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AbdomenA posterior segment of an animal that usually houses the organs of digestion and excretion.
AbioticNonliving or not containing any living organisms.
Abiotic factorsEnvironmental influences produced other than by living organisms; for example, temperature, wind patterns, humidity, pH, substrate rock type, and other physical and chemical influences.
AbomasumThe final compartment of the ruminant stomach,
also known as the fourth or true stomach of the cow, comparable in function to
the simple-stomached animals.
Aboral surfaceThe surface opposite the mouth on an echinoderm.
Abscisic acidA hormone in plants that helps regulate the growth of buds and
the germination of seeds.
Abscission zoneThe area at the base of a leaf petiole where the leaf breaks off
from the stem.
AbsorptionIn digestion, the movement of nutrients to the circulatory system.
Accessory pigmentA pigment that absorbs light energy and transfers energy to
chlorophyll a in photosynthesis.
AccipiterThe latin name for a genus of raptors, the short winged hawks of classic falconry, such as goshawks or cooper's.
AcclimationThe process of an organism’s adjustment to an abiotic factor.
Acclimatization
adjustment to altered environmental conditions.
Acid falloutMolecules of acid formed from reactions high in the atmosphere involving nitrogen, sulfur oxides, and water vapor that settle out of the atmosphere without any additional water.
Acid rainThe precipitation of sulfuric acid and other acids as rain. The acids form when sulfur dioxide and nitrogen oxides released during the combustion of fossil fuels combine with water and oxygen in the atmosphere.
AcneAn inflammatory disorder of the sebaceous glands characterized by skin
lesions in the form of pimples, blackheads, and sometimes cysts.
AcoelomateAn animal with no coelom, or body cavity.
Acre-foot
The volume of water that would cover one acre of land to a depth of one foot. An acre foot is the basic measure of agricultural water use.
ActinOne of the two protein filaments in a muscle cell that function in
contraction.
ActinomyceteA member of a class of bacteria characterized as rod-shaped monerans that form branched filaments.
Activation EnergyAmount of energy required for a chemical reaction to start
and to continue on its own.
Active TransportThe movement of a substance across a cell membrane against a
concentration gradient; requires the cell to expend energy.
AcyclovirAn antiviral drug.
AdaptationAn inherited trait that increases an organism’s chance of survival in a particular environment.
Adaptive RadiationAn evolutionary pattern in which many species evolve from
a single ancestral species.
AdenineA nitrogen-containing base that is a component of a nucleotide.
Adenosine Diphosphate (ADP)A substance involved in energy metabolism formed by the breakdown of adenosine triphosphate.
Adenosine Triphosphate (ATP)A molecule present in all living cells and acting as an energy source for metabolic processes.
AdhesionThe attractive force between unlike substances.
Adrenal GlandAn endocrine gland located on the top of a kidney.
Adrenaline EpinephrineA hormone secreted by the adrenal medulla that raises
the level of glucose in the blood, increases the heartbeat, and raises blood
pressure.
Adrenocorticotropic HormoneA hormone that stimulates the adrenal cortex.
AerobeAn organism that utilizes atmospheric oxygen in its metabolic pathways.
Aerobic RespirationThe process in which cells make ATP by breaking down
organic compounds, with oxygen as the final electron acceptor.
Afferent NeuronA neuron that conducts impulses toward the central nervous system.
AflatoxinToxin produced by the fungi Aspergillus flavus
and Aspergillus parasiticus.
Aflatoxin A crop damaging carcinogen that is produced by mold in stored crops. It is prominent in crops that are stored while still moist.
AfterbirthThe remains of the placenta and the amnion, expelled from the mother’s body following birth.
AgarA gel-like base for culturing microbes; extracted from the cell walls of red algae.
Age StructureThe distribution of individuals among different ages in a population.
Agenda 21The international policy agreed on at the Rio Conference in 1992. Under Agenda 21, countries agreed to work towards sustainable social, economic and environmental development.
AgribusinessThe combination of the producing operations of a farm, the manufacture and distribution of farm equipment and supplies and the processing, storage, and distribution of farm commodities.
Agricultural DiversificationAgricultural diversification refers to a shift from one particular cropping system to a varied and multi-cropping system to stabilized farm income (particularlyon small farm holdings) and protects our natural resources.
Agricultural Pollution Wastes, emissions, and discharges arising from farming activities. Causes include runoff and leaching of pesticides and fertilizers; pesticide drift and volatilization; erosion and dust from cultivation; and improper disposal of animal manure and carcasses.
