3.6.1.1 - SURVIVAL AND RESPONSE

Question 1

give one similarity and one difference between a taxis and a tropism (2)

Answer 1

similarity: both a directional response to a stimulus

difference:
- tropism occurs in plants and taxis occurs in animals
- in taxis, the whole organism moves and tropism is a growth response

Question 2

Use your knowledge of IAA to explain the growth curvature in the tip of the plant shoot (3)

Answer 2

1. tip produces IAA
2. IAA diffuses into shoot (down)
3. more elongation of cells on (top) one side than other

Question 3

suggest two advantages of simple reflexes (2)

Answer 3

1. rapid
2. protect against damage to body tissues
3. do not have to be learnt
4. help escape from predators
5. enable homeostatic control

Question 4

explain the importance of reflex actions (3)

Answer 4

1. automatic/involuntary
2. reduces damage to tissues / prevents injury (burning)
3. role in homeostasis
4. posture/balance
5. finding food/mate
6. escape from predator

Question 5

name the process by which IAA moves from the growing regions of a plant shoot to other tissues (1)

Answer 5

diffusion

Question 6

when a young shoot is illuminated from one side, IAA stimulates growth on the shaded side.

explain why growth on the shaded side helps to maintain the leaves in a favourable environment (2)

Question 7

when a young shoot is illuminated from one side, IAA stimulates growth on the shaded side.

explain why growth on the shaded side helps to maintain the leaves in a favourable environment (2)

Answer 7

1. causes plant to bend/grow toward light/positive phototropism
2. light required for photosynthesis