I/E: Responses in Plants/Animals

Question 1

Tropism

Answer 1

The response of a plant to a directional stimulus.

Question 2

Positive tropism

Answer 2

Plant growth towards the stimulus.

Question 3

Negative tropism

Answer 3

Plant growth away from the stimulus.

Question 4

Phototropism

• Positive phototropism*
• Negative phototropism*

Answer 4

Growth of a plant in response to light.

• Positive = growth towards light*
• Negative = growth away from light*

Question 5

Gravitropism

• Positive gravitropism*
• Negative gravitropism*

Answer 5

Growth of a plant in response to gravity

• Positive = growth towards gravity/downwards*
• Negative = growth away from gravity/upwards*

Question 6

Phototropism/gravitropism of roots?

Phototropism/gravitropism of shoots?

Answer 6

Roots = negatively phototropic, positively gravitropic.

Shoots = positively phototropic, negatively gravitropic.

Question 7

Growth factors

Answer 7

Hormone-like chemicals that speed up or slow down plant growth.

Question 8

How do plants respond to directional stimuli?

Where are these produced?

Answer 8

Using growth factors produced in the growing regions of the plant, eg. the roots and the shoots.

Question 9

Auxins

Answer 9

Growth factors that stimulate the growth of shoots by cell elongation.

Question 10

What does high concentrations of auxins in the roots of a plant do?

Answer 10

Inhibits the growth of roots.

Question 11

Cell elongation

Answer 11

Cell walls of plants become loose and stretchy, so the cell gets longer.

Question 12

Name an auxin:

Answer 12

Indoleacetic Acid (IAA)

Question 13

Where is IAA produced?

Why is it moved around plants?

Answer 13

In the tips of shoots in flowering plants.

Moved around the plant to control tropisms.

Question 14

How does IAA move around a plant:

• long distance?
• short distance?

What does this movement result in?

Answer 14

Short distance = diffusion and active transport

Long distance = via the phloem

Results in an uneven distribution of IAA and uneven growth.

Question 15

Describe the tropisms that occur in the shoots of flowering plants:

Answer 15

1. Phototropism = IAA concentration increases on shaded side of shoot = cells elongate and shoot bends towards the light.
2. Gravitropism = IAA concentration increases on the lower side of the shoot = cells elongate and shoot grows upwards.

Question 16

Describe the tropisms that occur in the roots of flowering plants:

Answer 16

1. Phototropism = IAA concentration increases on shaded side = growth is inhibited so root bends away from light.
2. Gravitropism = IAA concentration increases on the lower side = growth is inhibited so root grows downwards.

Question 17

What are the two responses of simple organisms?

Answer 17

Tactile responses (taxes)

or

Kinetic responses (kineses)

Question 18

Tactile responses

Answer 18

Organisms move towards or away from a directional stimulus, eg light.

Question 19

Give an example of a tactile response in woodlice:

Answer 19

• Phototaxis - move away from a light source.
• Helps them survive:
  
  • Keeps them concealed under stones during the day (safe from predators)
  • Keeps them in damp conditions (reduces water loss)

Question 20

Kinetic responses

Answer 20

Organisms’ movement is affected by a non-directional stimulus, eg. humidity.

Question 21

Give an example of a kinetic response in woodlice:

Answer 21

• High humidity = move slowly and turn less often, so that they stay where they are.
• Low humidity = move faster and turn more often, so that they move in to a new area.
• Increases chances of moving into a high humidity area, and improves survival by reducing water loss.

Question 22

What is a choice chamber and what is it used to investigate?

Answer 22

Container with different compartments, in which you can create different environmental conditions.

Can investigate how animals respond to certain conditions.

Question 23

Describe an investigation using choice chambers to investigate animal responses:

Answer 23

1. Split choice chamber into 4 conditions.

• Damp/dark
• Dry/dark
• Damp/light
• Dry/light

1. Place 10 woodlice on the mesh in the centre of the chamber and cover with the lid.
2. After 10 minutes, take off lid and record the number of woodlice in each condition.
3. Repeat.