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

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QUESTIONS AND ANSWERS

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

    Introduction

    1. How do we tell the difference between what is alive and what is not alive?
      The distinction between living and non-living entities is based on various characteristics. Living beings display characteristics such as growth, reproduction, responsiveness to stimuli, ability to metabolize and maintain homeostasis, and the presence of organized structures such as cells.

    2. If we see a dog running, or a cow chewing cud, or a man shouting loudly on the street, we know that these are living beings. What if they were asleep? How do we know they are alive?
      Even when animals are asleep, we can infer that they are alive because of certain indicators such as breathing. The rise and fall of their chests as they breathe serve as evidence of their vitality.

    3. How do we determine if plants are alive? What characteristics do we observe?
      Plants exhibit signs of life through various characteristics. These include growth, which can be observed as an increase in size or the development of new leaves or branches. Additionally, plants carry out metabolic processes, such as photosynthesis, and respond to stimuli in their environment.

    4. Why is visible movement not enough to define life? Provide examples.
      Visible movement alone is not sufficient to define life because there are living organisms that do not exhibit visible movement but are still considered alive. For instance, some animals can breathe without observable external movement, and plants may not visibly grow for a certain period while still being alive.

    5. Is invisible molecular movement necessary for life? Explain the controversy surrounding viruses.
      Yes, invisible molecular movement is essential for life. Biologists argue that molecular movements are crucial for maintaining the organized structures of living organisms. However, viruses, which lack molecular movement until they infect a host cell, challenge the definition of life as they exhibit characteristics of both living and non-living entities. This controversy arises due to the unique nature of viruses.

    6. Why are molecular movements needed for life? How do they relate to the maintenance of living structures?
      Molecular movements are necessary for life as they facilitate the maintenance and repair of living structures. Living organisms consist of organized structures such as tissues, cells, and subcellular components. These structures are made up of molecules that constantly undergo movement to ensure proper functioning and structural integrity. Without molecular movements, the ordered nature of living structures would break down over time, compromising the organism's viability.

    7. What are the maintenance processes in living organisms?
      Living organisms employ various maintenance processes to ensure the proper functioning and preservation of their structures. These processes include molecular transport, synthesis of new molecules, repair of damaged components, removal of waste products, energy metabolism, and regulation of cellular activities to maintain homeostasis.

    What are life processes?

    1. What are life processes and why are they important?

      Life processes are the maintenance functions of living organisms that ensure their survival and well-being. These processes continue even when the organism is not engaged in any particular activity. They are important because they prevent damage and breakdown within the organism and ensure its proper functioning.


    2. Explain the process of nutrition and its significance.

      Nutrition is the process of transferring energy and raw materials from outside the body of an organism to the inside. It involves the intake, digestion, absorption, and assimilation of food. Nutrition is essential for providing the necessary energy and nutrients to carry out life processes and sustain the growth and development of the organism.


    3. What is the role of carbon-based molecules in nutrition?

      Carbon-based molecules serve as the primary food sources for organisms. These molecules provide energy and the necessary raw materials for growth and maintenance. The complexity of these carbon sources determines the type of nutritional processes different organisms can utilize.


    4. Describe the process of respiration and its significance.

      Respiration is the process of acquiring oxygen from the environment and utilizing it to break down food sources for cellular energy needs. It involves a series of chemical reactions, including oxidizing-reducing reactions, to convert food molecules into a usable form of energy. Respiration is crucial for maintaining living structures and carrying out molecular movements within the body.


    5. Explain the challenges faced by multicellular organisms in obtaining food and oxygen.

      In multicellular organisms, not all cells are in direct contact with the environment, requiring specialized tissues to facilitate the uptake of food and oxygen. Simple diffusion is insufficient to meet the requirements of all cells, necessitating a transportation system to carry these essential substances throughout the organism's body.


    6. What is the role of a transportation system in multicellular organisms?

      The transportation system in multicellular organisms is responsible for carrying food and oxygen from one place to another within the body. It ensures that all cells receive the necessary nutrients and oxygen for their functioning and survival.


    7. Define excretion and its importance.

      Excretion is the process of removing waste by-products produced during cellular metabolism. These waste substances are not useful for the cells and may even be harmful. Excretion plays a vital role in maintaining the internal environment of the organism by eliminating waste materials and maintaining proper homeostasis.


    8. Explain the relationship between transportation system and excretion in multicellular organisms.

      In multicellular organisms, the transportation system not only transports food and oxygen but also carries waste products away from cells to specialized excretory tissues. This ensures efficient removal of waste materials from the body and their proper disposal outside.


    Nutrition

    1. What is the main source of energy and materials for living things?
      The main source of energy and materials for living things is food.

    2. How do autotrophs fulfill their energy and carbon requirements?

      Autotrophs fulfill their energy and carbon requirements through the process of photosynthesis. In this process, carbon dioxide (CO2) and water (H2O) are converted into carbohydrates in the presence of sunlight and chlorophyll.


    3. Name two types of organisms based on their method of obtaining food.

      Two types of organisms based on their method of obtaining food are autotrophs and heterotrophs.


    4. What is the process by which autotrophs convert external substances into stored forms of energy?

      The process by which autotrophs convert external substances into stored forms of energy is photosynthesis.


    5. What are the raw materials required for photosynthesis in autotrophic organisms?

      The raw materials required for photosynthesis in autotrophic organisms are carbon dioxide (CO2) and water (H2O).


    6. How are carbohydrates utilized in autotrophic organisms?

      Carbohydrates produced through photosynthesis are utilized in autotrophic organisms to provide energy for various metabolic activities.


    7. What happens to excess carbohydrates that are not immediately used by the plant?

      Excess carbohydrates that are not immediately used by the plant are stored in the form of starch, serving as an internal energy reserve.


    8. How is energy stored in our body in the form of glycogen?

      In our body, energy is stored in the form of glycogen, a complex carbohydrate, which serves as a reserve source of energy to be used as and when required.


    9. Define nutrition.

      Nutrition refers to the process by which living organisms obtain energy and materials from the food they consume to support their growth, development, and various physiological functions.


    10. What is the difference between autotrophs and heterotrophs?

      Autotrophs are organisms that can synthesize their own food using sunlight and inorganic substances, while heterotrophs are organisms that rely on consuming other organisms for their food.


