Q. 1. Name the most essential factor for life ?

Ans. Movement of molecules in the cells and tissues is the most essential condition for something to be alive.



Q. 2. What do you mean by life processes ?

Ans. The processes that together perform the repairing and maintaining the job of living structures are called life processes.



Q. 3. Why is nutrition essential for an organism ?

Ans. Nutrition is essential to provide an organism with the energy required to perform various life activities.



Q. 4. Define photosynthesis.

Ans. The process by which green plants prepare their own food from carbon dioxide and water in the presence of sunlight and chlorophyll is called photosynthesis.



Q. 5. Name the organelle in which photosynthesis occurs.

Ans. Photosynthesis occurs in ‘Chloroplasts’.



Q. 6. Write the balanced chemical equation for the process of photosynthesis.

6CO2 + 6H2O
C6H22O6 + 6O2



Q. 7. What do you mean by autotrophic nutrition ?

Ans. In autotrophic nutrition, the process by which autotrophs, i.e., green plants and some bacteria use CO2 and H2O to convert them into glucose in the presence of sunlight and chlorophyll.



Q. 8. What are heterotrophs ?

Ans. The organisms which depend on others for their food are called heterotrophs.



Q. 9. What are autotrophs ?

Ans. Plants and a few bacteria which prepare their own food are called as autotrophs.



Q. 10. Name the mode of nutrition in amoeba.

Ans. Holozoic nutrition.



Q. 11. Which pigment is present in plants that can absorb solar energy ?

Ans. Chlorophyll.



Q. 12. Name the two stages of photo-synthesis.

Ans. The two stages of photosynthesis are
(a) Light reaction or Hill’s reaction, and
(b) Dark reaction or Blackman’s reaction.



Q. 13. What do you mean by holozoic nutrition ?

Ans. The nutrition in which organisms take solid food.



Q. 14. What is compensation point ?

Ans. It means the intensity of light at which the photosynthetic intake of CO2 is equal to the respiratory output of CO2.



Q. 15. What are enzymes ?

Ans. Enzymes are the bio-catalyst substances which help in completion biochemical processes like digestion of food, cellular respiration etc.



Q. 16. What is the function of bile on the food ?

Ans. Bile is secreted by liver. It does not have any enzyme. It emulsifies the fats into smaller globules.



Q. 17. What is cellular ?

Ans. The process of acquiring oxygen from outside the body and using it in the process of breakdown of food sources to release energy for cellular needs is known as cellular respiration.



Q. 18. Why is the food crushed in the buccal cavity and wetted before it makes its passage into the alimentary canal ?

Ans. As the lining of the alimentary canal is soft, the food is crushed and wetted in the buccal cavity to make its passage smooth.



Q. 19. What is alimentary canal ?

Ans. It is a long tube extending from the mouth to the anus.



Q. 20. How does dental caries start ?

Ans. Dental caries starts when bacteria acting on sugars produce acids, thus softening the enamel.



Q. 21. Name the four kinds of teeth present in human mouth.

Ans. Incisors, Canines, Premolars and Molars.



Q. 22. What is peristalsis ?

Ans. It is the continuous contraction and expansion in the stomach which pushes the food downward in the alimentary canal.



Q. 23. Name the digested form of proteins.

Ans. Amino acids.



Q. 24. Name the digested products of fats.

Ans. Fatty acid and glycerol.



Q. 25. What is the name given to the digested form of carbo-hydrates and sugars ?

Ans. Glucose.



Q. 26. Name the vestigial part of human alimentary canal.

Ans. Vermiform appendix.



Q. 27. What are stomata ?

Ans. The tiny holes found on the surface of the leaves through which exchange of gases takes place and some amount of water is evolved in the form of vapours are called stomata.



Q. 28. Name the respiratory organs of animals like fish that live in water.

Ans. Gills.



Q. 29. Haemoglobin is a type of :
(a) Carbohydrate
(b) Skin pigment
(c) Vitamin
(d) Respiratory pigment.

Ans. (d) Respiratory pigment.



Q. 30. What is breathing ?

Ans. It is the process of intake of oxygen from the environment and releasing carbon dioxide into the environment.



Q. 31. What is the function of anal sphincter ?

Ans. Anal sphincter regulates the exit of waste materials via the anus.



Q. 32. Name the enzyme present in saliva. What is its role ?

Ans. Salivary amylase that breaks starch (a complex molecule) to give sugar.



Q. 33. What do you mean by double circulation ?

Ans. The circulation of blood through the heart twice during each cycle of blood circulation is known as double circulation.



Q. 34. Which process of respiration releases more energy ?

Ans. Aerobic respiration.



