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Biology > topic 5.1.5: plant and animal responses > Flashcards

topic 5.1.5: plant and animal responses Flashcards

1
Q

what are examples of abiotic stressors

A

high winds, excess or lack of water, temp changes

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2
Q

give 5 plant responses to abiotic stress

A

leaf loss, daylength sensitivity, abscission, preventing freezing, stomatal closure

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3
Q

what is photoperiodism

A

sensitivity to lack of light

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4
Q

how do plants carry out abscission on leaves

A

light levels decrease, ethene switches on genes for enzymes which digest cell walls in separation layer, leaf falls and waterproof scar forms

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5
Q

how do plants respond to herbivory

A

physical defences eg thorns
chemical defences eg alkaloids and pheromones
folding in response to touch

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6
Q

what are alkaloids

A

nitrogenous, bitter tasting chemicals eg nicotine

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7
Q

what are pheromones

A

affect behaviour of other members of same species
vocs in plants

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8
Q

what are tropisms

A

plant growth responses to stimuli from one direction

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9
Q

how do phototropisms affect shoots

A

shoot tips produce auxin, causing cell elongation
auxin diffuses to other cells on shaded side so plant bends towards light

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10
Q

how do phototropisms affect roots

A

high concs of auxin inhibits cell elongation so root bends away from light

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11
Q

how do geotropisms affect shoots

A

auxin diffuses to underside of leaf

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12
Q

how do geotropisms affect roots

A

auxin moves to underside of root so upper side elongates and root bends towards gravity

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13
Q

what are auxins

A

cause cell elongation in stems and inhibit growth in roots, prevent leaves from dropping, maintain apical dominance

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14
Q

what are gibberellins

A

stimulate seed germination, stem elongation, and pollen tube growth in fertilisation

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15
Q

what does ethene do

A

fruit ripening

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16
Q

what is aba

A

stimulates stomatal closure and maintains dormancy of seeds

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17
Q

where are auxins made

A

tips of roots and shoots, and in meristem

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18
Q

what is apical dominance

A

growth of one main shoot and inhibition of lateral shoot growth

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19
Q

what is the evidence for apical dominance caused by auxins

A

removal of apical shoot causes rapid growth of lateral shoots, artificial application of auxin to shoot suppresses growth of lateral shoots

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20
Q

what happens in high concentrations of auxins in roots

A

inhibits root growth

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21
Q

how do gibberellins cause seed germination

A

cause the release of enzymes that break down food stores in seed (so embryo plant can use food to make atp) by switching on genes which code for proteases and amylases

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22
Q

what is the evidence for the role of gibberellins in seed germination

A

plant seeds without gene for gibberellins did not germinate until exposed to artificial gibberellins

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23
Q

what is the evidence for the role of gibberellins in stem elongation

A

dwarf varieties have low levels, grow to normal height with artificial gibberellins

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24
Q

how are plant hormones used commercially

A

ethene controls fruit ripening, auxins used in rooting powders to encourage plant cuttings to grow, auxins used as weed killers by causing rapid growth

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25
Q

what is the central nervous system

A

brain and spinal cord

26
Q

what is the peripheral nervous system

A

other neurones linking cns to body

27
Q

what is the somatic nervous system

A

under conscious control

28
Q

what is the autonomic nervous system

A

involuntary

29
Q

what is the sympathetic nervous system

A

fight or flight response (noradrenaline)

30
Q

what is the parasympathetic nervous system

A

relaxing responses (acetylcholine)

31
Q

where is the cerebrum and what is its function

A

4 lobes, receives sensory information and coordinates responses

32
Q

where is the cerebellum and what is its function

A

top of spine
controls muscular movement, body posture and balance

33
Q

where is the hypothalamus and what is its function

A

centre of brain
regulates temp and water, main control centre for ans

34
Q

where is the pituitary gland and what is its function

A

underneath hypothalamus
stores and releases hormones

35
Q

what is the difference between the anterior and posterior pituitary gland

A

anterior- growth and reproduction
posterior- hormones from hypothalamus eg adh

36
Q

where is the medulla oblongata and what is its function

A

top of brain stem
regulates heart beat, breathing etc

37
Q

what is a reflex action

A

an involuntary response to a sensory stimulus

38
Q

how does the knee jerk reflex happen

A

stimulus causes the thigh muscle to contract while the relay neurone inhibits the motor neurone
contradiction causes the leg to kick

39
Q

what is the survival importance of reflex actions

A

avoids harm, brain can deal with complex responses without being overloaded

40
Q

what are the 3 types of muscle

A

skeletal- movement
cardiac- heart
smooth- walls of organs and blood vessels

41
Q

describe the structure and function of skeletal muscle

fibre appearance, control, arrangement, contraction speed and length

A

striated, conscious, regular contraction in one direction, rapid, short, tubular and multinucleated

42
Q

describe the structure and function of cardiac muscle

fibre appearance, control, arrangement, contraction speed and length

A

specialised striated, involuntary, simultaneous contraction, intermediate, intermediate, branched and uninucleated

43
Q

describe the structure and function of smooth muscle

fibre appearance, control, arrangement, contraction speed and length

A

smooth, involuntary, no regular arrangement, slow, long, spindle shaped and uninucleated

44
Q

what is the sarcolemma

A

the plasma membrane of muscle fibres

45
Q

what is the sarcoplasm

A

the shared cytoplasm between muscle cells

46
Q

what is the sarcoplasmic reticulum

A

the specialised endoplasmic reticulum of muscle fibres

47
Q

what do muscle fibres contain

A

myofibrils

48
Q

what are myofibrils

A

long cylindrical organelles made of proteins and specialised for contraction

49
Q

what do myofibrils contain

A

actin- thinner, 2 twisted strand
myosin- thicker, rod shaped with bulbous heads

50
Q

what are the bands of myofibrils

A

I- only actin
A- actin and myosin overlap
H- only myosin
Z- centre of I

51
Q

what is a sarcomere

A

distance between Z lines

52
Q

what happens at a neuromuscular junction when an action potential reaches it

A

sarcolemma becomes depolarised, sarcoplasmic reticulum releases ca2+, muscle contracts

53
Q

what happens in the muscle to cause it to contract (sliding filament theory)

A

ca2+ binds to troponin, causes change in shape, tropomyosin reveals binding site, myosin head binds to actin to form cross bridge, actin slides along myosin and releases adp, atp binds to head, detaches from actin, ca2+ activates atpase in sarcoplasm to hydrolyse atp into adp so head resumes original position

54
Q

what is tropomyosin

A

blocks myosin binding site on actin during relaxation

55
Q

how is atp regenerated

A

phosphocreatine provides phosphate to adp

56
Q

what happens to bands during contraction

A

I and H become narrower, Z move closer

57
Q

describe the fight or flight response

A

ans detects threat and sends impulse to hypothalamus, sympathetic nervous system and adrenal cortical system stimulated, adrenaline and noradrenaline released triggering release of adrenocorticotropic hormone from pituitary

58
Q

how is heart rate controlled hormonally

A

adrenaline increases heart rate, stroke vol and cardiac output

59
Q

how is heart rate controlled nervously

A

cardiovascular centre in medulla oblongata connected via accelerator (increases) and vagus (decreases) nerves

60
Q

how is heart rate controlled homeostatically

A

chemoreceptors (pH) stimulate increase when pH increases
baroreceptors (pressure) stimulate decrease when blood pressure increases

Biology (25 decks)

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