Why do organisms respond to their environment?
Reveal answer
Detect change → respond → survive and keep internal conditions steady.
Key words: survive
3(j) CO-ORDINATION AND RESPONSE · RECALL
3.30 Responding to the environment
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What apparatus tests the response of small animals to conditions?
Reveal answer
A choice chamber.
Key words: choice chamber
What is meant by the term receptor?
Reveal answer
Cell or structure that detects a stimulus.
Key words: receptor
What is meant by the term response?
Reveal answer
Change in activity caused by a stimulus.
Key words: response
What is meant by the term effector?
Reveal answer
Structure that carries out a response.
Key words: effector
Environmental responses: for Bright light at a shoot, give the receptor/route and the response value.
Reveal answer
Receptor/route: Light-sensitive tip/signalling. Response value: Growth toward light supports photosynthesis.
Key words: Bright light at a shoot
Environmental responses: for Touching a hot object, give the receptor/route and the response value.
Reveal answer
Receptor/route: Skin temperature/pain receptors. Response value: Withdrawal limits tissue damage.
Key words: Touching a hot object
Environmental responses: for Low blood water content, give the receptor/route and the response value.
Reveal answer
Receptor/route: Hypothalamic osmoreceptors. Response value: ADH response conserves water.
Key words: Low blood water content
Environmental responses: for Gravity acting on a root, give the receptor/route and the response value.
Reveal answer
Receptor/route: Gravity sensing in root tip. Response value: Growth downward supports anchorage and water uptake.
Key words: Gravity acting on a root
True or false, and why? “Only animals respond to stimuli.”
Reveal answer
False. Plants respond through growth, turgor and biochemical changes.
True or false, and why? “Every response is voluntary.”
Reveal answer
False. Many are automatic or involve growth.
True or false, and why? “A receptor is the same as a sense organ.”
Reveal answer
False. Sense organs contain receptors; individual receptor cells may also occur elsewhere.
What is a stimulus?
Reveal answer
A change in the environment that an organism can detect.
Key words: change
Woodlice move to damp, dark places in a choice chamber. Why does this help them survive?
Reveal answer
Less water loss and hidden from predators.
Key words: water loss
What is meant by sensitivity in living organisms?
Reveal answer
The ability to detect and respond to changes in the environment.
Key words: detect