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LGS A-Level OCR Biology > Unit 5 - Plant & Animal Responses > Flashcards

Unit 5 - Plant & Animal Responses Flashcards

1
Q

Nastic responses

A

Plant responses in which the direction of the plant response is independent of the stimulus

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2
Q

Herbivory

A

Consumption of plants

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3
Q

Abiotic

A

Physical

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4
Q

Tropisms

A

Directional growth responses in plants

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5
Q

Phototropisms

A

Influenced by light e.g. plants grow towards light to photosynthesise due to auxin moving unilaterally

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6
Q

Geotropism

A

Influenced by gravity
Plants recieve unilateral gravitational stimulus (downwards)
Shoots are -vely geotropic and roots are +vely geotropic

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7
Q

Thigmotropism

A

Influenced by touch

Shoots of climbing plants e.g. ivy winding around other plants or solid structures for support

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8
Q

Chemotropism

A

Influenced by chemicals

Pollen tubes grow down the style of a plant towards the ovary where fertilisation takes place

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9
Q

Plant hormones

A 
Cytokinins
Abscisic acid (ABA)
Auxins
Giberellins 
Ethene
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10
Q

Effects of cytokinins

A

Promote cell divison
Delay leaf senescence - increases shelf life
Overcome apical dominance - lateral growth
Promote cell expansion

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11
Q

ABA

A

Inhibit seed germination and growth
Stimulate cold protective responses
Cause stomatal closure when the plant is stressed by low water availability

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12
Q

Effect of auxins

A

Promote cell elongation in roots - low conc
Promote shoot growth/ demote root growth - high conc
Inhibit growth of side shoots
Inhibit leaf abscission
Selective weedkiller
Promote cell division in cambium

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13
Q

Effect of gibberellins

A

Promote seed germination - break bud dormancy (works against ABA)
Promote growth of stems - elongation of internodes
Develop seedless fruit and fruit setting
Acts synergistically w/ auxin

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14
Q

Effect of ethene

A

Promote fruit ripening - starch to sugar and breaks down chlorophyll and cell wall
Stimulates cells in abscission zone to expand and breaks cell wall causing leaf to fall off
Opp to auxin

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15
Q

How do plants avoid herbivores

A

Tannins - phenolic compounds; toxic to herbivores and microorganisms
Alkaloids - make plants taste bitter
Mimosa leaves fold up in response to touch - scares insects

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16
Q

Abscission in deciduous plants

A

Decreases production of auxin
More sensitive to ethene
Gene expression of enzymes in abcission zone
Cellulase breaks down cell walls in separation layer of abscission zone
Vascular bundles sealed off, fatty materials for neat, waterproof scar

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17
Q

Mechanism of seed germination

A

Seed absorbs H2O and activates embryo
Begins to produce gibberellins
Gene expression –> produces amylases and proteases to break down starch food stores
Glucose is used as a respiratory substrate and in protein synthesis

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18
Q

Mechanism of stomatal closure

A 
Levels of soil water falls
Roots produce ABA
Transported and binds to guard cells 
Increases pH, charged particles move out 
Increases wp, water moves out 
Loss of turgor closes stoma
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19
Q

Proof of gibberellins causing seed germination

A

Mutant varieties that lack gibberellin do not germinate but w/ external gibberellin they do
When gibberellin inhibitors are addeed to normal seeds they dont grow

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20
Q

Apical Dominance Effect

A

Auxin produced at the apex, inhibits growth of lateral buds

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21
Q

Experimental evidence for apical dominance

A

Removal of apical buds allows lateral bud to grow
Auxin/synthetic auxin placed on cut tip continues to inhibit the growth of side shoots

Plant 30 plants of same type, age, genotype and weight in same soil
Remove tip of 10 and apply auxin paste
Remove tip of another 10 and add paste w/out auxin
Leave last 10 as control
Sig. increase of no. of side shoots grown in first 10

