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English Glossary This glossary defines each key term that appears in bold type in the text. It also shows the chapter, section, and page number where you can find the word(s) used. English Glossary A 866 abiotic: nonliving, physical features of the environment, including air, water, sunlight, soil, temperature, and climate. (Chap. 25, Sec. 1, p. 720) acid precipitation: precipitation with a pH below 5.6 that can pollute water, kill fish and plants, and damage soils; occurs when air pollutants from the burning of fossil fuels react with water in the atmosphere to form strong acids. (Chap. 27, Sec. 2, p. 787) active immunity: long-lasting immunity that results when the body makes its own antibodies in response to a specific antigen. (Chap. 23, Sec. 1, p. 661) active transport: energy-requiring process in which transport proteins bind with particles and move them through a cell membrane. (Chap. 3, Sec. 2, p. 77) adaptation: any variation that makes an organism better suited to its environment. (Chap. 6, Sec. 1, p. 158) aerobe (AY rohb): any organism that uses oxygen for respiration. (Chap. 7, Sec. 1, p. 190) aggression: forceful behavior, such as fighting, used by an animal to control or dominate another animal in order to protect their young, defend territory, or get food. (Chap. 16, Sec. 2, p. 468) algae (AL jee): chlorophyll-containing, plantlike protists that produce oxygen as a result of photosynthesis. (Chap. 8, Sec. 1, p. 213) allele (uh LEEL): an alternate form that a gene may have for a single trait; can be dominant or recessive. (Chap. 5, Sec. 1, p. 126) allergen: substance that causes an allergic reaction. (Chap. 23, Sec. 3, p. 673) ENGLISH GLOSSARY allergy: overly strong reaction of the immune system to a foreign substance. (Chap. 23, Sec. 3, p. 672) alveoli (al VEE uh li): tiny, thin-walled, grapelike clusters at the end of each bronchiole that are surrounded by capillaries, where carbon dioxide and oxygen exchange takes place. (Chap. 20, Sec. 1, p. 577) amino acid: building block of protein. (Chap. 18, Sec. 1, p. 519) amniotic egg: egg covered with a leathery shell that provides a complete environment for the embryo’s development; for reptiles, a major adaptation for living on land. (Chap. 14, Sec. 4, p. 417) amniotic (am nee AH tihk) sac: thin, liquid-filled, protective membrane that forms around the embryo. (Chap. 22, Sec. 3, p. 641) anaerobe (AN uh rohb): any organism that is able to live without oxygen. (Chap. 7, Sec. 1, p. 190) angiosperms: flowering vascular plants that produce a fruit containing one or more seeds; monocots and dicots. (Chap. 9, Sec. 3, p. 259) antibiotics: chemicals produced by some bacteria that are used to limit the growth of other bacteria. (Chap. 7, Sec. 2, p. 195) antibody: a protein made in response to a specific antigen that can attach to the antigen and cause it to be useless. (Chap. 23, Sec. 1, p. 660) antigen (AN tih jun): complex molecule that is foreign to your body. (Chap. 23, Sec. 1, p. 660) anus: opening at the end of the digestive tract through which wastes leave the body. (Chap. 12, Sec. 3, p. 351) English Glossary B basidium (buh SIHD ee uhm): club-shaped, reproductive structure in which club fungi produce spores. (Chap. 8, Sec. 2, p. 226) behavior: the way in which an organism interacts with other organisms and its environment; can be innate or learned. (Chap. 16, Sec. 1, p. 460) bilateral symmetry: body parts arranged in a similar way on both sides of the body, with each half being a mirror image of the other half. (Chap. 12, Sec. 1, p. 339) binomial nomenclature (bi NOH mee ul • NOH mun klay chur): two-word naming system for organisms; first word is the genus and second word is the species. (Chap. 1, Sec. 4, p. 20) biogenesis (bi oh JEN us suhs): theory that living things can come only from other living things. (Chap. 1, Sec. 3, p. 19) biological vector: disease-carrying organism, such as a rat, mosquito, or fly, that spreads infectious disease. (Chap. 23, Sec. 2, p. 667) biomes (BI ohmz): large geographic areas with similar climates and ecosystems; includes tundra, taiga, desert, temperate deciduous forest, temperate rain forest, tropical rain forest, and grassland. (Chap. 26, Sec. 2, p. 752) biosphere: part of Earth that supports life, including the top portion of Earth’s crust, the atmosphere, and all the water on Earth’s surface. (Chap. 24, Sec. 1, p. 692) biotic (bi AHT ik): features of the environment that are alive or were once alive. (Chap. 25, Sec. 1, p. 720) bladder: elastic, muscular organ that holds urine until it leaves the body through the urethra. (Chap. 20, Sec. 2, p. 586) brain stem: connects the brain to the spinal cord and is made up of the midbrain, the pons, and the medulla. (Chap. 21, Sec. 1, p. 604) bronchi (BRAHN ki): two short tubes that branch off the lower end of the trachea and carry air into the lungs. (Chap. 20, Sec. 1, p. 577) budding: form of asexual reproduction in which a new, genetically identical organism forms on the side of its parent. (Chap. 8, Sec. 2, p. 226) ENGLISH GLOSSARY English Glossary appendages: jointed structures of arthropods, such as legs, wings, or antennae. (Chap. 13, Sec. 3, p. 374) artery: blood vessel that carries blood away from the heart and has thick, elastic walls made of connective tissue and smooth muscle tissue. (Chap. 19, Sec. 1, p. 550) ascus (AS kus): saclike, spore-producing structure of sac fungi. (Chap. 8, Sec. 2, p. 226) asexual reproduction: a type of reproduction—fission, budding, and regeneration—in which a new organism is produced from one parent and has DNA identical to the parent organism. (Chap. 4, Sec. 1, p. 101) asthma: lung disorder in which the bronchial tubes contract quickly and cause shortness of breath, wheezing, or coughing; may occur as an allergic reaction. (Chap. 20, Sec. 1, p. 582) atmosphere: air surrounding Earth; is made up of gases, including 78 percent nitrogen, 21 percent oxygen, and 0.03 percent carbon dioxide. (Chap. 25, Sec. 1, p. 721) atriums (AY tree umz): two upper chambers of the heart that contract at the same time during a heartbeat. (Chap. 19, Sec. 1, p. 547) auxin (AWK sun): plant hormone that causes plant leaves and stems to exhibit positive phototropisms. (Chap. 11, Sec. 2, p. 316) axon (AK sahn): neuron structure that carries messages away from the cell body. (Chap. 21, Sec. 1, p. 601) 867 English Glossary English Glossary C 868 cambium (KAM bee um): vascular tissue that produces xylem and phloem cells as a plant grows. (Chap. 9, Sec. 3, p. 257) capillary: microscopic blood vessel that connects arteries and veins; has walls one cell thick, through which nutrients and oxygen diffuse into body cells and waste materials and carbon dioxide diffuse out. (Chap. 19, Sec. 1, p. 551) carbohydrate (kar boh HI drayt): nutrient that usually is the body’s main source of energy. (Chap. 18, Sec. 1, p. 