Survival And Response Flashcards
What is a stimuli?
A detectable change in the internal or external environment of an organism, that produces a response
Give three examples of stimuli in plants, and three in animals
Plants- light, gravity, water
Animals- light, sound, pressure
What is tropism, and what is the difference between negative and positive?
Tropism a plants growth response to an external, directional stimuli
Positive tropism- where the plant grows towards the stimulus
Negative- where the plant grows away from the stimulus
What is positive and negative phototropism? And what are their survival values?
Positive- plant shoots grow towards the light, so leaves can absorb more light for photosynthesis
Negative- plant roots grow away from light, into the soil so they can absorb more water and ions
What is positive and negative gravitropism? And what are their survival values?
Positive- young roots grow towards gravity, into the soil so they can absorb more water and ions
Negative- young stems grow away from gravity, out of the soil so the leaves are exposed to sunlight for photosynthesis
What is positive hydrotropism? Why is this beneficial?
Where plant roots grow towards water
The root systems grow and spread in areas of soil that have more water, so more water is absorbed
What are auxins?
Plant growth regulators
What is the most common auxin and where it is produced?
IAA
Controls directional growth in tropisms in flowering plants
Produced in the tip of the shoot or root, and move by diffusion to other parts of the plant.
How dopes IAA control phototropism in shoots?
Shoots are positively phototropic
IAA accumulates on the shaded side, and causes elongation
The shaded area grows faster than the side in the light
Shoot bends and grown towards the light
How does IAA control phototropism in roots?
Roots are negatively phototropic
IAA accumulates on the shaded side, and inhibits cell elongation
The shaded region grows slower than the area in the sun
The roots bend a are grows away from the light
How does IAA affect shoots and roots differently?
It causes cell elongation in shoots
And inhibits cell elongation (growth) in roots
What is gravitropism?
The growth of plants roots and shoots in response to gravity
How does IAA control gravitropism in shoots?
Shoots are negatively gravitropic
IAA accumulates on the lower side of the clerks due to gravity
Causes cell elongation, the underside of the shoots grow more than the upper side
The shoot bends and the shoot grown upwards
How does IAA affect gravitropism in roots?
Roots are positively gravitropic
IAA accumulates in the bottom of the cell due to gravity
Cell elongation is inhibited
The underside of the root grows less than the upper side, so the root bends and grows downwards
What is meant by innate?
An instinctive behaviour that does not have to be learnt
What is a taxis?
An innate behaviour in animals
It is a directional response to a stimulus, carried out by the whole organism
It can be positive or negative
What is a kinesis?
An innate behaviour in animals
It is a non-directional response to a stimulus, resulting in a change of random movement patterns
What are the two sections of the nervous system ?
The central NS- the brain and spinal cord
The peripheral NV- sensory and motor nerves
Describe how nerve cells stimulate a response
Nerve cells (neurones) pass electrical impulses along their length and stimulate their target cells by secreting neurotransmitters directly onto them. This results in rapid, short lived and localised responses
What is a reflex?
A rapid, short lived involuntary response to a specific stimulus
What is the function of sensory neurone?
They carry electrical impulses from receptors to the CNS
What is the function of motor neurones?
They carry electrical impulses from the CNS to effectors
What is the shortest pathway taken by impulses known a?
The reflex arc
Explain the process of the reflex arc- specifically the withdrawal reflex
A stimulus is detected and generates impulses in the sensory neurone
A sensory neurone enters the spinal cord. The neurone synapses with a relay neurone, which then synapses with a motor neurone
Motor neurone carries the impulse to the effector (like muscle cells) which then contracts to move away from the stimuli
Sensory information concerning the reflex action is then carried to your brain so you are aware of your response
How can you tell is a response is part of the reflex arc?
If only three neurones are used
