C3 Plant

A plant that fixes carbon exclusively through the Calvin cycle, named for the three-carbon compound that is initially formed.

C4 Plant

A plant that incorporates CO2 into four-carbon compounds.


A hormone that stimulates removal of calcium from the blood.

Calvin Cycle

A biochemical pathway of photosynthesis in which CO2 is converted into carbohydrate.


Crassulacean acid metabolism; a biochemical pathway in certain plants in which CO2 is incorporated into organic acids at night and released for fixation in the Calvin cycle during the day.


Layers of treetops that shade the forest floor.

Capacity Building

The improvement of an organization’s or community’s ability to perform its tasks effectively and confidently. It may include skills training, organizational development and financial resources.


The reaction of a liquid surface with a solid; capillarity allows water to creep up the interior of a narrow vessel.


The protein covering a virus.


In mosses, a sporangium that produces spores; in bacteria, a protective layer of polysaccharides around the cell wall.

Captive breeding

The propagation or preservation of animals outside their natural habitat, involving control by humans of the animals chosen to constitute a population and of mating choices within that population.


A substance found in the cell walls of red algae that is used commercially as a smoothing agent.


A tough covering over the cephalothorax of some crustaceans; the dorsal part of a turtle’s shell.


An organic compound present in the cells of all living things and a major organic nutrient for humans.

Carbon Cycle

Process in which carbon is cycled through the biosphere.

Carbon Fixation

The incorporation of carbon dioxide into organic compounds.


A cancer-causing substance.


Any substance that produces or promotes cancer. This is a key consideration in evaluating the safety of pesticides and other chemicals

Cardiac Muscle

The involuntary muscle of the heart.

Cardiac Sphincter

A circular muscle located between the esophagus and the stomach.

Cardiac Stomach

In an echinoderm, the stomach closer to the mouth.

CardioVascular System

The blood, the heart, and the blood vessels.


A consumer that eats other consumers.


Macro organisms that feed on other animals.


A light-absorbing compound that functions as an accessory pigment in photosynthesis.

Carrier Protein

A protein that transports specific substances across a biological membrane.

Carrying capacity

The maximum number of individuals of a particular species, that a given part of the environment can maintain indefinitely. Also called biological carrying capacity.

Carrying Capacity

The number of individuals of a species that an ecosystem is capable of supporting.


A strong, flexible connective tissue.

Cash crop

Crop grown for cash rather than retained for household that brings money immediately, like cotton, potato and tobacco  etc.



A type of fossil formed when sediments fill in the cavity left by a decomposing organism.


A chemical that reduces the amount of activation energy needed for a reaction but is not a reactant.

Caudal Fin

In fishes, a fin extending from the tail that moves from side to side and amplifies the swimming motions.

Cause and Effect

A relationship between two variables in which a change in one variable leads to a change in the other.


A sac usually found at the beginning of the large intestine.


A membrane-bound structure that is the basic unit of life.

Cell Cycle

The events of cell division; includes interphase, mitosis, and cytokinesis.

Cell Differentiation

The change in morphology, physiology, or function of a cell in relation to its neighboring cells.

Cell Junction

Connection between cells that holds them together as a unit.

Cell Membrane

The lipid bilayer that forms the outer boundary of a cell.

Cell Plate

A membrane that divides newly forming plant cells following mitosis.

Cell Theory

The theory that all living things are made up of cells, that cells are the basic units of organisms, and that cells come only from existing cells.

Cell Wall

A rigid structure that surrounds the cells of plants, fungi, many protists, and most bacteria.

Cell-Mediated Response

Part of an immune response involving a T-cell attack on an antigen.

Cellular Slime Mold

Individual haploid cells that move about like amoebas; member of the phylum Acrasiomycota.

Centers of diversity

The regions where most of the major crop species were originally domesticated and developed. These regions may coincide with centers of origin.

Central Nervous System

The brain and the spinal cord.


A structure that appears during mitosis in animal cells.


A region of the chromosome where the two sister chromatids are held together and which is the site of attachment of the chromosome to the spindle fibers during mitosis.


A dark body containing a centriole in animal cells but not in plant cells; spindle fibers radiate from the centrosome in preparation for mitosis.


Concentration of nerve tissue and sensory organs at the anterior end of an organism.


