Intext Questions ( page no. 111)

1. How does chemical coordination take place in animals?

Ans. The hormones in animals are part of endocrine gland which helps in control and coordination.

— Different hormones reach till target organs by blood and performs chemical coordination by being in coordination with each other.

— Hormones Adrenaline secreting from adrenal gland mixes with blood and prepares animal body to fight with scary situations. Heart beats faster, breathing rate increases, muscles get sufficient oxygen.

— The hormone secreted from pancreas insulin, maintains / controls the level of sugar in the body.

— Thus chemical balance is maintained in animal bodies.

2. Why is the use of iodised salt advisable?

Ans. Hormone thyroxin is secreted from a thyroid gland.

— Iodine is essential for synthesis of thyroxin.

— With the help of thyroxin metabolism of main elements of food carbohydrates, protein, fat is done.

— Due the deficiency of thyroxin a disease called goiter is caused.

 

3. How does our body respond when adrenaline is secreted into the blood?

Ans. Adrenaline prepares our body in an emergency situation. When adrenaline is secreted into the blood body shows following responses :

— The heart beats faster, breathing rate increases, blood pressure increases, skeletal muscles become more active, etc.

— This is known as fight or flight response.

4. Why are some patients of diabetes treated by giving injections of insulin?

Ans. When the level of sugar increases in blood of a person, the deficiency caused is called Diabetes.

— The regulation of level of sugar in blood is done by hormone Insulin secreted from pancreas.

— If insulin is not secreted in proper amount from pancreas, the sugar level in the blood rises causing Diabetes. So by giving insulin injection to patients, the level of sugar is maintained in blood.

                                                                         Exercise 

1. Which of the following is a plant hormone ?

(A) Insulin        (B) Thyroxin      (C) Oestrogen     (D) Cytokinin

Ans. (D) Cytokinin

2. The gap between two neurons is called a

(A) Dendrite       (B) Synapse       (C) Axon         (D) Impulse

Ans. (B) Synapse

3. The brain is responsible for

(A) Thinking                                 (B) Regulating the heart beat

(C) Balancing the body              (D) All of the above

Ans. (D) All of the above

4. What is the function of receptors in our body ? Think of situations where receptors do not work properly. What problems are likely to arise ?

Ans. Receptors are specialised cells located in our sense organs like ear, nose, skin, tongue and eyes. The function of receptors is to detect information from the environment. For example, olfactory receptors detect smell. If receptors do not work properly, the information obtained from the environment will be delayed to reach the spinal cord or brain. In this situation, the response to the environmental stimulus will be delayed causing harm to the body. For example, if skin receptors are damaged, and one accidentally touches a hot object, then his/her hands might get burn as the damaged receptor cannot perceive the external stimuli of heat and pain.

5. Draw the structure of a Neuron and Explain its function.

Ans. Nerve cell or neuron is the functional unit of nervous system. A nerve cell has three parts-

(i) cell body

(ii) dendrite

(iii) axon

Function: The function of nerve cells is to carry information in the form of electrical signals which are called nerve impulses. Cells receive stimulus to send it to spinal cord and brain and carry the message from brain to the target organ.

6. How does phototropism occur in plants ?

Ans. Procedure:

— Fill a conical flask with water.

— Cover the neck of the flask with a wire mesh.

— Keep two or three freshly germinated bean seed on the wire mesh.

— Take a cardboard box which is open from one side.

— Keep the flask in the box in such a manner that the open side of the box faces light 

coming from a window.

Observation :

After two or three days, the shoots bend towards light and roots away from light.

Conclusion :

Plants shoot shows positive photo tropism and root shows negative photo tropism.

7. Which signals will get disrupted in case of a spinal cord injury?

Ans. All the involuntary actions will get disturbed.

— Reflex actions will be disturbed because reflexes are located in the spinal cord. Therefore, the quick responses required to safe guard the body will not take place.

8. How does chemical coordination occur in plants?

Ans. Different plant hormones help to coordinate growth, development and responses to the environment.

— Hormones are synthesized at places away from where they act and diffuse to the area of action.

Eg. Auxin helps the cells to grow.

Gibberellins help in the growth of stem.

Cytokinin promotes cell division.

Abscisic acid inhibits growth. Its effects cause wilting of leaves.

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

Ans. An organism needs control and coordination system for the following functions:

(i) To save the body of the organisms from the harmful changes in the Environment.

(ii) To control the speed of voluntary and involuntary actions.

(iii) To have the capability to think and learn for responding to any stimuli.

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

Ans.