Life Processes Class 10 Science Important Questions and Answers for Board Exam

Life Processes Class 10 Science Important Questions and Answers for Board Exam has been provided by JEE Wallah to help students score good marks in their CBSE and Competitive exams. Important Questions For Class 10 Science Chapter 5 Life Processes are given here as these questions are asked in the Board Exam. Students need to have a strong conceptual understanding of the chapter, only then could they be able to answer Extra Questions for Class 10 Science Chapter 5 Life Processes.

Life Processes Class 10 Science Important Questions and Answers Science Chapter 5

Students can solve Life Processes Class 10: Important Questions & Answers to know their preparation level. This post also contains many Previous Year Questions of Life Processes Class 10 that will help you check whether you have grasped the conceptual learning or not. Scroll below and start solving Life Processes Class 10 Important Questions with Answers.

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1 Mark Questions

Question 1. Which is the universal source of energy in all cells?
Answer : ATP, Adenosine Tri Phosphate.

Question 2. If no apparent work is being done by an organism, why does it takes food ?
Answer : To carry out life processes, growth, reproduction and for repair of worn out tissues.

Question 3. Which pathway is common to both aerobic and anaerobic respiration?
Answer : Glycolysis.

Question 4. What would be the consequences of deficiency of haemoglobin in our bodies ?
Answer : Anaemia

Question 5. How does nutrition in a fungus different from that in a tapeworm ?
Answer : Fungus derives its nutrition either by parasitic or saprophytic manner while tapeworm is only parasitic.

Question 6. What is the role of cartilaginous rings on trachea?
Answer : They prevent the collapsing of trachea when there is no air present in it.

Question 7. Mention two ways in which food gets oxidized in organisms.
Answer : Aerobic respiration and anaerobic respiration.

Question 8. Which enzyme is present in human saliva ?
Answer : Salivary amylase

Question 9. Why is respiration considered an exothermic process?
Answer : Respiration is considered an exothermic process due to breaking down of glucose/food in the presence of oxygen with release of energy.

Question 10. How does nutrition in a fungus different from that in a tapeworm?
Answer :Fungus derives its nutrition either by parasitic or saprophytic manner while tapeworm is only parasitic.

Question 11. What is peristalsis?
Answer : Contraction and expansion of alimentary canal to push the food forward is called peristalsis.

Question 12. What is the role of cartilaginous rings on trachea?
Answer :They prevent the collapsing of trachea when there is no air present in it.

Question 13. Why is respiration considered an exothermic process?
Answer :Respiration is considered an exothermic process due to breaking down of glucose/food in the presence of oxygen with release of energy.

Question 14. Why is energy required by an organism even during sleep?
Answer :This is because even when an organism is asleep, various biological processes keep on
occurring in its body which requires energy.

Question 15. Give the energy transformation that takes place in the process of photosynthesis.
Answer :Solar energy is converted into chemical energy during photosynthesis.

Question 16. Name the various factors which affect the rate of photosynthesis.
Answer : The factors which affect the rate of photosynthesis are light, water, temperature and carbon
dioxide.

Question 17.  Define photolysis.
Answer :The phenomenon of breaking down of water molecule using solar energy absorbed by
chlorophyll molecules is known as photolysis.

Question 18. Define light reaction.
Answer :A chemical reaction, which take place only in the presence of light, is called light reaction
or light dependent reaction. It takes place in grana of chloroplast.

Question 19. Define dark reaction.
Answer :A chemical reaction, which can take place even in the absence of light, is called a dark
reaction or light independent reaction. It takes place in stroma of chloroplast.

Question 20. Name the various cells through which water moves upward to reach the leaves.
Answer :water absorbed by root hairs moves through epidermis → root cortex → endodermis →
root xylem (ie., tracheids and vessels) → stem xylem → xylem in the leaf.

2 Marks Questions

Question 1. What will happen to a plant if its xylem is removed ?
Answer :The xylem tissue transports water and minerals from the soil to the leaves of a plant for
photosynthesis. If xylem is removed, upward movement of water will stop leading to wilting of
leaves and ultimately causes death of a plant.

Question 2.  In which chamber of heart is oxygenated and deoxygenated blood found?
Answer :Oxygenated blood: It is found in left auricle and left ventricle.Deoxygenated blood: It is found in right auricle and right ventricle

Question 3.  What is the main function of kidneys in humans?
Answer :Kidneys excrete water and dissolve metabolic wastes, e.g., urea and other dissolved solids
like uric acid, creatinine and inorganic salts.

