Chapter 5: Life Processes

Multiple Choose Question and Answer:

Question: The kidneys in human beings are a part of the system for

(a) nutrition.

(b) respiration.

(c) excretion.

(d) transportation.

Answer:  (c) excretion .

[ Kidneys filter blood to remove wastes like urea, excess salts, and water, forming urine, which is part of the excretory system.]

Question: The xylem in plants are responsible for

(a) transport of water.

(b) transport of food.

(c) transport of amino acids.

(d) transport of oxygen.

Answer: (a) transport of water .

[ Xylem carries water and minerals from the roots to the leaves, while phloem transports food. ]

Question: The autotrophic mode of nutrition requires

(a) carbon dioxide and water.

(b) chlorophyll.

(c) sunlight.

(d) all of the above.

Answer:  (d) all of the above

[ Autotrophic nutrition, like photosynthesis, needs carbon dioxide, water, sunlight, and chlorophyll to make food. All three are essential for the process.]

Question: The breakdown of pyruvate to give carbon dioxide, water and energy takes place in

(a) cytoplasm.

(b) mitochondria.

(c) chloroplast.

(d) nucleus.

Answer:  (b) mitochondria

[ After glycolysis in the cytoplasm, pyruvate enters the mitochondria, where it is fully broken down during the Krebs cycle and electron transport chain to produce carbon dioxide, water, and energy (ATP).]

Question: In living organisms during respiration which of the following products are not formed if oxygen is not available ?  [2021 1M]

(a) Carbon dioxide + water     (b) Carbon dioxide + Alcohol     (c) Lactic acid +Alcohol      (d) Carbon dioxide + Lactic Acid

Answer: (a) Carbon dioxide + water.

 [ Aerobic respiration (when oxygen is available): Glucose → Carbon dioxide + Water + Energy (This is the complete oxidation process in mitochondria.)

Anaerobic respiration (when oxygen is not available):

In yeast/plants (alcoholic fermentation): Glucose → Carbon dioxide + Alcohol (Ethanol)

In animal muscles: Glucose → Lactic acid

Water is not produced in anaerobic conditions.

Therefore, Carbon dioxide + Water are not formed together when oxygen is unavailable. ]

Question: The correct statements with reference to single celled organisms are : [2021 1M]

(i) Complex substances are not broken down into simpler substances .

(ii) Simple diffusion is sufficient to meet the requirement of exchange of gases .

(iii) Specialised tissues perform different functions in the organism .

(iv) Entire surface of the organism is in contact with the environment for taking in food .

(a) (i) and (iii)   (b) (ii) and (iii)  (c) (ii) and (iv)  (d) (i) and (iv)   

Answer: (c) (ii) and (iv)  

[ (i) Complex substances are not broken down into simpler substances
 Incorrect — even single-celled organisms digest food, so complex substances are broken down.

(ii) Simple diffusion is sufficient for exchange of gases
Correct — since they are very small, diffusion is enough for oxygen and carbon dioxide exchange.

(iii) Specialised tissues perform different functions
Incorrect — they don’t have tissues at all (only one cell!).

(iv) Entire surface is in contact with the environment for taking in food
Correct — the whole cell surface helps in exchange and intake. ]

Question:  Which one among the following is not removed  as a waste product from the body of a plant ? [2021 1M]

(a) Resins  and Gums   (b) Urea   (c) Dry leaves   (d) Excess water

Answer:  (b) Urea

[ Plants remove wastes in different ways:

Resins and gums → stored or secreted as waste

Dry leaves → wastes get stored and removed when leaves fall

Excess water → removed through transpiration

But urea is a nitrogenous waste found in animals, not in plants. ]

Question: A student was asked to write a stepwise procedure to demonstrate that carbon dioxide is necessary for photosynthesis . He wrote the following steps . The wrongly worded step is ; [2021 1M]

(a) Both potted plants are kept in dark room for at least three days . 

(b) Bottom of the bell jars is sealed to make them air tight .

(c) Both potted plants are kept in sunlight  after the starch test .

