3.6.1.1 Survival and Response Flashcards
How do organisms increase the chances of survival?
- By responding to changes in their environment.
What are changes in the environment called?
- Stimulus
What are the 4 main responses?
- Tropisms
- Taxis
- Kinesis
- Simple reflexes
How are tropisms controlled?
- By Growth Factors
How do growth factors work?
- Growth factors move to other tissues, where they regulate growth in response to directional stimuli.
What is the main growth factor in plants?
- Auxin/IAA
What happens in roots and shoots during phototropism?
ROOTS: IAA diffuses to the under side of the root causing cell elongation to be inhibited and bend downwards.
SHOOTS: IAA diffuses to the darker side of the shoot causing cell elongation on the darker side bending towards light.
What happens in roots and shoots during Gravitropism?
SHOOTS: IAA diffuses to the lower side of the shoot and causes cell elongation upwards.
ROOTS: IAA diffuses to lower side of the roots, inhibitng cell elongation so the root bends downwards.
What is taxis and kinesis?
- Simple responses that maintain a mobile organism in a favourable condition.
What is taxis specifically?
- Organisms that move towards/away a directional stimulus
What is kinesis specifically?
- Organisms movement changes due to a non-directional stimulus.
How do simple reflexes work?
1) Receptors detect stimulus.
2) Sensory neurone carries impulse from receptor to the relay neurone.
3) Relay neurone carries impulse directly from sensory neurone to motor neurone.
4) Effector carries out the response
Why are simple reflexes important?
- FAST (doesn’t involve the conscious part of the brain due to the relay neurone)
- LOCALISED (Neurotransmitter is secreted directly onto target cells producing similar responses)
