GSEB Class 10 Science Solutions Chapter 6 Life Processes

 

Question 1. Why is diffusion insufficient to meet the oxygen requirements of multicellular organisms like humans?
Answer: Multicellular organisms have many cells, and not all of them might be touching the outside world. So, diffusion alone won't be enough to give oxygen to every single cell.
In simple words: Diffusion is too slow for big living things because not all their cells are close to the air.

Exam Tip: Remember that multicellular organisms have a larger volume to surface area ratio, making simple diffusion inadequate for gas exchange across all cells.

 

Question 2. What criteria do we use to decide whether something is alive?
Answer: We can tell if something is alive by checking for movement when it senses things outside itself, if it breathes, and if it grows.
In simple words: Things that move, breathe, and grow are usually considered alive.

Exam Tip: Key indicators of life include growth, reproduction, metabolism, response to stimuli, and movement.

 

Question 3. What are the outside raw materials used for maintenance and sustenance of life by an organism?
Answer: Outside raw materials are used for maintenance and sustenance of life by an organism.
In simple words: Organisms use materials from their surroundings to stay alive and keep their bodies working.

Exam Tip: Consider essential nutrients like food, water, and oxygen as primary external raw materials for life processes.

 

Question 4. What processes would you consider essential for maintaining life?
Answer: Any process that helps living things stay alive is called a life process. All these important processes are needed to keep an organism living.
In simple words: Processes like nutrition, respiration, transport, and excretion are vital for life.

Exam Tip: Focus on the four main categories of life processes: nutrition, respiration, transportation, and excretion, as they are fundamental.

 

Question 5. What are the differences between autotrophic nutrition and heterotrophic nutrition?
Answer:
Autotrophic Nutrition:

• Food is made from simple, non-living ingredients.
• Chlorophyll and sunlight are necessary.
• Photosynthesis or chemosynthesis takes place.
• It occurs in green plants and some bacteria.

Heterotrophic Nutrition:

• Food is obtained from complex organic sources.
• Chlorophyll and sunlight are not needed.
• These processes do not occur.
• It occurs in animals and insectivorous plants.

In simple words: Autotrophs make their own food, like plants. Heterotrophs eat other organisms for food, like animals.

Exam Tip: When comparing, always highlight key distinctions like source of food, energy requirement, specific processes involved, and examples of organisms.

 

Question 6. Where do plants get each of the raw materials required for photosynthesis?
Answer: To make food, plants get their basic ingredients from different places:

1. Water: Roots take it from the soil.
2. Carbon dioxide: Tiny openings on leaves, called stomata, let this gas into the plant.
3. Chlorophyll: This green substance is already found inside the leaves.

In simple words: Plants get water from roots, carbon dioxide from the air through leaves, and already have chlorophyll in their leaves.

Exam Tip: List each raw material separately and clearly state its source and how it enters the plant for photosynthesis.

 

Question 7. What is the role of acid in our stomach?
Answer: The acid (HCl) in our stomach creates an acidic environment. This helps the enzyme pepsin work better and also kills germs that come in with our food.
In simple words: Stomach acid helps an enzyme called pepsin digest food and kills harmful bacteria.

Exam Tip: Remember the dual function of HCl in the stomach: activating pepsinogen to pepsin and providing a protective barrier against pathogens.

 

Question 8. What is the function of digestive enzymes?
Answer: Digestive enzymes break down complex food items into much simpler parts.
In simple words: Digestive enzymes split large food molecules into smaller ones that the body can use.

Exam Tip: Recall that enzymes are biological catalysts, speeding up the breakdown of complex molecules like carbohydrates, proteins, and fats into absorbable units.

 

Question 9. How is the small intestine designed to absorb the digested food?
Answer: The small intestine has tiny, finger-shaped bumps on its inside surface. These bumps, called villi, make the area bigger for soaking up nutrients from food. Villi have many blood vessels that then carry this absorbed food to every cell throughout the body.
In simple words: The small intestine has tiny folds called villi, which increase its surface area to absorb food easily into the blood.

Exam Tip: Focus on villi, microvilli, and extensive blood supply as key adaptations that maximize the absorption efficiency in the small intestine.

 

Question 10. What advantages over an aquatic organism does a terrestrial organism have with regard to obtaining oxygen for respiration?
Answer: Land organisms have an advantage over water organisms because air contains a higher percentage of oxygen than water. This means animals on land can get more oxygen at once compared to those living in water.
In simple words: Terrestrial organisms can get more oxygen because there is more oxygen in the air than dissolved in water.

Exam Tip: Contrast the oxygen availability in air (higher concentration) versus water (lower concentration), and relate it to the ease of gas exchange for each type of organism.

