Sat Subject Bio
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516 terms
Terms | Definitions |
|---|---|
 abiotic | nonliving, as in the physical environment |
| absorption | the process by which water and dissolved substances pass through a membrane |
| acetylcholine | a transmitter substance released from the axons of nerve cells at the synapse |
| active immunity | protective immunity to a disease in which the individual produces antibodies as a result of previous exposure to the antigen |
| adaptation | a behavioral or biological change that enables an organism to adjust to its environment |
| adaptive radiation | the production of a number of different species from a single ancestral species |
| adenosine phosphate | adenosine diphosphate (ADP) and adenosine triphosphate (ATP), which are energy storage molecules |
| ADH (vassopressin) | a hormone that regulates water reabsorption |
| adipose | fatty tissue, fat-storing tissue, or fat within cells |
| adrenal cortex | the outer part of the adrenal gland that secretes many hormones, including cortisone and aldosterone |
| adrenal medulla | the inner part of the adrenal gland that secretes adrenalin |
| adrenaline (epinephrin) | an "emergency" hormone stimulated by anger or fear; increase blood pressure and heart rate in order to supply the emergency needs of the muscles |
| adrenocorticotrophic hormone | usually referred to as ACTH and secreted by the anterior lobe of the pituitary gland; stimulates the adrenal cortex to produce its characteristic hormones |
| aerobe | an organism that requires oxygen for respiration and can live only in the presence of oxygen |
| aerobic | requiring free oxygen from the atmosphere for normal activity and respiration |
| aldosterone | hormone active in osmoregulation; a mineral corticoid produced by the adrenal cortex; stimulates reabsorption of Na+ and secretion of K+ |
| alimentary canal | an organ (group of organs) centrally involved in the human digestive system |
| allantois | the extraembyonic 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 (think umbilical cord) |
| allele | one or two or more types of genes, each representing a particular trait; many alleles exist for a specific gene locus |
| alternation of generations | the description of a plant life cycle that consists of a diploid, asexual, sporophyte generation and a haploid, sexual, gametrophyte generation |
| alveolus | an air sac in the lung; the site of respiratory exchange, involving diffusion of oxygen and carbon dioxide between the air in the alveolus and the blood in the capillaries |
| amnion | the extraembryonic membrane in birds, reptiles and mammals that surrounds the embryo, forming an amniotic sac |
| amoeboid movement | movement involving the flowing of cytoplasm into pseudopods, as in amoeba |
| anaerobe | an organism that does not require free oxygen in order to respire |
| anaerobic | living or active in the absence of free oxygen; pertaining to respiration that is independent of oxygen |
| analogous | describes structures that have similar function but different evolutionary origins; e.g., a bird's wing and a moth's wing |
| anaphase | the stage in mitosis that is characterized by the migration of chromatids to opposite ends of the cell; the stage in meiosis during which homologus pairs migrate (Anaphase I), and the stage in meiosis during which chromatids migrate to different ends of the cell (Anaphase II) |
| androgen | a male sex hormone (e.g., testosterone) |
| angiosperm | a flowering plant; a plant of the class Angiospermae that produces seeds enclosed in an ovary and is characterized by the possession of fruits and flowers |
| Annelida | the phylum to which segmented worms belong |
| anther | the part of the male reproductive organ (the stamen) that produces and stores pollen |
| antibiotic | an antipathogenic substance (e.g., penicillin) |
| antibody | globular proteins produced by tissues that destroy or inactivate antigens, Y shaped |
| antigen | a foreign protein that stimulates the production of antibodies when introduced into the body of an organism |
| aorta | the largest artery; carries blood from the left ventricle |
| aortic arch | blood vessels located between ascending and descending aortas that deliver blood to most of the upper body |
| appendage | a structure that extends from the trunk of an organism and is capable of active movements |
| aqueous humor | fluid in the eye, found between the cornea and the lens |
| Arachnida | a class of arthropods that includes scorpions, spiders, mites and ticks |
| artery | a blood vessel that carries blood away from the heart |
| Arthropoda | the phylum to which jointed-legged invertebrates belong, including insects, arachnids and crustaceans |
| asexual reproduction | the production of daughter cells by means other than the sexual union of gametes (as in budding and binary fission) |
| assimilation | the conversion of digested foods and other materials into forms usable by the body (i.e., the conversion of amino acids into proteins) |
| assortative mating | the type of mating that occurs when an organism selects a mating partner that resembles itself |
| atrium | the thin-walled anterior chamber of the heart (also called the auricle) |
| autolysis | self-digestion occurring in plant and animal tissues, particularly after they have ceased to function properly |
| autonomic nervous system | the part of the nervous system that regulates the involuntary muscles, such as the walls of the alimentary canal; includes the parasympathetic and sympathetic nervous systems |
| autosome | any chromosome that is not a sex chromosome |
| autotroph | an organism that utilizes the energy of inorganic materials such as water and carbon dioxide or the sun to manufacture organic materials |
| auxin | a plant growth hormone |
| axon | a nerve fiber |
| bacillus | bacteria that are rod shaped |
| bacteriophage | a type of virus that can destroy bacteria by infecting, parasitizing and eventually killing them |
| bile | an emulsifying agent secreted by the liver |
| bile salts | compounds in bile that aid in emulsification |
| binary fission | asexual reproduction; in this process, the parent organism splits into two equal daughter cells |
| binomial nomenclature | the system of naming an organism by its genus and species name |
| biome | a habitat zone, such as desert, grassland or tundra |
