Definitions IGCSE Biology Flashcards
movement
an action by an organism or part of an organism causing a change in position or place
respiration
the chemical reactions in cells that break down nutrient molecules and release energy for metabolism
sensitivity
the ability to detect or sense stimuli in the internal or external environment and to make appropriate responses
growth
a permanent increase in size and dry mass by an increase in cell number or cell size or both
reproduction
the processes that make more of the same kind of organism
excretion
removal from organisms of the waste products of metabolism (chemical reactions in cells including respiration), toxic materials and substances in excess of requirements
nutrition
taking in of materials for energy, growth and development; plants require light, carbon dioxide, water and ions; animals need organic compounds and ions and usually need water
species
a group of organisms that can reproduce to produce fertile offspring
binomial system (of naming species)
an internationally agreed system in which the scientific name of an organism is made up of two parts showing the genus and species
tissue
a group of cells with similar structures, working together to perform a shared function
organ
a structure made up of a group of tissues, working together to perform specific functions
organ system
a group of organs with related functions, working together to perform body functions
diffusion
the net movement of particles from a region of their higher concentration of a region of their lower concentration down a concentration gradient, as a result of their random movement
osmosis
the net movement of water molecules from a region of higher water potential to a region of lower water potential, through a partially permeable membrane
active transport
the movement of particles through a cell membrane from a region of lower concentration to a region of higher concentration using energy from respiration
catalyst
a substance that increases the rate of a chemical reaction and is not changed by the reaction
enzymes
proteins that function as biological catalysts
photosynthesis
the process by which plants manufacture carbohydrates from raw materials using energy from light
limiting factor
something present in the environment in such short supply that it restricts life processes
ingestion
the taking of substances into the body through the mouth
mechanical digestion
the breakdown of food into smaller pieces without chemical change to the food molecules
chemical digestion
the breakdown of large, insoluble molecules into small. soluble molecules
absorption
the movement of small food molecules and ions through the wall of the intestine into the blood
assimilation
the movement of digested food molecules into the cells of the body where they are used, becoming part of the cells
egestion
the passing out of food that has not been digested or absorbed, as faeces, through the anus
transpiration
loss of water vapour from plant leaves by evaporation of water at the surfaces of mesophyll cells followed by diffusion of water vapour through the stomata
translocation
the movement of sucrose and amino acids from regions of productions (source- leaves) to regions of storage or regions where they are used in respiration or growth (sink)
pathogen
a disease causing organism
transmissible disease
a disease in which the pathogen can be passed from one host to another
active immunity
defence against a pathogen by antibody production in the body
aerobic respiration
the chemical reactions in cells that use oxygen to break down nutrient molecules to release energy
anaerobic respiration
the chemical reactions in cells that break down nutrient molecules to release energy without using oxygen