Plant and Animal Responses Flashcards
1
Q
Abiotic stresses that plants respond to
A
Daylength, falling temperatures, water availability
2
Q
How plants respond to changes in day length
A
Deciduous plants lose leaves, enter dormancy
3
Q
How plants know when to respond to changes in day length
A
The ratio of Pr and Pfr (Forms of phytochrome)
4
Q
What are Pr and Pfr examples of?
A
Phytochromes
5
Q
Photoperiodism
A
Sensitivity to lack of light in the environment
6
Q
Plant responses that are affected by photoperiodism
A
Breaking dormancy of leaf buds, timing of plant flowering, when tubers are formed
7
Q
Why do deciduous plants do leaf abscission?
A
The temperature is so low that the amount of glucose required for respiration in the leaves and to produce chemicals to prevent freezing is greater than the amount produced by photosynthesis
8
Q
How do plants do leaf abscission?
A
Falling light levels decrease the concentration of auxin, more ethene produced, ethene initiates the switching on of genes in the abscission zone to produce enzymes such as cellulase, cellulase digests the cell wall in the separation zone, vascular bundles sealed off, fatty material deposited into cells in protective layer which forms scar, cells in separation zone retain water, increases strain on separation zone, strain is too much, leaf falls
9
Q
How do plants respond to lower temperatures?
A
Cytoplasm and sap of plant cells contain solutes to lower freezing point
10
Q
How do plants respond to lower water availability?
A
Roots provide early warning system by producing ABA when there is less water, ABA transported to leaves, binds to receptors on plasma membrane of guard cells, causes changes in ionic concentration of guard cells, reduces water potential of cells, guard cells lose turgor, stomata close
11
Q
Type of plant responses to herbivory
A
Physical, chemical, pheromones, folding in response to touch
12
Q
Physical plant responses to herbivory
A
Thorns, barbs, spikes, spiny leaves, fibrous tissue, inedible tissue, hairy leaves, stings
13
Q
Chemical plant responses to herbivory
A
Tannins, alkaloids, terpenoids
14
Q
How do tannins protect plants against herbivory?
A
Bitter tasting, toxic to insects
15
Q
Why are tannins toxic to insects?
A
Bind to digestive enzymes and inactivate them
16
Q
How do alkaloids protect plants against herbivory?
A
Bitter tasting, affecting metabolism of animals
17
Q
Examples of alkaloids protecting plants against herbivory
A
Caffeine produced by coffee bush seedlings is toxic to fungi and insects, caffeine prevents germination of seeds of other plants, nicotine produced by tobacco plants is a toxin stored in vacuoles
18
Q
How do terpenoids protect plants against herbivory?
A
Toxins to insects and fungi
19
Q
Examples of terpenoids protecting plants against herbivory
A
Pyrethrin from chrysanthemums is an insect neurotoxin, citronella from lemon grass is an insect repellent
20
Q
Pheromone
A
Chemical made by an organism which affects the social behaviour of other members of the same species
21
Q
Examples of pheromones being used to protect plants against herbivory
A
Maple trees attacked by insects release a pheromone which is absorbed by leaves on other branches which can then prepare
22
Q
Plant version of pheromones
A
Volatile organic compounds
23
Q
How VOCs work
A
Made when plant defences detected chemicals in insect saliva, elicit gene switching
24
Q
Examples of VOCs protecting plants against herbivory
A
Cabbages can produce a signal which attracts parasitic wasps which eats the caterpillar eggs, signal deters other butterflies from laying their eggs, apple trees do the same things, wheat seedlings produce signals that repel aphids when attacked
25
Example of a plant that folds in response to touch
Mimosa pudica
26
How do Mimosa podia fold in response to touch?