| biotic | living, as in living organisms in the environment |
| blastula | a stage of embryonic development in which the embryo consists of a hollow ball of cells |
| Bowman's capsule | part of the nephron in the kidney; involved in excretion |
| bud | in plants, an area of undifferentiated tissue covered by embryonic leaves |
| budding | a process of asexual reproduction in which the offspring develop from an outgrowth of the plant or animal |
| buffer | a substance that prevents appreciable changes in pH in solutions to which small quantities of acids or bases are added |
| calorie | a unit of heat; the amount of heat required to raise the temperature of one gram of water by one degree centigrade (note: the uppercase Calorie=1000 calories) |
| Calvin cycle | cycle in photosynthesis that reduces fixed carbon to carbohydrates through the addition of electrons ("dark cycle") |
| cambium | undifferentiated tissue in the stem of a plant that aids growth in width |
| capillary | a tube one cell thick that carries blood from artery to vein; the site of material exchange between the blood and tissues of the body |
| carapace | a bony or chitinous case or shield covering the back or part of the back of an animal (shell of a crab) |
| carbohydrate | an organic compound to which hydrogen and oxygen are attached; the hydrogen and oxygen are in a 2:1 ratio; examples include sugars, starches and cellulose |
| carbon cycle | the recycling of carbon from decaying organisms for use in future generations |
| carnivore | a flesh-eating animal; a holotrophic animal that subsists on other animals or parts of animals |
| carotene | an orange plant pigment that is the precursor of vitamin A |
| cation | an ion with a positive charge, or an ion that migrates towards the cathode (negative electrode) in an electric field |
| cell wall | a wall composed of cellulose that is external to the cell membrane in plants; it is primarily involved in support and in the maintenance of proper internal pressure |
| cell wall plate | in mitosis of higher plants, the structure that forms between the divided nuclei of the two daughter cells and eventually becomes the cell wall |
| central nervous system (CNS) | encompasses the brain and the spinal cord |
| centriole | the small granular body within the centrosome to which the spindle fibers attach |
| centromere | the place of attachment of the mitotic fiber to the chromosome |
| centrosome | a structure in animal cells containing centrioles from which the spindle fibers develop |
| cephalic | pertaining to the head |
| cerebellum | the hindbrain region that controls equilibrium and muscular coordination |
| cerebral cortex | the outer layer of cerebral hemispheres in the forebrain, consisting of gray matter |
| cerebral hemisphere | one of the paired lateral divisions of the forebrain |
| cerebrum | the largest portion of the human brain; it is believed to be the center of intelligence, conscious thought and sensation |
| chemosynthesis | the process by which carbohydrates are formed through chemical energy; found in bacteria |
| chemotropism | the orientation of cells or organisms in relation to chemical stimuli; the growth or movement response of organisms to chemical stimuli |
| chitin | a white or colorless, amorphous, horny substance that forms part of the outer integument of insects, crustaceans and some other invertebrates; it also occurs in certain fungi |
| chlorophyll | a green pigment that performs essential functions as an electron donor and light "entrapper" in photosynthesis |
| chloroplast | a plastid (organelle) containing chlorophyll |
| Chordata | an animal phylum in which all members have a notochord, dorsal nerve cord and pharyngeal gill slits at some embryonic stage; includes the Cephalochordata and the Vertebrates |
| chorion | the outermost, extra-embryonic membrane of reptiles and birds |
| chromatid | one of the two strands that constitute a chromosome; chromatids are held together by the centromere |
| chromatin | a nuclear protein of chromosomes that stains readily |
| chromosome | a short, stubby rod consisting of chromatin that is found in the nucleus of the cells; contains the genetic or hereditary component of cells (in the form of genes) |
| chyme | partially digested food in the stomach |
| circadian rhythms | daily cycles of behavior |
| cleavage | the division in animal cell cytoplasm caused by the pinching in of the cell membrane |
| climax community | the stable, biotic part of the ecosystem in which populations exist in balance with each other and with the environment |
| clotting | the coagulation of blood caused by the rupture of platelets and the interaction of fibrin, fibrinogen, thrombin, prothrombin and calcium ions |
| cloaca | the chamber in the alimentary canal of certain vertebrates located below the large intestine, into which the ureter and reproductive organs empty (as in frogs) |
| cochlea | the sensory organ of the inner ear of mammals; it is coiled and contains the organ of corti |
| codominant | the state in which two genetic traits are fully expressed and neither dominates |
| Coelentrata (Cnidarians) | an invertebrate animal phylum in which animals possess a single alimentary opening and tentacles with stinging cells |
| coelom | the space between the mesodermal layers that forms the body cavity of some animal phyla |
| coenzyme | an organic cofactor required for enzyme activity |
| colon | the large intestine |
| commensal | describes an organism that lives symbiotically with a host; this host neither benefits nor suffers from the association |
| conditioning | the association of physical, visceral response with an environmental stimulus with which it is not naturally associated; a learned response |
| cone | a cell in the retina that is sensitive to colors and is responsible for color vision |
| consumer | organism that consumes food from outside itself instead of producing it |
| contractile vacuole | a specialized structure that controls osmotic pressure by removing water from the cell |
| cornea | the outer, transparent layer of the eye |
| corpus callosum | a tract of nerve fibers connecting the two cerebral hemispheres |
| corpus luteum | a remnant of follicle after ovulation that secretes the hormone progesterone |
| cortex | in plants, the tissue between the epidermis and the vascular cylinder in the roots and stems of plants; in animals, the outer tissue of some organs |
