Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

A Level Biology Paper 2 > Topic 6 > Flashcards

Topic 6 Flashcards

1
Q

What is a stimulus?

A

A detectable change in the environment

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

How are stimulus detected?

A

Receptor cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What kind of responses do animals have?

A

Animals have nerves and hormones which allow them to respond quickly to changes in the environment.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What kind of responses do plants have?

A

Plants lack nerves or hormones but sensitive to the environment and correspond by growing in a particular direction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What are tropism?

A

Plant responses via a growth to stimuli

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What stimuli the plants respond to?

A

Light
Gravity
Water
Chemicals

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is a positive tropism?

A

Growing towards a stimulus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is a negative tropism?

A

Growing away from a stimulus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What does phototropic mean?

A

Growing towards or away from light

This is for maximising photosynthesis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What does gravitropic/geotropic mean?

A

Growing towards or away from gravity

This allows shoots to move towards the sun and water in soil to be absorbed by roots

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What does chemotropic mean?

A

Growing towards or away from chemicals

For example so that pollen can reach ovaries

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What does thigmotropic mean?

A

Growing towards or away from touch

This allows them to grow upwards

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What does aerotropic mean?

A

Growing towards or away from air

This allows plants to grow towards water

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What are hormones?

A

Chemical messengers that are secreted into the blood to effect organs and tissues

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What do plants not have?

A

Blood and so hormones

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What do plants have instead of hormones?

A

Chemicals called growth factors such as IAA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Where is IAA produced?

A

In the tip of the roots and shoots

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What is IAA an example of?

A

An auxin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What happens when unilateral light shines on the shoot of a plant?

A

This causes IAA, produced in the tip, to move to the shaded side by active transport
Where it diffuses down the shaded side
Causing cell elongation on this side
These cells elongate faster than the other so the plant bends towards the light

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

How do plant roots grow towards gravity?

A

IAA moves to the lower side of root by active transport due to gravity
IAA inhibits elongation of cells on lower side
Cells elongate more on upper side and root bends downwards

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

How does a root cell detect the direction of gravity?

A

Amyloplasts (organelles) that are dense due to be packed with starch and so accumulate on the lower side of cells. IAA is actively transported to where the Amylopasts are.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What does removing the tip or using a cover on the tip of a plant shoot show?

A

The photographic response will stop, this shows that the tip of the shoot is responsible for detecting light.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What does putting a gelatin block as a barrier between a plant and the cut tip show?

A

When photographic response still occurs as it shows that the stimulus for growth is a chemical, able to travel through the gelatin block.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What does the ability to respond to a stimulus due for organisms?

