The A band corresponds to the length of the thick filaments in muscle fibers. The A site holds the tRNA carrying the next amino acid during translation. The abdominal cavity houses parts of the digestive, excretory, and reproductive systems and is separated from the thoracic cavity by the diaphragm.

1. The broad region that corresponds to the
A band length of the thick filaments.
One of three binding sites for tRNA during
translation, it holds the tRNA carrying the
A site next amino acid to be added to the
polypeptide chain; A stands for aminoacyl-
tRNA site.
The body cavity in mammals that primarily
houses parts of the digestive, excretory, and
abdominal cavity reproductive systems. It is separated from
the more cranial thoracic cavity by the
diaphragm.
Nonliving chemical and physical factors in
abiotic components the environment.
Genetically determined classes of human
blood that are based on the presence or
absence of carbohydrates A and B on the
ABO blood groups surface of red blood cells. The ABO blood
group phenotypes, also call blood types, are
A, B, AB, and O.

2. A plant hormone that generally acts to inhibit
abscisic acid (ABA) growth, promote dormancy, and help the
plant tolerate stressful conditions.
The uptake of small nutrient molecules by an
absorption organism's own body; the third main stage of
food processing, following digestion.
The range of a pigment's ability to absorb
absorption spectrum various wavelengths of light.
The very deep benthic communities near the
bottom of the ocean. This region is
abyssal zone characterized by continuous cold, extremely
high water pressure, low nutrients, and near
or total absence of light.
A group of ancient jawed fishes from the
acanthodians Devonian period.

3. Physiological adjustment to a change in an
acclimatization environmental factor.
The automatic adjustment of an eye to focus
accommodation on near objects.
acetyl CoA (acetyl The entry compound for the Krebs cycle in
cellular respiration; formed from a fragment
coenzyme A) of pyruvate attached to a coenzyme.
One of the most common neurotransmitters;
functions by binding to receptors and altering
the permeability of the postsynaptic
acetylcholine membrane to specific ions, either
depolarizing or hyperpolarizing the
membrane.
A substance that increases the hydrogen ion
acid concentration of a solution.

4. A mixture of recently swallowed food and
acid chyme gastric juice.
Rain, snow, or fog that is more acidic than
acid precipitation pH 5.6.
A solid-bodied animal lacking a cavity
acoelomate between the gut and outer body wall.
The discharge of a sperm's acrosome when
acrosomal reactions the sperm approaches an egg.
An organelle at the tip of a sperm cell that
acrosome helps the sperm penetrate the egg.

5. A globular protein that links into chains, two
of which twist helically about each other,
actin forming microfilaments in muscle and other
contractile elements in cells.
Actinistia The class of lobe-finned fishes.
Actinopterygii The class of ray-finned fishes.
A rapid change in the membrane potential of
an excitable cell, caused by stimulus-
action potential triggered, selective opening and closing of
voltage-sensitive gates in sodium and
potassium ion channels.
A profile of the relative performance of
action spectrum different wavelengths of light.

6. The amount of energy that reactants must
activation energy absorb before a chemical reaction will start.
A transcription factor that binds to an
activator enhancer and stimulates transcription of a
gene.
Immunity conferred by recovering from an
active immunity infectious disease.
The specific portion of an enzyme that
active site attaches to the substrate by means of weak
chemical bonds.
The movement of a substance across a
biological membrane against its
active transport concentration or electrochemical gradient
with the help of energy input and specific
transport proteins.

7. Inherited characteristics that enhance the
adaptations ability of an organism to survive and
reproduce in a particular environment.
An equilibrium state in a population when the
gene pool has allele frequencies that
adaptive peak maximize the average fitness of a
population's members.
The emergence of numerous species from a
common ancestor introduced into an
adaptive radiation environment, presenting a diversity of new
opportunities and problems.
Also called the anterior pituitary, it consists
of endocrine cells that synthesize and
adenohypophysis secrete several hormones directly into the
blood.
An enzyme that converts ATP to cyclic AMP
adenylyl cyclase in response to a chemical signal.

8. The attraction between different kinds of
adhesion molecules.
An endocrine gland located adjacent to the
kidney in mammals; composed of two
glandular portions: an outer cortex, which
adrenal gland responds to endocrine signals in reacting to
stress and effecting salt and water balance,
and a central medulla, which responds to
nervous inputs resulting from stress.
The central portion of an adrenal gland,
controlled by nerve signals, that secretes the
adrenal medulla fight-or-flight hormones epinephrine and
norepinephrine.
A peptide hormone released from the
adrenocorticotropic anterior pituitary, it stimulates the production
and secretion of steroid hormones by the
hormone adrenal cortex.
Roots extending from stems and leaves
adventitious above ground.

9. Containing oxygen; referring to an organism,
aerobic environment, or cellular process that
requires oxygen.
afferent arteriole The blood vessel supplying a nephron.
A branch of mammals that includes sloths,
Afrotheria anteaters, and armadillos.
The relative number of individuals of each
age structure age in a population.
An antibody-mediated immune response in
which bacteria or viruses are clumped
agglutination together, effectively neutralized, and
opsonized.

10. A fruit such as a blackberry that develops
aggregate fruit from a single flower that has several carpels.
A member of a jawless class of vertebrates
agnathan represented today by the lampreys and
hagfishes.
A type of behavior involving a contest of
some kind that determines which competitor
agnostic behavior gains access to some resource, such as
food or mates.
AIDS (acquired The name of the late stages of HIV infection;
defined by a specified reduction of T cells
immunodeficiency and the appearance of characteristic
secondary infections.
syndrome)
The conversion of pyruvate to carbon dioxide
alcohol fermentation and ethyl alcohol.

11. Organic compounds containing hydroxyl
alcohols groups.
An organic molecule with a carbonyl group
aldehyde located at the end of the carbon skeleton.
An adrenal hormone that acts on the distal
tubules of the kidney to stimulate the
aldosterone reabsorption of sodium (Na+) and the
passive flow of water from the filtrate.
(plural, algae) A photosynthetic, plantlike
alga protist.
A digestive tract consisting of a tube running
alimentary canal between a mouth and an anus.

12. One of four extra-embryonic membranes;
allantois serves as a repository for the embryo's
nitrogenous waste.
alleles Alternate versions of a gene.
The variation in the relative rates of growth
allometric growth of various parts of the body, which helps
shape the organism.
A mode of speciation induced when the
allopatric speciation ancestral population becomes segregated by
a geographic barrier.
A common type of polyploid species
resulting from two different species
allopolyploid interbreeding and combining their
chromosomes.

13. An action that occurs either completely or
all-or-none event not at all, such as the generation of an action
potential by a neuron.
A specific receptor site on some part of an
allosteric site enzyme molecule remote from the active
site.
A spiral shape constituting one form of the
alpha helix secondary structure of proteins, arising from
a specific hydrogen-bonding structure.
A life cycle in which there is both a
multicellular diploid form, the sporophyte,
alternation of generations and a multicellular haploid form, the
gametophyte; characteristic of plants.
A type of regulation at the RNA-processing
level in which different mRNA molecules are
alternative RNA splicing produced from the same primary transcript
depending on which RNA segments are
treated as exons and which as introns.