| cortisone | a hormonal secretion of the adrenal cortex |
| cotyledon | a "seed leaf"; responsible for food digestion and storage in plant embryo |
| cretinism | a thyroid deficiency that results in stunted growth and feeblemindedness |
| crossing over | the exchange of parts of homologous chromosomes during meiosis |
| cross-pollination | the pollination of the pistil of one flower with pollen from the stamen of a different flower of the same species |
| Crustacea | a large class of arthropods, including crabs and lobsters |
| cuticle | a waxy protective layer secreted by the outer surface of plants, insects, etcetera |
| cytochrome | a hydrogen carrier containing iron that functions in many cellular processes, including respiration |
| cytokinesis | a process by which the cytoplasm and the organelles of the cell divide; the final stage of mitosis |
| cyton | the cell body of a neuron |
| cytoplasm | the living matter of a cell, located between the cell membrane and the nucleus |
| cytoskeleton | the organelle that provides mechanical support and carries out motility functions for the cell |
| cytosine | a nitrogen base that is present in nucleotides and nucleic acids; it is paired with guanine |
| deamination | the removal of an amino group from an organism, particularly from an amino acid |
| deletion | the loss of all or part of a chromosome |
| deme | a small, local population |
| dendrite | the part of the neuron that transmits impulses to the cell body |
| deoxyribose | a five carbon sugar that has one oxygen atom less than ribose; a component of DNA |
| diastole | the passive, rhythmical expansion or dilation of the cavities of the heart (atria or ventricles) that allows these organs to fill with blood; preceded and followed by systole (contraction) |
| dicotyledon | a plant that has two seed leaves or cotyledons |
| diencephalon | the hind portion of the forebrain of vertebrates |
| differentation | a progressive change from which a permanently more mature or advanced state results |
| diffusion | the movement of particles from one place to another as a result of their random motion |
| digestion | the process of breaking down large organic molecules into smaller ones |
| dihybrid | an organism that is heterozygous for two different traits |
| dimorphism | the instance of polymorphism in which there is a difference of form between two members of a species, as between males and females |
| diploid | describes cells that have a double set of chromosomes in homologous pairs (2n) |
| disaccharide | a sugar composed of two combined monosaccharides |
| disjunction | the separation of homologous pairs of chromosomes following meiotic synapsis |
| DNA | deoxyribonucleic acid; found in cell nucleus, its basic unit is the nucleotide; contains coded genetic information; can replicate on the basis of heredity |
| dominance | a dominant allele suppresses the expression of the other member of an allele pair when both members are present |
| dorsal root | the sensory branch of each spinal nerve |
| duodenum | the most anterior portion of the small intestine of vertebrates, adjacent to the stomach; the continuation of the stomach into which the bile duct and pancreatic duct empty |
| ecological succession | the orderly process by which one biotic community replaces another until a climax community is established |
| ecology | the study of organisms in relation to their environment |
| ectoderm | the outermost embryonic germ layer that gives rise to the epidermis and the nervous system |
| egg (ovum) | the female gamete; it is nonmotile, large in comparison to male gametes, and stores nutrients |
| electron transport chain | a complex carrier mechanism located on the inside of the inner mitochondrial membrane of the cell; releases energy and is used to form ATP |
| embolus | a blood clot that is formed within a blood vessel |
| emulsion | a colloidal system involving the dispersion of a liquid within a liquid (think bile and fat) |
| endemic | pertaining to a restricted locality; ecologically, occurring only in one particular region |
| endocrine gland | a ductless gland that secretes hormones directly into the bloodstream |
| endocytosis | a process by which the cell membrane is invaginated to form a vesicle which contains extracellular medium |
| endoderm | the innermost embryonic germ layer that gives rise to the lining of the alimentary canal and to the digestive and respiratory organs |
| endoplasmic reticulum | a network of membrane-enclosed spaces connected with the nuclear membrane; transports materials through the cell; can be smooth or rough (ribosomes) |
| enzyme | an organic catalyst and protein |
| endoplasm | the inner portion of the cytoplasm of a cell or the portion that surrounds the nucleus |
| endosperm | the triploid tissue in some seeds that contains stored food and is formed by the union of one sperm nucleus with two nuclei of the female's gametophyte |
| epidermis | the outermost surface of an organism |
| epididymis | the coiled part of the sperm duct, adjacent to the testes in mammals |
| epiglottis | in mammals, a flap of tissue above the glottis; it folds back over the glottis in swallowing to close the air passages of the lungs; contains elastic cartilage |
| epicotyl | the portion of seed plant embryo above the cotyledon |
| epinephrine | adrenaline |
| epithelium | the cellular layer that covers external and internal surfaces |
| epiphyte | a plant that lives on another plant mensalistically |
| erythrocyte | an anucleate red blood cell that contains hemoglobin |
| esophagus | the portion of alimentary canal connecting the pharynx and the stomach |
| estrogen | a female sex hormone secreted by the follicle |
| ethanol fermentation | a form of anaerobic respiration found in yeast and bacteria |
| ethylene | a hormone that ripens fruit and induces aging |
| eukaryote | multicellular organism |
| Eustachian tube | an air duct from the middle ear to the throat that equalizes external and internal air pressure |
| excretion | the elimination of metabolic waster matter |
| exocrine | pertaining to a type of gland that releases its secretion through a duct |
| exocytosis | a process by which the vesicle in the cell fuses with the cell membrane and releases its contents to the outside |
| exoskeleton | describes arthropods and other animals whose skeletal or supporting structures are outside the skin |