A free-swimming, predatory mollusk with a circle of tentacles extending from the head; an octopus, squid, cuttlefish, or chambered nautilus.


In arachnids and some crustaceans, a body part formed by the fusion of the head with the thorax.


A posterior portion of the brain that controls movement and muscle coordination.

Cerebral Cortex

The folded outer layer of the cerebrum that controls motor and sensory activities.

Cerebral Ganglion

One of a pair of nerve-cell clusters that serve as a brain at the anterior end of some invertebrates.

Cerebrospinal Fluid

A watery substance that provides a cushion that protects the brain and spinal cord.


The anterior portion of the brain where higher brain functions occur.

Character Displacement

Evolution of anatomical differences that reduce competition between similar species.


A pincerlike mouthpart of some arthropods.


In arthropods, a claw used to capture food and for defense.


An element or compound naturally occurring or created by humans.

Chemical Bond

A chemical attachment between atoms.

Chemical Reaction

The process of breaking chemical bonds, forming new bonds, or both.


The application of a pesticide and/or fertilizer through any irrigation system


A process in chloroplasts and mitochondria in which the movement of protons down their concentration gradient across a membrane is coupled to the synthesis of ATP.


An organism that synthesizes organic compounds using chemicals instead of light.


The production of carbohydrates through the use of energy from inorganic molecules instead of light.


Plant growth in response to a chemical.


A farm implement used to break through and shatter compacted or otherwise impermeable layers of soil.


A carbohydrate that forms part of the arthropod exoskeleton.

Chlorofluorocarbons (CFCs)

 A class of industrial chemicals found to be destroying the ozone layer in the upper atmosphere


A class of light-absorbing pigments used in photosynthesis.


A plastid containing chlorophyll; the site of photosynthesis.


The outer membrane surrounding an embryo.

Chorionic Villi

Fingerlike projections of the chorion that extend into the uterine lining.


One of two identical parts of a chromosome.


The DNA and proteins in the nucleus of a non dividing cell.


DNA and protein in a coiled, rod-shaped form that occurs during cell division.

Chromosome Map

A diagram of allele positions on a chromosome.

Chronic Bronchitis

An inflammation of the bronchi and bronchioles.


The outer covering of a butterfly pupa.


The mixture formed in the stomach from digested food particles and gastric fluid.


An aquatic protist characterized by gametes and zoospores with a single, posterior flagellum.


A short, hairlike organelle that extends from a cell and functions in locomotion or in the movement of substances across the cell surface.

Circulatory System

The system that distributes oxygen and nutrients to cells in all parts of the body.


A condition in which normal liver tissues are replaced by scar tissue.


In fishes, a structure that transfers sperm into the female’s body.


The divisions of the zygote immediately following fertilization.

Cleavage Furrow

The area of the cell membrane that pinches in and eventually separates the dividing cell.


The long term average of weather conditions in an area.


Climate Change

A change which is attributed directly or indirectly to human activity that alters the composition of the global atmosphere. The build-up of manmade gases in the atmosphere traps the suns heat, causing changes in weather patterns on a global scale. The effects include changes in rainfall patterns, sea level rise, potential droughts, habitat loss and heat stress.

Climatic (thermal) stimulusChanges in temperature or other weather related factors that cause a response.

Climax community

The end of a successional sequence; a community that has reached stability under a particular set of environmental conditions.

Closed Circulatory System

A system in which blood is contained within vessels as in the human circulatory system.


A phylum of animals with radially symmetrical bodies, a saclike internal cavity, tentacles, and nematocysts, such as jellyfish, hydras, sea anemones, and corals.


A cell-like droplet formed from dissimilar substances.


The attraction of like molecules to each other.

Cohesion-Tension Theory

States that water is able to move up the stem xylem due to the strong attraction of water molecules to each other.

Collar Cell

A cell lining the inside of sponges that circulates water; also called a choanocyte.


Plant tissue made up of elongated cells with unevenly thickened, flexible walls.


The management of a specific resource (such as a forest or pasture) by a well-defined group of resource users with the authority to regulate its use by members and outsiders.


A self-propelled or tractor-drawn machine which cuts, threshes, and cleans the standing crop which moving across the field. It is adapted to harvesting all the small grains, soybeans, grain sorghums, peanuts, beans, etc. In some areas, the crop is cut and placed in windrows by a swather (windrower), and a combine with a pickup attachment gathers the grain and threshes it at a later date.


