Chapter 5 - Life Processes Class 10 Notes (Science)
Chapter 5 – Life Processes Class 10 Notes (Science)
Updated Solution 2024-2025 Updated 2024-2025
NCERT Solutions for Science, Chapter 5 – Life Processes Class 10 Notes,
Question/Answers, Activity & Projects
Chapter 5 – Life Processes Class 10 Notes (Science)
Questions
Q 1. Why is diffusion insufficient to meet the oxygen requirements of multi-cellular organisms like humans?
Ans 1: Diffusion is too slow and inefficient to meet the oxygen needs of multicellular organisms like humans. This is because:
- Large Size: Humans have many cells spread across a large body. Diffusion alone cannot deliver oxygen to all cells deep inside the body.
- High Demand: Human cells need a constant and large supply of oxygen to produce energy. Diffusion cannot keep up with this demand.
- Distance: In multicellular organisms, some cells are far from the surface where oxygen enters, making it harder for diffusion to reach them.
To overcome these limits, humans have a circulatory and respiratory system to transport oxygen quickly and efficiently.
Q 2. What criteria do we use to decide whether something is alive?
Ans 2: To decide if something is alive, we check for certain features. These include:
- Growth: Living things grow and develop over time.
- Reproduction: They can produce offspring.
- Response to stimuli: They react to changes in their environment (like plants bending toward light).
- Metabolism: Living things take in energy, use it, and release waste.
- Cellular organization: They are made up of one or more cells.
- Homeostasis: They maintain a stable internal environment (like body temperature).
If something has these features, it’s considered alive.
Q 3. What are outside raw materials used for by an organism?
Ans 3: Organisms use outside raw materials for essential life processes:
- Food: Provides energy and nutrients for growth, repair, and maintenance.
- Water: Helps in transporting nutrients, removing waste, and regulating body functions.
- Oxygen: Needed for energy production through respiration.
- Minerals: Support building body structures like bones and aid various biochemical processes.
These materials are critical for survival and maintaining a healthy body.
Q 4. What processes would you consider essential for maintaining life?
Ans 4: To maintain life, essential processes include:
- Nutrition: Eating or absorbing nutrients to get energy and materials for growth.
- Respiration: Breaking down food to release energy.
- Transportation: Moving nutrients, gases, and waste around the body.
- Excretion: Removing waste products to keep the body clean.
- Growth: Increasing in size and repairing cells.
- Reproduction: Creating new life to continue the species.
- Response to Stimuli: Reacting to changes in the environment for survival.
These processes work together to keep organisms alive and healthy.
Activity 5.1
- Take a potted plant with variegated leaves – for example, money plant or crotons.
- Keep the plant in a dark room for three days so that all the starch gets used up.
- Now keep the plant in sunlight for about six hours.
- Pluck a leaf from the plant. Mark the green areas in it and trace them on a sheet of paper.
- Dip the leaf in boiling water for a few minutes.
- After this, immerse it in a beaker containing alcohol.
- Carefully place the above beaker in a water-bath and heat till the alcohol begins to boil.
- What happens to the colour of the leaf? What is the colour of the solution?
- Now dip the leaf in a dilute solution of iodine for a few minutes.
- Take out the leaf and rinse off the iodine solution.
- Observe the colour of the leaf and compare this with the tracing of the leaf done in the beginning (Fig. 5.2).
- What can you conclude about the presence of starch in various areas of the leaf?
Ans: Activity 5.1
1. Prepare the plant: Keep a potted plant with variegated leaves (e.g., money plant or crotons) in a dark room for three days to deplete starch.
Fig 5.2 variegated leaf (a) before and (b) after starch test
2. Sunlight exposure: Place the plant in sunlight for about six hours.
3. Mark the green areas: Pluck a leaf, mark its green areas, and trace them on paper.
4. Boil the leaf: Dip the leaf in boiling water for a few minutes to soften it.
5. Alcohol treatment: Immerse the leaf in alcohol in a beaker and place the beaker in a water bath. Heat until the alcohol boils, removing chlorophyll.
6. Leaf color change: The leaf becomes pale, and the alcohol turns green.
7. Iodine test: Dip the leaf in a dilute iodine solution for a few minutes.
8. Observe results: Rinse the leaf and compare its color with the initial tracing. Blue-black areas indicate starch presence.
9. Conclusion: Starch is present in green areas (photosynthetic regions), showing the role of chlorophyll in photosynthesis.
Q 1. What happens to the colour of the leaf? What is the colour of the solution?
Ans 1: When the leaf is immersed in boiling alcohol, the color of the leaf changes to a pale or almost colorless appearance, as the alcohol extracts the chlorophyll and other pigments. The alcohol solution itself will take on a greenish hue due to the dissolved chlorophyll.
So, after boiling in alcohol:
- The color of the leaf becomes pale or colorless.
- The color of the alcohol solution turns green due to the extraction of chlorophyll.
Q 2. What can you conclude about the presence of starch in various areas of the leaf?
Ans 2: The starch is present only in the green areas of the leaf, where chlorophyll is found. These areas undergo photosynthesis and produce starch. The non-green areas, lacking chlorophyll, do not produce starch, highlighting the essential role of chlorophyll in the photosynthesis process.
