Plant and animal responses Flashcards
Plant chemical responses to herbivores
-tannins- toxic and make leaf taste bad
-alkaloids- growing tips and flowers, making them taste bitter
-pheromones- affect the behaviour or physiology of another organism
Types of plant response
Tropisms- directional growth responses:
-phototropism- shoots grow towards light= positively phototropic
-geotropism- roots grow towards the pull of gravity, anchoring them in the soil
-chemotropism- response to chemicals eg. pollen grows down style attracted by chemicals
-thigmotropism- shoots of climbing plants wind around other plants
Nastic response- non directional response to external stimuli eg. mimosa folding leaves when touched = thigmonasty
Effect cytokinins
-promote cell division
-delay leaf aging
-overcome apical dominance
Effect abscisic acid
-inhibits seed germination
-stomatal closure when low water availability
Effect auxins
-promote cell elongation
-inhibit growth side shoots
-inhibit leaf fall
Effect gibberellins
-promote seed germination
-promote growth of stems
Effect ethene
-promotes fruit ripening
Auxin when tip broken off and role abscisic acid, cytokinins
-auxin prevents growth lateral buds
-when tip broken, auxin levels drop and side shoots grow
-tested by applying auxin paste to broken tip and lateral buds didn’t grow
-high auxin keeps abscisic acid levels high, when tip removed, abscisic acid level drop causing growth lateral buds
-cytokinins promote lateral bud growth by overriding apical dominance effect. High auxin makes shoot apex a sink for cytokinins, when removed, they spread around plant
Gibberellic acid experiments
-compare GA1 levels of tall vs short pea plants
-Le gene responsible for producing enzyme that converts GA20 to GA1
-dominant Le allele= tall plant
Seed germination
-seed absorbs water and embryo releases gibberellins
-enables production amylase which breaks down starch to glucose
-glucose can be respired so seed grows
Location of meristems in plants
-apical meristems in tips of shoots or roots
-lateral bud meristems
-lateral meristems for widening of roots and shoots
Mechanism of auxin’s effect
-increases stretchiness of cell wall by promoting active transport of H+ by ATPase enzyme on membrane
-this decreased pH is optimum for wall-loosening enzymes to work
-enzymes break bonds between cellulose so become less rigid
Enzymes involved in redistribution of auxin
-phototropin 1 and phototropin 2- activity promoted by blue light
Commercial uses auxin
-take cuttings and dip in auxin to encourage root growth
-treat unpollinated flowers with auxin, it will grow seedless fruit
-used as herbicides as stems grow rapidly so the weed can’t support itself so buckles and dies
Commercial uses cytokinins
-prevent yellowing lettuce leaves after picked
-mass production of plants
Commercial uses gibberellins
-used in shops to keep fruit fresh for longer
-make apples elongate to improve shape
-elongate grape stalks, meaning grapes grow bigger
-brewing, as speed up process
-sugar productions, stems elongate, so more sugar available from each plant
Commercial uses ethene
-speed up fruit ripening in apple, tomatoes etc
-promote fruit drop in walnuts, cherries
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Nervous system divisions
-divides CNS and PNS
-CNS divides spinal cord and brain
-PNS divides into motor and sensory
-motor divides autonomic and somatic
-autonomic divides into parasympathetic and sympathetic
CNS
-brain composed relay neurones, non-myelinated= grey matter
-spine has non-myelinated relay neurones making up grey matter, but also has myelinated which make outer region white matter
Motor nervous system
-conducts AP from CNS to effectors
-divided into somatic= voluntary control eg. muscles and autonomic= non-voluntary eg. glands
Sympathetic system
-many nerves leading out CNS to effector
-ganglia outside CNS
-noradrenaline= neurotransmitter
-increase activity
Parasympathetic system
-few nerves leading out CNS to effector
-ganglia in effector tissue
-acetylcholine= neurotransmitter
-decreases activity
Cerebrum
-2 cerebral hemispheres
-higher brain functions eg. conscious thought, intelligence, decisions
-cerebral cortex- outermost layer for sensory, association and motor areas
Sensory areas-receive AP from sensory receptors
Motor areas- send AP to effectors
Association areas- compare sensory input with experience to come up with appropriate response
Cerebellum
-balance and fine coordination
-receives info from sensory receptors eg. retina
-control requires learning and can then become 2nd nature
-cerebrum and cerebellum connected by pons
Hypothalamus
-centre brain above pituitary gland
-controls homeostatic mechanisms using negative feedback eg. osmoregulation
Pituitary
-posterior- links hypothalamus by neurosecretory cells to release hormones from hypothalamus
-anterior- produces hormones in response to releasing factor from hypothalamus
Medulla oblongata