14. Behavior that reduces an individual's fitness
altruisim while increasing the fitness of another
individual.
The aiding of another individual at one's own
altruistic behavior risk or expense.
A protistan clade that includes
dinoflagellates, apicomplexans, and the
ciliates. Alveolates have small membrane-
Alveolata bounded cavities called alveoli under their
cell surfaces. The function of alveoli is
unknown.
(plural, alveoli) (1.) One of the deadend,
multilobed air sacs that constitute the gas
alveolus exchange surface of the lungs. (2.) One of
the milk-secreting sacs of epithelial tissue in
the mammary glands.
Neurons of the retina that help integrate
amacrine cell information before it is sent to the brain.

15. An organic compound with one or more
amine amino groups.
An organic molecule possessing both
amino acid carboxyl and amino groups. Amino acids
serve as the monomers of proteins.
A functional group that consists of a nitrogen
atom bonded to two hydrogen atoms; can
amino group act as a base in solution, accepting a
hydrogen ion and acquiring a charge of +1.
aminoacyl-tRNA An enzyme that joins each amino acid to the
correct tRNA.
synthetase
An enzyme found within the small intestine
that splits off one amino acid at a time,
aminopeptidase beginning at the opposite end of the
polypeptide containing a free carboxyl group.

16. A small and very toxic nitrogenous waste
ammonia produced by metabolism.
Shelled cephalopod animals that were the
dominant invertebrate predators for millions
ammonites of years ending with the mass extinctions at
the end of the Cretaceous period.
A technique for determining genetic
abnormalities in a fetus by the presence of
amniocentesis certain chemicals or defective fetal cells in
the amniotic fluid, obtained by aspiration
from a needle inserted into the uterus.
The innermost of four extraembryonic
amnion membranes; encloses a fluid-filled sac in
which the embryo is suspended.
A vertebrate possessing an amnion
amniote surrounding the embryo; reptiles, birds, and
mammals are amniotes.

17. A shelled, water-retaining egg that enables
amniotic egg reptiles, birds, and egg-laying mammals to
complete their life cycles on dry land.
A type of protist characterized by great
amoeba flexibility and the presence of pseudopodia.
An amoebalike cell that moves by
pseudopodia, found in most animals;
depending on the species, may digest and
amoebocyte distribute food, dispose of wastes, form
skeletal fibers, fight infections, and change
into other cell types.
The vertebrate class of amphibians,
Amphibia represented by frogs, salamanders, and
caecilians.
A molecule that has both a hydrophilic region
amphipathic molecule and a hydrophobic region.

18. The strengthening of stimulus energy that is
amplification otherwise too weak to be carried into the
nervous system.
Lacking oxygen; referring to an organism,
anaerobic environment, or cellular process that lacks
oxygen and may be poisoned by it.
A metabolic pathway that synthesizes a
anabolic pathway complex molecule from simpler compounds.
The use of inorganic molecules other than
anaerobic respiration oxygen to accept electrons at the quot;downhillquot;
end of electron transport chains.
The use of inorganic molecules other than
anagenesis oxygen to accept electrons at the quot;downhillquot;
end of electron transport chains.

19. The similarity of structure between two
analogy species that are not closely related;
attributable to convergent evolution.
The fourth subphase of mitosis, in which the
chromatids of each chromosome have
anaphase separated and the daughter chromosomes
are moving to the poles of the cell.
anaphylactic shock An acute, life-threatening, allergic response.
One of three groups of amniotes based on
anapsids key differences between their skulls.
anatomically modern Fully modern humans.
humans

20. anatomy The study of the structure of an organism.
The requirement that to divide, a cell must
anchorage dependence be attached to the substratum.
Adhesive junctions that link cells together
anchoring junctions into tissues.
The principal male steroid hormones, such
as testosterone, which stimulate the
androgens development and maintenance of the male
reproductive system and secondary sex
characteristics.
A chromosomal aberration in which certain
aneuploidy chromosomes are present in extra copies or
are deficient in number.

21. A flowering plant, which forms seeds inside a
angiosperm protective chamber called an ovary.
The ability to survive in a dormant state
anhydrobiosis when an organism's habitat dries up. Also
called cryptobiosis.
The portion of the egg where the least yolk is
animal pole concentrated. Opposite of vegetal pole.
anion A negatively charged ion.
A plant that completes its entire life cycle in a
annual single year or growing season.

22. Sensory appendages found in uniramians
antennae and crustaceans.
Also called the adenohypophysis, it consists
of endocrine cells that synthesize and
anterior pituitary secrete several hormones directly into the
blood.
Referring to the head end of a bilaterally
anterior symmetrical animal.
The terminal pollen sac of a stamen, inside
anther which pollen grains with male gametes form
in the flower of an angiosperm.
(plural, antheridia) In plants, the male
antheridium gametangium, a moist chamber in which
gametes develop.

23. The phylum of hornworts, small herbaceous
Anthocerophyta (non-woody) plants.
Anthophyta The phylum containing all angiosperms.
A member of a primate group made up of the
apes (gibbon, orangutan, gorilla,
anthropoid chimpanzee, and bonobo), monkeys, and
humans.
A chemical that kills bacteria or inhibits their
antibiotic growth.
An antigen-binding immunoglobulin,
antibody produced by B cells, that functions as the
effector in an immune response.

24. A specialized base triplet at one end of a
tRNA molecule that recognizes a particular
anticodon complementary codon on an mRNA
molecule.
A hormone that is part of an elaborate
antidiuretic hormone feedback scheme that helps regulate the
osmolarity of the blood.
A foreign macromolecule that does not
antigen belong to the host organism and that elicits
an immune response.
The process by which an MHC molecule
cradles a fragment of an intracellular protein
antigen presentation antigen in its hammocklike groove, carries it
to the cell surface, and quot;presentsquot; the protein
to an antigen receptor on a nearby T cell.
Transmembrane versions of antibody
molecules that B cells and T cells use to
antigen receptor recognize specific antigens. Also called
membrane antibodies.

25. Cells that ingest bacteria and viruses and
antigen-presenting cell then destroy them. Class II MHC molecules
in these cells collect peptide remnants of this
(APCs) degradation and present them to helper T
cells.
The order of frogs and toads that includes
anura tailless tetrapod amphibians.
anurans The group of frogs and toads.
The part of the ocean beneath the photic
aphotic zone zone, where light does not penetrate
sufficiently for photosynthesis to occur.
Concentration of growth at the tip of a plant
apical dominance shoot, where a terminal bud partially inhibits
axillary bud growth.

26. A limb-bud organizing region consisting of a
apical ectodermal ridge thickened area of ectoderm at the tip of a
limb bud.
Embryonic plant tissue in the tips of roots
apical meristem and in the buds of shoots that supplies cells
for the plant to grow in length.
One of a group of parasitic protozoans,
apicomplexan some of which cause human diseases.
The order of caecilians that includes legless
apoda amphibians.
apodans The group of caecilians.