Activity 5.2
- Take two healthy potted plants which are nearly the same size.
- Keep them in a dark room for three days.
- Now place each plant on separate glass plates. Place a watch-glass containing potassium hydroxide by the side of one of the plants. The potassium hydroxide is used to absorb carbon dioxide.
- Cover both plants with separate bell-jars as shown in Fig. 5.4.
Figure 5.4 Experimental set-up (a) with potassium hydroxide (b) without potassium hydroxide
- Use Vaseline to seal the bottom of the jars to the glass plates so that the set-up is air-tight.
- Keep the plants in sunlight for about two hours.
- Pluck a leaf from each plant and check for the presence of starch as in the above activity.
- Do both the leaves show the presence of the same amount of starch?
- What can you conclude from this activity?
Ans: Activity 5.4
This experiment is designed to demonstrate the importance of carbon dioxide in photosynthesis. Here’s a step-by-step breakdown and the expected outcome:
Procedure Explanation:
- Two Plants in Darkness: Both plants are kept in a dark room for three days to ensure that they use up any starch stored in their leaves. During this period, photosynthesis cannot occur, so any starch present will be consumed.
- Use of Potassium Hydroxide (KOH): One plant has a watch-glass with potassium hydroxide (KOH) placed near it. KOH absorbs carbon dioxide, preventing it from reaching the plant inside the bell-jar. The other plant has no KOH, allowing carbon dioxide to be available for photosynthesis.
- Covering with Bell-Jars: Both plants are placed under separate bell-jars to create controlled environments. The sealed jars ensure no external air can enter, so the only source of carbon dioxide for each plant will be either the available air inside the jar or none at all (in the case of the plant with KOH).
- Exposure to Sunlight: The plants are exposed to sunlight for about two hours, which is necessary for photosynthesis. The plant without KOH will be able to photosynthesize, while the plant with KOH will not be able to perform this process effectively due to the lack of carbon dioxide.
- Testing for Starch: After two hours, a leaf is plucked from each plant and tested for the presence of starch. The leaf is typically boiled in water to kill it, then placed in iodine solution, which turns blue-black in the presence of starch.
Results and Conclusion:
- Leaf with Potassium Hydroxide (KOH): The leaf from the plant with KOH (which could not access carbon dioxide) will likely not show a blue-black color, indicating that starch has not been produced.
- Leaf without Potassium Hydroxide: The leaf from the plant exposed to carbon dioxide will likely show a blue-black color, indicating that photosynthesis occurred, producing starch.
Conclusion:
- Starch Production and Carbon Dioxide: The plant with KOH did not produce starch because it was deprived of carbon dioxide, demonstrating that carbon dioxide is essential for photosynthesis. The plant without KOH, which had access to carbon dioxide, was able to photosynthesize and produce starch.
Activity 5.3
- Take 1 mL starch solution (1%) in two test tubes (A and B).
- Add 1 mL saliva to test tube A and leave both test tubes undisturbed for 20-30 minutes.
- Now add a few drops of dilute iodine solution to the test tubes.
- In which test tube do you observe a colour change?
- What does this indicate about the presence or absence of starch in the two test tubes?
- What does this tell us about the action of saliva on starch?
Ans: Activity 5.3
This experiment demonstrates the enzymatic action of saliva on starch. Here’s the expected outcome and the reasoning behind it:
Observations:
- Test Tube A (with saliva added):
- After adding iodine, the color of the solution will change from yellow-brown to blue-black if starch is present. However, after the 20-30 minutes incubation, the iodine may show little or no color change. This is because saliva contains the enzyme amylase, which breaks down starch into smaller sugar molecules (like maltose).
- Test Tube B (without saliva):
- The iodine solution will turn blue-black, indicating the presence of starch. Since no amylase is present to break down the starch, it remains unchanged.
Conclusions:
- The color change in test tube B indicates the presence of starch because iodine turns blue-black in the presence of starch.
- The lack of color change in test tube A indicates that starch has been broken down by the enzyme amylase present in the saliva. This shows that the saliva contains enzymes that convert starch into simpler sugars, like maltose, which do not react with iodine in the same way as starch.
What this tells us about the action of saliva on starch:
- Saliva contains the enzyme amylase, which begins the digestion of starch into simpler sugars (like maltose). This process starts in the mouth, breaking down starch as we chew food, making it easier for the body to absorb and process.
Q 1. In which test tube do you observe a colour change?
Ans 1: The color change is observed in Test Tube B (without saliva). The iodine solution turns blue-black, indicating the presence of starch.
Q 2. What does this indicate about the presence or absence of starch in the two test tubes?
Ans 2: The observations indicate the following about the presence or absence of starch in the two test tubes:
- Test Tube A (with saliva added): The lack of a color change after iodine is added suggests that starch has been broken down by the enzyme amylase in the saliva. Therefore, there is little or no starch remaining in the solution. The enzyme amylase has converted the starch into simpler sugars like maltose, which do not react with iodine.
- Test Tube B (without saliva): The iodine solution turns blue-black, which indicates the presence of starch. Since there is no amylase in this test tube to break down the starch, it remains unchanged and reacts with iodine to produce the blue-black color.