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22
Q

Recent research on apical dominance

A

Auxin stimulates production of ABA (inhibits growth)
When apex is removed as is the source of auxin, ABA levels decrease
Most cytokinins go to tip so when tip is removed cytokinins spread evenly around plant promoting growth

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23
Q

Where does growth occur in plants

A

Apical meristems

Lateral bud meristems

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24
Q

Mechanism of cell elongation by auxin

A 
Tip produces auxins, diffuses down 
Promotes active transport of H+ into cell walls
Lowers pH, optimum pH for expansins
Breaks H bonds within cellulose
Reduces rigidity and H2O enters
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25
Confirming auxin as the hormone that causes growth
Impregnated agar blocks w/ diff conc. of auxin Placed them on cut shoot tips Same effects as in reg. shoots Curvature is directly proportional to conc of auxin used
26
Research supporting geotropism in shoots
Plants are grown on a slowly rotating drum (clinostat) so gravitational stimulus is applied evenly Plants grow straight in both light and dark
27
Research supporting geotropism in roots
Seeds are placed in petri dishes w/ moist cotton wool that are rotated 90 degrees as seedlings grow Cover lid w/ oil - ensure no light is coming in All petri dishes should be in same environment Geotropic response in the roots can be seen every 2 hours
28
Investigating role of gibberellin in stem elongation
Plant 40 plants Water 20 plants normally Water other 20 w/ diluted solution of gibberellins Let all 40 grow for 28 days, measuring height every 7 Calculate rate at which plants grew
29
IAA
Natural form of auxin responsible for +ve phototropism so plant bends towards light to phostosynthesise and grow taller and grows roots to reach water and nutrients Light stimulus detected by tip of plant
30
Central nervous system
Brain and spinal cord Mostly relay neurones in brain Mostly non-myelinated in brain and myelinated in spinal cord
31
Role of peripheral nervous system
Ensure rapid comm between the sensory receptors, CNS and effectors
32
Divisions of PNS
Sensory nerous systems | Motor nervous system
33
Sensory nervous system
Neurons conduct action potentials from the sensory receptor into the CNS
34
Divisions of motor nervous system
Autonomic | Somatic
35
Somatic nervous system
Motor neurones that conduct action potentials to effectors that are under voluntary control e.g. skeletal muscles Mostly myelinated neurones One single motor neuone connecting CNS to effector
36
Autonomic nervous system
Motor neurones that conduct action potentials to effectors that arent under voluntary control e.g. cardiac muscles Mostly unmyelinated neurones At least two motor neurones involved - connected at ganglia
37
Divisions of autonomic nervous system
Sympathetic | Parasympathetic
38
Ganglia in sympathetic system
Outside CNS, near spinal cord
39
Ganglia in parasympathetic system
Closer to effector tissue
40
Neurones in sympathetic system
Short pre-ganglionic neurones | Long post-ganglionic neurones
41
Neurones in parasympathetic system
Long pre-ganglionic neurones | Short post-ganglionic neurones
42
Neurotransmitter in sympathetic system
Noradrenaline
43
Neurotransmitter in parasympathetic system
Acetylcholine
44
Four sections of the brain
Cerebrum Cerebellum Medulla Oblongata Hypothalamus and pituitary complex
45
Cerebrum
Largest part of human brain Two hemispheres connected by corpus callosum Involved in control of speech and higher thought processes e.g. planning a task
46
Cerebral cortex
Highly folded Outer part of cerebrum Involved in higher thought e.g. overriding reflexes, conscious thought, intelligence and reasoning
47
What is the cerebral cortex divided into
Sensory areas - recieve impulses from sensory neurones Motor areas - send impulses out to effectors Association areas - link info and coordinate approriate respnse
48
Cerebellum
Controls muscular movement and balance Connected to cerebrum by pons Coordination of posture
49
Medulla oblongata