(d) A leaf from both the plants is taken to test the presence of starch .

Answer: (c) Both potted plants are kept in sunlight after the starch test

[ This step is wrongly written because in the correct procedure, plants must be kept in sunlight before the starch test, not after. ]

Question: The length of small intestine in a deer is more as compared to the length of small intestine of a tiger . The reason for this is [2021 1M]

(a) Mode for intake of food .

(b) Type of food consumed

(c) Presence or absence of villi in intestines .

(d) Presence or absence of digestive enzymes .

Answer: (b) Type of food consumed

[ A deer is a herbivore (plant eater). Plant food like cellulose is hard to digest, so it needs a longer small intestine for proper digestion and absorption.

A tiger is a carnivore (meat eater). Meat is easier to digest, so its small intestine is shorter.

So, the difference is because of the type of food they consume. ]

Question: The haemodialyzer has semi-permeable lining of tubes which help  [2021 1M]

(a) To maintain osmotic pressure of blood

(b) To filter nitrogenous waste from the dialyzing solution .

(c) In passing the waste products in the dialyzing solution .

(d) To pump purified blood back into the body of the patient .

Answer: (c) In passing the waste products in the dialyzing solution.

The semi-permeable membrane of the hemodialyzer allows waste products from the patient's blood to pass through into the dialyzing solution while retaining essential components like blood cells and proteins.

Question: Which one of the following is not a function of Artificial Kidney ?

(a) To remove nitrogenous wastes from the blood .

(b) To remove excess fluids from the blood .

(c)  To remove reabsorb essential nutrients from the blood .

(d) To filter and purify the blood .

Answer: (c) To remove reabsorb essential nutrients from the blood.

[ Artificial kidneys are designed to filter and purify the blood by removing nitrogenous wastes and excess fluids, mimicking the function of natural kidneys. They do not selectively reabsorb essential nutrients like natural kidneys do. ]

Question: The ‘used dialysis’ solution is rich in :

(a) Urea and excess salts

(b) Blood cells

(c) Lymph 

(d) Proteins

Answer: (a) Urea and excess salts.

[ During dialysis, the solution used to cleanse the blood accumulates waste products like urea and excess salts that have been removed from the patient's bloodstream. ]

Question: Which part of the nephron inhuman kidney, serves the function of reabsorbtion of certain substances ?

(a) Glomerulus   (b) Bowman’s  capsule  (c) Tubules   (d) Collecting 

Answer: (c) Tubules

[ The renal tubules, including the proximal convoluted tubule, loop of Henle, and distal convoluted tubule, are responsible for reabsorbing essential substances (such as water, glucose, and ions) from the filtrate back into the bloodstream. ]

Question: An organism which breaks down the food material outside the body and then absorbs it is: [2023]

(a) a plant parasite , cuscuta       (b) an animal parasite, tapeworm

(c) a bacteria, Rhizobium             (d) a fungi, Rhizopus

Answer: (d) a fungi, Rhizopus.

[ Fungi like Rhizopus secrete digestive enzymes to break down food externally and then absorb the nutrients, a process known as extracellular digestion.]

Question: Consider the following statements about ,small intestine and select the which is not correct: [2023]

(a) The length of the small intestine in animals differs as it depends on the type of food they eat.

(b) The small intestine is the site of complete digestion of food.

(c) The small intestine receives secretions from liver and pancreas.

(d) The villi of the small intestine absorb water from the unabsorded food before it gets removed from the body via the anus.  

Answer: (d) The villi of the small intestine absorb water from the unabsorbed food before it gets removed from the body via the anus.

[ Water absorption primarily occurs in the large intestine, not the small intestine. The villi in the small intestine mainly absorb nutrients, not water.]

Assertion (A) and Reason (R) Question and Answer :

Question: Assertion (A) : Nitrogen is an essential element for plant growth and is taken up by plants in the form of inorganic nitrates or nitrites .

Reason (R) : The soil is the neatest and richest source of raw materials like Nitrogen, Phosphorus and other minerals for the plants . [2021]

(a) Both (A) and (R) are true and (R) is the correct explanation of (A) .