In summary, Test Tube A has little or no starch due to the action of amylase, while Test Tube B contains starch, as evidenced by the color change with iodine.
Q 3. What does this tell us about the action of saliva on starch?
Ans 3: The experiment demonstrates that saliva contains the enzyme amylase, which plays a crucial role in the digestion of starch. Amylase begins breaking down starch into simpler sugars, such as maltose, as soon as food enters the mouth. This enzymatic action is evident because in the presence of saliva (Test Tube A), starch is broken down, and the iodine solution does not turn blue-black, indicating that starch is no longer present. In contrast, in the absence of saliva (Test Tube B), the iodine turns blue-black, showing that the starch remains intact. Therefore, this experiment confirms that saliva helps to digest starch by breaking it down into simpler sugars like maltose.
Questions
Q 1. What are the differences between autotrophic nutrition and heterotrophic nutrition?
Ans 1: Autotrophic nutrition is the process by which organisms make their own food using simple substances like carbon dioxide and water, typically through photosynthesis (in plants) or chemosynthesis (in some bacteria). These organisms are called autotrophs.
Heterotrophic nutrition, on the other hand, is the process where organisms obtain their food by consuming other organisms, either plants or animals. These organisms are called heterotrophs and rely on external sources for nutrition.
Q 2. Where do plants get each of the raw materials required for photosynthesis?
Ans 2: Plants get the raw materials for photosynthesis from:
- Carbon dioxide (CO₂): Absorbed from the air through tiny openings in leaves called stomata.
- Water (H₂O): Taken up by the roots from the soil.
- Light energy: Captured by chlorophyll in the chloroplasts from sunlight.
These materials combine in the plant’s leaves to produce glucose and oxygen through the process of photosynthesis.
Q 3. What is the role of the acid in our stomach?
Ans 3: Role of acid in the stomach are as follows:
- Digestion: Stomach acid (hydrochloric acid) helps break down food, particularly proteins.
- Activation of enzymes: It activates pepsinogen to pepsin, an enzyme that digests proteins.
- Defense: The acid kills harmful bacteria and pathogens, protecting the body from infections.
- Absorption: Helps absorb certain nutrients, like vitamin B12 and minerals, by creating an acidic environment.
- Stimulates digestion: It signals other digestive processes to start, improving overall digestion efficiency.
Q 4. What is the function of digestive enzymes?
Ans 4: Digestive enzymes are proteins that help break down food into smaller parts so the body can absorb nutrients. They are produced by the stomach, pancreas, and small intestine. For example, amylase breaks down starches into sugars, lipase helps digest fats, and proteases break down proteins into amino acids. These enzymes make digestion more efficient, ensuring that our body gets the energy and nutrients it needs from the food we eat.
Q 5. How is the small intestine designed to absorb digested food?
Ans 5: The small intestine is specially designed for absorbing digested food through its structure. It has tiny, finger-like projections called villi on its inner walls, which increase the surface area. These villi are covered in even smaller hair-like structures called microvilli. This design allows for a larger surface area, helping more nutrients to be absorbed into the bloodstream. The walls of the small intestine are thin, which makes it easier for nutrients to pass through and be transported to the body. The food is also moved along by muscular contractions, ensuring it mixes well with digestive enzymes.
Activity 5.4
- Take some freshly prepared lime water in a test tube.
- Blow air through this lime water.
- Note how long it takes for the lime water to turn milky.
- Use a syringe or pichkari to pass air through some fresh lime water taken in another test tube (Fig.5.7).
- Note how long it takes for this lime water to turn milky.
- What does this tell us about the amount of carbon dioxide in the air that we breathe out?
Ans: Activity 5.4
Q 1. Blow air through this lime water. Note how long it takes for the lime water to turn milky.
Ans 1: In this experiment, when you blow air through the lime water, it reacts with the carbon dioxide (CO₂) in your breath. The time it takes for the lime water to turn milky depends on the concentration of CO₂ in your exhaled air. Typically, it will take just a few seconds for the lime water to turn milky, indicating the presence of CO₂.
If you blow air gently through the lime water, the process may take a bit longer, while a stronger breath might cause the lime water to turn milky more quickly. In general, human exhaled air contains about 4-5% CO₂, which will cause a noticeable milky effect in lime water.
Q 2. Use a syringe or pichkari to pass air through some fresh lime water taken in another test tube (Fig.5.7). Note how long it takes for this lime water to turn milky.
Ans 2: When you pass air through the lime water using a syringe or pichkari, the time it takes for the lime water to turn milky depends on the amount of CO₂ in the air being passed. Since the syringe or pichkari allows you to control the flow of air more precisely, you will likely notice that it takes less time for the lime water to turn milky compared to blowing air directly through the lime water, because you’re forcing the air through the liquid at a more controlled rate.
If it turns milky quickly, it suggests that the CO₂ concentration in the air being passed through is relatively high. If it takes longer, the concentration of CO₂ is lower.
Figure 5.7: (a) Air being passed into lime water with a pichkari/ syringe, (b) air being exhaled into lime water
Q 3. What does this tell us about the amount of carbon dioxide in the air that we breathe out?
