Survival and Response

Question 1

Organisms [1] their chance of survival by responding to [2] in their environment.

Answer 1

[1] increase

[2] changes

Question 2

List two simple responses by small organisms such as insects

Answer 2

Taxis

Kinesis

Question 3

Function of taxis and kinesis for mobile organisms

Answer 3

1. Keep organisms in a favourable environment.
   (e.g. more food, more mates, less predators, less desiccation)
2. Increase chances of survival

Question 4

Define taxis

Answer 4

Directional movement in response to a stimulus

Question 5

Positive taxis

Answer 5

Directional response with movement towards the stimulus

Question 6

Negative taxis

Answer 6

Directional response with movement away from the stimulus

Question 7

Define kinesis

Answer 7

Random OR non-directional movements in response to the stimulus

Question 8

Give one similarity and one difference between a taxis and a tropism.

Answer 8

similarity − directional response to a stimulus / movement towards OR away from a stimulus;

Difference − in taxis whole organism moves whereas tropism a growth response in part of the plant (e.g. shoot or root tips).

OR

Difference - taxis occurs in animals whereas tropisms

Question 9

In flowering plants, specific [1] factors move from growing regions to other tissues, where they regulate growth in response to directional [2].

Answer 9

[1] growth

[2] stimuli

Question 10

Which organisms demonstrate tropisms?

Answer 10

Plants

Question 11

Define tropism

Answer 11

Response of a plant to a directional stimulus

Question 12

Stimuli that cause tropisms

Answer 12

Light
Gravity
Water
Salinity

Question 13

Positive phototropism

Answer 13

Directional response of shoot tips towards light

Question 14

Directional response of root tips away from light

Answer 14

negative phototropism

Question 15

Positive gravitotropism

Answer 15

Directional response of root tips towards gravity

Question 16

Auxis are a family of growth factors that cause tropisms. Which specific auxin must you know.

Answer 16

IAA

Full name: Indoleacetic acid

Question 17

Where is IAA synthesised?

Answer 17

Shoot tips &
root tips

Question 18

How does IAA move into the growing region of the shoot or root tip?

Answer 18

Diffusion

Question 19

Where does IAA build up in the shoot tips in response to light?

Answer 19

On the shaded side

Question 20

Effect of IAA in the shoot tips

Answer 20

1. Stimulates elongagation of cells on the shaded side;
2. Causes shoot to bend towards the light;
   (this is a positive phototropism)

Question 21

Where does IAA build up in the root tips in response to gravity?

Answer 21

On the side closest to gravity / on the underside

Question 22

Effect of IAA in the root tips

Answer 22

Inhibits elongagation of cells on the underside;
Cells on opposite side (away from gravitiy) can elongate and cause the root tip to bend towards gravity;

Question 23

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 marks).

Answer 23

1. Causes plant to bend / grow towards light / positive phototropism;
2. Light energy required for photosynthesis;

Question 24

TRUE or FALSE:

IAA is only produced in the light

Answer 24

FALSE

IAA is produced in the light AND dark

Question 25

Which neuron in the simple reflex arc contains receptors to the stimulus?

Answer 25

Sensory

Question 26

Suggest two advantages of simple reflexes

Answer 26

Rapid; Protect against damage to body tissues; Do not have to be learnt / innate behaviour / involuntary; Help escape from predators; Enable homeostatic control; Finding suitable conditions / keep organism in favourable environment;

Question 27

Give two types of cell that act as effectors.

Answer 27

Muscles Glands (which produce hormones)

Question 28

What is found between the sensory neuron and relay neuron

Answer 28

synapse