SAT Subject Bio Glossary Crack SAT Flashcards
abiotic
Nonliving materials in the environment—such as elements, sunlight, and soil—that influence and are influenced by living (biotic) entities on the planet.
Acetylcholine
A neurotransmitter released from the axons of nerve cells to excite an action potential or trigger a muscle to contract.
active immunity
Protective immunity to a disease in which the individual produces antibodies as a result of previous exposures to the antigen.
Acids
Hydrogenion (H+) donors. Acids are very important in the chemical reactions of life because they are highly reactive. Acids have pH values below 7. They are the opposite of bases.
actin
Protein filaments that, along with myosin, allow muscles to contract.
active site
The part of an enzyme that interacts with, or binds to, a substrate.
active transport
The movement of molecules across a cell membrane from a region of lower concentration to a region of higher concentration. Because active transport involves moving the molecule against the natural flow of the concentration gradient, the process requires energy.
adaptive radiation
The evolutionary process by which ancestral forms of an organism are diversified through adaptation to new environments.
adenosine triphosphate (ATP)
The energy storage molecule for the cell. ATP consists of an adenosine molecule bonded to three phosphate groups. Each phosphate bond contains energy; by breaking these bonds, the cell can get the energy it needs for chemical
reactions. Cells build ATP during cell respiration, using the raw material of glucose.
adrenal glands
Two glands, the adrenal cortex (cortisone, aldosteron) and adrenal medulla (adrenaline) located on the kidney.
aerobic respiration
A form of cell respiration requiring oxygen(as opposed to an aerobic respiration, which does not need oxygen). Aerobic respiration is much more efficient than anaerobic respiration; it produces 36 ATP for every molecule of glucose. Aerobic respiration proceeds in three stages: glycolysis ,the Krebs cycle, and the electron transport chain
allantois
The extra embryonic membrane of birds, reptiles, and mammals that serves as an area of gaseous exchange and as a site for the storage of noxious excretion products.
allele
A specific form or possible version of a gene having multiple versions. Alleles may be dominant or recessive.
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.
alveolus
An air sac in the lung, the site of respiratory exchange.
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.
Amnion
The extra embryonic membrane in birds, reptiles, and mammals that surrounds the embryo, forming an amniotic sac.
anaerobic respiration
A form of cell respiration that does not use oxygen(as opposed to aerobic cell respiration). Anaerobic respiration is less efficient than the aerobic variety and produces just 2 ATP per molecule of glucose. Anaerobic respiration has two stages: glycolysis and fermentation.
analogous trait
A trait that is morphologically and functionally similar to that of a different species but that arose from a distinct, ancestral condition.
anaphase
The stage of mitosis in which sister chromosomes are separated and pulled to opposite ends of the cell by microtubules; the fourth stage of the first meiotic division(meiosis I), during which maternal and paternal homologous pairs are separated on microtubules; the fourth stage of the second meiotic division(meiosis II), during which either maternal or paternal sister chromatids are separated on microtubules.
androgen
A male sex hormone. (e.g.testosterone)
Angiosperm
Avascular 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.
Anticodon
The sequence of three nucleotides on tRNA that pairs with a codon of mRNA at the A site of a ribosome during translation. (tRNA, mRNA)
Antigen
A protein coat on the surface of red blood cells; a red blood cell may have a protein coat of typeA, B, or AB. If the cell has no antigens, it is called type O. The presence of a foreign antigen in a body will cause blood to clot.
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.
Appendage
A structure that extends from the trunk of an organism and is capable of active movements.
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.
Autosome
Any chromosome that is not a sex chromosome. Humans have 44 autosomes, in 22 homologous pairs. The two sex chromosomes are the twenty-third pair of chromosomes.
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.
Base
An ion or compound that removes H+ ions from solution. Often bases are substances that release hydroxide ions (OH–). Bases have pH values above 7. They are the opposite of acids.
Bile
An emulsifier of fats secreted by the liver and stored in the gallbladder for release in the small intestine.
binary fission
Asexual reproduction found in prokaryotes in which a cell divides into two equal daughter cells by a nonmitotic process.