Ans 3: The experiment with lime water shows that the air we breathe out contains carbon dioxide (CO₂). The faster the lime water turns milky, the higher the concentration of CO₂ in our exhaled air. Conversely, if it takes longer for the lime water to turn milky, it indicates a lower concentration of CO₂. Therefore, this experiment helps us understand that CO₂ is a natural component of exhaled air, and the rate at which lime water becomes milky can give an approximate idea of its concentration.
Chapter 5 – Life Processes Class 10 Notes, Question/Answer, Activity & Projects
Updated Solution 2024-2025
Activity 5.5
Q 1. What change is observed in the lime water and how long does it take for this change to occur?
Ans 1: The change observed in the lime water is that it turns milky. This happens because carbon dioxide (CO₂), produced during fermentation by yeast, reacts with calcium hydroxide (Ca(OH)₂) in the lime water to form calcium carbonate (CaCO₃), which is insoluble and gives the solution a milky appearance.
The time it takes for this change to occur can vary depending on factors such as temperature and the amount of sugar or fruit juice used. Typically, the milky appearance may take anywhere from a few minutes to an hour to appear, but the fermentation process continues over a longer period.
Q 2. What does this tell us about the products of fermentation?
Ans 2: The experiment tells us that one of the main products of fermentation is carbon dioxide (CO₂), as indicated by the lime water turning milky when CO₂ reacts with calcium hydroxide to form calcium carbonate (CaCO₃). The production of ethanol (alcohol) is also a key product of fermentation, although it is not directly observed in this experiment. The presence of carbon dioxide highlights the gas release during fermentation, which is important for processes like bread rising and the carbonation in alcoholic beverages.
Activity 5.6
- Observe fish in an aquarium. They open and close their mouths and the gill-slits (or the operculum which covers the gill-slits) behind their eyes also open and close. Are the timings of the opening and closing of the mouth and gill-slits coordinated in some manner?
Ans: Yes, the timings of the opening and closing of the mouth and gill-slits in fish are coordinated in a specific manner. When the fish opens its mouth, it draws in water, which passes over the gills. As the mouth closes, the gill-slits (or operculum) open to allow the water to exit the gills. This synchronized action ensures a continuous flow of water across the gills for efficient oxygen exchange. The mouth and gill-slits generally work in tandem to maintain a consistent respiratory cycle.
- Count the number of times the fish opens and closes its mouth in a minute.
Ans: you will need to observe the fish closely for one minute and count the number of times its mouth opens and closes. Here’s how you can proceed:
- Set a Timer: Use a stopwatch or any timer and start it when you begin observing the fish.
- Observe the Fish: Watch for the rhythmic movements of the fish’s mouth. Each time the mouth opens and closes is counted as one cycle.
- Count the Cycles: Focus on counting how many times the fish’s mouth opens and closes in one minute.
You can repeat this several times if you want to get an average rate of mouth movements, as some fish may show variation in their breathing patterns.
Once you’ve counted the cycles, you can compare this with human breathing patterns for further analysis!
- Compare this to the number of times you breathe in and out in a minute.
Ans: you would compare the number of mouth movements observed in the fish with the number of times you breathe in and out in one minute.
For example:
- Fish Respiration: If you observe that the fish opens and closes its mouth, say, 50 times per minute, this indicates a much higher frequency of respiration compared to humans. Fish typically have a higher respiratory rate because they need to maintain a continuous flow of water over their gills to extract oxygen, especially in environments where oxygen may be scarce.
- Human Breathing: On average, an adult human breathes around 12 to 20 times per minute at rest, which is much slower compared to fish. Human respiration involves alternating inhalation and exhalation, which is less frequent than the continuous rhythmic opening and closing of the fish’s mouth.
Conclusion: You would note that the fish likely has a much higher respiratory rate than humans due to their continuous need for oxygen from water. This difference is partly due to the varying respiratory mechanisms: gill-based for fish versus lung-based for humans.
Questions
Q 1. What advantage over an aquatic organism does a terrestrial organism have with regard to obtaining oxygen for respiration?
Ans 1: A terrestrial organism has an advantage over an aquatic one in obtaining oxygen because air contains much more oxygen than water. In air, oxygen is easier to access and diffuse into the organism’s lungs or other respiratory structures. Aquatic organisms, on the other hand, must extract oxygen from water, which has a lower concentration of oxygen and requires more effort to absorb it through gills.
Q 2. What are the different ways in which glucose is oxidised to provide energy in various organisms?
Ans 2: Glucose is a key source of energy for many organisms, and it can be oxidized in different ways depending on the organism and its environment.
- Aerobic Respiration: In organisms with oxygen, like humans, glucose is broken down in the presence of oxygen into carbon dioxide and water. This process takes place in the mitochondria and produces a lot of energy (ATP).
- Anaerobic Respiration: In the absence of oxygen, some organisms (like yeast and muscle cells) use a process called anaerobic respiration. This results in less energy and produces byproducts like lactic acid (in animals) or ethanol and carbon dioxide (in yeast).