520) carbon cycle: model describing how carbon molecules move between the living and nonliving world. (Chap. 25, Sec. 2, p. 733) cardiac muscle: striated, involuntary muscle found only in the heart. (Chap. 17, Sec. 2, p. 499) carnivore: animal that eats only other animals or the remains of other animals. (Chap. 12, Sec. 1, p. 335) (Chap. 15, Sec. 2, p. 441) carrying capacity: largest number of individuals of a particular species that an ecosystem can support over time. (Chap. 24, Sec. 2, p. 699) cartilage: tough, flexible tissue that joins vertebrae and makes up all or part of the vertebrate endoskeleton. (Chap. 14, Sec. 1, p. 399) (Chap. 17, Sec. 1, p. 492) cell: smallest unit of a living thing that can perform the functions of life; has an orderly structure and contains hereditary material. (Chap. 1, Sec. 2, p. 10) cell membrane: protective outer covering of all cells that is made up of a double layer of fatlike molecules and regulates the interaction between the cell and the environment. (Chap. 2, Sec. 1, p. 38) cell theory: states that all organisms are made up of one or more cells, the cell is the basic unit of life, and all cells come from other cells. (Chap. 2, Sec. 2, p. 51) ENGLISH GLOSSARY cellulose (SEL yuh lohs): chemical compound made out of sugar; forms tangled fibers in the cell walls of many plants and provides structure and support. (Chap. 9, Sec. 1, p. 244) cell wall: rigid structure that encloses, supports, and protects the cells of plants, algae, fungi, and most bacteria. (Chap. 2, Sec. 1, p. 39) central nervous system: division of the nervous system, made up of the brain and spinal cord. (Chap. 21, Sec. 1, p. 603) cerebellum (sur uh BEL um): part of the brain that controls voluntary muscle movements, maintains muscle tone, and helps maintain balance. (Chap. 21, Sec. 1, p. 604) cerebrum (suh REE brum): largest part of the brain, where memory is stored, movements are controlled, and impulses from the senses are interpreted. (Chap. 21, Sec. 1, p. 604) chemical digestion: occurs when enzymes and other chemicals break down large food molecules into smaller ones. (Chap. 18, Sec. 2, p. 529) chemosynthesis (kee moh SIN thuh sus): process in which producers make energyrich nutrient molecules from chemicals. (Chap. 25, Sec. 3, p. 735) chemotherapy (kee moh THAYR uh pee): use of chemicals to destroy cancer cells. (Chap. 23, Sec. 3, p. 676) chlorophyll (KLOR uh fihl): green, lighttrapping pigment in plant chloroplasts that is important in photosynthesis. (Chap. 11, Sec. 1, p. 306) chloroplast: green, chlorophyll-containing, plant-cell organelle that converts sunlight, carbon dioxide, and water into sugar. (Chap. 2, Sec. 1, p. 42) chordate: animal that has a notochord, a nerve cord, gill slits, and a postanal tail present at some stage in its development. (Chap. 14, Sec. 1, p. 398) chromosome: structure in a cell’s nucleus that contains genetic material. (Chap. 4, Sec. 1, p. 98) English Glossary control: in an experiment, the standard to which the outcome of the test will be compared. (Chap. 1, Sec. 1, p. 9) coral reef: diverse ecosystem formed from the calcium carbonate shells secreted by corals. (Chap. 26, Sec. 3, p. 765) coronary (KOR uh ner ee) circulation: flow of blood to and from the tissues of the heart. (Chap. 19, Sec. 1, p. 547) courtship behavior: behavior that allows males and females of the same species to recognize each other and prepare to mate. (Chap. 16, Sec. 2, p. 469) crop: digestive system sac in which earthworms store ingested soil. (Chap. 13, Sec. 2, p. 370) cuticle (KYEWT ih kul): waxy, protective layer that covers the stems, leaves, and flowers of many plants and helps prevent water loss. (Chap. 9, Sec. 1, p. 244) cyclic behavior: behavior that occurs in repeated patterns. (Chap. 16, Sec. 2, p. 472) cytoplasm: constantly moving gel-like mixture inside the cell membrane that contains heredity material and is the location of most of a cell’s life processes. (Chap. 2, Sec. 1, p. 38) English Glossary chyme (KIME): liquid product of digestion. (Chap. 18, Sec. 2, p. 533) cilia (SIHL ee uh): short, threadlike structures that extend from the cell membrane of a ciliate and allow the organism to move quickly. (Chap. 8, Sec. 1, p. 217) climate: average weather conditions of an area over time, including wind, temperature, and rainfall or other types of precipitation such as snow or sleet. (Chap. 25, Sec. 1, p. 725) climax community: stable, end stage of ecological succession in which the plants and animals of a community use resources efficiently and balance is maintained by disturbances such as fire. (Chap. 26, Sec. 1, p. 751) closed circulatory system: blood circulation system in which blood moves through the body in closed vessels. (Chap. 13, Sec. 1, p. 366) cochlea (KOH klee uh): fluid-filled structure in the inner ear in which sound vibrations are converted into nerve impulses that are sent to the brain. (Chap. 21, Sec. 2, p. 614) commensalism: a type of symbiotic relationship in which one organism benefits and the other organism is not affected. (Chap. 24, Sec. 3, p. 706) community: all the populations of different species that live in an ecosystem. (Chap. 24, Sec. 1, p. 694) condensation: process that takes place when a gas changes to a liquid. (Chap. 25, Sec. 2, p. 729) conditioning: occurs when the response to a stimulus becomes associated with another stimulus. (Chap. 16, Sec. 1, p. 464) consumer: organism that cannot create energy-rich molecules but obtains its food by eating other organisms. (Chap. 24, Sec. 3, p. 705) contour feathers: strong, lightweight feathers that give birds their coloring and shape and that are used for flight. (Chap. 15, Sec. 1, p. 434) D day-neutral plant: plant that doesn’t require a specific photoperiod and can begin the flowering process over a range of night lengths. (Chap. 11, Sec. 2, p. 318) dendrite: neuron structure that receives messages and sends them to the cell body. (Chap. 21, Sec. 1, p. 601) dermis: skin layer below the epidermis that contains blood vessels, nerves, oil and sweat glands, and other structures. (Chap. 17, Sec. 3, p. 503) desert: driest biome on Earth with less than 25 cm of rain each year; has dunes or thin soil with little organic matter and plants and animals specially adapted to survive extreme conditions. (Chap. 26, Sec. 2, p. 758) ENGLISH GLOSSARY 869 English Glossary English Glossary diaphragm (DI uh fram): muscle beneath the lungs that contracts and relaxes to move gases in and out of the body. (Chap. 20, Sec. 1, p. 578) dicot: angiosperm with two cotyledons inside its seed, flower parts in multiples of four or five, and vascular bundles in rings. (Chap. 9, Sec. 3, p. 260) diffusion: a type of passive transport in cells in which molecules move from areas where there are more of them to areas where there are fewer of them. (Chap. 3, Sec. 2, p. 75) digestion: mechanical and chemical breakdown of food into small