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Biology OCR A Alevel > plant and animal responses > Flashcards

plant and animal responses Flashcards

1
Q

name 3 plant responses to abiotic stress

A
  • leaf loss
  • prevention of freezing by having solutes in cell sap and cytoplasm that lower freezing point
  • stomatal control
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2
Q

name 3 chemicals that plants use in their defence to herbivores and what they do

A

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

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3
Q

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?

A

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

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4
Q

what is phototropism?

A

plants response to light. shoots are positively phototrophic and roots are negatively phototrophic

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5
Q

what is geotropism?

A

plants response to gravity which always they always receive as a unilateral stimulus downwards
shoots are negatively geotrophic and roots are positively geotrophic

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6
Q

describe the roles of hormones in leaf loss

A

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

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7
Q

describe the roles of hormones in seed germination

A

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

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8
Q

describe the roles of hormones in stomatal closure

A

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

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9
Q

explain and give 2 peices of evidence for the role of auxin in apical dominance

A

(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

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10
Q

explain how gibberellins are used in germination and give 2 pieces of evidence for this

A

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

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11
Q

how are gibberellins used in stem elongation and give 2 peices of evidence

A

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

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12
Q

how is ethene used comercially in plants?

A

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

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13
Q

name 2 ways in which auxin is used comercially in plants

A

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.
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14
Q

what are the two sections the nervous system is organised into structurally?

A

the central nervous system and peripheral nervous system

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15
Q

what is the central nervous system?

A

the brain and spinal cord

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16
Q

what is the peripheral nervous system?

A

all the neurones that connect the CNS to the rest of the body - sensory and motor neurones

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17
Q

how is the nervous system arranged functionally?

A

into the somatic and autonomic nervous system

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18
Q

what is the somatic nervous system?

A

the system under conscious control

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19
Q

what is the autonomic nervous system?

A

works constantly under subconscious control

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20
Q

what is the difference between sympathetic and parasympathetic nervous system?

A

parasympathetic is the relaxing responses- what happens all the time

sympathetic is in regard to the fight or flight response

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21
Q

what is the function of the cerebrum?

A

controls voluntary actions, interpreting sensory information sends impulses to motor neurones for response

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22
Q

what is the function of the cerebellum?

A

controls unconscious functions - it coordinates movement such as balance and posture etc

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23
Q

what is the function of the medulla oblongata?

A

contains many regulatory centres of the autonomic nervous system- heart rate, ventillation etc

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24
Q

what is the function of the hypothalamus?

A

main controlling region for the autonomic nervous system, it controls temperature. it produces hormones that stimulate other glands

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25
Q

what is the function of the pituitary gland?

A

under the control of the hypothalamus. it releases hormones and stimulates other glands to release hormones

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26
Q

list the sequence in a reflex arc

A 
stimulus
receptor
sensory neurone
relay neurone
motor neurone
effector
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27
Q

what kind of reflex is the knee-jerk reflex?

A

spinal reflex

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28
Q

describe the knee-jerk reflex

A

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

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29
Q

what survival advantage does the knee jerk reflex have?

A

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

30
Q

what kind of reflex is the blinking reflex?

A

cranial reflex - it goes to lower brain stem not spinal cord

31
Q

describe the blinking reflex

A

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

32
Q

what is the survival advantage of the blink reflex?

A

it protects eye from damage

33
Q

what detects the threat in a fight or flight response?

A

the hypothalamus

34
Q

what are the functions of the sympathetic nervous system in the fight or flight response?

A

send impulses to muscles and glands

causes adrenal medulla to make noradrenaline and adrenaline and release into blood stream

35
Q

what is the role of the hormonal system in the fight or flight response?

A

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

36
Q

describe the action of adrenaline

A

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

37
Q

what controls heart rate?

A

the autonomic nervous system by the medulla oblongata

38
Q

what are the two centres in the medulla oblongata controlling heart rate?

A

one increases heart rate by the accelerator nerve

one decrease heart rate by the vagus nerve

39
Q

what do barorecptors do to control heart rate?

A

the detect change in blood pressure

40
Q

what do chemoreceptors do to control heart rate?

A

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 .

41
Q

where are baroreceptors located?

A

in the aorta, vena cava and carotid artery

42
Q

where are the chemoreceptors located?

A

aorta, carotid artery and medulla

43
Q

what is the function of skeletal muscle?

A

concious movement

44
Q

what is the function of cardiac muscle?

A

to keep the heart beating regularly- only found in the heart and is myogenic so doesnt need stimulus

45
Q

what is the function of involuntary muscle?

A

also known as smooth muscle

used in subconscious movement such as in hollow organ such as the stomach and bladder

46
Q

what is the structure of skeletal muscle?

A

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

47
Q

what is the structure of cardiac muscle?

A

fainter striations and cells branch and interconnect so that they contract simultaneously
uni nucleic fibres

48
Q

what is the structure of involuntary muscle?

A

no striations
no regular arrangement- contract in different directions
spindle shaped fibres that are uninucleic

49
Q

what is the structure of myofibrils?

A

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

50
Q

what is the structure of a myosin flament?

A

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

51
Q

what is the structure of actin?

A

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

52
Q

what is a neuromuscular junction?

A

where a motor nuerone and skeletal muscle meet

53
Q

how does a neuromuscluar juntion work?

A

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

54
Q

what are the steps of the sliding filament model?

A

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

55
Q

how is ATP supplies maintained?

A

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

56
Q

what are the effects of adrenaline?

A

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

57
Q

what happens when baroreceptors detect high blood pressure?

A

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

58
Q

what happens when baroreceptors detect low blood pressure?

A

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

59
Q

what happens when chemo receptors detect change in chemical levels in the blood

A

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

60
Q 
what happens to 
the light band
the z lines
the h zones 
the dark band
during muscle contraction
A

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

61
Q

what are the differences between the sympathetic and parasympathetic responses?

A

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 ;

62
Q

Give three reasons why both plants and animals need to be able to respond to changes in
their environment.

A

(both) to, avoid / counter, (abiotic) stress ;
(both) to avoid, being eaten / predation ;
(both) to access resources ;

63
Q

State three differences in the ways in which plant and mammalian hormones operate.

A

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

64
Q

what are 4 effects of adrenanline?

A

relaxes smooth muscle in the bronchioles
increases frequency impulses sent from the SAN
Increases glycogenolysis
causes erector muscles in the skin to contract

65
Q

what is the role of contracting erector muscles in the skin in the fight or flight response?

A

to make them look bigger and more aggressive

66
Q

what does Abscisic acid do?

A

inhibits seed germination

stomatal closure in low water availability

67
Q

what does auxin do?

A

cell elongation

inhibit lateral bud growth

inhibit leaf abscission

68
Q

what do gibberellins do?

A

seed germination

growth of stems

69
Q

what does ethene do?

A

fruit ripening

produced when low levels of auxin for leaf loss

70
Q

how do gibberellins promote stem elongation?

A

they stimulate cell elongation and division

71
Q

how do gibberellins promote seed germination?

A

they activate genes for amylase and protease enzymes which break down food stores

72
Q

how does auxin inhibit leaf loss and fruit drop?

A

it ihibits abscission by preventing ethene production from increasing

Biology OCR A Alevel (26 decks)

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