Q1: A stomata closes when: (1 Mark) (2024)
(i) it needs carbon dioxide for photosynthesis.
(ii) it does not need carbon dioxide for photosynthesis.
(iii) water flows out of the guard cells.
(iv) water flows into the guard cells.
The correct reason(s) in this process is/are:
(a) (i) only
(b) (i) and (iii)
(c) (ii) and (iii)
(d) (ii) and (iv)
Ans: (c)
Stomata are small openings on the surface of leaves that allow gases to enter and exit the plant. They close when the plant doesn't need carbon dioxide for photosynthesis (which is when it's not producing food) and when water flows out of the guard cells (which helps the plant conserve water). Therefore, the correct answers are (ii) and (iii).
Q2: State one role of each of the following in the human digestive system: (2 Marks) (2024)
(i) Hydrochloric acid
(ii) Villi
(iii) Anal Sphincter
(iv) Lipase
Ans:
(i) Hydrochloric acid: Creates an acidic environment that helps enzymes work and kills harmful microorganisms.
(ii) Villi: Increases the surface area of the intestine, enhancing the absorption of nutrients.
(iii) Anal Sphincter: Controls the release of waste from the body through the anus.
(iv) Lipase: Breaks down fats into smaller molecules, aiding in their digestion.
Q3: (i) Why is respiratory pigment needed in multicellular organisms with large body sizes? (3 Marks) (2024)
(ii) Give reasons for the following:
(a) Rings of cartilage are present in the throat.
(b) Lungs always contain a residual volume of air.
(c) The diaphragm flattens and ribs are lifted up when we breathe in.
(d) Walls of alveoli contain an extensive network of blood vessels.
Ans: (i) In large animals, diffusion alone cannot deliver enough oxygen throughout the body. Instead, respiratory pigments are essential because they:
In humans, the main respiratory pigment is haemoglobin, found in red blood cells, which has a strong affinity for oxygen. Carbon dioxide is mostly carried in a dissolved form in the blood.
(ii) Reasons:
(a) Rings of cartilage in the throat prevent the air passage from collapsing.
(b) Lungs retain a residual volume of air to allow time for oxygen absorption and carbon dioxide release.
(c) When we breathe in, the diaphragm flattens and the ribs lift, making the chest cavity larger, which draws air into the lungs.
(d) The walls of alveoli contain many blood vessels to facilitate gas exchange.
Q4: Which of the following statement(s) is (are) true about human heart? (1 Mark) (CBSE 2024)
(A) Right atrium receives oxygenated blood from lungs through pulmonary artery.
(B) Left atrium transfers oxygenated blood to left ventricle which sends it to various parts of the body.
(C) Right atrium receives deoxygenated blood through vena cava from upper and lower body.
(D) Left atrium transfers oxygenated blood to aorta which sends it to different parts of the body.
(a) (A)
(b) (A) and (D)
(c) (B) and (C)
(d) (B) and (D)
Ans: (c)
Therefore, the correct answer is (c) (B) and (C).
Q5: Photosynthesis takes place in the leaves and the food prepared by it reaches other parts of the plants. Name the process involved and explain it. (1 Mark) (2024)
Ans:
Q6: Which of the following statement (s) is (are) true about human heart? (1 Mark) (2024)
(A) Right atrium receives oxygenated blood from lungs through pulmonary artery.
(B) Left atrium transfers oxygenated blood to left ventricle which sends it to various parts of the body.
(C) Right atrium receives deoxygenated blood from different parts of the body through vena cava.
(D) Left atrium transfers oxygenated blood to aorta which sends it to different parts of the body.
(a) (B) only
(b) (A) and (D)
(c) (B) and (C)
(d) (B) and (D)
Ans: (c)
The correct statements about the human heart are (B) and (C). The left atrium does transfer oxygenated blood to the left ventricle, which then pumps it to the body. The right atrium receives deoxygenated blood from the body through the vena cava, while (A) is incorrect because the right atrium actually receives deoxygenated blood, not oxygenated, and (D) is misleading as the left atrium transfers blood to the left ventricle, not directly to the aorta.
Q7: Case/Source based questions. (4 & 5 Marks) (CBSE 2024)
Human digestive system is a tube running from mouth to anus. Its main function is to breakdown complex molecules present in the food which cannot be absorbed as such into smaller molecules. These molecules are absorbed across the walls of the tube and the absorbed food reaches each and every cell of the body where it is utilised for obtaining energy.
(a) Name the glands present in the buccal cavity and write the components of food on which the secretion of these glands act upon.
(b) Two organs have a sphincter muscle at their exit. Name them.
(c) What will happen if:
(i) mucus is not secreted by the gastric glands.
(ii) Villi are absent in the small intestine.
OR
(c) “Bile juice does not contain any enzyme, yet it has important roles in digestion.” Justify the statement.
Ans: (a) Salivary glands; Starch / Carbohydrate
(b) Stomach, Anus
(c) The consequences of specific conditions are:
(i) If mucus is not secreted by the gastric glands, the inner lining of the stomach will be unprotected from acid, leading to potential damage.
(ii) If villi are absent in the small intestine, the absorption of digested food will be significantly reduced.
OR
(c) Emulsification of fats.
Acidic medium has to be made alkaline for the pancreatic enzymes to act.
Q8: In human beings, when the process of digestion is completed, the (i) proteins, (ii) carbohydrates, and (iii) fats are respectively finally converted into: (1 Mark) (CBSE 2024)
(a) (i) Amino acids, (ii) glucose and (iii) fatty acids
(b) (i) Amino acids, (ii) glucose, (iii) fatty acids and glycerol
(c) (i) Glucose, (ii) fatty acids and glycerol, (iii) amino acids
(d) (i) Sugars, (ii) amino acids, (iii) fatty acids and glycerol
Ans: (b)
During digestion in humans:
The correct answer is (b) as it accurately describes the final products of these macronutrients after digestion.
Q9: We need to water the soil in plants on a regular basis. But it ultimately reaches the leaves of the plant. Explain how this takes place. (1 Mark) (CBSE 2024)
Ans: Water reaches the leaves through the xylem.
This ensures water supply to the leaves for photosynthesis and other processes.
Q10: The process in which transport of soluble products of photosynthesis takes place in plants is known as: (1 Mark) (CBSE 2024)
(a) Transpiration
(b) Evaporation
(c) Conduction
(d) Translocation
Ans: (d)
The process of transporting soluble products of photosynthesis in plants is called translocation. This involves:
Translocation is vital for distributing energy throughout the plant, ensuring that all parts receive the necessary nutrients for growth and development.
Q11: (a) Sometimes while running, the athletes suffer from muscle cramps. Why? How is the respiration in this case different from aerobic respiration?
OR
(b) Write the other name given to lymph. State its two functions. (3 Marks) (CBSE 2024)
Ans: (a)
i. The formation of lactic acid in muscles leads to cramps.
ii. Aerobic respiration occurs with oxygen, while cramps result from anaerobic respiration, which happens without oxygen.
iii. End products of aerobic respiration are carbon dioxide, water, and energy, whereas anaerobic respiration produces lactic acid and energy.