27. apomixes The asexual production of seeds.
A derived phenotypic character, or
apomorphic character homology, that evolved after a branch
diverged from a phylogenetic tree.
In plants, the nonliving continuum formed by
apoplast the extracellular pathway provided by the
continuous matrix of cell walls.
Programmed cell death brought about by
signals that trigger the activation of a
apoptosis cascade of quot;suicidequot; proteins in the cells
destined to die.
The bright coloration of animals with
aposematic coloration effective physical or chemical defenses that
acts as a warning to predators.

28. A small, fingerlike extension of the vertebrate
appendix cecum; contains a mass of white blood cells
that contribute to immunity.
A transport protein in the plasma membrane
of a plant or animal cell that specifically
aquaporin facilitates the diffusion of water across the
membrane (osmosis).
Plasmalike liquid in the space between the
lens and the cornea in the vertebrate eye;
aqueous humor helps maintain the shape of the eye,
supplies nutrients and oxygen to its tissues,
and disposes of its wastes.
aqueous solution A solution in which water is the solvent.
The animal class that includes scorpions,
Arachnida spiders, ticks, and mites.

29. One of two prokaryotic domains, the other
Archaea being the Bacteria.
Primitive eukaryotic group that includes
diplomonads, such as Giardia; some
Archaezoa systematists assign kingdom status to
archezoans.
(plural, archegonia) In plants, the female
archegonium gametangium, a moist chamber in which
gametes develop.
The endoderm-lined cavity, formed during
archenteron the gastrulation process, that develops into
the digestive tract of an animal.
The reptilian group that includes crocodiles,
archosaurs alligators, dinosaurs, and birds.

30. A vessel that conveys blood between an
arteriole artery and a capillary bed.
A cardiovascular disease caused by the
arteriosclerosis formation of hard plaques within the arteries.
A vessel that carries blood away from the
artery heart to organs throughout the body.
Segmented coelomates with exoskeletons
arthropod and jointed appendages.
The most diverse phylum in the animal
kingdom; includes the horseshoe crab,
arachnids (e.g., spiders, ticks, scorpions,
and mites), crustaceans (e.g., crayfish,
Arthropoda lobsters, crabs, barnacles), millipedes,
centipedes, and insects. Arthropods are
characterized by a chitinous exoskeleton,
molting, jointed appendages, and a body
formed of distinct groups of segments.

31. The selective breeding of domesticated
artificial selection plants and animals to encourage the
occurrence of desirable traits.
ascocarps Macroscopic fruiting bodies of sac fungi.
(plural, asci) A saclike spore capsule located
at the tip of the ascocarp in dikaryotic
ascus hyphae; defining feature of the Ascomycota
division of fungi.
A type of reproduction involving only one
parent that produces genetically identical
asexual reproduction offspring by budding or by the division of a
single cell or the entire organism into two or
more parts.
An amino acid that functions as a CNS
aspartate neurotransmitter.

32. The acquired ability to associate one
associative learning stimulus with another; also called classical
conditioning.
A type of nonrandom mating in which mating
assortative mating partners resemble each other in certain
phenotypic characters.
Glial cells that provide structural and
astrocytes metabolic support for neurons.
A carbon atom covalently bonded to four
asymmetric carbon different atoms or groups of atoms.
Cell division in which one daughter cell
asymmetric cell division receives more cytoplasm than the other
during mitosis.

33. A cardiovascular disease in which growths
atherosclerosis called plaques develop on the inner walls of
the arteries, narrowing their inner diameters.
The smallest unit of matter that retains the
atom properties of an element.
An atom's central core, containing protons
atom nucleus and neutrons.
The number of protons in the nucleus of an
atom, unique for each element and
atomic number designated by a subscript to the left of the
elemental symbol.
The total atomic mass, which is the mass in
atomic weight grams of one mole of the atom.

34. An adenine-containing nucleoside
ATP (adenosine triphosphate that releases free energy when
its phosphate bonds are hydrolyzed. This
triphosphate) energy is used to drive endergonic reactions
in cells.
A cluster of several membrane proteins
found in the mitochondrial crista (and
bacterial plasma membrane) that function in
chemiosmosis with adjacent electron
ATP synthase transport chains, using the energy of a
hydrogen ion concentration gradient to make
ATP. ATP synthases provide a port through
which hydrogen ions diffuse into the matrix
of a mitrochondrion.
A peptide hormone that opposes the renin-
atrial natriuretic factor angiotensin-aldosterone system (RAAS).
A region of specialized muscle tissue
between the right atrium and right ventricle.
atrioventricular (AV) note It generates electrical impulses that primarily
cause the ventricles to contract.
A valve in the heart between each atrium
atrioventricular valve and ventricle that prevents a backflow of
blood when the ventricles contract.

35. (plural, atria) A chamber that receives blood
atrium returning to the vertebrate heart.
According to this model, eukaryotic cells
evolved by the specialization of internal
autogenesis model membranes originally derived from
prokaryotic plasma membranes.
An immunological disorder in which the
autoimmune disease immune system turns against itself.
A subdivision of the motor nervous system of
vertebrates that regulates the internal
autonomic disease environment; consists of the sympathetic
and parasympathetic divisions.
A subdivision of the motor nervous system of
autonomic nervous vertebrates that regulates the internal
environment; consists of the sympathetic
system and parasympathetic divisions.

36. A type of polyploid species resulting from
one species doubling its chromosome
autopolyploid number to become tetraploid, which may
self-fertilize or mate with other tetraploids.
A chromosome that is not directly involved in
autosome determining sex, as opposed to a sex
chromosome.
An organism that obtains organic food
molecules without eating other organisms or
substances derived from other organisms.
autotroph Autotrophs use energy from the sun or from
the oxidation of inorganic substances to
make organic molecules from inorganic
ones.
A class of plant hormones, including
indoleacetic acid (IAA), having a variety of
effects, such as phototropic response
auxins through the stimulation of cell elongation,
stimulation of secondary growth, and the
development of leaf traces and fruit.
A nutritional mutant that is unable to
synthesize and that cannot grow on media
auxotroph lacking certain essential molecules normally
synthesized by wild-type strains of the same
species.

37. The vertebrate class of birds, characterized
Aves by feathers and other flight adaptations.
An embryonic shoot present in the angle
axillary bud formed by a leaf and stem.
A typically long extension, or process, from a
axon neuron that carries nerve impulses away
from the cell body toward target cells.
A type of lymphocyte that develops in the
B lymphocyte (B cell) bone marrow and later produces antibodies,
which mediate humoral immunity.
One of two prokaryotic domains, the other
Bacteria being the Archaea.

38. bacterial artificial An artificial version of a bacterial
chromosome that can carry inserts of
chromosome (BAC) 100,000–500,000 base pairs.
A virus that infects bacteria; also called a
bacteriophage phage. See phage.
A photosynthetic pigment found in
bacteriorhodopsin halophiles. It is very similar to the visual
pigments in the retinas of our eyes.
(plural, bacteria) A prokaryotic
bacterium microorganism in Domain Bacteria.
A form of Rhizobium contained within the
bacteroids vesicles formed by the root cells of a root
nodule.

