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Biology > 5.1.5 - PLANT + ANIMAL RESPONSES > Flashcards

5.1.5 - PLANT + ANIMAL RESPONSES Flashcards

1
Q

What is herbivory?

A

Plants being eaten by animals (herbivory)

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2
Q

Explain how plants respond to herbivory

A

Have chemical defences

  • Pheromones - chemicals released by a species to affect another organism in the same species (e.g. ETHENE causing ripening of fruit in nearby plants)
    ^— ETHENE also toxic to insects
  • Alkaloids - chemicals with bitter tastes, noxious smells or poisonous characteristics that deter/kill herbivores (e.g. tobacco plants produce alkaloid NICOTINE in response to tissue damage)
  • Tannins - bitter tasting | can bind to proteins in the gut in some herbivores (e.g. cattle), making the plant hard to digest
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3
Q

What is abiotic stress?

A

Anything harmful that is natural but non-living

E.g. drought

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4
Q

Explain how plants respond to abiotic stress

A

Carrots produce antifreeze proteins at low temps
^— proteins bind to ice crystals + lower temperature that water freezes at, stopping more ice crystals from growing

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5
Q

Explains how plants respond to being touched

A
  • If a single leaflet (mini leaf-shaped structure that makes up part of a leaf) of this plant Mimosa pudica is touched, a signal spread through the whole leaf, causing it to quickly fold up
  • COULD help protect Mimosa pudica against herbivory in many ways: knocking off small insect feeding on the plant, scaring of animals trying to eat it
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6
Q

What is a tropism?

A

The response of a plant to a directional stimulus (coming from a particular direction)

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7
Q

What is a positive tropism?

A

Growth towards the stimulus

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8
Q

What is a negative tropism?

A

Growth away from the stimulus

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9
Q

List the FIVE types of tropism

A
  • Phototropism
  • Geotropism
  • Hydrotropism
  • Thermotropism
  • Thigmotropism
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10
Q

What is phototropism?

A

Growth of a plant towards the light

  • SHOOTS ARE POSITIVELY PHOTOTROPIC (grow towards light)
  • ROOTS ARE NEGATIVELY PHOTOTROPIC (grow away from light)
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11
Q

What is geotropism?

A

Growth of a plant in response to gravity

  • SHOOTS ARE NEGATIVELY GEOTROPIC (grow upwards)
  • ROOTS ARE POSITIVELY GEOTROPIC (grow downwards)
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12
Q

What is hydrotropism?

A

Plant growth in response to water

ROOTS ARE POSITIVELY HYDROTROPIC (grow towards water)

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13
Q

What is thermotropism?

A

Plant growth in response to temperature

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14
Q

What is thigmotropism?

A

Plant growth in response to contact with an object

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15
Q

What are deciduous plants?

A

Deciduous plants - plants that lose their leaves in winter
^— losing their leaves helped plants conserve water (lost from leaves) during the cold part of the year when its difficult to absorb water from soil (soil water may be frozen) + there’s less light for photosynthesis

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16
Q

Explain the role of plant hormones in leaf loss in deciduous plants

A

Leaf loss is triggered by shortening day length in the autumn + controlled by hormones

  • Auxins inhibit leaf loss (as leaf gets older, less auxin is produced, leading to leaf loss
  • Ethene stimulates leaf loss - produced by ageing leaves (as leaves get older, more ethene is produced)
    ^— a layer of cells (called abscission layer) develops at the bottom of the leaf stalk (where leaf joins the stem) | layer separated leaf from res of plant + ethene stimulates the cells in the abscission layer to expand, breaking the cell walls + causing the leaf to fall off
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17
Q

Explain the role of plant hormones in seed germination

A
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18
Q

Explain the role of plant hormones in stomata closure

A
  • Plants need to be able to close their stomata in order to reduce water loss through transpiration
    ^— done using guard cells (found on either side of a stomata pore)
  • When guard cells are full of water, they are plump and turgid + the pore is open - when the guard cells lose water they become flaccid, making the pore close
  • The plant hormone abscisic acid (ABA) is able to trigger stomata closure
    ^— binds to receptors on the guard cell membranes - causes specific ion channels to open, allowing calcium ions to enter the cytosine from the vacuole
    ^— increased conc. of calcium ions in cytosol causes other ion channels to open - these ions channels allow ions (e.g. K ions) to leave the guard cells, raising the water potential of the cells
  • Water then leaves guard cells by osmosis - guard cells become flaccid + stomata close
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19
Q

What are auxins?

