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abiotic factors

physical factors in the environment which can act as a stimuli for the organisms' responses


the range of physical factors which are favourable for the organism

biotic factors

biological influences on organisms within an ecosystem


change in environment which causes a response in an organism


any cell or group of cell which detects a change in stimuli


a cell or group of cells which respond to change


relationships between different species


relationships between organisms in the same species


all things living in a particular area including physical factors


he place or environment in which specific organisms live

limiting factor

any variable factor which limits the activity of an organism or population

gause's principle

no two species with identical ecological niches can co-exist for long in the same place

ecological niche

the way an organism lives

biological clocks

Internal timing systems that continue without external clues, and control (to some extent) the timing of activities of plants and animals.

period of the rhythm

the time it takes to complete one cycle of activity

phase shift

a shift in the activity of a biological rhythm, typically provided by a synchronizing environment stimulus

free running period

The natural period of the rhythm if there are no external cues.


Process by which an internal clock becomes reset by rhythmic environmental factors


the environmental agent that resets the biological clock e.g: change in light, temperature


of or relating to biological processes occurring at 24-hour intervals




A rhythm of about 12.5hours


A rhythm of about 1 month


A rhythm of about 1 year


the response in animals and plants to the length of the day and night

exogenous rhythm

A rhythm that continues only when external cues are present.

endogenous rhythm

An internal rhythm that occurs when there are no external cues. Caused by a biological clock


the growth response of a plant toward or away from a stimulus

nastic movement

a plant's response to a stimulus such that the direction of the response is preprogrammed and not dependent of the direction of the stimulus


movement of a whole organism towards or away from a stimulus


a non-directional response to to a stimulus - animals


Ability of an animal to find its way home over unfamiliar territory


substance produced in the tip of a seedling that stimulates cell elongation

apical dominance

Concentration of growth at the tip of a plant shoot, where a terminal bud partially inhibits axillary bud growth


Concentration of growth at the tip of a plant shoot, where a terminal bud partially inhibits axillary bud growth


a growth hormone that causes a wide variety of effects. One role is to stimulate growth of stems by promoting cell division. Farmers use it to make fruit grow larger

apical meristem

the growing region at the tips of stems and roots in plants


hormone that promotes leaf abscission and fruit ripening

abscisic acid

hormone that promotes bud and seed dormancy and inhibits leaf abscission


the act of causing a plant to develop without chlorophyll by growing it without exposure to sunlight

short day plants

plants that bloom only when the period of daylight is shorter than a specific period of darkness

long day plants

plants that bloom only when the period of day is longer than a specific period of darkness

day neutral plants

A plant in which flowering can occur irrespective of the day length


pigment used to measure time


Exposure of seeds to a period of cold to break the seeds' dormancy


a period when an organism's growth or activity stops


when a moist seed is exposed to a low temperature for many days to break dormancy


the process where seeds need to be scratched or treated in a rough way before it can germinate


a chemical present in desert plants which prevents germination unless there is sufficient ain which washes the chemical away


shedding of flowers and leaves and fruit following formation of scar tissue in a plant

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