Plant and animal responses 5.5 Flashcards
describe what are auxins/IAA
- found in apical meristems
- cell elongation
- maintains apical dominance
- inhibits lateral shoot growth
- inhibits fruit ripening
- inhibits abscission
describe what are gibberellins
- promotes seed germination
- promotes stem elongation
- stimulates pollen growth in fertilisation
describe what is ethene
- promotes fruit ripening
- promotes abscission
describe what is abscissic acid/ABA
- maintains dormancy in leaves and seeds
- stimulates protective measurements like antifreeze and stomatal closure
define tropisms
a directional growth response in plants
what is phototropism
shoots grow towards light (+ve tropism)
- allows photosynthesis
roots away (-ve)
what is geotropism
roots grow towards pull of gravity (+ve)
- helps intake lots of water for support
what are physical defences in plants
thorns, spikes or hairy leaves
folding leaves in response to touch
what are chemical defences in plants
Alkaloids : bitter taste and poisonous to animals
Phermones - affects the social behaviour of other members of the same species
describe abscission as a response to abiotic stress
- phtochromes detect change is light levels or season
- ethene produces hydrolytic enzymes
- enzymes digest cell wall of separation zone
- separation zone falls off
- vascular bundles sealed off
- leaf fall
what are the benefits of abscission
- reduces energy needed to maintain leaves in the winter
- fallen leaves insulate roots
- rotten leaves provide minerals to plants
describe lack of water as a response to abiotic stress
- roots detect lack of water and produce ABA
- ABA travels to leaves and binds to receptors on guard cells
- ions move out of guard cell and affects the water potential gradient
- water leaves by osmosis
- guard cells become flaccid and close stomata
describe the effect of auxin concentration on apical dominance
- high auxin concentrations inhibit root growth and promote shoot growth
- low auxin concentrations promote root growth and inhibit shoot growth
what are the benefits of apical dominance
allows the whole of the plant to receive light as if the lateral shoots were long it would cover the rest of the plant from getting light
how does gibberellin concentration affect stem elongation
high gibberellin concentration means:
- longer internodes
-therefore taller plants
- and compete better for light
-so higher rate of photosynthesis
how is ethene used for commercial use
in fruits:
- speeds up ripening
- promotes lateral growth
-promotes fruit drop
how are gibberellins used for commercial uses
- farmers can prevent stem elongation to reduce waste and prevent crop damage in bad weather
- delay senescence in citrus
explain the experimental evidence that auxins maintain apical dominance
- removing shoot of apex means removing the source of auxins, causes cytokinins to stimulate lateral bud growth
- and causes ABA levels to drop
explain the experimental evidence that gibberellins control stem elongation and germination
stem elongation: tall plants have higher gibberellin concentration than dwarf
farmers can apply gibberellin externally onto dwarf plants to make them grow taller
mutant seeds with non-functional gibberellin is need gibberellin applied externally to germinate
how are cytokinins use commercially
prevent yellowing of lettuce leaves, promote shoot growth
how are auxins used commercially
rooting powder
growing seedless fruit
herbicides
low concentrations prevent leaf and fruit drop
high concentrations promote fruit drop
describe the difference between the CNS and PNS
CNS
- brain
- spinal cord
- relay neurone
PNS
- receptors
- motor and sensory neurone
what is the autonomic response
unconscious
e.g controls heart rate and breathing
what is the somatic response
conscious
e.g moving hand up and down
what is the sympathetic response
uses noradrenaline
fight or flight
increases heart rate
increases breathing rate
reduces digestion
dilates pupils
what is the parasympathetic response
uses acetylcholine
rest and digest
decreases the heart rate
decreases breathing rate
increases digestion
constricts pupils
what is the brain made up of and definitions
- cerebrum : main part of the brain that controls hearing,sight , thinking etc
- cerebellum : movement, coordination and balance
- medulla oblongata : autonomic, controls heart rate and breathing ]