Touch initiates an action potential, spreads to the base of each petiole, pulvinus is at the base of each petiole, action potential causes K+ and Cl- ions to leave the extensor side of the pulvinus and move into the flexor side, opens voltage gated channels, water leaves the extensor side by osmosis, cells become flaccid on the extensor side and turgid on the flexor side, pulvinus can't support weight of the leaf, leaf droops
27
Examples of plant tropisms
Phototropism, geotropism, thigmotropism, chemotropism
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Tropism
A directional growth response
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Phototropism
Response to light
30
Geotropism
Response to gravity
31
Chemotropism
Response to chemicals
32
Thigmotropism
Response to touch
33
How phototropism works
Light causes the auxin to move laterally across the shoot, greater concentration on unilluminated side, stimulates cell elongation and growth on the dark side
34
Practical investigations into phototropism
Grow seedlings in different light conditions and use time-lapse photography to observe the changes, grow in unilateral light with different colour filters to see which wavelengths result in the greatest response,
35
Which kind of organisms are used to study tropisms?
Germinating seeds and young seedlings of monocotyledonous
36
Why are germinating seeds and young seedlings used to study tropisms?
Easy to work with, changes affect the whole organism, seedlings of monocotyledonous have a single spike with no leaves known as a coleoptile
37
Practical investigations into geotropisms
Place a plant in a clinostat which is rotating and the plant will grow straight, seeds placed in petri dishes stuck to walls of lab and roots show geotropism
38
How hormones are involved in seed germination
Seeds absorb water, embryo activated, gibberellins produce, production of enzymes to break down food stores stimulated, food stores used to make ATP, ABA is antagonistic to gibberellins
39
How do gibberellins stimulate the production of enzymes?
Switch on genes for amylases and proteases
40
Where are the food stores in dicot seeds?
Cotyledon
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Where are the food stores in monocot seeds?
Endosperm
42
Role of auxins
Stimulate the growth of the main apical shoot, apical dominance, low concentration of auxins promote root growth
43
How do auxins stimulate the growth of the main apical shoot?
Auxin binds to specific receptor sites in the plant cell membrane, pH falls to 5, optimum pH for enzymes to keep walls flexible and plastic
44
How auxin does apical dominance?
Growth in the main shoot is stimulated by auxin produced at the tip so it grows quickly, lateral shoots inhibited by the hormone that moves back down the stem, further down the stem there is less auxin so the shoots grow more
45
Practical investigations into apical dominance
Apical shoot removed, lateral shoots grow faster, the application of artificial auxin to the cut apical shoot reasserts apical dominance
46
How do gibberellins cause stem elongation?
Affect the length of the internodes
47
Practical investigations into how gibberellins result in stem elongation
Plants infected by the fungus that produces gibberellins grow tall and thin, plants with short stems produce few or no gibberellins
48
Experimental evidence into how gibberellins affect seed germination
Mutant varieties which lack the gene that allows them to make gibberellins make seeds that don't germinate, gibberellins applied to the seeds cause them to germinate normally, gibberellin inhibitors cause the seeds to not germinate
49
How to investigate the effect of hormones on plant growth
Grow seeds hydroponically in serial dilutions of different hormones, apply different concentration to the cut ends of stems
50
What can plant hormones be used for commercially?
Controlling ripening, rooting powders, hormonal weed killers
51
How hormones are used to control ripening
Fruits can be harvested when they aren't ripe, greengrocers then spray them with ethene to cause them to ripen
52
How hormones are used in rooting powders
Auxin applied to cut shoots of cuttings to stimulate root production, increases chances of successful propagation
53
How hormones are used in hormonal weedkillers
Synthetic auxins can be used as weedkillers as they are absorbed by broad-leaved weeds, causing their growth rate to become unsustainable so they die
54
How is the mammalian nervous system organised structurally?
Central nervous and peripheral nervous systems
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Central Nervous System
Brain and spinal cord
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Peripheral nervous system
The neurones that connect the CNS to the body,
57
How is the mammalian nervous system organised functionally?
Somatic and autonomic nervous systems
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Somatic nervous system
System under conscious control, carries impulses to the muscles
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Autonomic nervous system
System under subconscious control, carries impulses to glands and smooth muscle and cardiac muscle
60
How is the autonomic nervous system organised?