A
  • Produced in the tips of shoots in flowering plants
  • Works by stimulating cell elongation
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20
Q

Give an example of an auxin

A

INDOLEACETIC ACID (IAA)

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21
Q

Outline the role of IAA

A
  • IAA moved around the plant to control tropisms - moves via diffusion + active transport over short distances + via the phloem over long distances
    ^— Results in different parts of the plants having different amounts of IAA | uneven distribution of IAA means there is uneven growth of the plants
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22
Q

Outline the effect IAA has on phototropism

A
  • IAA moves to the more shaded parts of the shoots + roots so there’s uneven growth
  • Cells elongate where IAA is (shaded parts) causing shoot to bend towards the light
  • When IAA moves to the shaded side of the roots, growth is inhibited so the roots bends away from the light
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23
Q

Outline the effect IAA has on geotropism

A
  • IAA moves to the underside of shoots + roots so there’s uneven growth
  • IAA moves to the shaded side of the shoots, cells elongate so the shoots grows upwards
  • IAA moves to the shaded side of the root - growth is inhibited so the root grows downwards
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24
Q

What is apical dominance?

A
  • The shoot tip at the top of a flowering plant is called the apical bud
  • Auxins stimulate the growth of the apical bud + inhibit the growth of side shoots from lateral buds
  • Prevents side shoots from growing, saving energy + preventing side shoots from the same plant competing with the shoot tip for light
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25
Q

Explain the role of auxins in the control of apical dominance

A

Because energy isn’t being used to grow side shoots, apical dominance allows a plant in an area where there are loads of other plants to grow tall very vast - past smaller plants to reach sunlight
- If you remove the apical bud then the plant wont produce auxins, so the side shoots will start growing by cell division + cell elongation
- BUT if you replace the tip w/ a source of auxin, side shoots development is inhibited - demonstrates apical dominance is controlled by auxins
- Auxins become less concentrated as they move away from the apical bud to the res of the plant | Is a plant grows very tall, the bottom of the plant will have a low auxin concentration so side shoots will start to grown near the bottom

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26
Q

Explain the role of gibberellin on seed germination

A
  • Seed start as to germinate when it absorbs water, activating the production of gibberellins
    ^— gibberellins cause enzymes to be released that can breakdown the food stores in the seed so that the embryo plant can use the food to respire + make ATP
  • Evidence suggest that gibberellins cause this to happen by switching on genes that code for amylases and proteases
    ^— evidence also indicates that abscisic has an antagonistic effect + that it is the levels of these two hormones that control when a seed germinates
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27
Q

Describe evidence for the role of gibberellins on seed germination

A
  • Experiments have been conducted using mutant plant varieties which do not have the gene that codes from gibberellins —> mutant plant seeds did not germinate but when exposed to an external gibberellins source, they did germinate
  • Experiments using gibberellin biosynthesis inhibitors also showed that these plants were unable to make gibberellins + their seeds did not germinate —> when plants were given gibberellins, the seed did germinate
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28
Q

Explain the role of gibberellin on stem elongation

A
  • Gibberellins are a small collection of hormones that help plants grow by stimulating elongation on in the stem
  • The higher the concentration of gibberellins, the more elongated the stem
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29
Q

Describe evidence for the role of gibberellins on stem elongation

A
  • Dwarf varieties of plants have very low levels of gibberellins
    ^— often due to a mutation in a gene involved in the synthesis pathway of gibberellins
  • Scientists have experimented by treating these dwarf varieties with an external source of gibberellins results in them growing to the same height as non-dwarf varieties
  • Horticulturalists + farmers apply gibberellin to shorter plants to stimulate growth
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30
Q

Explain the commercial uses of ethene as a plant hormone

A
  • Used to control ripening in fruits
  • Unripe fruit can be picked + transported whilst firm, then sprayed with ethene before it is sold
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31
Q

Explain the commercial uses of auxins

A
  • Used in rooting powder used to encourage growth of new roots from plant cuttings
  • Used as weedkiller, sprayed over weeds which then grow too quickly
    ^— stems give way + die
    ^— too quickly for resources to handle
32
Q

Explain the commercial uses of gibberellins

A
33
Q

What are the components of the mammalian nervous system?

A
  • Peripheral Nervous System
  • Central Nervous System
34
Q

What are the components of the PNS?

A
  • Receptors
  • Sensory neurones
  • Motor neurones
35
Q

What are the components of the CNS?

A
  • Brain
  • Spinal cord

These are teh coordination centres

36
Q

What is the autonomic nervous system?

A
  • Works constantly, subconsciously
  • Involved with activities such as digestion, which involves no conscious control
37
Q

What is the somatic nervous system?

