5.5 plant and animal responses Flashcards
difference between abiotic and biotic
abiotic = non living
biotic = living
name the chemical defences of plants when under threat of herbivores
tannins
alkaloids
pheromones
what do tannins do
toxic to microorganisms and larger herbivores
make leaves taste bad
prevent infiltration by pathogenic microorganims in roots
what do alkaloids do
taste bitter
in tips and flowers and peripheral cells in stems, roots
what do pheromones do
chemicals released that can affect anothers behaviour/physiology
define tropism
a directional growth response determined by an external stimulus
name the different types of tropisms as a response to abiotic stress
photo - light
geo - gravity
chemo - chemicals
thigmo - physical contact eg. ivy growing around structures
hydro - water
define nastic response
a non directional response to external stimuli
example of nastic response
folding in when touched
name the plant hormones
cytokinins
abscisic acid
auxins
gibberellins
ethene
effects of cytokinins
promote cell division
delay leaf senescence
overcome apical dominance
promote cell expansion
effects of abscisic acid
inhibits seed germination/ growth
causes stomatal closure when low water availablity
effects of auxin
promote cell elongation
inhibit growth of side shoots
inhibit leaf abscission (leaf fall)
where is auxin made
apex of the shoot
effects of gibberellins
promote seed germination
stem growth
effects of ethene
promotes fruit ripening
general role of plant hormones
coordinate plant responses to environmental stimuli
how do hormones move in a plant
active transport
diffusion
mass flow
leaf senescence vs leaf absission
senescence = development of leaves
absission = leaf fall
define apical dominance
inhibition of lateral buds further down the shoot due to chemical produced by the apical bud at the tip of the shoot
explain the relationship between auxin concentration and growth
normal auxin conc. in lateral buds inhibits growth
where as low auxin conc. promotes growth
how are auxins, abscisic acid and cytokinins involved in plant growth
abscisic acid = inhibits bud growth - high auxin levels in shoot keeps the AA levels high = when the tip is removed AA levels drop and the bud starts to grow
cytokinins = promotes bud growth = high auxin levels = sink for cyto. = apical dominance = when tip removed cytokinin spreads evenly around plant = lateral growth
role of gibberellins in seed germination
seed absorbes water = releases gibberellins = stimulates amylase production = breaks starch into glucose = substrate for respiration/ protein synthesis = embryo can grow
how do gibberellins cause growth
causes growth in internodes by stimulating cell elongation (loosening of cell walls) and cell division (stimulates protein production that controls cell cycle)
explain the experiment about gibberellins in dwarf and tall plants
tall plants = high concentrations of Ga1 (gibberellins)
tall plants = have homo. dominant Le allele
dwarf = have homo. recessive le allele
Le is responsible for converting G20 to GA1 (gibberellins)
plant with mutant (na-1) blocks gibberellin production in first step
grafted this shoot onto homozygous le plant = grew tall as shows it has the enzyme toconvert G20 to GA1 and can use the G20 provided from the other plant
therefore proves GA1 causes stem elongation/ growth
where does the growth occur in plants
meristem
in roots/ shoots
explain Darwins results in investigating plant hormones
the shoot tip is responsible for phototropic responses
explain Boysen-Jensons results in investigating plant hormones
substance in the tip needs to be able to move backwards for phototropism to happen
- permeable block = shoot still showed phototropism
- impermeable block = no phototropic response
explain Went’s results in investigating plant hormones
chemical messenger doesn’t need tip to be present to allow phototropism
how was auxin proved to be the chemical messenger for growth in plants in investigating plant hormones
agar blocks with with different auxin concentrations on gave the same results
using a series of blocks with diff. conc. of auxin (IAA) created by serial dilution gave shoot curvature in proportion to the amount of auxin
equal light = equal growth all around
unequal light = auxins move to shade = cells elongate quicker = bends to light
extent of cell elongation = con. of auxin
mechanism of auxin
causes active tranpsort of H+ by ATPase enzymes on plasma membrane into cell wall
results in low pH
provides optimum pH for enzymes to break bonds within the cellulose
wall becomes less rigid and can expand as cell takes in water
explain the effect of auxin in the roots and shoots
shoots - light on one side = auxin moves to shaded side = zone of elongation = cells elongate
roots - auxin accumulates on lower side and inhibits cell elongation = upper side continues to grow = root bends down