AgricultureThe art and science of producing crops, raising livestock and their preparation and marketing for use by the human beings.
Agriculture EconomyAn economic system based primarily on crop production.
Agriculture Land Agricultural land is land including arable land, land under permanent crops and land under permanent meadows and pastures.
Agriculture PricesIt is the exchange value of agricultural commodity, determined by buyers and sellers in the market and is expressed in terms of money.
Agro-forestryProduction of tree crops in a manner similar to agriculture. Also production of trees along with regular crops.
AgronomicAn adjective used to describe plants and plant products. Pertains to agronomy or agricultural plants and things affecting plants.
AgronomyThe science of crop production and soil management.
AI = artificial inseminationThe technique that involves breeding of females without
the males being physically present.
Alcoholic FermentationThe process by which pyruvic acid is converted to ethyl alcohol; the anaerobic action of yeast on sugars.
AlcoholismThe disease of addiction to ethanol.
AldosteroneA hormone that helps maintain water and salt balance.
AlgaeAutotrophic protists.
Alien speciesA species occurring in an area outside of its historically known natural range as a result of intentional or accidental dispersal by human activities (also known as an exotic or introduced species).
AllantoisIn amniotic eggs, the membranous sac that contains many blood vessels; in humans, a membrane surrounding the embryo that becomes the umbilical cord.
AlleleAn alternative form of a gene.
Allele FrequencyThe percentage of an allele in a gene pool.
AllergenA usually harmless antigen in the environment that is capable of
inducing an allergic reaction.
AllergyImmune reaction to an allergen.
All-in all-out systemsA livestock management system in which all
animals are introduced into an isolated confinement unit, taken through the
appropriate stage of the production cycle and all moved out at the same time.
The unit is then cleaned thoroughly and disinfected before a new group comes in.
Alternative AgricultureAgriculture based on reduced use of chemical fertilizers and pesticides, increased use of crop rotation, enhance sustainability, improve efficiency and profitability and reduce tillage of soil.
Alternative CropsNon-traditional crops that can be in an area to diversity rotations, and increase income.
AltricialReferring to birds that, at hatching, are immature and in need of parental
care.
Altruistic BehaviorSacrifice by one individual that results in a benefit for
another individual.
AlveolusOne of the tiny air sacs found in the lungs.
ambient air
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The air immediately around us. |
Amebic DysenteryA sometimes fatal disease caused by an amoeba that enters the body in contaminated food or water.
AmebocyteIn sponges, an amoebalike cell that moves through the body cells, supplying nutrients, removing wastes, and transporting sperm during sexual reproduction.
Amino AcidA carboxylic acid with an amino group; one of 20 monomers that form proteins.
Amino Acid–Based HormonesAgroup of hormones that includes proteins, peptides, amino acids, and other forms derived from amino acids.
AmmonificationIn the nitrogen cycle, the formation of ammonia compounds.
AmniocentesisA procedure used in fetal diagnosis in which fetal cells are removed from the amniotic fluid.
AmpullaA bulblike sac at the base of the tube foot of an echinoderm that functions in movement.
AnaerobeAn organism capable of living in the absence of free oxygen.
Anal PoreIn protozoa, an opening from which wastes are eliminated.
Analogous StructureIn evolution, structures in more than one organism that have similar appearance and function, but different embryological origin.
AnaphaseA phase of mitosis and meiosis in which the chromosomes separate.
Anatomy Anatomy is the study of the structure of organisms.
AndrogenA hormone secreted by the testes that controls secondary sex characteristics.
AngiospermA flowering plant.
AnnelidA bilaterally symmetrical, segmented worm, such as an earthworm or a leech.
Annual Any plant which completes its entire life cycles and dies within one year or less.
Annual RingA yearly growth ring in a woody plant.
AnteriorThe front end of a bilaterally symmetrical organism.
AntherThe microsporangium of an angiosperm in which pollen grains are produced.
AntheridiumIn plants, algae, and fungi a reproductive structure that produces gametes by mitosis.
anthropocentric
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The belief that humans hold a special place in nature, being centered primarily on humans and human affairs. |
Anthropoid PrimateOne of a subgroup of primates that includes monkeys and apes.
AntibioticA chemical that can inhibit the growth of some bacteria.
AntibodyA protein produced by B cells that binds to antigens.
AnticodonA region of tRNA consisting of three bases complementary to the codon of mRNA.
