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Q1. Which important function is carried out by the human heart?

Solution

The heart beats continuously to act as a pump for the transport of blood throughout the body.

Q2. List the factors which affect transpiration.

Solution

Factors affecting transpiration are

• Sunlight: During the day, the rate of transpiration is faster because stomata remain open which allows the inward diffusion of carbon dioxide for photosynthesis.
• Temperature: Transpiration is faster in summer as compared to winter.
• Wind: Transpiration is more when wind blows faster because water vapour is removed more quickly from the leaves.
• Humidity: Transpiration is reduced if the air is humid.

Q3. How the deoxygenated blood is reoxygenated?

Solution

The deoxygenated blood from different parts of the body enters the right auricle and is sent to the right ventricle. From here, the blood is pumped through the pulmonary artery to the lungs for reoxygenation. In lungs, the deoxygenated blood gives up carbon dioxide and absorbs oxygen from the inhaled air.

Q4. How is pulmonary artery different from any other artery?

Solution

An artery carries oxygen-rich blood but the pulmonary artery carries carbon dioxide-rich blood to the lungs.

Q5. A pigment is responsible for the Red colour of blood Name it.

Solution

Haemoglobin.

Q6. Which blood cells act as soldiers of our body?

Solution

White blood cells acts as soldiers of our body. White blood cells fight against germs that enter our body either by destroying them or by producing antibodies against them; hence prevent us from infections.

Q7. Transpiration nourishes the plant. Explain.

Solution

Transpiration brings about transport of minerals because the water pulled from the roots also contains certain minerals. Thus, it nourishes the plant.

Q8. Write the function of:(a) Xylem(b) Phloem

Solution

(a) Xylem transports water and nutrients in the plants.(b) Phloem transports food to all parts of the plant.

Q9. (a) In summer, why do we find white patches on our clothes, especially in areas like underarms? (b) Describe the excretory products of birds and lizards.

Solution

(a) On a hot summer day, we sweat a lot. Sweat contains water and salts. The water of sweat evaporates, leaving behind the salts which appear as white patches on our clothes.(b) Birds and lizards excrete a semi-solid, white coloured compound, the uric acid.

Q10. Which principle is involved in the functioning of an artificial kidney?

Solution

Dialysis.

Q11. What is transpiration? How is it important to plants?

Solution

Transpiration is the evaporation of water from aerial parts of plants, especially from leaves into the atmosphere. Importance: (i) It generates a force due to which water absorbed by roots is pulled upwards to the aerial parts of the plant. (ii) Transpiration also helps in cooling the plant.

Q12. What is the function of the red pigment of blood? Where is this pigment present in blood?

Solution

Haemoglobin, the red pigment of blood, binds with oxygen and transports it to all the parts of the body and ultimately to all the cells. It is present in the red blood cells of blood.

Q13. Describe an activity to show transportation of water through cells.

Solution

i. Take a large potato, peel off its outer skin and cut one of its ends to make the base flat. ii. Now, make a deep and hollow cavity on the opposite side. iii. Fill half of the cavity with sugar solution and mark the level by inserting a pin in the wall of the potato. iv. Put the potato into a dish containing a small amount of water. Make sure that the level of water is below the level of the pin. v. Allow the apparatus to stand for few hours. vi. We would observe an increase in the level of sugar solution. This is because for very short distances water can move from one cell to another. In this way, water reaches xylem vessels of the root from the soil.

Q14. Differentiate between artery, vein and capillary.

Solution

Artery Vein Capillary i. Thick-walled. ii. Carry oxygen-rich blood from the heart to other parts of the body. i. Thin-walled. ii. Carry carbon dioxide-rich blood from different organs to the heart. i. Thin-walled. ii. Capillaries are involved in the exchange of food material, respiratory gases, and body wastes.

Q15. Name any four excretory organs in humans and mention one function of each organ.

Solution

Kidneys: They are a pair of bean-shaped, reddish brown organs that help in maintaining the water and salt concentration of blood by the process of osmoregulation. Ureters: They carry urine from each kidney to the urinary bladder. Urinary bladder: They store urine until it is expelled from the body. Urethra: It is a short tube through which urine is passed out.

Q16. Name the important parts of the human excretory system.

Solution

Human excretory system consists of a pair of kidneys, a pair of ureters, urinary bladder and urethra.

Q17. How are the useful and harmful substances in blood dealt by the kidney?

Solution

The useful substances are absorbed back into the blood and the harmful wastes dissolved in water are removed as urine.

Q18. Give two functions of blood.

Solution

1. Blood carries oxygen from the lungs to the other cells of the body. 2. It transports waste for removal from the body.

Q19. Write the importance of: (i) Stethoscope (ii) Atrium (iii) Ventricle

Solution

(i) Stethoscope - It amplifies the sound of the heart, hence doctors can feel the heartbeats of the patient and get clues about the heart condition. (ii) Atrium - It receives blood from various parts of the body. (iii) Ventricle - It supplies blood to different parts of the body.

Q20. List the excretory products of the following organs: Kidneys, lungs, skin and liver

Solution

Kidneys - Urea, uric acid, creatinine, ammonia, sodium chloride, excess water Skin - Sodium chloride, water, some urea Lungs - Carbon dioxide, water vapour Liver - Bile pigments

Q21. Discuss how a heartbeat is formed?

