A daily decrease in metabolic activity and
corresponding body temperature during
times of inactivity for some small mammals
daily torpor and birds. The physiological changes during
resting periods enable these organisms to
survive on energy stores in their tissues.
A measure of mass for atoms and subatomic
The contribution an individual makes to the
Darwinian fitness gene pool of the next generation, relative to
the contributions of other individuals.
Either of the two cells that result when a cell
daughter cells divides.
A plant whose flowering is not affected by
day-neutral plant photoperiod.
A relatively large group of crustaceans that
decapods includes lobsters, crayfish, crabs, and
Any of the saprotrophic fungi and bacteria
that absorb nutrients from nonliving organic
decomposers material such as corpses, fallen plant
material, and the wastes of living organisms,
and convert them into inorganic forms.
The breakdown of organic materials into
decomposition inorganic ones.
An international initiative focusing on the
deepest phylogenetic branching within the
deep green plant kingdom to identify and name the major
A dark, hot, oxygen-deficient environment
deep-sea hydrothermal associated with volcanic activity. The food
producers are chemoautotrophic
A chemical reaction in which two molecules
dehydration reaction covalently bond to each other with the
removal of a water molecule.
(1) A deficiency in a chromosome resulting
from the loss of a fragment through
deletion breakage. (2) A mutational loss of one or
more nucleotide pairs from a gene.
A shift from zero population growth in which
birth rates and death rates are high to zero
demographic transition population growth characterized instead by
low birth and death rates.
The study of statistics relating to births and
demography deaths in populations.
For proteins, a process in which a protein
unravels and loses its native conformation,
thereby becoming biologically inactive. For
denaturation DNA, the separation of the two strands of the
double helix. Denaturation occurs under
extreme conditions of pH, salt concentration,
One of usually numerous, short, highly
branched processes of a neuron that
dendrite conveys nerve impulses toward the cell
The number of individuals per unit area or
Any characteristic that varies according to an
density dependent increase in population density.
density-dependent Any factor that has a greater impact on a
population as the population density
density-dependent The phenomenon observed in normal animal
cells that causes them to stop dividing when
inhibition they come into contact with one another.
density-independent Any factor that affects a population by the
same percentage, regardless of density.
A double-stranded, helical nucleic acid
deoxyribonucleic acid molecule capable of replicating and
determining the inherited structure of a cell's
The sugar component of DNA, having one
deoxyribose less hydroxyl group than ribose, the sugar
component of RNA.
An electrical state in an excitable cell
whereby the inside of the cell is made less
negative relative to the outside than at the
resting membrane potential. A neuron
depolarization membrane is depolarized if a stimulus
decreases its voltage from the resting
potential of 270 mV in the direction of zero
The condition of a membrane that is more
depolarized negatively charged on one side than on the
A heterotroph, such as an earthworm, that
deposit-feeder eats its way through detritus, salvaging bits
and pieces of decaying organic matter.
The protective covering of plants; generally a
single layer of tightly packed epidermal cells
dermal tissue system covering young plant organs formed by
descent with Darwin's initial phrase for the general
process of evolution.
A type of intercellular junction in animal cells
desmosome that functions as an anchor.
A type of embryonic development in
protostomes that rigidly casts the
determinate cleavage developmental fate of each embryonic cell
A type of growth characteristic of animals, in
determinate growth which the organism stops growing after it
reaches a certain size.
The progressive restriction of developmental
potential, causing the possible fate of each
determination cell to become more limited as the embryo
A consumer that derives its energy from
detritivore nonliving organic material.
detritus Dead organic matter.
One of two distinct evolutionary lines of
coelomates, consisting of the echinoderms
and chordates and characterized by radial,
deuterostomes indeterminate cleavage, enterocoelous
formation of the coelom, and development of
the anus from the blastopore.
The sum of all of the changes that
development progressively elaborate an organism's body.
A second messenger produced by the
diacylglycerol (DAG) cleavage of a certain kind of phospholipid in
the plasma membrane.
(1) A sheet of muscle that forms the bottom
wall of the thoracic cavity in mammals; active
in ventilating the lungs. (2) A dome-shaped
diaphragm rubber cup fitted into the upper portion of the
vagina before sexual intercourse. It serves
as a physical barrier to block the passage of
One of three groups of amniotes based on
diapsids key differences between their skulls.
The stage of the heart cycle in which the
diastole heart muscle is relaxed, allowing the
chambers to fill with blood.
Blood pressure that remains between heart
diastolic pressure contractions.
The stage of the heart cycle in which the
diatom heart muscle is relaxed, allowing the
chambers to fill with blood.
A subdivision of flowering plants whose
dicot members possess two embryonic seed
leaves, or cotyledons.
differentiation See cellular differentiation.