Q. 35. What is the function of the rings of cartilage present in the throat ?

Ans. The rings of cartilage ensure that the air-passage does not collapse when air is moved out of the passage.



Q. 36. What is excretion ?

Ans. The biological process involved in the removal of harmful metabolic wastes (nitrogenous materials) from the body is called excretion.



Q. 37. What is the function of plant transport system ?

Ans. Plant transport system transports energy stores from leaves and raw materials from roots.



Q. 38. What is ‘Osmoregulation’ ?

Ans. It is the process of maintaining the right amount of water and proper ionic balance in the body.



Q. 39. Name the factors that can reduce the activity of kidneys.

Ans. (i) Infections, (ii) injury and (iii) restricted blood flow to kidneys.



Q. 40. Name the largest artery in our body.

Ans. Aorta.



Q. 41. Name the instrument that is used to measure the blood pressure.

Ans. Sphygmomanometer.



Q. 42. Name the type of blood vessels which carry blood form organs to the heart.

Ans. Arteries.



Q. 43. Define osmosis.

Ans. Osmosis is the movement of solute particles from a region of higher concentration to a region of lower concentration.



Q. 44. How does diaphagm help in inspiration ?

Ans. It flattens during inspiration, thus increasing the volume of the thoracic cavity.



Q. 45. What is the function of valves present in heart ?

Ans. The presence of these valves ensures that blood does not flow backwards when the atria or ventricles contract.



Q. 46. What is the function of platelet cells in the blood ?

Ans. They help in the clotting of the blood.



Q. 47. Name the respiratory organs of :
(i) fish
(ii) mosquito
(iii) earthworm.

Ans. (i) Gills (ii) Air tubes
(iii) Body surface.



Q. 48. The basic functional unit of kidney is
(a) Henle’s loop   (b) Nephron   (c) Nephridium   (d) Pyramid.

Ans. (b) Nephron.



Q. 49. Name the excretory organs of cockroach.

Ans. Malpighian tubules.



Q. 50. What are nephridia ?

Ans. The excretory organs in earthworm are called nephridia.





Q. 1. In which form is nitrogen taken up by the plants ?

Ans. Nitrogen is taken either in the form of inorganic nitrates or nitrites, or as organic compounds which have been prepared by bacteria from the atmospheric nitrogen.



Q. 2. How do autotrophs meet their energy requirements ?

Ans. Autotrophs meet their energy requirements through the process of photosynthesis.
• Light energy is taken by chlorophyll.
• Water is taken up from the soil by roots (in terrestrial plants).
• Nitrogen, phosphorus, iron and magnesium are taken up from the soil.



Q. 3. Describe briefly the series of events that take place during photosynthesis.

Ans. During photosynthesis, the following events take place :
(a) Absorption of light energy by chlorophyll.
(b) Conversion of light energy into chemical energy and splitting of water molecules into hydrogen and oxygen.
(c) Reduction of CO2 gas into carbohydrates.



Q. 4. Why is nutrition essential for an organism ?

Ans. Nutrition is essential for an organism for :
(i) Obtaining energy, as energy is required for performing all the life processes.
(ii) Growth : It is an internal, permanent and slow process which also needs energy.
(iii) Repair and maintenance : As some cells and tissues in body parts rupture and die, their repair and replacement is necessary for which they need energy.
(iv) Building up resistance against diseases.



Q. 5. Differentiate autotrophic nutrition and heterotrophic nutrition.

Ans. Differences between autotrophic nutrition and heterotrophic nutrition :–
Autotrophic nutrition :
1. It occurs in green plants and some bacteria.
2. They need chlorophyll and sunlight.
3. CO2 and H2O combine together to form organic compounds.
4. They take in inorganic components as their food.
Heterotrophic nutriton :
1. It occurs in animals and insect-ivorous plants.
2. These are not needed.
3. In this type of nutrition, organisms depend on plants and herbivores for their food.
4. They take inorganic components as their food.



Q. 6. What do you understand by chemoautotrophs ?

Ans. The organisms which do not require light and prepare their food from inorganic substances in the presence of energy derived from the oxidation of simple compounds like iron, sulphur etc. are called chemoautotrophs, e.g., bacteria, nitrosomonas.



Q. 7. Describe the role of saliva in the digestion of food ?

Ans. Saliva contains an enzyme salivary amylase, ptyalin, a simple sugar which is easily digested, which helps in the breakdown of starch.
Apart from that, saliva also helps in thorough mixing of food which further helps in the easy movement of food in the oesophagus as well as in the alimentary canal.