A

Increase the chances of survival

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
What are taxes and kinesis examples of?
Innate animal behaviour
26
What is the taxis response?
This is where an organism will move its entire body towards a favourable stimulus or away from an unfavourable stimulus. This is a response to a directional stimulus.
27
What is a kinesis response?
When organisms change the speed of movement and the rate that changes direction due to a nondirectional stimulus. This is an increase in random movements designed to bring an organism back to favourable conditions.
28
What is the sequence in a reflex arc?
Stimulus Receptor Sensory neuron Relay neuron Motor neuron Effector Response
29
What are the parts of the CNS?
Brain and spinal cord
30
How many synapses are involved in reflex arcs?
2
31
Why do reflex arcs need to be extremely quick and immediate processes?
So that no time is wasted processing information in the brain.
32
What are the three things to describe reflex arcs?
Invariable: cannot be varied in the light of experience Involuntary: happens without any conscious thought Innate: present from birth
33
What are the two things that the nervous system is divided into?
The central nervous system and the peripheral nervous system
34
What do sensory neurones do?
Carry nerve impulses from receptors towards the CNS
35
What do motor neurons do?
Curry nerve impulses from the CNS towards the effectors
36
What is the pacinian corpusle an example of?
A receptor
37
What does the Pacinian corpus respond to?
Changes in mechanical pressure They are deformed by pressure They respond individually
38
What makes the pacinian corpuslespecific?
They only respond to changes in mechanical pressure and not any other kind of stimulus, e.g. heat or light
39
How do pacinian corpuscles act as transducers?
By converting mechanical energy into electrical energy in the form of a generator potential.
40
Where are Pacinian corpucles found?
In the skin
41
What is the structure of pacinian corpuscles?
They have layers of connective tissue called lamella This tissue is wrapped around the nerve ending of a sensory neuron.
42
Describe a neurone at rest?
These neurone have no nervous impulse and so are polarised. They are resting potential and are relatively more negative on the inside (-70 MV)
43
Describe a neurone when stimulated.
When there is a nervous impulse, your own become depolarised in the form of an action potential and our relatively more positive on the inside (+40 MV)
44
How are action potential triggered by the pacinian corpuscle?
The Pacinian corpuscle is stimulated by pressure The lamellae are deformed and press on the sensory neurone The neuron membrane stretches deforming stretch mediated sodium iron channels. The channels widen and sodium ions diffuse in causing deep polarisation and a generator potential. If this potential reaches the threshold point an action potential triggered.
45
What is the firing threshold?
The threshold needed to trigger an action potential.
46
What does pressure need to do to reach the threshold value for the pacinian corpuscle?
Be heavy enough
47
Where are photo receptors located in the eye?
The retina
48
Where does light into the eye?
The cornea
49
What is the role of the fovea ?
This is where light is focused by the cornea and lens. Light intensity is highest here so this is where the most clones are.
50
What is the optic neuron?
This is a sensory neurone which passes action potentials to the brain?
51
How do photo receptors act as transducers?
They convert light energy into electrical energy in the form of generator potentials, if the threshold value is reached an action potential forms and an impulse sentence to the brain.
52
How do photo receptors work?
When light hits a photo receptor a pigment in the photo receptor absorbs the light and breaks it down. This is called bleaching The change causes sodium iron channels to open in the membrane and an influx of sodium ions courses a generator potential.
53
What is bleaching in photo receptors?
When a pigment in the photo receptor absorbs the light and breaks it down.
54
What happens if a generator potential, as a result of bleaching, reaches the threshold value?
An impulse passes to the optic nerve via a bipolar neurone as an action potential
55
What are rods and cones?
Photo receptors
56
What is the pigment in rods?
Rhodopsin
57
Where are rods located?
Located throughout the retina except the fovea
58
Do our eyes have more cones or rods?
There are more numerous rods than cones
59
What can rods not do?
Distinguish between different wavelength of light, they are monochromatic (black and white)
60
What are the negatives and positives of rods in comparison to cones?
They share bipolar connections to the brain which leads to convergence, this means they have poor visual acuity (more difficulty distinguishing between points) However, they are more sensitive because they share these bipolar connections and can respond to lowlight intensities
61
What is spatial summation?
This is the idea that through convergence (multiple synapses Being used for action potentials) Cells are able to reach threshold value making them more sensitive to lowlight.
62
What pigments do cones have?
Iodopsin
63
Where are cones mainly located?
The fovea
64
What can cones do that rods can’t?
They can distinguish between different wavelength of light, meaning they are trichromatic. Cones absorb different wavelengths of light, red, green, and blue.
65
In white light, what kind of cone is stimulated?
All three
66
What does the colour that someone sees depend on?
The percentage of different cones in the region of the eye that is stimulated.
67
What are the negatives and positives of cones in comparison to rods?
Each cone has its own bipolar connection to the brain meaning they have good visual acuity as the brain receives separate impulses. However, they can only respond to high light intensities as they don’t show convergence so threshold value cannot be reached as easily.
68
Why is cardiac muscle considered myogenic?
This means it can generate its own impulses to contract independently of the nervous system
69
What are the four parts of the heart involved in contraction?
SAN AVN Bundle of His Purkinje Fibres
70
What is the SAN?
A specialised group of cells that can produce an action potential
71
What is the role of the AVN?
Allows the passage of electrical activity but at a slower rate

A Level Biology Paper 2 (4 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions