plant and animal responses 5.5 Flashcards
chemical defenses in plants
- increases there chances of survival to herbivory
- alkaloids= bitter tasting chemical
-tannin’s= taste bitter, can make the plant hard to digest in some animals - some plants releases pheromones a signalling chemical to produce a response in another organism
e,g, alarm pheromones which can be detected by other plants causing them to start making chemical defenses
mimosa pudicas response
- if touched, a signal spreads through the whole leaf causing it to fold
- can knock of small insects
- can scare off animals trying to eat it
example of a response to abiotic stress
- = non-living e,g whether
- in extreme cold conditions carrots produce a antifreeze protein which binds to ice crystals lowering the temperature at which water freezes. stopping more ice crystals growing
- stomata can also close
tropisms
- a response to a directional stimulus
- phototropism= growth of plant in response to light
- shoots are a positive tropisms= grow towards the lights to increases photosynthesis
- roots are negatively tropisms= grow away from light
- geotropisms= growth in response to gravity
- shoots are negatively as grow upwards
-roots positive as they grow downwards
auxins (IAA)
-cell/stem elongation=stimulates growth of plant
- also inhibits fruit ripening and abcisission by inhibiting ethene
- maintains apical dominace preventing growth of lateral buds
ethene
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-promotes fruit ripening and abscission
gibberellins
- promotes stem elongation = increasing internode length( distance between the branches in the stem)
- promotes seed germination. =stimulates production of enzymes to release glucose from food store. the energy is used for seed growth
absiscic acid (ABA)
-stimulates protective measures e.g. antifreeze production and stomatal closure’opening
Auxins experiment
-when the tips are removed,no auxin is made so stems do not grow
-when the tips are covered,auxins moves to all parts of the stem causing all parts to grow. prevents auxins from being broken down by light
-when the tips are lit from one side only auxin accumulates on the shaded side causing it to grow more than the illuminated side
hormones involved in leaf loss of deciduous plants
-they loose there leaves in the winter to conserve water that would have been lost in the leaves.
- auxins inhibit leave loss, as plant gets older less auxins are produced leading to leaf loss
-ethene stimulates leaf loss. is produced by ageing leaves so more leaves loss.
-ethene works antagonistically to auxin’s
the brain
- cerebellum= coordinates movement and balance
- medulla oblongata= coordinates many of the autonomic responses e.g. heart rate
- hypothalamus= homeostatsis
-pituitary gland= stores and releases hormons made by the hypothalamus
reflec arc
-a rapid responses to a change in the environment that does not involve any processing in the brain.
- has a survival value
knee jerk reflex
- helps to maintain balance and posture
- stretch receptors in quadriceps muscles detect muscle in being stretched
-nerve impulse passes along sensory neurone communicating directly with a motor neurone in the spinal chord - motor neurone transfers impulse along to the effector (qaud msucles) causing it to contract straightening the leg
- only two neurons involved meaning less synapses for quicker responses
blinking reflex
- corena is irritated
- triggers impulse along sensory neuron to relay neurone in the lower brain to motor neurone (eyelid muscles) causing both eyes to close
action of adrenaline
-primary messenger
-binds to receptors on the surface membrane of target cell which activates the enzyme adenyl cyclase
- adenyl cyclases converts ATP to cyclic AMP (cAMP) which is the secondary messenger inside the cell
cAMP activates enzyme actions depending on the cell adrenaline binds too
controlling the heart rate= interaction between the nervous system and endocrine system
-endocrine= adrenal medulla releases adrenaline and noradrenaline to increases heart rate
- nervous system chemoreceptors and baroreceptors in the carotid arteries and the aorta monitor ph of the blood
- during excersize muscles release carbon dioxide which combins with water forming carbonic acid and dissocates forming H+ ions lowing blood ph therefore sends actional potential to the cardiovascular system to increase heart rate.
- accelerans nerves=increase heart rate
-vagus nerve= decrease in heart rate
the structure of the mammalian muscle
- muscle fibres made up of sacromere wrapped around by the sacromela.
- contains the sacroplasm and sacroplasmic reticulum
- also consists of ,myofibrils= has Actin + myosin
- thick myofilaments are myosin and the thinner filaments are actin
under microscope - the dark bands are mysoin
- A band are overlapping myosin and actin filaments
-light bands are only actin (l- band) - the h-line is the space in the middle containing only myosin
- m-line = middle line
-z-line = ends of each sacromere
-Muscle contraction results in both the H-band and I-bands shortening, but the A-band remains the same length
the sliding filament model of muscular contraction
and the role of ATP
- action potential arrives and depolarizes the sacromela and sacromela reticulum therefore cauasing the sacromela reticulm to realease calcium ions into the sacroplassm
-actin is wrapped around my tropomyosin and held in place by troponin - calcium ions bind to troponin, causing a conformational change. this pulls the attached tropomyosin out of the actin-myosin binding site on the actin filamment
- this exposes the binding site which allows myosin heads to bind forming a actin-myosin cross bridge
-mysoin muscles flex moving actin filamentrs along using ATP .
-ATP is needed to break the actin-myosin crossbridge causing deattchment
neuromuscular junction
- synapses between motor neurons and muscle cells
-work in the same way synapses between neurons do
-action potential arrives causing calcium channels to open and calcium ions into the junction - vesicles of aceycholine move torwards and fuse with the end membrane
- acetylcholine molecules diffuses across the gap and fuse with receptors on the sacromela
-the sodium ion channels open allowing sodium ions to enter the muscle fibres, causing depolarisation of the sacromela
-wave of depolarisation spreads across allowing muscle to contract - this stimulates the sliding filament theory