Survival And Response Nervous Coordination Flashcards
Define taxis
Whole mobile organism has a directional response towards or away from a stimulus
Define kinesis
Whole mobile organisms has a random movement where rate of movement increases /decreases in response to a stimulus
Positive taxes
Towards the stimulus
Negative taxes
Away from the stimulus
Why do organisms need to respond to changes in the environment?
- Avoidance of harm full environments, competition or predator
- Stay within a favourable environment.
- Growth towards or away from stimuli.
- Dispersal to find new mate
Define tropism
A directional growth of a part of of a organism to a stimulus
Order of simple reaction pathway
- Stimulus.
- Receptor.- cell or organ
(Sensory neuron) - Coordinator ( brain or spinal cord)
(Motor neuron ) - Effector - muscle /gland
- Response.
Explain the advantages of simple reflex arcs
- Rapid.
- Protect against damage to body tissue.
- Does not have to be learnt
- Help escape from predators.
Sensory neuron
Sensory neuron into spinal cord
Relay neuron
In the middle of a spinal cord
Motor neuron
Out of spinal cord
Positive tropisms
Growth towards a stimulus
Negative tropism
Growth away from stimulus
Types of tropism
Halo - salt
Geo - gravity
Photo - light
Hydro - water
Aero - air
What is IAA?
Growth factor which causes elongation
What does IAA do in phototropism?
Diffusers to more shaded parts of roots and shoots
What does IAA do in geotropism?
Move to underside of roots and shoots
Cell elongation in the shoot
- IAA synthesise in shoot tips.
- Diffuses into growing region.
- Light causes movement off IAA from light side to shaded side.
- Causes directional growth as great to sell elongation on shaded side
- Shaded side grows faster and causes shoot to bend towards the light.
- This is positive phototropism.
Cell elongation in the roots
- IAA is synthesis in the root tips.
- Diffuses to the growing region.
- Light causes IAA to move from light side to shaded side towards gravity
- Higher concentration of IAA on shaded side.
- Cell elongation inhibited on shaded side.
- Resort in directional growth from light towards gravity.
- This is positive geotropism.
Is elongation promoted or inhibited in shoot?
Promoted
Is cell elongation promoted on inhibited in roots?
Inhibited
Why does plant move downwards towards the soil in the roots?
Water and nutrients
Why does the plant move towards the light in phototropism?
more light dependent reaction leading to more light independent reaction some more growth