Q. 8. What is the role of stomach in digestion of food ?

Ans. Stomach is a large organ that expands when food enters it. Muscular walls of the stomach help in churning the food thoroughly.



Q. 9. Which take place in the duodenum ?

Ans. In the duodenum, (a) Bile emulsifies the fat molecules present in the food. (b) Trypsin starts digesting the proteins and the pancreatic amylase breaks down the starch. (c) The duodenal wall secrets bicarbonate ions to make the medium alkaline, so that the pancreatic enzymes act on the food.



Q. 10. What is the role of the glands present in the small intestine’s walls ?

Ans. These glands secrete intestinal juice, the enzymes present which finally convert the proteins into amino acids, complex carbohydrates into glucose and fats into fatty acids and glycerol.



Q. 11.What is the function of large intercellular spaces present in plants ?

Ans. These large inter-cellular spaces ensure that all cells are in contact with air, and both CO2 and O2 are exchanged by diffusion in these spaces.



Q. 12. What is the function of sphincter muscle of the stomach ?

Ans. The sphincter of the stomach regulates the exit of food from the stomach in small amounts into the small intestine.



Q. 13. What do you mean by glycolysis ?

Ans. The process of breakdown of glucose into a pyruvate, a three carbon molecule, is called glycolysis.



Q. 14. What do you mean by peristaltic movements ?

Ans. The rhythmic contraction of muscles which takes place all along the alimentary canal is referred to as peristaltic movements. These movements help to push the food forward.



Q. 15. Small intestine is referred to as the site of the complete digestion, why ?

Ans. Small intestine receives the secretions of the liver and pancreas which help in the complete digestion of carbohydrates, proteins and fats. Thus it is lightly referred to as the site of complete digestion.



Q. 16. Draw a labelled diagram to show the human duodenum and the duct system of the associated digestive glands pouring into it.





Q. 17. What are villi ?

Ans. The finger-like projections present in the inner walls of the small intestine are called villi. They increase the surface area for absorption.



Q. 18. Why does the heart have different chambers ?

Ans. As both oxygen and carbon dioxide have to be transported by the blood, it has different chambers to prevent the oxygen-rich blood from getting mixed with the blood containing carbon dioxide.



Q. 19. Describe briefly the mechanism of blood clotting.

Ans. When the blood flows out from a damaged blood vessel and gets exposed to air, the platelet cells release a substance called thromboplastin, which converts the prothrombin present in the blood plasma into thrombin. Thrombin acts as a catalyst and converts soluble protein fibrinogen present in blood plasma into an insoluble protein called fibrin.Fibrin in turn makes a thick mesh across the wound and RBCs get entangled into the mesh to form a blood clot.



Q. 20. Write the main functions of blood in our body.

Ans. The main functions of blood in our body are –
(i) It transports O2 to various body parts.
(ii) It transports waste products from various organs to the excretory organs.
(iii) It protects the body from harmful bacteria, viruses, protozoans etc. and it also maintains the body temperature.



Q. 21. How is excretion different from osmoregulation ?

Ans. Excretion means the removal of water substances produced in body due to metabolic activities. On the other hand, osmoregulation refers to the control of excess water and ions in the body of an organism.



Q. 22. Why is circulation of blood in man known as double circulation ?

Ans. The blood circulates two times in the human heart :
(i) Systemic circulation
(ii) Pulmonary circulation.
The impure blood coming from various parts of the body is collected in the right atrium from where it is sent to the lungs through the pulmonary artery. Blood is purified in the lungs. It is then sent to the left auricle or atrium from where it comes into ventricle and then to various parts of the body through aorta. Thus blood comes into the heart two times, and the circulation is called double circulation.





Q. 1. Which three substances are contained in the gastric juice ? What are their functions ?

Ans. Gastric juice contains the following three substances :
Hydrochloric acid, enzyme pepsin and mucus.
Functions :
(i) In the stomach HCl is used to make the medium of gastric juices acidic and to kill germs, if any and to activate pepsin enzyme.
(ii) Enzyme pepsin attacks the proteins to convert them into peptones.
(iii) The mucus helps to protect the stomach wall from being digested by its own secretion.



Q. 2. How does Nutrition take place in Amoeba. What is it called ?

Ans. Amoeba takes in the food particles with the help of its finger-like projections called Pseudopodia. A food vacuole is formed inside its cell around the food particle.


Complex substances are broken down into simpler ones inside the food vacuole which are then diffused into the cell cytoplasm. The remaining undigested material is sent to the surface of the cell and thrown out. This process of nutrition in Amoeba is known as phagocytosis.