39. A bone that is contained in, and helps stiffen,
baculum the penis of rodents, raccoons, walruses,
and several other mammals.
The ability of natural selection to maintain
balanced polymorphism diversity in a population.
All tissues external to the vascular cambium
in a plant growing in thickness, consisting of
bark phloem, phelloderm, cork cambium, and
cork.
A dense object lying along the inside of the
Barr body nuclear envelope in female mammalian cells,
representing an inactivated X chromosome.
Contraception that relies upon a physical
barrier methods barrier to block the passage of sperm.
Examples include condoms and diaphragms.

40. Glands near the vaginal opening in a human
Bartholin’s glands female that secrete lubricating fluid during
sexual arousal.
A eukaryotic cell organelle consisting of a 9
+ 0 arrangement of microtubule triplets; may
basal body organize the microtubule assembly of a
cilium or flagellum; structurally identical to a
centriole.
basal metabolic rate The minimal number of kilocalories a resting
animal requires to fuel itself for a given time.
(BMR)
A cluster of nuclei deep within the white
basal nuclei matter of the cerebrum.
A substance that reduces the hydrogen ion
base concentration of a solution.

41. The floor of an epithelial membrane on which
basement membrane the basal cells rest.
A point mutation; the replacement of one
nucleotide and its partner in the
base-pair substitution complementary DNA strand by another pair
of nucleotides.
Elaborate fruiting bodies of a dikaryotic
basidiocarps mycelium of a club fungus.
(plural, basidia) A reproductive appendage
that produces sexual spores on the gills of
basidium mushrooms. The fungal division
Basidiomycota is named for this structure.
A circulating leukocyte that produces
basophil histamine.

42. A type of mimicry in which a harmless
Batesian mimicry species looks like a species that is
poisonous or otherwise harmful to predators.
behavior What an animal does and how it does it.
A heuristic approach based on the
expectation that Darwinian fitness
behavioral ecology (reproductive success) is improved by
optimal behavior.
A mass of abnormal cells that remains at the
benign tumor site of origin.
The bottom surfaces of aquatic
benthic zone environments.

43. The communites of organisms living in the
benthos benthic zone of an aquatic biome.
The source of insulin within the islets of
beta cell Langerhans, nestled within the pancreas.
A metabolic sequence that breaks fatty acids
beta oxidation down to two-carbon fragments which enter
the Krebs cycle as acetyl CoA.
One form of the secondary structure of
proteins in which the polypeptide chain folds
beta (b) pleated sheet back and forth, or where two regions of the
chain lie parallel to each other and are held
together by hydrogen bonds.
A plant that requires two years to complete
biennial its life cycle.

44. A life history in which adults have but a
single reproductive opportunity to produce
big-bang reproduction large numbers of offspring, such as the life
history of the Pacific salmon. Also known as
semelparity.
Characterizing a body form with a central
bilateral symmetry longitudinal plane that divides the body into
two equal but opposite halves.
Members of the branch of eumetazoans
bilateria possessing bilateral symmetry.
A mixture of substances that is produced in
the liver, stored in the gall bladder, and acts
bile as a detergent to aid in the digestion and
absorption of fats.
The type of cell division by which
prokaryotes reproduce. Each dividing
binary fission daughter cell receives a copy of the single
parental chromosome.

45. The two-part latinized name of a species,
binomial consisting of genus and specific epithet.
All of the variety of life; usually refers to the
variety of species that make up a
community; concerns both species richness
biodiversity (the total number of different species) and
the relative abundance of the different
species.
The current rapid decline in the variety of life
biodiversity crisis on Earth, largely due to the effects of human
culture.
A relatively small area with an exceptional
biodiversity hot spot concentration of endemic species.
The study of how organisms manage their
bioenergetics energy resources.

46. The principle that all life arises by the
biogenesis reproduction of preexisting life.
biogenic amines Neurotransmitters derived from amino acids.
Any of the various nutrient circuits, which
biogeochemical cycles involve both biotic and abiotic components of
ecosystems.
The study of the past and present
biogeography distribution of species.
An internal timekeeper that controls an
organism's biological rhythms; marks time
with or without environmental cues but often
biological clock requires signals from the environment to
remain tuned to an appropriate period. See
also circadian rhythm.

47. A trophic process in which retained
biological magnification substances become more concentrated with
each link in the food chain.
The definition of a species as a population or
group of populations whose members have
biological species concept the potential in nature to interbreed and
produce fertile offspring; a biological species
is also called a sexual species.
The dry weight of organic matter comprising
biomass a group of organisms in a particular habitat.
One of the world's major ecosystems,
classified according to the predominant
biome vegetation and characterized by adaptations
of organisms to that particular environment.
The use of living organisms to detoxify and
bioremediation restore polluted and degraded ecosystems.

48. The entire portion of Earth inhabited by life;
biosphere the sum of all the planet's ecosystems.
The manipulation of living organisms or their
biotechnology components to produce useful products.
Pertaining to the living organisms in the
biotic environment.
All the organisms that are part of the
biotic components environment.
Neurons that synapse with the axons of rods
bipolar cell and cones in the retina of the eye.

49. Any of a class of warm-blooded vertebrates
distinguished by having the body more or
birds less completely covered with feathers and
the forelimbs modified as wings.
Chemical contraceptives that inhibit
ovulation, retard follicular development, or
birth control pills alter a woman's cervical mucus to prevent
sperm from entering the uterus.
A flower equipped with both stamens and
bisexual flower carpels.
A leaflike structure of a seaweed that
blade provides most of the surface area for
photosynthesis.
The fluid-filled cavity that forms in the center
blastocoels of the blastula embryo.

50. An embryonic stage in mammals; a hollow
blastocyst ball of cells produced one week after
fertilization in humans.
An embryonic cap of dividing cells resting on
blastodisc a large undivided yolk.
blastomeres Small cells of an early embryo.
The opening of the archenteron in the
blastopore gastrula that develops into the mouth in
protostomes and the anus in deuterostomes.
The hollow ball of cells marking the end
blastula stage of cleavage during early embryonic
development.

51. A type of connective tissue with a fluid matrix
blood called plasma in which blood cells are
suspended.
The hydrostatic force that blood exerts
blood pressure against the wall of a vessel.
A set of tubes through which the blood
blood vessel moves through the body.
A specialized capillary arrangement in the
brain that restricts the passage of most
blood-brain barrier substances into the brain, thereby preventing
dramatic fluctuations in the brain's
environment.
A fluid-containing space between the
body cavity digestive tract and the body wall.

52. bolus A lubricated ball of chewed food.
The quantity of energy that must be
absorbed to break a particular kind of
bond energy chemical bond; equal to the quantity of
energy the bond releases when it forms.
A type of connective tissue, consisting of
bone living cells held in a rigid matrix of collagen
fibers embedded in calcium salts.
Organs of gas exchange in spiders,
book lungs consisting of stacked plates contained in an
internal chamber.
Genetic drift resulting from the reduction of a
population, typically by a natural disaster,
bottleneck effect such that the surviving population is no
longer genetically representative of the
original population.

