Lewis/Life - Glossary

I

ileum Il-ee-um The last section of the small intestine. 761

imbibition IM-bah-BISH-un The absorption of water by a seed. 40

implantation im-plan-TAY-shun Nestling of the blastocyst into the uterine lining. 218

imprinting A type of learning that usually occurs early in life and is performed without obvious reinforcement. 816

inclusive fitness Fitness defined by personal reproductive success as well as by relatives sharing an individual's genes. 826

incomplete dominance A heterozygote whose phenotype is intermediate between the phenotypes of the two homozygotes. 273

incomplete penetrance A genotype that does not always produce a phenotype. 275

incus INK-us A small bone in the middle ear. 653

independent assortment The random organization of homologs during metaphase of meiosis I. 201, 269

indeterminate cleavage in-dee-TER-min-et CLEEV-edge A cleavage embryo in which the fate of the cells is not yet determined. 514

industrial melanism in-DUS-tree-al MEL-an-iz-um Coloration that is adaptive in a polluted area. 410

inferior vena cava in-FEAR-ee-er VE-nah KA-vah The lower branch of the largest vein that leads to the heart. 720

inflammation in-flam-AY-shun Increased blood flow and accumulation of fluid and phagocytes at the site of an injury, rendering it inhospitable to bacteria. 791

initiation complex in-ish-e-A-shun COM-plex A small ribosomal subunit, mRNA, and an initiator tRNA, joined. 333

initiation site in-ish-e-A-shun SITE The site on a chromosome where DNA replication begins. 317

innate in-AYT Instinctive. 812

inner cell mass The cells in the blastocyst that develop into the embryo. 218

insertion in-SER-shun The end of a muscle on a movable bone. 700

insight learning Ability to apply prior learning to a new situation without trial-and-error activity. 816

insulin IN-sel-in A pancreatic hormone that lowers blood sugar level by stimulating body cells to take up glucose from the blood and to metabolize or store it. 663, 672

integrin in-TEG-rin A cell adhesion molecule that helps direct a white blood cell through a capillary wall to the site of an injury. 103

integument in-TEG-u-ment Outer covering of an animal's body. 594

intercalary meristem in-TER-kah-LARE-ee MER-eh-stem Dividing tissue between mature regions of grass stem. 535

intercalated disks in-TER-kah-LAY-tid DISKS Tight foldings in cardiac muscle cell membranes that join adjacent cells. 692

intercellular junctions Structures that join cells, including tight junctions, gap junctions, desmosomes, and plasmodesmata. 96

interferon in-ter-FEAR-on A polypeptide produced by a T cell infected with a virus that diffuses to surrounding cells and stimulates them to manufacture biochemicals that halt viral replication. 791

interleukin in-ter-LUKE-in A class of immune system biochemicals. 792

intermediate-day plant Plant that flowers only when exposed to days of intermediate length, growing vegetatively at other times. 584

intermediate filament Cytoskeletal element intermediate in size between a microtubule and a microfilament. 100

intermembrane compartment in-ter-MEM-brain cum-PART-ment The space between a mitochondrion's two membranes. 128

interneuron in-ter-NURE-on A neuron that connects one neuron to another to integrate information from many sources and to coordinate responses. 611

internode In-ter-node Part of stem between nodes. 541

interphase IN-ter-faze The period when the cell synthesizes proteins, lipids, carbohydrates, and nucleic acids. 168

intertidal zone IN-ter-TI-dal ZONE The region bordering an estuary where the tide recedes and returns. 881

intestinal ceca in-TES-tin-al SEE-ka The site of digestion and absorption in flatworms. 517

intracellular digestion in-tra-SEL-yu-lar di-JEST-shun Digestion within food vacuoles in cells. 753

intrinsic rate of increase Population growth rate if survival and reproduction are unrestricted. 840

intrinsic rate of natural increase Population growth rate under ideal conditions. 840

intron IN-tron Bases of a gene that are transcribed but are excised from the mRNA before translation into protein. 330

inversion in-VER-shun An introverted gene sequence. 301

invertebrate in-VERT-e-brayt An animal that does not have a backbone. 508

ion I-on An atom that has lost or gained electrons, giving it an electrical charge. 38

ionic bond i-ON-ik bond Attraction between oppositely charged ions. 38

ionizing radiation I-o-nize-ing rade-e-A-shun Radiation that ejects electrons from atoms. 147

irritability IR-eh-tah-BIL-eh-tee An immediate response to a stimulus. 10

islets of Langerhans I-letz uv LANG-er-hanz Clusters of cells in the pancreas that secrete hormones that control nutrient use. 672

isotonic ice-o-TON-ik When solute concentration is the same on both sides of a membrane. 88

isotope I-so-tope A differently weighted form of an element. 33

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