topic 5.1.5: plant and animal responses Flashcards
what are examples of abiotic stressors
high winds, excess or lack of water, temp changes
give 5 plant responses to abiotic stress
leaf loss, daylength sensitivity, abscission, preventing freezing, stomatal closure
what is photoperiodism
sensitivity to lack of light
how do plants carry out abscission on leaves
light levels decrease, ethene switches on genes for enzymes which digest cell walls in separation layer, leaf falls and waterproof scar forms
how do plants respond to herbivory
physical defences eg thorns
chemical defences eg alkaloids and pheromones
folding in response to touch
what are alkaloids
nitrogenous, bitter tasting chemicals eg nicotine
what are pheromones
affect behaviour of other members of same species
vocs in plants
what are tropisms
plant growth responses to stimuli from one direction
how do phototropisms affect shoots
shoot tips produce auxin, causing cell elongation
auxin diffuses to other cells on shaded side so plant bends towards light
how do phototropisms affect roots
high concs of auxin inhibits cell elongation so root bends away from light
how do geotropisms affect shoots
auxin diffuses to underside of leaf
how do geotropisms affect roots
auxin moves to underside of root so upper side elongates and root bends towards gravity
what are auxins
cause cell elongation in stems and inhibit growth in roots, prevent leaves from dropping, maintain apical dominance
what are gibberellins
stimulate seed germination, stem elongation, and pollen tube growth in fertilisation
what does ethene do
fruit ripening
what is aba
stimulates stomatal closure and maintains dormancy of seeds
where are auxins made
tips of roots and shoots, and in meristem
what is apical dominance
growth of one main shoot and inhibition of lateral shoot growth
what is the evidence for apical dominance caused by auxins
removal of apical shoot causes rapid growth of lateral shoots, artificial application of auxin to shoot suppresses growth of lateral shoots
what happens in high concentrations of auxins in roots
inhibits root growth
how do gibberellins cause seed germination
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
what is the evidence for the role of gibberellins in seed germination
plant seeds without gene for gibberellins did not germinate until exposed to artificial gibberellins
what is the evidence for the role of gibberellins in stem elongation
dwarf varieties have low levels, grow to normal height with artificial gibberellins
how are plant hormones used commercially
ethene controls fruit ripening, auxins used in rooting powders to encourage plant cuttings to grow, auxins used as weed killers by causing rapid growth
what is the central nervous system
brain and spinal cord
what is the peripheral nervous system
other neurones linking cns to body
what is the somatic nervous system
under conscious control
what is the autonomic nervous system
involuntary
what is the sympathetic nervous system
fight or flight response (noradrenaline)
what is the parasympathetic nervous system
relaxing responses (acetylcholine)
where is the cerebrum and what is its function
4 lobes, receives sensory information and coordinates responses
where is the cerebellum and what is its function
top of spine
controls muscular movement, body posture and balance
where is the hypothalamus and what is its function
centre of brain
regulates temp and water, main control centre for ans
where is the pituitary gland and what is its function
underneath hypothalamus
stores and releases hormones
what is the difference between the anterior and posterior pituitary gland
anterior- growth and reproduction
posterior- hormones from hypothalamus eg adh
where is the medulla oblongata and what is its function
top of brain stem
regulates heart beat, breathing etc
what is a reflex action
an involuntary response to a sensory stimulus
how does the knee jerk reflex happen
stimulus causes the thigh muscle to contract while the relay neurone inhibits the motor neurone
contradiction causes the leg to kick
what is the survival importance of reflex actions
avoids harm, brain can deal with complex responses without being overloaded
what are the 3 types of muscle
skeletal- movement
cardiac- heart
smooth- walls of organs and blood vessels
describe the structure and function of skeletal muscle
fibre appearance, control, arrangement, contraction speed and length
striated, conscious, regular contraction in one direction, rapid, short, tubular and multinucleated
describe the structure and function of cardiac muscle
fibre appearance, control, arrangement, contraction speed and length
specialised striated, involuntary, simultaneous contraction, intermediate, intermediate, branched and uninucleated
describe the structure and function of smooth muscle
fibre appearance, control, arrangement, contraction speed and length
smooth, involuntary, no regular arrangement, slow, long, spindle shaped and uninucleated
what is the sarcolemma
the plasma membrane of muscle fibres
what is the sarcoplasm
the shared cytoplasm between muscle cells
what is the sarcoplasmic reticulum
the specialised endoplasmic reticulum of muscle fibres
what do muscle fibres contain
myofibrils
what are myofibrils
long cylindrical organelles made of proteins and specialised for contraction
what do myofibrils contain
actin- thinner, 2 twisted strand
myosin- thicker, rod shaped with bulbous heads
what are the bands of myofibrils
I- only actin
A- actin and myosin overlap
H- only myosin
Z- centre of I
what is a sarcomere
distance between Z lines
what happens at a neuromuscular junction when an action potential reaches it
sarcolemma becomes depolarised, sarcoplasmic reticulum releases ca2+, muscle contracts
what happens in the muscle to cause it to contract (sliding filament theory)
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
what is tropomyosin
blocks myosin binding site on actin during relaxation
how is atp regenerated
phosphocreatine provides phosphate to adp
what happens to bands during contraction
I and H become narrower, Z move closer
describe the fight or flight response
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
how is heart rate controlled hormonally
adrenaline increases heart rate, stroke vol and cardiac output
how is heart rate controlled nervously
cardiovascular centre in medulla oblongata connected via accelerator (increases) and vagus (decreases) nerves
how is heart rate controlled homeostatically
chemoreceptors (pH) stimulate increase when pH increases
baroreceptors (pressure) stimulate decrease when blood pressure increases