Common property resource management

The management of a specific resource (such as a forest or pasture) by a well-defined group of resource users with the authority to regulate its use by members and outsiders.


A group of ecologically related populations of various species of organisms occurring in a particular place and time.


All the populations in one area.


The concept of achieving conservation efficiently by ensuring that a set of areas is assembled with due regard to the additional species that each brings into the network. This is the basis of a critical faunal analysis.


Organic residues, or a mixture of organic residues and soil, which have been piled, moistened, and allowed to undergo biological decomposition for use as a fertilizer.

Concentration Concentration

A measurement of the amount of solute dissolved in a fixed amount of solvent.

Concentration Gradient

The difference in concentration of a substance across space.

Condensation Reaction

A chemical reaction, also called dehydration synthesis, in which one molecule of water is produced.


A photoreceptor within the retina that can produce sharp images and distinguish colors; in gymnosperms, a seed-bearing structure.


An organism that does not regulate its internal environment.


A spore produced during asexual reproduction in ascomycetes


The union of two protists to exchange genetic material.

Conjugation Bridge

In certain algae and fungi, a passageway for the transfer of the genetic information from one organism to another.


The management of human and natural resources to provide maximum benefits over a sustained period of time. In farming, conservation entails matching cropping patterns and the productive potential and physical limitations of agricultural lands to ensure long-term sustainability of profitable production. Conservation practices focus on conserving soil, water, energy, and biological resources. Contour farming, no-till farming, and integrated pest management are typical examples of conservation practices.


The management of human use of the biosphere so that it may yield the greatest sustainable benefit to current generations while maintaining its potential to meet the needs and aspirations of future generations.

Conservation Biology

A branch of biology concerned with preserving biodiversity in natural areas.

Conservation of Biodiversity

The management of human interactions with genes, species, and ecosystems so as to provide the maximum benefit to the present generation while maintaining their potential to meet the needs and aspirations of future generations; encompasses elements of saving, studying, and using biodiversity.

Conservation Practice

Any technique or measure used to protect soil and water resources for which standards and specifications for installation, operation, or maintenance have been developed. Practices approved by the Natural Resources Conservation Service are compiled at each conservation district in its field office technical guide.

Conservation Tillage

Any of several farming methods that provide for seed germination, plant growth and weed control yet maintain effective ground cover throughout the years and disturb the soil as little as possible. No-till is the most restrictive form of conservation tillage. Other practices include ridge-till, strip-till, and mulch-till.

Conservation-tillage farming

Crop cultivation in which the soil is disturbed little (minimum-tillage farming) or not at all (no-till farming) to reduce soil erosion, lower labor costs, and save energy.


A heterotroph that obtains energy from organic molecules made by other organisms.


Polluting or making something impure.

Contour farming

Field operations such as plowing, planting, cultivating, and harvesting on the contour, or at right angles to the natural slope to reduce soil erosion, protect soil fertility, and use water more efficiently.

Contour Feather

A feather that provides coloration, insulation, and a streamlined shape to adult birds.

Contract Crops

Specific crops eligible for production flexibility payments: wheat, corn, sorghum, barley, oats, rice and upland cotton.

Contract farming

Contract farming is defined as a system for the production and supply of agricultural/horticultural produce under forward contracts between producers/suppliers and buyers. The essence of such an arrangement is the commitment of the producer/ seller to provide an agricultural commodity of a certain type, at a time and a price, and in the quantity required by a known and committed buyer.

Contractile Vacuole

An organelle in protists that expels water.

Control Group

In an experiment, a group or individual that serves as a standard of comparison with another group or individual to which it is identical except for one factor.

Controlled Experiment

A test of variables using a comparison of a control group with an experimental group.

Conus Arteriosus

In fishes and frogs, the final chamber of the heart.

Convection Cell

A regional pattern of rising and falling air.

Conventional agriculture

Generally used to contrast common or traditional agricultural practices featuring heavy reliance on chemical and energy inputs typical of large-scale, mechanized farms to alternative agriculture or sustainable agriculture practices.


Convergent Evolution

The process by which unrelated species become more similar as they adapt to the same kind of environment.

Coral bleaching

The loss of color from a coral as it expels its zooxanthellae-usually a stress response.