-control non skeletal muscles eg. cardiac by AP in ANS
-regulates heart rate, blood pressure, breathing rate
-coordinates by negative feedback
Reflex actions
-don’t involve any processing in the brain to coordinate movement
-3 neurones - sensory, relay, motor
-for survival or to avoid danger
Corneal reflex
-mediated sensory neurone in cornea that enters the pons
-3 neurones- sensory, relay, motor
-2 synapses
-rapid and causes both eyes to blink even if only 1 effected
Optical reflex
-dilation of pupil
-can’t be overridden
-protects the retina from light damage
-slower than corneal reflex
Knee jerk reflex
-spinal reflex
-2 neurones- sensory + motor
-one synapse
Mechanism of adrenaline action
-binds receptor on plasma membrane
-activates g protein, which activates adenyl cyclase
-converts ATP to cAMP = 2nd messenger
-causing an effect inside cell by activating enzyme action
Release of hormones from pituitary
molecules released
-CRH form hypothalamus causes release of ACTH which stimulates adrenal cortex to release cortisol, causing more glucose to be released from glycogen stores
-TRH causes release of TSH which causes more thyroxine to be released from thyroid gland, this increases metabolic rate of cells
Roles of heart
-transport of oxygen and nutrients
-removal of waste eg CO2
-transport urea from liver to kidney
-distribute heat
Myogenic
-the heart can initiate its own beat at regular intervals
Change heart rate by cardiovascular centre
-in medulla oblongata
2 nerves alter frequency of contractions
-accelerans nerve- causes release noradrenaline which increases heart rate
-vagus nerve- releases acetylcholine which reduces heart rate
Sensory input to cardiovascular centre
-stretch receptors in muscles, increased stretch= more Na+ released, so AP reached and sent to cardiovascular centre to increase heart rate
-chemoreceptors- monitor pH, high CO2 decreases pH, detected and send AP to cardiovascular centre
-Baroreceptors- monitor blood pressure, increase blood pressure causes stretching carotid artery, this prevents heart rate going too high
Artificial control heart rate
- artificial pacemaker which delivers electrical impulse to heart
-implanted under skin or within chest cavity
-connected to SAN or to ventricle muscle
3 types muscle
Smooth (involuntary) muscle
-individual cells
-spindle shaped
-controlled autonomic NS
-arranged longitudinal and circular layers
Cardiac muscle
-individual cells form long fibres which branch forming cross bridges
-cells joined intercalated discs which allow free diffusion of ions between cells
Skeletal (striated) muscle
-cells form fibres which are multinucleate
-each fibre surrounded by the sarcolemma
-cytoplasm= sarcoplasm
-ER= sarcoplasmic reticulum
-arranged into myofibrils that divide into sarcomeres
Structure of myofibril
-contain 2 types protein filament
-thin filaments= actin which make up light band held by z line
-thick filaments= myosin which make up dark band held by M line
Sarcomere structure
-z line to z line
-gap where no overlap= H zone
-A band= length of thick filament
-I band= thin filament without overlapping thick filament
Muscle contraction stimulation and control
-AP arrives at pre synaptic bulbs which opens Ca2+ channels
-Ca2+ diffuse in causing vesicles with acetylcholine to fuse with the membrane
-AC diffuses across cleft and binds receptors on Na+
-opens Na+, diffuse in, depolarising membrane
-depolarisation spreads along the sarcolemma and down the transverse tubules
-this causes Ca2+ to be released from the sarcoplasmic reticulum
-Ca2+ bind troponin, which alters the shape and pulls tropomyosin aside, exposing binding sites
-myosin heads bind to sites forming cross bridges
-heads move pulling the actin filament past the myosin filament
-myosin heads detach from actin and can bind again further up the actin filament
-acetylcholinesterase breaks down AC to stop another contraction
Motor unit
-when all muscle fibres contract together providing a stronger contraction
Thin filaments
-2 chains of actin wound around each other
-wound with tropomyosin and troponin
-at rest these proteins cover the binding sites so the thick filaments can’t bind
Thick filaments
-bundle myosin fibres
-each myosin molecule has 2 protruding heads
-heads are mobile and bind to actin when site exposed
Sliding filament hypothesis
-during contraction light band and H zone shorten
-z lines move closer, sarcomere gets shorter
Roles of ATP in muscle contraction
-myosin head attaches to actin forming cross bridges
-head moves backwards, causing actin to slide past= power stroke which releases ADP + Pi form head
-after power stroke, ATP binds to head breaking cross bridge
-myosin head returns to normal position as ATP hydrolysed, releasing energy for this to occur
Maintaining supply of ATP for muscle contractions
-aerobic respiration in mitochondria
-anaerobic respiration in the sarcoplasm
-creatine phosphate- in sarcoplasm and acts as a reserve of phosphate groups