Question 4. How are fats digested in our bodies? Where does this process take place?
Answer : Fats are first emulsified with the help of bile salts followed by their breakdown in fatty acids and glycerol due to the action of lipase. All these events take placein first part of small intestine duodenum.

Question 5. How do plants exchange gases?
Answer : Plants exchange gases through stomata. Large intercellular spaces ensure that each cell is in contact with air. Carbon dioxide and oxygen are exchanged here.

Question 6. List two factors which decide direction of diffusion of oxygen and carbon dioxide.
Answer : Environmental conditions and requirement of the plants decide direction of diffusion of oxygen and carbon dioxide.

Question 7. What are the strategies of plants to get rid of their wastes?
Answer : They throw away oxygen and water vapour through stomata. Some wastes like gums, oil and resins may be stored in old xylem or wood in stem. Some wastes may be stored in leaves and bark and
shed off from time to time. Roots can also throw some wastes.

Question 8. Why do we feel pain or cramps in muscles after a vigorous exercise?
Answer : Actively metabolizing cells of an extremely active skeletal muscle, during heavy exercise, carry oxidation in the anaerobic condition inside the muscle cell, we feel pain after a vigorous exercise because of production of ATP by anaerobic respiration in leg muscles.

Question 9. List two ways in which plants can get rid of the wastes.
Answer : They can throw gases and excess water through stomata through diffusion. They can store wastes like gums and resins in old xylem tissue (wood).

Question 10. What is the role of acid and mucus in stomach?
Answer : It kills germs in food and provides acidic medium for the action of pepsin enzyme to digest the proteins in stomach. Mucus protects the wall of stomach from the action of acid and pepsin.

Question 11. Identify the mode of nutrition where sunlight is used along with CO2 and water to prepare food.
Answer : In photosynthesis, sunlight is used along with water, CO2 and chlorophyll to prepare food. The mode of nutrition here is autotrophic. Example of autotrophic organisms is green plants that make their own food and do not depend on any organism for their nutrition.

Question 12. State the photosynthetic reaction and where does it occur?
Answer : The process of photosynthesis occurs in green parts of a plant, basically leaves. The presence of chlorophyll (green pigment) is necessary for photosynthesis to occur and chlorophyll is present in leaves as green dots.

Question 13. Which organelle acts as the site of photosynthesis ?
Answer : The chloroplast acts as the site of photosynthesis. It is a cell organelle that is covered by a double membrane and it contains chlorophyll. It is present in green tissues of plants, especially leaves. Chloroplasts absorb sunlight to conduct photosynthesis.

Question 14. Name the raw materials which are essential to carry out the process of photosynthesis in plants.
Answer : The raw materials needed to carry out photosynthesis are water (absorbed through roots), CO2(diffused in from the air through stomata). In addition to these, chlorophyll (green pigment present in chloroplasts) and sunlight are also required. Without these materials, photosynthesis cannot occur.

Question 15. How do parasitic organisms derive their nutrition?
Answer : Parasitic organisms like tapeworms, leeches, orchids, etc obtain nutrition from other living organisms (plants or animals) called as host, without killing them. Parasites may live on the outside or inside the body of its host. They cause harm to the body of the host.

Question 16. Why carnivores have shorter small intestine?
Answer : Carnivores have shorter small intestine, as compared to herbivores. Carnivores consume only flesh of other animals whereas herbivores consume plant products, which contain cellulose and fibre. Meat is relatively easier to digest and provide more energy. Cellulose and other plant products take longer to be digested. Hence, carnivores possess shorter small intestine.

Question 17. How do villi increase the surface area?
Answer : Villi are small finger-like projections present in the inner lining of the small intestine. They increase the surface area of small intestine by providing more area for efficient absorption of nutrients. The presence of villi and micro-villi gives a brush border appearance. Villi also possess blood vessels and lacteals (lymphatic vessels).

Question 18. Where is bile juice produced?
Answer : Bile juice (dark green-yellow pigment) is produced by the liver. It helps in the digestion of lipids (fats) in small intestine. It emulsifies (breaks down) larger fat globules into smaller ones so that enzymes can act efficiently on fat globules.

Question 19. What happens to extra glucose or carbohydrate in an animal body?
Answer : In an animal body, extra glucose or carbohydrate is stored in the liver as well as in skeletal muscles in the form of glycogen. Glucose is converted to glycogen (starch-like carbohydrate) in liver. When the body is in need of energy, glycogen is converted back into glucose.

