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Biology-14-Response To The Stimuli > Survival And Response > Flashcards

Flashcards in Survival And Response Deck (13):

What’s a stimulus

Is a detectable change in the internal or external environment of an organism that leads to a response in the organism


Organisms that survive have a greater chance of raising offspring and if passing their alleles to the next generation. What does this mean in terms of response

There is always a selection pressure favouring organisms with more appropriate responses


What do receptors do

They detect stimuli and are specific to one type of stimulus


What do effectors do

They produce a response (may be on a molecular level or of whole organism)


What are the sequence of events for a response

Stimulus e.g. see a friend waving

Receptors e.g. light receptors in your eyes detect the wave

CNS(coordinator) - processes information

Effector - muscle cells are stimulated by motor neurones

Response - muscle cells contract to make your arm wave


What is a taxis

A simple response whose direction is determined by the direction of the stimulus


How are taxis classified

Positive taxis - towards the stimulus

Negative taxis - away from the stimulus

Natures of the stimulus


What is kinesis

A form of response in which the organism does not move towards of away from a stimulus

Instead it changes the speed at which it mov s and the rate at which it changes direction



What happens if an organism crosses a sharp diving line between a favourable and an unfavourable environment

It’s rate of turning increases


What happens if it moves a considerable distance into an unfavourable environment

It’s rate of turning will slowly decrease so that it moves in long straight lines before it turns, often very sharply


What is a tropism

The growth part of a plant in response to a directional stimulus


What’s it if the plant grows towards or away from the stimulus

Toward ( positive response )

Away ( negative response)


How do do plant roots grow to increase probability that they will grow into the soil, where they are able to absorb water and mineral ions

Grow away from light ( negative phototropism )

Grow towards gravity ( positive gravitropism)