Coral Reef

A rocklike formation in warm, shallow seas composed of the skeletons of corals.

Cork Cambium

The lateral meristem of a plant; produces cork.


A relationship between two variables in which both variables change together.


In plants, a mature ground tissue located just inside the epidermis; inanimals, the outermost portion of an organ such as the kidney.


A hormone that regulates certain phases of carbohydrate and protein metabolism.

Cost-benefit analysis

Estimates and comparison of short-term and long-term costs (losses) and benefits (gains) from an economic decision. If the estimated benefits exceed the estimated costs, the decision to buy an economic good or provide a public good is considered worthwhile.


A seed leaf in a plant embryo.

Countercurrent Flow

 In gills of fishes, an arrangement whereby water flows away from the head and blood flows toward the head.

Country of origin of genetic resources

The country which possesses those genetic resources in in-situ conditions.

Country providing genetic resources

The country supplying genetic resources collected from in-situ sources, including populations of both wild and domesticated species, or taken from ex-situ sources, which may or may not have originated in that country

Covalent Bond

A bond that forms when two atoms share one or more pairs of electrons.

Cover crops

The leguminous pulses grown at or in advance of the monsoon period in between trees rows to cover the soil from erosion or to draw surplus moisture off e.g. cowpea, ground nut, moong and moth are good cover crops.

Coxal Gland

In some arachnids, an organ that removes wastes and discharges them at the base of the legs.

Cranial Cavity

The area in which the brain rests.

Cranial Nerve

One of the 12 nerves of the head that relay information between the brain and the muscular and sensory structures in the head.


A form of mental retardation caused by hypothyroidism.


A fold of the inner membrane of mitochondria.

Critical faunal analysis

A methodology to identify the minimum set of areas which would contain at least one viable population of every species in a given animal or plant group.

Critical habitat

A technical classification of areas in the United States that refers to habitats essential for the conservation of endangered or threatened species. The term may be used to designate portions of habitat areas, the entire area, or even areas outside the current range of the species.


In earthworms, a structure that stores soil; in birds, a structure that stores food.

Crop Milk

A nutritious milklike fluid secreted by the crop of pigeons and doves to feed their young.

Crop residue

That portion of a plant, such as a corn stalk, left in the field after harvest. ?

Crop Rotation

The practice of growing different crops in recurring succession on the same land, to reduce nutrient depletion of the soil and reliance on pesticides.

Cropping intensity

Cropping intensity refers to the number of crops grown per annum an a given area of land multiplied by hundred

Cropping Pattern

It is the proportion of the area under various crops at a point of time


The exchange of genes by reciprocal segments of homologous chromosomes during meiosis.


A reproductive process in which pollen from one plant is transferred to the stigma of another plant.


An arthropod with mandibles and branched appendages; examples include shrimps, barnacles, crabs, and pill bugs.


A type of lichen that grows as a layer on rocks and trees.


A combination of the words cultivated and variety for a food plant that has a specific distinguishing characteristic, such as Thompson Seedless grapes.


A cultivated variety (genetic strain) of a domesticated crop plant.


A machine used to till the upper portion of the soil, primarily used to destroy weeds or form a moisture retaining mulch

Cultural diversity

Variety or multiformity of human social structures, belief systems, and strategies for adapting to situations in different parts of the world.

Cutaneous Respiration

In some animals, the exchange of gases through the skin.


Plant piece (stem, leaf, or root) removed from a parent plant that is capable of developing into a new plant.


Any of an order of gymnosperms of the family cycadaceae. Cycads are tropical plants that resemble palms but reproduce by means of spermatozoids.


A resistant, thick-walled structure that encloses and protects a dormant organism.


A chemical signal between cells of the immune system.


The division of the cytoplasm of one cell into two new cells.


Plant hormones that promote cell division.


The bursting of a cell.


The region of a cell between the cell membrane and the nucleus.

Cytoplasmic Streaming

The circular motion of the cytoplasm.


A nitrogen-containing base; a pyrimidine of DNA and RNA.


A network of long protein strands in the cytosol that helps maintain the shape and size of a eukaryotic cell.


The gelatinlike aqueous fluid that bathes the organelles on the inside of the cell membrane.

Cytotoxic T cell

A type of T cell that destroys infected body cells.