explain the effect of auxin concentration on stimulation and inhibition of growth in the roots and shoots
at low concentrations = root growth is stimulated
at high concentrations = shoot growth stimulated and root growth inhibited
the commercial use of auxin
prevent leaf and fruit drop
promote flowering
herbicides - promotes growth too much that cell cannot support= breaks = plant dies
seedless fruit
encouraging root growth/ taking cuttings
the commercial use of cytokinins
delay leaf senescence / prevent yellowing of leaves
mass produce plants in tissue culture
promote bud and shoot growth
the commercial use of gibberellins
fruit production
-delay senescence - makes fruits available for longer
-can elongate apples to improve shape
-grape stalks elongate = less compact so bigger grapes
brewing
- speeds up germination of barely
sugar production
- stimulates growth in nodes = stems elongate = more sugar can be stored
plant breeding
- speed up process by inducing seed formation
commercial use of ethene
speeds up fruit ripening
promotes fruit drop
promotes lateral growth
promotes female sex expression in cucumbers
central nervous system
central part of the nervous system composed of the brain, spinal cord and relay neurones
peripheral nervous system
the sensory and motor neurones connecting the sensory receptors and effectors to the cns
what does the PNS divide into
somatic and autonomic
describe the somatic nervous system
conduct action potentials from the cns to the effectors
under voluntary control
mostly myelinated = responses are rapid
one single neurone connecting
describe the autonomic nervous system
conduct action potentials from the cns to the effectors
under involuntary control
mostly non myelinated = responses are not rapid
two neurones are connected by a ganglia
what can the autonomic nervous system be divided into
sympathetic and parasympathetic
describe the sympathetic nervous system
prepares the body for activity
fight or flight response
noradrenaline as neurotransmitter
increases activity
during times of stress
describe the parasympathetic nervous system
conserves energy
relaxing responses
acetylcholine as neurotransmitter
decreases activity
during sleep/ relaxation
effects of the sympathetic and parasympathetic nervous systems (opposite)
sympathetic
- increase heart rate
- dilates pupils
- increase ventilation rate
- reduces digestive activity
parasympathetic
- decrease heart rate
- constricts pupils
- reduce ventilation rate
- increase digestive activity
Name the structures of the brain
Cerebrum
Cerebellum
Medulla oblongata
Hypothalamus
Pituitary
Function of the cerebrum
Conscious thought
Conscious actions
Emotional responses
Intelligence, decision making etc.
Memory
Divided into two cerebral hemispheres (left side controls right side of body)
Function of the cerebellum
Coordinates balance and muscle control/ coordination
Function of the medulla oblongata
Controls physiological processes
Eg. Cardiac centre , Vasomotor centre, Respiratory centre
Function of the hypothalamus
Coordinates homeostasis responses
Temperature regulation
Osmroregulation
Functions of the pituitary
endocrine gland
anterior lobe - secretes hormones
posterior lobe - stores hormones
define reflex action
a response that doesn’t involve any processing by the brain
what neurones make up the reflex pathway
sensory - relay - motor
explain the blinking reflex
temporary closure of the eye
is a cranial reflex - passes through the brain
explain the knee jerk reflex
relex that straightens the leg
is a spinal reflex - passes through spinal cord
response is quick as only uses sensory and motor neurone
where is the fight or flight response coordinated
hypothalamus
how does the hypothalamus coordinate a response
increases activity in the sympathetic nervous system
stimulates release of hormones from the anterior pituitary gland
what does the hypothalamus secrete and their role
releasing hormones into the blood
passes into the pituitary which causes release of tropic hormones from anterior pituitary
stimulates endocrine glands
what does CRH cause
from the hypothalamus causes the release of ACTH from the pituitary
what does TRH cause
from the hypothalamus causes release of TSH
what does ACTH cause
adrenal cortex to release cortisol hormones
what does TSH cause
thyroid stimulating hormone
the thyroid to release more thyroxine
explain what happens in response coordination in the nervous pathway
sympathetic nervous system
activates adrenal medulla - adrenaline released into the bloodstream
impulses activate glands/ smooth muscles
fight or flight response initiated
explain what happens in hormonal coordination in the nervous pathway
hypothalamus releases hormones to stimulate the pituitary gland
pituitary secretes ACTH - adrenal cortex releases corticoid hormones - into the bloodstream
pituitary secretes TSH - thyroid gland secretes thyroxine - into the bloodstream