The spontaneous tendency of a substance to
move down its concentration gradient from a
diffusion more concentrated to a less concentrated
The process of breaking down food into
digestion molecules small enough for the body to
An organism that is heterozygous with
respect to two genes of interest. A dihybrid
results from a cross between parents doubly
dihybrid homozygous for different alleles. For
example, parents of genotype AABB and
aabb produce a dihybrid of genotype AaBb.
A mycelium of certain septate fungi that
dikaryon possesses two separate haploid nuclei per
A mycelium with two haploid nuclei per cell,
dikaryotic one from each parent.
A unicellular photosynthetic alga with two
dinoflagellate flagella situated perpendicular grooves in
cellulose plates covering the cell.
An extremely diverse group of ancient
dinosaurs reptiles varying in body shape, size, and
Referring to a plant species that has
diocious staminate and carpellate flowers on separate
An enzyme found attached to the intestinal
dipeptidase lining. It splits small peptides.
diploblastic Having two germ layers.
A cell containing two sets of chromosomes
diploid cell (2n), one set inherited from each parent.
Diplopoda The animal class that includes millipedes.
Dipnoi The class of lungfishes.
Natural selection that favors individuals at
directional selection one end of the phenotypic range.
A double sugar, consisting of two
disaccharide monosaccharides joined by dehydration
The distribution of individuals within
dispersal geographic population boundaries.
The pattern of spacing among individuals
dispersion within geographic population boundaries.
A chart showing the relative amounts of
oxygen bound to hemoglobin when the
dissociation curve pigment is exposed to solutions varying in
their partial pressure of dissolved oxygen.
In the vertebrate kidney, the portion of a
distal tubule nephron that helps refine filtrate and empties
it into a collecting duct.
A force that changes a biological community
and usually removes organisms from it.
disturbance Disturbances, such as fire and storms, play
pivotal roles in structuring many biological
Strong covalent bonds formed when the
disulfide bridge sulfur of one cysteine monomer bonds to the
sulfur of another cysteine monomer.
Natural selection that favors extreme over
diversifying selection intermediate phenotypes.
diversity Variety in organisms.
An individual's unique collection of DNA
DNA fingerprint restriction fragments, detected by
electrophoresis and nucleic acid probes.
A linking enzyme essential for DNA
replication; catalyzes the covalent bonding of
DNA ligase the 39 end of a new DNA fragment to the 59
end of a growing chain.
The addition of methyl groups (—CH3) to
bases of DNA after DNA synthesis; may
DNA methylation serve as a long-term control of gene
A method to detect and measure the
expression of thousands of genes at one
time. Tiny amounts of a large number of
single-stranded DNA fragments representing
DNA microarray assays different genes are fixed to a glass slide.
These fragments, ideally representing all the
genes of an organism, are tested for
hybridization with various samples of cDNA
An enzyme that catalyzes the elongation of
DNA polymerase new DNA at a replication fork by the addition
of nucleotides to the existing chain.
A chemically synthesized, radioactively
labeled segment of nucleic acid used to find
DNA probe a gene of interest by hydrogen-bonding to a
A part of the three-dimensional structure of a
DNA-binding domain transcription factor that binds to DNA.
A taxonomic category above the kingdom
domain level. The three domains are Archaea,
Bacteria, and Eukarya.
A linear quot;pecking orderquot; of animals, where
dominance hierarchy position dictates characteristic social
In a heterozygote, the allele that is fully
dominant allele expressed in the phenotype.
The phenotype that results from having at
dominant phenotype least one dominant allele.
Those species in a community that have the
highest abundance or highest biomass.
dominant species These species exert a powerful control over
the occurrence and distribution of other
A biogenic amine closely related to
dopamine epinephrine and norepinephrine.
A condition typified by extremely low
dormancy metabolic rate and a suspension of growth
Pertaining to the back of a bilaterally
dorsal symmetrical animal.
dorsal lip The dorsal side of the blastopore.
A circulation scheme with separate
double circulation pulmonary and systemic circuits, which
ensures vigorous blood flow to all organs.
A type of covalent bond in which two atoms
double covalent bond share two pairs of electrons; symbolized by a
pair of lines between the bonded atoms.
A mechanism of fertilization in angiosperms,
in which two sperm cells unite with two cells
double fertilization in the embryo sac to form the zygote and
The form of native DNA, referring to its two
double helix adjacent polynucleotide strands wound into a
A human genetic disease resulting from
having an extra chromosome 21,
Down syndrome characterized by mental retardation and
heart and respiratory defects.
Members of the group Oomycota, they are
heterotrophic stramenopiles that lack
downy mildews chloroplasts, typically have cell walls made
of cellulose, and generally live on land as
parasites of plants.
Drosophila Fruit fly.
A human genetic disease caused by a sex-
Duchenne muscular linked recessive allele; characterized by
progressive weakening and a loss of muscle
The first section of the small intestine, where
acid chyme from the stomach mixes with
duodenum digestive juices from the pancreas, liver,
gallbladder, and gland cells of the intestinal
An aberration in chromosome structure
resulting from an error in meiosis or
duplication mutagens; duplication of a portion of a
chromosome resulting from fusion with a
fragment from a homologous chromosome.
