Plant And Animal Responsss ( 5.1.5) Flashcards
(50 cards)
Central nervous system
Consists of your brain and your spinal cord and relay neurones
Peripheral nervous system
Consists of all neurones which connect CNS to rest of body
These are: sensory neurones, which carry nerve impulses from receptors to CNS; motor neurones carry impulses from CNS to effectors
Prepherial Nervous system is functionally organised into 2 systems
Somatic nervous system: under conscious control, when you voluntarily decide to do something
Automatic nervous system: system works constantly under subconscious control ( e. Heart beat)
How is autonomic nervous system split
Sympathetic motor system - fight or flight
Parasympathetic- relaxation
How are messages passed along in the somatic nervous system
Message from brain or spinal chord passes along a single neurone to effector organs releasing acetylcholine
Features of the Autonomic nervous system
Involuntary action
Lightly myelinated axon
Neurotransmitters: acetylcholine (parasympathetic), noradrenaline ( sympathetic)
Stimulatory or inhibitory depending on neurotransmitter + receptors on effector organs
Sympathetic : involved in flight or fight response
Parasympathetic : involved in relaxation response
Effect smooth muscle heart and digestion
How does SAN control heart rate
SAN initiates contractions
Rate of these contractions is controlled by: hormones acting directly on SAN ( adrenaline), messages from the autonomic nervous system
Where are the hormones that act directly on SAN secreted from
2 centres in the medulla oblongata, each is linked by a motor neurone to the sino atrial node
Vagus nerve- parasympathetic
Accelerator nerve- sympathetic
hormones in plants
coordinate plant response to environmental stimuli
move around by active transport, diffusion, or mass flow in phloem and xylem vessels
hormones in plants
coordinate plant response to environmental stimuli
move around by active transport, diffusion, or mass flow in phloem and xylem vessels
what effects can plant hormones have
have different effects on different tissues
amplify each others effects
cancel out each other effects
role of auxin hormone
control cell elongation, prevent leaf fall, maintain apical dominance, involved in tropisms, stimulate the release of ethene, involved in fruit ripening
role of gibberellin
cause stem elongation, trigger the mobilisation of food stores in seed at germination, stimulate polled tube growth in fertilisation
role of ethene
causes fruit ripening, promotes abscission in deciduous trees
ABA (abscisic acid)
maintains dormancy of seeds and buds, stimulates cold protective responses, e.g, antifreeze production, stimulates stomatal closing
how plant hormones effect seed germination
- when the seed absorbs water the embryo is activated and begins to produce gibberellins, - they in turn stimulate the production of enzymes that break down the food stores found in the seed
- embryo uses these food stores to produce ATP for building materials so it can grow and break through the seed coat
- gibberellins switch on genes which code for amylases and proteases - digestive enzymes required for germination
where is the food store in dicot seeds
- the food store is in the cotyledons in dicot seeds and the endosperm in monocot seeds
reasons for and hormonal involvement in abscission
falling light levels lead to a falling concentration of auxin
the leaves respond to this change by producing the gaseous plant hormone ethene
at the base of the stalk lies the abscission zone which has cells sensitive to ethene
ethene seems to initiate gene switching in these cells resulting in the production of new enzymes that digest and weaken the abscission zone
Hormone effect on stomata closure
opening and closing of the stomata due to abiotic stresses is largely under control of the hormone ABA
the leaf cells appear to release ABA under abiotic stress
ABA is transported to the leaves where it binds to receptors on the plasma membrane of the stomatal guard cells changing the ionic concentration of the guard cells reducing the water potential and therefore turgidity causing stomata to close
The effect of unilateral light
When plants are partially shaded the shoots grow towards the light then grow straight towards it
This response appears to be the result of the way auxin moves down the shaded side + elongates the cell
Geotropism
Plants are responsive to gravity, in normal situations growing acts downwards
Shoots are usually negatively geotropic and roots are positively geotropic
Abcission in plants
- Falling light levels cause a decrease in auxin concentration, the plants respond to this by producing the gaseous plant hormone ethene.
- Abscission zone at the base of the lead stalk is sensitive to ethene, which seems to initiate the switching on and off of some genes resulting in the production of enzymes, these enzymes weaken the abscission zone
- vascular bundles that carry materials to the leaf are sealed off and fatty acids are deposited on the stem side of the separation layer forming a protective scar
- in order to prevent pathogens entering
Chemical defences to herbivory - tannins
group of chemical compounds called phenols produced by plants
very bitter taste which puts animals off eating the leaves
toxic to insects, inactive digestive enzymes
tea and red wine are both rich in tannins
Chemical defences to herbivory - alkaloids
- large group of very bitter tasting nitrogenous compounds found in many plants
- many of them act as drugs affecting the metabolism of animals, and sometimes poisoning them
- e.g caffeine which is toxic to insects and fungi, also prevents seed germination of other plants