Question 20. Name an energy rich carbohydrate stored in large quantities in liver and muscle cells.
Answer : Glycogen is an energy rich carbohydrate that is stored in large quantities in the liver and skeletal muscles of the body. It is a branched-chain polymer of glucose. It serves as a reserve source of energy.

Question 21. How does most CO2, reach the photosynthesising cells of a green leaf?
Answer : Most CO2 reach the photosynthesising cells of green leaves through diffusion. Stomata (tiny pores) present of leaf surface and stem facilitates gaseous exchange between the plant cells and the surrounding. CO2 move into the cells through these small pores.

Question 22. Stomata of desert plants remain closed during the day. Explain how and when they take up CO2 to perform photosynthesis?
Answer : Desert plants close their stomata during the day to prevent transpiration and loss of water. To perform photosynthesis, CO2 is necessary. They take up CO2 during the night through stomata and store it in their photosynthesising cells in the form of an intermediate until the day. And when sunlight is available, they perform photosynthesis to make their food.

3 Marks Questions

Question 1. Give the steps involved in photosynthesis.
Answer : The process of photosynthesis involves a few events that may not occur immediately after one another. There might be a time lag between them.

•The chlorophyll present in chloroplasts absorbs energy from sunlight.
•This light energy is then converted into chemical energy which is used for making food.
•The water molecules split to give hydrogen and oxygen.
•Finally, CO2 absorbed is reduced to form glucose (carbohydrate).

Question 2. What do we learn concerning the increased cutting of trees and removal of the green cover?
Answer : Removal of green cover (deforestation) leads to serious problems. It has a negative
impact on our environment and our lives. As we are directly dependent on plants and
trees for our food, our survival will be at risk. Deforestation leads to climatic changes. It
is a major cause for global warming. Moreover, animals are also badly affected. Their
habitats are destroyed.

Question 3. Why cannot we digest raw green plants in our alimentary canal?
Answer : Raw green plants contain fibre and cellulose. Our digestive system does not secrete any enzyme capable of digesting cellulose. Cellulose is digested by enzyme cellulose present in ruminating animals like cow. Also, our oesophagus serves only as a pathway to transport food from mouth to stomach. It does not possess any digestive gland. Hence, no secretion of enzymes occurs.

Question 4. Why are digestive enzymes present in an inactive form in the body when we can require their action any time?
Answer : Although we may require enzyme action any time, they must be produced in an inactive form. Enzymes are capable of digesting a variety of bio molecules (proteins, fats, etc). If produced in active form, they may act upon the body cells and tissues and digest them leading to degeneration of body tissues.

Question 5. Where does aerobic respiration occur? How many molecules of ATP are released during it?
Answer : Respiration on the basis of presence or absence of oxygen can be of two types: aerobic respiration and anaerobic respiration. Aerobic respiration occurs in the presence of oxygen while anaerobic occurs in the absence of oxygen. Site of aerobic respiration is mitochondria. During aerobic respiration 38 ATPs get released in complete oxidation of one glucose molecule.

Question 6. -The end product of a process is ethanol and carbon dioxide with the release of energy. Name this process and write the pathway involved in the reaction
Answer : -During aerobic respiration, the product is CO2 & H2O. While during anaerobic
respiration, the product can be either lactic acid or ethanol+CO2 on the basis of enzyme
involved. If the product is ethanol &CO2, the process is termed as Fermentation. Initially glucose gets converted into pyruvic acid (by the process of glycolysis-common in both aerobic & anaerobic respiration). In fermentation, this pyruvic acid produces ethanol & carbon-dioxide in the presence of enzyme alcohol dehydrogenase. The fermentation process is also used for industrial production of alcohol.

Question 7. -Where does anaerobic respiration occur in human body?
Answer : -Usually human body performs only aerobic respiration. But in certain conditions (like heavy exercises), when body needs enormous amount of energy but oxygen supply is not enough, our body gets bounded to perform anaerobic respiration. It occurs in our muscle cells where due to anaerobic respiration, lactic acid gets produced. You might have experienced pain in arms or legs after doing some heavy physical exercise or work. It is because of accumulation of lactic acid in muscle cells.

Question 8. -What is the difference between external and internal respiration.
Answer : -External respiration is an alternate term used for breathing. It includes inhalation of O2 & exhalation of CO2. While internal respiration occurs inside the body between blood and tissues where there is transfer of oxygen from blood to each and every tissue of body to fulfil its demand.

