2 (j) Co-ordination and Response

Question 1

Positive Geotropism

Answer 1

Grow in the direction of gravity

e.g. Plant Roots

Question 2

Negative Geotropism

Answer 2

Grow against the direction of gravity

Question 3

Positive Phototropism

Answer 3

Grow towards light

Question 4

Word Tropism meaning

Answer 4

A directional growth response in response to a stimulus

Question 5

Auxin

Answer 5

Plant hormone

Controls growth of cells in the tips of roots + shoots in response to light + gravity

Question 6

How does auxin move

Answer 6

Diffuses downwards

Question 7

What do auxin in shoot cells cause?

Answer 7

Cell Elongation

Even distribution of auxin = shoot growing evenly

Question 8

What happens when a shoot is exposed to light?

Answer 8

More auxin accumulates on the shaded side of the shoot -> causes more cell division/more growth/more elongation

Question 9

Animals vs Plant Responses

Answer 9

Animals:
* detect stimulus by neurones -> more rapid and short duration using electrical impulses

• Plants detect stimulus for a long duration, with slower response. Involves auxin (growth regulation) using phloem cells

Question 10

Hydrotropism

Answer 10

Responses to water

Question 11

Geotropism

Answer 11

Responses to gravity

Question 12

Phototropism

Answer 12

Resposes to light

Question 13

Homeostasis

Answer 13

The maintenance of a constant internal environment

Question 14

Examples of Homeostasis

Answer 14

• Body water content
• Body water temperature

Question 15

What does a co-ordinated response require?

Answer 15

• Stimulus
• Receptor
• Effector

Question 16

Order of a Response

Answer 16

1. Stimulus
2. Receptor
3. Sensory Neurone
4. Relay Neurone
5. Motor Neurone
6. Effector
7. Response

Question 17

What happens in a co-ordinated response/reflex arc

Answer 17

1. Stimulus detected by receptors
2. Electrical impulse generated and passes from receptor-> sensory neurone -> relay neurone (in spinal cord) -> motor neurone
3. Between each neurone there is a synapse
4. Motor neurone is connected to a muscle or gland that brings about a response

Question 18

What happens at a synapse

Answer 18

1. Electrical impulse arrives at pre-synaptic neurone
2. This releases the neurotransmitters stored in vesicles
3. The neurotransmitters diffuses across the synaptic cleft
4. They bind to the membranes of the receptors on the post - synaptic neurone
5. Stimulates another electric impulse

Question 19

What makes up the central nervous system?

Answer 19

Brain and spinal cord
Linked to sense organs by nerves

Question 20

Is the eye a receptor?

Answer 20

Yes