    11. Explain the process of photosynthesis in autotrophic organisms.

      Photosynthesis is the process in which autotrophic organisms convert carbon dioxide and water into carbohydrates using sunlight and chlorophyll as the catalysts. The equation for photosynthesis is: 6CO2 + 6H2O + sunlight → C6H12O6 + 6O2.


    12. What are the raw materials required for photosynthesis?

      The raw materials required for photosynthesis are carbon dioxide (CO2) and water (H2O).


    13. How do autotrophs utilize carbohydrates for energy?

      Autotrophs utilize carbohydrates as a source of energy through the process of cellular respiration. During cellular respiration, carbohydrates are broken down in the presence of oxygen to release energy in the form of ATP (adenosine triphosphate).


    14. What is the purpose of storing excess carbohydrates in the form of starch or glycogen?

      The purpose of storing excess carbohydrates in the form of starch or glycogen is to serve as an energy reserve that can be utilized by the organism when needed. It provides a readily available source of energy during times of scarcity or increased energy requirements.


    15. Define glycogen.

      Glycogen is a complex carbohydrate that serves as the primary storage form of glucose in animals and humans. It is stored in the liver and muscles and can be broken down into glucose to provide energy during periods of fasting or physical activity.


    16. How do heterotrophic organisms obtain their food?

      Heterotrophic organisms obtain their food by consuming other organisms or organic matter. They rely on ingesting and digesting complex substances, such as carbohydrates, proteins, and fats, to extract the necessary nutrients for their energy and growth.


    17. What are enzymes and how do they help in the breakdown of complex substances?

      Enzymes are bio-catalysts that facilitate chemical reactions in living organisms. They help in the breakdown of complex substances, such as carbohydrates, proteins, and fats, into simpler forms that can be absorbed and utilized by the organism for various physiological processes.


    18. Explain the interdependence between autotrophs and heterotrophs in terms of nutrition.

      Autotrophs and heterotrophs are interdependent in terms of nutrition. Autotrophs, through photosynthesis, produce oxygen and organic compounds (carbohydrates) that serve as a food source for heterotrophs. Heterotrophs, in turn, consume autotrophs or other heterotrophs for their energy and nutrient requirements. This interdependence ensures the cycling of energy and nutrients in ecosystems.


    Autotrophic Nutrition

    1. Define photosynthesis and explain its significance in autotrophic nutrition.

      Photosynthesis is the process by which autotrophs convert carbon dioxide and water into carbohydrates using sunlight and chlorophyll. It is significant in autotrophic nutrition as it provides autotrophs with the necessary energy to carry out metabolic processes and synthesize organic compounds.


    2. What are the requirements for photosynthesis in autotrophic organisms?

      The requirements for photosynthesis in autotrophic organisms are carbon dioxide (CO2), water (H2O), sunlight, and chlorophyll.


    3. Describe the process of photosynthesis, including the steps involved.

      The process of photosynthesis involves the following steps:

      • Absorption of light energy by chlorophyll.
      • Conversion of light energy to chemical energy and splitting of water molecules into hydrogen and oxygen.
      • Reduction of carbon dioxide to carbohydrates.

    4. Provide the balanced chemical equation for photosynthesis.

      The balanced chemical equation for photosynthesis is:

      6CO2 + 12H2O + light energy → C6H12O6 + 6O2


    5. Why is chlorophyll essential for photosynthesis?

      Chlorophyll is essential for photosynthesis because it absorbs light energy from the sun, which is necessary for the conversion of carbon dioxide and water into carbohydrates.


    6. Explain the role of sunlight in the process of photosynthesis.

      Sunlight plays a crucial role in photosynthesis as it provides the energy required to convert carbon dioxide and water into carbohydrates. The absorbed sunlight is converted into chemical energy, which is used to drive the synthesis of carbohydrates.


    7. What happens to the carbohydrates produced during photosynthesis?

      The carbohydrates produced during photosynthesis are utilized by the plant for providing energy to carry out various metabolic processes. Any excess carbohydrates that are not immediately used are stored in the form of starch, serving as an internal energy reserve for the plant.


    8. Compare the storage of energy in autotrophs and humans.

      In autotrophs, such as plants, the energy produced during photosynthesis is stored in the form of carbohydrates, mainly starch. In humans, energy derived from food is stored in the form of glycogen.


    9. Discuss the importance of starch as an energy reserve in plants.

      Starch serves as an important energy reserve in plants. It allows plants to store excess carbohydrates produced during photosynthesis in a compact and readily available form. Starch can be broken down and used as an energy source during periods when photosynthesis is not actively occurring, such as during the night or in winter.


    10. Explain the concept of glycogen as an energy storage compound in humans.

      Glycogen is an energy storage compound in humans. It is a polysaccharide made up of glucose molecules. Glycogen is primarily stored in the liver and muscles. When energy is needed, glycogen can be broken down into glucose, which can be used as a fuel source by the body.


    11. How do desert plants adapt their photosynthetic process to their environment?

      Desert plants have adapted their photosynthetic process to their environment by taking up carbon dioxide at night and storing it as an intermediate compound. This intermediate compound is then utilized during the day when energy is available from sunlight. This adaptation allows desert plants to conserve water by reducing water loss through open stomata during the hot daytime conditions.


    12. Describe the events that occur during the process of photosynthesis.

      During the process of photosynthesis, the following events occur:

      1. Absorption of light energy by chlorophyll
      2. Conversion of light energy to chemical energy and splitting of water molecules into hydrogen and oxygen
      3. Reduction of carbon dioxide to carbohydrates

    13. Explain the conversion of light energy to chemical energy in photosynthesis.

      During photosynthesis, light energy is absorbed by chlorophyll. This absorbed light energy is converted into chemical energy through a series of complex biochemical reactions. The chemical energy is stored in the form of carbohydrates, which can be utilized by the plant for various metabolic processes.


    14. Discuss the reduction of carbon dioxide to carbohydrates in photosynthesis.

      In photosynthesis, carbon dioxide is reduced to carbohydrates through a series of enzymatic reactions. The energy from sunlight is utilized to convert carbon dioxide into high-energy molecules, such as glucose. This reduction process involves the transfer of electrons and hydrogen ions, resulting in the formation of carbohydrates.


