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OCR A-level Biology > Plant and Animal Responses > Flashcards

Plant and Animal Responses Flashcards

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1
Q

Why might plants respond to stimuli?

A

In order to improve chance of survival which will increase their chance of having offspring

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2
Q

What could a plant do in response to threat from a herbivore?

A

Employ chemical defences

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3
Q

Give 3 examples of chemical defences

A

Tannins - deposited in leaves and are toxic to microorganisms and herbivores, make the leaf taste bad

Alkaloids - derived from amino acids, make plants taste bitter

Pheromones - chemicals released by one individual which can affect the behaviour or physiology of another

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4
Q

What are tropisms?

A

Directional growth responses of plants

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5
Q

Give 4 examples of different tropisms

A

Phototropism - grows towards the light

Geotropism - grows away from gravity

Chemotropism - can grow towards or away from a chemical

Thigmotropism - shoots of climbing plants wrap around structures to pull the plant up

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6
Q

What is the name given to the process where a plant grows TOWARDS a stimulus?

A

Positive tropic response

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7
Q

What is the name given to the process where a plant grows AWAY FROM a stimulus?

A

Negative tropic response

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8
Q

What is the name given to a non-directional response?

A

Nastic response

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9
Q

What controls plant responses?

A

Plant hormones

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10
Q

Give 5 examples of plant hormones

A

Cytokinins

Abscisic acid

Auxins

Gibberellins

Ethene

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11
Q

What do Cytokinins do?

A

Promote cell division

delay senescence

overcome apical dominance

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12
Q

What does Abscisic acid do?

A

Inhibits seed germination

Causes stomatal closure

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13
Q

What do Auxins do?

A

Promote cell elongation

Inhibit growth of side-shoots

Inhibit leaf abscission

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14
Q

What do Gibberellins do?

A

Promote see germination

Promote growth of stems

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15
Q

What does Ethene do?

A

Promotes fruit ripening

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16
Q

Where does growth occur in plants?

A

Meristems

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17
Q

What are the 3 types of meristem?

A

Apical meristem - found in the apex of roots and cause them to grow longer

Lateral bud meristem - found in buds, allow side shoots to grow

Lateral meristem - form a cylinder near the outside of shoots and roots and allow them to grow wider

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18
Q

How could you investigate the effect of phototropism?

A

There is a test plant and a control plant

The control plant is illuminated equally from all sides, whereas the test plant is only illuminated from 1 side

Leave them to grow for a few days

The test plant will grow towards the light whereas the control will grow straight up

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19
Q

How could you investigate the effect of geotropism?

A

Plants are positioned perpendicular to the ground

A control plant is placed on a klinostat which spends very slowly meaning gravity has the same effect on all sides of the plant

An experimental plant is left to grow in the perpendicular position

The control will grow straight whereas the experimental plant will bend away from the ground

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20
Q

When light is shining on one side of the shoot, where would the auxins move to?

A

The shaded side

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21
Q

How does auxin cause the stem to bend?

A

It promotes active transport of H+ from the membrane into the cell wall

This lowers pH to a level which is optimum for certain enzymes which break down bonds in cellulose causing the cell wall to be less rigid

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22
Q

How is auxin involved in geotropic actions of roots?

A

If a root is lying flat, auxin accumulates on the lower side of the root, inhibiting cell elongation

The top side continues to grow which causes the root to bend

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23
Q

Give some commercial uses for auxins

A

Rooting powder, for growing plants promotes root growth

Growing seedless fruit - treating unpollinated flowers with auxin can grow seedless fruit

Herbicides - In high concentrations, they promote soot growth so much that the stem cant support itself and dies

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24
Q

Give a commercial use of Cytokinins

A

Because they delay leaf senescence, used to prevent yellowing of lettuce leaves after they are picked