53. A model of community organization in which
mineral nutrients control community
organization because nutrients control plant
bottom-up model numbers, which in turn control herbivore
numbers, which in turn control predator
numbers.
A cup-shaped receptacle in the vertebrate
kidney that is the initial, expanded segment
Bowman’s capsule of the nephron where filtrate enters from the
blood.
Also called lamp shells, these animals
superficially resemble clams and other
brachiopod bivalve mollusks, but the two halves of the
brachiopod shell are dorsal and ventral to
the animal rather than lateral, as in clams.
A hormone produced by neurosecretory cells
in the insect brain. It promotes development
brain hormone by stimulating the prothoracic glands to
secrete ecdysone.
The hindbrain and midbrain of the vertebrate
central nervous system. In humans, it forms
brainstem a cap on the anterior end of the spinal cord,
extending to about the middle of the brain.

54. A brain center that directs the activity of
breathing control center organs involved in breathing.
Fine branches of the bronchus that transport
bronchioles air to alveoli.
(plural, bronchi) One of a pair of breathing
bronchus tubes that branch from the trachea into the
lungs.
One of a group of marine, multicellular,
brown algae autotrophic protists, the most common type
of seaweed. Brown algae include the kelps.
A special tissue in some mammals, located
brown fat in the neck and between the shoulders, that
is specialized for rapid heat production.

55. The phylum of mosses. Note that the term
quot;bryophyte quot; refers instead to the informal
group of mosses, liverworts, and hornworts,
Bryophyta nonvascular plants that inhabit the land but
lack many of the terrestrial adaptations of
vascular plants.
A moss, liverwort, or hornwort; a
nonvascular plant that inhabits the land but
bryophytes lacks many of the terrestrial adaptations of
vascular plants.
A moss, liverwort, or hornwort; a
nonvascular plant that inhabits the land but
bryozoans lacks many of the terrestrial adaptations of
vascular plants.
An asexual means of propagation in which
outgrowths from the parent form and pinch
budding off to live independently or else remain
attached to eventually form extensive
colonies.
Used in reference to the gains and losses of
various materials and energy. Most energy
and materials budgets are interconnected,
budgets with changes in the flux of one component
affecting the exchanges of other
components.

56. A substance that consists of acid and base
forms in a solution and that minimizes
buffer changes in pH when extraneous acids or
bases are added to the solution.
One of a pair of glands near the base of the
penis in the human male that secrete fluid
bulbourethral gland that lubricates and neutralizes acids in the
urethra during sexual arousal.
The movement of water due to a difference
bulk flow in pressure between two locations.
Animals that eat relatively large pieces of
bulk-feeder food.
A type of photosynthetic cell arranged into
bundle-sheath cell tightly packed sheaths around the veins of a
leaf.

57. A plant that uses the Calvin cycle for the
initial steps that incorporate CO2 into organic
C3 Plant material, forming a three-carbon compound
as the first stable intermediate.
A plant that uses the Calvin cycle for the
initial steps that incorporate CO2 into organic
C4 Plant material, forming a three-carbon compound
as the first stable intermediate.
An important class of cell-to-cell adhesion
cadherins molecules.
A mammalian thyroid hormone that lowers
calcitonin blood calcium levels.
A mass of dividing, undifferentiated cells at
callus the cut end of a shoot.

58. An intracellular protein to which calcium
calmodulin binds in its function as a second messenger
in hormone action.
The amount of heat energy required to raise
the temperature of 1 g of water by 1°C; also
the amount of heat energy that 1 g of water
calorie (cal) releases when it cools by 1°C. The Calorie
(with a capital C), usually used to indicate
the energy content of food, is a kilocalorie.
The second of two major stages in
photosynthesis (following the light reactions),
Calvin cycle involving atmospheric CO2 fixation and
reduction of the fixed carbon into
carbohydrate.
A plant that uses crassulacean acid
metabolism, an adaptation for
photosynthesis in arid conditions, first
discovered in the family Crassulaceae.
CAM plant Carbon dioxide entering open stomata
during the night is converted into organic
acids, which release CO2 for the Calvin cycle
during the day, when stomata are closed.
A burst of evolutionary origins when most of
the major body plans of animals appeared in
Cambrian explosion a relatively brief time in geologic history;
recorded in the fossil record about 545 to
525 million years ago.

59. cAMP receptor protein A regulatory protein that directly stimulates
gene expression.
(CRP)
canaliculi Minute canals in a bodily structure.
The uppermost layer of vegetation in a
canopy terrestrial biome.
A microscopic blood vessel that penetrates
the tissues and consists of a single layer of
capillary endothelial cells that allows exchange
between the blood and interstitial fluid.
A network of capillaries that infiltrate every
capillary bed organ and tissue in the body.

60. The protein shell that encloses a viral
capsid genome. It may be rod-shaped, polyhedral,
or more complete in shape.
A sticky layer that surrounds the cell walls of
some bacteria, protecting the cell surface
capsule and sometimes helping to glue the cell to
surfaces.
A sugar (monosaccharide) or one of its
carbohydrate dimers (disaccharides) or polymers
(polysaccharides).
The incorporation of carbon from CO2 into an
organic compound by an autotrophic
carbon fixation organism (a plant, another photosynthetic
organism, or a chemoautotrophic bacterium).
A functional group present in aldehydes and
carbonyl group ketones and consisting of a carbon atom
double-bonded to an oxygen atom.

61. A functional group present in organic acids
and consisting of a single carbon atom
carboxyl group double-bonded to an oxygen atom and also
bonded to a hydroxyl group.
An organic compound containing a carboxyl
carboxylic acid group.
An enzyme found within the small intestine
that splits off one amino acid at a time,
carboxypeptidase beginning at the end of the polypeptide that
has a free carboxyl group.
carcinogen A chemical agent that causes cancer.
The alternating contractions and relaxations
cardiac cycle of the heart.The alternating contractions and
relaxations of the heart.

62. A type of muscle that forms the contractile
cardiac muscle wall of the heart; its cells are joined by
intercalated discs that relay each heartbeat.
The volume of blood pumped per minute by
cardiac output the left ventricle of the heart.
cardiovascular disease Diseases of the heart and blood vessels.
A closed circulatory system with a heart and
branching network of arteries, capillaries,
cardiovascular system and veins; the system is characteristic of
vertebrates.
The group of birds with a carina, or sternal
carnites keel, supporting their large breast muscles.

63. An animal, such as a shark, hawk, or spider,
carnivore that eats other animals.
An accessory pigment, either yellow or
orange, in the chloroplasts of plants. By
absorbing wavelengths of light that
carotenoid chlorophyll cannot, carotenoids broaden the
spectrum of colors that can drive
photosynthesis.
The female reproductive organ of a flower,
carpel consisting of the stigma, style, and ovary.
In human genetics, an individual who is
heterozygous at a given genetic locus, with
one normal allele and one potentially harmful
carrier recessive allele. The heterozygote is
phenotypically normal for the character
determined by the gene but can pass on the
harmful allele to offspring.
The maximum population size that can be
carrying capacity supported by the available resources,
symbolized as K.

