NSSCO Biology 6116 key terms

The factor that a scientist deliberately changes or selects in an experiment so that its effect on the measured result can be investigated.

The factor that is measured or counted in an experiment; it is expected to respond to changes made to the independent variable.

A factor that is kept the same across all trials or specimens in an experiment so that it cannot explain differences in the results.

How consistently repeated measurements or trials give similar results; reliable data are more trustworthy because random variation has less influence.

How close a measured value is to the true value; accuracy improves when instruments are calibrated and readings are taken carefully.

The net movement of particles from a region of higher concentration to a region of lower concentration, caused by random motion, without energy input from the cell.

The net movement of water molecules through a partially permeable membrane from a dilute solution to a more concentrated solution, down a water potential gradient.

Movement of substances across a cell membrane against a concentration gradient using energy released by respiration, usually with the help of carrier proteins.

A type of nuclear division that produces two genetically identical daughter cells with the same chromosome number as the parent cell; it supports growth and repair.

A protein that speeds up a specific chemical reaction by lowering its activation energy; enzymes are biological catalysts and are affected by temperature and pH.

The process in chloroplasts where green plants use light energy to convert carbon dioxide and water into glucose and oxygen, with chlorophyll absorbing the light.

A condition, such as light intensity, carbon dioxide concentration or temperature, that is in shortest supply and therefore restricts the rate of photosynthesis.

A diet containing all the nutrients needed in suitable amounts, including carbohydrates, proteins, fats, vitamins, minerals, fibre and water, to maintain health.

Rhythmic waves of muscular contraction in the walls of the alimentary canal that push food along and help mix it with digestive juices.

The release of energy from glucose using oxygen, producing carbon dioxide and water; it occurs mainly in mitochondria and yields more energy than anaerobic respiration.

Release of energy from glucose without oxygen; in human muscle it produces lactic acid, and in yeast it produces ethanol and carbon dioxide.

A tiny air sac in the lungs where gas exchange occurs; its thin, moist wall and rich blood supply allow oxygen and carbon dioxide to diffuse quickly.

Small pores mainly on the lower surface of leaves that open and close to allow carbon dioxide in and oxygen and water vapour out.

The loss of water vapour from plant leaves through stomata, creating a pulling force that helps draw water and dissolved minerals up the xylem.

The movement of dissolved sugars and other organic substances through the phloem from sources where they are made to sinks where they are used or stored.

A blood vessel that carries blood away from the heart; arteries have thick elastic muscular walls and narrow lumens to withstand high pressure.

A very narrow blood vessel with a thin wall, linking arteries and veins; its large surface area allows rapid exchange of substances with tissues.

The maintenance of a stable internal environment within narrow limits, despite changes outside the body, through coordinated nervous and hormonal responses.

A control mechanism in which a change from the normal level triggers a response that reduces the change and brings conditions back toward the set point.

The microscopic filtering unit of the kidney; it filters blood, reabsorbs useful substances and secretes wastes to produce urine.

A rapid, automatic response to a stimulus that does not require conscious thought, protecting the body from harm; it involves a reflex arc.

A junction between two neurones, or between a neurone and an effector, where a chemical neurotransmitter carries the impulse across a small gap.

A chemical messenger produced by an endocrine gland and transported in the blood to target organs, where it alters their activity.

A growth response of a plant shoot toward light, caused by auxin redistributing to the shaded side and stimulating greater cell elongation there.

The transfer of pollen from the anther of a flower to the stigma, either within the same flower or between different flowers, enabling fertilisation.

The fusion of a male gamete nucleus with a female gamete nucleus to form a zygote, restoring the diploid chromosome number in the new cell.

A reduction division that produces four daughter cells, each with half the chromosome number of the parent; it forms gametes and creates genetic variation.

One of the different versions of a gene that can occupy the same position on a chromosome and may produce different characteristics.

The process in which individuals with inherited features better suited to their environment survive and reproduce more, so those features become more common.

A community of interacting organisms together with the non-living parts of their environment, such as soil, water, air and sunlight.

An organism that makes its own food by photosynthesis, forming the starting point of a food chain and supplying energy to other organisms.

Nutrient enrichment of water, often by fertiliser runoff, causing rapid algal growth; decomposition then uses up oxygen and can kill aquatic animals.

The series of processes by which carbon moves between the atmosphere, living organisms, soil, oceans and fossil fuels, including photosynthesis, respiration and combustion.