    Activities 5.1 and 5.2

    1. Define photosynthesis and explain its significance in plants.

      Photosynthesis is the process by which green plants, algae, and some bacteria convert sunlight, carbon dioxide, and water into glucose and oxygen. It is a vital process as it provides plants with the energy they need to grow and survive. Additionally, photosynthesis plays a crucial role in maintaining the balance of oxygen and carbon dioxide in the atmosphere.


    2. What is the purpose of keeping the potted plant in a dark room for three days before exposing it to sunlight?

      The purpose of keeping the potted plant in a dark room for three days is to ensure that all the starch present in the leaves gets used up. This allows for a clear investigation of the presence of starch in different areas of the leaf after exposure to sunlight.


    3. Describe the procedure followed in the activity to investigate the presence of starch in different areas of the leaf.

      The procedure followed in the activity is as follows:

      1. Take a potted plant with variegated leaves.
      2. Keep the plant in a dark room for three days.
      3. Expose the plant to sunlight for about six hours.
      4. Pluck a leaf from the plant and mark the green areas on a sheet of paper.
      5. Dip the leaf in boiling water and then immerse it in alcohol.
      6. Heat the alcohol solution in a water-bath until it begins to boil.
      7. Observe the colour of the leaf and compare it with the tracing of the leaf done in the beginning.

    4. Explain the role of boiling water and alcohol in the activity.

      The boiling water is used to denature the enzymes present in the leaf. This helps in degrading any starch present into simpler sugars. The alcohol is used to remove the chlorophyll pigment from the leaf, making it easier to observe any remaining starch.


    5. What is the significance of heating the alcohol solution in a water-bath during the activity?

      Heating the alcohol solution in a water-bath helps in accelerating the extraction of pigments from the leaf and the breakdown of chlorophyll. It also aids in dissolving any remaining starch, making it easier to observe the absence or presence of starch in different areas of the leaf.


    6. What changes occur to the colour of the leaf and the solution when it is immersed in alcohol?

      When the leaf is immersed in alcohol, the chlorophyll pigment in the leaf dissolves and is extracted into the alcohol solution. This results in the leaf losing its green colour and becoming pale. The alcohol solution, on the other hand, may turn green as it absorbs the chlorophyll pigment.


    7. What is the purpose of dipping the leaf in a dilute solution of iodine? Explain the reaction that takes place.

      The purpose of dipping the leaf in a dilute solution of iodine is to test for the presence of starch. Iodine reacts with starch and forms a dark blue-black colour complex. This reaction serves as an indicator for the presence of starch in different areas of the leaf.


    8. Compare the colour of the leaf after rinsing off the iodine solution with the tracing of the leaf done in the beginning. What inference can be drawn from this comparison?

      After rinsing off the iodine solution, the areas of the leaf that contain starch will appear dark blue-black, while the areas without starch will retain their original color. By comparing the colour of the leaf with the initial tracing, one can infer the distribution of starch in different areas of the leaf.


    9. Based on the observations, explain the presence of starch in various areas of the leaf.

      Based on the observations, areas of the leaf that turn dark blue-black after the iodine test indicate the presence of starch. These areas are typically the green parts of the leaf, which have been exposed to sunlight and have undergone photosynthesis, producing glucose and converting it into starch for storage.

    10. Define stomata and explain their role in gaseous exchange during photosynthesis. Provide an example.

      Stomata are tiny pores present on the surface of leaves, stems, and roots of plants. They play a crucial role in the exchange of gases, particularly carbon dioxide and oxygen, during the process of photosynthesis. Stomata allow carbon dioxide to enter the plant for photosynthesis and facilitate the release of oxygen as a byproduct. An example of stomatal exchange is the intake of carbon dioxide by plants during daylight hours for the synthesis of glucose through photosynthesis.


    11. Describe the process of opening and closing of stomata. Provide a chemical equation for the reaction involved in the swelling and shrinking of guard cells.

      The opening and closing of stomata is controlled by the movement of specialized cells called guard cells. When water flows into the guard cells, they swell and cause the stomatal pore to open, allowing gas exchange. Conversely, when water is lost from the guard cells, they shrink, leading to the closure of the stomatal pore. The reaction involved in the swelling and shrinking of guard cells can be represented as follows:

      Swelling of guard cells: H2O + Guard Cells → Swollen Guard Cells

      Shrinking of guard cells: Guard Cells → Shrunken Guard Cells + H2O


    12. What is the function of guard cells in stomatal regulation? Explain with reasoning.

      The primary function of guard cells is to regulate the opening and closing of stomata. Guard cells have the ability to swell and shrink in response to changes in water content. When water flows into the guard cells, they swell, causing the stomatal pore to open and enabling gaseous exchange. Conversely, when water is lost from the guard cells, they shrink, leading to the closure of stomata and prevention of excessive water loss. This mechanism helps plants balance their need for carbon dioxide uptake for photosynthesis while minimizing water loss through transpiration.


    13. Explain why plants close their stomata when they do not need carbon dioxide for photosynthesis.

      Plants close their stomata when they do not need carbon dioxide for photosynthesis to prevent excessive water loss through transpiration. Closing stomata helps conserve water and maintain proper hydration within the plant. Additionally, it reduces the risk of desiccation in dry environmental conditions. By regulating the opening and closing of stomata, plants can optimize their gas exchange, conserving water resources while still ensuring an adequate supply of carbon dioxide for photosynthesis when needed.


    14. Discuss the significance of gaseous exchange across the surface of stems, roots, and leaves in plants.

      Gaseous exchange across the surface of stems, roots, and leaves is of utmost significance in plants. It allows for the intake of carbon dioxide needed for photosynthesis and the release of oxygen as a byproduct. This exchange ensures the supply of oxygen to plant cells and facilitates cellular respiration. Additionally, gaseous exchange helps regulate the water vapor content within the plant, as well as the exchange of other gases involved in metabolic processes. Overall, this exchange is crucial for maintaining plant health, growth, and energy production.


