69 terms

IGCSE biology syllabus terms

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movement
an action by an organism or part of an organism causing a change of 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
group of organisms that can reproduce to produce fertile offspring
binomial system (of naming species)
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
inheritance
the transmission of genetic information from generation to generation
chromosomes
thread-like structure of DNA, carrying genetic information in the form of genes
gene
length of DNA that codes for a protein
allele
a version of a gene
haploid nucleus
a nucleus containing a single set of unpaired chromosomes, e.g. in gametes
diploid nucleus
a nucleus containing two sets of chromosomes, e.g. in body cells
mitosis
nuclear division giving rise to genetically identical cells
meiosis
reduction division in which the chromosome number is halved from diploid to haploid resulting in genetically different cells
genotype
the genetic make-up of an organism in terms of the alleles present
phenotype
the observable features of an organism
homozygous
having two identical alleles of a particular gene
heterozygous
having two different alleles of a particular gene
dominant
an allele that is expressed if it is present
recessive
an allele that is only expressed when there is no dominant allele of the gene present
sex-linked characteristic
a characteristic in which the gene responsible is located on a sex chromosome and that this makes it more common in one sex than in the other
stem cells
unspecialised cells that divide by mitosis to produce daughter cells that can become specialised for specific functions
codominance
two alleles are equally expressed in the phenotype of a heterozygous individual
genetic engineering
changing the genetic material of an organism by removing, changing or inserting individual genes
variation
differences between individuals of the same species
mutation
genetic change
gene mutation
a change in the base sequence of DNA
adaptive feature
an inherited functional feature that helps an organism to survive and reproduce in its environment and increase its fitness
fitness
the probability of an organism surviving and reproducing in the environment in which it is found
evolution
the change in adaptive features of a population over time as the result of natural selection
the process of adaptation
the process, resulting from natural selection, by which populations become more suited to their environment over many generations
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
catalyst
substance that increases the rate of a chemical reaction and is not changed by the reaction
enzymes
proteins that function as biological catalysts
diffusion
the net movement of particles from a region of their higher concentration to 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 (dilute solution) to a region of lower water potential (concentrated solution), 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
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
transpiration
loss of water vapour from plant leaves by evaporation of water at the surfaces of the mesophyll cells followed by diffusion of water vapour through the stomata
translocation
the movement of sucrose and amino acids in phloem from regions of production (source) to regions of storage OR to regions where they are used in respiration or growth (sink)
ingestion
the taking of substances, e.g. food and drink, 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
diarrhoea
the loss of watery faeces
pathogen
a disease-causing organism
transmissible disease
a disease in which the pathogen can be passed from one host to another
active immunity
defense against a pathogen by antibody production in the body
passive immunity
short-term defence against a pathogen by antibodies acquired from another individual, e.g. mother to infant
deamination
the removal of the nitrogen-containing part of amino acids to form urea
synapse
a junction between two neurones
nerve impulse
an electrical signal that passes along nerve cells called neurones
reflex action
an automatic response to a stimulus, a means of automatically and rapidly integrating and coordinating stimuli with the responses of effectors (muscles and glands)
sense organs
groups of receptor cells responding to specific stimuli: light, sound, touch, temperature and chemicals
hormone
a chemical substance, produced by a gland and carried by the blood, which alters the activity of one or more specific target organs
homeostasis
the maintenance of a constant internal environment, the control of internal conditions within set limits
gravitropism
a response in which parts of a plant grow towards or away from gravity
phototropism
a response in which parts of a plant grow towards or away from the direction from which light is coming
drug
any substance taken into the body that modifies or affects chemical reactions in the body