Biomass
The amount of living matter in a given ecosystem. Because only 10 percent of energy is transferred between trophic levels, the biomass o flower 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 rainforest, 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.
Buffer
Solutions that resist change in pH even when acids and bases are added.
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.
Cell
The smallest unit of life, consisting of a solution of organic molecules enclosed by a plasma membrane.
cell cycle
Inter-pro-meta-ana-telo)
A process in which cells reproduce. First the cell replicates its DNA and then divides into two daughter cells. The two main phases of the cell cycle are interphase and mitosis.
cell membrane
The phospholipid bilayer that surrounds all cells, regulating the passage of molecules in and out of the cell.
cellular respiration
The process in which the cell burns glucose to createATP with the aid of oxygen. Cells have two different methods of turning food in to usable fuel: aerobic respiration and anaerobic respiration.
cell theory
The doctrine that every living organism is composed of cells and that all cells come only from other preexisting
cells.
cell wall
A rigid structure that surrounds the outer membrane of some cells and helps maintain their shape. In plants the cell wall contains cellulose; in fungi it contains chitin; in prokaryotes it typically contains peptidoglycan.
Cellulose
A complex carbohydrate that constitutes the cell walls of plants and protist molds.
central nervous system (CNS)
The brain and the spinal cord. The CNS acts as the central command center of the body. Mostly made up of interneurons.
Centriole
A structure in the cell that plays an important role in cell replication. During prophase, the centrioles migrate to the poles of the cell and form the mitotic spindle, which allows the chromosomes to be organized and split when the cell divides.
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.
Chlorophyll
A pigment located within a chloroplast that absorbs light in plant cells, helping to convert light energy into biological energy through the process of photosynthesis.
Chloroplast
A double-membrane-bound organelle that contains chlorophyll and is found in plant cells. Chloroplasts are responsible for mediating photosynthesis.
Chromatin
The stringy web of genetic material and histone proteins found in the nucleus of eukaryotic cells. During cell division, each strand of DNA coils to form a chromosome.
Chromosome
A physical structure composed of a single long strand of DNA(and associated proteins), containing along its length many genes. The human genome consists of 46 chromosomes contained within the nucleus of each cell.
Cilia
Short, hairlike projections found on eukaryotic cells that can help the cell move or can sweep food particles toward the mouth.
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.
citric acid cycle
also known as Krebs cycle.
A metabolic pathway in aerobic organisms in which acetyl-CoA combines with oxaloacetic acid to form citric acid. The cycle produces energy in the forms of ATP, NADH, andFADH2.
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.
Codon
A three-nucleotide sequence in a DNA or mRNA molecule. Each codon specifies a single amino acid.
Coenzyme
A compound that regulates activity by binding to an enzyme to tell it when to catalyze a reaction.
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).
corpus luteum
After releasing its ovum(ovulation),the follicle becomes the corpus luteum, which produces progesterone for the continued buildup of the uterine wall.
cotyledon
A “SeedLeaf”, responsible for food digestion and storage in a plant embryo.
crossing-over
The exchange of genetic information between homologous chromosomes during meiosis I. Crossing-over can disrupt the normal linkage between genes on the same chromosome.
cretinism
A thyroid deficiency that results in stunted growth and feeble mindedness.
Cytochrome
A hydrogen carrier, containing iron that functions in many cellular processes, including respiration.
Cytokinesis
The final part of mitosis, in which a cell with duplicated contents splits into two independent cells.
Cytoplasm
The entire content of the cell outside the nucleus, including the membrane-bound organelles and the cytosol.
Cytoskeleton
A system of protein filaments found throughout the cytoplasm of eukaryotic cells, which provides structural support for the cell. The cytoskeleton also helps with the movement of organelles within the cell. It is composed of microfilaments and microtubules.
Cytosol
The main component of the cytoplasm. It is a grayish, gel-like liquid containing the nucleus, organelles, and cytoskeleton.
