3.6.1.1 stimuli, both internal and external , and detected and lead to a response Flashcards
why organism have to response to change in there environment
increase their chance of survival
increasing the likelihood of reproducing
passing alleles on to the next generation
simple response that can allow mobile organism maintain in favourable environment
taxis, kinesis
stimulus definition
A stimulus is a detectable change in the internal / external environment of an organism that leads to a response.
taxis
defintion
chracteristic
example
+ve / -ve
Movement of a whole organism in response to a stimulus (usually environmental changes)
- directional response
e.g. chemotaxis, phototaxis etc.
The direction of movement is determined by the direction of the stimulus
Positive taxes = organisms move towards a stimulus (usually favourable)
Negative taxes = organisms move away from a stimulus (usually unfavourable)
kinesis
characteristic
- non-directional
- changes the speed at which it is moving and the rate at which it changes direction in response to a stimulus
- Movement is random
If it moves into an unfavourable environment then its rate of turning decreases so that it moves in long straight lines before turning (vise versa)
chi square test
If the calculated 𝛘2 < table 𝛘2
Accept the Null hypothesis
Differences are just due to chance
If the calculated 𝛘2 > table 𝛘2
Reject the Null hypothesis
compare and contrast taxis and kinesis
both involve movement in repond to stimuli
directional vs non directioncal (randondom) [whereas]
whole organism movement vs growth response
animal vs plant
tropism
definition
+ve / -ve
The growth of plants in response to a directional stimulus
The plant grows towards (positive response) or away (negative response) from a stimulus
3 type of stmuli plants respond to
Light - phototropism (shoots positive)
Gravity - gravitropism (roots positive, shoots negative)
Water - positively hydrotropic
IAA/ auxin effect on plant
- increasing the flexibility / stretchiness of plant cell walls
= allowing cell elongation.
(Cell elongation on one side only can lead to a shoot or root bending.) in shoot - inhibit cell elongation in the root
What causes the uneven IAA distribution?
(for ans experiment Q)
- Light inhibits IAA on illuminated side
- Light destroys IAA on illuminated side
- Light stimulates the movement of IAA to the shaded side
gravitropism on shoot and root
shoot
- elongation
- bend up
- negative gravitropism
roots
- elongation inhibit
- ben down
- positive gravitropism
cns and pns and neuron involve
The CNS processes information.
Sensory neurones carry messages (electrical impulses) from the peripheral sense organs to the CNS
Motor neurones send electrical impulses from the CNS to effector organs (muscles or glands.)
definition of a stimulus
A stimulus is a change in the internal (inside organism) or external (outside organism) environment.
definition of receptor
A receptor detects a stimulus. Receptor cells are specific to one type of stimulus.
propose of effector
An effector produces a response.
voluntory and involuntory response (involve body structure)
Voluntary responses involve the brain (conscious thinking) and spinal cord
Involuntary responses occur without thinking and often involves the spinal cord
purpose/ advantage of reflex arc
- Rapid;
- Protect against damage to body tissues;
- Do not have to be learnt;
- Help escape from predators; (increase survival chance)
- Enable homeostatic control.
- Involuntary actions
what is a simple reflex arc
sensory neuron
relay neuron
motor neuron
only contain 3 neuron
exam Q : if tomato root grow toward gravity but salt is on the ground so it grow side ways what does this shows
salt have more effect than gravity