A
  • Consciously controlled
  • Voluntary and when one decides to move
    ^— e.g. choosing to stand up
38
Q

List the 5 key structures of the human brain

A
  • Cerebrum
  • Cerebellum
  • Medulla oblongata
  • Hypothalamus
  • Pituitary gland
39
Q

Describe the structure of the cerebrum

A
  • Largest part of the brain
  • Outer layer known as the cerebral cortex
  • Made up of many folds + split into 2 hemispheres
40
Q

Describe the structure of the cerebellum

A
  • Similar to a mini cauliflower
41
Q

Describe the structure of the medulla oblongata

A
  • Above the spinal cord
42
Q

Describe the structure of the pituitary gland

A

Small, lobed structure known as the master gland

43
Q

Describe the structure of the pituitary gland

A

Small, lobed structure known as the master gland

44
Q

Describe the function of the cerebrum

A
  • Controlling conscious thoughts
  • Language
  • Intelligence
  • Personality
  • High-level functions
  • Memory
45
Q

Describe the function of the cerebellum

A
  • Coordinating movements + balance
46
Q

Describe the function of the medulla oblongata

A
  • Centre of control for unconscious activities
    ^— e.g. breathing + heart rate
47
Q

Describe the function of the hypothalamus

A
  • Responsible for homeostasis
    ^— e.g. thermoregulation + osmoregulation
48
Q

Describe the function of the pituitary gland

A
  • Secretes many hormones to coordinate several responses
    ^— e.g. osmoregulation
49
Q

What is a reflex?

A

A rapid, automatic response to protect an individual from danger

50
Q

Explain the process of a reflex arc

A
  • Once the stimulus is detected by the receptor, an impulse is passed along the sensory neurone to a relay neurones
  • relay neurones passes the impulse onto a motor neurone which is connected to an effector
    ^— e.g. if hot object: effector = hand + arm muscles | response = muscles contract to move hand away
51
Q

Give two examples of a reflex arc

A
  • Knee-jerk reaction
  • Blinking
52
Q

What is the fight or flight response?

A

When mammals are exposed to a potential threat to survival, a series of autonomic responses are triggered to prepare the organism to either fight to survive or run away

53
Q

Describe the detection of a potential threat

A
  • The autonomic nervous system detects the potential threat, sending an impulse to the hypothalamus
    ^— results in more impulses being transmitted along the sympathetic nervous system + adrenal-cortical system
  • Effectors are the adrenal glands, which will release more adrenaline + noradrenaline
    ^— the release of hormones triggers the hypothalamus to stimulate the release of adrenocorticotropic hormone (ACTH) from the pituitary gland
54
Q

Describe the action of adrenaline

A

If blood glucose is too low, adrenal glands will also secrete adrenaline

55
Q

Describe how adrenaline will increase blood glucose by

A
  • Adrenaline (first messenger) attaches to receptors on target cell surfaces, causing a protein (G protein) to be activated + adenylyl cyclase to convert ATP into cAMP (second messenger)
  • cAMP activates an enzyme that can hydrolyse glycogen into glucose
    ^— KNOWN AS second messenger model of adrenaline + glucagon,
56
Q

Describe how the endocrine + nervous systems can affect the heart rate

A
  • Heart has inbuilt pacemaker (SAN) + is myogenic
    ^— BUT can be affected by endocrine + nervous system to respond to stimuli
57
Q

What effects does adrenaline have on the heart?

A
  • Increases heart rate
  • Increases stroke volume
  • Increases cardiac output
58
Q

How does the brain control heart rate?

A
  • Cardiovascular center in the medulla oblongata in the brain controls heart rate via autonomic nervous system
  • Heart + medulla oblongata connected via two nerves:
    ^— accelerator nerve
    ^— vagus nerve
59
Q

Describe the role of the accelerator nerve

A
  • Impulses sent via accelerator nerve in sympathetic nervous system INCREASE HEART RATE
60
Q

Describe the role of the vagus nerve

A
  • Impulses sent via vagus nerve in parasympathetic nervous system DECREASE HEART RATE
61
Q

Describe how heart rate changes in response to pH

A
  • Detected by chemoreceptors
  • pH of blood decreases during time of high respiratory rate due to production of carbon dioxide or lactic acid
  • Excess acid must be removed from the blood rapidly to prevent enzymes denaturing
    ^— achieved by increasing heart rate (more impulses via sympathetic nervous system to SAN) so carbon dioxide can diffuse out into the alveoli more rapidly
62
Q

Describe how heart rate changes in response to pressure

A
  • If bp is too high this can cause damage to the walls of the arteries + it is important to put mechanisms in place to reduce bp
    ^— results in more impulses via parasympathetic nervous system to decrease heart rate
  • If bp is too low, there may be insufficient supply of oxygenated blood to respiring cells + removal of waste
    ^— results in more impulses via sympathetic nervous system to increase heart rate
63
Q

What are the three types of muscle fibres?