- hypothalamus : autonomic , controls homeostasis
- pituitary gland : posterior (back) , controlled by hypothalamus and stores and releases ADH anterior (front), own glands and release own hormones
describe the knee jerk reflex
- tap under kneecap - cause patellar tendon to stretch and extensor muscle too
- sends reflex arc impulse through sensory neurone
- reflex signal goes along one motor neurone causing the extensor muscle to contract
- relay neurone inhibits the other motor neurone of flexor muscle and relaxes
- leg kicks due to antagonistic muscle
describe the blinking reflex
- cornea is irritated
-triggers impulse along sensory neurone
- relay neurone in lower brain stem and passes impulse along
- signal branches out in motor neurones to eyelid muscles
- both eyes shut due to a consensus response
explain how coordinated responses work
- nervous system detects threat stimuli
- stimulates autonomic response
- triggers hypothalamus
- stimulates the sympathetic nervous system which signals the adrenal medulla to release adrenaline and noradrenaline
AND
- stimulates the pituitary gland to release ACTH, signals the adrenal cortex to release steroids hormones
describe what is the skeletal muscle
- voluntary
- multi-nucleate
- cross-striated
- contract quickly for speed
- get fatigued
- contract slowly for endurance
-long muscle fibres
describe what is the smooth muscle
- involuntary
- found in walls of internal organs e.g small intestine
- one nucleus
- spindle shaped with pointed ends
- very small and short
- contract slowly
- dont fatigue
describe what is the cardiac muscle
- heart muscle
- myogenic
- connected by intercalated discs - for low electrical resistance for fast impulses
- branched - allow impulses to spread through the heart
- contract rhythmically and don’t fatigue
- some striations
what is the neuromuscular junction
synapse between a motor neurone and muscle cell
uses AcH, binds to recpetors on post-synaptic membrane
work same as synapses between neurones
what happens to the neuromuscular junction when a chemical is used
prevents the AcH from binding and being released
action potential not passed
muscle not contracted
if chemical is used instead and action potential is not passed what effect does it have on the body
dangerous for muscles that control breathing e.g the intercostal muscles and diaphragm
cant respire aerobically
what are myofibrils describe what the different structures are
made of sarcomeres
thick myofibrils = myosin
dark bands = A bands - myosin
thin = actin
Light bands = I bands - actin
in the middle = M line
around M line = H line and contains myosin only
describe muscle contraction
myosin and actin slide over each other to make sarcomeres contract
(myofibrils DONT contract)
muscle relaxes and sarcomeres return to og length
difference between relaxed and contracted sarcomeres
relaxed: A-band, I band and H band og length
contracted: A band same length, I band and H band shorten
define sarcomere, sarcolemma, sarcoplasm, sarcoplasmic reticulum
sarcomere : basic functional unit of a fibre
sarcolemma: plasmic membrane around fibres
sarcoplasm: shared cytoplasm within fibres
sarcoplasmic reticulum: endoplasmic reticulum in sarcomere
first step of the sliding filament model
stimulation and attachment
action potential triggers influx of Ca2+ ions
sarcoplasmic reticulum releases Ca2+ into the sarcoplasm
Ca2+ binds to troponin and causes conformational change and pulls the tropomyosin out of A-M binding site
myosin head binds to exposed site
A-M cross bridge formed
second stage of the sliding filament model
movement of myosin head
Ca2+ activate enzyme ATPase which breaks down ATP to ADP and Pi
causes myosin head to bend
releases ADP+Pi
causes myosin head to move myosin filament along
third stage of the sliding filament model
detachment
another mol. of ATP binds to myosin head, breaks cross-bridge, myosin head detaches
M head reattaches to a diff binding site along actin filament
new cross-bridge formed
cycle repeated
what happens when muscles stop being stimulated
Ca2+ leaves troponin mol. and returns to og shape
Tropomyosin blocks binding site
actin filaments slide back into relaxed position which lengthens sarcomere
describe the ATP-creatine phosphate system
anaerobic and antlactic
CP stored in ATP-CP system to generate ATP quickly
used in short burst of vigorous exercise
