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A-level Biology Year 2 > Survival and Response > Flashcards

Survival and Response Flashcards

1
Q

Define tropism.

A

The response of a plant to aa directional stimulus. They respond to this stimuli by regulating their growth

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2
Q

Stimuli: Gravity
Tropism: ____tropism
Shoot: _____tive
Roots: _____tive

A

Stimuli: Gravity
Tropism: Geotropism
Shoot: Negative
Roots: Positive

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3
Q

Stimuli: Light
Tropism: ____tropism
Shoot: _____tive
Roots: _____tive

A

Stimuli: Light
Tropism: Phototropism
Shoot: Positive
Roots: Negative

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4
Q

What is positive and negative tropism?

A

Positive tropism: growth towards stimulus
Negative tropism: growth away from stimulus

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5
Q

Give one similarity and one difference between taxis and tropism. (2)

A
  1. Similarities: directional response to a stimulus/movement towards/away from stimulus
  2. Difference: taxis causes the whole organism to move and tropism is a growth response.
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6
Q

What stimulates flowering and seed germination?

A

Gibberellins

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7
Q

What causes the growth in shoots by cell elongation?

A

Auxins

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8
Q

What is IAA?

A

Indoleacetic Acid
Its a plant hormone factor and one effect it has is it causes elongation of plant cells.

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9
Q

How does positive phototropism in plant shoots work?

A
  1. IAA is synthesised in root tips
  2. IAA diffuses into the growing region
  3. Light causes IAA to move to shaded side
  4. More IAA on shaded side so it stimulates elongation on shaded side
  5. Shaded side grows faster and causes roots to bend toward the light
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10
Q

How does positive geotropism in plant shoots work?

A
  1. IAA is synthesised in root tips
  2. IAA diffuses into the growing region
  3. Gravity causes the movement of IAA towards underside of root
  4. More IAA on underside so inhibits elongation of underside.
  5. Topside grows faster and causes the root to bend towards gravity
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11
Q

Where is IAA produced?

A

Plant tips

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12
Q

How does IAA cause positive phototropism?

A
  1. IAA synthesised in shoot tips
  2. IAA diffuses into growing region
  3. Light causes the movement of IAA onto shaded side
  4. More IAA on shaded side
  5. Stimulates elongation on shaded side
  6. Shaded side grows faster so shoot bends towards light
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13
Q

How does IAA cause positive geotropism?

A
  1. IAA synthesised in root tips
  2. IAA diffuses into growing region
  3. Gravity causes the IAA towards the underside
  4. More IAA on underside
  5. Inhibits growth on underside
  6. Underside grows slower so root bends towards gravity
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14
Q

Investigation 1:
How does growth differ in these three shoots and why?:
A - uncut (control)
B - tip removed
C - tip removed but then replaced

A

B - No growth as no tip to stimulate growth
C - Grew slower than A

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15
Q

Investigation 2:
How does growth change in a shoot that has the tip cut off and then replaced with agar jelly in the middle?

A

Growth is normal as IAA can diffuse through the agar jelly

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16
Q

Investigation 3:
How does growth change in a shoot that has the tip cut off and then replaced with agar jelly (which has the tip on top for 2 hours, which was then removed)?

A

Growth occurred as IAA can diffuse into the agar during the 2 hours and then diffuse into the cut end when agar jelly was placed on top.

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17
Q

Investigation 4:
How does growth differ in these three shoots when a light source is directional and why?:
A - normal (control)
B - black cover over tip
C - shoot covered by black sand apart from tip

A

A - Shoot grew towards the beam of light due to positive phototropism
B - Shoot grew straight up, positive phototropism didnt occur as IAA was shaded from light
C - Shoot still grew towards the beam of light due to positive phototropism

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18
Q

Investigation 5:
How does growth change in a shoot that is in the dark and has the tip cut off and then replaced with agar jelly (which had the tip on top for 2 hours, that was then removed) which only covers half the cut end?

A

Shoot grows in the opposite direction to the side the agar is covering even without a light source.
IAA is able to diffuse into the side the agar is covering so growth is faster on that side.