OR
(b) Tissue fluid / Extracellular fluid Functions:
i. Carries digested and absorbed fats from the intestine.
ii. Drains excess fluid from extracellular space back into the blood.
iii. Fight against infections.
Q12: (a) Design an experiment to demonstrate that carbon dioxide is essential for photosynthesis. Write the observation and conclusion of the experiment. (3 Marks) (CBSE 2024)
OR
(b) (i)In the experimental set-up shown above in diagram (I) atmospheric air is being passed into lime water with a syringe while in diagram (II) air is being exhaled into lime water. The time taken for the lime water to turn milky in both the test tubes is different. Give reason.
(ii) Draw the diagram of an open stomatal pore and label (I) Guard cells, and (II) Chloroplast on it. Mention two functions performed by stomata.
Ans: (a)
OR
(b) (i) In set up (I) lime water turns milky in more time as compared to set up (II) because the air we exhaled contains high percentage of CO2 as compared to atmospheric air.
(ii)
Two labellings: (I) Guard Cells
(II) Chloroplast Two functions performed by stomata:
Gaseous exchange
Transpiration
Q13: In human respiratory system, when a person breathes in, the position of ribs and diaphragm will be: (1 Mark) (CBSE 2024)
(a) lifted ribs and curve/dome shaped diaphragm.
(b) lifted ribs and flattened diaphragm.
(c) relaxed ribs and flattened diaphragm.
(d) relaxed ribs and curve/dome shaped diaphragm.
Ans: (b)
The correct answer is (b) lifted ribs and flattened diaphragm. When a person breathes in, the diaphragm contracts and flattens, while the ribs are lifted upward and outward. This movement creates more space in the chest cavity, allowing air to fill the lungs.
Q14: For Q. Nos., two statements are given - One labelled as Assertion (A) and the other labelled as Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below: (1 Mark) (CBSE 2024)
Assertion (A): The rate of breathing in aquatic organisms is much faster than in terrestrial organisms.
Reason (R): The amount of oxygen dissolved in water is very high as compared to the amount of oxygen in air.
(a) Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
(b) Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).
(c) Assertion (A) is true, but Reason (R) is false.
(d) Assertion (A) is false, but Reason (R) is true.
Ans: (c)
The correct answer is (c) Assertion (A) is true, but Reason (R) is false. Aquatic organisms do breathe faster than terrestrial organisms because they need to extract enough oxygen from water, which has less oxygen available than air. Therefore, while the assertion is correct, the reason given is incorrect because it states that water has a high amount of dissolved oxygen, which is not true compared to air.
Q15: In a nerve cell, the site where the electrical impulse is converted into a chemical signal is known as: (1 Mark) (CBSE 2024)
(a) Axon
(b) Dendrites
(c) Neuromuscular junction
(d) Cell body
Ans: (c) Neuromuscular junction
(a) Axon: The axon transmits electrical impulses away from the cell body but does not convert them into chemical signals.
(b) Dendrites: Dendrites receive electrical signals from other nerve cells but do not convert them into chemical signals.
(c) Neuromuscular junction: The correct answer, as this is where the electrical impulse is converted into a chemical signal during neurotransmission.
(d) Cell body: The cell body contains the nucleus and other cell structures but does not convert electrical impulses into chemical signals.
The correct answer is: (c) Neuromuscular junction
Q16: Study the diagram given below and answer the questions that follow: (3 Marks) (CBSE 2024)(i) Name the defect of vision represented in the diagram. Give reason for your answer.
(ii) List two causes of this defect.
(iii) With the help of a diagram show how this defect of vision is corrected.
Ans: (i) Hypermetropia or Far-sightedness.
Reason – Image is formed behind the retina.
Near point for the person is farther away from the normal near point (25 cm)
(ii)
(iii)
N = Near point of a hypermetropic eye
N’= Near point of a normal eye
Q1: Opening and closing of stomata is due to (1 Mark) (2023)
(a) High pressure of gases inside the cells
(b) Movement of water in and out of the guard cells
(c) Stimulus of light in the guard cells
(d) Diffusion of CO2 in and out of the guard cells.
Ans: (b)
The opening and closing of stomata are indeed regulated by the movement of water in and out of guard cells. Here’s a brief explanation of how it works:
Mechanism of Stomatal Movement:
Guard Cells and Stomata:
Opening of Stomata:
Closing of Stomata:
Q2: Assertion (A): The inner walls of the small intestine have finger like projections called villi which are rich in blood. (1 Mark) (2023)
Reason (R): These villi have a large surface area to help the small intestine in completing the digestion of food.
(a) Both (A) and (R) are true and (R) is the correct explanation of (A).
(b) Both (A) and (R) are true and (R) is not the correct explanation of (A).
(c) (A) is true but (R) is false.
(d) (A) is false but (R) is true.
Ans: (c)
Assertion (A):
Reason (R):
Conclusion: (A) is true, but (R) is false.
Q3: Water in the root enters due to (1 Mark) (2023)
(a) The function of the root to absorb water
(b) Difference in the concentration of ions between the root and the soil
(c) Excess water present in the soil
(d) Diffusion of water in the roots
Ans: (b)
Q4: As compared to terrestrial organisms, the rate of breathing in aquatic organism is (1 Mark) (2023)
(a) Faster because they need more oxygen for their survival
(b) Faster because the amount of dissolved oxygen in water is fairly low
(c) Slower because the amount of dissolved oxygen in water is fairly low
(d) Slower because the capacity of water of dissolving atmospheric air is limited
Ans: (b)
In aquatic organisms, the rate of breathing is higher.
These organisms utilize oxygen dissolved in water.
The amount of dissolved oxygen in water is relatively low compared to the oxygen available in the air.
Therefore, aquatic organisms need to breathe faster to obtain sufficient oxygen for their survival.
Q5: Observe the following diagram and identify the process and its significance from the following options: (1 Mark) (2023)(a) Evaporation : maintains water contents in leaf cells.
(b) Transpiration : creates a suction force which pulls water inside the plant.
(c) Excretion : helps in excreting out waste water from the plant.
(d) Translocation : helps in transporting materials from one cell to another.
Ans: (b)
Transpiration is a vital process in plants that involves the loss of water vapour from the aerial parts, primarily leaves. This process plays a crucial role in several ways:
During the day, when the stomata are open, transpiration becomes the main driving force for water movement. At night, root pressure assists in this transport. Overall, transpiration is essential for maintaining the plant's hydration and nutrient supply.
Q6: The process in which loss of water in the form of vapours from the aerial parts of plants takes place is X, which helps in Y. Here, X and Y respectively are (1 Mark) (2023)
(a) Transpiration and photosynthesis
(b) Transpiration and temperature regulation
(c) Translocation and movement of soluble products of photosynthesis in phloem
(d) Translocation and absorption of water and minerals from soil by roots.
Ans: (b)
Q7: Assertion (A) : The walls of atria are thicker than those of the ventricles. (1 Mark) (2023)
Reason (R) : Ventricles have to pump blood into various organs at high pressure.