(b) Both (A) and (R) are true but (R) is not the correct explanation of (A) .

(c) (A) is true , but (R) is false .

(d) (A) is false , but (R) is true .

Answer: (b) Both (A) and (R) are true but (R) is not the correct explanation of (A)

[ Assertion (A): Nitrogen is essential for plant growth and is absorbed as nitrates or nitrites.
This is true — plants cannot take nitrogen directly from air, so they absorb it from soil in these forms.

Reason (R): Soil is the main source of raw materials like nitrogen, phosphorus, and minerals. This is also true.]

Question:  Assertion (A) : Hydrochloric acid helps in the digestion of stomach .

Reason (R) : Hydrochloric acid creases and acidic medium to activate protein digesting enzymes . [2021 1M]

(a) Both (A) and (R) are true and (R) is the correct explanation of (A) .

(b) Both (A) and (R) are true but (R) is not the correct explanation of (A) .

(c) (A) is true, but (R) is false .

(d) (A) is false, but (R) is true .

Answer:  (a) Both (A) and (R) are true and (R) is the correct explanation of (A).

[ Assertion (A): Hydrochloric acid helps in digestion in the stomach.
True — it plays an important role in digestion.

Reason (R): Hydrochloric acid creates an acidic medium to activate protein-digesting enzymes (like pepsin).
 True — this is exactly how it helps in digestion. ]

Short Question and Answer

Question: What is the role of saliva in the digestion of food? [1M]

Answer: Saliva helps in digestion by moistening food to make it easy to swallow and by breaking down starch into sugar with the help of the enzyme salivary amylase.

Question: How do autotrophs obtain and to make their food ?    [2008 1M]

Answer: Autotrophs obtain from the atmosphere through photosynthesis and  from nitrogen-fixing bacteria in the soil or water.

Question: What will happen to a plant if its xylem is removed ? [2009 1M]

Answer: If the xylem is removed from a plant, it will be unable to transport water and minerals from the roots to the rest of the plant, causing dehydration and wilting.

Question: What will happen to a plant if its phloem is removed ? [1M]

Answer: If the phloem is removed from a plant, it will be unable to transport sugars and other products of photosynthesis, leading to wilting and eventual death.

Question: Name the green dot like structures in some cells observed by a student when a leaf peel was viewed under a microscope . What is this green colour due to ? [2010 1M]

Answer:  The green dot-like structures observed in leaf cells are chloroplasts. The green color is due to chlorophyll, the pigment responsible for capturing light energy during photosynthesis.

Question: How are fats digested in our bodies? Where does this process take place? [2M]

Answer: Fats are digested in the small intestine. Bile from the liver breaks large fat globules into smaller ones, a process called emulsification, which helps enzymes act efficiently. The pancreas secretes lipase, an enzyme that breaks these emulsified fats into fatty acids and glycerol. This complete digestion occurs in the small intestine with the help of bile and pancreatic juice.

Question: What are the components of the transport system in human beings? What are the functions of these components? [2M]

Answer:  The transport system in human beings consists of blood, heart, and blood vessels.

The functions are : (i) Blood carries oxygen, nutrients, hormones, and waste products to and from the body cells.

(ii) Heart acts as a pump that pushes blood through the blood vessels to all parts of the body.

(iii) Blood vessels form a network of arteries, veins, and capillaries that carry blood to and from the heart and body tissues.

Question: What are the differences between autotrophic nutrition and heterotrophic nutrition? [2M]

Answer: The differences between Autotrophic and Heterotrophic nutrition are :

Autotrophic Nutrition	Heterotrophic Nutrition
Organisms make their own food from simple substances.	Organisms cannot make their own food.
Uses sunlight, carbon dioxide, and water.	Depends on plants or other animals for food.
Food is prepared by photosynthesis.	No photosynthesis occurs.
Found in green plants and algae.	Found in animals, fungi, and humans.
Chlorophyll is present.	Chlorophyll is absent.

