Biology Sat Subject Test Vocabulary Flashcards
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
adrenal cortex
the ourter 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 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
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
pseudopod
movement of 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)
Anaphase I
the stage in meiosis during which homologus pairs migrate
AnaphaseII
the stage in meiosis during which chromatids migrate to different ends of the cell
androgen
a mall 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
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
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
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
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 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
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
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
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
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 soft or rough
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
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
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
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
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
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
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
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
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
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
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