(a) Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A)
(b) Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A)
(c) Assertion (A) is true, but Reason (R) is false.
(d) Assertion (A) is false, but Reason (R) is true.
Ans: (d)
Assertion (A): The walls of atria are thicker than those of the ventricles.
Reason (R): Ventricles have to pump blood into various organs at high pressure.
Therefore, while Reason (R) correctly explains the physiological need for thicker ventricular walls due to high-pressure pumping, Assertion (A) is incorrect because the ventricular walls are thicker than atrial walls, not the other way around.
Q8: Two green plants are kept separately in oxygen-free containers, one in the dark and the other in sunlight. It was observed that plants kept in the dark could not survive longer. Give a reason for this observation. (2 Marks) (2023)
Ans: The plant kept in the dark could not survive longer because:
As a result, the plant in the dark cannot sustain itself and eventually dies.
Q9: List the events that take place during the process of photosynthesis in the proper sequence. (2 Marks) (2023)
Ans: The three events that occur during the process of photosynthesis are;
(i) Absorption of light energy by chlorophyll.
(ii) Conversion of light energy to chemical energy (in the form of ATP and NADPH) and splitting of water molecules into hydrogen and oxygen.
(iii) Reduction of carbon dioxide to carbohydrates (carbon assimilation).
Q10: (i) How does Paramecium obtain its food? (3 Marks) (2023)
(ii) List the role of each of the following in our digestive system:
(a) Hydrochloric acid
(b) Trypsin
(c) Muscular walls of the stomach
(d) Salivary amylase
Ans: (i) In Paramecium, a unicellular protozoan, the hair-like outgrowth cilia are present on the entire surface and help collect the food. They sweep the food inside the body through the oral groove.
(ii) (a) Role of hydrochloric acid: It helps to maintain the acidic pH in the stomach required for activation of the enzyme pepsin that digests proteins in the stomach.
(b) Role of trypsin in our digestion system: Trypsin breaks down protein into smaller peptides in the duodenum of the small intestine. It helps in digesting dietary protein by breaking the chain of amino acids. It also activates some proenzymes present in pancreatic juice.
(c) Role of muscular walls in the stomach in our digestive system: The muscular walls in the stomach contract periodically and thereby help in the churning and mixing of the food with the digestive enzymes and HCI. It helps in chemical digestion.
(d) Role of salivary amylase in our digestive system: Salivary amylase found in saliva breaks down the starch and converts it into the simplest sugar.
Q11: (a) With the help of an activity, explain the action of saliva on the food we eat. (3 Marks) (2023)
(b) Why is bile juice important in the process of digestion?
Ans: (a) The action of saliva on food can be demonstrated through a simple activity:
Results:
(b) Bile juice plays a crucial role in digestion:
Q12: What is the other name of 'tissue fluid'? Write its two functions. (2 Marks) (2023)
Ans: Tissue fluid is also called lymph. The functions of tissue fluid are:
(i) It carries digested and absorbed fat from the intestine.
(ii) It drains excess fluid from extracellular space back into the blood.
Q13: What will happen if: (2 Marks) (2023)
(a) Xylem tissue in a plant is removed.
(b) We are injured and start bleeding?
Ans: (a) If the xylem is removed, transport of water and minerals from the soil would not occur, which leads to the wilting of leaves and, ultimately, the death of the plant.
(b) In case of any injury, when bleeding occurs, platelets circulate around the body and form a mesh-like network or clot at the site of injury.
Q14: (i) What is double circulation? (3 Marks) (2023)
(ii) Why is the separation of the right side and the left side of the heart useful? How does it help birds and mammals?
Ans: (i) Double circulation is a system where blood passes through the heart twice during one complete cycle. It consists of two main pathways:
(ii) The separation of the heart into right and left sides is beneficial because:
In summary, the distinct sides of the heart ensure that oxygen-rich blood is effectively circulated to all body parts, supporting the energy demands of these animals.
Q15: Write one specific function of each of the following organs in relation to excretion in human beings: (2 Marks) (2023)
(i) Renal Artery
(ii) Urethra
(ii) Glomerulus
(iv) Tubular part of nephron
Ans: (i) Renal artery: Carries blood from the aorta to the kidneys for filtration.
(ii) Urethra: Transports urine from the bladder to the outside of the body.
(iii) Glomerulus: Filters blood to initiate the formation of urine.
(iv) Tubular part of nephron: Enables selective reabsorption of essential substances like glucose, amino acids, salts, and water into the blood.
Q16: Explain in brief two ways by which leaves of a plant help in excretion. (2 Marks) (2023)
Ans: Leaves of a plant assist in excretion in the following ways:
Q17: An organism which breaks down the food material outside the body and then absorbs it is:
(a) a plant parasite, Cuscuta
(b) an animal parasite, Tapeworm
(c) a bacteria, Rhizobium
(d) a fungi, Rhizopus (1 Mark) (CBSE 2023)
Ans: (d)
(i) Rhizopus is a fungus that performs extracellular digestion. It secretes digestive enzymes outside its body to break down food material into simpler substances, which are then absorbed.
(ii) Cuscuta is a plant parasite that absorbs nutrients directly from the host plant.
(iii) Tapeworm is an animal parasite that lives inside the host's body and absorbs pre-digested nutrients.
(iv) Rhizobium is a nitrogen-fixing bacterium associated with legume roots; it does not break down food outside the body for absorption.
Therefore, (d) a fungi, Rhizopus is correct, as it digests food material outside its body and then absorbs it.
Q18: Consider the following statements about small intestine and select the one which is NOT correct:
(a) The length of the small intestine in animals differ 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 receive secretions from liver and pancreas.
(d) The villi of the small intestine absorb water from the unabsorbed food before it gets removed from the body via the anus. (1 Mark) (CBSE 2023)
Ans: (d)
(a) This statement is correct. The length of the small intestine varies among animals depending on their diet. Herbivores generally have longer small intestines than carnivores to allow more time for digesting plant material.
(b) This statement is correct. The small intestine is the primary site for the complete digestion of food, where nutrients are broken down and absorbed.
(c) This statement is correct. The small intestine receives secretions from the liver (bile) and the pancreas (pancreatic enzymes) that aid in digestion.
(d) This statement is incorrect. The main function of the villi in the small intestine is to absorb nutrients, not water. Water absorption primarily occurs in the large intestine, not the small intestine.
Therefore, the correct answer is (d), as it is the statement that is NOT correct.
Q19: Name the type of blood (oxygenated/ deoxygenated) transported by each of the following mentioning the path i.e., from one organ (which place) to another (which place).
(A) Vena cava
(B) Pulmonary artery (3 Marks) (CBSE 2023)
Ans: (A) Vena cava: The vena cava consists of two main veins:
(B) Pulmonary artery:
Q20: (A) State the role of ATP in cellular respiration.
(B) What ensures sufficient exchange of gases in plants?