Question: Where do plants get each of the raw materials required for photosynthesis? [2M]

Answer: Plants get the raw materials for photosynthesis from different sources. Carbon dioxide comes from the air through small pores called stomata in the leaves. Water is absorbed from the soil by the roots and transported to the leaves through xylem tissues. Sunlight is obtained from the Sun and is trapped by chlorophyll present in green leaves. These raw materials together help plants to prepare their food by photosynthesis.

Question: What is the role of the acid in our stomach? [2M]

Answer: The acid in our stomach, released by the gastric glands, creates an acidic medium which facilitates the action of the enzyme pepsin to digest proteins. It also helps protect the inner lining of the stomach under normal conditions with the mucus secreted by the glands.

Question: What is the function of digestive enzymes? [2M]

Answer: The function of digestive enzymes is to break down complex food molecules into simpler substances that can be easily absorbed by the body. For example, enzymes like amylase break down starch into sugar, pepsin breaks down proteins into smaller peptides, and lipase breaks down fats into fatty acids and glycerol. This helps the body to get nutrients from the food we eat.

Question: Write one function each of the following components of the transport system in human beings : [2008 2M]

(a) Blood   (b) Blood platelets   (c) Lymph   (d) Heart  

Answer:  (a) Blood : Transports oxygen, nutrients, hormones, and wastes throughout the body.

(b) Blood platelets : Help in clotting of blood to stop bleeding.

(c) Lymph : Transports absorbed fats from the intestine and helps in body defence.

(d) Heart : Pumps blood to all parts of the body.

Question: In the experimental set up to show that “ is given out during out during respiration” . Name the substance taken in the small test tube kept in the conical flask . State its function and the consequence of its use . [2019 2M]

Answer: Potassium hydroxide (KOH) . KOH absorbs carbon dioxide (CO₂) present inside the flask.
Since CO₂ produced during respiration is absorbed by KOH, the pressure inside the flask decreases. This causes the liquid (like water) in the delivery tube to move inward, showing that CO₂ is being produced during respiration.

Question: (a) (i) State the role of ATP in cellular respiration.

(ii) what ensures sufficient exchange of gases in plants ?

(iii) State the conditions on which the direction of diffusion of gases in plant depend upon. [3M, 2023]

Answer: (a) (i)  ATP acts as the main energy currency of the cell. It stores and supplies energy needed for various cellular processes like growth, movement, and active transport.

(ii) Stomata and lenticels ensure proper exchange of gases (O₂ and CO₂) between the plant and the environment.

(iii) The direction of diffusion of gases in plants depends on the concentration gradient of gases. Gases move from a region of higher concentration to a region of lower concentration. It also depends on whether the plant is carrying out photosynthesis or respiration, which changes the relative levels of oxygen and carbon dioxide.

Question: (a) (i) What is the internal energy reserve in plants and animals ?

(ii) How desert plants perform photosynthesis if their stomata remain closed during the day ? [3M, 2023]

Answer: (a) (i) The internal energy reserve in plants is primarily stored in the form of starch, while in animals, it is stored as glycogen and fat. These reserves are used to provide energy when needed.

(ii) Desert plants keep their stomata (tiny openings on leaves) closed during the day to save water. Instead, they open their stomata at night to take in carbon dioxide (CO₂) and store it as an acid. During the day, they use this stored CO₂ to perform photosynthesis, even with their stomata closed.

Question:  How are oxygen and carbon dioxide transported in human beings ? How are lungs designed to maximize the area for exchange of gases ? [2008 3M]

Answer: In human beings, oxygen is transported by haemoglobin in red blood cells. It binds with oxygen in the lungs and carries it to all body parts. Carbon dioxide is transported mainly in dissolved form in blood plasma and also by haemoglobin back to the lungs.

The lungs are designed with millions of tiny air sacs called alveoli. These alveoli provide a large surface area, have thin walls, and are surrounded by capillaries, which helps in efficient exchange of gases.

Question: What are the differences between the transport of materials in xylem and phloem ?  [3M]

Answer: The differences between the transport of materials in xylem and phloem are as follows.