Q. 3. Write a note on bile and its functions.

Ans. Bile is secreted by the liver and is stored in gall bladder. It helps in making the medium of food alkaline for the proper action of pancreatic enzymes. It also helps in the breakdown of large fat globules into smaller globules. This makes the action of enzymes easier.



Q. 4. Draw a diagram of human alimentary canal showing duodenum, small intestine, liver and pancreas.





Q. 5. (i) Draw diagram of a stomata when it is open.
(ii) Label Epidermal cell, Guard cell, Chloroplast and stomatal opening on the diagram drawn.





Q. 6. What are the different ways in which glucose is oxidised to provide energy in various organisms ?

Ans. Oxygen is essential for releasing energy from the food. Glucose is the nutrient of food which provides energy on decomposition. Glucose decomposes in three ways –
(a) Aerobic respiration. in which, glucose breaks up into pyruvate in presence of oxygen in cytoplasm.
(b) Anaerobic respiration. in which, breaking up of glucose takes place in mitochondria in the absence of oxygen in which ethanol and carbon dioxide are released as by-products alongwith the less amount of energy.
(c) In the muscle cells, the glucose, in presence of less amount of oxygen breaks into lactic acid, liberating energy.



Q. 7. What is the need of special tissues or organs for transport of substances in plants and animals ? Describe the transport of :
(i) minerals and (ii) food in plants.

Ans. Plants and animals possess complex body systems and thus they require oxygen, water and food to survive and maintain themselves. These substances are picked up or absorbed at one end of the body of an organism and transported to other parts. For this they need special tissues or organs for transport of substances.
Transport of minerals in plants. Water and minerals are taken in the form of solution, from roots tips to the leaves by xylem elements, i.e. tracheids and vessels.
Transport of food in plants. Food/sugars and other metabolites, are transported from leaf to other parts of the plant alongwith hormones through the living cells of the phloem which are called sieve tubes.



Q. 8. State the role of the following in the human respiratory system :
(i) Nasal cavity (ii) Diaphragm (iii) Alveoli.

Ans. (i) Nasal cavity. In the nasal cavity, the air is warmed, moistened and dust particles are entrapped in the mucous which is a secretion of glands inside the nasal cavity.
(ii) Diaphragm. Diaphragm separates thoracic cavity from the abdominal cavity. The lungs lie in the thoracic cavity and the diaphragm helps in the exhalation and inhalation process, flattening during inhalation and becoming more convex during exhalation.
(iii) Alveoli. Alveoli are the site of exchange of gases. They are the centre of the richly supplied with blood capillaries.



Q. 9. How does respiration take place in Amoeba ?

Ans. Amoeba is a single-celled animal which lives in water which has dissolved oxygen in it.



It takes in oxygen from the water through its cell membrane by the process of diffusion. In the same way, CO2 also goes out through its cell membrane.



Q. 10. (a) Define the terms ‘excretion’ and ‘osmoregulation’.
(b) Name the excretory unit of the following :
(i) Amoeba (ii) Earthworm.

Ans. (a) Excretion is the process which involves the removal of excess of nitrogenous waste such as urea from the body.
Osmoregulation is the process of maintaining the right amount of water and proper ionic balance in the body is termed as osmoregulation.
(b) Contractile vacuole and Nephridium.



Q. 11. Describe briefly the respiration process in a fish.

Ans. Fishes have special organs for breathing called gills. When water passes over the gills, they extract dissolved O2 from this water. The water is taken in by the fish through its mouth. As there is a rich supply of blood in the gills, the oxygen absorbed by the gills is carried by blood to all parts of the fish where cellular respiration occurs. As a result of cellular respiration, CO2 is produced which is carried by blood to the gills where it goes out into the surrounding water.



Q. 12. Describe aerobic respiration.

Ans. Respiration which occurs only in the presence of O2 is called aerobic respiration. During this type of respiration, glucose is broken down into CO2 and H2O, with the release of a large amount of energy. The energy is stored in the form of ATP.
Aerobic respiration consists of two steps –
(i) Glycolysis. It is the conversion of glucose into pyruvate or pyruvic acid. It occurs in the cytoplasm (i.e., outside the mitochondria).
(ii) Kreb’s cycle. It is the process of converting pyruvate into CO2 and H2O along with the release of considerable amount of energy. It occurs in the mitochondria. One molecule of glucose liberates 38 ATP of energy during aerobic respiration.