Controls involuntary processes e.g. heart rate and breathing rate Has specialised centres that recieve info from internal receptors and adjust breathing and heart rate accordingly
50
Hypothalamus and pituitary complex
Organises homeostatic responses and controls various physiological processes Info is recieved from hypothalamus and hormones are released via the pituitary gland (controls endocrine system)
51
Reflex reactions
Responds to changes in the environment but not involving the brain Sensory --> relay --> motor Brain may be informed but doesn't coordinate Survival; fast, involuntary and not learned (innate)
52
Cranial reflex
Nervous pathway passes through the brain
53
What makes something an reflex arc
Receptor and effector in same place
54
Blinking reflex
Cranial reflex Corneal - object toucing eyes Optical - Light hitting back of eye (retina)
55
Patnway for corneal blinking reflex
Receptor Sensory neurone on cornea Sensory centre on pons Non-myelinated relay neuron passes action potential to motor neurone Motor neurone passes out of brain to facial muscles
56
If the corneal blinking reflex is to be overridden
Sensory neurone on cornea Myelinated relay neurones inform brain Allows reflex to be overriden (inhibitory neurone) - faster so reflex can be overriden before it happens
57
Knee-jerk reflex
Spinal reflex Unexpected stretching of quadraceps --> detected by muscle spindles --> causes a reflex reaction (no relay neurone) --> quadraceps contract
58
Spinal reflex
Involves the spinal chord rather than the brain
59
Muscle spindles
Stretch receptors that detect increase in muscle length
60
Class of hormones
Steroid - produced in reproductive organs and adrenal cortex Peptide - insulin, ADH, adrenaline
61
Hypothalamic - anterior axis
Hypothalamus releases hormones (releasing factors) Pass down a portal vessel to anterior pituitary gland Anterior pituitary gland releases tropic hormones e.g. for thyroid and adrenal
62
Tropic hormones
These stimulate other endocrine glands
63
Mechanism of steroid hormones
Steroid hormone combines w/ steriod receptor in cytoplasm Hormone-receptor complex enters nucleus Complex binds to receptor sites on DNA, activating mRNA transcription mRNA leaves nucleus Ribosome translates mRNA into new protein in cytoplasm
64
Mechanism of peptide hormones
Adrenaline in the blood binds to membrane bound receptor Stimulates G-protein to activate Adenyl cyclase Converts ATP to cAMP cAMP acts as second messenger by moving into the cell cytoplasm and causing an effect
65
Thyroxin
Increases metabolic rate in most cells
66
How is thryoxin released
Hypothalamus releases TRH Travels to anterior pituitary gland and releases TSH Travels to thyroid through portal vessel and releases thyroxine
67
TRH
Thyrotropin releasing hormone
68
TSH
Thyroid stimulating hormone
69
How are glucocorticoids (cortisol) released
Hypothalamus releases CRH Travels to anterior pituitary gland and releases ACTH Travels to adrenal cortex through portal vessel and releases cortisol
70
Cortisol
Released as a response to chronic stress | Stimlates breakdoen of glycogen
71
Coordination of flight or fight
Sensory input Action potential travels to sensory centres (cerebrum) Signals passed to association areas If a threat is recognised, cerebrum stimulates hypothalamus Hypothalamus stimulates symapthetic nervous system and stimulates release of hormones from anterior pituitary gland
72
How is the fight or flight response formed
Hypothalamus activates sympathetic nervous system Impulses activate glands and smooth muscle Activated adrenal medulla Secretion of adrenaline into the bloodstream Hypothalamus also secretes releasing factors e.g. CRH and TRH
73
CRH
Corticotropic releasing hormone
74
ACTH
Adrenocorticotropic hormone
75
Physiological changes in fight or flight response
Pupils dilate - more light enters eyes, retina becomes more sensitive Heart rate and bp increase Ventilation depth and rate increases Less digestion Blood glucose increases Metabolic rate increase - faster coversion of glucose to ATP Endorphins released in brain Erector pili muscles in the skin contract
76
Why do erector pili muscles stand up in fight or flight response