Question 9. -List the factors on which diffusion in the plants depends.
Answer : -Diffusion is a phenomenon explaining movement of substances from its higher concentration to its lower concentration. In plants, diffusion of gases occurs. Factors affecting diffusion are:-
(i) Concentration gradient:- More steeper the concentration gradient, greater will be
the diffusion.
(ii) Temperature:- Diffusion rate increase with increase in the temperature because
speed of ions increases.
(iii) Size of molecules:- Molecules with smaller size can diffuse easily as compared to
molecules with larger size.

Question 10. -What are lenticels?
Answer : -Lenticels are pores present on the woody bark of a tree stem. Usually a stem is covered with a tough layer of suberin. The places where suberin is absent, some pores are develop. These pores are called as Lenticels. They help in the exchange of gases.

Question 11. -What is the role of valves in veins?
Answer : -They prevent the back flow of blood especially when it moves against gravity and under low blood pressure.

Question 12. -What would be the consequences of deficiency of hemoglobin in your body?
Answer : -The deficiency of hemoglobin in our body is called anemia. In anemia, the blood is unable to carry the sufficient amount of oxygen required by the body. So, respiration would be less and less energy will be available to the body. The hemoglobin deficient person will feel weak, pale, lethargic and will be unable to perform heavy physical work.

Question 13. -Respiratory surface of animals must always be moist. Why?
Answer : -The respiratory surface of animals must always be moist for better diffusion of gases. Both oxygen and carbon-dioxide gets dissolved in water quickly and their diffusion becomes easier & quicker. This is the reason for moist respiratory surfaces.

Question 14. -How is the small intestine designed to absorb digested food?
Answer : -Walls of small intestine has finger like projection called villi to increase surface area. The food is absorbed by villi and brought into blood. Fat is brought into lymph vessel.

Question 15. -Why does the rate of breathing in aquatic animals is faster than others?
Answer : - In aquatic animals, the respiration process involves the usage of oxygen dissolved in water. As the amount of oxygen dissolved in water is much less than the amount of oxygen available on land, aquatic animals have higher breathing rate.

Question 16. -List three characteristics of lungs which make it an efficient respiratory surface.
Answer : Three characteristics of lungs which make it an efficient respiratory surface are :

1. Thin: The air sac walls are very thin so that gases can quickly diffuse through them. Oxygen
   is absorbed in to the blood and carbon dioxide is given out in to the lungs to be exhaled out.
2. Moist: The air sacs are moist with mucus so that gases can dissolve before diffusing.
3. Good blood supply: The air sacs or the alveoli have a large capillary network so that large
   volumes of gases can be exchanged. More the flow of blood more exchange.
   

Question 17. -What is the essential feature of respiratory organ of different terrestrial animals?
Answer : -The essential feature of respiratory organs of terrestrial animals is that they must be protected under layers of tissue so as to avoid any shock or damage. They must also be supplied with a large number of blood vessels for easy and fast exchange of gases.

Question 18. -Why are arteries thick walled and elastic?
Answer : -Arteries receive the blood pumped by heart with lots of pressure hence to tolerate and sustain this pressure they are thick walled and elastic.

Question 19. - Why do the walls of the trachea not collapse when there is less air in it?
Answer : -Rings of cartilages are present in trachea. These rings support the trachea and do not allow the trachea to collapse when there is less air in it.

Question 20. - Discuss how the roles of vena cava and pulmonary veins different from each other?
Answer : -Pulmonary vein carries oxygenated blood from lungs to left auricle of heart in humans. On the other hand Vena Cava collects deoxygenated blood from all parts of the body and transport it to right auricle of the heart in human.

Question 21. -State two functions of stomata.
Answer : Exchange of gases between the plant and the atmosphere and Transpiration in plants takes place through stomata.

Question 22. -What is saliva? State its role in the digestion of food.
Answer : -Saliva is a watery fluid secreted by the salivary glands in the mouth. The digestive functions of saliva include moistening food, and helping to create a food bolus, so it can be swallowed easily. Saliva contains the enzyme amylase that breaks some starches down into maltose.

Question 23. --Why is it advisable to breathe through nose?
Answer : --There are fine hair and mucus gland in the inner lining of nose which filter the incoming air of germs and dust. Moreover the air attains the optimum temperature before reaching the lungs.

Question 24. --Define transpiration. How does transpiration help in upward movement of water from roots to leaves?
Answer : --Transpiration is the process of removal of water vapours from the aerial parts of a plant, mainly through stomata in the leaves. Evaporation of water molecules from the cells of a leaf creates a suction force which pulls water from the xylem cells. This transpiration helps in upward movement of water from roots to leaves.

