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Biology - OCR A > 5.1.5 - Plants And Animal Responses > Flashcards

5.1.5 - Plants And Animal Responses Flashcards

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1
Q

What is tropism in plants?

A

Tropism is a directional growth response of a plant as a result of a stimulus.

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2
Q

Give 4 examples of types of tropism?

A

*Thigmotropism (response to touch)
*Geotropism (response to gravity)
*Chemotropism (response to chemicals)
*Phototropism (response to light)

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3
Q

What is positive tropism?

A

The growth towards a stimuli like light

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4
Q

What is negative tropism?

A

The growth away from a stimuli

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5
Q

What is a mastic response, and give an example>

A

A mastic response is a non-directional response to external stimuli.
##Footnote
Mimosa pudica rolls its leaves when touched (a thigmonastic response).

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6
Q

What is auxin?

A

Auxin is a plant growth hormone located in the tips of shoots and roots.

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7
Q

What is auxins role in plant growth?

A

It stimulates cell elongation, causing the plant to bend towards light due to IAA (indoleacetic acid) accumulation on the shaded side.

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8
Q

What is apical dominance?

A

Apical dominance is when a plant favors upward growth from the top (apex) over other parts. Auxin promotes this upward growth.

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9
Q

What is lateral growth?

A

Lateral growth refers to sideward growth of the plant, which is not favored.

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10
Q

How is lateral growth affected by auxin?

A

Auxin inhibits lateral growth and bud growth

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11
Q

What role does abscisic acid play in plant growth?

A

Abscisic acid works along with auxin to inhibit lateral bud growth.

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12
Q

What role do cytokinins play in plant growth?

A

Cytokinins promote lateral bud growth if there is no auxin, allowing the plant to obtain more nutrients.

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13
Q

What are gibberellins and what do they promote?

A

Gibberellins are plant hormones that promote stem elongation and seed germination.

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14
Q

Why do small plants have low levels of gibberellins?

A

Small plants have low levels of gibberellins, which is why they do not grow tall.

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15
Q

How do selective weed killers use auxin?

A

Selective weed killers use high concentrations of synthetic auxin to cause rapid, damaging growth in weeds, making them susceptible to pathogens.
##Footnote
This technique is effective against broadleaf weeds but less harmful to grasses.

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16
Q

How is auxin used in rooting powders?

A

Rooting powders contain auxin at low doses to stimulate root growth in cuttings. The lower ends of cuttings are dipped in powder before planting, which helps roots to develop.

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17
Q

How is ethane used to control the ripening of fruit?

A

Ethene can be used to stimulate the ripening of fruit and is often used for fruits that are delicate and soft when they are ripe and can be easily damaged in transport. Instead the fruit is harvested unripe, transported and then ripened artificially using ethene

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18
Q

What hormone causes the stomata to close?

A

Abscisic acid

19
Q

What does abscisic acid do to a plant?

A
  • moves through translocation from the roots to the leaves
  • stimulates the stomata to close to lower the rate of transpiration and photosynthesis
20
Q

When is abscisic acid released?

A

When the pant is experiencing water stress

21
Q

What is evidence for the role of auxin (2 ways to show)?

A

Way 1:
- prune the plant to remove the apical bud and auxin
- the plant will grow laterally instead of upwards to acquire energy and raw materials

Way 2:
- prune the plant removing auxin
- replace with an agar block infused with auxin to inhibit lateral growth even though upwards growth can’t happen
- shows that it promotes upwards growth and inhibits lateral growth

22
Q

Describe the role of gibberellins in seed germination.

A
  1. Seed embryo absorbs water
  2. Gibberellins is released
  3. Gibberellins moves to the aleurone layer where it stimulates the production of amalayse
  4. Amalayse convert starch to maltose
  5. Maltase converts maltose into glucose
  6. Glucose is used by the embryo as a respiratory substance and protein
23
Q

What are the 2 main divisions of the mammalian nervous system?

A
  • central nervous system
  • peripheral nervous system
24
Q

What are the 2 divisions of the peripheral nervous system?

A
  • Sensor division
  • Motor division
25
Q

What are the 2 divisions of the motor division?

A
  • autonomic nervous system
  • somatic nervous system
26
Q

What are the 2 divisions of the autonomic nervous system?

A
  • sympathetic division
  • parasympathetic division
27
Q

What is the difference between the autonomic and somatic nervous systems?

A

Autonomic is involuntary responses whereas somatic is voluntary responses

28
Q

What is the difference between the parasympathetic and sympathetic divisions?

A

Sympathetic uses adrenaline to speed up processes whereas parasympathetic uses acetylcholine to slow down processes

29
Q

What do baroreceptors do and where are they found?

A

Found in the carotid sinus
- detects pressure changes

30
Q

What do baroreceptors do at high pressures?

A

The vagus nerve stimulates the SAN slowing the heart rate

31
Q

What do baroreceptors do when blood pressure is low?

A

The accelerans nerve stimulates the SAN increasing the heart rate

32
Q

What do chemoreceptors detect?

A

pH lowering as a result of excess carbon dioxide dissociating to carbonic acid

33
Q

What do chemoreceptors do at low and high carbon dioxide levels?

A

Low carbon dioxide:
The vagus nerve stimulates the SAN slowing heart rate.
High carbon dioxide:
Accelerans nerve stimulates the SAN causing the heart rate to speed up

34
Q

What are the 2 nerves responsible for the nervous control of the heart?

A
  • Vagus nerve
  • Accelerans nerve
35
Q

What do stretch receptors do?

A

Detective the limbs moving, they then feed this information to the medulla oblongata which increases the heart rate to provide muscles with oxygen and glucose faster

36
Q

What is sarcalemma?

A

A layer around muscle fibres

37
Q

What is sarcoplasm?

A

Stuff that fills gaps in the myofibrils

38
Q

What is the A band on a myofibril?

A

The darker section that is made of thicker myosin protein filaments

39
Q

What is the I band on a myofibril?

A

Lighter section made of thinner actin protein filaments

40
Q

What is a Z disk/line on a myofibril?

A

Border between individual sarcomeres

41
Q

What is a sarcomere on a myofibril?

A

Repeating section from z disk to z disk.
It is 2.5 micrometers at rest

42
Q

What is the H zone on a myofibril?

A

Area of a sacromere where dark and light bands overlap and where contraction happens

43
Q

What is the M line?

A

The midline of each sacromere

Biology - OCR A (25 decks)

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