Xylem	Phloem
(i) Xylem transports water and minerals from the roots to the aerial parts of the plant, such as the leaves and stems.	(i) Phloem transports organic nutrients, such as sugars and amino acids, from the photosynthetic parts (source) to the non-photosynthetic parts (sink) of the plant.
(ii) Xylem consists of non-living cells called tracheids and vessel elements, which form long tubes for water transport.	(ii) Phloem consists of living cells called sieve elements (sieve tube elements and companion cells) connected end-to-end to form sieve tubes.
(iii) The flow rate in xylem is unidirectional and relatively slow.	(iii) The flow rate in phloem can be bidirectional, allowing for the movement of materials both upwards and downwards in the plant.

Question: Compare the functioning of alveoli in the lungs and nephrons in the kidneys with respect to their structure and functioning. [3M]

Answer: The structure and functioning of alveoli in the lungs and nephrons in the kidneys are :

Alveoli (Lungs)	Nephrons (Kidneys)
Small balloon-like sacs at the end of bronchioles	Small filtering units in kidneys
Surrounded by capillaries for gas exchange	Surrounded by blood vessels for filtration and reabsorption
Thin walls allow easy diffusion of oxygen into blood and carbon dioxide out	Tubular structure allows selective reabsorption of water, salts, and useful substances
Main function: exchange of gases	Main function: excretion of wastes and regulation of water and salts
Provides large surface area for efficient oxygen absorption	Provides large surface area for maximum filtration and reabsorption

Question: What are the differences between aerobic and anaerobic respiration? Name some organisms that use the anaerobic mode of respiration. [3M]

Answer: The differences between aerobic and anaerobic respiration are :

Aerobic Respiration	Anaerobic Respiration
Requires oxygen	Does not require oxygen
Glucose is completely broken down into CO₂ and H₂O	Glucose is partially broken down into lactic acid (in animals) or ethanol and CO₂ (in plants/yeast)
Releases more energy	Releases less energy
Occurs in mitochondria	Occurs in cytoplasm
Examples: Humans, animals, plants	Examples: Yeast, bacteria, some muscle cells (during intense exercise)

Some organisms using anaerobic respiration include yeast and certain bacteria.

Question: Describe double circulation in human beings. Why is it necessary?  [3M]

Answer: Double circulation in humans means that blood passes through the heart twice in one complete cycle of the body. The right side of the heart pumps deoxygenated blood to the lungs to get oxygen, while the left side pumps oxygenated blood to the rest of the body. This separation prevents mixing of oxygen-rich and oxygen-poor blood, ensuring an efficient supply of oxygen to meet high energy needs. It is a key feature of mammals and birds.

It is necessary because it keeps oxygen-rich and oxygen-poor blood separate, ensuring efficient oxygen supply to all body cells.

Long Question and Answer

Question: (a) Draw a diagram of human alimentary canal and label on it :

     Oesophagus , gall bladder , Liver and pancreas

(b) Explain the statement , ‘ Bile does not contain any enzyme but it is essential for digestion ‘ . [2009 5M]

Answer:  (a)  Photo

(b) Bile does not contain digestive enzymes, but it is important because it helps in digestion of fats. It breaks large fat globules into smaller droplets (emulsification), increasing surface area for enzyme action. It also makes the food medium alkaline, which is suitable for pancreatic enzymes to work properly.

Question: (a) Draw a diagram of excretory system in human beings and label on it  :

   Aorta , vena cava , urinary bladder , urethra

(b) List two vital functions of the kidney . [2009 5M]

Answer:  (a) Photo

(b)  Two vital functions of the kidney are:

(i) Removal of nitrogenous wastes (like urea) from the blood through urine.

(ii) Regulation of water and salt balance in the body to maintain proper internal conditions.

Question: Explain the process of digestion of food in mouth , stomach and small intestine in human body [2010 5M]

Answer: Digestion starts in the mouth where food is chewed into small pieces and mixed with saliva. Saliva contains salivary amylase which breaks starch into simple sugars. The tongue helps in mixing and swallowing.

