CBSE Class 10 Science Life Processes Assignment Set 07

This is Assignment Set 07 for CBSE Class 10 Science Chapter 5, Life Processes, with 22 mixed practice questions of 1, 3 and 5 marks and one case based question. It covers egestion and excretion, emulsification, blood and lymph, transpiration and translocation, and gas transport in humans, and each answer is explained in steps.

Very Short Answer Questions (1 Mark Each)

Question 1. What is the source of energy used by plants during photosynthesis?
Answer:
Sunlight (light energy) is the source of energy used by plants during photosynthesis.
In simple words: Plants use the energy of sunlight.

Teacher's Note:
1. Chlorophyll absorbs this light energy.
2. Light energy is changed to chemical energy.

Question 2. In addition to carbon dioxide and water, state two other conditions necessary for the process of photosynthesis to take place?
Answer:
The two other conditions are sunlight and chlorophyll (the green pigment of the leaf).
In simple words: Photosynthesis needs light and chlorophyll too.

Teacher's Note:
1. Name the two conditions, not the raw materials.
2. Without chlorophyll light cannot be trapped.

Question 3. In the chemical reaction of the photosynthesis, which substance is the raw material as well as the product?
Answer:
Water is both a raw material and a product. In the full equation 6CO₂ + 12H₂O → C₆H₁₂O₆ + 6O₂ + 6H₂O, 12 molecules of water are used and 6 new water molecules are formed.
In simple words: Water is used up and also formed again in photosynthesis.

Teacher's Note:
1. Look at both sides of the full equation.
2. The net use is 6 water molecules.

Question 4. What is egestion?
Answer:
The removal of undigested waste material from the body, through the anus in the form of faeces, is called egestion.
In simple words: Egestion is throwing out the undigested food.

Teacher's Note:
1. Do not confuse egestion with excretion.
2. Excretion removes metabolic waste.

Question 5. In higher animals, what does ammonia react with to produce urea?
Answer:
In the liver, ammonia reacts with carbon dioxide to form urea, a much less toxic substance, which is later removed from the body.
In simple words: The liver turns toxic ammonia into urea using carbon dioxide.

Teacher's Note:
1. The reaction occurs in the liver.
2. Urea is less harmful than ammonia.

Question 6. Name the process of loss of water in the form of vapour from the aerial parts of the plants.
Answer:
The process is transpiration.
In simple words: Loss of water vapour from leaves is transpiration.

Teacher's Note:
1. Most of it happens through the stomata.
2. Do not confuse it with translocation.

Question 7. Name the form in which carbohydrates are stored in plants.
Answer:
Carbohydrates are stored in plants as starch.
In simple words: Plants store food as starch.

Teacher's Note:
1. Animals store glycogen.
2. Starch is tested with iodine.

Question 8. What is emulsification of fat?
Answer:
Emulsification is the breaking of large fat globules into many tiny droplets by the bile salts of the bile juice in the small intestine. It does not change the chemical nature of fat; it only increases the surface area so that the enzyme lipase can act better to form fatty acids and glycerol.
In simple words: Bile breaks big fat drops into tiny ones.

Teacher's Note:
1. Emulsification is a physical change.
2. The chemical breakdown into fatty acids is done by lipase.

Question 9. Name the component of blood that helps in the formation of blood clot in the event of a cut.
Answer:
The blood platelets help in the formation of a blood clot at a cut.
In simple words: Platelets make the blood clot.

Teacher's Note:
1. The clot stops loss of blood.
2. Platelets are also called thrombocytes.

Question 10. Name the cell organelle in which breakdown of pyruvate to give carbondioxide, water and energy takes place.
Answer:
The mitochondria (in the presence of oxygen).
In simple words: Mitochondria are the powerhouses where aerobic respiration is completed.

Teacher's Note:
1. The first step of glucose breakdown is in the cytoplasm.
2. Aerobic breakdown of pyruvate is in mitochondria.

Short Answer Questions (2 to 3 Marks Each)

Question 11. How is the small intestine designed to absorb digested food?
Answer:
The small intestine is the part in which most of the digested food is absorbed.
Its inner wall has numerous finger-like projections called villi, which greatly increase the surface area for absorption.
The villi are richly supplied with blood vessels, which take the absorbed food to every cell of the body for energy, growth and repair.
In simple words: Villi give a large surface and a good blood supply for absorption.

Teacher's Note:
1. Name the villi and the blood supply.
2. Say that the surface area increases.

Question 12. What advantage over an aquatic organism does a terrestrial organism have with regards to obtaining oxygen for respiration?
Answer:
Aquatic organisms such as fish use the oxygen dissolved in water. Terrestrial organisms take oxygen directly from the air.
The amount of oxygen dissolved in water is much less than the amount in air (about 21%), so a terrestrial organism gets oxygen more easily and can breathe at a slower rate, while aquatic animals have to breathe much faster.
In simple words: Air has far more oxygen than water, so land animals get oxygen more easily.

Teacher's Note:
1. Compare the oxygen in air and in water.
2. Link it with the breathing rate.

Question 13. What would be the consequences of deficiency of haemoglobin in the body?
Answer:
Haemoglobin in the red blood cells carries oxygen to all parts of the body.
If it is deficient, the cells do not get enough oxygen. The person feels weak and tired, looks pale and cannot do heavy work. This condition is called anaemia.
In simple words: Low haemoglobin means less oxygen for the body, so the person is weak and pale.

Teacher's Note:
1. Name anaemia.
2. Connect haemoglobin with oxygen supply.

Question 14. What are the components of the transport system in highly organised plants?
Answer:
The transport system of highly organised plants has two conducting tissues:
1. Xylem, which carries water and minerals from the roots to the other parts; it has tracheids, vessels, xylem parenchyma and fibres.
2. Phloem, which carries the food made in the leaves to all parts; it has sieve tubes, companion cells, phloem parenchyma and fibres.
In simple words: Xylem carries water and minerals; phloem carries food.

Teacher's Note:
1. Name both tissues and their cells.
2. State what each carries.

Question 15. How is the amount of urine produced regulated?
Answer:
The amount of urine depends on the quantity of excess water and the amount of dissolved waste in the body. When there is more of these, more urine is produced, and when there is less, less urine is produced.
It is controlled by how much water is reabsorbed in the nephron tubules. The hormone ADH, released from a gland at the base of the brain, also regulates the reabsorption of water.
In simple words: The kidneys reabsorb more or less water according to the needs of the body.

Teacher's Note:
1. Give the two factors.
2. Mention reabsorption of water.

Teacher's Note:
1. Make a table of cell and function.
2. Haemoglobin is in the RBCs.

Teacher's Note:
1. Give at least two points.
2. Mention haemoglobin in the first point.

Question 18. What is transpiration? Mention its importance to the plants.
Answer:
Transpiration is the loss of water in the form of vapour from the leaves and other aerial parts of a plant.
Importance:
1. Cooling: evaporation of water cools the plant on hot days.
2. Suction force: it helps in the upward movement of water and minerals (ascent of sap) through the xylem.
3. Distribution of water: it draws water to all the leaves.
4. It removes the excess water absorbed by the roots.
In simple words: Transpiration cools the plant and pulls water up.

Teacher's Note:
1. Define it before the importance.
2. Write at least two benefits.

Long Answer Questions (5 Marks Each)

Question 19. How are water and minerals transported in plants?
Answer:
Water and minerals are transported by the xylem.
1. The root hairs absorb water from the soil by osmosis and the minerals by active transport.
2. The water and minerals pass through the root cells and enter the xylem of the root. The xylem vessels of the root are joined to those of the stem and the leaves, so a continuous channel is formed.
3. In the leaves, water is lost as vapour through the stomata by transpiration. This creates a suction (transpiration pull) which draws the water up the xylem in a continuous column.
4. At night, when transpiration is low, the root pressure pushes the water upward.
In simple words: Roots absorb water; transpiration from leaves pulls it up through the xylem.