64. A type of flexible connective tissue with an
cartilage abundance of collagenous fibers embedded
in chondrin.
A water-impermeable ring of wax around
endodermal cells in plants that blocks the
Casparian strip passive flow of water and solutes into the
stele by way of cell walls.
A metabolic pathway that releases energy by
catabolic pathway breaking down complex molecules to simpler
compounds.
In E. coli, a helper protein that stimulates
catabolite activator gene expression by binding within the
promoter region of an operon and enhancing
protein (CAP) the promoter's ability to associate with RNA
polymerase.
A chemical agent that changes the rate of a
catalyst reaction without being consumed by the
reaction.

65. The hypothesis by Georges Cuvier that each
boundary between strata corresponded in
catastrophism time to a catastrophe, such as a flood or
drought, that had destroyed many of the
species living there at that time.
A class of compounds, including epinephrine
catecholamines and norepinephrine, that are synthesized
from the amino acid tyrosine.
An ion with a positive charge, produced by
cation the loss of one or more electrons.
A process in which positively charged
minerals are made available to a plant when
cation exchange hydrogen ions in the soil displace mineral
ions from the clay particles.
A T cell surface protein, present on most
CD4 helper T cells, CD4 binds to part of the class
II MHC protein.

66. A T cell surface protein that enhances the
CD8 interaction between the antigen-presenting
infected cell and a cytotoxic T cell.
A limited gene library using complementary
cDNA library DNA. The library includes only the genes
that were transcribed in the cells examined.
(plural, ceca) A blind outpocket of a hollow
cecum organ such as an intestine.
The simplest collection of matter that can
cell live.
Glycoproteins that contribute to cell
cell adhesion molecules migration and stable tissue structure.

67. The part of a cell, such as a neuron, that
cell body houses the molecules.
A region in the cytoplasm near the nucleus
cell center from which microtubules originate and
radiate.
An ordered sequence of events in the life of
a eukaryotic cell, from its origin in the
cell cycle division of a parent cell until its own division
into two; composed of the M, G1, S, and G2
phases.
A cyclically operating set of molecules in the
cell cycle control system cell that triggers and coordinates key events
in the cell cycle.
cell division The reproduction of cells.

68. The disruption of a cell and separation of its
cell fractionation organelles by centrifugation.
cell lineage The ancestry of a cell.
A double membrane across the midline of a
cell plate dividing plant cell, between which the new
cell wall forms during cytokinesis.
A protective layer external to the plasma
membrane in plant cells, bacteria, fungi, and
some protists. In plant cells, the wall is
formed of cellulose fibers embedded in a
cell wall polysaccharide-protein matrix. The primary
cell wall is thin and flexible, whereas the
secondary cell wall is stronger and more
rigid and is the primary constituent of wood.
The type of immunity that functions in
defense against fungi, protists, bacteria, and
cell-mediated immunity viruses inside host cells and against tissue
transplants, with highly specialized cells that
circulate in the blood and lymphoid tissue.

69. The structural and functional divergence of
cells as they become specialized during a
cellular differentiation multicellular organism's development;
dependent on the control of gene
expression.
The most prevalent and efficient catabolic
pathway for the production of ATP, in which
cellular respiration oxygen is consumed as a reactant along with
the organic fuel.
A type of protist that has unicellular
cellular slime mold amoeboid cells and multicellular reproductive
bodies in its life cycle.
A structural polysaccharide of cell walls,
cellulose consisting of glucose monomers joined by b-
1, 4-glycosidic linkages.
A temperature scale (°C) equal to 5/9 (°F
232) that measures the freezing point of
Celsius scale water at 0°C and the boiling point of water at
100°C.

70. The narrow cavity in the center of the spinal
central canal cord that is continuous with the fluid-filled
ventricles of the brain.
central nervous system In vertebrate animals, the brain and spinal
cord.
(CNS)
A membranous sac in a mature plant cell
central vacuole with diverse roles in reproduction, growth,
and development.
A structure in an animal cell composed of
cylinders of microtubule triplets arranged in a
centriole 9 + 0 pattern. An animal cell usually has a
pair of centrioles involved in cell division.
The centralized region joining two sister
centromere chromatids.

71. Material present in the cytoplasm of all
centrosome eukaryotic cells, important during cell
division; the microtubule-organizing center.
An evolutionary trend toward the
cephalization concentration of sensory equipment on the
anterior end of the body.
A chordate without a backbone, represented
cephalochordate by lancelets, tiny marine animals.
Part of the vertebrate hindbrain
(rhombencephalon) located dorsally;
cerebellum functions in unconscious coordination of
movement and balance.
Part of the vertebrate hindbrain
(rhombencephalon) located dorsally;
cerebral cortex functions in unconscious coordination of
movement and balance.

72. The surface of the cerebrum; the largest and
most complex part of the mammalian brain,
containing sensory and motor nerve cell
cerebral cortex bodies of the cerebrum; the part of the
vertebrate brain most changed through
evolution.
cerebral hemisphere The right or left side of the vertebrate brain.
Blood-derived fluid that surrounds, protects,
cerebrospinal fluid against infection, nourishes, and cushions
the brain and spinal cord.
The dorsal portion, composed of right and
left hemispheres, of the vertebrate forebrain;
cerebrum the integrating center for memory, learning,
emotions, and other highly complex
functions of the central nervous system.
The neck of the uterus, which opens into the
cervix vagina.

73. A scrubland biome of dense, spiny
evergreen shrubs found at midlatitudes
chaparral along coasts where cold ocean currents
circulate offshore; characterized by mild,
rainy winters and long, hot, dry summers.
Protein molecules that assist the proper
chaperonin folding of other proteins.
character A heritable feature.
The green algal group that shares two
ultrastructural features with land plants. They
Charophyceans are considered to be the closest relatives of
land plants.
A critical control point in the cell cycle where
checkpoint stop and go-ahead signals can regulate the
cycle.

74. Clawlike feeding appendages characteristic
chelicerae of the chelicerate group.
The animal phylum that includes horseshoe
Chelicerata crabs, scorpions, ticks, spiders, and an
extinct group called the eurypterids.
Members of the animal phylum that includes
chelicerates horseshoe crabs, scorpions, ticks, spiders,
and an extinct group called the eurypterids.
An attraction between two atoms resulting
from a sharing of outer-shell electrons or the
chemical bond presence of opposite charges on the atoms;
the bonded atoms gain complete outer
electron shells.
Energy stored in the chemical bonds of
chemical energy molecules; a form of potential energy.

75. In a reversible chemical reaction, the point at
chemical equilibrium which the rate of the forward reaction equals
the rate of the reverse reaction.
A process leading to chemical changes in
chemical reaction matter; involves the making and/or breaking
of chemical bonds.
chemically-gated ion Specialized ion channels that open or close
in response to a chemical stimulus.
channels
An energy-coupling mechanism that uses
energy stored in the form of a hydrogen ion
gradient across a membrane to drive cellular
chemiosmosis work, such as the synthesis of ATP. Most
ATP synthesis in cells occurs by
chemiosmosis.
An organism that needs only carbon dioxide
chemoautotroph as a carbon source but that obtains energy
by oxidizing inorganic substances.