    15. Explain how excessive water loss is prevented through stomatal regulation. Provide an example.

      Excessive water loss through transpiration is prevented through stomatal regulation. When plants close their stomata, the rate of transpiration decreases significantly, conserving water resources within the plant. This is particularly important in arid or dry environments where water availability is limited. An example of stomatal regulation for water conservation is the behavior of succulent plants such as cacti. These plants have specialized adaptations, including reduced and sunken stomata, which help minimize water loss through transpiration.


    16. Describe the structure and location of stomata on the plant surface. Support your answer with a labeled diagram.

      Stomata are present on the surfaces of leaves, stems, and roots. They consist of two specialized cells called guard cells that surround a central opening or pore. The structure of stomata allows for their opening and closing in response to changes in water content. The diagram below illustrates the structure and location of stomata on the plant surface:

      Stomata Diagram

    17. Discuss the relationship between stomata and the process of photosynthesis in plants.

      Stomata play a vital role in the process of photosynthesis in plants. They allow for the entry of carbon dioxide, which is an essential raw material for photosynthesis. Carbon dioxide enters the plant through open stomata and diffuses into the chloroplasts of leaf cells, where it participates in the Calvin cycle to produce glucose and other organic compounds. The oxygen produced as a byproduct of photosynthesis is released through the stomata. Hence, stomata facilitate the exchange of gases necessary for photosynthesis, enabling plants to produce energy-rich organic molecules.



    18. Explain the role of stomata in maintaining the balance between carbon dioxide uptake and water loss in plants.

      Stomata play a crucial role in maintaining the balance between carbon dioxide uptake and water loss in plants. By regulating the opening and closing of stomata, plants can control the exchange of gases with the external environment. When carbon dioxide is needed for photosynthesis, stomata open, allowing its entry while enabling the release of oxygen. However, stomata also allow for water vapor to escape through transpiration. To prevent excessive water loss, plants close their stomata when the demand for carbon dioxide is low, thus minimizing transpirational water loss. This dynamic regulation helps plants optimize their carbon dioxide uptake while conserving water resources.


    19. Compare and contrast the opening and closing mechanisms of stomata in response to water availability.

      The opening and closing mechanisms of stomata in response to water availability involve different cellular processes. When water availability is high, guard cells absorb water through osmosis, causing them to swell and bend apart, which leads to the opening of stomatal pores. On the other hand, when water availability is low, guard cells lose water, causing them to shrink and close the stomatal pores. Both processes are regulated by changes in turgor pressure within the guard cells. While the opening of stomata is driven by increased turgor pressure, the closing of stomata is a result of decreased turgor pressure. These mechanisms ensure efficient gas exchange while preventing excessive water loss through transpiration.

    20. Define photosynthesis and explain its significance in plants.

      Photosynthesis is the process by which green plants, algae, and some bacteria convert light energy from the sun into chemical energy in the form of glucose. It occurs in the chloroplasts of plant cells and is essential for the production of oxygen and organic compounds, which serve as a source of energy for all living organisms. The overall equation for photosynthesis is:

      6CO2 + 6H2O + light energy → C6H12O6 + 6O2


    21. Describe the experimental setup used to investigate the role of sunlight in photosynthesis.

      To investigate the role of sunlight in photosynthesis, the following experimental setup can be used:

      1. Take two healthy potted plants of the same size.
      2. Keep both plants in a dark room for three days to deplete their stored starch.
      3. Place one plant under sunlight and the other plant in a dark room as a control.
      4. Expose both plants to light for a specific duration, such as two hours.
      5. After the exposure, pluck a leaf from each plant and perform a starch test to determine the presence of starch.
      6. Compare the amount of starch present in the leaves of the sunlit plant and the control plant.

    22. What is the purpose of placing potassium hydroxide near one of the plants in the experiment?

      The purpose of placing potassium hydroxide near one of the plants in the experiment is to absorb carbon dioxide (CO2). Potassium hydroxide acts as a carbon dioxide absorbent, creating a carbon dioxide-free environment around the plant. This allows the investigation of the role of carbon dioxide in photosynthesis by comparing the results between the plant exposed to sunlight and the plant placed near potassium hydroxide.


    23. Why is it important to keep the setup airtight using vaseline?

      It is important to keep the setup airtight using vaseline to ensure that there is no exchange of gases between the environment and the experimental setup. Airtight sealing with vaseline prevents the entry of atmospheric carbon dioxide into the setup and ensures that the observed changes in the plants are solely due to the influence of sunlight and absence/presence of carbon dioxide.


    24. What is the role of water in photosynthesis? How is it obtained by terrestrial plants?

      Water plays a crucial role in photosynthesis as it serves as a source of hydrogen (H) atoms for the reduction of carbon dioxide (CO2) during the light-independent reactions. Terrestrial plants obtain water from the soil through their root systems. The roots absorb water through osmosis and transport it to the leaves through the xylem vessels. Water uptake by roots is facilitated by the process of transpiration, where water is drawn up from the roots to the leaves due to evaporation at the leaf surface.


    25. Discuss the importance of nitrogen in the synthesis of proteins and other compounds in plants. How is nitrogen acquired by plants?

      Nitrogen is an essential element required for the synthesis of proteins and other compounds in plants. Proteins are composed of amino acids, and nitrogen is a crucial component of these amino acids. Nitrogen is also essential for the formation of nucleic acids and chlorophyll.

      Plants acquire nitrogen by absorbing it from the soil in the form of inorganic nitrates or nitrites. Some plants can also take up nitrogen in the form of organic compounds, such as amino acids and ammonium ions, which are produced by nitrogen-fixing bacteria. These bacteria convert atmospheric nitrogen (N2) into organic nitrogen compounds through a process called nitrogen fixation.


    26. Explain the process of starch testing to determine the presence of photosynthesis in plants.

      Starch testing is a common method used to determine the presence of photosynthesis in plants. The process involves the following steps:

      1. Pluck a leaf from the plant.
      2. Boil the leaf in water to soften it and denature enzymes.
      3. Place the boiled leaf in a test tube and add a few drops of iodine solution.
      4. Observe the color change in the leaf.
      5. If the leaf turns blue-black, it indicates the presence of starch, which suggests that photosynthesis has occurred. If the leaf remains brown, it indicates the absence of starch and a lack of photosynthesis.