molecules that cells can absorb and use. (Chap. 18, Sec. 2, p. 529) diploid (DIH ployd): cell whose chromosomes occur in pairs. (Chap. 4, Sec. 2, p. 104) DNA: deoxyribonucleic acid; the genetic material of all organisms; made up of two twisted strands of sugar-phosphate molecules and nitrogen bases. (Chap. 4, Sec. 3, p. 110) dominant (DAHM uh nunt): describes a trait that covers over, or dominates, another form of that trait. (Chap. 5, Sec. 1, p. 128) down feathers: soft, fluffy feathers that provide an insulating layer next to the skin of adult birds and that cover the bodies of young birds. (Chap. 15, Sec. 1, p. 434) E ecology: study of the interactions that take place among organisms and their environment. (Chap. 24, Sec. 1, p. 693) ecosystem: all the living organisms that live in an area and the nonliving features of their environment. (Chap. 24, Sec. 1, p. 693) ectotherm: vertebrate animal whose internal temperature changes when the temperature of its environment changes. (Chap. 14, Sec. 1, p. 401) 870 ENGLISH GLOSSARY egg: haploid sex cell formed in the female reproductive organs. (Chap. 4, Sec. 2, p. 104) embryo: fertilized egg that has attached to the wall of the uterus. (Chap. 22, Sec. 3, p. 641) embryology (em bree AHL uh jee): study of embryos and their development. (Chap. 6, Sec. 2, p. 167) emphysema (em fuh SEE muh): lung disease in which the alveoli enlarge. (Chap. 20, Sec. 1, p. 581) endocytosis (en duh si TOH sus): process by which a cell takes in a substance by surrounding it with the cell membrane. (Chap. 3, Sec. 2, p. 78) endoplasmic reticulum (ER): cytoplasmic organelle that moves materials around in a cell and is made up of a complex series of folded membranes; can be rough (with attached ribosomes) or smooth (without attached ribosomes). (Chap. 2, Sec. 1, p. 43) endoskeleton: supportive framework of bone and/or cartilage that provides an internal place for muscle attachment and protects a vertebrate’s internal organs. (Chap. 14, Sec. 1, p. 399) endospore: thick-walled, protective structure produced by a pathogen when conditions are unfavorable for survival. (Chap. 7, Sec. 2, p. 199) endotherm: vertebrate animal with a constant internal temperature. (Chap. 14, Sec. 1, p. 401) energy pyramid: model that shows the amount of energy available at each feeding level in an ecosystem. (Chap. 25, Sec. 3, p. 737) enzyme: a type of protein that regulates nearly all chemical reactions in cells. (Chap. 3, Sec. 1, p. 71) (Chap. 18, Sec. 2, p. 530) epidermis: outer, thinnest skin layer that constantly produces new cells to replace the dead cells rubbed off its surface. (Chap. 17, Sec. 3, p. 502) English Glossary F fat: nutrient that stores energy, cushions organs, and helps the body absorb vitamins. (Chap. 18, Sec. 1, p. 521) fermentation: process by which oxygenlacking cells and some one-celled organisms release small amounts of energy from glucose molecules and produce wastes such as alcohol, carbon dioxide, and lactic acid. (Chap. 3, Sec. 3, p. 84) fertilization: in sexual reproduction, the joining of a sperm and egg. (Chap. 4, Sec. 2, p. 104) fetal stress: can occur during the birth process or after birth as an infant adjusts from a watery, dark, constant-temperature environment to its new environment. (Chap. 22, Sec. 3, p. 644) fetus: a developing baby after the first two months of pregnancy until birth. (Chap. 22, Sec. 3, p. 642) fin: fanlike structure used by fish for steering, balancing, and movement. (Chap. 14, Sec. 2, p. 403) fission: simplest form of asexual reproduction in which two new cells are produced with genetic material identical to each other and identical to the previous cell. (Chap. 7, Sec. 1, p. 190) flagellum: long, thin, whiplike structure of some protists that helps them move through moist or wet surroundings. (Chap. 7, Sec. 1, p. 189) (Chap. 8, Sec. 1, p. 214) food group: group of foods—such as bread, cereal, rice, and pasta—containing the same type of nutrients. (Chap. 18, Sec. 1, p. 526) food web: model that shows the complex feeding relationships among organisms in a community. (Chap. 25, Sec. 3, p. 736) fossil fuels: nonrenewable energy resources—coal, oil, and natural gas— that formed in Earth’s crust over hundreds of millions of years. (Chap. 27, Sec. 1, p. 780) free-living organism: organism that does not depend on another organism for food or a place to live. (Chap. 12, Sec. 3, p. 348) frond: leaf of a fern that grows from the rhizome. (Chap. 10, Sec. 2, p. 280) English Glossary equilibrium: occurs when molecules of one substance are spread evenly throughout another substance. (Chap. 3, Sec. 2, p. 75) erosion: movement of soil from one place to another. (Chap. 27, Sec. 2, p. 793) estivation: inactivity in hot, dry months during which amphibians hide in cooler ground. (Chap. 14, Sec. 3, p. 411) estuary: extremely fertile area where a river meets an ocean; contains a mixture of freshwater and salt water and serves as a nursery for many species of fish. (Chap. 26, Sec. 3, p. 766) evaporation: process that takes place when a liquid changes to a gas. (Chap. 25, Sec. 2, p. 728) evolution: change in inherited characteristics over time. (Chap. 6, Sec. 1, p. 154) exocytosis (ek soh si TOH sus): process by which vesicles release their contents outside the cell. (Chap. 3, Sec. 2, p. 78) exoskeleton: thick, hard, outer covering that protects and supports arthropod bodies and provides places for muscles to attach. (Chap. 13, Sec. 3, p. 374) G gametophyte (guh MEE tuh fite) stage: plant life cycle stage that begins when cells in reproductive organs undergo meiosis and produce haploid cells (spores). (Chap. 10, Sec. 1, p. 277) gene: section of DNA on a chromosome that contains instructions for making specific proteins. (Chap. 4, Sec. 3, p. 112) ENGLISH GLOSSARY 871 English Glossary English Glossary 872 genetic engineering: biological and chemical methods to change the arrangement of a gene’s DNA to improve crop production, produce large volumes of medicine, and change how cells perform their normal functions. (Chap. 5, Sec. 3, p. 141) genetics (juh NET ihks): the study of how traits are inherited through the actions of alleles. (Chap. 5, Sec. 1, p. 126) genotype (JEE nuh tipe): an organism’s genetic makeup. (Chap. 5, Sec. 1, p. 130) genus: a group of similar species. (Chap. 1, Sec. 4, p. 24) geothermal energy: heat energy within Earth’s crust; available only where natural geysers or volcanoes are located. (Chap. 27, Sec. 1, p. 783) germination: series of events that results in the growth of a plant from a seed. (Chap. 10, Sec. 3, p. 292) gestation period: period during which an embryo develops in the uterus; the length of time varies among species. (Chap. 15, Sec. 2, p. 445) gills: organs that exchange carbon dioxide for oxygen in water. (Chap. 13, Sec. 1, p. 364) gill slits: in developing chordates, the paired openings found in the area between the mouth and digestive