Question 25. --Describe the structure of the human heart briefly.
Answer : --Human heart is four chambered. The two upper chambers are called atria and they receive blood from large veins while the two lower chambers are called ventricles. Between left atrium and left ventricle as well as between right atrium and right ventricle are valve which allow blood to flow only from atrium to ventricle.

Question 26. --Name the respiratory pigment in human beings? What is its role?
Answer : --Respiratory pigment, haemoglobin is present in red blood cells. Haemoglobin has affinity for O2 thus helping in its transport.

Question 27. --What are enzyme? Do they play some role in our digestive system too?
Answer : --They are chemically proteinaceous biocatalyst, which increase or decrease the rate of a biochemical reaction. The enzyme present in our digestive system help to breakdown of complex molecules of food into simpler ones.

Question 28. --What is the role of large intestine?
Answer : --Water re-absorption occurs through villi, undigested food is stored in rectum and thrown out through anus. Exit is regulated by anal sphincter.

Question 29. --Why are ventricles thick walled and muscular?
Answer : --Since ventricles have to pump blood into various organs, they are thick-walled and muscular.

Question 30. --How is the length of intestine related to food habit of the animal?
Answer : --Intestine where digestion and absorption occur is very long in herbivores and shorter in carnivores as digesting meat is easier than digesting grass.

Question 31. -Differentiate between Photosynthesis and Respiration.
Answer : --Difference between Photosynthesis and Respiration are :

• Respiration: It occurs in all living cells. O2 reacts with food and energy is released. It occurs in cytoplasm and mitochondria.  
• Photosynthesis: It occurs in only autotrophs. CO2 and H2 O combine to form starch and water in the presence of light. It occur in plastid- chloroplast.

Question 32. --What is residual volume in our lungs? What is its importance.
Answer : --Residual volume is the amount of air which is always left inside the lungs in spite of forceful exhalation. It helps in continuous gas exchange during exhalation or inhalation.

Question 33. --In which organisms the cell membrane acts as the respiratory surface?
Answer : --The organism in which the cell membrane acts as a respiratory surface is Amoeba. In amoeba, the unicellular animal, the exchange of gases takes place through the cell membrane or the plasma membrane. The cell membrane of amoeba absorbs oxygen from the surrounding area and release carbon dioxide by the process of diffusion.

Question 34. --How are the alveoli designed to maximise the exchange of gases?
Answer : --Alveoli are small pouches or sacs like structure. They are surrounded by blood capillaries. Thus a large amount of air is brought in contact with the air in the lungs. More than millions of alveoli are present in the lungs. The presence of millions of alveoli in the lungs provides a very large surface area for the exchange of gases. The availability of large surface area maximises the exchange of gases.

Question 35. --Why do we need a respiratory pigment to perform respiration?
Answer : --Respiratory pigments play a very important role in the body of an organism. It helps in the transportation of respiratory gases to the various body organs. Respiratory pigment present in humans is haemoglobin. It is a red color pigment present in our blood. It helps in transporting oxygen from lungs to various body tissues and also helps in the removal of carbon-dioxide from cells.

Question 36. --What is common between respiration and transpiration process in plants?
Answer : --Both in respiration and transpiration stomata are active. The only difference is that in respiration stomata helps in exchange of gases, while in transpiration, it helps in evaporation of water.

Question 37. --Why rate of breathing in aquatic animals has to be faster than that in terrestrial animals?[
Answer : --Amount of O2 dissolved in water is less than O2 present in air therefore rate of breathing in aquatic animals has to be faster than that in terrestrial animals. Terrestrial organism need not spend so much energy to obtain oxygen.

Question 38. --How do autotrophs obtain CO 2 and N 2 to make their food?
Answer : --CO2 from environment/atmosphere through diffusion/ stomata. Nitrogen from soil/environment in inorganic (nitrates) or organic form.

Question 39. --How is oxygen and carbon dioxide exchanged between blood and tissue? How are the gases
transported in human being.
Answer : --Exchange of gases in tissues occurs through diffusion. Oxygen is carried as oxyhaemoglobin
from lungs to tissues. It dissociates and carbon dioxide diffuses out into blood from tissues. It is
transported in dissolved form and reaches lungs where again it diffuses to alveoli.

Question 40. --What are the important features of all respiratory structures in animals?
Answer : --All respiratory system have some important features.

• Large surface area.
• Thin and delicate surface for diffusion and exchange of gases. It is generally located in protected inner part of body.
• Rich blood supply to respiratory organ. Since all of them are present in alveoli hence it is perfectly
  designed for exchange of gases.

