topic 5.1.5: plant and animal responses

Question 1

what are examples of abiotic stressors

Answer 1

high winds, excess or lack of water, temp changes

Question 2

give 5 plant responses to abiotic stress

Answer 2

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

Question 3

what is photoperiodism

Answer 3

sensitivity to lack of light

Question 4

how do plants carry out abscission on leaves

Answer 4

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

Question 5

how do plants respond to herbivory

Answer 5

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

Question 6

what are alkaloids

Answer 6

nitrogenous, bitter tasting chemicals eg nicotine

Question 7

what are pheromones

Answer 7

affect behaviour of other members of same species
vocs in plants

Question 8

what are tropisms

Answer 8

plant growth responses to stimuli from one direction

Question 9

how do phototropisms affect shoots

Answer 9

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

Question 10

how do phototropisms affect roots

Answer 10

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

Question 11

how do geotropisms affect shoots

Answer 11

auxin diffuses to underside of leaf

Question 12

how do geotropisms affect roots

Answer 12

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

Question 13

what are auxins

Answer 13

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

Question 14

what are gibberellins

Answer 14

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

Question 15

what does ethene do

Answer 15

fruit ripening

Question 16

what is aba

Answer 16

stimulates stomatal closure and maintains dormancy of seeds

Question 17

where are auxins made

Answer 17

tips of roots and shoots, and in meristem

Question 18

what is apical dominance

Answer 18

growth of one main shoot and inhibition of lateral shoot growth

Question 19

what is the evidence for apical dominance caused by auxins

Answer 19

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

Question 20

what happens in high concentrations of auxins in roots

Answer 20

inhibits root growth

Question 21

how do gibberellins cause seed germination

Answer 21

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

Question 22

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

Answer 22

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

Question 23

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

Answer 23

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

Question 24

how are plant hormones used commercially

Answer 24

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

Question 25

what is the central nervous system

Answer 25

brain and spinal cord

Question 26

what is the peripheral nervous system

Answer 26

other neurones linking cns to body

Question 27

what is the somatic nervous system

Answer 27

under conscious control

Question 28

what is the autonomic nervous system

Answer 28

involuntary

Question 29

what is the sympathetic nervous system

Answer 29

fight or flight response (noradrenaline)

Question 30

what is the parasympathetic nervous system

Answer 30

relaxing responses (acetylcholine)

Question 31

where is the cerebrum and what is its function

Answer 31

4 lobes, receives sensory information and coordinates responses

Question 32

where is the cerebellum and what is its function

Answer 32

top of spine controls muscular movement, body posture and balance

Question 33

where is the hypothalamus and what is its function

Answer 33

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

Question 34

where is the pituitary gland and what is its function

Answer 34

underneath hypothalamus stores and releases hormones

Question 35

what is the difference between the anterior and posterior pituitary gland

Answer 35

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

Question 36

where is the medulla oblongata and what is its function

Answer 36

top of brain stem regulates heart beat, breathing etc

Question 37

what is a reflex action

Answer 37

an involuntary response to a sensory stimulus

Question 38

how does the knee jerk reflex happen

Answer 38

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

Question 39

what is the survival importance of reflex actions

Answer 39

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

Question 40

what are the 3 types of muscle

Answer 40

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

Question 41

describe the structure and function of skeletal muscle | fibre appearance, control, arrangement, contraction speed and length

Answer 41

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

Question 42

describe the structure and function of cardiac muscle | fibre appearance, control, arrangement, contraction speed and length

Answer 42

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

Question 43

describe the structure and function of smooth muscle | fibre appearance, control, arrangement, contraction speed and length

Answer 43

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

Question 44

what is the sarcolemma

Answer 44

the plasma membrane of muscle fibres

Question 45

what is the sarcoplasm

Answer 45

the shared cytoplasm between muscle cells

Question 46

what is the sarcoplasmic reticulum

Answer 46

the specialised endoplasmic reticulum of muscle fibres

Question 47

what do muscle fibres contain

Answer 47

myofibrils

Question 48

what are myofibrils

Answer 48

long cylindrical organelles made of proteins and specialised for contraction

Question 49

what do myofibrils contain

Answer 49

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

Question 50

what are the bands of myofibrils

Answer 50

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

Question 51

what is a sarcomere

Answer 51

distance between Z lines

Question 52

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

Answer 52

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

Question 53

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

Answer 53

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

Question 54

what is tropomyosin

Answer 54

blocks myosin binding site on actin during relaxation

Question 55

how is atp regenerated

Answer 55

phosphocreatine provides phosphate to adp

Question 56

what happens to bands during contraction

Answer 56

I and H become narrower, Z move closer

Question 57

describe the fight or flight response

Answer 57

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

Question 58

how is heart rate controlled hormonally

Answer 58

adrenaline increases heart rate, stroke vol and cardiac output

Question 59

how is heart rate controlled nervously

Answer 59

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

Question 60

how is heart rate controlled homeostatically

Answer 60

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