| eye | a sensory organ capable of detecting light |
| F1 | the first filial generation (first offspring) |
| F2 | the second filial generation; offspring resulting from the crossing of individuals of the F1 generation |
| fallopian tube | the mammalian oviduct that leads from the ovaries to the uterus |
| feedback mechanism | the process by which a certain function is regulated by the amount of the substance it produces |
| femur | the thigh bone of vertebrates |
| fermentation | anaerobic respiration the yields 2 molecules of ATP, lactic acid, ethyl alcohol and carbon dioxide or some similar compound via the glycolytic pathway |
| fertilization | the fusion of sperm and the egg to produce a zygote |
| fibrin | protein threads that form in the blood during clotting |
| fibrinogen | blood protein that is transformed to fibrin upon clotting |
| fitness | the ability of an organism to contribute its alleles and therefore is phenotypic traits to future generations |
| flagellate | an organism that possesses one or more whiplike appendages called flagella |
| flagellum | a microscopic, whiplike filament that serves as a locomotor structure in flagellate cells |
| follicle | the sac in the ovary in which the egg develops |
| food vacuole | a vacuole in the cytoplasm in which digestion takes place (in protozoans) |
| frame shift mutation | a mutation involving the addition or loss of nucleotides |
| fruit | a mature ovary |
| follicle-stimulating hormone (FSH) | an anterior pituitary hormone that stimulates the follicles in females and the function of the seminiferous tubules in males |
| functional groups | chemical groups attached to carbon skeletons that give compounds their functionality |
| gall bladder | an organ that stores bile |
| gamete | a sex or reproductive cell that must fuse with another of the opposite type to form a zygote |
| gametophyte | the haploid, sexual stage in the life cycle of plants |
| ganglion | a grouping of neuron cell bodies that acts as a coordinating center |
| gastrula | a stage of embryonic development characterized by the differentiation of the cells into the ectoderm and endoderm germ layers and by the formation of the archenteron |
| gene | the portion of a DNA molecule that serves as a unit of heredity; found on the chromosome |
| gene frequency | a decimal fraction that represents the presence of an allele for all members of a population that have a particular gene locus |
| genetic code | a four-letter code made up of the DNA nitrogen bases A, T, G and C; each chromosome is made up of thousands of these bases |
| genetic drift | random evolutionary changes in the genetic makeup of a population |
| genotype | the genetic makeup of an organism without regard to physical appearance |
| genus | in taxonomy, a classification between species and family |
| geographical barrier | any physical feature that prevents the ecological niches of different organisms from overlapping |
| geotropism | any movement or growth of a living organism in response to the force of gravity |
| germ cell | a reproductive cell |
| germ layer | one of the primary tissues of the embryo |
| gibberellin | a hormone that stimulates plant stem elongation |
| gill slit | a perforation leading from the pharynx to the outside environment that is a characteristic of chordates at one stage of their development |
| glomerulus | a network of capillaries in the Bowman's capsules of the kidney |
| glottis | in mammals, the slitlike opening formed by the vocal folds in the larynx |
| glycogen | a starch form in animals; glucose is converted to this in the liver |
| gylcolysis | the anaerobic respiration of carbohydrates |
| goiter | an enlargement of the thyroid gland due to lack of iodine |
| Golgi apparatus | membranous organelles involved in the storage and modification of secretory products (folded) |
| gonads | the reproductive organ that produces sex cells |
| Graffian follicle | the cavity in the mammalian ovary in which the egg ripens |
| granum | the smallest particle that is capable of carrying out photosynthesis; the functional unit of a chloroplast |
| gray matter | a portion of the CNS consisting of cytons (cell bodies), their dendrites and synaptic connections |
| guanine | a purine (nitrogenous base) component of nucleotides and nucleic acids; links with cytosine in DNA |
| guard cell | one of a pair of kidney-shaped cells that surround a stomate and regulate the size of the stomate in a leaf |
| gymnosperm | a plant that belongs to the class of seed plants in which the seeds are not enclosed in an ovary; includes the conifers |
| haploid | describes cells (gametes) that have half the chromosome number typical of the species |
| hemoglobin | a protein compound containing iron that is found in red blood cells |
| hepatic portal system | the veins that carry blood from the digestive organs to the liver |
| herbivore | a plant-eating animal |
| hermaphrodite | an organism that possesses both the male and the female reproductive organs |
| heterotroph | an organism that must get its inorganic and organic raw materials from the environment; a consumer |
| heterozygous | describes an individual that possesses two contrasting alleles for a given trait |
| homeotherm | an animal with a constant body temperature |
| homologous | describes two or more structures that have similar forms, positions and origins despite the differences between their current functions |
| homozygous | describes an individual that has the same gene for the same trait on each homologous chromosome |
| hormone | a chemical messenger that is secreted by one part of the body and carried by the blood to affect another part of the body, usually a muscle or gland |
| host | any organism that is the victim of a parasite |
| humerus | a bone of the upper arm |
| hybrid | an offspring that is heterozygous for one or more gene pairs |
| hydrostatic skeleton | fluid skeleton of annelids |
| hyperthyroidism | an over secretion of thyroid that leads to high metabolism and exopthalmia goiter |
| hypertonic | describes a fluid that has a higher osmotic pressure than another fluid it is compared to |
| hypocoytl | the portion of the embryonic seed plant below the point of attachment of the coytledon; form the root |
| hypothalamus | a section of the posterior forebrain associated with the pituitary gland |
