A liquid X of colour Y circulates in the human body only in one direction: from body tissues to the heart. Among other things, liquid X contains germs from cells and dead cells. The liquid X is cleaned of germs and dead cells by a special type of white blood cells called Z. This cleaned liquid is then put into blood circulatory system in subclavian veins.

1. What is (i) liquid X and (ii) colour Y?
2. What are Z.
3. The liquid X is somewhat similar to a component of blood. Name this component.
4. Why is liquid X not red?

1. Draw a sectional view of the human heart and label on it: Aorta, Pulmonary arteries, Vena cava, Left ventricle.
2. Why is double circulation of blood necessary in human beings?

Write the difference between nutrition in plants and animals.

There is a pair of bean-shaped organs P in the human body towards the back, just above the waist. A waste product Q formed by the decomposition of unused proteins in the liver is brought into organ P through blood by an artery R. The numerous tiny filters S present in organ P clean the dirty blood by removing the waste product Q. The clean blood goes into circulation through a vein T. The waste substance Q, other waste salts, and excess water form a yellowish liquid U which goes from organ P into a bag-like structure V through two tubes W. This liquid is then thrown out of the body through a tube X.

1. What is (i) organ P and (ii) waste substance Q?
2. Name (i) artery R, and (ii) vein T.
3. What are tiny filters S known as?
4. Name (i) liquid U, (ii) structure V, (iii) tubes W and (iv) tube X.

State one difference between artificial kidney and natural kidney?

When a person puts food in his mouth, then teeth cut it into small pieces, chew and grind it. The glands A in the mouth secrete a substance B which is mixed with the food by tongue. The substance B contains an enzyme C which starts the digestion of food in the mouth. The slightly digested food from the mouth goes down a tube D. The special type of movements E in the walls of tube D push the food into stomach for further digestion. The stomach wall secretes gastric juice containing three substance F, G and H. One of the functions of F is to kill bacteria which may enter the stomach with food. The substance G protects the inside layer of stomach from the damaging effect of substance F whereas substance H is and enzyme for digestion. The partially digested food then enters into small intestine for further digestion.

1. What is Gland A, Substance B and Enzyme C?
2. Name the tube D.
3. What is the movement E known as?
4. What are F, G and H?

Describe the alimentary canal of man.

If a person holds his breath after expiration for about 25sec, would there be occurrence of any exchange of respiratory gases in the lungs during this period? Explain.

1. Draw a diagram of human alimentary canal and label - gall bladder, pancreas, liver and small intestine on it.
2. Give two reasons to explain why absorption of digested food occurs mainly in the small intestine.

Explain the process of nutrition in Amoeba.