Hairs/ fur stands up - signs of aggression
77
Why are endorphins released in the fight or flight response
Wounds inflicted don't prevent activity
78
Why must plants be able to respond to their environment
Cope w/ changing conditions | Avoid antibiotic stress
79
How does auxin cause cell elongation (2 marks)
Loosens rigid cellulose framework | Osmotic uptake of water allows cell elongation
80
Why do cut plants w/ agar blocks w/ auxin placed on the rhs bend to the lhs
Auxin produced at tip Diffuses laterally to rhs Cells on rhs exhibit greater elongation Bending to the left
81
How does auxin act as a selective weedkiller
Rapid cell elongation so plant grows too quickly No extra lignified tissue Stem collapses or loss of extra water from leaves
82
What happens when the apex is removed from a plant
Once apex is removed, auxin production stops Apical dominance is stopped Lateral growth is not inhibited and lateral buds develop
83
Types of muscle
Skeletal (voluntary) Cardiac Involuntary (smooth)
84
Voluntary (skeletal muscle)
``` Striated Multinucleate Regularly arranged —> contraction in one direction Attached to bone by tendon Tubular Nerves from peripheral, somatic (rapid) ```
85
Cardiac muscle
Specialised striated (parallel myofibrils) Branched fibres Uninucleated Cross bridges allow simultaneous contraction Dark bands - intercalated discs Nerves from autonomic nervous system
86
Involuntary (smooth muscle)
Non striated Nerves from autonomic nervous system No reg. arrangement - diff cells can contract in diff directions Fibres are spindle shaped and uninucleated Used in hollow organs (peristalsis)
87
Sarcolemma
Plasma membrane that encloses bundles of muscle fibre
88
Why may the sarcolemma fold in
Spread impulse throughout sarcoplasm | Contract at the same time
89
Sarcoplasm
Shared cytoplasm within muscle fibres
90
How are muscle fibres formed
Fusion of several embryonic muscle cells - gap between adjacent cells would be a weakness (That’s why it’s multinucleate)
91
Sarcoplasmic reticulum
Modified version of ER | Provides strength and stored Ca^2+
92
Protein filaments
Myosin | Actin
93
Muscle organisation
``` Muscle Fascicles Muscle fibres Myofibrils Protein filaments ```
94
Connective tissue
Tendons
95
Light band (I)
Thin actin held together by Z line
96
Dark band (A)
Both actin and myosin Entire length of myosin Myosin held together by M line
97
M line
Midpoint of myosin | Has no heads
98
Z line
Found at the centre of each light band
99
Sarcomere
Functional unit of muscle From one Z line to another Sub unit of myofibrils
100
Why is muscle considered a tissue
Muscle fibre Blood vessels Nerves Connective cells
101
Characteristics of sliding filament model
Z lines get closer Sarcomeres shortens I band narrows H zone narrows
102
What does simultaneous contraction of several sarcomeres allow
Myofibrils and then muscle fibres to contract —-> enough to pull a bone
103
Neuromuscular junction
Action potential arriving at axon of motor neurone opens VG Ca2+ to flood into tip Vesicles of acetylcholine to move towards membrane & fuse Acetylcholine diffuses across synapse and binds to receptors on sarcolemma Na+ channels open and wave of depolarisation passes down transverse tubules Passes to SR which releases Ca2+ into the sarcoplasm
104
Cross bridge muscle contraction cycle
Tropomyosin is blocking myosin binding site in actin Ca2+ binds to troponin causing a conformational change, tropomyosin moves Myosin heads bind to actin, forming cross bridges between filaments Myosin heads move, pulling the actin filament. ADP and Pi are released during the power strike A new ATP molecule attaches to myosin head, breaking cross bridge ATP hydrolyses and myosin head returns to its orig. position
105
Where does SR get Ca^2+
Active absorption from sarcoplasm
106
Supply of ATP for muscular contraction
Aerobic respiration - oxidative phosphorylation Anaerobic respiration - glycolysis Glycogen —> glucose Creatine phosphate can combine w/ ADP to form ATP
107
Where is creatine phosphate found
Sarcoplasm
108
Supply of energy of slow twitch muscle
Aerobic respiration
109
Supply of energy for fast twitch muscle