| hypotonic | describes a fluid that has a lower osmotic pressure than a fluid it is compared to |
| ilium | the dorsal part of the hip girdle |
| immunity | a resistance to disease developed through the immune system |
| imprinting | the process by which environmental patterns or objects presented to a developing organism during a "critical period" of its growth is accepted as a permanent element of its behavior |
| incomplete dominance | genetic blending; each allele exerts some influence on the phenotype |
| independent assortment | the law by which genes on different chromosomes are inherited independently of each other |
| ingestion | the intake of food from the environment into the alimentary canal |
| inner ear | a fluid-filled sensory apparatus that aids balance and hearing |
| insulin | a hormone produced by the Islets of Langerhans in the pancreas |
| integument | refers to protective covering |
| interphase | a metabolic stage between mitoses in which genetic material is reproduced |
| interstitial cells | cells which in the female are located between the ovarian follicles and in the male are located between the seminiferous tubules of the testes |
| inversion | occurs when a segment of genetic material on a chromosome becomes reversed |
| iris | the colored part of the eye that is capable of contracting and regulating the size of the pupils |
| irritability | the ability to respond to a stimulus |
| isolation | the separation of some members of a population from the rest of their species; prevents interbreeding and may lead to the development of a new species |
| isomer | one of a group of compounds that is identical in a atomic composition, but different in structure and arrangement |
| isotonic | describes a fluid that has the same osmotic pressure as a fluid it is compared to |
| Krebs cycle | process of aerobic respiration that fully harvests the energy of glucose; also known as the citric acid cycle |
| lactase | the enzyme that acts upon lactose |
| lacteal | a lymph tubule located in the villus that absorbs fatty acids |
| lactid acid fermentation | a type of anaerobic respiration found in fungi, bacteria and human muscle cells |
| larva | a period in the development of animals between the embryo and adult stages; starts at hatching and ends in metamorphasis |
| legume | a flowering plant with simple dry fruit, characterized by nodes on their roots that contain nitrogen-fixing bacteria |
| lens | a structure of the eye that focuses images on the retina by changing its convexity |
| levels of structure | different relationships that are formed in proteins between the original sequence of amino acids and more complex three-dimensional compounds |
| lichen | an association between an algae and a fungus that is symbiotic and mutualistic in nature |
| linkage | occurs when different traits are inherited together more often than they would have been by chance along; it is assumed that these traits are linked on the same chromosome |
| lipase | a fat-digesting hormone |
| lipid | a fat or oil |
| littoral zone | a marine biome; a region on the continental shelf that contains an ocean area with depths of up to 600 ft |
| Loop of Henle | the thin, bent part of the renal tubule that is the site of the counter-current flow and the sodium gradient |
| luteinizing hormone (LH) | secreted by the anterior pituitary gland, this hormone stimulates the conversion of a follicle into the corpus luteum and the secretion of progesterone by the corpus luteum |
| lymph | a body fluid that flows in its own circulatory fluid in lymphatic vessels separate from blood circulation |
| lymph capillary | one of many tubules that absorb tissue fluid and return it to the bloodstream via the lymphatic system |
| lymphocyte | a kind of white blood cell in vertebrates that is characterized by a rounded nucleus; involved in the immune response |
| lysosome | an organelle that contains enzymes that aid in intracellular digestion |
| macula | a sensory hair structure in the utriculus and the sacculus of the inner ear; orients the head with respect to gravity |
| malleus | the outermost bone of the middle ear (hammer) |
| malpighian tubules | tubules that excrete metabolic wastes into the hindgut in arthropods |
| maltase | an enzyme that acts upon maltose and converts it into glucose |
| maltose | a 12-carbon sugar that is formed by the union of two glucose units (a disaccharide) |
| marsupial | a pouched mammal, such as the kangaroo or opossum |
| medulla | the inner layer of an organ surrounded by the cortex |
| medulla oblongata | the posterior part of the brain that controls the rate of breathing and other autonomic functions |
| medusa | a jellyfish |
| meiosis | a process of cell division whereby each daughter cell receives only one set of chromosomes; the formation of gametes |
| Mendelian laws | laws of classical genetics established through Mendel's experiments with peas |
| meninges | three membranes that envelop the brain and spinal cord (pia mater, dura mater and arachnoid) |
| meristem | an undifferentiated, growing region of a plant that is constantly undergoing cell division and differentiation |
| mesoderm | the primary germ layer, developed from the lip of the blastopore, that gives rise to the skeleton, the circulatory system and many organs and tissues between the epidermis and the epithelium |
| metabolism | a group of life-maintaining processes that includes nutrition, respiration (the production of usable energy) and the synthesis and degradation of biochemical substances |
| metamorphosis | the transformation of an immature animal into an adult; a change in the form of an organ or structure |
| metaphase | a stage of mitosis; chromosomes line up at the equator of the cell |
| microbodies | organelles that serve as specialized containers for metabolic reactions |
| micron (micrometer) | one-thousandth of a millimeter; a unit of microscopic length |
| mitochondria | cytoplasmic organelles that serve as sites of respiration; a rod-shaped body in the cytoplasm known to be the center of cellular respiration |
| mitosis | a type of nuclear division that is characterized by complex chromosomal movement and the exact duplication of chromosomes; occurs in somatic cells |
| monocotyledon | a plant that has a single cotyledon or seed-leaf |
| monohybrid | an individual that is heterozygous for only one trait |
| monosaccharide | a simple sugar |
| morphology | the study of form and structure |
