3.6.1.1 survival and response Flashcards
Suggest two advantages of simple reflexes
- Rapid;
- Protect against damage to body tissues;
- Do not have to be learnt;
- Help escape from predators;
- Enable homeostatic control;
What is a stimulus?
A detectable change in the internal or external environment of an organism.
Why is the ability to respond to stimuli advantageous.
It increases the chances of survival
Stimuli are detected by…
receptors
A response is controlled by a…
coordinator e.g. brain
A response (e.g. hormone secretion) is produced by an…
effector
The two modes of communication between cells in large multicellular organisms are…
- Hormonal communication
2. Nervous communication
What is the sequence of events leading from a stimulus to a response?
Stimulus >Receptor > Coordinator > Effector >Response
Define taxis.
A directional response in which a whole organism moves towards or away from a stimulus.
Movement of a whole organism towards light (e.g. algae) is called…
Phototaxis (positive)
Positive taxis is…
Movement towards a stimulus by a whole organism.
Negative taxis is…
Movement away form a stimulus by a whole organism.
Define kinesis.
Random movement of a whole organism in response to a non-directional stimuli e.g. temp or humidity. This may be an increase/decrease in speed or turning frequency.
Define tropism
the growth of part of a plant in response to a directional stimulus e.g. light, gravity, water
When plant shoots grow towards light we call it…
positive phototropism
When plant shoots grow away from gravity we call it…
negative gravitropism
When plant roots grow away from light we call it…
negative phototropism
Why do woodlice increase their rate if turning if they exit favourable conditions?
To increase the probability that they will re-enter the favourable conditions.
Why do woodlice decrease their rate of turning and move rapidly after spending a while in unfavourable conditions?
To increase the chances that they will pass through the unfavourable conditions and enter more favourable.
Woodlice move in response to stimuli via the process of…
kinesis
When roots grow towards water we call it…
positive hydrotropism
As well as taking in water the function of roots is to…
anchor plants into the ground
The growth responses (tropisms) of plants are controlled by hormone like substances called…
plant growth factors
How do plant growth factors differ from hormones?
- They are produced by cells located throughout the plant (not just a particular organ/gland)
- They tend to affect the tissues that release the growth factors rather than ‘target’ tissues.