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Glossary
- State University of New York Press
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Glossary adaptive landscape: range of evolutionary possibilities viewed as adaptive hills and ill-adapted valleys; organisms optimally adapted to one set of ecological circumstances are unlikely to adapt to another. adaptive radiation: apparently related fossils appearing in the same strata as if evolving rapidly from the same ancestral population. AI: artificial insemination; suspension of spermatozoa introduced manually into female genital tract. allele: gene, especially one of a group found alternately at the same locus on a chromosome. allopatric speciation: origin of species from geographically isolated subpopulations . amino acids: organic compounds having an amine group (-NH2 ), the organic acid group (-COOH), and residual groups bound to carbon; one of twenty such organic components of polypeptides or proteins. amniocentesis: aspiration of fluid and cells from amniotic cavity; procedure to obtain fetal cells for the diagnosis of hereditary disease. amnion: extraembryonic membrane; closest to embryo in amniotic vertebrates covers embryo and yolk sac. androgens: male steroid sex hormones associated with increased muscle mass. aneuploid: an abnormal number of chromosomes. 242 GLOSSARY antibodies: circulating immunoglobular proteins with a high affinity for substances known as antigens; similar immunoglobulins attached to lymphocytes. antigen: (1) substances capable of evoking an immunological reaction such as the production of antibodies; (2) substance combining with a specific antibody. APC: antigen-presenting cell; a macrophage or dendritic cell which has taken up and processed an antigen for later interaction with a competent immunoreactive lymphocytes. apoptosis: cytological and nuclear events accompanying programmed cell death especially condensation and fragmentation of dying cell’s nucleus. Archaea (also Archaebacteria): Domain of life; type of prokaryote. area pellucida: portion of avian egg and cellular blastoderm that gives rise to embryo proper and extraembryonic membranes. asexual reproduction: reproduction entirely by the body’s own (somatic) cells without the participation of sex cells. ATP: adenosine triphosphate; molecule utilized in energy- and phosphatetransferring reactions within cells. B cells: type of lymphocyte especially capable of reacting with other cells of the immune system by producing specific antibodies. Bacteria (also Eubacteria): Domain of life; type of prokaryote including Escherichia coli and blue green bacteria (cyanobacteria). base pairing: Watson/Crick pairing; couplets of complementary nitrogenous bases (A–T or U; C–G) linking stands of nucleic acids together. Bauplan (pl.: Baupläne): theoretical construction plan for related organisms. Bilateria: animals (metazoans) with three germ layers in gastrula and bilateral (rarely radial) symmetry in adults. biosphere: portion of Earth’s surface and surrounding atmosphere containing all organisms living on Earth. [44.215.110.142] Project MUSE (2024-03-29 02:01 GMT) Glossary 243 blastocoel: cavity within an early embryo; cavity within a blastula. blastocyst: preembryonic stage of mammalian development in which a layer of outer cells (trophectoderm or trophoblast) encloses an eccentric group of cells (inner cell mass) and a fluid-filled cavity (blastocyst cavity). blastoderm: layer of embryonic cells. blastomere: embryonic cell, especially cell produced by cleavage. blastula: stage of embryonic development following cleavage and preceding gastrulation. bone marrow (strictly red bone marrow): blood- and lymphocyte-forming tissue in cavity of bones. Caenorhabditis elegans (also C. elegans): a free-living round-worm found in soil and frequently used in developmental and genetic research. Cambrian: geological Period at beginning of Paleozoic (Phanerozoic) Era. cDNA: complementary (copy) DNA; DNA made by reverse transcriptase complementary to an RNA template. cell cycle: succeeding periods of cell division, or mitosis, and interphase. cellular turnover: physiological replacement of cells in stable organs and systems. cellularization: formation of the cellular blastoderm in the embryos of some insects at end of cleavage. central dogma: doctrine that DNA determines everything about proteins and, therefore, the way an organism interacts with its environment, but the organism’s environment determines nothing about DNA and, therefore, has no influence on heredity. chloroplast: cell organelle found in plants and algae capable of conducting photosynthesis; organelle derived from cyanobacteria. chorion: membrane over watery cavity; outermost extraembryonic membrane. 244 GLOSSARY chromosome: (1) rod-shaped, colored body appearing in eukaryotic cell prior to cell division and separating into two identical bodies during division; (2) nucleic acid bearing hereditary information. cladistics: method for weighing similarities and differences among sets of organismic characteristics, especially molecular sequence-data, used to propose patterns of branching evolution. cleavage: cell division in fertilized egg and blastomeres. CNS: central nervous system; portion of nervous system consisting of brain and spinal cord in vertebrates. codon: triplet of nitrogenous bases in messenger RNA directing the incorporation of a specific amino acid into a polypeptide or protein. conjugation: sexual-like coupling in algae and protozoans; formation of...