| morula | the solid ball of cells the results from cleavage of an egg; a solid blastula that precedes the blastula stage |
| mucosa | a mucus-secreting membrane |
| mutagenic agent | agent that induces mutations; typically carcinogenic |
| mutation | changes in genes that are inherited |
| mutualism | a symbiotic relationship from which both organisms involved derive some benefit |
| myelin sheath | a fatty sheath surrounding the axon of a neuron that aids in stimulus transmission; it is secreted by the Schwann cells |
| NAD | an abbreviation of nicotinamide-adenine-dinucleotide, also called DPN; a respiratory oxidation-reduction molecule |
| NADP | an abbreviation of nicotinamide-adenine-dinucleotide-phosphate, also called TPN; an organic compound that serves as an oxidation-reduction molecule |
| nephron | functional urinary tubules responsible for excretion in the kidney of vertebrates |
| nerve | a bundle of nerve axons |
| nerve cord | a compact linear organization of nerve tissues with ganglia in the CNS |
| nerve net | a multidirectional sensory system of lower animals such as the hydra, consisting of nerve fibers spread throughout the ectoderm |
| neural tube | an embryonic structure that gives rise to the central nervous system |
| neuron | a nerve cell |
| niche | the functional role and position of an organism in an ecosystem; embodies every aspect of the organism's existence |
| nictitating membrane | a thin, transparent, eyelid-like membrane that opens and closes laterally across the cornea of many vertebrates (the third eyelid) |
| nitrogen cycle | the recycling of nitrogen from decaying organism for use in future generations |
| nondisjunction | the failure of some homologous pairs of chromosomes to separate following meiotic synapsis |
| notochord | a flexible, supportive rod running longitudinally through the dorsum ventral to the nerve cord; found in lower chordates and in the embryos of vertebrates |
| nuclear membrane | a membrane that envelopes the nucleus and separates it from the cytoplasm; present in eukaryotes |
| nucleolus | a dark-staining small body within the nucleus; composed of RNA |
| nucleotide | an organic molecule consisting of joined phosphate, 5-carbon sugar (deoxyribose or ribose), and a purine or a pyrimidine (adenine, guanine, uracil, thymine or cytosine) |
| nucleus | an organelle that regulates cell functions and contains the genetic material of the cell |
| olfactory | related to the sense of smell |
| oogenesis | a process of formation of ova |
| organelle | a specialized structure that carries out particular functions for eukaryotic cells |
| osmoregulation | the ways in which organisms regulate their supply of water |
| osmosis | the diffusion of water through a semipermeable membrane, from an area of greater concentration to an area of lesser concentration |
| ovary | the female gonad in animals; the base of the pistil in plants |
| oviduct | a tube connecting the ovaries and the uterus |
| oxidation | the removal of hydrogen or electrons from a compound or addition of oxygen; half of a redox (oxidation or reduction) process |
| pairing (synapsis) | an association of homologous chromosomes during the first meiotic division |
| parasitism | a relationship in which one organism benefits at the expense of another |
| parasympathetic | pertaining to a subdivision of the autonomic nervous system of vertebrates |
| parathyroid | an endocrine gland of vertebrates, usually paired, and located near or within the thyroid that secretes parathormone, which controls the metabolism of calcium |
| parenchyma | plant tissue consisting of large thin-walled cells for storage |
| passive immunity | a resistance to disease produced through the injection of antibodies |
| parthenogenesis | a form of asexual reproduction in which the egg develops in the absence of sperm |
| pathogen | a disease-causing organism |
| pedigree | a family tree depicting the inheritance of a particular genetic trait over several generations |
| pelagic zone | a marine biome typical of the open seas |
| pepsin | a stomach enzyme that partially digests proteins |
| peptide | the kind of bond formed when two amino acid units are jointed end to end |
| peripheral nervous system | comprises somatic and autonomic nervous systems; consists of cranial nerves and spinal nerves |
| peristalsis | waves of contraction and relaxation passing along a tubular structure, such as the digestive tube |
| permeability | degree of penetrability, as in membranes that allow given substances to pass through; the ability to penetrate |
| pH | a symbol that denotes the relative concentration of hydrogen ions in a solution |
| phagocyte | any cell capable of ingesting another cell |
| pharynx | the part of the alimentary canal between the mouth and the esophagus |
| phenotype | the physical appearance or makeup of an individual, as opposed to its genetic makeup |
| pheromone | substance secreted by organisms that influences the behavior of other members of the same species |
| phloem | the vascular tissue of a plant that transports organic materials (photosynthetic products) from the leaves to other parts of the plant |
| photolysis | a process of photosynthesis in which water is split into H+ and OH-; the hydrogen ion is then joined to NADP |
| photoperiodism | a response by an organism to the duration and timing of light and dark conditions |
| photosynthesis | the process by which light energy and chlorophyll are used to manufacture carbohydrates out of carbon dioxide and water; an autotrophic process using light energy |
| phototropism | plant growth stimulated by light (stem: +, towards light; root: -, away from light) |
| phylogeny | the study of the evolutionary descent and interrelations of groups of organisms |
| phylum | a category of taxonomic classification that is ranked above class and under kingdoms |
| physiology | the study of all living processes, activities and functions |
| pineal body | a structure found between the cerebral hemispheres of vertebrates; secretes melatonin |
| pinocytosis | the intake of fluid droplets into a cell |
| pistil | the part of the flower that bears the female gametophyte |
| pith | the central tissue of a stem, used for food storage |
| pituitary | a gland composed of two parts, anterior and posterior, each with its own secretions; called the "master gland" because its hormones stimulate secretions by other glands |