    27. Do both leaves from the two plants show the same amount of starch after exposure to sunlight? Explain your answer.

      No, both leaves from the two plants do not show the same amount of starch after exposure to sunlight. The leaf from the plant exposed to sunlight is expected to show the presence of starch, indicating that photosynthesis has occurred in the presence of light. However, the leaf from the plant placed in the dark room (control) is expected to show the absence of starch, indicating that photosynthesis did not occur due to the absence of light.


    28. Based on the activities performed, can we conclude that sunlight is essential for photosynthesis? Justify your answer.

      Yes, based on the activities performed, we can conclude that sunlight is essential for photosynthesis. The presence of starch in the leaf exposed to sunlight indicates that photosynthesis occurred in the presence of light energy. In contrast, the absence of starch in the leaf placed in the dark room (control) indicates that photosynthesis did not occur in the absence of light energy. This demonstrates the vital role of sunlight in driving the process of photosynthesis.


    29. Design an experiment to demonstrate the importance of sunlight in photosynthesis. Provide a step-by-step procedure.

      An experiment to demonstrate the importance of sunlight in photosynthesis can be designed using the following procedure:

      1. Take two identical potted plants of the same species.
      2. Keep one plant in a well-lit area exposed to sunlight (Plant A).
      3. Place the other plant in a dark room without any access to light (Plant B).
      4. Ensure both plants receive the same amount of water and other necessary resources.
      5. Observe the growth and overall health of both plants over a period of time, recording any visible differences.
      6. Analyze the differences observed in terms of plant height, leaf color, and overall vitality.
      7. Based on the comparison, conclude whether sunlight is essential for photosynthesis and plant growth.

    30. List other raw materials required by autotrophs for building their bodies. How are these materials obtained?

      Autotrophs require various raw materials for building their bodies, including:

      • Carbon dioxide (CO2) - Obtained from the atmosphere through stomata in leaves.
      • Water (H2O) - Absorbed from the soil through the root system.
      • Nitrogen (N) - Acquired from the soil in the form of inorganic nitrates or nitrites, or as organic compounds produced by nitrogen-fixing bacteria.
      • Phosphorus (P), iron (Fe), magnesium (Mg), and other minerals - Absorbed from the soil through the root system.



    31. Explain the role of inorganic nitrates and organic compounds in the uptake of nitrogen by plants.

      Inorganic nitrates (NO3-) and nitrites (NO2-) play a crucial role in the uptake of nitrogen by plants. The roots of plants absorb these inorganic compounds from the soil and utilize them in the synthesis of proteins, nucleic acids, and other nitrogen-containing compounds.

      On the other hand, organic compounds that have been prepared by bacteria from atmospheric nitrogen, such as ammonia (NH3) or amino acids, can also serve as a source of nitrogen for plants. These organic compounds are produced through a process called nitrogen fixation, performed by nitrogen-fixing bacteria in symbiotic relationships with certain plants or in the soil. Plants can absorb these organic nitrogen compounds and utilize them for growth and development.


    32. Discuss the significance of photosynthesis in the overall energy balance of ecosystems.

      Photosynthesis plays a crucial role in the overall energy balance of ecosystems. It is the primary process through which solar energy is converted into chemical energy in the form of glucose and other organic compounds. These organic compounds serve as a source of energy for all living organisms, including both autotrophs and heterotrophs.

      Autotrophs, such as plants and algae, perform photosynthesis and produce organic matter, which forms the base of the food chain. Heterotrophs, including animals and other organisms, rely on the consumption of these organic compounds for their energy needs. Thus, photosynthesis acts as the ultimate source of energy for sustaining life and maintaining the energy flow within ecosystems.


    33. Provide examples of other factors that can affect the rate of photosynthesis in plants.

      Several factors can affect the rate of photosynthesis in plants. Some examples include:

      • Light intensity - Higher light intensity generally leads to increased photosynthetic activity.
      • Temperature - Optimum temperature levels promote efficient photosynthesis, while extreme temperatures can negatively impact the process.
      • Carbon dioxide concentration - Adequate availability of carbon dioxide is necessary for optimal photosynthesis.
      • Availability of water - Insufficient water supply can limit photosynthetic activity.
      • Nutrient availability - The presence of essential nutrients, such as nitrogen, phosphorus, and magnesium, is crucial for proper photosynthetic function.

    34. Write the balanced chemical equation for photosynthesis, indicating the reactants and products involved.

      The balanced chemical equation for photosynthesis is:

      6CO2 + 6H2O + light energy → C6H12O6 + 6O2

      The reactants are carbon dioxide (CO2) and water (H2O), and the products are glucose (C6H12O6) and oxygen (O2).


    Heterotrophic Nutrition

    1. Define heterotrophic nutrition and provide examples of organisms that exhibit this type of nutrition.

      Heterotrophic nutrition is a mode of nutrition in which organisms obtain organic compounds and nutrients from external sources, as they are unable to synthesize their own food. Examples of organisms that exhibit heterotrophic nutrition include:

      • Fungi like bread moulds, yeast, and mushrooms.
      • Parasitic organisms such as cuscuta (amar-bel), ticks, lice, leeches, and tape-worms.

    2. Describe the different strategies used by organisms for obtaining and utilizing food.

      Organisms employ various strategies for obtaining and utilizing food based on their environmental conditions and body design. Some strategies include:

      • Break-down of food material outside the body and subsequent absorption, as seen in fungi like bread moulds, yeast, and mushrooms.
      • Intake of whole food material and subsequent internal break-down, observed in various organisms with suitable body design and functioning.
      • Parasitic nutrition, where organisms derive nutrition from plants or animals without killing them, as exemplified by cuscuta (amar-bel), ticks, lice, leeches, and tape-worms.

    3. Provide a brief explanation of how heterotrophic organisms obtain and utilize their food.

      Heterotrophic organisms obtain and utilize their food through different mechanisms:

      • Fungi like bread moulds, yeast, and mushrooms break down food material outside their bodies using enzymes. They then absorb the digested organic compounds.
      • Other organisms take in whole food material and internally break it down with the help of digestive enzymes and other biochemical processes.
      • Parasitic organisms derive nutrition from plants or animals without killing them. They have specialized adaptations to extract nutrients from their hosts without causing fatal harm.