A large contractile protein forming the side-
dynein arms of microtubule doublets in cilia and
One of three binding sites for tRNA during
translation, it is the place where discharged
E site tRNAs leave the ribosome; E stands for exit
A steroid hormone that triggers molting in
One of two distinct clades within the
ecdysozoa protostomes. It includes the arthropods.
Sessile or slow-moving animals that include
echinoderms sea stars, sea urchins, brittle stars, crinoids,
and basket stars.
The ratio of net productivity at one trophic
ecological efficiency level to net productivity at the next lower
A method to use multiple constraints to
estimate the human carrying capacity of
Earth by calculating the aggregate land and
ecological footprint water area in various ecosystem categories
that is appropriated by a nation to produce
all the resources it consumes and to absorb
all the waste it generates.
(nich) The sum total of a species' use of the
ecological niche biotic and abiotic resources of its
ecological species The idea that ecological roles (niches) define
Transition in the species composition of a
biological community, often following
ecological succession ecological disturbance of the community; the
establishment of a biological community in
an area virtually barren of life.
The study of how organisms interact with
ecology their environments.
All the organisms in a given area as well as
ecosystem the abiotic factors with which they interact; a
community and its physical environment.
The study of energy flow and the cycling of
ecosystem ecology chemicals among the various biotic and
abiotic factors in an ecosystem.
The outermost of the three primary germ
layers in animal embryos; gives rise to the
ectoderm outer covering and, in some phyla, the
nervous system, inner ear, and lens of the
A type of mycorrhizae in which the mycelium
forms a dense sheath, or mantle, over the
surface of the root. Hyphae extend from the
ectomycorrhizae mantle into the soil, greatly increasing the
surface area for water and mineral
Parasites that feed on the external surface of
ectoparasites a host.
An animal, such as a reptile, fish, or
amphibian, that must use environmental
ectotherm energy and behavioral adaptations to
regulate its body temperature.
Organisms that do not produce enough
ectothermic metabolic heat to have much effect on body
ediacaran period The last period of the Precambrian era.
A muscle cell or gland cell that performs the
body's responses to stimuli; responds to
effector cell signals from the brain or other processing
center of the nervous system.
efferent arteriole The blood vessel draining a nephron.
Another name for maternal effect genes,
egg-polarity genes these genes control the orientation (polarity)
of the egg.
The short section of the ejaculatory route in
mammals formed by the convergence of the
ejaculatory duct vas deferens and a duct from the seminal
vesicle. The ejaculatory duct transports
sperm from the vas deferens to the urethra.
Long threads made of the protein elastin.
Elastic fibers provide a rubbery quality to the
elastic fibers extracellular matrix that complements the
nonelastic strength of collagenous fibers.
electrocardiogram (ECG A record of the electrical impulses that travel
through cardiac muscle during the heart
or EKG) cycle.
The diffusion gradient of an ion, representing
electrochemical a type of potential energy that accounts for
both the concentration difference of the ion
gradient across a membrane and its tendency to
move relative to the membrane potential.
electroencephalogram A medical test that measures different
patterns in the electrical activity of the brain.
An ion transport protein generating voltage
electrogenic pump across the membrane.
electromagnetic Receptors of electromagnetic energy, such
as visible light, electricity, and magnetism.
electromagnetic The entire spectrum of radiation ranging in
wavelength from less than a nanometer to
spectrum more than a kilometer.
A subatomic particle with a single negative
electron charge; one or more electrons move around
the nucleus of an atom.
A microscope that focuses an electron beam
through a specimen, resulting in resolving
power a thousandfold greater than that of a
light microscope. A transmission electron
electron microscope microscope (TEM) is used to study the
internal structure of thin sections of cells. A
scanning electron microscope (SEM) is used
to study the fine details of cell surfaces.
An energy level representing the distance of
electron shell an electron from the nucleus of an atom.
A sequence of electron carrier molecules
(membrane proteins) that shuttle electrons
electron transport chain during the redox reactions that release
energy used to make ATP.
The attraction of an atom for the electrons of
electronegativity a covalent bond.
A technique to introduce recombinant DNA
into cells by applying a brief electrical pulse
electroporation to a solution containing cells. The electricity
creates temporary holes in the cells' plasma
membranes, through which DNA can enter.
Any substance that cannot be broken down
element to any other substance.
The passing of undigested material out of
elimination the digestive compartment.
embryo New developing individuals.
The female gametophyte of angiosperms,
formed from the growth and division of the
embryo sac megaspore into a multicellular structure with
eight haploid nuclei.
Mutations with phenotypes leading to death
embryonic lethal at the embryo or larval stage.