In the stomach, food is mixed with gastric juice containing hydrochloric acid and pepsin. The acid creates an acidic medium and kills germs, while pepsin digests proteins. Mucus protects the stomach lining.

In the small intestine, bile from the liver makes the medium alkaline and emulsifies fats. Pancreatic juice digests proteins and fats. Intestinal juice completes digestion by converting food into glucose, amino acids, fatty acids and glycerol.

Question: (a) List the three events that occur during the process of photosynthesis . Explain the role of stomata in this process .

(b) Describe an experiment to show that ‘‘ sunlight is essential for photosynthesis .’’   [2010 5M]

Answer: (a) The three main events in Photosynthesis are:

(i) Absorption of light energy by chlorophyll.

(ii) Conversion of light energy into chemical energy and splitting of water.

(iii) Reduction of carbon dioxide to form carbohydrates.

Stomata are tiny pores present on the surface of leaves that help in gaseous exchange required for photosynthesis. Carbon dioxide enters the leaf through stomata, while oxygen produced during photosynthesis exits. They are controlled by guard cells, which regulate their opening and closing. When guard cells swell, stomata open; when they shrink, stomata close. This also helps the plant control water loss through transpiration.

Take two similar healthy potted plants and keep them in the dark for three days to remove stored starch. Place each plant on separate glass plates. Keep a watch-glass containing potassium hydroxide near one plant to absorb carbon dioxide. Cover both plants with separate bell-jars and seal the setup airtight using vaseline. Keep the plants in sunlight for a few hours. Then pluck one leaf from each plant and test for starch using iodine solution. The leaf from the plant without potassium hydroxide turns blue-black, while the other does not, showing that sunlight is essential for photosynthesis.

Photo figure 4.5

Question: (a) Mention any two components of blood .

(b) Trace the movement of oxygenated blood in the body .

(c) Write the function of valves present in between the composition of artery and veins . [2018 5M]

Answer: (a) Two components of blood are red blood cells (RBCs) and plasma .

(b)  Oxygenated blood is pumped from the lungs to the left atrium of the heart through pulmonary veins. From the left atrium, it flows into the left ventricle. The left ventricle then pumps this oxygen-rich blood into the aorta, which distributes it through arteries to all parts of the body.

(c) Valves in blood vessels help maintain the one-way flow of blood. In veins, they prevent the backward flow of blood and ensure it moves towards the heart, even against gravity. Arteries generally do not have valves (except near the heart), but valves in veins are important to avoid backflow and maintain proper circulation of blood.

Question: (a) Why is there a difference in the rate of breathing between aquatic organisms and terrestrial organisms ? Explain .

(b) Draw a diagram of human respiratory system and label – pharynx , trachea , lungs , diaphragm and alveolar sac on it . [2020   5M]

Answer: (a) Aquatic organisms breathe faster than terrestrial organisms because water contains much less dissolved oxygen compared to air. To obtain sufficient oxygen, aquatic animals must move more water over their respiratory surfaces (like gills) more frequently. In contrast, terrestrial organisms get oxygen directly from air, which is richer in oxygen, so their breathing rate is comparatively slower.

(b)   Photo

Question:.(a) Name the organs that form the excretory system in human beings .

(b) Describe in brief how urine is produced in human body . [2020 5M]

Answer: The organs that form the excretory system in human beings are: (i) Kidneys    (ii) Ureters   (iii)Urinary bladder   (iv) Urethra

These organs work together to filter waste products from the blood and remove them from the body as urine.

(b) Urine is produced in the human body through the process of filtration, reabsorption, and secretion in the kidneys. Each kidney contains numerous nephrons, which consist of clusters of thin-walled blood capillaries associated with Bowman's capsules. Filtration occurs as blood passes through these capillaries, with waste products and excess substances entering the nephrons. Subsequently, selective reabsorption of essential substances occurs as urine flows through tubules. The formed urine then travels through the ureters to the urinary bladder for storage until it is expelled through the urethra.