plant and animal responses Flashcards
name 3 plant responses to abiotic stress
- leaf loss
- prevention of freezing by having solutes in cell sap and cytoplasm that lower freezing point
- stomatal control
name 3 chemicals that plants use in their defence to herbivores and what they do
tanins - bitter taste and can bind to proteins in the gut so they’re hard to digest
Alkaloids - bitter taste and noxious smell
pheromones -if one plant produces pheremones in response to grazing, it cause nearby plants that detect it to produce chemical defences such as tanins
what plant is known for its folding in response to touch and how does this occur and how does it help the plant against herbivores?
Mimosa pudica
rapid uptake of water in cells at the base of each leaflet causes adjacent cells to lose volume and collapse
scares off herbivores and dislodges small insects
what is phototropism?
plants response to light. shoots are positively phototrophic and roots are negatively phototrophic
what is geotropism?
plants response to gravity which always they always receive as a unilateral stimulus downwards
shoots are negatively geotrophic and roots are positively geotrophic
describe the roles of hormones in leaf loss
lengthening dark periods/ loss of light causes falling level of auxin to be produced.
ethene is formed in response
a layer of cells called the abscission layer develops at the bottom of the leaf stalk . ethene stimulates the abscission layer to expand, breaking the cell walls and causing the leaf to fall off
or cause gene switching in abscission zone and new enzymes are produced which break down abscission zone
describe the roles of hormones in seed germination
when seed absorbs water the embryo is activated giberellins are produced
giberellins stimulate digestive enzymes such as amylase to be produced which breaks down food stores
ATP created by the metabolism is used for growth
ABA works against and inhibits enzyme
describe the roles of hormones in stomatal closure
ABA produced by the roots when low level of water in soil
ABA binds to receptors on the cell surface membrane of guard cells.
ABA activates changes in the ion concentrations of guard cells and reduces the water potential and therefore the turgor of cells as water has moved out
cell becomes flaccid and therefore stomata closes
explain and give 2 peices of evidence for the role of auxin in apical dominance
(auxins produced at the apex of the plant cause plant to grow upwards and inhibits lateral growth)
if apex bud and therefore the auxin source is removed, lateral bud growth occurs
if apical bud is replaced with agar block containing auxin, inhibition is restored- lateral bud growth stops
explain how gibberellins are used in germination and give 2 pieces of evidence for this
gibberellins stimulate amylase to be produced which causes digestion of food sources leading to ATP being creating which provides energy for growth.
mutant varieties that do not produce giberellins cannot germonate
however they germinate normally when gibberellins are applied externally
if gibberellin biosynthesis inhibitors are applied, the plant doesnt germinate
how are gibberellins used in stem elongation and give 2 peices of evidence
they causes cell elongation and division leading to stem growth.
dwarf varieties (where giberellin synthesis pathways are inhibited) show very low levels of gibberellins
treating dwarf varieties with gibberellins allows them to grow to normal height
how is ethene used comercially in plants?
control of fruit ripening
ethene stimulates the break down of cell walls, chlorophyll and converts starch into sugars = soft and ripe
harvested unripe then exposed to ethene when needed so they all ripen at the same time
name 2 ways in which auxin is used comercially in plants
rooting powder
- when cutting is made, it is treated with auxin causing it to grow roots so it can be replanted
weed killer
- auxin used as a selective weed killer
- makes weeds produce long stems but not big leaves so plant grows too fast and doesnt get enough water and nutrients so it dies.
what are the two sections the nervous system is organised into structurally?
the central nervous system and peripheral nervous system
what is the central nervous system?
the brain and spinal cord
what is the peripheral nervous system?
all the neurones that connect the CNS to the rest of the body - sensory and motor neurones
how is the nervous system arranged functionally?
into the somatic and autonomic nervous system
what is the somatic nervous system?
the system under conscious control
what is the autonomic nervous system?
works constantly under subconscious control
what is the difference between sympathetic and parasympathetic nervous system?
parasympathetic is the relaxing responses- what happens all the time
sympathetic is in regard to the fight or flight response
what is the function of the cerebrum?
controls voluntary actions, interpreting sensory information sends impulses to motor neurones for response
what is the function of the cerebellum?
controls unconscious functions - it coordinates movement such as balance and posture etc
what is the function of the medulla oblongata?
contains many regulatory centres of the autonomic nervous system- heart rate, ventillation etc
what is the function of the hypothalamus?