4 Mark Questions

Question 1. --What is excretion? Name some parts in our body involved in this life process?
Answer : --Excretion means throwing out metabolic waste from living body. Many organs perform this process such as :

• Kidneys remove nitrogenous wastes like urea and uric acid in urine.
• Sweat and oil by glands in skin.
• Carbon dioxide and water vapor by lungs.
• Faces or undigested food by large intestine.
• Bile pigments by liver. It also converts toxic ammonia to urea.
  

Question 2. --What is the need to have a transport system in complex organisms?
Answer : --The transport system of an animal moves substances to where they are needed in the body. Even the smallest animal must have the means of transporting substances around its body. Oxygen and food molecules must move to all the cells, and the waste products must be removed from the cells and expelled into the environment. It occurs through diffusion mainly. In a multicellular organism, all cells are not in contact with the surrounding hence diffusion will be insufficient for it. A variety of fluid systems, called vascular systems, help such transport in most members of the animal kingdom.

Question 3. --How is food transported in a plant?
Answer : --The food prepared by plant may be sucrose, amino acids or other materials. It is done with the help of living cells- sieve tubes and companion cell of phloem tissue by utilizing energy of ATP. The movement occurs both upwards and down ward from the place of formation (leaves) to storage organ (roots or stems) from storage organ to organ of its utilization (growing buds) depending upon the situation.

• Transport of organic food from the leaves to the other parts of the plants through the
  sieve tubes of phloem tissue is called translocation.
• It is an essential process as every part of the plant requires food. For energy, building
  and maintenance.
• Sugars are synthesized in the leaves whereas hormones are synthesized in the growing parts of
  roots and shoots.
  

Question 4. --Explain how the air is inhaled during breathing in humans.
Answer : --Mechanism of inhalation is :

• The diaphragm and rib muscles contract which make the throat move upwards and outwards.
• The volume inside the thoracic cavity increases i.e., it expands.
• Air pressure inside the thoracic cavity decreases. Thus, air from outside rushes into the lungs / alveoli through nostrils, trachea and bronchi.
  

Question 5. --What are the main events occurring in the small intestine?
Answer : --The main events occurring in the small intestine are :

• Bile emulsifies fat present in the food (emulsification means breaking of fat molecules
  into smaller globules).
• Pancreatic juice containing trypsin for digesting proteins and pancreatic amylase for starch act
  upon the food.
• Bicarbonate ions secreted by duodenal wall make the medium alkaline because it is required for the
  action of pancreatic enzynies.
• Enzymes produced in intestinal juice complete the digestive process.
• Digested food - amino acids, sugar are absorbed by the blood capillaries present in the villi of intestine.
• Digested fats are absorbed by lymph vessels present in the villi of intestine.

Question 6. --Which process in plants is responsible for clouds formation and precipitation? Define the process. How is this process important for the plants?
Answer : --They are due to transpiration. Transpiration is evaporation of water from aerial parts, leaves of plant, through mainly stomata.

• In plants, water rises because of transpiration and in nature water cycle operates because of it.
• Transpiration is the process of cooling the parts of a plant.
•  Evaporation of water molecules from the cells of a leaf creates a suction force which pulls water
  from the xylem cells. This transpiration helps in upward movement of water from roots to leaves.
  

Question 7. --Leaves of a healthy potted plant were coated with Vaseline to block the stomata. Will this plant remain healthy for long? Stage three reasons for your answer.
Answer : --No, the plant will not stay healthy for a long time. The reasons are:

• It will not be able to exchange O2 and CO2, hence respiration will be affected adversely.
• Photosynthesis will also be affected as CO 2 will not be available.
• Transpiration will not take place hence there will be no ascent of sap, hence no water absorption
  from the soil.
  

Question 8. --How is oxygen and carbon dioxide transported in human being? Explain clearly how the air is inhaled and exhaled during breathing in humans.
Answer : -- oxygen and carbon dioxide transported in human being by :

• Most of oxygen is carried by haemoglobin in blood. On reaching the tissues, it gets diffused into the cells as it is in higher concentration than in the cells.
• The carbon dioxide, which is formed in the cells, gets accumulated there in higher concentration as compared in the blood, now diffused into the blood.
• The CO2 mostly dissolved in blood plasma reaches the lungs, from where it is expelled out during exhalation.
  

Mechanism of Inhalation: The thoracic cavity expands when diaphragm and rib muscles contract. The thorax moves upwards and outwards, increasing the volume inside thoracic cavity. The air pressure in the cavity decreases, hence the air rushes into the lungs through nostrils, trachea and bronchi.

