14.1 — stimuli and responses Flashcards
through what do organisms detect stimuli?
receptors
what do receptors do?
they initiate responses from effectors
what is the pathway of response in an organism?
- stimulus — a detectable change in the internal or external enviroment of an organism
- receptor — detects specific types of stimulus
- coordinator — coordinates a suitable response to the stimulus
- effector — produces a response to a stimulus
- response — the action produced by the effector
what is a stimulus?
a detectable change in the internal or external enviroment of an organism
what does a receptor do?
detects specific types of stimulus
what does a coordinator do?
coordinates a suitable response to the stimulus
what does a effector do?
produces a response to a stimulus
what is a response and what produces it?
the action produced by the effector
why are responses to stimuli crucial for survival — what do they allow organisms to do?
they allow organisms to:
- navigate towards beneficial resources like food
- evade predators or harmful conditions
what does responses to stimuli do to the probability of survival and successful reproduction?
increases it
what is a taxis?
a taxis is a simple response whose direction is determined by the direction of the stimulus
what do taxes do?
they guide organisms either towards a beneficial stimulus or away from a harmful one
what do positive taxes do?
lead towards a favourable stimuli
what do negative taxes do?
prompt movement away from adverse stimuli
what are some types of taxes?
- positive phototaxes — when an organism moves towards light (e.g. when algae moves towards light for photosynthesis to synthesis food)
- negative phototaxis — when an organism moves away from light (e.g. earthworms move away from light because the heat of the sun can dry out their skin out)
- positive chemotaxis — when an organism moves towards a towards a region where a specific chemical is more concentrated (e.g. bacteria move towards regions rich in glucose to obtain food)
what is positive phototaxes?
when an organism moves towards light
what is an example of positive phototaxes?
when algae moves towards light for photosynthesis to synthesis food
what is negative phototaxis?
when an organism moves away from light
what is an example of negative phototaxis?
earthworms move away from light because the heat of the sun can dry out their skin out
what is positive chemotaxis?
when an organism moves towards a towards a region where a specific chemical is more concentrated
what is an example of positive chemotaxis?
bacteria move towards regions rich in glucose to obtain food
what do kineses do?
adjust the movement speed and turning frequency of an organism based on the favourability of the environment
how is the kinesis affect in unfavourable conditions?
increased turning occurs
how is the kinesis affect in favourable conditions?
accelerated movement
what is a tropsim?
the growth of a part of an organism (like a plant) in response to a directional stimulus
what does phototropism do?
directs growth towards or away from light
what does gravitropsim do?
directs growth towards or away from the gravitational pull
what tropisms do the shoots of plants exhibit and why?
- positive phototropism
- negative gravitropism
to optimise light absorption for photosynthesis
what tropisms do the roots of plants exhibit and why?
- negative phototropism
- positive gravitropism
increase the probability that roots will grown into the soil, where they can absorb more water and mineral ions