main controlling region for the autonomic nervous system, it controls temperature. it produces hormones that stimulate other glands
what is the function of the pituitary gland?
under the control of the hypothalamus. it releases hormones and stimulates other glands to release hormones
list the sequence in a reflex arc
stimulus receptor sensory neurone relay neurone motor neurone effector
what kind of reflex is the knee-jerk reflex?
spinal reflex
describe the knee-jerk reflex
stretch receptors in the patellar tendon detect stretch(stimulus)
a nerve impulse is sent along the snesory neurone which contects with a motor neurone
the motor neurone carries the nerve impulse to the effector muscle- extensor muscle on top of thigh contracts and flexor muscle relaxes
what survival advantage does the knee jerk reflex have?
it helps to maintain balance and posture
if your knee buckles after a landing the reflex causes your quadreceots to contract so you stay upright
what kind of reflex is the blinking reflex?
cranial reflex - it goes to lower brain stem not spinal cord
describe the blinking reflex
sensory nerve endings in the cornea are stimulated by touch
a nerve impulse is sent along the sensory neurone to the relay neurone in the lower brain stem
impulse is passed onto motor neurone
motor neurones send impulse to orbicularis oculi muscles which contract causing the eyelid to shut
what is the survival advantage of the blink reflex?
it protects eye from damage
what detects the threat in a fight or flight response?
the hypothalamus
what are the functions of the sympathetic nervous system in the fight or flight response?
send impulses to muscles and glands
causes adrenal medulla to make noradrenaline and adrenaline and release into blood stream
what is the role of the hormonal system in the fight or flight response?
causes the pituitary gland to secrete ACTH which is released in the blood and causes the cortex of the adrenal gland to release steriodal hormones
describe the action of adrenaline
adrenaline (primary messenger) binds to receptors on the cell surface membrane of liver cells.
this activates adenylyl cyclase (hormone)
adenylyl cylcase then converts ATP into cyclicAMP (secondary messenger)
cAMP activates enzymes and glycogen is converted to glucose for respiration
what controls heart rate?
the autonomic nervous system by the medulla oblongata
what are the two centres in the medulla oblongata controlling heart rate?
one increases heart rate by the accelerator nerve
one decrease heart rate by the vagus nerve
what do barorecptors do to control heart rate?
the detect change in blood pressure
what do chemoreceptors do to control heart rate?
they detect change in chemical levels e.g. pH due to increase in carbon dioxide so reacts with water and increases the concentration of carbonic acid so lowers pH .
where are baroreceptors located?
in the aorta, vena cava and carotid artery
where are the chemoreceptors located?
aorta, carotid artery and medulla
what is the function of skeletal muscle?
concious movement
what is the function of cardiac muscle?
to keep the heart beating regularly- only found in the heart and is myogenic so doesnt need stimulus
what is the function of involuntary muscle?
also known as smooth muscle
used in subconscious movement such as in hollow organ such as the stomach and bladder
what is the structure of skeletal muscle?
striated and arranged so that contractions only occur in one direction multinucleic fibres
bundles of muscle fibres sharing a cytoplasm called the sarcoplasm and all fibres enclosed in the sarcolemma (plasma memebrane)
sarcolemma folds inwards to create T-tubules that help the spread of impulse.
the sarcoplasmic reticulum stores and releases calcium ions needed for muscle contraction.
contains lots of mitochondria to provide ATP for contraction
long cylindrical organelles called myofibrils
what is the structure of cardiac muscle?
fainter striations and cells branch and interconnect so that they contract simultaneously
uni nucleic fibres
what is the structure of involuntary muscle?
no striations
no regular arrangement- contract in different directions
spindle shaped fibres that are uninucleic
what is the structure of myofibrils?
made of actin and myosin
z line showing the end and start of each sarcomere
H band showing where only myosin is present
A band from start of myosin to end
I band where only actin is present
what is the structure of a myosin flament?
have globular heads which are hinged allowing them to move back and forth each has a binding site of actin and ATP
thousands line up to make a myosin filament
what is the structure of actin?
actin filaments have binding sites for myosin heads called actin myosin binding sites but theses are often blocked by tropomyosin which is held in place by the protein troponin
what is a neuromuscular junction?
where a motor nuerone and skeletal muscle meet
how does a neuromuscluar juntion work?