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25
Give commercial uses of Gibberellins
Fruit production - they can make fruit last longer in shops and allow fruit to grow bigger Brewing - Increase the rate of production of malt which comes from barley seeds Sugar production - increases the length of sugar cane which improves yield
26
Give commercial uses of Ethene
Speeding up fruit ripening Promoting fruit drop in cotton, cherry and walnut
27
How and why might one want to restrict ethene's effects in industry?
Ethene could reduce shelf life of bananas when shipping them from the Caribbean Storing them at low temperatures with little Oxygen and high Carbon dioxide levels prevents ethene synthesis
28
What is the role of the nervous system?
To coordinate rapid responses to external stimuli
29
What are the two parts of the nervous system?
Central nervous system Peripheral Nervous system
30
What are the two parts of the peripheral nervous system?
Sensory system Motor system
31
What are the two parts of the motor nervous system?
Somatic system Autonomic System
32
What is the difference in structure of the cells in white and grey matter in nervous tissues?
White matter contains myelinated neurones, whereas grey matter contains non-myelinated neurones
33
What is the role of sensory neurones?
To deliver action potentials from sensory receptors to the CNS
34
What is the role of the somatic motor nervous system?
To conduct action potentials from the CNS to the effector muscles under conscious control E.g any skeletal muscle
35
What is the role of the autonomic motor nervous system?
To conduct action potentials from CNS to the effectors that are under subconscious control E.g the heart or many glands
36
What are the two parts of the autonomic nervous system?
Sympathetic system Parasympathetic system
37
What is the role of the sympathetic nervous system?
To prepare the body for action e.g fight or flight response
38
What is the role of the parasympathetic nervous system?
To conserve energy and allow normal vital function
39
What are the 4 main parts of the brain?
The cerebrum The cerebellum The hypothalamus and pituitary complex The medulla oblongata
40
What is the role of the cerebrum?
Conscious thought Conscious action Emotions Intelligence Factual memory
41
What is the role of the cerebellum?
Coordination and movement e.g Maintaining body position Judging position of objects Skeletal muscle contraction
42
What is the name of the area which connects the cerebrum and the cerebellum?
The Pons
43
What is the role of the hypothalamus and pituitary complex?
Control of Homeostatic mechanisms, e.g Thermoregulation Osmoregulation ADH release Hormonal control
44
What is the role of the medulla oblongata?
Controls non-skeletal muscle, e.g Cardiac centre Respiratory centre Vasomotor centre - regulates circulation and blood pressure
45
What is a reflex action?
A response to changes in the environment that don't require any brain processing
46
What is the function of a reflex action?
To help an organism survive get out of danger avoid damage maintain balence
47
Why is the blinking reflex referred to as a cranial reflex?
Because the neuronal pathway goes through the brain, however no conscious thought is required
48
What is a reflex arc?
When the effector and receptor for a reflex are in the same place
49
What is the name of the reflex when a foreign object touches the eye?
Corneal reflex
50
What is the name given to the reflex caused when there is a sudden change in light?
Optical reflex
51
How and why can the corneal reflex be overridden?
Because the sensory neurone also passes an action potential to myelinated neurones in the pons This then sends it to the cerebral cortex where conscious thought occurs This can then send inhibitory signals to the pons overriding the signal
52
What is a spinal reflex?
A reflex that passes through the spinal cord instead of the brain Means the reflex can happen faster as signals don't need to travel all the way to the brain
53
Give an example of a spinal reflex
Knee jerk reflex
54
Why does the knee jerk reflex occur?
There are specialised stretch receptors in the patella tendon which detect when the muscles are stretched They are known as muscle spindles When this change is unexpected they cause the quadriceps to contract to straighten the leg Enables us to balance on one leg
55
How many types of neurones are involved in the knee jerk reflex?
Only 2 Sensory neurone --> Motor neurone
56
Can you inhibit the knee jerk reflex?
No, it doesn't pass through the brain so it is impossible to inhibit
57
Give some physiological changes that occur during the fight or flight response
Pupils dilate Heart rate and Blood pressure increase Arterioles to digestives system constrict while those to active muscles dilate Blood glucose levels increase Metabolic rate increases Hairs stand up Ventilation rate increases Endorphins released by the brain
58
Which subdivision of the nervous system does the fight or flight response utilise?
The sympathetic nervous system
59
How does adrenaline act inside the cell seeing that it is unable to enter the cell itself?
Adrenaline (first messenger) binds to a surface protein on the target cell which is associated with a G protein inside the cell G protein activates adenyl cyclase which converts ATP to cAMP cAMP is the second messenger and cause an effect inside the cell
60