tube. (Chap. 14, Sec. 1, p. 399) gizzard: muscular digestive system structure in which earthworms grind soil and organic matter. (Chap. 13, Sec. 2, p. 370) Golgi bodies: organelles that package cellular materials and transport them within the cell or out of the cell. (Chap. 2, Sec. 1, p. 43) gradualism: model describing evolution as a slow process by which one species changes into a new species through a continuing series of mutations and variations over time. (Chap. 6, Sec. 1, p. 160) grasslands: temperate and tropical regions with 25 cm to 75 cm of precipitation each year that are dominated by climax communities of grasses; ideal for growing crops and raising cattle and sheep. (Chap. 26, Sec. 2, p. 759) ENGLISH GLOSSARY greenhouse effect: heat-trapping feature of the atmosphere that keeps Earth warm enough to support life. (Chap. 27, Sec. 2, p. 788) guard cells: pairs of cells that surround stomata and control their opening and closing. (Chap. 9, Sec. 3, p. 255) gymnosperms: vascular plants that do not flower, generally have needlelike or scalelike leaves, and produce seeds that are not protected by fruit; conifers, cycads, ginkgoes, and gnetophytes. (Chap. 9, Sec. 3, p. 258) H habitat: place where an organism lives and that provides the types of food, shelter, moisture, and temperature needed for survival. (Chap. 24, Sec. 1, p. 695) haploid (HA ployd): cell that has only one of each type of chromosome. (Chap. 4, Sec. 2, p. 105) hazardous wastes: waste materials, such as pesticides and leftover paints, that are harmful to human health or poisonous to living organisms. (Chap. 27, Sec. 2, p. 794) hemoglobin (HEE muh gloh bun): chemical in red blood cells that carries oxygen from the lungs to body cells and carries some carbon dioxide from body cells back to the lungs. (Chap. 19, Sec. 2, p. 557) herbivore: animal that eats only plants or parts of plants. (Chap. 12, Sec. 1, p. 335) (Chap. 15, Sec. 2, p. 441) heredity (huh RED ut ee): the passing of traits from parent to offspring. (Chap. 5, Sec. 1, p. 126) hermaphrodite (hur MA fruh dite): animal that produces sperm and eggs in the same body, but its sperm cannot fertilize its own eggs. (Chap. 12, Sec. 2, p. 342) heterozygous (het uh roh ZI gus): describes an organism with two different alleles for a trait. (Chap. 5, Sec. 1, p. 130) English Glossary I immune system: complex group of defenses that protects the body against pathogens—includes the skin and respiratory, digestive, and circulatory systems. (Chap. 23, Sec. 1, p. 658) imprinting: occurs when an animal forms a social attachment to another organism during a specific period following birth or hatching. (Chap. 16, Sec. 1, p. 463) incomplete dominance: production of a phenotype that is intermediate between the two homozygous parents. (Chap. 5, Sec. 2, p. 134) infectious disease: disease caused by a virus, bacterium, fungus, or protist that is spread from an infected organism or the environment to another organism. (Chap. 23, Sec. 2, p. 667) innate behavior: behavior that an organism is born with and does not have to be learned, such as a reflex or instinct. (Chap. 16, Sec. 1, p. 461) inorganic compound: compound, such as H2O, that is made from elements other than carbon and whose atoms usually can be arranged only in one structure. (Chap. 3, Sec. 1, p. 71) insight: form of reasoning that allows animals to use past experiences to solve new problems. (Chap. 16, Sec. 1, p. 465) instinct: complex pattern of innate behavior, such as spinning a web, that can take weeks to complete. (Chap. 16, Sec. 1, p. 462) intertidal zone: part of the shoreline that is underwater at high tide and exposed to the air at low tide. (Chap. 26, Sec. 3, p. 766) invertebrate: animal without a backbone. (Chap. 12, Sec. 1, p. 338) involuntary muscle: muscle, such as heart muscle, that cannot be controlled consciously. (Chap. 17, Sec. 2, p. 497) ENGLISH GLOSSARY English Glossary hibernation: cyclic response of inactivity and slowed metabolism that occurs during periods of cold temperatures and limited food supplies. (Chap. 14, Sec. 3, p. 411) (Chap. 16, Sec. 2, p. 473) homeostasis: regulation of an organism’s internal, life-maintaining conditions despite changes in its environment. (Chap. 1, Sec. 2, p. 15) (Chap. 21, Sec. 1, p. 601) hominid: humanlike primate that appeared about 4 million to 6 million years ago, ate both plants and meat, and walked upright on two legs. (Chap. 6, Sec. 3, p. 171) homologous (huh MAHL uh gus): body parts that are similar in structure and origin and can be similar in function. (Chap. 6, Sec. 2, p. 168) Homo sapiens: early humans that likely evolved from Cro-Magnons. (Chap. 6, Sec. 3, p. 173) homozygous (hoh muh ZI gus): describes an organism with two alleles that are the same for a trait. (Chap. 5, Sec. 1, p. 130) hormone (HOR mohn): chemical produced by the endocrine system; released directly into the bloodstream by ductless glands; affects specific target tissues, and can speed up or slow down cellular activities. (Chap. 22, Sec. 1, p. 628) host cell: living cell in which a virus can actively reproduce or in which a virus can hide until activated by environmental stimuli. (Chap. 2, Sec. 3, p. 52) hybrid (HI brud): an offspring that was given different genetic information for a trait from each parent. (Chap. 5, Sec. 1, p. 128) hydroelectric power: electricity produced when the energy of falling water turns the blades of a generator turbine. (Chap. 27, Sec. 1, p. 781) hyphae (HI fee): mass of many-celled, threadlike tubes forming the body of a fungus. (Chap. 8, Sec. 2, p. 224) hypothesis: a prediction that can be tested. (Chap. 1, Sec. 1, p. 8) 873 English Glossary J joint: any place where two or more bones come together; can be movable or immovable. (Chap. 17, Sec. 1, p. 493) K English Glossary kidney: bean-shaped urinary system organ that is made up of about 1 million nephrons and filters blood, producing urine. (Chap. 20, Sec. 2, p. 584) kingdom: first and largest category in the scientific classification system of organisms; can be divided into smaller groups: phylum, class, order, family, genus, and species. (Chap. 1, Sec. 4, p. 23) 874 L larynx: airway to which the vocal cords are attached. (Chap. 20, Sec. 1, p. 577) law: a scientific statement about how things happen in nature and that seems to be true at all times. (Chap. 1, Sec. 1, p. 10) lichen (LI kun): organism made up of a fungus and a green alga or a cyanobacterium. (Chap. 8, Sec. 2, p. 228) ligament: tough band of tissue that holds bones together at joints. (Chap. 17, Sec. 1, p. 493) limiting factor: anything that can restrict the size of a population, including living and nonliving features of an ecosystem, such as predators or drought. (Chap. 24, Sec. 2, p. 698) long-day plant: plant that generally requires short nights—less than ten to 12 hours of darkness—to begin the flowering process. (Chap. 11, Sec. 2, p. 318) lymph (LIHMF): tissue