initiates fight or flight response
mechanism of adrenaline
protein hormone = can’t enter cell
adrenaline (first messanger)
binds to receptor = associated with a G protein inside cell = activates enzyme adenyl cyclase
converts ATP to cAMP
(second messanger)
cyclic AMP causes activation of enzymes
how can the heart generate its own heartbeat
myogenic cardiac muscle - initiate its own beat
SAN - pacemaker - controls wave of excitation/ action potential by nerves (accelerater, vagus)
describe the role of the accelerator and vagus nerve
accelerator = increases heart rate
vagus = reduces heart rate
what is the cardiovascular centre located
medulla oblongata
how does the cardiovascular centre recieve information
stretch receptors = in muscles = detect movement = send impulses to the cardiovascular centre = extra 02 needed= hr increases
chemoreceptors = in carotid arteries, aorta = monitor pH = exercise produces co2/ carbonic acid
baroreceptors in carotid sinus = detect blood pressure
3 types of muscle
smooth (involuntary)
skeletal (voluntary)
cardiac
explain the structure of cardiac muscle and its benefits
cells form long fibres
branch to form cross bridges
ensure electrical stimulation spreads evenly over the walls cells joined by intercalated discs - allow movement of ions
doesn’t fatigue easily, myogenic
explain the structure of smooth muscle
spindle shaped cells
contracts slowly and regularly
doesn’t tire easily
controlled by autonomic nervous system
in longitudinal and circular layers
explain the structure of skeletal muscle (sarco)
striated
sacorlemma - membrane that surrounds the fibres that contain many nuclei
sarcoplasm - muscle cell cytoplasm that contains lots of mitochondria and
sarcoplasmic reticulum - specialised endoplasmic reticulum
myofibrils - contents of the fibres are arranged in
sarcomeres - myofibrils are divided into chain of subunits that contain protein filaments, are the contractile units of muscle
what proteins are in muscles to allow contraction
actin
myosin
neuromusclar junction
junction where a neurone and muscle meet
how is a muscle contraction stimulated at a NMJ
action potential arrives at the end of the axon
opens calcium ions channels = move into axon
causes vesicles of acetylcholine to move to the membrane
exocytosis = acetylcholine molecules diffuse across the gap = fuse with receptors on the sarcolemma
opens sodium ion gates = enters muscle fibres = causes depolarisation
wave of depolarisation passes along sarcolemma = spreads down tubule (T system)
causes calcium ions to be released from sarcoplasmic reticulum = causes muscle contraction
name the 4 proteins found in muscles
actin
myosin
tropomyosin
troponin
explain what the H zone, A band, I band and Z lines are
H zone = area in the centre where only myosin is, dark band
A band = the whole length of myosin
I band = area where there is only actin, light band
Z lines = hold together actin
what are the thin filaments and thick filaments of a muscle
thin = actin
thick = myosin
structure and function of the proteins of thin filaments
actin = two strands that wind around each other, twisted double string of beads
tropomyosin winds around the actin = blocks binding sites at rest
troponin = complex of 3 polypeptides - one binds to actin, one to tropomyosin and one to calcium
structure and function of thick filaments
bundle of myosin molecules
has two potruding heads
heads are mobile and bind to actin when sites are exposed
briefly explain the mechanism of muscle contraction
caused by movement of myosin heads
muscle stimulated = tropomyosin moves exposing binding sites = myosin binds to sites on actin = causes actin to slide past myosin
control of muscle contraction
action potential passes to sarcoplasmic reticulum = calcium ions released into sarcoplasm
calcium ions bind to the troponin = alters the shape and tropomyosin is pulled aside = exposes binding sites on the actin
myosin heads bind to the actin = forms cross bridges between the filaments
myosin heads move = pulls actin past past the myosin
myosin heads detach and bind again further up the actin
how is a muscle relaxed
calcium ions pumped back into sarcoplasmic reticulum
role of ATP in muscle contraction
myosin head attaches to the actin filament = cross bridge
myosin head tilts backwards = causing actin to move past = power stroke = ADP +Pi are released
after the power stroke a new ATP joins = breaks cross bridge
myosin head returns to original position as ATP is hydrolysed to ADP +Pi = as it releases energy
myosin can now form new cross bridge
maintaing the supply of ATP
aerobic respiration = high oxygen supply = lots of ATP released = limited to how much 02 is supplied
aerobic respiration = release less ATP but lactic acid builds up = fatigue
creatine phosphate = reserve store = phosphate transferred to ADP molecules creating ATP = supports contraction for another 2-4 seconds