Another name for land plants, recognizing
embryophyte that land plants share the common derived
trait of multicellular, dependent embryos.
The process that keeps tiny fat droplets from
Molecules that are mirror images of each
A species that is in danger of extinction
endangered species throughout all or a significant portion of its
Species that are confined to a specific,
endemic species relatively small geographic area.
A nonspontaneous chemical reaction in
endergonic reaction which free energy is absorbed from the
A ductless gland that secretes hormones
endocrine gland directly into the bloodstream.
The internal system of chemical
communication involving hormones, the
ductless glands that secrete hormones, and
the molecular receptors on or in target cells
endocrine system that respond to hormones; functions in
concert with the nervous system to effect
internal regulation and maintain
The cellular uptake of macromolecules and
particulate substances by localized regions
endocytosis of the plasma membrane that surround the
substance and pinch off to form an
The innermost of the three primary germ
layers in animal embryos; lines the
endoderm archenteron and gives rise to the liver,
pancreas, lungs, and the lining of the
The innermost layer of the cortex in plant
endodermis roots; a cylinder one cell thick that forms the
boundary between the cortex and the stele.
The collection of membranes inside and
around a eukaryotic cell, related either
endomembrane system through direct physical contact or by the
transfer of membranous vesicles.
The inner lining of the uterus, which is richly
endometrium supplied with blood vessels.
A type of mycorrhizae that, unlike
ectomycorrhizae, do not have a dense
endomycorrhizae mantle ensheathing the root. Instead,
microscopic fungal hyphae extend from the
root into the soil.
endoparasites Parasites that live within a host.
An extensive membranous network in
eukaryotic cells, continuous with the outer
endoplasmic reticulum nuclear membrane and composed of
ribosome-studded (rough) and ribosome-free
A hormone produced in the brain and
endorphin anterior pituitary that inhibits pain perception.
A hard skeleton buried within the soft tissues
of an animal, such as the spicules of
endoskeleton sponges, the plates of echinoderms, and the
bony skeletons of vertebrates.
A nutrient-rich tissue formed by the union of
a sperm cell with two polar nuclei during
endosperm double fertilization, which provides
nourishment to the developing embryo in
A thick-coated, resistant cell produced within
endospore a bacterial cell exposed to harsh conditions.
A hypothesis about the origin of the
eukaryotic cell, maintaining that the
endosymbiotic theory forerunners of eukaryotic cells were
symbiotic associations of prokaryotic cells
living inside larger prokaryotes.
The innermost, simple squamous layer of
endothelium cells lining the blood vessels; the only
constituent structure of capillaries.
An animal that uses metabolic energy to
endotherm maintain a constant body temperature, such
as a bird or mammal.
Organisms with bodies that are warmed by
heat generated by metabolism. This heat is
endothermic usually used to maintain a relatively stable
body temperature higher than that of the
A component of the outer membranes of
endotoxin certain gram-negative bacteria responsible
for generalized symptoms of fever and ache.
The concept that the length of a food chain is
energetic hypothesis limited by the inefficiency of energy transfer
along the chain.
The capacity to do work (to move matter
energy against an opposing force).
In cellular metabolism, the use of energy
energy coupling released from an exergonic reaction to drive
an endergonic reaction.
The different states of potential energy for
energy level electrons in an atom.
A DNA sequence that recognizes certain
enhancer transcription factors that can stimulate
transcription of nearby genes.
The type of development found in
deuterostomes. The coelomic cavities form
enterocoelous when mesoderm buds from the wall of the
archenteron and hollows out.
A category of hormones secreted by the wall
enterogastrones of the duodenum.
An intestinal enzyme that directly or
eneteropeptidase indirectly triggers activation of other
enzymes within the intestinal lumen.
entomology The study of insects.
A quantitative measure of disorder or
entropy randomness, symbolized by S.
An ecological term for the effect of spatial
environmental gain variation, or patchiness, relative to the size
and behavior of an organism.
A protein serving as a catalyst, a chemical
enzyme agent that changes the rate of a reaction
without being consumed by the reaction.
The embryonic axis above the point at which
epicotyl the cotyledons are attached.
(1) The dermal tissue system in plants. (2)
epidermis The outer covering of animals.
A coiled tubule located adjacent to the testes
epididymis where sperm are stored.
The progressive development of form in an
A cartilaginous flap that blocks the top of the
windpipe, the glottis, during swallowing,
epiglottis which prevents the entry of food or fluid into
the respiratory system.
A hormone produced as a response to
epinephrine stress; also called adrenaline.
A plant that nourishes itself but grows on the
epiphyte surface of another plant for support, usually
on the branches or trunks of tropical trees.
A genetic element that can exist either as a
episome plasmid or as part of the bacterial
A genetic element that can exist either as a
epistasis plasmid or as part of the bacterial
A brain region, derived from the
diencephalon, that contains several clusters
epithalamus of capillaries that produce cerebrospinal
Sheets of tightly packed cells that line
epithelial tissue organs and body cavities.