fluid that has diffused into the capillaries. (Chap. 19, Sec. 3, p. 562) lymphatic system: carries lymph though a network of lymph capillaries and vessels and drains it into large veins near the heart; helps fight infections and diseases. (Chap. 19, Sec. 3, p. 562) ENGLISH GLOSSARY lymph node: bean-shaped organ found throughout the body that filters out microorganisms and foreign materials taken up by the lymphocytes. (Chap. 19, Sec. 3, p. 563) lymphocyte (LIHM fuh site): a type of white blood cell that fights infection. (Chap. 19, Sec. 3, p. 562) M mammals: endothermic vertebrates that have hair, teeth specialized for eating certain foods, and whose females have mammary glands that produce milk for feeding their young. (Chap. 15, Sec. 2, p. 440) mammary glands: milk-producing glands of female mammals used to feed their young. (Chap. 15, Sec. 2, p. 440) mantle: thin layer of tissue that covers a mollusk’s body organs; secretes the shell or protects the body of mollusks without shells. (Chap. 13, Sec. 1, p. 364) marsupial: a mammal with an external pouch for the development of its immature young. (Chap. 15, Sec. 2, p. 444) mechanical digestion: breakdown of food through chewing, mixing, and churning. (Chap. 18, Sec. 2, p. 529) medusa (mih DEW suh): cnidarian body type that is bell-shaped and freeswimming. (Chap. 12, Sec. 2, p. 343) meiosis (mi OH sus): reproductive process that produces four haploid sex cells from one diploid cell and ensures offspring will have the same number of chromosomes as the parent organisms. (Chap. 4, Sec. 2, p. 105) melanin: pigment produced by the epidermis that protects skin from Sun damage and gives skin and eyes their color. (Chap. 17, Sec. 3, p. 503) menstrual cycle: hormone-controlled monthly cycle of changes in the female reproductive system that includes the maturation of an egg and preparation of the uterus for possible pregnancy. (Chap. 22, Sec. 2, p. 636) English Glossary mutation: any permanent change in a gene or chromosome of a cell; may be beneficial, harmful, or have little effect on an organism. (Chap. 4, Sec. 3, p. 114) mutualism: a type of symbiotic relationship in which both organisms benefit. (Chap. 24, Sec. 3, p. 706) mycorrhizae (mi kuh RI zee): network of hyphae and plant roots that helps plants absorb water and minerals from soil. (Chap. 8, Sec. 2, p. 228) N natural resources: parts of Earth’s environment that supply materials useful or necessary for the survival of living organisms. (Chap. 27, Sec. 1, p. 778) natural selection: organisms with traits best suited to their environment are more likely to survive and reproduce; includes concepts of variation, overproduction, and competition. (Chap. 6, Sec. 1, p. 157) nephron (NEF rahn): tiny filtering unit of the kidney. (Chap. 20, Sec. 2, p. 585) nerve cord: tubelike structure above the notochord that in most chordates develops into the brain and spinal cord. (Chap. 14, Sec. 1, p. 399) neuron (NOO rahn): basic functioning unit of the nervous system; made up of a cell body, dendrites, and axons. (Chap. 21, Sec. 1, p. 601) niche: in an ecosystem, refers to the unique ways an organism survives, obtains food and shelter, and avoids danger. (Chap. 24, Sec. 3, p. 707) nitrogen cycle: model describing how nitrogen moves from the atmosphere to the soil, to living organisms, and then back to the atmosphere. (Chap. 25, Sec. 2, p. 730) ENGLISH GLOSSARY English Glossary menstruation (men STRAY shun): monthly flow of blood and tissue cells that occurs when the lining of the uterus breaks down and is shed. (Chap. 22, Sec. 2, p. 636) metabolism: the total of all chemical reactions in an organism. (Chap. 3, Sec. 3, p. 81) metamorphosis: process in which many insect species change their body form to become adults; can be complete (egg, larva, pupa, adult) or incomplete (egg, nymph, adult). (Chap. 13, Sec. 3, p. 376) migration: instinctive seasonal movement of animals to find food or to reproduce in better conditions. (Chap. 16, Sec. 2, p. 474) mineral: inorganic nutrient that regulates many chemical reactions in the body. (Chap. 18, Sec. 1, p. 524) mitochondrion: cell organelle that breaks down lipids and carbohydrates and releases energy. (Chap. 2, Sec. 1, p. 42) mitosis (mi TOH sus): cell process in which the nucleus divides to form two nuclei identical to each other, and identical to the original nucleus, in a series of steps (prophase, metaphase, anaphase, and telophase). (Chap. 4, Sec. 1, p. 98) mixture: a combination of substances in which the individual substances do not change or combine chemically but instead retain their own individual properties; can be gases, solids, liquids, or any combination of them. (Chap. 3, Sec. 1, p. 69) molting: shedding and replacing of an arthropod’s exoskeleton. (Chap. 13, Sec. 3, p. 374) monocot: angiosperm with one cotyledon inside its seed, flower parts arranged in multiples of three, and vascular tissues in bundles scattered throughout the stem. (Chap. 9, Sec. 3, p. 260) muscle: organ that can relax, contract, and provide the force to move bones and body parts. (Chap. 17, Sec. 2, p. 496) 875 English Glossary English Glossary nitrogen fixation: process in which some types of bacteria in the soil change nitrogen gas into a form of nitrogen that plants can use. (Chap. 25, Sec. 2, p. 730) nitrogen-fixing bacteria: bacteria that convert nitrogen in the air into forms that can be used by plants and animals. (Chap. 7, Sec. 2, p. 196) noninfectious disease: disease, such as cancer, diabetes, or asthma, that is not spread from one person to another. (Chap. 23, Sec. 3, p. 672) nonrenewable resources: natural resources, such as petroleum, minerals, and metals, that are used more quickly than they can be replaced by natural processes. (Chap. 27, Sec. 1, p. 779) nonvascular plant: plant that absorbs water and other substances directly through its cell walls instead of through tubelike structures. (Chap. 9, Sec. 1, p. 247) notochord: firm but flexible structure that extends along the upper part of a chordate’s body. (Chap. 14, Sec. 1, p. 398) nuclear energy: energy produced from the splitting apart of billions of uranium nuclei by a nuclear fission reaction. (Chap. 27, Sec. 1, p. 782) nucleus: organelle that controls all the activities of a cell and contains hereditary material made of proteins and DNA. (Chap. 2, Sec. 1, p. 40) nutrients (NEW tree unts): substances in foods—proteins, carbohydrates, fats, vitamins, minerals, and water—that provide energy and materials for cell development, growth, and repair. (Chap. 18, Sec. 1, p. 518) O olfactory (ohl FAK tree) cell: nasal nerve cell that becomes stimulated by molecules in the air and sends impulses to the brain for interpretation of odors. (Chap. 21, Sec. 2, p. 615) 876 ENGLISH GLOSSARY omnivore: animal that eats plants and animals or animal flesh. (Chap. 12, Sec. 1, p. 335) (Chap. 15, Sec. 2, p. 441) open circulatory system: blood circulation