- Fermentation: This is another form of anaerobic process used by yeast and some bacteria. It breaks down glucose without oxygen, producing energy along with byproducts like alcohol or acid.
Each method provides energy, but the amount produced and the byproducts vary based on the presence of oxygen.
Q 3. How is oxygen and carbon dioxide transported in human beings?
Ans 3: Oxygen and carbon dioxide are transported in the human body through the bloodstream.
- Oxygen: When we breathe in, oxygen enters the lungs and then moves into the blood, where it binds to red blood cells. These cells carry oxygen throughout the body to the organs and tissues that need it.
- Carbon Dioxide: This is a waste product produced by the body’s cells. It moves from the cells into the bloodstream, where most of it is carried in the form of bicarbonate ions. The blood transports it to the lungs, where it is exhaled out of the body when we breathe out.
Q 4. How are the lungs designed in human beings to maximise the area for exchange of gases?
Ans 4: The human lungs are designed to maximize the area for gas exchange through several features. First, they have millions of tiny air sacs called alveoli, which provide a large surface area. These alveoli are surrounded by a network of capillaries, which allow oxygen to pass into the blood and carbon dioxide to be removed. The thin walls of the alveoli and capillaries make the gas exchange process efficient. Additionally, the branching structure of the airways ensures that air reaches every part of the lungs, further increasing the surface area for exchange.
Fig: Alveoli In the Lungs
Activity 5.7
- Visit a health center in your locality and find out what is the normal range of hemoglobin content in human beings.
Ans: you would need to visit a local health center or a medical facility to gather specific information about the normal range of hemoglobin content in humans. Based on general medical knowledge, you could expect the following normal hemoglobin ranges:
- For Men: 13.8 to 17.2 grams per deciliter (g/dL)
- For Women: 12.1 to 15.1 g/dL
However, to get more accurate or region-specific data, a visit to a health center or lab for a blood test would be the best course of action.
- Is it the same for children and adults?
Ans: No, hemoglobin levels are different for children and adults. Newborns and infants typically have higher hemoglobin levels than older children and adults. As children grow, their hemoglobin levels gradually stabilize and fall within the adult range.
- Is there any difference in the hemoglobin levels for men and women?
Ans: Yes, there is a difference in hemoglobin levels between men and women. Men typically have higher hemoglobin levels than women due to factors such as higher muscle mass, which requires more oxygen, and the hormone testosterone, which promotes red blood cell production. In contrast, women tend to have lower hemoglobin levels, partly due to menstrual blood loss.
- Visit a veterinary clinic in your locality. Find out what is the normal range of hemoglobin content in an animal like the buffalo or cow.
Ans: The normal range of hemoglobin content in cows or buffalo is typically 10 to 15 grams per deciliter (g/dL). Calves have slightly lower levels, generally ranging from 9 to 13 g/dL. You can visit a local veterinary clinic to get more specific details based on regional and species variations.
- Is this content different in calves, male and female animals?
Ans: The hemoglobin content in calves, male, and female animals is generally similar, but there are some differences:
- Calves have lower hemoglobin levels compared to adult animals, as they are still growing.
- Male and female animals (such as cows or buffaloes) may have slight differences in hemoglobin levels, but these variations are less pronounced than those seen in humans. The differences are usually linked to size and muscle mass, with males potentially having slightly higher levels.
- How would the difference, if any, be explained?
Ans: The difference in hemoglobin levels between humans and animals can be explained by the following points:
- Human Differences:
- Testosterone: In men, higher testosterone levels promote red blood cell production, resulting in higher hemoglobin levels.
- Menstrual Blood Loss: Women experience monthly blood loss, which lowers their hemoglobin levels.
- Body Composition: Men generally have more muscle mass, requiring more oxygen and leading to higher hemoglobin levels.
- Animal Differences:
- Age: Young animals (e.g., calves) have lower hemoglobin levels due to their developing bodies.
- Sex: In some species, males may have slightly higher hemoglobin levels due to larger body size and muscle mass, but the difference is less significant than in humans.
- Absence of Menstruation: Female animals do not experience menstruation, so blood loss is not a factor influencing hemoglobin levels.
- Compare the difference seen in male and female human beings and animals.
Ans: Here is a summarized comparison of hemoglobin levels in male and female humans and animals:
Category | Human (Male vs. Female) | Animals (Male vs. Female) |
Hemoglobin Levels | Males: 13.8–17.2 g/dL | Cows/Buffalo: 10–15 g/dL (both sexes) |
Difference in Levels | Males generally have higher levels due to muscle mass, testosterone, and no blood loss from menstruation | Minor differences between male and female animals, less pronounced than in humans |
Reasons for Difference | Testosterone increases red blood cell production in men Menstrual blood loss in women lowers levels | Males may have slightly higher levels due to larger muscle mass |
Significance | Clear difference in hemoglobin due to physiological factors | Difference is less significant compared to humans |
Activity 5.8
- Take two small pots of approximately the same size and having the same amount of soil. One should have a plant in it. Place a stick of the same height as the plant in the other pot.
- Cover the soil in both pots with a plastic sheet so that moisture cannot escape by evaporation.
- Cover both sets, one with the plant and the other with the stick, with plastic sheets and place in bright sunlight for half an hour.