Which part of the brain secretes releasing hormones?
Hypothalamus
61
Which part of the brain secretes tropic hormones?
Pituitary gland | anterior pituitary
62
How do the hypothalamus and pituitary gland interact to release hormones?
Hypothalamus secretes releasing hormones into the blood They pass down a portal vessel to the pituitary gland These trigger the secretion of tropic hormones from the anterior pituitary gland
63
How does the hypothalamus-pituitary complex stimulate the adrenal cortex? (named chemicals)
Corticotropin-releasing hormone (CRH) is secreted from hypothalamus this triggers the release of Adrenocorticotropic hormone (ACTH) ACTH stimulates the adrenal cortex to release glucocorticoids such as cortisol
64
Give two examples of hormones released by the hypothalamus and their counterpart that is subsequently released from the pituitary gland
Corticotropin releasing hormone (CRH) and Adrenocorticotropic hormone (ACTH) Thyrotropin-releasing hormone (TRH) and Thyroid-stimulating hormone (TSH)
65
How could a damaged pituitary gland impact ones metabolism? possible symptoms?
Damaged pituitary would not secrete the right amount of thyroid stimulating hormone (TSH) This would mean less thyroxine is secreted by the thyroid gland (underactive thyroid) This could make you tired, sensitive to cold, or gain weight
66
Give 3 ways that heart action can be modified by
Increase or decrease in heart rate Altering force of contractions of the ventricular walls Altering stroke volume`
67
What does the term myogenic refer to?
The ability for a muscle to initiate its own contractions at regular intervals
68
Which part of the brain controls heart rate?
Medulla oblongata
69
What sub section of the nervous system is heart rate controlled by?
Autonomic nervous system
70
Which nerve from the medulla will reduce heart rate?
Vagus nerve
71
Which nerve from the medulla will increase heart rate?
Accelerans nerve
72
Give examples of different receptors that will affect heart rate via the medulla
Stretch receptors - detect movement in the limbs and increase heart rate Chemoreceptors - detect when pH in blood decreases (happens when muscles produce CO2) and increase heart rate Stretch receptors in Carotid Sinus - detect when blood pressure is too high, reduce heart rate
73
What is the role of an artificial pacemaker?
To provide electrical impulses to the SAN when it can no longer do it itself Allows the heart to beat regularly and with the correct strength of contraction
74
What are the 3 types of muscle?
Involuntary (smooth) muscle Voluntary (skeletal) muscle Cardiac muscle
75
Where might smooth muscle be found?
In the walls of tubular structures such as the digestive system and blood vessels
76
What sub-division of the nervous system is smooth muscle controlled by?
Autonomic
77
Describe the structure of smooth muscle
Spindle shaped Each cell contains a nucleus and bundles of actin and myosin
78
Describe the structure of cardiac muscle
individual cells form long fibres Fibres form cross-bridges between each other Cells joined by intercalated discs, which are specialised membranes which allow the free diffusion of ions
79
What is the name for a cardiac muscle cell?
Myocyte
80
What is the role of Purkyne fibres?
Carry electrical impulses in the heart Coordinate contraction to prevent back flow
81
What is the name for a skeletal muscle cell?
Sarcomere
82
Describe the structure of a sarcomere
Multinucleated Surrounded by sarcolemma Contains the sarcoplasm which contains lots of mitochondria and sarcoplasmic reticulum Contains actin and myosin
83
Which subdivision of the nervous system controls skeletal muscle?
Somatic nervous system
84
What is the name given to the area where the muscle joins to the nervous system?
Neuromuscular Junction
85
Describe the process of an action potential causing a contraction at a neuromuscular junction
Action potential causes Ca2+ to flood the axon tip This causes acetyl choline vesicles to bind with the membrane and release into the gap Acetyl choline diffuses and binds to receptors on the muscle which open Na+ channels Na+ moves in and depolarises the muscle causing contraction
86
What are myofibrils?
The contractile units of skeletal muscle
87
What are the two types of protien filament in the myofibril?
Thin filament Thick filament
88
What makes up the light band (I-band)?
Thin filaments
89
What is the Z-line?
Where the thin filaments are held together They show the ends of the sarcomere
90
What makes up the dark band (A-band)?
Thick filaments
91
What is the H-zone?
The area in the dark band where there is no overlap of the thin and thick filaments
92
Which protein makes up the thin filaments?
Actin
93
What is attached to actin the thin filaments?
A molecule of tropomyosin to which is attached globular molecules of troonin
94
What protein makes up the thick filaments?
Myosin Myosin has two heads which are mobile and will bind to actin when the binding sites are available
95
What is sliding filament theory and how can it be shown experimentally?
States that during contraction the thin and thick filaments slide past one another. Can be shown as on a micrograph, during contraction, Light band (I-band) and H-zone get shorter. The Z-lines move closer together and thus the sarcomere shortens. This shows the the light filament is sliding over the thick filament

OCR A-level Biology (24 decks)

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