76. An organism that must consume organic
chemoheterotroph molecules for both energy and carbon.
A group of about 50 different proteins
secreted by blood vessel endothelial cells
and monocytes. These molecules bind to
chemokin receptors on many types of leukocytes and
induce numerous changes central to
inflammation.
A receptor that transmits information about
chemoreceptor the total solute concentration in a solution or
about individual kinds of molecules.
(plural, chiasmata) The X-shaped,
microscopically visible region representing
chiasma homologous chromatids that have
exchanged genetic material through crossing
over during meiosis.
Chilopoda The animal class that includes centipedes.

77. A structural polysaccharide of an amino
chitin sugar found in many fungi and in the
exoskeletons of all arthropods.
A green pigment located within the
chloroplasts of plants. Chlorophyll a can
chlorophyll participate directly in the light reactions,
which convert solar energy to chemical
energy.
A type of blue-green photosynthetic pigment
chlorophyll a that participates directly in the light reactions.
A type of yellow-green accessory
chlorophyll b photosynthetic pigment that transfers energy
to chlorophyll a.
An organelle found only in plants and
photosynthetic protists that absorbs sunlight
chloroplast and uses it to drive the synthesis of organic
compounds from carbon dioxide and water.

78. A flagellated feeding cell found in sponges.
Also called a collar cell, it has a collarlike
choanocyte ring that traps food particles around the base
of its flagellum.
A hormone released from the walls of the
cholecystokinin (CCK) duodenum in response to the presence of
amino acids or fatty acids.
A steroid that forms an essential component
of animal cell membranes and acts as a
cholesterol precursor molecule for the synthesis of other
biologically important steroids.
The vertebrate class of cartilaginous fishes,
Chondrichthyes represented by sharks and their relatives.
A protein-carbohydrate complex secreted by
chondrin chondrocytes; chondrin and collagen fibers
form cartilage.

79. chondrocytes Cartilage cells.
A member of a diverse phylum of animals
that possess a notochord; a dorsal, hollow
chordate nerve cord; pharyngeal gill slits; and a
postanal tail as an embryo.
The outermost of four extraembryonic
chorion membranes; contributes to the formation of
the mammalian placenta.
A technique for diagnosing genetic and
chorionic villus sampling congenital defects in a fetus by removing
and analyzing a small sample of the fetal
(CVS) portion of the placenta.
A thin, pigmented inner layer of the
choroid vertebrate eye.

80. The complex of DNA and proteins that
makes up a eukaryotic chromosome. When
chromatin the cell is not dividing, chromatin exists as a
mass of very long, thin fibers that are not
visible with a light microscope.
In some classification systems, a kingdom
chromista consisting of brown algae, golden algae, and
diatoms.
A threadlike, gene-carrying structure found in
the nucleus. Each chromosome consists of
chromosome one very long DNA molecule and associated
proteins. See chromatin.
A basic principle in biology stating that genes
chromosome theory of are located on chromosomes and that the
behavior of chromosomes during meiosis
inheritance accounts for inheritance patterns.
A DNA mapping technique that begins with a
gene or other sequence that has already
been cloned, mapped, and sequenced and
chromosome walking quot;walksquot; along the chromosomal DNA from
that locus, producing a map of overlapping
restriction fragments.

81. Small intracellular globules composed of fats
chylomicron that are mixed with cholesterol and coated
with special proteins.
An enzyme found in the duodenum. It is
chymotrypsin specific for peptide bonds adjacent to certain
amino acids.
Mainly aquatic primitive fungi that form
uniflagellated spores (zoospores). The
chytrid chytrids and fungi are now thought to form a
monophyletic branch of the eukaryotic tree.
A type of protozoan that moves by means of
ciliate cilia.
A portion of the vertebrate eye associated
with the lens. It produces the clear, watery
ciliary body aqueous humor that fills the anterior cavity of
the eye.

82. (plural, cilia) A short cellular appendage
specialized for locomotion, formed from a
cilium core of nine outer doublet microtubules and
two inner single microtubules ensheathed in
an extension of plasma membrane.
A physiological cycle of about 24 hours that
is present in all eukaryotic organisms and
circadian rhythm that persists even in the absence of external
cues.
clade Each evolutionary branch in a cladogram.
A taxonomic approach that classifies
organisms according to the order in time at
cladistics which branches arise along a phylogenetic
tree, without considering the degree of
morphological divergence.
A pattern of evolutionary change that
produces biological diversity by budding one
cladogenesis or more new species from a parent species
that continues to exist; also called branching
evolution.

83. A dichotomous phylogenetic tree that
branches repeatedly, suggesting a
cladogram classification of organisms based on the time
sequence in which evolutionary branches
arise.
In classification, the taxonomic category
class above order.
The animal group that includes scorpions,
class Arachnida spiders, ticks, and mites.
class Chilopoda The centipede group of animals.
class Diplopoda The millipede group of animals.

84. A collection of cell surface glycoproteins
encoded by a family of genes called the
major histocompatibility complex. In humans,
class I MHC molecules these glycoproteins are also known as the
HLA, human leukocyte antigens. Class I
MHC molecules are found on all nucleated
cells.
A collection of cell surface glycoproteins
encoded by a family of genes called the
major histocompatibility complex. In humans,
class II MHC molecules these glycoproteins are also known as the
HLA, human leukocyte antigens. Class II
MHC molecules are restricted to a few
specialized cell types.
A type of associative learning; the
classical conditioning association of a normally irrelevant stimulus
with a fixed behavioral response.
The process of cytokinesis in animal cells,
characterized by pinching of the plasma
membrane; specifically, the succession of
cleavage rapid cell divisions without growth during
early embryonic development that converts
the zygote into a ball of cells.
The first sign of cleavage in an animal cell; a
cleavage furrow shallow groove in the cell surface near the
old metaphase plate.

85. The prevailing weather conditions at a
climate locality.
Graded variation in some traits of individuals
cline that parallels a gradient in the environment.
An organ in the female that engorges with
clitoris blood and becomes erect during sexual
arousal.
A common opening for the digestive, urinary,
cloaca and reproductive tracts in all vertebrates
except most mammals.
The mechanism that determines specificity
and accounts for antigen memory in the
immune system; occurs because an antigen
clonal selection introduced into the body selectively activates
only a tiny fraction of inactive lymphocytes,
which proliferate to form a clone of effector
cells specific for the stimulating antigen.

86. (1) A lineage of genetically identical
individuals or cells. (2) In popular usage, a
single individual organism that is genetically
clone identical to another individual. (3) As a verb,
to make one or more genetic replicas of an
individual or cell. See also gene cloning.
Using a somatic cell from a multicellular
cloning organism to make one or more genetically
identical individuals.
An agent used to transfer DNA in genetic
engineering. A plasmid that moves
recombinant DNA from a test tube back into
cloning vector a cell is an example of a cloning vector, as is
a virus that transfers recombinant DNA by
infection.
Circulatory systems in which blood is
closed circulatory system confined to vessels and is kept separate
from the interstitial fluid.
The common name for members of the
club fungus phylum Basidiomycota. The name comes
from the clublike shape of the basidium.