system in which blood moves through vessels and into open spaces around the body organs. (Chap. 13, Sec. 1, p. 364) organ: structure, such as the heart, made up of different types of tissues that work together. (Chap. 2, Sec. 1, p. 45) organelle: structure in the cytoplasm of a eukaryotic cell that can act as a storage site, process energy, move materials, or manufacture substances. (Chap. 2, Sec. 1, p. 40) organic compounds: compounds that always contain hydrogen and carbon; carbohydrates, lipids, proteins, and nucleic acids are organic compounds found in living things. (Chap. 3, Sec. 1, p. 70) organism: any living thing; uses energy, is made of cells, reproduces, responds, grows, and develops. (Chap. 1, Sec. 2, p. 14) osmosis: a type of passive transport that occurs when water diffuses through a cell membrane. (Chap. 3, Sec. 2, p. 76) ovary: female reproductive organ that produces eggs and is located in the lower part of the body. (Chap. 10, Sec. 3, p. 287) (Chap. 22, Sec. 2, p. 635) ovulation (ahv yuh LAY shun): monthly process in which an egg is released from an ovary and enters the oviduct, where it can become fertilized by sperm. (Chap. 22, Sec. 2, p. 635) ovule: in gymnosperms, the female reproductive part that produces eggs and food-storage tissues. (Chap. 10, Sec. 3, p. 285) ozone depletion: thinning of Earth’s ozone layer caused by chlorofluorocarbons (CFCs) leaking into the air and reacting chemically with ozone, breaking the ozone molecules apart. (Chap. 27, Sec. 2, p. 789) English Glossary P ENGLISH GLOSSARY English Glossary parasitism: a type of symbiotic relationship in which one organism benefits and the other organism is harmed. (Chap. 24, Sec. 3, p. 706) passive immunity: immunity that results when antibodies produced in one animal are introduced into another’s body; does not last as long as active immunity. (Chap. 23, Sec. 1, p. 661) passive transport: movement of substances through a cell membrane without the use of cellular energy; includes diffusion, osmosis, and facilitated diffusion. (Chap. 3, Sec. 2, p. 74) pasteurization (pas chur ruh ZAY shun): process in which a liquid is heated to a temperature that kills most bacteria. (Chap. 23, Sec. 2, p. 663) pathogen: disease-producing organism. (Chap. 7, Sec. 2, p. 199) periosteum (pur ee AHS tee um): tough, tight-fitting membrane that covers a bone’s surface and contains blood vessels that transport nutrients into the bone. (Chap. 17, Sec. 1, p. 491) peripheral nervous system: division of the nervous system; made up of all the nerves outside the CNS; connects the brain and spinal cord to other body parts. (Chap. 21, Sec. 1, p. 603) peristalsis (per uh STAHL sus): waves of muscular contractions that move food through the digestive tract. (Chap. 18, Sec. 2, p. 532) petroleum: nonrenewable resource formed over hundreds of millions of years, mostly from the remains of microscopic marine organisms buried in Earth’s crust. (Chap. 27, Sec. 1, p. 779) pharynx (FER ingks): tubelike passageway for food, liquid, and air. (Chap. 20, Sec. 1, p. 576) phenotype (FEE nuh tipe): outward physical appearance and behavior of an organism. (Chap. 5, Sec. 1, p. 130) pheromone (FER uh mohn): powerful chemical produced by an animal to influence the behavior of another animal of the same species. (Chap. 16, Sec. 2, p. 469) phloem (FLOH em): vascular tissue that forms tubes that transport dissolved sugar throughout a plant. (Chap. 9, Sec. 3, p. 257) photoperiodism: a plant’s response to the lengths of daylight and darkness each day. (Chap. 11, Sec. 2, p. 318) photosynthesis (foh toh SIHN thuh suhs): food-making process by which plants and many other producers use light energy to produce glucose and oxygen from carbon dioxide and water. (Chap. 3, Sec. 3, p. 82)(Chap. 11, Sec. 1, p. 307) phylogeny (fi LAH juh nee): evolutionary history of an organism; used by scientists to group organisms into kingdoms. (Chap. 1, Sec. 4, p. 23) pioneer species: first organisms to grow in new or disturbed areas; break down rock and build soil. (Chap. 9, Sec. 2, p. 249) (Chap. 26, Sec. 1, p. 748) pistil: female reproductive organ inside the flower of an angiosperm; consists of an ovary and a sticky stigma, where pollen grains land. (Chap. 10, Sec. 3, p. 287) placenta: a saclike organ in which a placental embryo develops; absorbs oxygen and food from the mother’s blood. (Chap. 15, Sec. 2, p. 445) placental: a mammal whose offspring develop inside a placenta in the female’s uterus. (Chap. 15, Sec. 2, p. 445) plasma: liquid part of blood, made mostly of water, in which oxygen, nutrients, and minerals are dissolved. (Chap. 19, Sec. 2, p. 556) platelet: irregularly shaped cell fragment that helps clot blood and releases chemicals that help form fibrin. (Chap. 19, Sec. 2, p. 557) pollen grain: small structure produced by the male reproductive organs of a seed plant; has a water-resistant coat, can develop from a spore, and contains gametophyte parts that will produce sperm. (Chap. 10, Sec. 3, p. 283) 877 English Glossary English Glossary 878 pollination: transfer of pollen grains to the female part of a seed plant by agents such as gravity, water, wind, and animals. (Chap. 10, Sec. 3, p. 283) pollutant: substance that contaminates any part of the environment. (Chap. 27, Sec. 2, p. 786) polygenic (pahl ih JEHN ihk) inheritance: occurs when a group of gene pairs acts together and produces a specific trait, such as human eye color, skin color, or height. (Chap. 5, Sec. 2, p. 136) polyp (PAH lup): cnidarian body type that is vase-shaped and is usually sessile. (Chap. 12, Sec. 2, p. 343) population: all the organisms that belong to the same species living in a community. (Chap. 24, Sec. 1, p. 694) postanal tail: muscular structure at the end of a developing chordate. (Chap. 14, Sec. 1, p. 398) preening: process in which a bird rubs oil from an oil gland over its feathers to condition them and make them water repellent. (Chap. 15, Sec. 1, p. 434) pregnancy: period of development—usually about 38 or 39 weeks in humans—from fertilized egg until birth. (Chap. 22, Sec. 3, p. 640) primates: group of mammals including humans, monkeys, and apes that share characteristics such as opposable thumbs, binocular vision, and flexible shoulders. (Chap. 6, Sec. 3, p. 170) producer: organism, such as a green plant or alga, that uses an outside source of energy like the Sun to create energy-rich food molecules. (Chap. 24, Sec. 3, p. 704) protein: nutrient made up of amino acids that is used by the body for growth and for replacement and repair of body cells. (Chap. 18, Sec. 1, p. 519) prothallus (proh THA lus): small, green, heart-shaped gametophyte plant form of a fern that can make its own food and absorb water and nutrients from the soil. (Chap. 10, Sec. 2, p. 280) ENGLISH GLOSSARY protist: one- or many-celled eukaryotic organism that can be plantlike, animal-like, or funguslike. (Chap. 8, Sec. 1, p. 