- Do you observe any difference in the two cases?
Ans: Activity 5.8
Observation and Explanation of Activity 5.8:
When you perform this activity, here’s what you’ll observe:
- Pot with the Plant:
- The inner surface of the plastic sheet covering the plant will have visible water droplets.
- This is due to transpiration, a process where water evaporates from the leaves of the plant and condenses on the plastic sheet.
- Pot with the Stick:
- The inner surface of the plastic sheet covering the stick will remain dry or show no significant moisture.
- This is because the stick does not transpire like the plant does.
Explanation:
- Transpiration is the loss of water vapor from the aerial parts of a plant, primarily through the stomata in the leaves.
- The plant absorbs water from the soil through its roots. In sunlight, this water is released as water vapor from the leaves, causing condensation on the plastic sheet.
- The stick, being non-living, does not have any such mechanism to release water vapor.
Conclusion:
This activity demonstrates transpiration in plants, highlighting the role of plants in water movement and their contribution to the water cycle.
Q1. Do you observe any difference in the two cases?
Ans 1: Yes, there is a clear difference:
- Pot with the Plant: The plastic sheet shows water droplets inside because the plant releases water vapor through its leaves (transpiration).
- Pot with the Stick: The plastic sheet remains dry since the stick, being non-living, does not release water.
This difference highlights that living plants can release water, while non-living objects cannot.
Questions
Q 1. What are the components of the transport system in human beings? What are the functions of these components?
Ans 1: The transport system in humans consists of the heart, blood, and blood vessels. Here’s what each does:
- Heart: Pumps blood to circulate it throughout the body.
- Blood: Carries oxygen, nutrients, hormones, and waste products.
- Blood Vessels:
- Arteries: Carry oxygen-rich blood from the heart to the body.
- Veins: Bring oxygen-poor blood back to the heart.
- Capillaries: Connect arteries and veins, allowing exchange of substances with cells.
These components work together to supply the body with essential materials and remove waste.
Q 2. Why is it necessary to separate oxygenated and deoxygenated blood in mammals and birds?
Ans 2: In mammals and birds, separating oxygenated and deoxygenated blood is crucial for efficient oxygen supply. It ensures that oxygen-rich blood reaches the body and oxygen-poor blood goes to the lungs for reoxygenation. This supports their high energy needs for activities like flying or running and maintains a stable body temperature.
Q 3. What are the components of the transport system in highly organised plants?
Ans 3: The transport system in highly organized plants consists of two main components:
- Xylem: It carries water and minerals from the roots to the rest of the plant.
- Phloem: It transports food (sugars) made in the leaves to other parts of the plant.
These systems work together to distribute nutrients, water, and minerals, ensuring the plant’s growth and survival.
Q 4. How are water and minerals transported in plants?
Ans 4: Water and minerals are transported in plants through a system of specialized tissues: xylem and phloem.
- Water Transport:
- Roots absorb water from the soil.
- Water moves up through the xylem due to root pressure, capillary action, and transpiration pull (water evaporation from leaves).
- Mineral Transport:
- Minerals dissolve in water and are absorbed by the roots.
- These nutrients are carried upward through the xylem to other parts of the plant.
This process ensures plants get the water and nutrients they need for growth and photosynthesis.
Figure 5.12 Movement of water during transpiration in a tree
Q 5. How is food transported in plants?
Ans 5: In plants, food is transported through a system of tubes called phloem. This process is known as translocation. The food, mainly in the form of sugars, is produced in the leaves during photosynthesis. The sugars are then moved from the leaves to other parts of the plant, such as the stems, roots, and flowers, where they are needed for growth and energy. This movement happens through a combination of pressure and flow, driven by the plant’s need to distribute the nutrients.
Questions
Q 1. Describe the structure and functioning of nephrons.
Ans 1: Nephrons are the tiny units in our kidneys that filter waste from the blood to form urine. Each kidney has around a million nephrons.
Structure:
- Bowman’s Capsule: This is a cup-like structure that collects waste from the blood. It surrounds a network of tiny blood vessels called glomerulus.
- Glomerulus: A group of capillaries where blood is filtered.
- Proximal Convoluted Tubule (PCT): The filtered fluid moves here, and useful substances like glucose and ions are reabsorbed.
- Loop of Henle: This part helps in water reabsorption and concentrates the urine.
- Distal Convoluted Tubule (DCT): More reabsorption and secretion happen here to balance salt and water.
- Collecting Duct: It collects urine from multiple nephrons and sends it to the ureter.
Function: Nephrons filter waste, regulate water and salt levels, and help in removing excess substances from the body. They keep the blood clean and maintain the right balance of fluids and salts.
Figure 5.14 Structure of a nephron
Q 2. What are the methods used by plants to get rid of excretory products?
Ans 2: Plants have several ways to get rid of waste products:
- Transpiration: Water vapor, which can contain waste like salts, is lost through tiny pores in leaves called stomata.
- Excretion through Glands: Some plants have specialized glands that secrete waste substances like resins or oils.
- Leaf Fall: Plants often shed leaves when they accumulate too much waste, helping to remove excess substances.