Mechanism of Exhalation: Exchange of gases between alveolar sacs and blood occurs and air having CO2 enters the alveoli. The thoracic cavity comes back to its original size as diaphragm muscles relax. Air containing CO2 is exhaled out through bronchi, trachea and nostrils.

Question 9. --Describe double circulation in human beings. Name the group of animal with double circulation? How is it important for them?
Answer : --Such a flow in which blood enters the heart twice is called double circulation. It helps in keeping the oxygenated and deoxygenated blood separate. The right atrium receives blood from the vena
cava and pumps the blood into the right ventricle. Blood is sent to lungs, where it is oxygenated. Then,
it is sent through the right and left pulmonary veins to the left atrium where it is pumped to the left ventricle. The blood then travels to the ascending aorta where it leaves the heart and delivers oxygen to different parts of the body.

Question 10. --What are the main components of blood?
Answer : --Blood is a very important connective tissue and has two main components which are:

• Plasma is the fluid part which is about 55% of the total blood. It is a straw colored
  liquid, viscous in nature. Plasma comprises of about 90-92% of water and 6-8%
  proteins.
• Blood cells/ corpuscles all the formed elements constitutes about
  45% of the total blood. It include the red blood cells (erythrocytes), white blood cells
  (leucocytes) and the platelets (thrombocytes). Out of these platelets are not the proper
  cells but the cell fragments which play a major role in the process of blood clotting.
  

Question 11. --How does excess of water removed by the plants?
Answer : --Plants lose excess water through stomata, lenticels and cuticle. The two processes involved are transpiration and guttation. When water is lost in the form of vapours through the stomata present on the aerial parts of plants, it is called transpiration. It occurs by pulling of water. It occurs only in daytime. When excess water is lost in the form of liquid droplets from the margins of leaves, through hydathodes, it is called guttation. It occurs by pushing of water towards leaf margins. It occurs only at night. Hydathodes are structurally modified pores present on leaf margin.

Question 12. --Outline the functioning of kidney dialysis machine?
Answer :

• The dialysis machine serves as artificial kidney.
• It is used for patients with damaged or dysfunctional kidneys.
• It filters blood and removes waste products and excess fluid from the body.
• It works on the principle of diffusion.
• It consists of semi-permeable tubes (made of cellophane) and a special dialyzing
  fluid.
• A small incision is made on the arm and a tube is connected. The blood is passed
  along the tubes placed in dialyzing fluid that filter waste products from the blood through
  diffusion.
• The filtered blood is transported back into the body.
  

Question 13. -How are oxygen and carbon dioxide transported in human beings? How are lungs designed to maximise the area for exchange of gases?
Answer : --Exchange of gases in tissues occurs through diffusion. Oxygen is carried as oxyhaemoglobin from lungs to tissues. It dissociates and carbon dioxide diffuses out into blood from tissues. It is transported in dissolved form and reaches lungs where again it diffuses to alveoli. Lungs have a tree like branching pattern of bronchi and bronchioles. The terminal part of bronchiole ends into sac like structures called alveoli which are present in groups. Alveoli have curved wall to increase surface area for exchange of gases. The wall of alveoli is extremely thin and is lined by blood capillaries.

Question 14. -State the functions of Lungs.
Answer : --

• It cleans the cellular environment.
• It returns proteins and tissue fluids to the blood (drainage).
• It provides a pathway for the absorption of fats and fat-soluble vitamins into the
  bloodstream.
• It defends the body against disease.
  

Question 15. -Describe an experiment to show that “sunlight is essential for photosynthesis.”
Answer : -Procedure is given below :

• Place a healthy green potted plant in a dark room for 1-2 days. This is done to ensure
  that the plant consumes all its reserve food and the leaves do not contain any starch.
• Then, cover a portion of a leaf of this plant on both sides with two uniform pieces of black
  paper, fixed in position with two paper clips.
• Now, expose this plant to bright light. After a few hours, remove the leaf and decolorize it
  with alcohol and test the presence of food (starch) with iodine solution.

Observation : It can be observed that the portion of the leaf covered with black paper does not undergo photosynthesis. This is because the food prepared by plants through the process of photosynthesis is stored as starch. Starch reacts with the iodine solution to give blue-black colour. Only those portions of the leaf that were exposed to sunlight could photosynthesise. Hence, gives blue- black colour when tested with iodine. The portion of the leaf covered with black paper did not receive sunlight. Hence, starch was not produced. Thus, it can be concluded that the sunlight is essential for photosynthesis.