212) protozoan: one-celled, animal-like protist that can live in water, soil, and living and dead organisms. (Chap. 8, Sec. 1, p. 217) pseudopods (SEWD uh pahdz): temporary cytoplasmic extensions used by some protists to move about and trap food. (Chap. 8, Sec. 1, p. 218) pulmonary circulation: flow of blood through the heart to the lungs and back to the heart. (Chap. 19, Sec. 1, p. 548) punctuated equilibrium: model describing the rapid evolution that occurs when mutation of a few genes results in a species suddenly changing into a new species. (Chap. 6, Sec. 1, p. 160) Punnett (PUN ut) square: a tool to predict the probability of certain traits in offspring that shows the different ways alleles can combine. (Chap. 5, Sec. 1, p. 130) R radial symmetry: body parts arranged in a circle around a central point. (Chap. 12, Sec. 1, p. 339) radioactive element: element that gives off a steady amount of radiation as it slowly changes to a nonradioactive element. (Chap. 6, Sec. 2, p. 165) radula (RA juh luh): in gastropods, the tonguelike organ with rows of teeth used to scrape and tear food. (Chap. 13, Sec. 1, p. 365) recessive (rih SES ihv): describes a trait that is covered over, or dominated, by another form of that trait and seems to disappear. (Chap. 5, Sec. 1, p. 129) recycling: conservation method that is a form of reuse and requires changing or reprocessing an item or natural resource. (Chap. 27, Sec. 3, p. 797) English Glossary S saprophyte: organism that feeds on dead or decaying tissues of other organisms. (Chap. 7, Sec. 2, p. 196) (Chap. 8, Sec. 2, p. 224) scales: thin, hard plates that cover a fish’s skin and protect its body. (Chap. 14, Sec. 2, p. 403) scientific method: problem-solving techniques used to investigate observations that can be made about living and nonliving things; may include stating a problem, gathering information, forming and testing a hypothesis, analyzing data, and drawing conclusions. (Chap 1, Sec. 1, p. 7) sedimentary rock: a type of rock, such as limestone, that is most likely to contain fossils and is formed when layers of sand, silt, clay, or mud are cemented and compacted together or when minerals are deposited from a solution. (Chap. 6, Sec. 2, p. 164) semen (SEE mun): mixture of sperm and a fluid that helps sperm move and supplies them with an energy source. (Chap. 22, Sec. 2, p. 634) sessile (SE sile): describes an organism that remains attached to one place during its lifetime. (Chap. 12, Sec. 2, p. 341) setae (SEE tee): bristlelike structures on the outside of each body segment that helps segmented worms move. (Chap. 13, Sec. 2, p. 369) sex-linked gene: an allele inherited on a sex chromosome; can cause human genetic disorders such as color blindness and hemophilia. (Chap. 5, Sec. 2, p. 139) sexual reproduction: a type of reproduction in which two sex cells, usually an egg and a sperm, join to form a zygote, which will develop into a new organism with a unique identity. (Chap. 4, Sec. 2, p. 104) sexually transmitted disease (STD): infectious disease, such as chlamydia, AIDS, or genital herpes, that is passed from one person to another during sexual contact. (Chap. 23, Sec. 2, p. 668) short-day plant: plant that generally requires long nights—12 or more hours of darkness—to begin the flowering process. (Chap. 11, Sec. 2, p. 318) skeletal muscle: voluntary, striated muscle that moves bones, works in pairs, and is attached to bones by tendons. (Chap. 17, Sec. 2, p. 499) skeletal system: all the bones in the body; forms an internal, living framework that provides shape and support, protects internal organs, moves bones, forms blood cells, and stores calcium and phosphorus compounds for later use. (Chap. 17, Sec. 1, p. 490) ENGLISH GLOSSARY English Glossary reflex: simple innate behavior, such as yawning or blinking, that is an automatic response and does not involve a message to the brain. (Chap. 16, Sec. 1, p. 461) (Chap. 21, Sec. 1, p. 607) renewable resources: natural resources, such as water, sunlight, and crops, that are constantly being recycled or replaced by nature. (Chap. 27, Sec. 1, p. 778) respiration: series of chemical reactions used to release energy stored in food molecules. (Chap. 3, Sec. 3, p. 83) (Chap. 11, Sec. 1, p. 309) retina: light-sensitive tissue at the back of the eye; contains rods and cones. (Chap. 21, Sec. 2, p. 611) rhizoids (RI zoydz): threadlike structures that anchor nonvascular plants to the ground. (Chap. 9, Sec. 2, p. 248) rhizome: underground stem of a fern. (Chap. 10, Sec. 2, p. 280) ribosome: small structure on which cells make their own proteins. (Chap. 2, Sec. 1, p. 42) RNA: ribonucleic acid, which carries codes for making proteins from the nucleus to the ribosomes. (Chap. 4, Sec. 3, p. 112) 879 English Glossary English Glossary 880 smooth muscle: involuntary, nonstriated muscle that controls movement of internal organs. (Chap. 17, Sec. 2, p. 499) social behavior: interactions among members of the same species, including courtship and mating, getting food, caring for young, and protecting each other. (Chap. 16, Sec. 2, p. 466) society: a group of animals of the same species that live and work together in an organized way, with each member doing a specific job. (Chap. 16, Sec. 2, p. 467) soil: mixture of mineral and rock particles, the remains of dead organisms, air, and water that forms the topmost layer of Earth’s crust and supports plant growth. (Chap. 25, Sec. 1, p. 722) sori: fern structures in which spores are produced. (Chap. 10, Sec. 2, p. 280) species: group of organisms that share similar characteristics and can reproduce among themselves. (Chap. 6, Sec. 1, p. 154) sperm: haploid sex cells formed in the male reproductive organs. (Chap. 4, Sec. 2, p. 104) (Chap. 22, Sec. 2, p. 634) spiracles (SPIHR ih kulz): openings in the abdomen and thorax of insects through which air enters and waste gases leave. (Chap. 13, Sec. 3, p. 375) spontaneous generation: theory that living things can come from nonliving things. (Chap. 1, Sec. 3, p. 19) sporangium (spuh RAN jee uhm): round spore case of a zygote fungus. (Chap. 8, Sec. 2, p. 227) spore: waterproof reproductive cell of a fungus. (Chap. 8, Sec. 2, p. 225) spores: haploid cells produced in the gametophyte stage of a plant that can divide by mitosis and form structures or an entire new plant or can develop into sex cells. (Chap. 10, Sec. 1, p. 277) sporophyte (SPOR uh fite) stage: plant life cycle stage that begins when an egg is fertilized by a sperm. (Chap. 10, Sec. 1, p. 277) ENGLISH GLOSSARY stamen: male reproductive organ inside the flower of an angiosperm; consists of an anther, where pollen grains form, and a filament. (Chap. 10, Sec. 3, p. 287) stinging cells: capsules with coiled triggerlike structures that help cnidarians capture food. (Chap. 12, Sec. 2, p. 344) stomata (STOH muh tuh): small openings in the surface of most plant leaves that allow carbon dioxide, water, and