(C) State the conditions on which the direction of diffusion of gases in plant depend upon. (3 Marks) (CBSE 2023)
Ans: (A) ATP in Cellular Respiration:
(B) Gas Exchange in Plants:
(C) Conditions Affecting Gas Diffusion:
Q1: In human alimentary canal, the specific enzyme/ juice secreted in locations (i), (ii) and (iii) are (2022)
(a) (i) Amylase (ii) Pepsin (iii) Bile
(b) (i) Amylase (ii) Bile (iii) Trypsin
(c) (i) Lipase (ii) Amylase (iii) Pepsin
(d) (i) Trypsin (ii) Bile (iii) Amylase
Ans: (b)
Saliva is secreted in the mouth (i) and contains the enzyme salivary amylase, which helps digest carbohydrates. The liver (ii) secretes bile to emulsify fats, breaking them into smaller globules for easier digestion. The pancreas (iii) produces pancreatic juice, which contains enzymes like trypsin for protein digestion.
Q2: Read the following and answer the questions from (i) to (iv). (2022)
Take a healthy potted plant with elongated leaves. Select a leaf and insert about one half of this leaf in a test tube containing KOH and make it air tight. Place the set-up in sun for two hours. Take out the leaf from the test tube and dip it in boiling water for a few minutes. Put this leaf in a beaker with alcohol and boil it in a water bath. Wash the leaf with water and then dip the leaf in iodine solution for a few minutes. The portion of the leaf dipped in KOH solution will not show any change when dipped in iodine solution.
(i) The function of KOH taken in the test tube is to absorb
(a) Released water vapours
(b) Released CO2
(c) Released O2
(d) Chlorophyll.
Ans: (b)
In the given experiment, KOH (Potassium hydroxide) in the test tube absorbs carbon dioxide; thus, due to the absence of CO2, the leaf fails to produce starch which proves that carbon dioxide is necessary for photosynthesis.
(ii) On the basis of this activity, we may conclude that the factor for photosynthesis is
(a) Carbon dioxide
(b) Oxygen
(c) Chlorophyll
(d) Water vapour.
Ans: (a)
The given experiment demonstrates the requirement of carbon dioxide for photosynthesis. When KOH absorbs the available CO2 from the portion of leaf dipped in it, formation of sugar and starch is inhibited and the portion of leaf dipped in KOH did not show any change when dipped in iodine solution. Thus, it is proved that CO2 is necessary for photosynthesis.
(iii) The event that does not occur in photosynthesis is
(a) Absorption of light energy by chlorophyll
(b) Reduction of carbon dioxide to carbohydrates
(c) Oxidation of carbon to carbon dioxide
(d) Conversion of light energy to chemical energy.
Ans: (c)
Following are the three events that occur during the process of photosynthesis
(i) Absorption of light energy by chlorophyll.
(ii) Conversion of light energy to chemical energy and splitting of water molecules into hydrogen and oxygen.
(iii) Reduction of carbon dioxide to carbohydrates.
(iv) Iodine solution gives blue-black colour with
(a) Starch
(b) Proteins
(c) Glucose
(d) Fats.
Ans: (a)
The brown coloured iodine will turn blue-black when it reacts with starch.
Q3: The correct statements with reference to single celled organisms are (2022)
(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).
Ans: (c)
Unicellular organisms are one-celled and perform all the life processes that are essential for maintaining the life of cell or organisms like nutrition, respiration, reproduction, excretion, etc. In single-celled organisms such as Amoeba, complex substances are broken into simpler substances.
Q4: Which one of the following conditions is true for the state of stomata of a green leaf shown in the given diagram?
(a) Large amount of water flows into the guard cells.
(b) Gaseous exchange is occurring in large amount.
(c) Large amount of water flows out from the guard cells.
(d) Large amount of sugar collects in the guard cells.
Ans: (c)
The opening and closing of the stomatal pore depend on the turgidity of the guard cells. When guard cells lose water, they become flaccid, leading to a closed stomatal pore. Conversely, when they swell with water, the pore opens.
Q5: Assertion (A): Nitrogen is an essential element for plant growth and is taken up by plants in the form of inorganic nitrates or nitrites. (2022)
Reason (R) : The soil is the nearest and richest source of raw materials like nitrogen, phosphorus and other minerals for the plants.
(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.
Ans: (b)
The correct answer is (b) Both (A) and (R) are true but (R) is not the correct explanation of (A). Nitrogen is indeed essential for plant growth, and plants absorb it mainly as inorganic nitrates or nitrites. However, while the soil is a rich source of nutrients for plants, the reason provided does not directly explain why nitrogen is taken up in that specific form, so it’s not a correct explanation of the assertion.
Q6: 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 (2022)
(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.
Ans: (c)
Both potted plants should be kept in sunlight for about two hours before the starch test.
Q7: 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 (2022)
(a) Mode of intake of food
(b) Type of food consumed
(c) Presence or absence of villi in intestines
(d) Presence or absence of digestive enzymes.
Ans: (b)
The length of the small intestine in a deer is greater than that of a tiger due to their differing diets.
The structure of the small intestine is adapted to the dietary needs of each animal, reflecting their evolutionary differences.
Q8: The sequence of anaerobic respiration in our muscle cells during heavy exercise is (2022)
(a)
(b)
(c)
(d)
Ans: (a)
During heavy exercise, when oxygen is scarce in our muscle cells, the process of anaerobic respiration occurs. Here’s a simplified breakdown:
Q9: The energy released during cellular respiration is used to synthesise (2022)
(a) Ribosomes
(b) RBC
(c) ATP
(d) mitochondria.
Ans: (c)
The energy released during cellular respiration is immediately used to synthesise a molecule called ATP which is energy currency of the cell and is used as fuel for cellular activities.
Q10: Which of the following statements are correct in reference to the role of A (shown in the given diagram) during a breathing cycle in human beings? (2022)
(i) It helps to decrease the residual volume of air in lungs.
(ii) If flattens as we inhale.
(iii) It gets raised as we inhale.
(iv) It helps the chest cavity to become larger.
(a) (ii) and (iv)
(b) (iii) and (iv)
(c) (i) and (ii)
(d) (i), (ii) and (iv)
Ans: (a)
During inhalation, we lift our ribs and flatten our diaphragm (A), which enlarges the chest cavity. This creates a vacuum that pulls air into the lungs, filling the expanded alveoli.When we exhale, our ribs and diaphragm return to their normal positions, causing the chest cavity to shrink. This pushes air out of the lungs.
Q11: Assertion (A): The rate of breathing in aquatic organisms is much slower than that seen in terrestrial organisms. (2022)
Reason (R): The amount of oxygen dissolved in water is very low as compared to the amount of oxygen in air.
(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.
Ans: (d)
The rate of breathing in aquatic organisms is much slower than that seen in terrestrial organisms.The rate of breathing in aquatic organisms is actually much faster than in terrestrial organisms due to the following reasons:
Q12: The function of the lining of mucus in the nasal passage of human beings is to (2022)
(a) Increase the temperature of inhaled air
(b) Move the air in and out
(c) Filter the air that we breathe in
(d) Absorb oxygen from the air.