    4. Explain the concept of parasitic nutrition and provide examples of organisms that exhibit this type of nutrition.

      Parasitic nutrition is a type of heterotrophic nutrition where organisms derive nutrition from other organisms without killing them. Examples of organisms that exhibit parasitic nutrition include cuscuta (amar-bel), ticks, lice, leeches, and tape-worms. These organisms have adaptations that allow them to extract nutrients from their hosts while ensuring their own survival.


    5. Describe the nutritive strategies employed by cuscuta (amar-bel), ticks, lice, leeches, and tape-worms.

      Cuscuta (amar-bel), ticks, lice, leeches, and tape-worms employ various nutritive strategies to obtain nutrients without killing their hosts:

      • Cuscuta (amar-bel) is a parasitic plant that attaches itself to the host plant and absorbs nutrients through specialized structures called haustoria.
      • Ticks, lice, and leeches feed on the blood of their hosts, using adaptations like mouthparts or suckers to obtain nutrients.
      • Tape-worms live in the intestines of animals and absorb nutrients directly from the host's digested food through their specialized structures.

    6. Explain the importance of body design and functioning in determining the type of food and mode of nutrition in organisms.

      The body design and functioning of organisms play a crucial role in determining the type of food they can consume and the mode of nutrition they exhibit. The adaptations and structures present in an organism determine its ability to break down and utilize different types of food materials. For example, the digestive system of an organism dictates whether it can externally break down food material or needs to ingest it whole. Similarly, specific adaptations allow parasites to derive nutrition from their hosts without causing fatal harm. The interplay between body design and functioning enables organisms to optimize their nutrition based on their specific ecological niche.

    How do Organisms obtain their Nutrition?

    1. Define nutrition.

      Nutrition refers to the process by which organisms obtain and utilize food for growth, energy, and maintenance of bodily functions.


    2. Describe the different ways in which organisms obtain their nutrition.

      Organisms obtain their nutrition through various methods:

      • In single-celled organisms, such as Amoeba, food is taken in by the entire surface through processes like endocytosis.
      • In more complex organisms, different parts become specialized to perform specific functions in the digestive system.
      • Animals can be classified based on their feeding mechanisms, such as herbivores, carnivores, and omnivores.
      • Plants produce their own food through the process of photosynthesis, utilizing sunlight, carbon dioxide, and water.

    3. Explain the process of nutrition in Amoeba.

      In Amoeba, the process of nutrition involves the following steps:

      1. The amoeba extends temporary finger-like extensions of the cell surface called pseudopodia.
      2. These pseudopodia surround the food particle, forming a food vacuole.
      3. Inside the food vacuole, complex substances are broken down into simpler ones through the process of digestion.
      4. The digested nutrients then diffuse into the cytoplasm, where they are utilized for various metabolic activities.
      5. Any undigested material is moved to the surface of the cell and expelled from the organism.


      Image depicting the process in Amoeba
      Nutrition in Amoeba


    4. Explain the process of nutrition in Paramoecium.

      In Paramoecium, the process of nutrition involves the following steps:

      1. The cell of Paramoecium has a definite shape with a specific spot for food intake.
      2. Cilia, which are hair-like structures covering the entire surface of the cell, move the food towards this spot.
      3. The food is engulfed at the specific spot, forming a food vacuole.
      4. Inside the food vacuole, digestion takes place, converting complex substances into simpler ones.
      5. The digested nutrients diffuse into the cytoplasm for utilization.
      6. Any undigested material is expelled from the organism.


    5. Explain how the digestive system differs in single-celled organisms and more complex organisms.

      The digestive system differs in single-celled organisms and more complex organisms in the following ways:

      • In single-celled organisms like Amoeba, the entire cell surface is involved in the process of food intake.
      • Complex substances are broken down inside food vacuoles, and the digested nutrients diffuse into the cytoplasm.
      • Any undigested material is expelled from the cell.
      • In more complex organisms, different parts of the body become specialized for specific functions in the digestive system.
      • These specialized parts include the mouth, esophagus, stomach, intestines, and accessory organs like liver and pancreas.
      • Digestion occurs in specific compartments of the digestive system, allowing for more efficient breakdown of food and absorption of nutrients.

    6. Explain the significance of cilia in Paramoecium's nutrition process.

      Cilia play a significant role in Paramoecium's nutrition process. Cilia are hair-like structures that cover the entire surface of the Paramoecium cell. They help in:

      • Moving the food particles towards the specific spot where food intake occurs.
      • Creating currents in the surrounding water, facilitating the capture and transport of food.
      • Increasing the efficiency of food intake and digestion in Paramoecium.

    Nutrition in Human Beings

    1. Define the alimentary canal and explain its function in the human body.

      The alimentary canal is a long tube extending from the mouth to the anus. It is responsible for the process of digestion and absorption of food in the human body. The different regions of the alimentary canal are specialized to perform various functions, such as mechanical and chemical digestion, nutrient absorption, and waste elimination.


    2. Describe the process of digestion in the human body.

      The process of digestion in the human body involves the following steps:

      1. Ingestion: The intake of food through the mouth.
      2. Chewing and Swallowing: Mechanical breakdown of food by teeth and the movement of food into the esophagus.
      3. Digestion in the Stomach: Chemical breakdown of food with the help of gastric juices.
      4. Digestion in the Small Intestine: Further breakdown of food using enzymes from the pancreas and intestinal wall.
      5. Absorption: The absorption of digested nutrients into the bloodstream through the walls of the small intestine.
      6. Formation of Feces: Removal of undigested waste materials from the body through the rectum and anus.

    3. Explain the steps involved in Activity 5.3 and interpret the observations.

      In Activity 5.3, the steps involved are as follows:

      1. 1 mL of starch solution (1%) is taken in two test tubes (A and B).
      2. 1 mL of saliva is added to test tube A, while test tube B is left undisturbed.
      3. Both test tubes are left undisturbed for 20-30 minutes.
      4. A few drops of dilute iodine solution are added to the test tubes.

      The color change is observed in test tube A, indicating the presence of starch. Test tube B remains unchanged, indicating the absence of starch. This indicates that saliva, which contains an enzyme called amylase, acts on starch and breaks it down into simpler substances.