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19
Q

Investigation 6:
What happens when thin slides of mica are used to separate two sides of a shoot tip that is on agar jelly in the dark vs light in this scenario:
1. Tip and agar intact

A
  1. Similar amounts of IAA in light and dark -> shows IAA is made in the tip in light or dark
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20
Q

Investigation 6:
What happens when thin slides of mica are used to separate two sides of a shoot tip that is on agar jelly in the dark vs light in this scenario:
2. Tip split but agar intact

A
  1. IAA amount the same -> shows IAA is made in the tip and diffuses down, but does not show on what side it is made
21
Q

Investigation 6:
What happens when thin slides of mica are used to separate two sides of a shoot tip that is on agar jelly in the dark vs light in this scenario:
3. Both agar and tip split

A
  1. IAA amount is same on both sides of the mica -> shows when IAA is made in the shoot, the mica prevents it diffusing to a certain side
22
Q

Investigation 6:
What happens when thin slides of mica are used to separate two sides of a shoot tip that is on agar jelly in the dark vs light in this scenario:
4. Only lower half of tip and agar are split

A
  1. IAA amount same as 3 in dark but in light the amount is higher on shaded side -> shows that the light causes IAA to diffuse away
23
Q

What is the order of a reflex neurone?

A

Receptor -> sensory neuron -> synapse or CNS -> motor neuron -> effector

24
Q

What is kinesis?

A

A random behaviour pattern where an animal responds to change in stimulus by increasing or decreasing activity.

25
Q

What is taxis?

A

The movement of an organism either towards or away from a directional stimulus
positive taxis = towards stimulus
negative taxis - away from stimulus

26
Q

What are the three parts of the nervous system and their roles?

A
  • Receptors detect stimuli
  • Neurones detect transmission of nerve/electrical impulses
  • Effectors respond
27
Q

Is the nervous system slow or fast response?

A

very fast

28
Q

What are the two divisions of the nervous system?

A
  • Central nervous system (CNS) which is the brain and spinal cord
  • Peripheral nervous system which are the nerves
29
Q

What are neurones?

A

Specialised cells that are adapted to their function of carrying electrical impulses from one part of the body to another

30
Q

What are the different types of neurone?

A
  • Sensory
  • Bipolar
  • Motor
31
Q

What is the structure of motor neurones?

A
  • Cell body
  • Dendrites
  • Axon
  • Schwann cells
  • Myelin sheath
  • Node of Ranvier
  • Terminal end branch
32
Q

What is the function of the cell body in the neurone?

A

Holds the nucleus in the cytoplasm which produces proteins and neurotransmitters

33
Q

What is the function of the dendrites in the neurone?

A
  • Carry nerve impulses towards the cell body
34
Q

What is the function of the axon in the neurone?

A
  • Carries nerve impulses away from the cell body
35
Q

What is the function of the Schwann Cells in the neurone?

A
  • Produce myelin sheath
36
Q

What is the function of the node of Ranvier in the neurone?

A
  • Gap between Schwann cells where there is no myelin sheath
37
Q

What is the function of the terminal end branch in the neurone?

A
  • connects the neurone to the effector
38
Q

What is a nerve impulse?

A

The movement of sodium ions and potassium ions across the membrane of a neurone.

39
Q

What are the three stages of a nerve impulse?

A
  • Resting potential
  • Depolarisation
  • Repolarisation

There is also hyperpolarisation

40
Q

What occurs at resting potential?

A
  • Membrane potential is -70mV
  • Due to more sodium ions outside the membrane compared to potassium. (Electrochemical gradient)
  • Maintained until stimulus is detected
41
Q

What occurs during depolarisation?

A
  • Stimulus makes membrane more permeable to sodium ions (sodium gates open) and sodium diffuses into the cell.
  • High sodium ion conc inside cell reverses the resting potential so inside cell is more positive
  • Action potential
42
Q

What is the all or nothing law?

A

An action potential will only occur if the membrane is stimulated enough to open all sodium channels
So a stimulus must be large enough or no action potential will occur.

43
Q

What occurs in repolarisation?

A

-Sodium gates close and potassium gates open.
- Potassium ions diffuse out of cell
- Inside cell becomes negative again

44
Q

What occurs in hyperpolarisation?

A
  • Too much potassium leaves cell so it becomes extra negative inside
  • The sodium potassium pump restores the resting potential
45
Q

How is the resting potential established?

A
  • High number of sodium inside membrane and potassium outside membrane after repolarisation
  • Sodium potassium pump moved 3 sodium out and 2 potassium in, which requires ATP
  • All sodium channels closed but some potassium ones open
  • Resulting in more positive ions outside the membrane than inside the neurone
46
Q

What is the refractory period?

A

After transmitting an electrical impulse, an axon has to recover before its able to transmit another

47
Q

How are impulses transmitted along the axon?

A
  • Action potentials stimulate adjacent polarised areas causing it to be passed along
  • The impulse travels by jumping from one node of ranvier to the next, which is salatory conduction
48
Q
A

A-level Biology Year 2 (16 decks)

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