Ans: (c)
The mucus lining in the nasal passage serves several important functions:
Q13: In living organisms during respiration which of the following products are not formed if oxygen is not available? (2022)
(a) Carbon dioxide + Water
(b) Carbon dioxide + Alcohol
(c) Lactic acid + Alcohol
(d) Carbon dioxide + Lactic Acid
Ans: (a)
In aerobic respiration, glucose is completely broken down to CO2 and H2O with the production of a large amount of energy (ATP).
Thus, CO2 and water are formed as a result of aerobic ; respiration and will not formed in the absence of oxygen (anaerobic respiration).
Q14: Respiratory structures of two different animals-a fish and a human being are shown. (2022)
Observe (A) and (B) and select one characteristic that hold true for both of them.
(a) Both are placed internally in the body of animal.
(b) Both have thin and moist surface for gaseous exchange.
(c) Both are poorly supplied with blood vessels to conserve energy.
(d) In both the blood returns to the heart after being oxygenated.
Ans: (b)
Q15: Observe the diagram of an activity given below. What does it help to conclude, when the person exhales into the test-tube? (2022)
(a) Percentage of carbon dioxide is more in inhaled air.
(b) Fermentation occurs in the presence of oxygen.
(c) Percentage of carbon dioxide is more in the exhaled air.
(d) Fermentation occurs in the presence of carbon dioxide.
Ans: (c)
Q16: The separation of the right side and the left side of heart is useful to (2022)
(a) Keep oxygenated blood from mixing with deoxygenated blood
(b) Allow a slow supply of oxygen in the body
(c) Supply energy to animals with low energy needs
(d) Often change their body temperature.
Ans: (a)
Q17: In spring, sugar stored in root or stem tissue of plants is transported to the buds for (2022)
(a) The energy needs of the buds to grow
(b) Temperature regulation
(c) Balancing the storage in different organs
(d) Diffusion process.
Ans: (a)
In spring, new buds are formed. These buds need more energy to grow than other parts of the plant. This energy comes from the sugar stored in root or stem tissue and is transported to the buds by phloem.
Q18: Upward movement of water in tall trees is due to (2022)
(a) Translocation
(b) Excretion
(c) Photosynthesis
(d) Transpiration.
Ans: (d)
The upward movement of water in tall trees is primarily driven by transpiration. This process involves:
Q19: Thin walled blood vessels are called (2022)
(a) Aorta
(b) Capillaries
(c) Arteries
(d) Vena cava
Ans: (b)
Capillaries are tiny blood vessels with very thin walls, just one cell thick. They play a crucial role in the body by:
After the exchange, capillaries merge to form veins, which carry blood away from the tissues.
Q20: Consider the following statements in connection with the functions of the blood vessels marked A and B in the diagram of a human heart as shown. (2022)
(i) Blood vessel A - It carries carbon dioxide rich blood to the lungs.
(ii) Blood vessel B - It carries oxygen rich blood from the lungs.
(iii) Blood vessel B - Left atrium relaxes as it receives blood from this blood vessel.
(iv) Blood vessel A - Right atrium has thick muscular wall as it has to pump blood to this blood vessel.
The correct statements are
(a) (i) and (ii) only
(b) (ii) and (iii) only
(c) (ii), (iii) and (iv)
(d) (i), (ii) and (iii).
Ans: (d)
Blood vessel A represents the pulmonary artery, while blood vessel B signifies the pulmonary vein.
The key functions of these blood vessels are:
Thus, oxygen-rich blood from the lungs enters the heart via the pulmonary vein, ensuring efficient oxygen supply to the body.
Q21: Identify the two components of phloem tissue that help in transportation of food in plants. (2022)
(a) Phloem parenchyma and sieve tubes
(b) Sieve tubes and companion cells
(c) Phloem parenchyma and companion cells
(d) Phloem fibres and sieve tubes
Ans: (b)
The two components of phloem tissue that assist in the transportation of food in plants are:
Q22: Read the following and answer the questions from (i) to (iv). (2022)
The figure shown below represents a common type of dialysis called as haemodialysis- It removes waste products from the blood, such as excess salts, and urea which are insufficiently removed by the kidney in patients with kidney failure. During the procedure, the patient's blood is cleaned by filtration through a series of semi-permeable membranes before being returned to the blood of the patient. On the basis of this answer the following questions.
(i) The haemodialyser has semi-permeable lining c tubes which help
(a) To maintain osmotic pressure of blood
(b) To filter nitrogenous wastes from the dialysin solution
(c) In passing the waste products in the dialysing solution
(d) To pump purified blood back into the body of the patient.
Ans: (c)
(ii) 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 reabsorb essential nutrients from the blood.
(d) To filter and purify the blood.
Ans: (c)
(iii) The 'used dialysing' solution is rich in
(a) Urea and excess salts
(b) Blood cells
(c) Lymph
(d) Proteins.
Ans: (a)
(iv) Which part of the nephron in human kidney, serves the function of reabsorption of certain substances
(a) Glomerulus
(b) Bowman's Capsule
(c) Tubules
(d) Collecting Duct
Ans: (c)
Q1: (i) Plants absorb water from the soil. Explain how it is taken up and transported from the soil. (2021)
(ii) "When we are injured and start bleeding, it requires the loss of blood from the system to be minimized." What will happen if the blood loss is not stopped? Is there anything the system could do on its own to prevent the loss?
Ans: (i)
Q1: In the human body, the site of absorption of digested food is the small intestine. How is the process of absorption carried out, and why is the absorption of digested food necessary? (2020)
Ans:
Q2: Complete the following flow chart as per the given instructions. (2020)
Ans: a - Hydrochloric acid (HCI)
b - Pepsin
c - Mucus
d - HCI makes medium acidic for the activation of an enzyme pepsin.
e - Pepsin acts in an acidic medium, which breaks down proteins into peptones.
f - The mucus protects the inner lining of the stomach from the corroding action of HCI.
Q3: (a) State the role played by the following in the process of digestion: (2020)
(i) Enzyme trypsin
(ii) Enzyme lipase
(b) List two functions of finger-like projections present in the small intestine.
Ans: (a) (i) Enzyme trypsin: This enzyme is produced by the pancreas in an inactive form called trypsinogen.
Trypsin converts the remaining proteins into peptones, and the peptones into peptides and amino acids.
(ii) Enzyme lipase: It is secreted by the pancreas and small intestine. Lipase converts fats into fatty acids and glycerol.
(b) Internally, the wall of the small intestine is provided with long finger-like projections called villi. Two functions of villi are:
(i) The villi greatly increase the absorptive surface area of the inner lining of the small intestine.
(ii) Villi are richly supplied with blood vessels that carry absorbed food to all cells of the body, where it is utilized for obtaining energy.
Q4: (a) In the process of respiration, state the function of alveoli. (2020)
(b) The rate of breathing in aquatic organisms is much faster than that in terrestrial organisms. Give reasons.
(c) Complete the following pathway showing the breakdown of glucose.