    4. Explain the significance of saliva in the digestion process.

      Saliva plays a crucial role in the digestion process. It contains an enzyme called amylase, which begins the digestion of starch in the mouth. Amylase breaks down starch into smaller molecules, such as maltose, by hydrolysis. This initial breakdown of starch in the mouth allows for easier digestion and absorption of nutrients in the later stages of the digestive system.

    5. Define digestion and explain its importance in the human body.

      Digestion is the process by which food is broken down into smaller, simpler molecules that can be absorbed and utilized by the body. It involves the mechanical and chemical breakdown of food components. Digestion is important in the human body because:

      • It allows nutrients to be extracted from food and utilized for energy production, growth, and repair of body tissues.
      • It breaks down complex molecules into simpler forms that can be easily absorbed by the body.
      • It helps in the elimination of waste materials from the body.
      • It plays a crucial role in maintaining overall health and well-being.

    6. Explain the role of teeth in the digestive process.

      Teeth play a crucial role in the digestive process. Their main functions are:

      • Mechanical breakdown of food: Teeth help in crushing and grinding food, increasing its surface area for better chemical digestion.
      • Initiation of digestion: Chewing stimulates the secretion of saliva, which contains digestive enzymes like salivary amylase. These enzymes start the breakdown of complex molecules, such as starch, into simpler forms.
      • Formation of a bolus: Chewing and mixing food with saliva helps in forming a moist, cohesive mass called a bolus, which is easier to swallow and digest.


    7. What is saliva, and what is its role in the digestion of food?

      Saliva is a fluid secreted by the salivary glands in the mouth. It contains various components, including water, mucus, electrolytes, and enzymes. Saliva's role in the digestion of food is as follows:

      • Moistening of food: Saliva moistens food particles, making it easier to chew and swallow.
      • Initiation of starch digestion: Saliva contains an enzyme called salivary amylase, which breaks down starch into simpler sugars like maltose.
      • Facilitation of swallowing: The lubricating properties of saliva aid in the smooth movement of food down the esophagus.

    8. Write the chemical reaction catalyzed by salivary amylase in the digestion of starch.

      The chemical reaction catalyzed by salivary amylase in the digestion of starch can be represented as:

      Starch + Salivary Amylase → Maltose


    9. Explain the process of peristalsis in the digestive system.

      Peristalsis is a rhythmic contraction and relaxation of the muscles in the digestive tract that helps in moving food along the canal. The process of peristalsis in the digestive system involves:

      • Rhythmic contractions: The circular muscles behind the food contract, while those in front relax, creating a wave-like motion.
      • Food propulsion: The coordinated muscular contractions push the food forward through the digestive tube.
      • Continuous movement: Peristalsis occurs throughout the entire digestive tract, ensuring the efficient transportation and processing of food.

    10. Describe the function of the stomach in the digestive process.

      The stomach plays a vital role in the digestive process. Its functions include:

      • Storage of food: The stomach expands to accommodate food after it enters from the esophagus.
      • Mixing and churning: The muscular walls of the stomach contract and relax, mixing the food with digestive juices and breaking it down further into a semi-liquid mixture called chyme.
      • Secretion of gastric juices: The stomach lining secretes gastric juices containing enzymes and hydrochloric acid, which aid in the breakdown of proteins and kill bacteria.
      • Partial digestion: The stomach begins the digestion of proteins through the action of the enzyme pepsin.

    11. Define gastric glands and describe their role in stomach digestion.

      Gastric glands are specialized glands present in the wall of the stomach. They release hydrochloric acid, pepsin (a protein-digesting enzyme), and mucus. The role of gastric glands in stomach digestion is to:

      • Release hydrochloric acid to create an acidic environment that aids in the action of pepsin.
      • Release pepsin for the breakdown of proteins.
      • Secrete mucus to protect the inner lining of the stomach from the corrosive effects of the acid and enzymes.
      Gastric Glands

    12. What additional function does hydrochloric acid serve in the stomach?

      In addition to aiding the action of pepsin, hydrochloric acid in the stomach has the following functions:

      • Kills harmful microorganisms that enter the body through food or drink.
      • Provides an optimal acidic pH for the conversion of pepsinogen (inactive form) into pepsin (active form).

    13. How does mucus protect the inner lining of the stomach?

      Mucus secreted by the gastric glands acts as a protective barrier for the inner lining of the stomach. It:

      • Covers and coats the stomach walls, forming a physical barrier against the corrosive effects of hydrochloric acid and pepsin.
      • Prevents the acid and enzymes from directly contacting the stomach lining, thus preventing damage and ulcer formation.

    14. Can the condition of 'acidity' experienced by adults be related to the gastric glands' function and acid production?

      Yes, the condition of 'acidity' experienced by adults can be related to the function and acid production of the gastric glands. 'Acidity' refers to the excessive production of hydrochloric acid in the stomach. When there is an imbalance in the secretion of acid or a disruption in the protective mechanisms of the stomach, it can lead to the backflow of acid into the esophagus, causing symptoms such as heartburn, acid reflux, and discomfort. This condition is commonly known as acid reflux or gastroesophageal reflux disease (GERD). It is important to maintain a balance of acid production and protective measures to prevent such conditions.

    15. Explain the role of the sphincter muscle in regulating the exit of food from the stomach.

      The sphincter muscle, located at the lower end of the stomach, plays a crucial role in regulating the exit of food from the stomach into the small intestine. It functions as a valve that:

      • Controls the flow of food by releasing it in small amounts into the small intestine.
      • Prevents the backflow of partially digested food from the small intestine back into the stomach.
      Sphincter Muscle

    16. Describe the structural adaptation of the small intestine and its relationship with the diet of herbivores and carnivores.

      The small intestine, the longest part of the alimentary canal, exhibits structural adaptations to optimize digestion and absorption. These include:

      • Extensive coiling and folding, which increase the surface area available for nutrient absorption.
      • Presence of villi and microvilli on the inner lining, further enhancing the surface area for nutrient absorption.

      The length of the small intestine differs in various animals based on their diet:

      • Herbivores, which eat grass and plant material containing cellulose, have a longer small intestine to allow for prolonged digestion and absorption of cellulose.
      • Carnivores, which primarily consume meat that is easier to digest, have a shorter small intestine.

