Biology SAT Subject Test Questions And Answers

Biology SAT Subject Test acetylcholine - A neurotransmitter released by neurons to excite an action potential or trigger a muscle to contract. actin - Protein filaments that, along with myosin, allow muscles to contract. adaptive radiation - The evolutionary process by which ancestral forms of an organism are diversified through adaptation to new environments. allelic frequency - The frequency with which a particular allele for a certain characteristic appears among all possible alleles for that characteristic in a population alternation of generations - The fluctuation between the diploid (sporophyte) and haploid (gametophyte) life stages that occur in plants. amino acid - The monomer of a protein. A central carbon attached to an amino group (-NH2), a carboxyl group (-COOH), and a hydrogen atom (-H). The fourth group is variable and defines the amino acid's chemical identity. analogous trait - A trait that is morphologically and functionally similar to that of a different species but that arose from a distinct, ancestral condition. angiosperm - A vascular flowering plant in which seeds are enclosed inside protective ovaries, such as fruit or flowers. Angiosperms can be monocots or dicots. anther - Pollen-producing structure at the top of the stamen, the male reproductive organ of flowers. aorta - The largest artery in the body; carries oxygenated blood from the left ventricle of the heart. aphotic zone - Literally, zone without light. The aphotic zone is part of the marine pelagic zone and begins 600 feet below the surface of the ocean. Only chemosynthetic organisms, scavengers, and predators are able to survive in this habitat. artery - Vessel that carries blood away from the heart and has thick, elastic, muscular walls that can dilate or contract to control blood pressure within the vessels. Blood in arteries is oxygenated, with the exception of the blood in the pulmonary artery. autonomic nervous system - The involuntary half of the peripheral nervous system. The autonomic nervous system is in two antagonistic parts: the sympathetic and parasympathetic nervous systems. Their interactions control smooth and cardiac muscle, glands, and organs and processes such as heartbeat, the movements of the digestive tract, and the contraction of the bladder. autotroph - An organism that can produce the organic molecules and energy necessary for life through the processes of photosynthesis or chemosynthesis. Autotrophs do not rely on other organisms for food. In a food web, autotrophs are producers. auxin - One in a class of plant hormones that stimulates (among other things) cell elongation, secondary tissue growth, and fruit development. bile - An emulsifier of fats secreted by the liver and stored in the gallbladder for release in the small intestine. biomass - The amount of living matter in a given ecosystem. Because only 10 percent of energy is transferred between trophic levels, the biomass of lower trophic levels is greater than the biomass of subsequent trophic levels: biomass of producers biomass of primary consumers biomass of secondary consumers biomass of tertiary consumers. biome - A particular geographic area with a common climate and characteristic plant and animal life. There are six major terrestrial biomes and two aquatic biomes. The six terrestrial biomes are tropical rain forest, savanna, desert, temperate deciduous forest, taiga, and tundra. The two aquatic biomes are marine and freshwater. Each biome is characterized by specific climax communities. blood - The liquid that carries nutrients and oxygen to the cells and carries carbon dioxide and nitrogenous wastes away. The liquid fluid of blood is called plasma. Red blood cells contain hemoglobin, an iron-containing protein that binds oxygen. White blood cells fight disease. Platelets clot to prevent extreme blood loss resulting from injury. bone - Rigid structures composed of living cells rooted in a matrix of calcium, phosphate salts, and collagen fibers. Bones are the primary component of most vertebrate skeletons. brain - The center of the central nervous system. The brain coordinates the processes of the body. It is composed of various distinct regions, all of which have different functions, including the cerebrum, cerebellum, medulla oblongata, and hypothalamus. bryophyte - A lower terrestrial plant (often a moss or liverwort) that lacks a vascular system and is dependent on environmental moisture for reproductive and nutritive functions. budding - Asexual reproductive process in which a small portion of the cell membrane and cytoplasm receive a nucleus and pinch off from the parent cell. bulb - Roughly spherical underground bud containing additional buds that can develop asexually into new plants. Calvin cycle - Light-independent phase of photosynthesis, where carbon dioxide is fixed to a three-carbon compound used to form glucose. ATP and NADH are consumed in this