A localized region on the surface of an
epitopse antigen that is chemically recognized by
antibodies; also called antigenic determinant.
A red blood cell; contains hemoglobin, which
erythrocyte functions in transporting oxygen in the
A hormone produced in the kidney when
tissues of the body do not receive enough
erythropoietin oxygen. This hormone stimulates the
production of erythrocytes.
A channel that conducts food, by peristalsis,
esophagus from the pharynx to the stomach.
The amino acids that an animal cannot
synthesize itself and must obtain from food.
essential amino acids Eight amino acids are essential in the human
Certain unsaturated fatty acids that animals
essential fatty acids cannot make.
A chemical element that is required for a
plant to grow from a seed and complete the
essential nutrient life cycle, producing another generation of
A physiological state characterized by slow
metabolism and inactivity, which permits
estivation survival during long periods of elevated
temperature and diminished water supplies.
The primary female steroid sex hormones,
which are produced in the ovary by the
developing follicle during the first half of the
cycle and in smaller quantities by the corpus
estrogens luteum during the second half. Estrogens
stimulate the development and maintenance
of the female reproductive system and
secondary sex characteristics.
A type of reproductive cycle in all female
mammals except higher primates, in which
estrous cycle the nonpregnant endometrium is reabsorbed
rather than shed, and sexual response
occurs only during midcycle at estrus.
A period of sexual activity associated with
The area where a freshwater stream or river
estuary merges with the ocean.
The study of animal behavior in natural
The only gaseous plant hormone,
ethylene responsible for fruit ripening, growth
inhibition, leaf abscission, and aging.
The more open, unraveled form of eukaryotic
euchromatin chromatin that is available for transcription.
A large subgroup of traditionally dicot
eudicots angiosperms including roses, peas,
buttercups, sunflowers, oaks, and maples.
A group of protistans, including Euglena and
its relatives, characterized by an anterior
euglenoid pocket or chamber from which one or two
A type of cell with a membrane-enclosed
nucleus and membrane-enclosed organelles,
eukaryotic cell present in protists, plants, fungi, and
animals; also called eukaryote.
Members of the subkingdom that includes all
eumetazoa animals except sponges.
Organisms that can tolerate substantial
euryhaline changes in external osmolarity.
Mainly marine and freshwater, extinct,
eurypterids chelicerates. These predators, also called
water scorpions, ranged up to 3 meters long.
The tube that connects the middle ear to the
Eustachian tube pharynx.
Placental mammals; those whose young
complete their embryonic development
eutherian mammals within the uterus, joined to the mother by the
Pertaining to a highly productive lake, having
eutrophic a high rate of biological productivity
supported by a high rate of nutrient cycling.
The removal of heat energy from the surface
evaporation of a liquid that is losing some of its
The property of a liquid whereby the surface
becomes cooler during evaporation, owing to
evaporative cooling a loss of highly kinetic molecules to the
All the changes that have transformed life on
evolution Earth from its earliest beginnings to the
diversity that characterizes it today.
evolutionary species The idea that evolutionary lineages and
ecological roles can form the basis of
concept species identification.
A structure that evolves and functions in one
environmental context but that can perform
exaptation additional functions when placed in some
Cells that have the ability to generate
excitable cells changes in their membrane potentials.
An electrical change (depolarization) in the
membrane of a postsynaptic neuron caused
excitatory postsynaptic by the binding of an excitatory
neurotransmitter from a presynaptic cell to a
potential (EPSP) postsynaptic receptor; makes it more likely
for a postsynaptic neuron to generate an
The disposal of nitrogen-containing waste
excretion products of metabolism.
A spontaneous chemical reaction in which
exergonic reaction there is a net release of free energy.
The cellular secretion of macromolecules by
exocytosis the fusion of vesicles with the plasma
Powerful hydrolytic enzymes secreted by a
exoenzymes fungus outside its body to digest food.
A coding region of a eukaryotic gene. Exons,
exon which are expressed, are separated from
each other by introns.
A hard encasement on the surface of an
animal, such as the shells of mollusks or the
exoskeleton cuticles of arthropods, that provides
protection and points of attachment for
A toxic protein secreted by a bacterial cell
exotoxin that produces specific symptoms even in the
absence of the bacterium.
exponential population The geometric increase of a population as it
grows in an ideal, unlimited environment.
A cloning vector that contains the requisite
prokaryotic promoter just upstream of a
expression vector restriction site where a eukaryotic gene can
The fusion of gametes that parents have
external fertilization discharged into the environment.
Sensory receptors that detect stimuli outside
exteroreceptor the body, such as heat, light, pressure, and
extracellular digestion The breakdown of food outside cells.
extracellular matrix The substance in which animal tissue cells
are embedded consisting of protein and
extraembryonic Four membranes (yolk sac, amnion, chorion,
allantois) that support the developing embryo
membranes in reptiles, birds, and mammals.