oxygen to enter and exit. (Chap. 9, Sec. 3, p. 255) (Chap. 11, Sec, 1, p. 305) succession: natural, gradual changes in the types of species that live in an area; can be primary or secondary. (Chap. 26, Sec. 1, p. 748) symbiosis: any close relationship between species, including mutualism, commensalism, and parasitism. (Chap. 24, Sec. 3, p. 706) synapse (SIHN aps): small space across which an impulse moves from an axon to the dendrites or cell body of another neuron. (Chap. 21, Sec. 1, p. 603) systemic circulation: largest part of the circulatory system in which oxygen-rich blood flows to all the organs and body tissues, except the heart and lungs, and oxygen-poor blood is returned to the heart. (Chap. 19, Sec. 1, p. 549) T taiga (TI guh): world’s largest biome, located south of the tundra between 50º N and 60º N latitude; has long, cold winters, precipitation between 35 cm and 100 cm each year, cone-bearing evergreen trees, and dense forests. (Chap. 26, Sec. 2, p. 754) taste bud: major sensory receptor on the tongue; contains taste hairs that send impulses to the brain for interpretation of tastes. (Chap. 21, Sec. 2, p. 616) English Glossary U umbilical cord: connects the embryo to the placenta; moves food and oxygen from the placenta to the embryo and removes the embryo’s waste products. (Chap. 15, Sec. 2, p. 445) ureter: tube that carries urine from each kidney to the bladder. (Chap. 20, Sec. 2, p. 586) urethra (yoo REE thruh): tube that carries urine from the bladder to the outside of the body. (Chap. 20, Sec. 2, p. 586) urinary system: system of excretory organs that rids the blood of wastes, controls blood volume by removing excess water, and balances concentrations of salts and water. (Chap. 20, Sec. 2, p. 583) urine: wastewater that contains excess water, salts, and other wastes that are not reabsorbed by the body. (Chap. 20, Sec. 2, p. 584) uterus: hollow, muscular, pear-shaped organ where a fertilized egg develops into a baby. (Chap. 22, Sec. 2, p. 635) English Glossary temperate deciduous forest: biome usually having four distinct seasons, annual precipitation between 75 cm and 150 cm, and climax communities of deciduous trees. (Chap. 26, Sec. 2, p. 755) temperate rain forest: biome with 200 cm to 400 cm of precipitation each year, average temperatures between 9ºC and 12ºC, and forests dominated by trees with needlelike leaves. (Chap. 26, Sec. 2, p. 755) tendon: thick band of tissue that attaches bones to muscles. (Chap. 17, Sec. 2, p. 499) tentacles (TEN tih kulz): armlike structures that have stinging cells and surround the mouths of most cnidarians. (Chap. 12, Sec. 2, p. 344) testis: male organ that produces sperm and testosterone. (Chap. 22, Sec. 2, p. 634) theory: an explanation of events or things based on scientific knowledge resulting from repeated observations and tests. (Chap. 1, Sec. 1, p. 10) tissue: group of similar cells that work together to do one job. (Chap. 2, Sec. 1, p. 45) toxin: poisonous substance produced by some pathogens. (Chap. 7, Sec. 2, p. 199) trachea (TRAY kee uh): air-conducting tube that connects the larynx with the bronchi, is lined with mucous membranes and cilia, and contains strong cartilage rings. (Chap. 20, Sec. 1, p. 577) tropical rain forest: most biologically diverse biome; has an average temperature of 25ºC and receives between 200 cm and 600 cm of precipitation each year. (Chap. 26, Sec. 2, p. 756) tropism: positive or negative plant response to an external stimulus such as touch, light, or gravity. (Chap. 11, Sec. 2, p. 314) tube feet: hydraulic, hollow, thin-walled tubes that end in suction cups and enable echinoderms to move. (Chap. 13, Sec. 4, p. 384) tundra: cold, dry, treeless biome with less than 25 cm of precipitation each year, a short growing season, permafrost, and winters that can be six to nine months long. (Chap. 26, Sec. 2, p. 753) V vaccination: process of giving a vaccine by mouth or by injection to provide active immunity against a disease. (Chap. 23, Sec. 1, p. 661) vaccine: preparation made from killed bacteria or damaged particles from bacterial cell walls that can prevent some bacterial diseases. (Chap. 7, Sec. 2, p. 201) vagina (vuh JI nuh): muscular tube that connects the lower end of the uterus to the outside of the body; the birth canal through which a baby travels when being born. (Chap. 22, Sec. 2, p. 635) variable: in an experiment, the one thing that can change. (Chap. 1, Sec. 1, p. 9) variation: inherited trait that makes an individual different from other members of the same species and results from a mutation in the organism’s genes. (Chap. 6, Sec. 1, p. 158) ENGLISH GLOSSARY 881 English Glossary English Glossary 882 vascular plant: plant with tubelike structures that move minerals, water, and other substances throughout the plant. (Chap. 9, Sec. 1, p. 247) vein: blood vessel that carries blood back to the heart and has one-way valves that keep blood moving toward the heart. (Chap. 19, Sec. 1, p. 550) ventricles (VEN trih kulz): two lower chambers of the heart that contract at the same time during a heartbeat. (Chap. 19, Sec. 1, p. 547) vertebrae: backbones that are joined by flexible cartilage and protect a vertebrate’s spinal nerve cord. (Chap. 14, Sec. 1, p. 399) vertebrate: animal with a backbone. (Chap. 12, Sec. 1, p. 338) vestigial (veh STIHJ ee ul) structure: structure, such as the human appendix, that doesn’t seem to have a function and may once have functioned in the body of an ancestor. (Chap. 6, Sec. 2, p. 168) villi (VIHL I): fingerlike projections covering the wall of the small intestine that increase the surface area for food absorption. (Chap. 18, Sec. 2, p. 534) virus: extremely tiny piece of genetic material that infects and multiplies in host cells; surrounded by a protein coating. (Chap. 2, Sec. 3, p. 52) (Chap. 23, Sec. 2, p. 664) vitamin: water-soluble or fat-soluble organic nutrient needed in small quantities for growth, for preventing some diseases, and for regulating body functions. (Chap. 18, Sec. 1, p. 522) voluntary muscle: muscle, such as a leg or arm muscle, that can be consciously controlled. (Chap. 17, Sec. 2, p. 497) ENGLISH GLOSSARY W water cycle: model describing how water moves from Earth’s surface to the atmosphere and back to the surface again through evaporation, condensation, and precipitation. (Chap. 25, Sec. 2, p. 729) water-vascular system: network of waterfilled canals that allows echinoderms to move, capture food, give off wastes, and exchange carbon dioxide and oxygen. (Chap. 13, Sec. 4, p. 384) wetland: a region that is wet most or all of the year. (Chap. 26, Sec. 3, p. 763) X xylem (ZI lum): vascular tissue that forms hollow vessels that transport substances, other than sugar, throughout a plant. (Chap. 9, Sec. 3, p. 257) Z zygote: new diploid cell formed when a sperm fertilizes an egg; will divide by mitosis and develop into a new organism. (Chap. 4, Sec. 2, p. 104)