Pyruvic acid
(2 Molecules)
Pyruvic acid
(1 Molecule)
(Occurs in the cytoplasm)
(Pyruvate)(2 Molecules)



Q. 13. Draw V.S. of heart of man.

V.S. of heart of human heart




Q. 14. Name the three kinds of cells present in blood and their function.

Ans. The three kinds of blood cells are :
(i) Red blood corpuscles (RBCs), also called erythrocytes.
Function. RBCs contain haemoglobin which combines with oxygen to form oxyhaemoglobin, and transport oxygen to all parts of the body.
(ii) White blood corpuscles (WBCs), also called leucocytes.
Function. They provide defence by protecting the body from infections.
(ii) Blood platelets, also called thrombocytes.
Function. Blood platelets help in the coagulation of blood, which is also known as blood clotting.



Q. 15. Draw a labelled diagram of the detailed structure of a nephron.





Q. 16. Give the three main functions of kidney.

Ans. Kidney is the main excretory organ in man. Its three main functions are :
(1) It removes the poisonous substances such as urea, other waste salts and excess water from the blood and excretes them in the form of urine.
(2) It regulates the osmotic pressure or water balance of the blood.
(3) It regulates the pH of the blood.



Q. 17. Draw the labelled diagram of the structure of a leaf to show chloroplast.







Q. 1. How does the butter in your food get digested and absorbed in the body ? Explain in detail.

Ans. The digestion of butter, a form of fat, takes place in the following manner :
When butter comes in the duodenum, bile juice comes in contact with it and divides it into fine fatty globules. This process is called emulsification. Now this emulsified fat comes in contact with the lipase enzyme of pancreatic juice and converts it into fatty acids and glycerol.

Bile juice
Emulsified form of fat
lipase enzyme
Emulsified Fat
Fatty acids + Glycerol


The process of absorption takes place in Ileum of the small intestine. Fatty acids and glycerol are diffused in the inner membrane and lymphatic duct and reach here. They are carried to various parts of the body by lymph .



Q. 2. Describe the important functions of blood.

Ans. The important functions of the blood are :
(1) Blood carries inhaled oxygen from the air sacks of the lungs to the different parts of the body.
(2) It carries the by-products of oxidation, i.e., CO2 from the body cells to the air sacks of lungs for exhaling.
(3) It delivers digested food from small intestine to all the body cells.
(4) It protects the body from diseases. This is because the white blood cells kill the bacteria and other germs that cause diseases.
(5) Blood regulates the body temperature also. The capillaries situated in our skin help to keep the body temperature constant (at about 37ºC).
(6) Blood carries hormones from the endocrine glands to the wherever they are needed.
(7) Blood carries a waste product (urea) from the liver to the kidneys from where it is excreted out of the body in the form of urine.



Q. 3. Describe an activity to demonstrate that chlorophyll is necessary for photosynthesis.

Ans. Take a potted plant with variegated leaves, like those of money plant or croton. Keep this plant in a dark room for 3 days so that all its starch is used up. Now take this plant out in sunlight and keep it there for 4 hours. After that pluck a leaf from it and trace its green and yellow areas on a piece of paper. Take this leaf in a small beaker containing some alcohol in it. Heat this beaker on a waterbath till alcohol starts boiling and absorbs chlorophyll from the leaf so that alcohol becomes green in colour.
After this, now dip this leaf in a dilute solution of iodine for a few minutes. The colour of those parts of leaf will become blue-black which were green at the start. This shows the presence of formation of starch only in the green parts of the leaf which have chlorophyll in it. Starch turns the iodine solution to blue-black.
This activity clearly demonstrates that chlorophyll is necessary for photosynthesis.



Q. 4. Describe in detail the respiration process in human beings.

Ans. The respiratory system in man begins from nose cavities known as nostrils. The air from nasal cavity enters through pharynx into the trachea. The trachea runs down the neck and divides into two bronchi. Each bronchus is connected to a lung. In the lungs each bronchus divides into a large number of thin tubes called bronchioles. The bronchioles have tiny air sacs at their ends which are called alveoli, which are the site of exchange of gases.
Mechanism of Breathing. When we inhale air, the diaphragm contracts which results in the increase of chest cavity. Because of this expansion of chest cavity, the air pressure in the lungs decreases. In this way air from outside rushes into the lungs through nostrils, trachea and bronchi.
In this way, air sacs of lungs get filled with air when we breathe in. The exchange of gases between alveoli and blood takes place by the process of diffusion, and the air present in air sacs of the lungs is rich in CO2.



During exhalation, the diaphragm relaxes which results in the decrease of chest cavity. This contraction pushes the air from the lungs into the trachea, then nostrils and then out of the body into air.
The mechanism of gaseous exchange occurs during respiration. O2 is carried by blood to all the parts of the body. As the blood passes through the tissues of the body, the oxygen from the blood diffuses into the cell, whereas the CO2 which is produced during respiration diffuses into the blood and is carried back to the lungs, which is expelled out of the body.