Sympathetic and parasympathetic nervous systems
61
Gross structure of the brain
Protected by the skull, surrounded by meninges, five main areas
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Main areas of the brain
Cerebrum, cerebellum, medulla oblongata, hypothalamus, pituitary gland
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Functions of the cerebrum
To receive sensory information and interpret it with respect to previous experiences, to send impulses along motor neurones to act on the information, used to control both voluntary and involuntary responses
64
Structure of the cerebrum
Highly convoluted, split into two halves, has discrete areas for different functions, outer layer called cerebral cortex
65
How the cerebrum responds to sensory information
Sensory areas receive information from receptor cells in sense organs, information passed to association areas, impulses go into motor areas so impulses can be sent through motor neurones to move muscles
66
How is the brain able to judge distance and perspective?
Impulses from right side of the field of vision sent to left hemisphere, impulses from left side sent to right hemisphere, integration gives distance and perspective
67
Function of the cerebellum
To control muscle movement, body posture and balance.
68
How does the cerebellum work?
Receives information from balance organs, relays information to areas of the cerebral cortex
69
Function of the medulla oblongata
To control reflex activities as part of the autonomic nervous system, such as ventilation and heart rate
70
Function of the hypothalamus
Main controlling region for the autonomic nervous system, one centre for parasympathetic system, one centre for sympathetic system, controls complex behaviour patterns, monitors composition of blood plasma, produces hormones
71
Function of the pituitary gland
To control most of the glands in the body
72
Structure of the pituitary gland
Divided into anterior and posterior pituitary gland
73
Function of anterior pituitary gland
To produce hormones such as FSH
74
Function of posterior pituitary gland
To store and release hormones made by the hypothalamus such as ADH
75
Reflex arc
Receptor detects stimulus, creates action potential for sensory neurone, sensory neurone carries impulse to motor neurone within the spinal cord via a relay neurone, motor neurone carries impulse to effector
76
What type of reflex is the knee jerk reflex?
Spinal reflex
77
Spinal reflex
When the neural circuit only goes up to the spinal cord, not the brain
78
How does the knee jerk reflex work?
Leg tapped just below the patella, stretches the patellar tendon, initiates the reflex arc, extensor muscle on top of the thigh contracts, relay neurone inhibits motor neurone of the flexor muscle so it relaxes, contraction of the extensor muscle causes the leg to kick
79
What is the knee jerk reflex used for?
Maintaining posture and balance
80
Examples of reflex actions
Knee jerk, blinking
81
What type of reflex is the blinking reflex?
Cranial reflex
82
Optical reflex
Blinking as a reaction to overly bright light
83
Cranial reflex
A reflex that occurs in the brain
84
How does the blinking reflex work?
Irritation of the cornea triggers an impulse along the fifth cranial nerve, passes through a relay neurone in the lower brain stem, impulses then sent along branches of the seventh cranial nerve, results in the eyelids closing
85
Consensual response
Both things respond in the same way to a stimulus
86
Example of a consensual response
Blinking reflex
87
How do reflexes increase your chances of survival?
Involuntary responses so the brain can deal with more complex responses, not learnt so provide immediate protection, fast
88
Stressor
Stimulus that causes the stress response which causes wear and tear on the body's physical or mental resources
89
Fight or flight response
Full range of coordinated responses of animals to situations of perceived danger
90
What is the cause of the fight or flight response?
Shift in the balance of stimulation to increase activity of the sympathetic nervous system and a decrease in activity of the parasympathetic nervous system
91
How is the fight or flight response coordinated?
Hypothalamus activates sympathetic nervous system and the adrenal-cortical system by releasing CRF, sympathetic nervous system activates the adrenal medulla which releases adrenaline and noradrenaline, sympathetic nervous system leads to impulses that activate glands and smooth muscles, anterior pituitary gland releases ACTH which leads to the adrenal cortex which releases hormones
92
Hormones that are released by the adrenal cortex in the fight-or-flight response
Cortisol, corticosterone
93
Role of cortisol
To regulate metabolism and blood pressure responses to stress
94
Role of corticosterone
Regulates immune response and suppresses inflammatory reactions
95
How does adrenaline use cell signalling?