Solution

The walls of the chambers of the heart are made up of muscles. These muscles contract and relax rhythmically. This rhythmic contraction followed by its relaxation constitutes a heartbeat.

Q22. What is the importance of root hairs for absorption?

Solution

The root hair increase the surface area of the root for the absorption of water and mineral nutrients dissolved in water.

Q23. (a) Where is food synthesized in plants? How do the rest of the plant parts receive this food? (b) Name the factors responsible for transpiration.

Solution

(a) Food is synthesized in the leaves of plants. This food is transported using the vascular tissue called phloem to all other parts of the plant. (b) Time of the day, temperature, humidity, wind and light are responsible for transpiration.

Q24. What is the need for excretion in our body?

Solution

When our cells perform various functions, certain waste products are released. These are toxic and hence need to be removed from the body by the process of excretion.

Q25. Explain the structure of kidney.

Solution

The structure of kidney:

• The kidney is about 11-14 cm in length, 6cm wide and 4cm thick.
• Kidneys have an outer cortex consisting of dark tissues and an inner medulla consisting of lighter tissues.
• A funnel-shaped cavity called the renal pelvis is present on the concave side of kidneys.
• Each kidney is made up of millions of microscopic units called nephrons which deal with the formation of urine from blood.
• Each nephron consists of a cup-shaped structure called Bowman’s capsule, which further divides into a cluster of minute capillaries called glomerulus where filtration occurs.
• Renal arteries supply blood to the kidneys, hence they break into small branches and supply blood to each nephron within which the blood is filtered to remove waste products like urea, uric acid, creatinine, ammonia, salts and water.

   

Q26. Why it is essential that food must be made available to every cell of the plant?

Solution

Food is the source of energy and every cell of an organism gets energy by the breakdown of glucose. The cells use this energy to carry out vital activities of life. Therefore, food must be made available to every cell of an organism.

Q27. Which blood cells form the clot?

Solution

Platelets form a network of cells on the cut or wound and thus forms a blood clot.

Q28. How the urine is excreted out?

Solution

Urine is excreted out through the urinary opening at the end of a muscular tube called urethera.

Q29. Why is the water kept in an earthen pot cooler?

Solution

This is because the water evaporates from the pores of the pot, which causes cooling.

Q30. How does kidney failure occur? What can be done to help the survival of such people?

Solution

Sometimes a person's kidneys may stop working due to infection or injury. This is called kidney failure due to which waste products start accumulating in the blood. For the survival of such people, it is essential that their blood is filtered periodically through an artificial kidney. This process is called dialysis.

Q31. After the production of urine it is stored temporarily in an organ. Name it.

Solution

Urinary bladder.

Q32. Write any three functions of the fluid which flows in blood vessels.

Solution

The fluid which flows in blood vessels is blood. Its functions are: (i) It transports substances like digested food from the small intestine to the other parts of the body. (ii) It carries oxygen from the lungs to the cells of the body. (iii) It also transports waste materials for removal from the body.

Q33. How is a pulse generated? What does the pulse rate indicate?

Solution

Each heart beat generates one pulse in the arteries. The pulse rate indicates the rate of heartbeat.

Q34. (a) What is vascular tissue? (b) What happens to the excessive water absorbed by roots?

Solution

(a) Vascular tissue is the tissue that conducts water and nutrients through the plant body in higher plants. Xylem and phloem are vascular tissues.(b) Some of the water absorbed by plant roots is used by the plants. But most of the water evaporates through the stomata present on the surface of leaves through transpiration.

Q35. Give reason: (i) Though pulmonary artery carries carbon-dioxide rich blood, it is still called as artery and not vein. (ii) Arteries have thick, elastic walls. (iii) Blood of all humans are red in colour.

Solution

(i) This is because pulmonary artery carries blood away from the heart and not towards it like a vein does. (ii) Since the blood flow through arteries rapidly at high pressure, the arteries have thick elastic walls. (iii) The red blood cells contain a red pigment called haemoglobin. The presence of haemoglobin makes blood appear red.

Q36. What are veins? What prevents the back flow of blood from veins?

Solution

Veins are vessels which carry carbon dioxide-rich blood from all parts of the body back to the heart. There are valves present in veins which allow blood to flow only towards heart and thus prevents the back flow of blood from veins.

Q37. What is the function of blood plasma?

Solution

Blood plasma carries the dissolved substances like proteins, digested food and salts from one part of the body to another.

Q38. Diagrammatically show the blood circulation in human body.

Solution

Q39. Usually, how much urine is excreted by an adult in a day? What is the percentage of urea in urine?

Solution

1-1.8 litres of urine is excreted by an adult in a day. About 2.5% of urea is present in the urine.

Q40. How do plants obtain water and nutrients? How are these transferred to all parts of the plant?

Solution

Plants take water and mineral nutrients from the soil through the roots and transport it to the leaves through a vascular tissue called xylem. The xylem forms a continuous network of channels that connects roots to the leaves through the stem and branches and thus transports water and nutrients to the entire plant.

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