Ans: (a) Functions of alveoli are:
(i) They increase the surface area for the exchange of gases.
(ii) The thin walls of alveoli facilitate the rapid exchange of oxygen and carbon dioxide between alveolar air and blood.
(b) Aquatic animals like fishes obtain dissolved oxygen from water present through their gills. The amount of dissolved oxygen is quite small compared to the amount of oxygen in the air. Therefore, to obtain the required amount of oxygen from water, aquatic animals have to breathe much faster than terrestrial organisms.
(c)
Q5: Give reasons: (2020)
(a) Ventricles have thicker muscular walls than atria.
(b) The transport system in plants is slow.
(c) Circulation of blood in aquatic vertebrates differs from that in terrestrial vertebrates.
(d) During the daytime, water and minerals travel faster through the xylem as compared to the night.
(e) Veins have valves, whereas arteries do not.
Ans: (a) Since ventricles have to pump blood into various organs with high pressure, they have thicker walls than atria.
(b) The transport system in plants is slow due to:
(c)
(d) During the daytime, water and minerals travel faster through the xylem because the rate of transpiration is higher during the daytime.
(e) The lumen of veins has valves, which allow the blood to flow in only one direction. Thus preventing the backflow of blood.
Q6: (a) "Blood circulation in fishes is different from the blood circulation in human beings”. Justify the statement.
(b) Describe "blood circulation” in human beings. (2020)
Ans: (a)
Q7: (a) Describe the structure and function of the basic filtering unit of the kidney. (2020)
(b) List two factors on which the reabsorption of water from urine depends.
Ans: (a) Nephron is the structural and functional unit of the kidney. Its main role is to regulate the concentration of water and soluble substances like sodium and other salts by filtering the blood, reabsorbing the excess water that is needed, and excreting the rest as urine.
(b) Two factors on which the reabsorption of water from urine depends are:
Q8: (a) Name the organs that form the excretory system in human beings. (2020)
(b) Describe in brief how urine is produced in the human body.
Ans: (a) The Excretory system (urinary system) in human beings consists of a pair of kidneys, a pair of ureters, a urinary bladder and a urethra.
(b)
Q9: (a) Why is nutrition necessary for the human body? (CBSE 2020)
(b) What causes the movement of food inside the alimentary canal?
(c) Why is the small intestine in herbivores longer than in carnivores?
(d) What will happen if mucus is not secreted by the gastric glands?
Ans: (a)
(d) If mucus is not secreted by the gastric glands:
Q10: (a) Why is there a difference in the rate of breathing between aquatic organisms and terrestrial organisms? Explain. (2020)
(b) Draw a diagram of the human respiratory system and label it - the pharynx, trachea, lungs, diaphragm and alveolar sac on it.
Ans: (a)
(b) The labelled diagram of the human respiratory system is as follows
Q11: (A) Write the correct sequence of steps followed during journey of oxygen rich blood from lungs to various organs of human body. (B) What happens when the system of blood vessels develop a leak? (CBSE 2020)
Ans: (A) Journey of oxygen rich blood from lungs to various parts of the body is as follows:
(i) The pulmonary vein brings the oxygenated blood from the lungs in the left atrium of the heart.
(ii) The left atrium contracts and pumps blood into left ventricle through the valve.
(iii) When the left ventricle contracts, the oxygenated blood enters the largest artery known as aorta.
(iv) The blood travels from the aorta to larger and smaller arteries into the capillaries.
(v) The aorta transports the blood to all the organs of the body except the lungs.
(vi) The oxygenated blood releases oxygen, nutrients and other substances and takes away carbon dioxide and waste substances.
(vii) The deoxygenated blood enters the vena cava, which carries it to the right atrium of the heart
(B) When the system of blood vessels develop a leak, the platelets will increase, which will minimise the leakage. Whenever there is a leak in the blood vessels, the blood flows, through them. If not checked, that may cause an excessive loss of blood.
Q1: Name an enzyme present in pancreatic juice. (2019)
Ans: Pancreatic juice contains the digestive enzyme trypsin.
Q2: What causes the movement of food inside the alimentary canal in human beings? (2019)
Ans:
Q3: (a) Write the function of the following in the human alimentary canal: (CBSE 2019)
(i) Saliva
(ii) HCI in the stomach
(iii) Bile juice
(iv) Villi
(b) Write one function for each of the following enzymes:
(i) Pepsin
(ii) Lipase
Ans: (a) (i) Saliva contains salivary amylase and is released in our mouth. It breaks down starch into sugar (complex carbohydrates into simpler ones).
(ii) Acid (HCI) plays an important role in the process of digestion. These are:
(b) (i) Pepsin is a protein-digesting enzyme present in gastric juice. Pepsin gets activated in an acidic medium and splits proteins into peptones and peptides.
(ii) Lipase is secreted by the pancreas and small intestine. Lipase converts fats into fatty acids and glycerol.
Q4: Write two different ways in which glucose is oxidized to provide energy in the human body. Write the products formed in each case. (2019)
Ans: The two different ways by which glucose is oxidized to provide energy in the human body are:
(i) Aerobic respiration (In the presence of oxygen): The end products in aerobic respiration are carbon dioxide, water, and energy.
(ii) Anaerobic respiration (In the lack of oxygen): The end products are lactic acid and energy.
Q5: Explain the ways in which glucose is broken down in the absence or shortage of oxygen. (2019)
Ans: In the absence or shortage of oxygen, glucose is oxidized in the following ways:
(i) In cytoplasm, glucose is oxidized to pyruvate and release energy.
(ii) In the muscles of humans, i.e., under anaerobic conditions, pyruvate breaks down to lactic acid and releases energy.
(iii) In yeast, i.e., during the fermentation process, pyruvate converts to ethanol while carbon dioxide releases a certain amount of energy.
Q6: (a) List in tabular form two differentiating features between xylem and phloem. (2019)
(b) Write two advantages of transpiration in plants.
Ans: (a) Differences between transport in the xylem and transport in the phloem are as follows:
(b) Significance of transpiration in plants:
(i) The absorbed water is transported from roots to leaves through xylem vessels, which is greatly influenced by transpiration pull.
(ii) The water stream moving upwards carries dissolved minerals with it. Transpiration also helps in distributing these minerals throughout the plant.
(iii) The evaporation of water during transpiration provides a cooling effect to the leaves.
Q7: Write three types of blood vessels. Give one important feature of each. (2019)
Ans: The three types of blood vessels in the human body are:
(i) Arteries are the blood vessels that carry blood from the heart to various parts of the body. They are thick-walled, elastic, and muscular, which enables them to dilate but do not rupture when the heart contracts and forces blood into them.
(ii) Veins are thin-walled blood vessels that bring blood from the body back to the heart. They are larger and hold more blood than the arteries. The lumen of veins has valves which prevent the backflow of blood.
(iii) Capillaries are thin-walled and extremely narrow blood vessels that occur at the terminals of arteries and veins. The walls of capillaries are permeable to water and dissolved substances so that the exchange of materials between the blood and body cells can take place.
