WBBSE Madhyamik Life Science (English Adaptation) key terms

A fast, automatic response to a stimulus that travels along a fixed nerve pathway without waiting for a decision from the brain, protecting the body from harm.

The complete route taken by a nerve impulse during a reflex: receptor, sensory neuron, spinal cord relay, motor neuron and effector muscle or gland.

The basic structural and functional unit of the nervous system, made of a cell body, dendrites and an axon, which carries electrical impulses through the body.

The tiny gap between two neurons across which a chemical transmitter diffuses so that an impulse can pass from one cell to the next in one direction only.

The largest, folded part of the brain, responsible for intelligence, memory, reasoning, voluntary movement and interpretation of sensations such as sight and hearing.

A chemical messenger secreted by an endocrine gland directly into the blood, which travels to a target organ and alters its activity slowly and for a long time.

A ductless gland such as the thyroid or adrenal that pours its secretion straight into the bloodstream instead of through a tube.

A hormone made by the beta cells of the pancreas that lowers blood glucose by helping cells absorb it and store it as glycogen; its shortage causes diabetes mellitus.

A self-correcting control system in which the level of a substance or effect feeds back to adjust the gland or organ producing it, keeping conditions steady within narrow limits.

Cell division in which one parent cell gives rise to two daughter cells with the same chromosome number and identical genetic content, used for growth and repair.

A reduction division producing four daughter cells, each with half the parent's chromosome number, so that gametes carry a single set before fertilisation.

A thread-like structure of DNA and protein found in the nucleus, carrying genes in a definite linear order and visible most clearly during cell division.

A segment of DNA at a particular position on a chromosome that codes for one trait or protein and is passed from parents to offspring.

One of the alternative forms of the same gene, such as the tall or dwarf form in pea plants, occupying the same position on homologous chromosomes.

The genetic make-up of an organism for a trait, written as the pair of alleles it carries, for example TT, Tt or tt.

The observable appearance or characteristic of an organism for a trait, which results from its genotype interacting with the environment.

Describing an organism whose two alleles for a trait are identical, such as TT or tt, so that it breeds true for that characteristic.

Describing an organism carrying two different alleles for a trait, such as Tt, so that the dominant allele alone shapes its appearance.

The characteristic that appears in a heterozygous individual because one allele masks the expression of the other, recessive allele.

A characteristic that stays hidden when a dominant allele is present and shows up only when both alleles are of the recessive kind.

The transmission of a trait whose gene lies on a sex chromosome, usually the X, so that its pattern of appearance differs between males and females.

A rare inherited disorder in which blood clots very slowly because a clotting factor is missing; the gene is recessive and carried on the X chromosome.

An inherited condition, commoner in males, in which a person cannot distinguish certain colours, especially red from green, because of a defective X-linked gene.

A hereditary blood disorder in which faulty haemoglobin is produced, causing anaemia; it is inherited when a child receives the defective gene from both parents.

Any inherited feature or behaviour that improves an organism's chance of surviving and reproducing in its particular habitat, built up over many generations.

The process by which individuals with favourable variations survive and leave more offspring, so those helpful traits become more common in later generations.

Structures in different species that share the same basic plan and origin but may perform different functions, indicating common ancestry, such as the forelimbs of humans and bats.

Structures that perform similar functions but differ in origin and structure, such as the wings of insects and birds, showing adaptation rather than close relationship.

A reduced, functionless structure left over from an ancestor in which it was well developed, such as the human appendix, giving evidence of evolution.

A self-regulating unit in which living organisms and their non-living surroundings interact and exchange energy and matter, for example a pond or a forest.

A linear sequence showing how energy passes from a producer to herbivores and then to successive carnivores, each stage forming a trophic level.

A network of interlinked food chains in a community that shows the many feeding relationships among organisms and makes the ecosystem more stable.

The circulation of a chemical element such as carbon, nitrogen or oxygen between the living and non-living parts of the biosphere, keeping nutrients available.

The variety of living species, their genetic differences and the ecosystems they form, which supports stability and is threatened by habitat loss and pollution.

The planned protection and wise management of natural resources and wildlife so that they remain available for future generations and ecosystems keep functioning.

The process by which green plants use light energy, carbon dioxide and water to make glucose and release oxygen, with chlorophyll acting as the trapping pigment.

The green pigment inside chloroplasts that absorbs light energy for photosynthesis and gives leaves their colour.

Tiny pores in the leaf surface, each bounded by two guard cells, through which gases are exchanged and water vapour escapes during transpiration.

A protein that speeds up one specific chemical reaction in living cells without being used up, such as amylase breaking starch into sugar.

The breakdown of large, insoluble food molecules into small, soluble ones that can be absorbed through the gut wall into the blood.

A greenish fluid made in the liver, stored in the gall bladder and poured into the small intestine, where it emulsifies fats and helps enzymes act on them.

One of many finger-like projections of the small intestine lining that increase the surface for absorbing digested food and contain blood capillaries and a lacteal.

The movement of digested, soluble food substances and water across the gut wall into the blood or lymph for transport around the body.

The loss of water as vapour from the aerial parts of a plant, mainly through stomata, which pulls water upward through the xylem in the transpiration stream.

A plant tissue of dead, hollow, lignified tubes that conducts water and dissolved minerals from the roots upward to the stem and leaves.

A living plant tissue of sieve tubes and companion cells that carries dissolved food made in the leaves to other parts of the plant.

The movement of soluble organic food, especially sucrose, through the phloem from leaves or storage organs to growing and respiring parts of the plant.

The red, iron-containing pigment of red blood cells that combines with oxygen in the lungs and releases it to tissues, giving blood its colour.

The enzyme-controlled release of energy from food, usually glucose, inside living cells, using oxygen in aerobic respiration and producing carbon dioxide and water.

The removal from the body of harmful nitrogenous waste products of metabolism, such as urea, together with excess water and salts.

The microscopic filtering and reabsorbing unit of the kidney, which turns blood plasma into urine through filtration and selective reabsorption.

The maintenance of a steady internal environment, such as constant body temperature, blood sugar and water balance, despite changes outside the body.

The active movement of an organism from one place to another, brought about by muscles pulling on a skeleton in response to nervous signals.

A place where two or more bones meet, held by ligaments, which may allow free movement as in the hinge of the elbow or none at all as in the skull.

A strong band of slightly elastic connective tissue that joins one bone to another at a joint and holds the bones in position.

A tough, inelastic cord of connective tissue that attaches a muscle to a bone so that muscle contraction can move the bone.

The way a bone acts as a lever, a joint as its fulcrum and a contracting muscle as the effort, allowing small muscle forces to move loads.

Any factor in an experiment that can change in value, such as temperature or light intensity; the one deliberately changed is the independent variable.

A parallel set-up that is treated exactly like the test set-up except for the factor under study, so that any difference can be credited to that factor.

A testable, reasoned statement predicting the relationship between variables, which an experiment is designed to support or reject with evidence.