Teacher's Note:
1. Name the xylem, osmosis and transpiration pull.
2. Add root pressure for the night.

Question 20. How is food transported in plants?
Answer:
The transport of food from the leaves to the other parts of the plant is called translocation. It takes place through the phloem.
The phloem has sieve tubes, which are living cells joined end to end by sieve plates with small holes. They allow the food in the form of a solution to pass through.
The glucose made in the leaves is loaded into the sieve tubes using energy from ATP. Water then enters the tissue by osmosis, which raises the pressure. This pressure moves the food to the regions of lower pressure where it is needed, such as roots, fruits and growing tips.
Translocation can take place in both upward and downward directions.
In simple words: Leaf food enters the phloem using energy and is pushed to where it is needed.

Teacher's Note:
1. Name the phloem, sieve tubes and ATP.
2. Translocation is both upward and downward.

Question 21. (i) Explain the excretory system in human beings.
(ii) List four strategies used by plants for excretion.
Answer:
(i) The human excretory system has a pair of kidneys, a pair of ureters, a urinary bladder and a urethra.
The kidneys are bean-shaped organs in the abdomen on either side of the backbone. Each kidney has about a million nephrons, in which the blood is filtered and urine is formed. The ureters carry urine from the kidneys to the urinary bladder, where it is stored. The urine is passed out through the urethra.
(ii) Plants excrete by: (1) transpiration of excess water; (2) release of oxygen and carbon dioxide through the stomata; (3) storing wastes in cell vacuoles, and in leaves, bark and old xylem that are shed; (4) forming gums, resins and latex.
In simple words: Kidneys make urine, ureters carry it, the bladder stores it and the urethra releases it.

Teacher's Note:
1. Name the four parts of the system and their jobs.
2. Give four plant methods.

Question 22. How is oxygen and carbon dioxide transported in human beings?
Answer:
Oxygen: air enters through the nostrils and passes down to the alveoli. Oxygen diffuses from the alveoli into the blood capillaries and combines with haemoglobin in the red blood cells to form oxyhaemoglobin. The oxygenated blood goes to the left atrium by the pulmonary veins, and is then pumped by the heart to all the body cells.
Carbon dioxide: it is produced in the cells during respiration. It is carried mostly in dissolved form in the blood to the lungs, where it diffuses into the alveoli and is breathed out.
In simple words: Haemoglobin carries oxygen and the blood carries most of the carbon dioxide dissolved in it.

Teacher's Note:
1. Name haemoglobin for oxygen.
2. Say that carbon dioxide is more soluble in water.

Case Based Question (3 Marks)

Question 23. Multicellular organisms with small surface area to volume ratios need transport systems. Water and mineral salts are transported through a plant in xylem vessels. Transpiration is the process of water movement through a plant and its evaporation from aerial parts, such as leaves, stems and flowers. Water is necessary for plants but only a small amount of water taken up by the roots is used for growth and metabolism. The movement of sucrose and other substances like amino acids around a plant is called translocation. Translocation of organic solutes such as sucrose occurs through living phloem sieve tubes. Both xylem vessels and phloem sieve tubes show unique structural features which are adaptations to their roles in transport.
(A) When is the root pressure maximum?
(B) There are different tissues found in plants that help in translocation of substances. Write the functions of xylem and phloem in plants.
(C) Movement of substances like amino acids around a plant is called translocation. Which is the major driving force in the movement of water from ground to the root during day?
Answer:
(A) Root pressure is maximum when the rate of transpiration is very low and the absorption of water is high, for example at night.
(B) Xylem carries water and minerals from the soil to the different parts of the plant, only in the upward direction. Phloem carries the soluble products of photosynthesis from the leaves to the other parts, using energy from ATP. It also carries amino acids and other substances.
(C) In the day, the major driving force is the transpiration pull, which is created when water evaporates through the open stomata.
In simple words: Root pressure works at night; transpiration pull works in the day.

Teacher's Note:
1. Part (C): the answer is transpiration pull.
2. Name the direction of flow in each tissue.