Binds to its receptor, activates inactive adenyl cyclase to make active adenyl cyclase which is an enzyme, ATP is then converted into cAMP, cAMP is the second messenger
96
How is the nervous system involved in increasing heart rate?
Centre in the medulla oblongata which increases heart rate sends impulses through the sympathetic nervous system in the accelerator nerve to the SAN
97
How is the nervous system involved in decreasing heart rate?
Centre in the medulla oblongata which decreases heart rate sends impulses through the parasympathetic nervous system in the vagus nerve to the SAN
98
Types of receptors involved in changing heart rate
Chemoreceptors, baroreceptors
99
How are chemoreceptors involved in increasing heart rate?
Decreases in blood pH are detected due to increased CO2 concentration so heart rate increases to get CO2 to the lungs faster
100
How are chemoreceptors involved in decreasing heart rate?
pH of the blood rises, detected by receptors in wall of the carotid arteries and aorta, reduction in frequency of impulses sent to the medulla oblongata, reduces frequency of impulses sent to the SAN
101
How are baroreceptors involved in decreasing heart rate?
Receptors in the aorta and carotid artery detect increase in blood pressure, impulses sent to medulla oblongata, medulla oblongata sends impulses along parasympathetic neurones to the SAN
102
Effect of hormones on heart rate
Adrenaline and noradrenaline increase heart rate, increase frequency of impulses produced by the SAN
103
Types of muscle present in the body
Skeletal, cardiac, smooth
104
Structure of skeletal muscle
Striated, regularly arranged so muscle contracts in one direction, tubular fibres, multinucleated fibres
105
Structure of cardiac muscle
Specialised striated, cells branch and interconnect, uninucleated fibres, fainter striations than skeletal muscle
106
Structure of smooth muscle
Non-striated, no regular arrangement, spindle-shaped fibres, uninucleated fibres
107
Functional structure of skeletal muscle
Under conscious control, rapid contraction, short contraction
108
Functional structure of cardiac muscle
No conscious control, intermediate contraction speed, intermediate contraction length
109
Functional structure of smooth muscle
No conscious control, slow contraction, can remain contracted for a relatively long time
110
Name for the membrane on skeletal muscle cells
Sarcolemma
111
Neuromuscular junction
Where a motor neurone and a skeletal muscle fibre meet
112
How contraction is set up at neuromuscular junctions
Action potential reaches junction, stimulates calcium ion channels to open, calcium ions diffuse into synaptic knob, synaptic vesicles fuse with presynaptic membrane, ACh released into synapse, binds to receptors on sarcolemma, opens sodium ion channels, depolarisation, spreads into muscle fibre down T tubules, calcium ion channels in the sarcoplasmic reticulum open, calcium ions flood into sarcoplasm
113
How muscles contract
Calcium ions bind to troponin, pulls on tropomyosin, exposes myosin binding sites on the actin, cross-bridges form between the actin and myosin, myosin head flexes and actin pulled along, molecule of ADP bound to head released, ATP molecule binds to the myosin head, head released from cross bridge, process repeats
114
Sliding filament model
When the muscle contracts, I band becomes very narrow, z lines become closer together, sarcomere shortens, H zone completely disappears
115
Structure of myosin
Globular hinged heads, heads have binding sites for actin and ATP
116
Structure of actin
Binding sites for myosin heads, covered by tropomyosin which is held in place by troponin
117
Role of ATP in muscle contraction
Movement of myosin heads, active transport of calcium ions into the sarcoplasmic reticulum
118
How ATP is generated in muscles
Aerobic respiration, anaerobic respiration, creatine phosphate
119
How does creatine phosphate help maintain the supply of ATP?
Reserve supply of phosphate which can combine with ADP, generates ATP rapidly but is used up quickly
120
Structure of skeletal muscle that you can see with a microscope
I bands contain just actin, A bands contain myosin and actin, H zone contains just myosin, Z lines are at the centre of each I band, M line is in centre of H zone