    17. Define the small intestine and explain its role in digestion.

      The small intestine is a part of the digestive system responsible for the complete digestion of carbohydrates, proteins, and fats. It receives secretions from the liver and pancreas, which aid in the digestion process. The acidic food from the stomach needs to be made alkaline for pancreatic enzymes to act, and this is achieved by bile juice from the liver. Bile salts present in the bile juice break down large fat globules into smaller ones, facilitating efficient enzyme action. The pancreas secretes pancreatic juice containing enzymes like trypsin for protein digestion and lipase for breaking down emulsified fats. The walls of the small intestine secrete intestinal juice containing enzymes that convert proteins to amino acids, complex carbohydrates to glucose, and fats to fatty acids and glycerol.


    18. Explain the role of bile salts in the digestion of fats in the small intestine.

      Bile salts play a crucial role in the digestion of fats in the small intestine. When fats enter the intestine, they are present in the form of large globules, which makes it difficult for enzymes to act on them effectively. Bile salts, present in the bile juice produced by the liver, break down these large fat globules into smaller globules through a process called emulsification. This increases the surface area of the fat, making it easier for the lipase enzyme to break down and digest the fats into fatty acids and glycerol.

      Reaction: Fats (large globules) + Bile salts → Fats (smaller globules)


    19. Describe the structure and function of villi in the small intestine.

      The inner lining of the small intestine is covered with numerous finger-like projections called villi. These villi greatly increase the surface area for absorption of digested food. Each villus has a network of blood vessels, which efficiently transport the absorbed food molecules to every cell of the body. This ensures that the absorbed nutrients are distributed for energy production, tissue building, and tissue repair.

      Villi structure


    20. Explain the process of absorption of digested food in the small intestine.

      The absorption of digested food occurs in the walls of the small intestine, specifically through the villi. As digested food reaches the small intestine, it is absorbed by the villi through their thin walls. The absorbed nutrients, including amino acids, glucose, fatty acids, and glycerol, are then transported by the blood vessels present in the villi to reach every cell of the body. This enables the utilization of absorbed nutrients for energy production, tissue growth, and tissue repair.


    21. Explain the role of the large intestine in the digestion process.

      The large intestine plays a role in the digestion process by absorbing water from the remaining undigested food material. After the absorption of digested food in the small intestine, the unabsorbed material enters the large intestine. The walls of the large intestine absorb water from this material, making it more solid. The remaining undigested material, along with waste products and bacteria, is then eliminated from the body through the anus.


    22. What is the role of the anal sphincter in the elimination of waste material?

      The anal sphincter is a muscular ring located at the end of the digestive tract, specifically the anus. It regulates the exit of waste material from the body. The anal sphincter remains contracted to prevent the involuntary release of waste material until the individual is ready to eliminate it voluntarily. When the individual consciously decides to eliminate the waste, the anal sphincter relaxes, allowing the waste material to be expelled from the body.


    23. Define dental caries and describe its progression.

      Dental caries, also known as tooth decay, is a dental condition characterized by the gradual softening of enamel and dentine. It occurs when bacteria present in the mouth act on sugars from food and produce acids that demineralize the tooth enamel. This demineralization process leads to the formation of dental caries.


    24. Explain the role of bacteria in the development of dental caries.

      Bacteria play a crucial role in the development of dental caries. When sugars from food are consumed, certain bacteria present in the mouth metabolize these sugars and produce acids as byproducts. These acids then interact with the tooth enamel, causing it to soften or demineralize. Over time, the continuous action of bacteria and acids can lead to the progression of dental caries.


    25. Describe the formation of dental plaque and its role in dental caries.

      Dental plaque is formed when masses of bacterial cells, along with food particles, adhere to the teeth. This sticky film, if not removed, acts as a breeding ground for bacteria and promotes their growth. Dental plaque covers the tooth surface, making it difficult for saliva to reach and neutralize the acids produced by bacteria. As a result, the acid attack on the teeth continues, contributing to the development and progression of dental caries.


    26. What is the significance of brushing teeth after eating in preventing dental caries?

      Brushing teeth after eating plays a significant role in preventing dental caries. By brushing, one can effectively remove the dental plaque that accumulates on the teeth, along with any food particles. This helps to disrupt the bacterial activity and remove the potential source of acids. By removing plaque promptly, before the bacteria have a chance to produce acids, the risk of demineralization and tooth decay can be minimized.


    27. Explain the potential consequences of untreated dental caries.

      If left untreated, dental caries can have various consequences. The progressive demineralization of the tooth enamel can lead to the formation of cavities or holes in the teeth. These cavities provide a pathway for bacteria to invade the inner layers of the tooth, including the pulp. The invasion of microorganisms into the pulp can cause inflammation and infection, resulting in symptoms such as toothache, sensitivity, and abscess formation. In severe cases, untreated dental caries may even lead to tooth loss.


    28. Provide examples of reactions involved in the development of dental caries.

      Several reactions occur during the development of dental caries. Examples include:

      • Reaction 1: Bacteria metabolizing sugars produce acids that demineralize the tooth enamel.
      • Reaction 2: Acidic environment promotes the growth of acid-producing bacteria, further contributing to enamel demineralization.
      • Reaction 3: Invasion of microorganisms into the tooth pulp leads to inflammation and infection.

      These reactions highlight the complex biochemical processes involved in the progression of dental caries.


    29. Explain the importance of saliva in preventing dental caries.

      Saliva plays a vital role in preventing dental caries. It contains various components that contribute to maintaining oral health. Saliva acts as a natural defense mechanism by neutralizing acids and buffering the pH of the oral cavity. It also helps in the remineralization process, where essential minerals are redeposited onto the tooth surface, strengthening the enamel. Additionally, saliva aids in the clearance of food particles and bacteria from the mouth, reducing the formation of dental plaque. Thus, an adequate flow of saliva is crucial for preventing the development and progression of dental caries.

    Class 10 Science Chapter 5 - Life Processes

    Class 10 CBSE Important Questions and Answers Chapter 5 - Life Processes


    Class 10 NCERT Chapter 5 - Life Processes AJs Chalo Seekhen Class 10 CBSE Important Questions and Answers Chapter 5 - Life Processes ajs notes history Chapter 5 ajs class 10 Chapter 5 imp questions important questions notes

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