| placenta | a structure formed by the wall of the uterus and the chorion of the embryo; serves as the area in which the embryo obtains nutrition from the parent |
| planaria | the class of free-living flatworms |
| plankton | passively floating or drifting flora and fauna of a body of water; consists mainly of microscopic organisms |
| plasma | the liquid part of blood |
| plasma membrane | the cell membrane |
| plasmodium | a motile, multinucleate mass of protoplasm resulting from fusion of uninuclear amoeboid cells |
| plastid | cytoplasmic bodies within a plant cell that are often pigmented |
| platelet | small, disc-shaped bodies in the blood that play a chief role in coagulation |
| pleural cavity | the cavity between the lungs and the wall of the chest |
| plexus | a network, particularly of nerve or blood vessels |
| point mutation | a mutation in which a single nucleotide base is substituted for another nucleotide base, or an extra nucleotide base is added |
| polar body | nonfunctional haploid cells created during meiosis in females; they have very little cytoplasm-most has gone into the functional egg cell |
| pollen | the microspore of a seed plant |
| pollination | the transfer of pollen to the micropyle or to a receptive surface that is associated with an ovule (such as stigma) |
| polymer | a large molecule that is composed of many similar molecule units |
| polymorphism | the individual differences of form among the members of a species |
| polyp | a typical coelenterate individual with a hollow tubular body whose outer ectoderm is separated from its inner ectoderm by mesoglea |
| polyploidy | a condition in which an organism may have a multiple of the normal number of chromosomes (4n, 6n, etc) |
| polysaccharide | a carbohydrate that is composed of many monosaccharide units joined together |
| pons | the part of the hindbrain located in the brain stem |
| population | all the members of a given species inhabiting a certain locale |
| Porifera | the phylum of sponges |
| primary oocyte | a cell that divides to form the polar body and the secondary oocyte |
| primary spermatocyte | a cell that divides to form two secondary spermatocytes |
| producer | organism that produces its own food; first stage in the food chain |
| progesterone | the hormone secreted by the corpus luteum of vertebrates and the placenta of mammals; its function is to maintain the endometrium |
| prokaryote | unicellular organism with simple cell structure |
| prophase | a mitotic or meiotic stage in which the chromosomes become visible and during which the spindle fibers form; synapsis takes place during the first meiotic prophase |
| protein | one of a class of organic compounds that is composed of many amino acids; contains C, H, O and N |
| prothrombin | a constituent of the plasma of the blood of vertebrates; it is converted to thrombin by thrombokinase in the presence of calcium ions, thus contributing to the clotting of blood |
| Protista | a kingdom of unicellular living organisms that are neither animals nor plants; includes some groups of algae, slime molds and protozoa |
| ptyalin | a digestive enzyme of the saliva that turns starch into maltose (salivary amylase) |
| pulmonary | relating to the lung |
| pupil | an opening in the eye whose size is regulated by the iris |
| purine | a nitrogenous base such as adenine or guanine; when joined with sugar or phosphate, a component of nucleotides and nucleic acids |
| pyrimidine | a nitrogen base such as cytosine, thymine and uracil; when joined with sugar or phosphate, a component of nucleotides and nucleic acids |
| pyloric valve | a muscular valve regulating the flow of food from the stomach to the small intestine |
| recessive | pertains to a gene or characteristic that is masked when a dominant allele is present |
| recombinant DNA technology | technology that allows for manipulation of genetic material |
| reduction | a change from a diploid nucleus to a haploid nucleus, as in meiosis |
| regeneration | the ability of certain animals to regrow missing body parts |
| respiration | a chemical action that releases energy from glucose to form ATP |
| respiratory center | the area of medulla that regulates the rate of breathing |
| reticulum | a network or mesh of fibrils, fibers or filaments |
| retina | the innermost tissue layer of the eyeball that contains light-sensitive receptor cells |
| Rh factor | an antigen in blood; can cause erythroblastosis fetalis when the mother is Rh- and the fetus is Rh+ |
| rhizome | an underground stem |
| ribosome | an organelle in the cytoplasm that contains RNA; serves as the site of protein synthesis |
| rhodopsin | the pigment in rod cells that causes light sensitivity |
| rickettsia | a kind of microorganism that is between a virus and a bacterium; parasitic within the cells of insects and ticks |
| RNA | an abbreviation of ribonucleic acid, a nucleic acid in which the sugar is ribose; a product of DNA transcription that serves to control certain cell activities |
| rod | a cell in the retina that is sensitive to weak light |
| root hair | outgrowths of a root's epidermal cells that allow for greater surface area for absorption of nutrients and water |
| saprophyte | an organism that obtains its nutrients from dead organisms |
| secondary tissue | tissue formed by the differentiation of cambium that causes a growth in width of a plant system |
| selective breeding | the creation of certain strains of specific traits through control of breeding |
| self-pollination | the transfer of pollen from the stamen to the pistil of the same flower |
| semicircular canals | fluid-filled structures in the inner ear that are associated with the sense of balance |
| seminal fluid | semen |
| seminiferous tubules | structures in the testes that produce sperm and semen |
| sensory neuron | a neuron that picks up impulses from receptors and transmits them to the spinal cord |
| sere | a series of ecological communities formed in ecological succession |
| serum | the fluid that remains after fibrinogen is removed from the blood plasma of vertebrates |
| sex chromosome | there are two kinds of sex chromosomes, X and Y; XX signifies a female and XY signifies a male |
| sex linkage | occurs when certain traits are determined by genes on sex chromosomes |
| sinus | a space in the body (e.g. blood sinus or maxillary sinus) |