Microorganisms that live in unusually highly
extreme halophiles saline environments such as the Great Salt
Lake or the Dead Sea.
Microorganisms that thrive in hot
extremeophile environments (often 60–80 degrees C).
Microorganisms that live in extreme
environments. They are further classified as
5’ cap either methanogens, extreme halophiles, or
A fertility factor in bacteria, a DNA segment
that confers the ability to form pili for
conjugation and associated functions
F factor required for the transfer of DNA from donor
to recipient. It may exist as a plasmid or
integrated into the bacterial chromosome.
The first filial, or hybrid, offspring in a genetic
F1 generation cross-fertilization.
The F factor and its plasmid that consists of
F1 plasmid about 25 genes, most of which are required
for the production of sex pili.
Offspring resulting from interbreeding of the
F2 generation hybrid F1 generation.
The positive effect of early species on the
facilitate appearance of later species in ecological
The spontaneous passage of molecules and
ions, bound to specific carrier proteins,
facilitated diffusion across a biological membrane down their
An organism that makes ATP by aerobic
respiration if oxygen is present but that
facultative anaerobe switches to fermentation under anaerobic
In classification, the taxonomic category
family above genus.
The depolarization of the egg membrane
fast block to within 1–3 seconds after sperm binding to
the vitelline layer. The reaction prevents
polyspermy additional sperm from fusing with the egg's
Muscle cells used for rapid, powerful
fast muscle fibers contractions.
A biological compound consisting of three
fat (tracylglycerol) fatty acids linked to one glycerol molecule.
Territorial diagrams of embryonic
fate maps development that reveal the future
development of individual cells and tissues.
A long carbon chain carboxylic acid. Fatty
acids vary in length and in the number and
fatty acid location of double bonds; three fatty acids
linked to a glycerol molecule form fat.
Light epidermal outgrowths that form the
feathers external covering of the body of birds.
feces The wastes of the digestive tract.
A method of metabolic control in which the
end product of a metabolic pathway acts as
feedback inhibition an inhibitor of an enzyme within that
A catabolic process that makes a limited
amount of ATP from glucose without an
fermentation electron transport chain and that produces a
characteristic end product, such as ethyl
alcohol or lactic acid.
The union of haploid gametes to produce a
fertilization diploid zygote.
The swelling of the vitelline layer away from
fertilization envelope the plasma membrane.
A developing human from the ninth week of
fetus gestation until birth; has all the major
structures of an atult.
A lignified cell type that reinforces the xylem
of angiosperms and functions in mechanical
fiber support; a slender, tapered sclerenchyma
cell that usually occurs in bundles.
The activated form of the blood-clotting
fibrin protein fibrinogen, which aggregates into
threads that form the fabric of the clot.
The inactive form of the plasma protein that
is converted to the active form fibrin, which
fibrinogen aggregates into threads that form the
framework of a blood clot.
A type of cell in loose connective tissue that
fibroblast secretes the protein ingredients of the
A glycoprotein that helps cells attach to the
fibronectin extracellular matrix.
A dense tissue with large numbers of
fibrous connective collagenous fibers organized into parallel
bundles. This is the dominant tissue in
tissue tendons and ligaments.
Root systems common to monocots
fibrous root systems consisting of a mat of thin roots that spread
out below the soil surface.
filament The stalk of a stamen.
Fluid extracted by the excretory system from
the blood or body cavity. The excretory
filtrate system produces urine from the filtrate after
extracting valuable solutes from it and
In the vertebrate kidney, the extraction of
filtration water and small solutes, including metabolic
wastes, from the blood by the nephrons.
first law of The principle of conservation of energy.
Energy can be transferred and transformed,
thermodynamics but it cannot be created or destroyed.
fixed action pattern A sequence of behavioral acts that is
essentially unchangeable and usually carried
(FAP) to completion once initiated.
Limp. Walled cells are flaccid in isotonic
flaccid surroundings, where there is no tendency for
water to enter.
(plural, flagella) A long cellular appendage
specialized for locomotion, formed from a
flagellum core of nine outer doublet microtubules and
two inner single microtubules, ensheathed in
an extension of plasma membrane.
In an angiosperm, a short stem with four sets
flower of modified leaves, bearing structures that
function in sexual reproduction.
The currently accepted model of cell
membrane structure, which envisions the
fluid mosaic model membrane as a mosaic of individually
inserted protein molecules drifting laterally in
a fluid bilayer of phospholipids.
An animal that lives by sucking nutrient-rich
fluid-feeder fluids from another living organism.
A microscopic structure in the ovary that
follicle contains the developing ovum and secretes
follicle-stimulating A protein hormone secreted by the anterior
pituitary that stimulates the production of
hormone (FSH) eggs by the ovaries and sperm by the testes.
