimatization (uh-klı¯ -muh-tı¯-za -shun) adaptive immunity A vertebrate-specific Physiological adjustment to a change in an defense that is mediated by B lymphocytes ch chose environmental factor. (B cells) and T lymphocytes (T cells). It e¯ meet acetyl CoA Acetyl coenzyme A; the entry com- exhibits specificity, memory, and self-nonself e/eh bet pound for the citric acid cycle in cellular respi- recognition. Also called acquired immunity. g game ration, formed from a fragment of pyruvate adaptive radiation Period of evolutionary change ı¯ ice attached to a coenzyme. in which groups of organisms form many new i hit acetylcholine (asЈ-uh-til-ko–Ј-le¯n) One of the species whose adaptations allow them to fill dif- ks box most common neurotransmitters; functions by ferent ecological roles in their communities. kw quick binding to receptors and altering the perme- addition rule A rule of probability stating that ng song ability of the postsynaptic membrane to specific the probability of any one of two or more mu- o- robe ions, either depolarizing or hyperpolarizing the tually exclusive events occurring can be deter- membrane. mined by adding their individual probabilities. o ox acid A substance that increases the hydrogen ion adenosine triphosphate See ATP (adenosine oy boy concentration of a solution. triphosphate). s say acid precipitation Rain, snow, or fog that is adenylyl cyclase (uh-denЈ-uh-lil) An enzyme sh shell more acidic than pH 5.2. that converts ATP to cyclic AMP in response to th thin acoelomate (uh-se¯Ј-lo– -ma–t) A solid-bodied an extracellular signal. u¯ boot animal lacking a cavity between the gut and adhesion The clinging of one substance to u/uh up outer body wall. another, such as water to plant cell walls by – z zoo acrosomal reaction (akЈ-ruh-somЈ-ul) The means of hydrogen bonds. discharge of hydrolytic enzymes from the adipose tissue A connective tissue that insulates Ј ϭ primary accent acrosome, a vesicle in the tip of a sperm, the body and serves as a fuel reserve; contains Јϭsecondary accent when the sperm approaches or contacts an egg. fat-storing cells called adipose cells. acrosome (akЈ-ruh-so–m) A vesicle in the tip of a adrenal gland (uh-dre¯Ј-nul) One of two en- sperm containing hydrolytic enzymes and other docrine glands located adjacent to the kidneys 5Ј cap A modified form of guanine nucleotide proteins that help the sperm reach the egg. in mammals. Endocrine cells in the outer por- added onto the 5Ј end of a pre-mRNA actin (akЈ-tin) A globular protein that links into tion (cortex) respond to adrenocorticotropic molecule. chains, two of which twist helically about each hormone (ACTH) by secreting steroid hor- A site One of a ribosome’s three binding sites for other, forming microfilaments (actin filaments) mones that help maintain homeostasis during tRNA during translation. The A site holds the in muscle and other kinds of cells. long-term stress. Neurosecretory cells in the tRNA carrying the next amino acid to be added action potential An electrical signal that propa- central portion (medulla) secrete epinephrine to the polypeptide chain. (A stands for gates (travels) along the membrane of a neuron and norepinephrine in response to nerve sig- aminoacyl tRNA.) or other excitable cell as a nongraded (all-or- nals triggered by short-term stress. ABC hypothesis A model of flower formation none) depolarization. adrenocorticotropic hormone (ACTH) A identifying three classes of organ identity action spectrum A graph that profiles the rela- tropic hormone that is produced and secreted genes that direct formation of the four types of tive effectiveness of different wavelengths of by the anterior pituitary and that stimulates floral organs. radiation in driving a particular process. the production and secretion of steroid abiotic (a–Ј-bı¯-otЈ-ik) Nonliving; referring to activation energy The amount of energy that re- hormones by the adrenal cortex. the physical and chemical properties of an actants must absorb before a chemical reaction aerobic respiration A catabolic pathway for environment. will start; also called free energy of activation. organic molecules, using oxygen (O2) as the abortion The termination of a pregnancy in activator A protein that binds to DNA and final electron acceptor in an electron transport progress. stimulates gene transcription. In prokaryotes, chain and ultimately producing ATP. This is abscisic acid (ABA) (ab-sisЈ-ik) A plant hor- activators bind in or near the promoter; in the most efficient catabolic pathway and is mone that slows growth, often antagonizing eukaryotes, activators generally bind to control carried out in most eukaryotic cells and many the actions of growth hormones. Two of its elements in enhancers. prokaryotic organisms. many effects