- Secretion of Waste: Some plants excrete waste through roots or stems, where it may accumulate and be washed away by rain or soil.
These methods help plants manage waste without affecting their growth
Q 3. How is the amount of urine produced regulated?
Ans 3: The amount of urine produced is regulated by the kidneys, which filter blood and remove waste. This process is controlled by hormones like antidiuretic hormone (ADH) and aldosterone. ADH helps the kidneys retain water, reducing urine output when the body needs to conserve water. Aldosterone helps balance salt and water levels, affecting urine concentration. The body’s hydration status and salt levels trigger these hormones, ensuring the right amount of urine is produced to maintain balance.
Exercise
Q 1. The kidneys in human beings are a part of the system for:
(a) Nutrition.
(b) Respiration.
(c) Excretion.
(d) Transportation.
Ans 1: (c) Excretion: The kidneys are part of the excretory system in humans, responsible for filtering waste products from the blood and producing urine.
Q 2. The xylem in plants is responsible for:
(a) transport of water.
(b) transport of food.
(c) transport of amino acids.
(d) transport of oxygen.
Ans 2: (a) transport of water: Xylem is the tissue in plants responsible for transporting water and minerals from the roots to the rest of the plant.
Q 3. The autotrophic mode of nutrition requires:
(a) carbon dioxide and water.
(b) chlorophyll.
(c) sunlight.
(d) all of the above.
Ans 3: (d) all of the above:
Autotrophic organisms, such as plants, use carbon dioxide and water to produce their own food in the presence of sunlight and chlorophyll through the process of photosynthesis.
Q 4. The breakdown of pyruvate to give carbon dioxide, water and energy takes place in
(a) cytoplasm.
(b) mitochondria.
(c) chloroplast.
(d) nucleus.
Ans 4: (b) mitochondria: The breakdown of pyruvate to give carbon dioxide, water, and energy takes place in the mitochondria. This process is part of cellular respiration, specifically during the citric acid cycle (Krebs cycle), which occurs in the mitochondria.
Q 5. How are fats digested in our bodies? Where does this process take place?
Ans 5: Digestion of Fats in the Body:
- Mouth: Digestion starts in the mouth, where the enzyme lingual lipase begins to break down fats, but only a small amount.
- Stomach: In the stomach, gastric lipase further breaks down fats into smaller molecules.
- Small Intestine:
- Most fat digestion happens here.
- Bile, produced by the liver and stored in the gallbladder, emulsifies fats (breaks them into smaller droplets).
- Pancreatic lipase from the pancreas then breaks down the fat droplets into fatty acids and glycerol.
- Absorption: These fatty acids and glycerol are absorbed by the walls of the small intestine and enter the bloodstream.
- Transport: The absorbed fats are transported via lymphatic vessels to various parts of the body for energy storage or use.
Q 6. What is the role of saliva in the digestion of food?
Ans 6: Role of Saliva in Digestion:
- Moistens food: Saliva softens and moistens food, making it easier to chew and swallow.
- Contains enzymes: It has amylase, an enzyme that breaks down starches into simpler sugars.
- Cleanses mouth: Helps wash away food particles and bacteria, keeping the mouth clean.
- Aids taste: Saliva dissolves food particles, which helps activate taste buds for better flavor detection.
- Protects teeth: It neutralizes acids in the mouth, reducing the risk of tooth decay.
Q 7. What are the necessary conditions for autotrophic nutrition and what are its byproducts?
Ans 7: Necessary Conditions for Autotrophic Nutrition:
- Presence of Sunlight: Required for photosynthesis, the process by which plants make their own food.
- Chlorophyll: A pigment in plants that captures sunlight and helps convert it into chemical energy.
- Water: Absorbed by roots and used in photosynthesis.
- Carbon Dioxide: Taken from the air for photosynthesis to occur.
- Proper Temperature: Necessary for enzymes to function in the process of food production.
Byproducts of Autotrophic Nutrition:
- Oxygen: Released into the air as a byproduct during photosynthesis.
- Glucose: The primary food or energy source made by plants.
Q 8. What are the differences between aerobic and anaerobic respiration? Name some organisms that use the anaerobic mode of respiration.
Ans 8: Differences between aerobic and anaerobic respiration:
Feature | Aerobic Respiration | Anaerobic Respiration |
Oxygen Requirement | Requires oxygen | Does not require oxygen |
Energy Yield | High (36-38 ATP molecules per glucose molecule) | Low (2 ATP molecules per glucose molecule) |
End Products | Carbon dioxide (CO₂) and water (H₂O) | Lactic acid (in animals) or ethanol and CO₂ (in yeast) |
Location in Cells | Mitochondria | Cytoplasm |
Efficiency | More efficient, complete oxidation of glucose | Less efficient, partial oxidation of glucose |
Examples of Organisms | Humans, animals, plants, most fungi | Yeast, certain bacteria, muscle cells in humans (during intense exercise) |
Energy Source | Glucose, fatty acids, proteins | Mainly glucose |
Process Stages | Glycolysis, Krebs cycle, Electron transport chain | Glycolysis, followed by fermentation |
Organisms that use anaerobic respiration:
- Yeast (produces ethanol and CO₂)
- Lactic acid bacteria (e.g., Lactobacillus)
- Some bacteria (e.g., Clostridium, Escherichia coli)
- Muscle cells in humans (during heavy exercise, leading to lactic acid production)
Q 9. How are the alveoli designed to maximise the exchange of gases?
