Simple Responses

Question 1

What are simple responses?

Answer 1

Rapid automatic responses protect the organisms from harmful stimuli.

Question 2

What is a stimulus?

Answer 2

A change in the external and internal environment.

Question 3

What are receptors?

Answer 3

They are cells or proteins in cell membrane that detect a stimulus.

Question 4

What is an effector?

Answer 4

A muscle or gland that brings about a response.

Question 5

How does the nervous system detect the stimulus and bring about a simple reflex in response to it?

Answer 5

1. The receptors detect the stimuli and send electrical impulses along the sensory neuron
2. The sensory neuron carries the electrical impulse from the receptors to the CNS.
3. The relay neurone allows the electrical impulse to be transferred from the sensory neurone to the motor neurone.
4. The motor neurone carries the electrical impulse from the CNS to the effector.
5. The effector brings about a response.

Question 6

Why is it important that organisms respond to changes in their environment?

Answer 6

It increases their chances of survival.

Question 7

What are taxi responses?

Answer 7

A directional movement in response to a directional stimulus.

Question 8

What is an example of a taxi response?

Answer 8

A shoot undergoing positive phototropism in response to light and the roots undergoing negative phototropism in response to light.

Question 9

What is a kinesis response?

Answer 9

1. A non-directional movement in response to a stimulus.
2. The direction and speed of the movement may change.
3. They depend on the intensity of the stimulus.

Question 10

Why are taxis and kinesis responses important?

Answer 10

They keep a mobile organism in a favourable environment.

Question 11

Explain the protective effect of a simple reflex.

Answer 11

1. They are rapid.
2. They are automatic, so they don’t have to be learnt.
3. This protects organisms from harmful stimuli.