Antidiuretic HormoneA hormone that helps regulate solute concentration in the blood.
AntigenA substance that stimulates an immune response.
AortaThe largest artery in the human body; carries blood from the left ventricle to systemic circulation.
Aortic ValveThe semilunar valve on the left side of the heart.
Aphotic ZoneThe ocean layer that receives no light.
Apical DominanceA plant growth pattern in which branches near the shoot tip are shorter than branches farther from the shoot tip.
Apical MeristemThe growing region at the tips of stems and roots in plants.
AppendageAny complex part or organ extending from the body.
Appendicular SkeletonIn vertebrates, the bones that form the limbs.
AquiferAn underground geological formation, or group of formations, containing usable amounts of groundwater that can supply wells or springs for domestic, industrial, and irrigation uses.
Aquifer DepletionDepletion of water of an aquifer resulting from withdrawal that is greater than natural or artificial recharge.
Arable landLand that can be cultivated
ArachnidAn arthropod with four pairs of walking legs; a spider, scorpion, mite, or tick.
Arachnoid MembraneThe middle layer of the three sacs that surround the brain and spinal cord.
ArchaebacteriumA prokaryotic organism distinguished from other prokaryotes by the composition of the cell membranes and walls.
ArchegoniumIn seedless plants, a reproductive structure that produces a single egg by mitosis.
Arid Climate A dry climate with an annual precipitation usually less than 10 inches and the level of evaporation is greater than the level of precipitation. It is not suitable for crop production without irrigation.
ArterioleA branch of an artery that gives rise to capillaries.
ArteryA vessel that carries blood away from the heart to the body’s organs.
Arthropod SegmentedAnimal with jointed appendages and an exoskeleton.
Artificial FertilizerA chemical added to soil to enhance crop production.
Artificial SelectionBreeding of organisms by humans for specific phenotypic characteristics.
AscocarpThe fruiting body of an ascomycete.
AscogoniumA gamete-producing structure in ascomycetes.
AscosporeOne of eight haploid cells in an ascus.
AscusA spore sac that forms on the surface of an ascocarp.
Asexual reproductionA method of reproduction in which genetically identical offspring are produced from a single parent; occurs by many mechanisms, including fission, budding, and fragmentation.
Asexual ReproductionThe production of offspring that does not involve the union of gametes.
AssemblageAn integrated group of species inhabiting a given area; the organisms within a community influence one another's distribution, abundance, and evolution. (A Human Community is a social group of any size whose members reside in a specific locality.)
Asteroid-Impact HypothesisThe hypothesis that the extinction of the dinosaurs was caused by the impact of a huge asteroid.
AsthmaA chronic respiratory condition characterized by recurring attacks of wheezing, coughing, and labored breathing.
AtherosclerosisA disease characterized by the buildup of fatty materials on the interior walls of the arteries.
AtmosphereThe mass of air surrounding the Earth.
AtomThe simplest particle of an element that retains all the properties of that element.
Atomic NumberThe number of protons in an atom.
ATP SynthaseAn enzyme that catalyzes the synthesis of ATP from ADP and phosphate.
Atrioventricular NodeA group of nerves in the heart that functions in the heartbeat.
Atrioventricular ValveA one-way valve separating each atrium from the ventricle beneath it.
AtriumAn anterior chamber of the heart.
Attenuated StrainRefers to a preparation of a virus for a vaccine in which the virus is incapable of causing disease under normal circumstances.
Auditory CanalThe tube through which air enters the ear.
AustralopithecineEarly hominid from the genus australopithecus.
Autoimmune DiseaseA disorder in which the immune system attacks the organism’s own cells.
Autonomic Nervous SystemA division of the peripheral nervous system that controls the involuntary actions that regulate the body’s internal environment.
AutosomeA chromosome that is not a sex chromosome.
AutotomyThe ability of an organism to deliberately drop a body part, most often to escape a predator.
AutotrophAn organism that uses energy to synthesize organic molecules from inorganic substances.
AutotrophLiterally, "self eater." Organisms capable of producing their own food.
AuxinA plant hormone that regulates cell elongation.
AvianThe class of animals that exclusively includes birds
Axial SkeletonThe backbone, skull, and associated bones of vertebrates.
AxonIn a neuron, an elongated extension that carries impulses away from the cell body.
Azidothymidine (AZT)An antiviral drug that inhibits the reverse transcriptase of retroviruses, such as HIV.