Q8: (a) Write two water-conducting tissues present in plants. How does water enter continuously into the root xylem? (2019)
(b) Explain why plants have low energy needs as compared to animals.
Ans: (a)
Q9: List four functions of the human heart. Why is double circulation necessary in the human body? (2019)
Ans: The functions of the human heart include:
The human heart consists of two sides: the right side and the left side. The right side receives deoxygenated blood and sends it to the lungs for purification. The left side receives oxygenated blood from the lungs and pumps it to the rest of the body. This process is known as double circulation.
Double circulation is necessary because:
Q10: (a) Define the term excretion. Why should animals excrete waste matter? (2019)
(b) Name the main excretory organ of human beings and state the form in which the excretory matter is thrown out of the body.
Ans: (a) Excretion is a biological process that removes harmful metabolic wastes from the body. Key points include:
Overall, excretion is essential for maintaining the body's health by preventing the buildup of toxic substances.
(b) A pair of kidneys are the main excretory organs in a human being. It helps excrete nitrogenous waste in the form of urea, toxins, excess salts, water-soluble vitamins, etc. and then eliminates it in the form of urine.
Q11: In the experimental set-up to show that "CO2 is given 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)
Ans: In the experiment in which carbon dioxide is given out during respiration, KOH (potassium hydroxide) solution or pellets are taken in a tube and placed within the conical flask. KOH absorbs the carbon dioxide, and it prevents the carbon dioxide from being utilized by the plant for the process of photosynthesis. Function of KOH
KOH: KOH solution kept in the flask absorbs carbon dioxide and creates a partial vacuum in the flask. The air present in the bent tube moves into a conical flask, and this pulls the water level up in the tube. Consequences:
Q12: In the experimental setup shown:
(A) Name the material X filled in the small test tube and the material Y placed at the bottom of the conical flask.
(B) Why is there a rise in water level in the delivery tube? (CBSE 2019)
Ans: (A) X - KOH pellets
Y - Wet germinating seeds
(B) Seeds use oxygen present in the flask and release carbon dioxide which is absorbed by potassium hydroxide. Thus, partial vacuum is created in the conical flask, as a result, water from the beaker rises in the delivery tube
Q13: Write the function of the following in the human alimentary canal: (CBSE 2019)
(i) Saliva
(ii) HCI in the stomach
(iii) Bile juice
(iv) Villi
Ans: (i) Saliva contains salivary amylase and is released in our mouth. It breaks down starch into sugar (complex carbohydrates into simpler ones).
(ii) Acid (HCI) plays an important role in the process of digestion. These are:
Q14: Give reasons for the following:
(A) There is a difference in the rate of breathing between aquatic organisms and terrestrial organisms.
(B) Plants have low energy needs as compared to animals. (CBSE 2019)
Ans: (A) The rate of breathing differs between aquatic and terrestrial organisms due to their environments:
(B) Plants have lower energy needs compared to animals for several reasons:
Q1: (a) Mention any two components of blood. (2018)
(b) Trace the movement of oxygenated blood in the body.
(c) Write the function of valves present in between atria and ventricles.
(d) Write one structural difference between the composition of arteries and veins.
Ans: (a) Two components of blood are blood plasma and blood corpuscles.
(b) Oxygenated blood from lungs → Pulmonary veins → Left atrium of heart → Left ventricle → Aorta → Arteries → Body parts
(c) When blood is pumped, valves prevent the backflow of blood between ventricles and atria. They open and allow the right amount of blood to flow from one chamber to the other.
(d) Structural difference between veins and arteries is as follows:
Q2: (a) Name the process and explain the type of nutrition found in green plants. List the raw materials required for this process. Give a Chemical equation for the mentioned process. (2018)
(b) Write three events that occur during this process.
Ans: (a) Photosynthesis is the process where green plants show autotrophic nutrition. The raw materials required for photosynthesis are carbon dioxide water, and energy in the form of sunlight.
The equation is as follows:
(b) The three events in photosynthesis are:
Q3: (a) Write the reaction that occurs when glucose breaks down anaerobically in yeast. (2018)
(b) Write the mechanism by which fishes breathe in water.
(c) Name the balloon-like structures present in the lungs. List its two functions.
(d) Name the respiratory pigment and write its role in human beings.
Ans: (a)
(b) Fishes breathe with the gills by diffusion.
(c) Alveoli are the balloon-like structures:
(d) Haemoglobin is the respiratory pigment in humans. It transports a major part of oxygen and some amount of carbon dioxide through the blood.
Q4: (a) Mention any two components of blood. (2018)
(b) Trace the movement of oxygenated blood in the body.
(c) Write the function of valves present in between atria and ventricles.
(d) Write one structural difference between the composition of arteries and veins.
Ans: (а) Blood is composed of plasma and three types of cells: red blood cells, white blood cells, and platelets.
(b)
(c) The function of valves between the atria and ventricles is to:
(d)
Q5: (а) Define excretion. (2018)
(b) Name the basic filtration unit present in the kidney.
(c) Draw the excretory system in human beings and label the following organs of the excretory system that perform the following functions:
(i) form urine.
(ii) is a long tube that collects urine from the kidney.
(iii) store urine until it is passed out.
Ans:
(a) Excretion is the biological process of removal of harmful metabolic wastes from the body.
(b) Nephrons
(c) (i) Kidney, (ii) Ureter, (iii) Urinary bladder.
Excretory System of Human Beings
Q1: Diffusion is insufficient to meet the oxygen requirement of multicellular organisms like humans. State reason. (2017)
Ans: Due to the higher metabolic rate and the large volume of the body, oxygen cannot diffuse into all cells of the human body quickly as oxygen will have to travel large distances to reach each and every cell. So, diffusion is insufficient to meet the oxygen demand of multicellular organisms.
Q2: Name the vein that brings blood to the left atrium from the lungs. (2017)
Ans: The pulmonary vein carries oxygenated blood from the lungs to the left atrium of the heart.
Q3: Explain the significance of photosynthesis. Write the balanced chemical equation involved in the process. (2017)
Ans: Photosynthesis is important for a number of reasons:
(i) Food: By photosynthesis, green plants synthesize food from simple raw materials like CO2 and H2O. Thus, it sustains life on earth.
(ii) Oxygen: Oxygen released during the process of photosynthesis is needed by animals and humans for respiration. Oxygen also supports the combustion of fuels. The balanced chemical equation involved in the process of photosynthesis is given as:
Q4: Differentiate between autotrophs and heterotrophs and give one example of each. (2017)
Ans: Differences between autotrophs and heterotrophs are as follows:
Q5: Explain how the translocation of materials in phloem tissue in plants is achieved by utilizing energy. (2017)
Ans:
Q6: Draw a diagram of the human excretory system and label kidney ureters on it. (2017)
Ans: The diagram of the human excretory system is as follows:
Q7: (a) Write the reaction that occurs when glucose breaks down anaerobically in yeast. (2017)
(b) Write the mechanism by which fishes breathe in water.