That portion of the ovarian cycle during
follicular phase which several follicles in the ovary begin to
The pathway along which food is transferred
food chain from trophic level to trophic level, beginning
food vacuole A membranous sac formed by phagocytosis.
The elaborate, interconnected feeding
food web relationships in an ecosystem.
The portion of a moss sporophyte that
gathers sugars, amino acids, water, and
foot minerals from the parent gametophyte via
Behavior necessary to recognize, search for,
foraging capture, and consume food.
A marine protozoan that secretes a shell and
foram extends pseudopodia through pores in its
One of three ancestral and embryonic
forebrain regions of the vertebrate brain; develops into
the thalamus, hypothalamus, and cerebrum.
A preserved remnant or impression of an
fossil organism that lived in the past.
Energy deposits formed from the remains of
fossil fuels extinct organisms; fossil fuels include coal,
oil, and natural gas.
The chronicle of evolution over millions of
fossil record years of geologic time engraved in the order
in which fossils appear in rock strata.
Genetic drift attributable to colonization by a
founder effect limited number of individuals from a parent
An eye's center of focus and the place on the
fovea retina where photoreceptors are highly
A hereditary mental disorder, partially
explained by genomic imprinting and the
fragile X syndrome addition of nucleotides to a triplet repeat
near the end of an X chromosome.
A means of asexual reproduction whereby a
fragmentation single parent breaks into parts that
regenerate into whole new individuals.
A mutation occurring when the number of
nucleotides inserted or deleted is not a
frameshift mutation multiple of three, resulting in the improper
grouping of the following nucleotides into
A quantity of energy that interrelates entropy
symbolized by G (S) and the system's total
energy (H). The change in free energy of a
free energy system is calculated by the equation: G
equals delta H minus T times delta S, where
T is absolute temperature.
The initial investment of energy necessary to
free energy of activation start a chemical reaction; also called
A decline in the reproductive success of a
frequency-dependent morph resulting from the morph's phenotype
becoming too common in a population; a
selection cause of balanced polymorphism in
A mature ovary of a flower that protects
fruit dormant seeds and aids in their dispersal.
A specific configuration of atoms commonly
attached to the carbon skeletons of organic
functional group molecules and usually involved in chemical
Fungi The kingdom that contains the fungi.
A heterotrophic eukaryote that digests its
food externally and absorbs the resulting
small nutrient molecules. Most fungi consist
fungus of a netlike mass of filaments called hyphae.
Molds, mushrooms, and yeasts are
examples of fungi.
The cambium cells within the vascular
fusiform initials bundles. The name refers to the tapered
ends of these elongated cells.
A GTP-binding protein that relays signals
from a plasma membrane signal receptor,
known as a G-protein linked receptor, to
other signal-transduction proteins inside the
G protein cell. When such a receptor is activated, it in
turn activates the G protein, causing it to
bind a molecule of GTP in place of GDP.
Hydrolysis of the bound GTP to GDP
inactivates the G protein.
A nondividing state in which a cell has left
G0 phase the cell cycle.
The first growth phase of the cell cycle,
G1 phase consisting of the portion of interphase before
DNA synthesis begins.
The second growth phase of the cell cycle,
G2 phase consisting of the portion of interphase after
DNA synthesis occurs.
An organ that stores bile and releases it as
gallbladder needed into the small intestine.
(plural, gametangia) The reproductive organ
of bryophytes, consisting of the male
gametangium antheridium and female archegonium; a
multichambered jacket of sterile cells in
which gametes are formed.
A haploid cell such as an egg or sperm.
gamete Gametes unite during sexual reproduction to
produce a diploid zygote.
The mature gamete-producing structure of a
gametophores gametophyte body of a moss.
The multicellular haploid form in organisms
undergoing alternation of generations that
gametophyte mitotically produces haploid gametes that
unite and grow into the sporophyte
gamma aminobutyric An amino acid that functions as a CNS
(plural, ganglia) A cluster (functional group)
ganglion of nerve cell bodies in a centralized nervous
Mutations in these genes cause quot;gapsquot; in
Drosophila segmentation. The normal gene
gap genes products map out the basic subdivisions
along the anterior-posterior axis of the
A type of intercellular junction in animal cells
that allows the passage of material or current
gap junction between cells; also known as a
The uptake of molecular oxygen from the
gas exchange environment and the discharge of carbon
dioxide to the environment.
The collection of fluids secreted by the
gastric juice epithelium lining the stomach.
A digestive hormone, secreted by the
gastrin stomach, that stimulates the secretion of
An extensive pouch that serves as the site of
extracellular digestion and a passageway to
gastrovascular cavity disperse materials throughout most of an
The two-layered, cup-shaped embryonic
gastrulation The formation of a gastrula from a blastula.
A protein channel in a cell membrane that
gated channel opens or closes in response to a particular
A gated channel for a specific ion. By
gated ion channel opening and closing such channels, a cell
alters its membrane potential.