same as a synapse but once sarcolemma is depolarised, it spreads through t tublus to depolarise sarcoplasmic reticulum causing calcium ion channels to open and flood out into the sarcoplasm which is then used in muscle contraction
what are the steps of the sliding filament model?
calcium ions bind to the troponin causing it to change shape and pull the tropomyosin away from the actin-myosin binding sites
these binding sites can now bind with the myosin heads forming actin myosin cross bridge
once attached the head flexes and moves the actin filament along and the ADP molecule bound to the head is released
ATP molecule binds to the head ad causes it to detach from the actin filament as it is hydrolysed from ATP to ADP and phosphate releasing energy which the head uses to return to its original position
the myosin head can now attach itself to another actin myosin binding site further along and the process continues as long as the muscle is stimulated
how is ATP supplies maintained?
creatine phosphate is used as a reserve supply of phosphate and allowes ADP to be phosphorylated to ATP
this is replensished when the msucle relaxes using phosphate from ATP
what are the effects of adrenaline?
increase heart rate
bronchioles relax
glycogen is converted to glucose
arterioles in the gut and skin constrict and arterioles supplying the heart, lungs and skeletal muscles dilate
erector pili muscles contract so hairs stand on end
what happens when baroreceptors detect high blood pressure?
if BP is too high impulses are sent to the medulla from the baroreceptors the medulla decreases the frequency of impulses sent along the vagus nerve to decreases heart rate. impulses are sent to the SAN to decrease HR
what happens when baroreceptors detect low blood pressure?
if BP is too low impulses are sent to the medulla from the baroreceptors
the medulla increases the frequency of impulses sent along the accelerator nerve to increase heart rate. impulses are sent to the SAN to decrease HR
what happens when chemo receptors detect change in chemical levels in the blood
impulses from the chemoreceptors are sent to the medulla
decreasing/increasing the impulses sent along the vagus/ accelerator nerve to the SAN
this decreases/increases the heart rate
what happens to the light band the z lines the h zones the dark band during muscle contraction
the light band gets narrower
the z lines move closer together - the sarcomere shortens
the H zone gets narrower
the dark band remains the same
what are the differences between the sympathetic and parasympathetic responses?
S has, short preganglionic neurone / long
postganglionic neurone / ganglia near(er) spinal cord,
but P has, long preganglionic neurone / short
postganglionic neurone / ganglia near(er) organ ;
S uses noradrenaline but P uses acetylcholine (at
organ) ;
S, fight / flight / stress, but P, rest / relaxation / calm ;
S increases, heart rate / cardiac output / blood
pressure, but P reduces this ;
S increases , speed / rate / depth, of breathing, but P
reduces this ;
S increases airway diameter but P reduces it ;
S increases blood flow to skeletal muscle but P
increases blood flow to gut (smooth muscle) ;
S dilates pupils but P constricts pupils ;
S makes liver release glucose, but P makes liver,
store / take up, glucose ;
P allows, peristalsis / digestion, but S reduces it ;
Give three reasons why both plants and animals need to be able to respond to changes in
their environment.
(both) to, avoid / counter, (abiotic) stress ;
(both) to avoid, being eaten / predation ;
(both) to access resources ;
State three differences in the ways in which plant and mammalian hormones operate.
1 (M) made in endocrine glands versus
(P) made in many plant tissues ;
2 (M) move in blood versus
(P) move, in xylem / in phloem / from cell to cell ;
3 (M) act on, a few / specific / target, tissues versus
(P) act on most tissues / can act in cells where produced ;
4 (M) act more rapidly ; ORA
what are 4 effects of adrenanline?
relaxes smooth muscle in the bronchioles
increases frequency impulses sent from the SAN
Increases glycogenolysis
causes erector muscles in the skin to contract
what is the role of contracting erector muscles in the skin in the fight or flight response?
to make them look bigger and more aggressive
what does Abscisic acid do?
inhibits seed germination
stomatal closure in low water availability
what does auxin do?
cell elongation
inhibit lateral bud growth
inhibit leaf abscission
what do gibberellins do?
seed germination
growth of stems
what does ethene do?
fruit ripening
produced when low levels of auxin for leaf loss
how do gibberellins promote stem elongation?
they stimulate cell elongation and division
how do gibberellins promote seed germination?
they activate genes for amylase and protease enzymes which break down food stores
how does auxin inhibit leaf loss and fruit drop?
it ihibits abscission by preventing ethene production from increasing