cycle. Also called the Calvin-Benson cycle or the dark reactions. capillary - Tiny blood vessels able to branch through the body and deliver oxygen and nutrients to every cell. carbon - The central element of life. Carbon has the ability to form bonds with up to four other elements or molecules at the same time. carrying capacity - The maximum number of individuals in a population that can be sustained in a given environment. As populations become increasingly concentrated, competition for food and space, predation, and disease all determine carrying capacity. cartilage - A firm but flexible substance, found in regions of vertebrate skeletons, such as the ribs, that need to bend. cellular respiration - The process in which the cell burns glucose to create ATP with the aid of oxygen. Cells have two different methods of turning food into usable fuel: aerobic respiration and anaerobic respiration. cellulose - A complex carbohydrate that constitutes the cell walls of plants and protist molds. cerebellum - Part of the brain. Makes sure that movements are coordinated and balanced. cerebrum - Part of the brain. Controls all voluntary movement, sensory perception, speech, memory, and creative thought. chemical cycles - The cycles in which inorganic elements move through the biotic and abiotic aspects of an ecosystem. The two most important chemical cycles are the carbon and nitrogen cycles. chemosynthesis - Synthesizing organic compounds by energy derived from chemical reactions rather than from the energy of the sun. Chemosynthetic organisms are autotrophs. chitin - A rough polysaccharide that constitutes the cell wall of fungi and exoskeleton of arthropods. circadian rhythms - Behavior cycles that depend on time of day. circulatory system - System of organs and blood that brings nutrients and oxygen to cells and carries away wastes. In higher vertebrates, the system has a pulmonary and systemic circuit. The pulmonary circuit carries blood to the lungs to be oxygenated, while the systemic circuit carries oxygenated blood to the body. Vertebrates have a closed circulatory system, while arthropods have an open system. climax community - A combination of plant and animal forms that dominate mature ecological communities. Climax communities are unique and shaped by various factors, including temperature, rainfall, and soil acidity. codominance - A phenomenon in which two alleles of the same gene are fully expressed in the phenotype when both are present in a heterozygote. Blood type is an example of codominance. cold-blooded - Animals that are unable to retain heat produced by metabolic activities. Also known as ectothermic. The metabolism of cold-blooded animals is greatly influenced by climate and temperature. community - The many populations that interact in a given geographical locale constitute ecological communities. Communities exhibit particular interactions such as competition, symbiosis, predation, and food relationships. They also undergo ecological succession. competition - The struggle for survival between organisms or populations that use similar resources and occupy similar niches. Interspecific competition refers to competition between populations that may drive a population out of a community or push it to evolve a different niche to reduce competition. Intraspecific competition refers to competition between individuals of the same species. consumer - Consumers are heterotrophic organisms within the food web of a community. In the trophic levels of the food chain, primary consumers consume producers, secondary consumers consume primary consumers, and tertiary consumers consume secondary consumers. contractile vacuole - An organelle often found in protozoa that pumps excess water out of the cell to keep the cell from bursting in a hypotonic environment (like freshwater). cytosol - The main component of the cytoplasm. It is a grayish, gel-like liquid containing the nucleus, organelles, and cytoskeleton. decomposer - Organisms that consume waste products and dead organic material and constitute part of the food web, which also includes producers and consumers. Also called saprophytes. Decomposers liberate inorganic elements such as nitrogen and carbon and allow those elements to move back into their respective chemical cycles. Examples of decomposers are bacteria and fungi. dehydration synthesis - A common biochemical reaction in which a new compound is formed by the joining of two compounds to release water. Occurs in the synthesis of polysaccharides and polypeptides. The reverse of hydrolysis. dicot - A flowering plant (angiosperm) that possesses two cotyledons during embryonic development. Usually has taproots, flower parts in multiples of fours and fives, and branching veins in leaves. diffusion - The transport or natural drift of molecules traveling from an area of higher concentration to an area of lower concentration. Diffusion does not require outside energy from the cell.