are to promote seed dormancy active immunity Long-lasting immunity con- age structure The relative number of individuals and facilitate drought tolerance. ferred by the action of B cells and T cells and of each age in a population. absorption The third stage of food processing in the resulting B and T memory cells specific for aggregate fruit A fruit derived from a single animals: the uptake of small nutrient mole- a pathogen. Active immunity can develop as a flower that has more than one carpel. cules by an organism’s body. result of natural infection or immunization. AIDS (acquired immunodeficiency absorption spectrum The range of a pigment’s active site The specific region of an enzyme that syndrome) The symptoms and signs present ability to absorb various wavelengths of light; binds the substrate and that forms the pocket during the late stages of HIV infection, defined also a graph of such a range. in which catalysis occurs. by a specified reduction in the number of T abyssal zone (uh-bisЈ-ul) The part of the ocean’s active transport The movement of a substance cells and the appearance of characteristic benthic zone between 2,000 and 6,000 m deep. across a cell membrane against its concentra- secondary infections. acanthodian (akЈ-an-tho–Ј-de¯-un) Any of a group tion or electrochemical gradient, mediated by alcohol fermentation Glycolysis followed by of ancient jawed aquatic vertebrates from the specific transport proteins and requiring an ex- the reduction of pyruvate to ethyl alcohol, re- ϩ Silurian and Devonian periods. penditure of energy. generating NAD and releasing carbon dioxide. G–1 GLOSSARY Ј – aldosterone (al-dos -tuh-ron) A steroid hormone ammonia A small, toxic molecule (NH3) produced separated and the daughter chromosomes are that acts on tubules of the kidney to regulate by nitrogen fixation or as a metabolic waste moving to the poles of the cell. ϩ the transport of sodium ions (Na ) and product of protein and nucleic acid metabolism. anatomy The structure of an organism. ϩ potassium ions (K ). ammonite A member of a group of shelled anchorage dependence The requirement that algae A diverse grade of photosynthetic protists, cephalopods that were important marine pred- a cell must be attached to a substratum in including unicellular and multicellular forms. ators for hundreds of millions of years until order to initiate cell division. Algal species are included in three of the five their extinction at the end of the Cretaceous androgen (anЈ-dro– -jen) Any steroid hormone, eukaryote supergroups (Chromalveolata, period (65.5 million years ago). such as testosterone, that stimulates the Rhizaria, and Archaeplastida). amniocentesis (amЈ-ne¯-o– -sen-te¯Ј-sis) A tech- development and maintenance of the male Ј Ј alimentary canal (al -uh-men -tuh-re¯) A com- nique associated with prenatal diagnosis in reproductive system and secondary sex Glossary plete digestive tract, consisting of a tube which amniotic fluid is obtained by aspiration characteristics. Glossary running between a mouth and an anus. from a needle inserted into the uterus. The aneuploidy (anЈ-yu¯-ployЈ-de¯) A chromosomal allele (uh-le¯Ј-ul) Any of the alternative versions fluid and the fetal cells it contains are analyzed aberration in which one or more chromosomes of a gene that may produce distinguishable to detect certain genetic and congenital defects are present in extra copies or are deficient in phenotypic effects. in the fetus. number. allergen An antigen that triggers an exaggerated amniote (amЈ-ne¯-o–t) Member of a clade of angiosperm (anЈ-je¯-o– -sperm) A flowering plant, immune response. tetrapods named for a key derived character, which forms seeds inside a protective chamber allopatric speciation (alЈ-uh-patЈ-rik) The for- the amniotic egg, which contains specialized called an ovary. mation of new species in populations that are membranes, including the fluid-filled amnion, angiotensin II A peptide hormone that stimu- geographically isolated from one another. that protect the embryo. Amniotes include lates constriction of precapillary arterioles and allopolyploid (alЈ-o– -polЈ-e¯-ployd) A fertile indi- mammals as well as birds and other reptiles. increases reabsorption of NaCl and water by vidual that has more than two chromosome amniotic egg An egg that contains specialized the proximal tubules of the kidney, increasing sets as a result of two different species inter- membranes that function in protection, nour- blood pressure and volume. breeding and combining their chromosomes. ishment, and gas exchange. The amniotic egg anhydrobiosis (an-hı¯Ј-dro– -bı¯-o–Ј-sis) A dormant allosteric regulation The binding of a regula- was a major evolutionary innovation, allowing state involving loss of almost all body water.