The separation of nucleic acids or proteins,
on the basis of their size and electrical
gel electrophoresis charge, by measuring their rate of movement
through an electrical field in a gel.
A discrete unit of hereditary information
gene consisting of a specific nucleotide sequence
in DNA (or RNA, in some viruses).
The selective synthesis of DNA, which
gene amplification results in multiple copies of a single gene,
thereby enhancing expression.
gene cloning The production of multiple copies of a gene.
The loss or gain of alleles in a population
gene flow due to the migration of fertile individuals or
gametes between populations.
The total aggregate of genes in a population
gene pool at any one time
The alternation of the genes of a person
gene therapy afflicted with a genetic disease.
generalized The random transfer of bacterial genes from
one bacterium to another.
Changes in the gene pool of a small
genetic drift population due to chance.
The direct manipulation of genes for practical
genetic engineering purposes.
An ordered list of genetic loci (genes or other
genetic map genetic markers) along a chromosome.
The general term for the production of
genetic recombination offspring with new combinations of traits
inherited from the two parents.
genetically modified An organism that has acquired one or more
genes by artificial means; also known as a
(GM) organism transgenic organism.
The scientific study of heredity and
genetics hereditary variation.
The complete complement of an organism's
genome genes; an organism's genetic material.
The parental effect on gene expression
whereby identical alleles have different
genomic imprinting effects on offspring, depending on whether
they arrive in the zygote via the ovum or via
A set of thousands of DNA segments from a
genomic library genome, each carried by a plasmid, phage,
or other cloning vector.
The study of whole sets of genes and their
genotype The genetic makeup of an organism.
(plural, genera) A taxonomic category above
genus the species level, designated by the first
word of a species' binomial Latin name.
The geographic area in which a population
geographic range lives.
The geographic area in which a population
geographic variation lives.
A time scale established by geologists that
reflects a consistent sequence of historical
geologic time scale periods, grouped into four eras:
Precambrian, Paleozoic, Mesozoic, and
Compounds that have the same molecular
geometric isomers formula but differ in the spatial arrangements
of their atoms.
A rapid J-shaped growth curve that typically
geometric population occurs when members have access to
abundant food and are free to reproduce at
growth their physiological capacity.
Three main layers that form the various
germ layers tissues and organs of an animal body.
Pregnancy; the state of carrying developing
gestation young within the female reproductive tract.
A class of related plant hormones that
stimulate growth in the stem and leaves,
gibberellins trigger the germination of seeds and
breaking of bud dormancy, and stimulate
fruit development with auxin.
A localized extension of the body surface of
gill many aquatic animals, specialized for gas
gill circulation The flow of blood through gills.
A phylum of gymnosperms represented by a
single extant species, Ginkgo biloba,
Ginkgophyta characterized by fanlike leaves that turn gold
and are deciduous in autumn.
glandular epithelia Epithelia that secrete chemical solutions.
glans penis The head end of the penis.
Supporting cells that are essential for the
glia structural integrity of the nervous system and
for the normal functioning of neurons.
A nonconducting cell of the nervous system
glial cell that provides support, insulation, and
protection for the neurons.
A ball of capillaries surrounded by Bowman's
glomerulus capsule in the nephron and serving as the
site of filtration in the vertebrate kidney.
A peptide hormone secreted by pancreatic
glucagon endocrine cells that raises blood glucose
levels; an antagonistic hormone to insulin.
A corticosteroid hormone secreted by the
glucocorticoid adrenal cortex that influences glucose
metabolism and immune function.
An amino acid that functions as a CNS
glyceraldehydes-3- The carbohydrate produced directly from the
A three-carbon alcohol with a hydroxyl group
glycerol on each carbon.
An amino acid that functions as a CNS
A fuzzy coat on the outside of animal cells,
glycocalyx made of sticky oligosaccharides.
An extensively branched glucose storage
glycogen polysaccharide found in the liver and muscle
of animals; the animal equivalent of starch.
The splitting of glucose into pyruvate.
Glycolysis is the one metabolic pathway that
glycolysis occurs in all living cells, serving as the
starting point for fermentation or aerobic
A protein covalently attached to a
A covalent bond formed between two
glycosidic linkage monosaccharides by a dehydration reaction.
gnathostomes The vertebrate subgroup that possess jaws.
A phylum of gymnosperms consisting of just
Gnetophyta three extant genera that are very different in
Typically unicellular, biflagellated, algae with
golden algae yellow and brown carotene and xanthophyll
An organelle in eukaryotic cells consisting of
stacks of flat membranous sacs that modify,
Golgi apparatus store, and route products of the endoplasmic
Hormones that stimulate the activities of the
gonadotropins testes and ovaries; a collective term for
follicle-stimulating and luteinizing hormones.
The male and female sex organs; the
gonads gamete-producing organs in most animals.
graft versus host