NCERT Class X Science Solutions: Chapter 7 – Control and Coordination Part 3

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Question 9:

What is the need for a system of control and coordination in an organism?

Answer 9:

The maintenance of the body functions in response to changes in the body by working together of various integrated body systems is known as coordination. All the movements that occur in response to stimuli are carefully coordinated and controlled. In animals, the control and coordination movements are provided by nervous and muscular systems. The nervous system sends messages to and away from the brain. The spinal cord plays an important role in the relay of messages. In the absence of this system of control and coordination, our body will not be able to function properly.

For example: when we accidentally touch a hot utensil, we immediately withdraw our hand. In the absence of nerve transmission, we will not withdraw our hand and may get burnt.

Question 10:

How are involuntary actions and reflex actions different from each other?

Answer 10:

Involuntary actions cannot be consciously controlled. For example, we cannot consciously control the movement of food in the alimentary canal or pumping of blood through heart. These actions are however directly under the control of the brain. On the other hand, the reflex actions such as closing of eyes immediately when bright light is focused show sudden response and do not involve any thinking. This means that unlike involuntary actions, the reflex actions are not under the control of brain.

Result for Reflex Arc

Reflex Arc

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Question 11:

Compare and contrast nervous and hormonal mechanisms for control and coordination in animals.

Answer:

Difference between nervous and hormonal systems

Nervous system mechanism

Hormonal system mechanism

1.

The information is conveyed in the form of electric impulse.

1.

The information is conveyed in the form of chemical messengers.

2.

The axons and dendrites transmit the information through a coordinated effort.

2.

The information is transmitted or transported through blood.

3.

The flow of information is rapid and the response is quick.

3.

The information travels slowly and the response is slow.

4.

Its effects are short lived.

4.

It has prolonged effects.

Question 12:

What is the difference between the manner in which movement takes place in a sensitive plant and the movement in our legs?

Answer:

Movement in plants and animals

Movement in sensitive plants

Movement in our legs

1.

The movement that takes place in a sensitive plant such as Mimosa pudica occurs in response to touch (stimulus).

1.

Movement in our legs is an example of voluntary actions.

2.

For this movement, the information is transmitted from cell to cell by electrochemical signals as plants do not have any specialised tissue for conduction of impulses.

2.

The signal or messages for these actions are passed to the brain and hence are consciously controlled.

3.

For this movement to occur, the plant cells change shape by changing the amount of water in them.

3.

In animal muscle cells, some proteins are found which allow the movement to occur.