Survival And Response Flashcards
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
W
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)
