Survival and Response Flashcards
Stimulus…
a detectable change in the internal or external environment of an organism, that produces a response
Give three examples of stimuli in plants?
Light, gravity and water
Response to light
phototropism
Response to water
hydrotropism
Response to gravity
gravitropism
Where is a stimulus detected in a shoot or root?
Tip
Where would you find ‘plant growth factors’?
They are produced in growing regions
What do ‘plant growth factors’ do?
stimulate or inhibit growth
Name a type of plant growth hormone?
Auxin
What is one of the main auxins called and what does it do?
IAA (indoleacetic acid) and it controls directional growth seen in tropisms
What are tropisms in shoots and roots due to?
Uneven distribution (diffusion) of IAA causing uneven growth of different parts of the plant causing cell elongation and bending towards the stimuli
How does IAA cause one side (the shaded side) to growth quicker than the other in SHOOTS?
Cell elongation occurs and these cells produce more organelles (such as mitochondria) so more ATP is made and used up for cell growth
What effect does IAA have in the roots?
negative phototropic response
Opposite to the shoots
It causes the shaded side to be inhibited by growth so the shaded side grows at a slower rate, causing the root to bend away from light rather than towards light
Describe the different gravitational responses in the root and the shoot?
Root > auxin (IAA) inhibits growth so cells on lower side grow more slowly so root curves downwards
Shoot > auxin (IAA) stimulates growth so cells on lower side grow faster so shoot curves upwards
Innate…
from birth, does not have to be learnt, instinctive
Name two simple innate forms of behaviour and what do they allow organisms to do?
Taxes and Kinesis
These allow mobile organism to respond to environmental changes and maintain them in favourable conditions for survival
What characteristics do Taxes and Kinesis have?
- Genetically determined
- Stereotyped pattern: similar in all members of that species
- Consists of a chain of reflexes
- Typical of an organism with a short life cycle
What is taxis behaviour?
Directional response towards a stimulus (positive or negative)
What is kinesis behaviour?
Non-directional response to a stimuli, random movement patterns
If an organism is in an unfavourable environment they would…
move faster and change direction less in order to get away from the area
If an organism was in a favourable environment they would…
move slower, change direction more frequently to stay in the same place
Where do Sensory neurones carry impulses to?
From receptors towards the central nervous system (CNS)
Where do Motor neurones carry impulses to?
From the CNS to the effectors (muscle, glands etc.)
Summarise nervous control:
Stimuli > Receptor > Co-ordinater CNS (brain and spinal cord) > Effector > Response
What do nerve cells do?
Pass electrical impulses along their length and stimulate their target cells by secreting chemical neurotransmitters directly onto them. This results in a RAPID, SHORT-LIVED and LOCALISED response
A reflex is…
a rapid, automatic response to a specific stimuli
Why are simple reflexes important?
They are:
- involuntary
- rapid
- controlled internally
- essential for survival
- innate
The reflex arc…
is the shortest pathway taken by the impulse in a simple reflex
Describe a reflex arc
- Sensory Neurone synapses with a Relay Neurone which synapses with a Motor Neurone
- Motor Neurone carries the impulse to the effector , which then contracts, causing a response
- Sensory information concerning this reflex action is then carried up to the brain to make you aware of what has happened
