IGCSE definitions Flashcards
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 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
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 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
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, 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
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
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
deamination
the removal of the
nitrogen-containing part of amino acids to form
urea
synapse
a junction between two
neurones
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
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
asexual reproduction
a process resulting
in the production of genetically identical
offspring from one parent
sexual reproduction
a process involving
the fusion of the nuclei of two gametes (sex cells)
to form a zygote and the production of offspring
that are genetically different from each other
fertilisation
the fusion of gamete nuclei
pollination
the transfer of pollen grains
from the anther to the stigma
self-pollination
the transfer of pollen
grains from the anther of a flower to the stigma
of the same flower or different flower on the
same plant
cross-pollination
transfer of pollen
grains from the anther of a flower to the stigma
of a flower on a different plant of the same
species
sexually transmitted infection
an infection that is transmitted via body fluids
through sexual contact
inheritance
the transmission of genetic
information from generation to generation
chromosome
a thread-like structure of
DNA, carrying genetic information in the form of
genes
gene
a 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
nuclear division giving rise to
cells that are genetically different
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
variation
differences between
individuals of the same species
mutation
genetic change
gene mutation
a change in the base
sequence of DNA
adaptive feature
the inherited
functional features of an organism that increase
its fitness
fitness
the probability of an organism
surviving and reproducing in the environment in
which it is found
process of adaptation
the process,
resulting from natural selection, by which
populations become more suited to their
environment over many generations
food chain
the transfer of
energy from one organism to the next, beginning
with a producer
trophic level
the position of an
organism in a food chain, food web, pyramid of
numbers or pyramid of biomass
food web
a network of interconnected
food chains
producer
an organism that makes its
own organic nutrients, usually using energy from
sunlight, through photosynthesis
consumer
an organism that gets its
energy by feeding on other organisms
herbivore
an animal that gets its energy
by eating plants
carnivore
an animal that gets its energy
by eating other animals
decomposer
an organism that gets its
energy from dead or waste organic material
population
a group of organisms of one
species, living in the same area, at the same time
community
all of the populations of
different species in an ecosystem
ecosystem
a unit containing the
community of organisms and their environment,
interacting together
genetic engineering
changing the
genetic material of an organism by removing,
changing or inserting individual genes
sustainable resource
one which is
produced as rapidly as it is removed from the
environment so that it does not run out
sustainable development
development providing for the needs of an
increasing human population without harming
the environment