87. Describing a dispersion pattern in which
clumped individuals are aggregate in patches.
A specialized cell for which the phylum
Cnidaria is named; consists of a capsule
cnidocyte containing a fine coiled thread, which, when
discharged, functions in defense and prey
capture.
The complex, coiled organ of hearing that
cochlea contains the organ of Corti.
A phenotypic situation in which the two
codominance alleles affect the phenotype in separate,
distinguishable ways.
A three-nucleotide sequence of DNA or
mRNA that specifies a particular amino acid
codon or termination signal; the basic unit of the
genetic code.

88. The probability that a particular gene present
in one individual will also be inherited from a
coefficient of relatedness common parent or ancestor in a second
individual.
A body cavity completely lined with
coelom mesoderm.
An animal whose body cavity is completely
lined by mesoderm, the layers of which
coelomate connect dorsally and ventrally to form
mesenteries.
Referring to a multinucleated condition
coenocytic resulting from the repeated division of nuclei
without cytoplasmic division.
An organic molecule serving as a cofactor.
coenzyme Most vitamins function as coenzymes in
important metabolic reactions.

89. The mutual influence on the evolution of two
different species interacting with each other
coevolution and reciprocally influencing each other's
adaptations.
Any nonprotein molecule or ion that is
required for the proper functioning of an
cofactor enzyme. Cofactors can be permanently
bound to the active site or may bind loosely
with the substrate during catalysis.
The ability of an animal's nervous system to
cognition perceive, store, process, and use information
obtained by its sensory receptors.
The scientific study of cognition; the study of
cognitive ethology the connection between data processing by
nervous systems and animal behavior.
A representation within the nervous system
cognitive map of spatial relations among objects in an
animal's environment.

90. The binding together of like molecules, often
cohesion by hydrogen bonds.
The idea that specific evolutionary
cohesion species concept adaptations and discrete complexes of
genes define species.
A group of individuals of the same age, from
cohort birth until all are dead.
The insertion of a penis into a vagina, also
coitus called sexual intercourse.
The covering of the young shoot of the
coleoptiles embryo of a grass seed

91. The covering of the young root of the embryo
coleorhizae of a grass seed.
A glycoprotein in the extracellular matrix of
animal cells that forms strong fibers, found
collagen extensively in connective tissue and bone;
the most abundant protein in the animal
kingdom.
Tough fibers of the extracellular matrix. They
collagenous fibers are made of collagen that are nonelastic and
do not tear easily when pulled lengthwise.
The location in the kidney where filtrate from
collecting duct renal tubules is collected; the filtrate is now
called urine.
A flexible plant cell type that occurs in
collenchymas cell strands or cylinders that support young parts
of the plant without restraining growth.

92. Adhesive structures on the tentacles of
colloblasts ctenophores.
The tubular portion of the vertebrate
alimentary tract between the small intestine
colon and the anus; functions mainly in water
absorption and the formation of feces.
The column shape of one type of epithelial
columnar cell.
A symbiotic relationship in which the
commensalism symbiont benefits but the host is neither
helped nor harmed.
All the organisms that inhabit a particular
area; an assemblage of populations of
community different species living close enough
together for potential interaction.

93. The study of how interactions between
community ethology species affect community structure and
organization.
A type of plant cell that is connected to a
sieve-tube cell by many plasmodesmata and
companion cell whose nucleus and ribosomes may serve
one or more adjacent sieve-tube cells.
Active demand by two or more organisms or
competition kinds of organisms for some environmental
resource in short supply.
The concept that when populations of two
similar species compete for the same limited
competitive exclusion resources, one population will use the
resources more efficiently and have a
principle reproductive advantage that will eventually
lead to the elimination of the other
population.
A substance that reduces the activity of an
competitive inhibitor enzyme by entering the active site in place of
the substrate whose structure it mimics.

94. A set of about 20 serum proteins that carry
complement out a cascade of steps leading to the lysis of
microbes.
An immune response in which antigen-
complement fixation antibody complexes activate complement
proteins.
A group of at least 20 blood proteins that
cooperate with other defense mechanisms;
may amplify the inflammatory response,
complement system enhance phagocytosis, or directly lyse
pathogens; activated by the onset of the
immune response or by surface antigens on
microorganisms or other foreign cells.
A DNA molecule made in vitro using mRNA
complementary DNA as a template and the enzyme reverse
transcriptase. A cDNA molecule therefore
(cDNA) corresponds to a gene, but lacks the introns
present in the DNA of the genome.
A digestive tube that runs between a mouth
and an anus; also called alimentary canal.
complete digestive tract An incomplete digestive tract has only one
opening.

95. A type of inheritance in which the
complete dominance phenotypes of the heterozygote and
dominant homozygote are indistinguishable.
A flower that has sepals, petals, stamens,
complete flower and carpels.
The transformation of a larva into an adult
that looks very different, and often functions
complete metamorphosis very differently in its environment, than the
larva.
A substance consisting of two or more
compound elements in a fixed ratio.
A type of multifaceted eye in insects and
crustaceans consisting of up to several
compound eye thousand light-detecting, focusing
ommatidia; especially good at detecting
movement.

96. A small molecule that cooperates with a
compressor repressor protein to switch an operon off.
An increase or decrease in the density of a
chemical substance in an area. Cells often
maintain concentration gradients of ions
across their membranes. When a gradient
concentration gradient exists, the ions or other chemical substances
involved tend to move from where they are
more concentrated to where they are less
concentrated.
conception The fertilization of the egg by a sperm cell.
A reaction in which two molecules become
covalently bonded to each other through the
condensation reaction loss of a small molecule, usually water; also
called dehydration reaction.
The direct transfer of thermal motion (heat)
conduction between molecules of objects in direct
contact with each other.

97. One of two types of photoreceptors in the
cone cell vertebrate eye; detects color during the day.
A characterization of an animal in regard to
environmental variables. The animal is a
conformer conformer if it allows some conditions within
its body to vary with certain external
changes.
(plural, conidia) A naked, asexual spore
conidium produced at the ends of hyphae in
ascomycetes.
A gymnosperm whose reproductive structure
conifer is the cone. Conifers include pines, firs,
redwoods, and other large trees.
The largest of the four gymnosperm phyla,
the reproductive structure is the cone.
Coniferophyta Conifers include pines, firs, redwoods, and
other large trees.

98. In bacteria, the direct transfer of DNA
conjugation between two cells that are temporarily
joined.
A mucous membrane that helps keep the
eye moist; lines the inner surface of the
conjunctiva eyelid and covers the front of the eyeball,
except the cornea.
Animal tissue that functions mainly to bind
and support other tissues, having a sparse
connective tissue population of cells scattered through an
extracellular matrix.
The group of ancient vertebrates that date
conodonts back as far as 510 million years.
A goal-oriented science that seeks to
conservation biology counter the biodiversity crisis, the current
rapid decrease in Earth's variety of life.