| small intestine | the site of most digestion of nutrients and absorption of digested nutrients |
| smooth muscle | involuntary muscle |
| somatic cell | any cell that is not a reproductive cell |
| species | a group of populations that can interbreed |
| spermatogenesis | the process of forming the sperm cells from primary spermatocytes |
| spindle | a structure that arises during mitosis and helps separate the chromosomes; composed of tubulin |
| spiracle | the external opening of the trachea in insects |
| sphincter | a ring-shaped muscle that is capable of closing a tubular opening by constriction |
| spore | a reproductive cell that is capable of developing directly into an adult |
| sporophyte | an organism that produces spores; a phase in the diploid-haploid life cycle that alternates with a gametophyte phase |
| stamen | the part of the flower that produces pollen |
| steroid | one of a class of organic compounds that contains a molecular skeleton of four fused rings of carbon |
| stigma | the uppermost portion of pistil upon which pollen grains alight |
| stoma (stomate) | a microscopic opening located in the epidermis of a leaf and formed by a pair of guard cells |
| stomach | the portion of alimentary canal in which some protein digestion occurs |
| stroma | a dense fluid within the chloroplast in which CO2 is converted into sugars in photosynthesis |
| style | a stalklike or elongated body part, usually pointed at one end |
| substrate | a substance that is acted upon by an enzyme |
| sucrase | an enzyme that acts upon sucrose |
| symbiosis | the living together of two organisms in an intimate relationship |
| sympathetic | pertaining to a subdivision of the autonomic nervous system |
| synapse | the junction or gap between the axon terminal of one neuron and the dendrites of another neuron |
| synergistic | describes organisms that are cooperative in action, such as hormones or other growth factors that reinforce each other's activity |
| synaptic terminal | the swelling at the end of an axon |
| synapsis | the pairing of homologous chromosomes during meiosis |
| systole | the contraction of the atria or ventricles of the heart |
| test cross | the breeding of an organism with a homozygous recessive in order to determine whether an organism is homozygous dominant or heterozygous dominant for a given trait |
| taiga | a terrestrial habitat zone that is characterized by large tracts of coniferous forests, long and cold winters, and short summers |
| taxonomy | the science of classification of living things |
| telophase | a mitotic stage in which nuclei reform and nuclear membrane reappears |
| testes | the male gonads that produce sperm and male hormones |
| tetrad | a pair of chromosome pairs present during the first metaphase of meiosis |
| thalamus | a lateral region of the forebrain |
| thermoregulation | the ways in which organisms regulate their internal heat |
| thoracic duct | a major lymphatic that empties lymph into a vein in the neck |
| thorax | the part of the body of an animal that is between the neck or head and the abdomen |
| thrombin | a substance that participates in the clotting of blood in vertebrates |
| thrombokinase | the enzyme released from the blood platelets in vertebrates during clotting |
| thymine | a pyrimidine component of nucleic acids and nucleotides; pairs with adenine in DNA |
| thymus | a ductless gland in upper chest region concerned with immunity and the maturation of lymphocytes |
| thyroid | an endocrine gland located in the neck that produces thyroxin |
| thryoxin | a hormone of the thyroid that regulates basal metabolism |
| tissue | a mass of cells that have similar structures and perform similar functions |
| trachea | an air-conducting tube |
| transcription | the fist stage of protein synthesis, in which the information coded in the DNA base is transcribed onto a strand of mRNA |
| translation | the final stages of protein synthesis in which the genetic code of nucleotide sequences is translated into a sequences of amino acids |
| translocation | the transfer of a piece of chromosome to another chromosome |
| transpiration | the evaporation of water from leaves or other exposed surfaces of plants |
| trilobite | a marine arthropod, now extinct, that lived during the Paleozoic era |
| trypsin | an enzyme from the pancreas that digests proteins in the small intestine |
| tundra | the biome located between the polar region and the tiaga |
| turgor pressure | the pressure exerted by the contents of a cell against the cell membrane or cell wall |
| umbilicus | the navel |
| ungulate | a hoofed animal |
| uracil | a pyrimidine found in RNA (but not DNA); pairs with DNA adenine |
| urea | an excretory product of protein metabolism |
| ureter | a duct that carries urine from the kidneys to the bladder |
| urethra | a duct through which the urine passes from the bladder to the outside |
| urinary bladder | an organ that stores urine temporarily before it is excreted |
| urine | fluid excreted by the kidney containing urea, water, salts, etc |
| uterus | the womb in which the fetus develops |
| vacuole | a space in the cytoplasm of a cell that contains fluid |
| vagus nerve | the tenth cranial nerve that innervates digestive organs, heart and other areas |
| vein | a blood vessel that carries blood back to the heart from the capillaries |
| ventral root | the basal branch of each spinal nerve; carries motor neurons |
| ventricle | the more muscular chamber(s) of the heart that pump blood to the lungs and to the rest of the body |
| vestigial organ | an organ that is not functional in an organism, but was functional at some period in its evolution |
| villus | a small projection in the walls of the small intestine that increases the surface area available for absorption |
| vitamin | an organic nutrient required by organisms in small amounts to aid in proper metabolic processes |
| white matter | an accumulation of axons within the CNS that is white because it is fatty, myelin sheath |
| wood | xylem that is no longer being used |
| xylem | vascular tissue of the plant that aids in support and carries water |
| yolk sac | a specialized structure that leads to the digestive tract of a developing organism and provides it with food during early development |
| zygote | a cell resulting from the fusion of gametes |
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