Question 16. --Explain the importance of Salivary Amalyse, villi and pepsin.
Answer : --

• Salivary amylase: It’s an enzyme present in the saliva, secreted by salivary glands. It digests starch into maltose there by starting the digestion of carbohydrate in the buccal cavity.
• Villi: They increase the surface area for absorption of digested food into the blood.
• Pepsin: It is a digestive enzyme secreted by gastric glands. It is responsible for the digestion of proteins in stomach.
  

Question 17. --Usman collected her saliva and mixed it with liquid A in the test tube. In another test tube she took only liquid A after about 10 minutes, she added a few drops of iodine solution to the mixture in the first test tube. It did not show any colour but when she treated the other test tube with iodine, a blue black colour appeared. Now answer the following questions: 

Question 18. --What are the different components of blood? Give the function of each of them.
Answer : --Blood is a liquid connective tissue. It is chiefly formed of two components:

• Plasma: It is of pale colour and transports much substance like dissolved carbon dioxide, glucose, amino acids, urea etc. has mainly water, some proteins like albumin, fibrinogen (blood clotting protein) and many other substances to be transported.
• Red blood corpuscles (R.B.C) or erythrocytes, which transports oxygen and carbon dioxide. They are enucleated, disc shaped, full of a red colored protein pigment, hemoglobin.
• White blood corpuscles (W.B.C) or leucocytes, which fight disease-causing agent. They are larger, nucleated and are of different types.
• Blood platelets or thrombocytes, which help in blood clotting. They are fragments of some larger cell hence do not have nucleus.
  

Question 19. --How are water and minerals absorbed and transported in the plants?
Answer : --

• Transpiration is the process of removal of water vapors from the aerial parts of a plant, mainly
  through stomata in the leaves.
• There are two conducting tissues of plants: first is xylem and second is phloem. Tracheids and
  vessels which are two kinds of elements of xylem.
• Tracheids are found in all vascular plants. They are spindle shaped, have only pits and are not
  very efficient.
• Vessels are found in flowering plants, are tube like, have perforation plates and pits making them
  more efficient.
• When loss of water in vapour occur from leaves of plants due to transpiration, deficit of water
  is created in the leaves. Evaporation of water molecules from the cells of a leaf creates a suction
  force which pulls water from the xylem cells.
• Water and minerals dissolved in it move up to leaves from root through tracheids and vessels pulling water and minerals upward through xylem elements-ascent of sap. Thus transpiration helps
  in upward movement of water from roots to leaves.
  
• The roots of a plant absorb water and dissolved substances from the soil, which is needed by the
  aerial parts of the plants. As such these substances are to be transported from roots up to stem,
  leaves and flowers.
  

Question 20. --Describe double circulation in human beings. Name the group of animal with double circulation? How is it important for them?
Answer :

Such a flow in which blood enters the heart twice is called double circulation. It helps in keeping the oxygenated and deoxygenated blood separate. The right atrium receives blood from the vena
cava and pumps the blood into the right ventricle. Blood is sent to lungs, where it is oxygenated. Then,
it is sent through the right and left pulmonary veins to the left atrium where it is pumped to the left ventricle. The blood then travels to the ascending aorta where it leaves the heart and delivers oxygen to different parts of the body.

Question 21. --Explain the different components of blood? Mention the functions of each of them.
Answer : --Blood is a liquid connective tissue. It is mainly formed of two components :

1. Red blood corpuscles (R.B.C) or erythrocyt. es, which transport O2 and CO2 . They are
   enucleated, disc shaped, full of a red colored protein pigment, hemoglobin.
2. White blood corpuscles (W.B.C) or leucocytes, which fight disease-causing agent. They are
   larger, nucleated and are of different types.
3. Blood platelets or thrombocytes, which help in blood clotting. They are fragments of some
   larger cell hence do not have nucleus.
4. Fluid matrix or plasma: It is of pale colour and transports much substance like dissolved
   carbon dioxide, glucose, amino acids, urea etc. has mainly water, some proteins like albumin,
   fibrinogen (blood clotting protein) and many other substances to be transported.

The liquid is now called urine is concentrated and collected in collecting duct and poured in ureters tobe carried to urinary bladder. Urine is passed out through urethra, when the urinary bladder is full and due to pressure there is an urge to do so. Sphincter muscles regulate this process Osmoregulation and excretion are intimately related, these processes together maintain homeostasis (i.e. staying the same), and are performed by the same set of organs. The kidney is the major organ of osmoregulation and excretion in vertebrates.

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