Anaerobic respiration
110
Where is the cardiovascular centre
Medulla oblongata - this alters the excitation wave frequency
111
Frequency of heart excitation
60-80 bpm
112
What is the heart rate regulated by
SAN | Nerves connect cardiovascular centre to the SAN
113
Nerves involved in controlling heart rate
Accelerans | Vagus
114
Accelerans
``` Causes release of noradrenaline at SAN Increases HR (sympathetic) ```
115
Vagus nerves
Causes release of acetylcholine at SAN, reduces HR (parasympathetic)
116
Sensory inputs that increase HR
Increased muscle movement (muscle stretch receptors) Decrease in pH (chemoreceptors) Adrenaline in blood
117
Sensory inputs that decrease HR
Increase in bp (stretch receptors - carotid sinus) | Decrease in dissolved CO2 (chemoreceptors)
118
Why do plants kept in the dark grow taller than those in the light
Auxin is more present in the dark
119
Plant growth substances vs animal hormones
Hormones travel faster in animals Synthesised in endocrine glands vs cells sites Slow acting in plants vs fast acting in animals
120
Why is temp controlled in investigations on effect of plant hormones
So temp does not affect results as temp affects enzyme activity
121
Why are monkeys used for human research
Closely related Both primates Similar physiology
122
Actions of parasympathetic nervous system
``` Increases blood flow to digestive system, allows peristalsis Decreases HR Decreases airway diameter Sexual arousal Constricts pupils ```
123
Why is glycogen found in striated muscle
Glycogenolysis Glucose can undergo glycolysis to produce ATP Energy storage
124
Uses of mitochondria in muscular contraction
ATP attaches to ATPase on the myosin head Hydrolysis to release ADP and Pi during power stroke, allows myosin heads pull the actin filaments Needed for myosin head to detach Protein synthesis Ca 2+ pumps in SR
125
Internal organs affected by SNS/PNS
Heart Lungs Liver Intestines
126
How is the heart affected in the PNS/SNS
Slow HR vs. fast HR
127
How are the lungs affected by the PNS/SNS
Shallow breaths vs deep breaths
128
How is the liver affected by the PNS/SNS
Glucose take up (glycogenesis) vs glucose used up (glycolysis)
129
How is the stomach affected by the PNS/SNS
More peristalsis vs. less
130
How does the SNS affect smooth muscle
``` Alters blood flow to increase bp Vasoconstriction Peristalsis slows down Relaxes in airways (increases diameter) Pupils dilate ```
131
How does the SNS affect cardiac muscle
Heart beats faster | Beats w/ more force
132
How does SNS affect voluntary muscles
Glycogenolysis in muscles for priming Diaphragm contracting faster More blood flow to skeletal muscle --> respiration
133
Long term effects of chronic stress
Cardiovascular problems due to high bp | Suppression of immune system leads to susceptibility to disease
134
Photoperiodism
Plants' sensitivity to a lack of light, affects several diff plant responses e.g. flowering
135
Phytochrome
Light sensitive pigment that affects the sensitivity of plants to light Exists in two forms, Pt and Pft
136
How do plants prevent freezing
Cytoplasm and vacuole contain sap that lowers the freezing point Produce biological molecules (excluding lipids) to prevent cytoplasm freezing or protect cells from damage if they do freeze
137
Commercial uses of plant hormones
``` Ethene to control ripeneing Hormone rooting powders and micropropagation Auxin to produce seedless fruit Cytokinins to prevent aging Gibberellins to improve size and shape ```
138
Transverse tubules
Extensions into sarcolemma
139
Factors affecting stomatal closure
Temperature | Water availability
140
How does increases in temp affect stomata
Release of ABA decreases Stomata open Allows plant to cool through water evaporation
141
How does decrease in water availability affect stomatal
Increased release of ABA Stomata close Reduces water loss through transpiration
142
How do gibberellins cause stem elongation
Promote cell elongation - by loosening cell walls | Promote cell division - producing proteins that control the cell cycle

LGS A-Level OCR Biology (42 decks)

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