(c) Name the balloon-like structures present in the lungs. List its two functions.
(d) Name the respiratory pigment and write its role in human beings.
Ans: (a) Glucose breaks down anaerobically i.e., in the absence of O2; in yeast in the following manner:
(b) Since fishes are aquatic, they take in O2 dissolved in water. They take water through their mouth, which goes to their gills, where the dissolved oxygen is taken up by the blood and transported. The CO2 is given out through the same passage.
(c) The balloon-like structures in our lungs are the alveoli.
Their functions are:
(d) The respiratory pigment is Haemoglobin.
Its role is:
Q8: (a) Name the process and explain the type of nutrition found in green plants. List the raw materials required for this process. Give the chemical equation for the mentioned process. (2017)
(b) Write three events that occur during this process.
Ans: (a) The process of nutrition in green plants is Photosynthesis. The type of nutrition is autotrophic nutrition. Autotrophic nutrition requires sunlight, chlorophyll, water, and carbon dioxide.
Plants prepare their own food in the form of glucose, which gets converted to starch. This is done using CO2 and H2O, which are fixed using energy from sunlight from the chlorophyll molecules present in green plants.
Equation -
(b) The three events involved are:
Q9: (a) Write the name of different components of the transport system in human beings and state their functions in brief. (2017)
(b) How does a blood clot form if a leak develops in the system of blood vessels?
Ans: (a) Various components of the transport system and their functions:
(b) If there is a leak in the blood vessels due to injury, then the blood platelets help plug these leaks. The platelets make the clot by forming a mesh-like structure over the leak in which other blood cells get entangled, ultimately plugging the leak.
Ans: Translocation is the process by which plants transport the products of photosynthesis from the leaves to various parts of the plant, including:
This transport occurs through the phloem, a type of vascular tissue, and involves:
Translocation is an energy-dependent process, using ATP to increase osmotic pressure, which facilitates the movement of substances in the phloem.
This allows the plant to distribute nutrients according to its needs, such as transporting stored sugars to new buds in spring.
Q2: Mention the raw materials required for photosynthesis. (2016)
Ans: Raw materials required for photosynthesis are carbon dioxide (CO2), water, light, and chloroplast.
Q3: Write three points of difference between breathing and respiration. (2016)
Ans: Differences between breathing and respiration are as follows:
Q4: Draw a flow chart to show the breakdown of glucose by various pathways. (2016)
Ans: Glucose is first broken down in the cell cytoplasm into a three-carbon molecule called pyruvate. Pyruvate is further broken down in the following ways to provide energy.
Q5: Draw a diagram of the human alimentary canal and label the following: (2016)
(i) Part in which starch digestion is initiated.
(ii) Organ in which bile is stored.
(iii) The gland that secretes digestive enzymes as well as hormones.
(iv) Part of the alimentary canal where water is reabsorbed.
(v) Part of the gut where finger-like projections are present to facilitate absorption of digested food.
Ans: (i) Mouth, (ii) Gall Bladder, (iii) Pancreas, (iv) Large Intestine, (v) Small intestine.
Q6: (a) State the form in which the following are stored : (2016)
(i) Unused carbohydrates in plants.
(ii) Energy derived from food in humans.
(b) Describe the process of nutrition in the amoeba with the help of a diagram.
Ans:
(a)
(i) As starch in fruits/storage roots tubers etc.
(ii) As glycogen.
(b) Amoeba is a unicellular eukaryotic organism that exhibits a holozoic mode of nutrition.
Five steps are involved in this mode of nutrition:
Q1: Give reason: (2015)
(l) Fine hair and mucus are present in the nasal passage.
(ii) Rings of cartilage are present in the throat.
Ans: (i) Fine hair and mucus are present in the nasal passage so that any dust particles, pathogens, etc., can be trapped in here, and only clean air will enter the lungs. This is one of the defence mechanisms of our body.
(ii) Rings of cartilage are present in the throat so that the trachea does not collapse on respiration.
Q2: Define the term parasite. Name one plant parasite and one animal parasite. Some organisms break down the food material outside the body and then absorb it. Give two examples. (2015)
Ans: Parasites are organisms that obtain nutrients from the bodies of other living organisms and harm them as a result.
(i) Plant parasite - cuscuta
(ii) Animal parasite - Tapeworm
Organisms that break down food outside the body and then absorb it are saprophytes.
Example: fungi, bacteria.
Q3: What do the following transport? (2015)
(i) Xylem
(ii) Phloem
(iii) Pulmonary vein
(iv) Vena cava
(v) Pulmonary artery
(vi) Aorta.
Ans:
Material transported by:
(i) Xylem: Water and minerals.
(ii) Phloem: Organic molecules like sucrose.
(iii) Pulmonary vein: Oxygenated blood from lungs to heart.
(iv) Vena cava: Impure and deoxygenated blood from the body to the heart.
(v) Pulmonary artery: Deoxygenated blood from the heart to the lungs.
(vi) Aorta: Oxygenated blood from the heart to body parts.
Q4: In single-celled organisms, diffusion is sufficient to meet all their requirements for food, gas exchange, or removal of waste, but it is not in the case of multicellular organisms. Explain the reason for this difference. (2015)
Ans: In the case of a single-celled organism, the entire surface of the organism is in contact with the environment, and hence, no specific organ for taking in food, exchanging gases, or removing waste may be needed. In multicellular organisms, only the cells of the skin are in direct contact with the environment. Diffusion is a very slow process, and it will take a very long time to reach all the cells of the body parts. Diffusion is insufficient to melt oxygen requirements.
Q5: State the role of the following in the human digestive system: (2015)
(a) Digestive enzymes
(b) Hydrochloric acid
(c) Villi
Ans: (a) Digestive enzymes digest the food we eat.
(b) Hydrochloric acid creates an acidic medium to facilitate the action of the enzyme pepsin.
(c) Villi increases the surface area inside the small intestine to facilitate the absorption of food.
Ans: Gastric glands are present in the wall of the stomach. They secrete gastric juices containing mucus, protein-digesting enzymes pepsin, rennin, and hydrochloric acid (HCI).
Q2: How does nutrition take place in Amoeba? How is it different in Paramoecium? (2014)
Ans: Nutrition in amoeba:
Nutrition in Paramoecium:
Q3: Why is it advisable to breathe through nose? (2014)
Ans: Breathing through the nose is advisable for several reasons:
Q4: Define transpiration. How does transpiration help in upward movement of water from roots to leaves? (2014)
Ans: Transpiration is the process through which water vapour is lost from the aerial parts of a plant, primarily via the stomata in the leaves.
This process plays a crucial role in the upward movement of water from the roots to the leaves:
During the day, when the stomata are open, the transpiration pull is the main driving force for water movement in the xylem.
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1. What are the main life processes in living organisms? | ![]() |
2. How do plants perform photosynthesis as part of their life processes? | ![]() |
3. What is the role of respiration in living organisms? | ![]() |
4. Why is excretion important for living organisms? | ![]() |
5. How do reproductive processes differ between plants and animals? | ![]() |