A
  • Skeletal muscles
  • Cardiac muscles
  • Involuntary (smooth) muscles)
64
Q

Describe the structure of skeletal muscles

A
  • Most muscle is skeletal - attached to the skeleton + responsible for causing movement of the skeleton
  • Made out of cylindrical shaped cells, which join to form multinucleated myofibrils
  • Striated patter when stained + viewed using a microscope
65
Q

Describe the structure of cardiac muscles

A
  • Heart contains cardiac muscles _ used to pump blood
  • Myogenic
  • Cells are branched to allow contraction across the whole of the atrium or ventricles + cells are uninucleated
  • Striated pattern when stained + viewed using a microscope
66
Q

Describe the structure of involuntary (smooth) muscles

A
  • Muscle lining organs + blood vessels
  • By contracting + relaxing, causes movement of the contents of an organ/blood vessel
    ^— e.g. controlling diameter or arteries, arterioles, bronchi + bronchioles, pupil dilation
  • Uninucleated, spindle shaped + unscripted when stained + viewed using a microscope
67
Q

What is the neuromuscular junction?

A
  • A synapse that occurs between a motor neurone and a muscle fibre
    ^— very similar to synaptic junction
68
Q

Describe the characteristics of the neuromuscular junction

A
  • Only excitatory
  • Connects motor neurones to muscles
  • End point for action potential
  • Acetylcholine binds to receptors on muscle fibre membranes
69
Q

Describe the characteristics of the cholinergic synapse

A
  • Excitatory or inhibitory
  • Connect two neurones, which could be sensory relay or motor
  • New action potential is generation in the next neurone
  • Acetycholine binds to receptors on post-synaptic membrane of a neurones
70
Q

Describe the role of the neuromuscular junction

A
  • When an impulse arrives at teh end of a motor neurones a neurotransmitter passes across the neuromuscular junction + binds to receptors on the sarcolemma
    ^— causes the receptors to open, sodium ions move in + the membrane becomes depolarised
  • Wave of depolarisation is passed down t-tubules causing the sarcoplasmic reticulum to release calcium ions, leading to muscular contraction
71
Q

What are agonist muscle pairs?

A
72
Q

What are antagonist muscle pairs?

A
73
Q

Briefly state how muscles move against the bone

A
  • Muscle act in antagonistic pairs against an incompressible skeleton to create movement
  • This can be automatic as part of a reflex or controlled by conscious thought
74
Q

What are myofibrils?

A

Made up of fused cells that share nuclei + cytoplasm (sarcoplasm) and there is a high number of mitochondria

75
Q

Describe the structure of the sarcomere

A
  • Muscle fibres made up of millions of myofibrils
  • Myofibrils made up of two proteins: myosin + actin
    ^— which form a sarcomere
76
Q

Describe how muscles contract in terms of the sliding filament model

A
  • During muscle contraction sarcomeres within myofibrils shorten as the actin and myosin filaments move past each other
    ^— sliding filament model of muscle contraction
  • An action potential arrives at the neuromuscular junction + calcium ions released from the sarcoplasmic reticulum into the sarcoplasm by diffusion
  • Calcium ions bind to troponin molecules, stimulating them to change shape
    ^— causes troponin and tropomyosin proteins to change position on the actin filaments
  • Myosin binding sites are exposed on the actin molecules
  • The globular heads of the myosin molecules bind with these sites, forming cross-bridges between the two types of filament
  • The myosin heads bend and pull the actin filaments towards the centre of the sarcomere, causing the muscle to contract a very small distance
    ^— movement of myosin heads known as the power-stroke
  • When the myosin heads bend, releases ADP molecule
  • ATP binds to myosin head, allowing it to detach from actin
  • The myosin head acts as an ATPase enzyme, hydrolysing ATP into ADP and Pi; energy released during this reaction allows the myosin head to return to its original position
  • The myosin head can now bind to a new binding site on the actin filaments
  • The myosin heads move again, pulling the actin filaments even closer to the centre of the sarcomere and causing the sarcomere to shorten further
  • As long as troponin and tropomyosin are not blocking the myosin-binding sites and the muscle has a supply of ATP, this process repeats until the muscle is fully contracted

Biology (26 decks)

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