Ans 9: The alveoli are designed to maximize gas exchange through the following features:
- Large Surface Area: Numerous alveoli provide a large surface area for gas exchange.
- Thin Walls: Alveolar walls are very thin (one cell thick), allowing gases to diffuse easily.
- Moist Surface: The inside of alveoli is moist, which helps gases dissolve and diffuse better.
- Rich Blood Supply: They are surrounded by a network of capillaries, ensuring a constant flow of oxygen and carbon dioxide.
- Close Proximity: The walls of the alveoli and capillaries are close together, reducing the distance for gas diffusion.
- Elasticity: Alveoli are elastic, which helps them expand and contract for efficient air intake and removal.
Q 10. What would be the consequences of a deficiency of hemoglobin in our bodies?
Ans 10: A deficiency of hemoglobin in the body, known as anemia, can lead to tiredness, weakness, and dizziness. Hemoglobin helps carry oxygen to our cells, so without enough of it, the body doesn’t get the oxygen it needs to function properly. This can cause difficulty in breathing, pale skin, and, in severe cases, heart problems. It is important to treat anemia to restore energy and overall health.
Q 11. Describe double circulation of blood in human beings. Why is it necessary?
Ans 11: Double circulation in humans refers to the flow of blood through the heart twice during one complete cycle. It consists of two circuits: the pulmonary circulation and the systemic circulation.
- Pulmonary Circulation: Deoxygenated blood from the body enters the right atrium of the heart, flows into the right ventricle, and is pumped to the lungs via the pulmonary artery. In the lungs, the blood gets oxygenated and releases carbon dioxide.
- Systemic Circulation: Oxygenated blood returns to the left atrium from the lungs, moves into the left ventricle, and is pumped through the aorta to the rest of the body. This blood supplies oxygen and nutrients to tissues and organs and collects waste products like carbon dioxide.
Necessity of Double Circulation: Double circulation is vital for efficient oxygen transport and waste removal. The separation of oxygenated and deoxygenated blood prevents mixing, ensuring tissues receive blood rich in oxygen, which is essential for cellular respiration. Additionally, the two circulations maintain higher blood pressure in the systemic circulation, facilitating the delivery of oxygen and nutrients to distant organs. This system enhances overall body function and energy efficiency.
Q 12. What are the differences between the transport of materials in xylem and phloem?
Ans 12: Here is a differences of material transport in xylem and phloem:
Feature | Xylem | Phloem |
Function | Transports water and minerals. | Transports food (mainly sugars) and other organic compounds. |
Direction of Flow | Unidirectional (from roots to leaves). | Bidirectional (from source to sink). |
Main Transport Material | Water and dissolved minerals. | Sugars (mainly sucrose), amino acids, hormones. |
Cell Type | Dead, hollow cells (tracheid’s and vessel elements). | Living cells (sieve tubes, companion cells). |
Structure | Xylem vessels are thick-walled and lignified. | Phloem sieve tubes have perforated sieve plates. |
Energy Requirement | Passive process (no energy required). | Active process (requires ATP energy for loading/unloading). |
Transport Mechanism | Driven by transpiration and capillary action. | Driven by pressure flow (mass flow hypothesis). |
Location in the Plant | Primarily in roots, stems, and leaves. | Found in all parts of the plant, especially in stems and leaves. |
Rate of Transport | Relatively slow. | Rapid and dynamic, especially during active growth. |
Q 13. Compare the functioning of alveoli in the lungs and nephrons in the kidneys with respect to their structure and functioning
Ans 13: The alveoli in the lungs and nephrons in the kidneys have distinct yet somewhat analogous roles in maintaining vital functions in the body. Below is a comparison of their structure and functioning:
Aspect | Alveoli (Lungs) | Nephrons (Kidneys) |
Structure | Tiny, thin-walled sacs surrounded by capillaries. | Comprised of a renal corpuscle and renal tubules. |
Function | Facilitate gas exchange (O₂ in, CO₂ out). | Filter blood to form urine, regulating water and solute balance. |
Exchange Process | Oxygen and carbon dioxide diffuse across alveolar walls into capillaries. | Waste products (urea, excess salts) are filtered from the blood. |
Role in Homeostasis | Helps maintain oxygen levels and remove CO₂ from the body. | Maintains electrolyte balance, fluid regulation, and removes metabolic wastes. |
Blood Flow | Blood enters via pulmonary arteries and exits via pulmonary veins. | Blood enters via renal arteries and exits via renal veins. |
Filtration Process | No filtration—only gas exchange occurs. | Filtration, reabsorption, and secretion occur in the nephron to form urine. |
Chapter 5 – Life Processes Class 10 Notes, Question/Answer, Activity & Projects
Updated Solution 2024-2025
This complete solution is prepared as per the latest syllabus of 2024-25. If you have any further queries, feel free to ask! 