Tropisms

Question 1

What is taxis

Answer 1

A directional response towards or away from a stimulus

Question 2

What is kinesis

Answer 2

A non-directional response to unfavourable environmental conditions

Question 3

What does behaviour refer to

Answer 3

The observable coordinated responses an animal makes to stimuli in its environment

Question 4

What is innate behaviour

Answer 4

instinctive behaviour which is genetically programmed so the organism responds to environmental circumstances

Question 5

What does positive phototaxis refer to

Answer 5

Moving towards a light stimulus

Question 6

What does negative phototaxis refer to

Answer 6

Moving away from a light stimulus

Question 7

What does negative chemotaxis refer to

Answer 7

Moving towards a chemical stimulus

Question 8

What does positive chemotaxis refer to

Answer 8

Moving away form a chemical stimulus

Question 9

How would an organism act when performing kinesis

Answer 9

The organism would change the speed of movement and the rate at which it changes direction with the frequency of changing direction increasing in more unpleasant conditions

Question 10

How would a woodlouse perform kinesis in unfavourable conditions

Answer 10

Woodlice prefer humid areas so if they enter a dry area the woodlouse would move rapidly and change direction to increase the chances of leaving the dry areas.

After a period of time if they haven’t found the humid area they will walk in a straight line to find it

Question 11

What is a tropism

Answer 11

How plants respond to their environment

Question 12

What type of tropism occurs when light is the stimulus

Answer 12

Phototropism

Question 13

What is positive phototropism

Answer 13

Where the plant grows towards the light.

Question 14

Where does positive phototropism occur

Answer 14

At the shoot tip

Question 15

What is negative phototropism

Answer 15

Where the plant grows away from the light

Question 16

Where does negative phototropism occur

Answer 16

At the roots

Question 17

What type of tropism occurs when gravity is the stimulus

Answer 17

Geotropism

Question 18

What is negative geotropism

Answer 18

Where the plant grows opposing gravity (up)

Question 19

Where does negative geotropism occur

Answer 19

At the shoot tips

Question 20

What is positive geotropism

Answer 20

Where the plant grows with gravity (down)

Question 21

Where does positive geotropism occur

Answer 21

At the roots

Question 22

How are the shoots of plants controlled by IAA 6 marks

Answer 22

1. Cells in the tip of the shoot produces IAA which is then transported to the shoot
2. The IAA is initially transported evenly throughout the plant as it moves down the shoot

3.However light causes movement of IAA from the light side to the shaded side of the shoot

4. The greater conc of IAA builds up on the shaded side
5. As IAA causes elongation of shoot cells there is a greater conc on the shaded side of the shoot so the cells on this side elongate more
6. The shaded area elongates more than the light side causing the shoot tip to bend towards the light

Question 23

How does IAA affect the shoot

Answer 23

Causes cells to elongate

Question 24

How does IAA affect the roots

Answer 24

Inhibits cell growth

Question 25

How are the roots of plants controlled by IAA 6 marks

Answer 25

1. Cells in the root produces IAA which is then transported along the root
2. The IAA is initially transported to all sides of the roots

3.Gravity influences the movement of IAA from the upper to lower side of the root

4. A greater conc of IAA builds up on the lower side of the root
5. As IAA inhibits elongation of root cells there is a greater conc on the lower side of the root so the cells on this side elongate less
6. The relative elongation of cells on the upper side causes the roots to bend downwards with the force of gravity

Question 26

Describe how the plants could be selected at random in a field

Answer 26

-Set up tape measures on two sides of the plot / make grid of plot
-Use random number table / calculator / generator
-To generate coordinates

Question 27

Name the process by which IAA moves from the growing regions of a plant shoot to other tissues

Answer 27

Diffusion