 

Question 11. What are the different ways in which glucose is oxidised to provide energy in various organisms?
Answer: The breakdown of glucose happens through various routes in different organisms: Glucose (6-carbon molecule) first breaks down in the cytoplasm to form Pyruvate (3-carbon molecule) and energy. From Pyruvate, there are three primary pathways:

1. Absence of \( O_2 \) (in yeast)
   \( \implies \) Ethanol + \( CO_2 \) + Energy (2-carbon molecule).
2. Lack of \( O_2 \) (in muscle cells)
   \( \implies \) Lactic acid + Energy (3-carbon molecule).
3. Presence of \( O_2 \) (in mitochondria)
   \( \implies \) \( CO_2 \) + \( H_2O \) + Energy.

In simple words: Glucose breaks down in different ways depending on oxygen levels: into alcohol without oxygen in yeast, lactic acid with low oxygen in muscles, or carbon dioxide and water with enough oxygen.

Exam Tip: Clearly distinguish between aerobic respiration (presence of oxygen) and anaerobic respiration (absence or lack of oxygen), listing the specific end products and locations for each pathway.

 

Question 12. How is oxygen and carbon dioxide transported in human beings?
Answer: Oxygen moves around the body attached to haemoglobin, which is found in red blood cells. Carbon dioxide, however, dissolves easily in water, so it travels in the blood in a dissolved state.
In simple words: Oxygen travels with red blood cells using haemoglobin, while carbon dioxide dissolves in blood plasma for transport.

Exam Tip: Emphasize haemoglobin's role as the oxygen carrier and the solubility of carbon dioxide in water (plasma) for its transportation.

 

Question 13. How are lungs designed in human beings to maximise the area for exchange of gases?
Answer: Human lungs have tiny tubes called bronchioles. These divide into even smaller tubes that end in small, balloon-like sacs known as alveoli. The alveoli give a very large area where gases can easily be swapped.
In simple words: Lungs have millions of tiny air sacs called alveoli, which provide a huge surface for efficient gas exchange.

Exam Tip: Highlight the large surface area, thin walls, and rich blood supply of the alveoli as key features optimizing gas exchange in the lungs.

 

Question 14. What are the components of transport system in human beings? What are the functions of these components?
Answer: The human transport system has several parts:
(i) Heart: This organ pumps blood throughout the body.
(ii) Blood: This is the liquid that moves things around. It includes:

• Plasma – carries food, waste products, salts, carbon dioxide, and hormones in a dissolved state.
• RBC (Red Blood Cells) – These cells have haemoglobin and move oxygen.
• WBC (White Blood Cells) – These cells help fight illnesses.
• Platelets – These tiny cells help blood to clot if there's an injury.

(iii) Blood vessels: These are the tubes that carry blood.

• Arteries – They take oxygen-rich blood away from the heart to all parts of the body.
• Veins – They bring de-oxygenated blood back to the heart so it can be cleaned.

In simple words: The human transport system consists of the heart (pumps blood), blood (carries substances), and blood vessels (tubes for blood flow).

Exam Tip: When describing components, always specify their structure and primary function clearly, noting the distinct roles of plasma, RBCs, WBCs, and platelets within blood.

 

Question 15. Why is it necessary to separate oxygenated and deoxygenated blood in mammals and birds?
Answer: Mammals and birds require a lot of energy for their daily activities. Separating oxygen-rich blood ensures that a high supply of oxygen reaches cells, which helps generate this necessary energy efficiently by breaking down food.
In simple words: Mammals and birds need lots of energy, so keeping oxygenated and deoxygenated blood separate ensures a constant, high supply of oxygen to meet their energy demands.

Exam Tip: Link the separation of blood to the high metabolic rate and constant energy requirements of endothermic (warm-blooded) animals like mammals and birds.

 

Question 16. What are the components of the transport system in highly organised plants?
Answer: In complex plants, the transport system is made of two main parts: xylem and phloem.
In simple words: Plants use xylem and phloem to move things around.

Exam Tip: Remember xylem transports water and minerals, while phloem transports food (sugars) throughout the plant.

 

Question 17. How are water and minerals, transported in plants?
Answer: Plants transport water and minerals using xylem tissue. Roots take in water from the soil by actively drawing in ions, which creates a concentration difference between the root and the soil. Water then moves into the root cells. This upward movement forms a continuous column of water, pushed through the vessels and tracheids in the roots, stem, and leaves, forming a network of water-carrying channels throughout the plant. Water loss from leaves through tiny pores, called stomata, is known as transpiration. This process creates a pulling force that draws water up from the roots' xylem cells.
In simple words: Water and minerals move up through the xylem. Roots absorb water, creating a column that is pulled upwards by transpiration (water loss from leaves).

Exam Tip: Explain the process as a combination of root pressure (active ion uptake) and transpiration pull (cohesion-tension theory), highlighting the role of xylem.

 

Question 18. How is food transported in plants?
Answer: Food transport in plants is called translocation. It occurs through a special tissue called phloem. Phloem moves sugars (like glucose), amino acids, and other materials from the leaves to the roots, shoots, fruits, and seeds. Sieve tubes and companion cells assist in moving food both up and down the plant. Sugars are transported using energy from ATP and osmotic pressure created by water. This pressure helps move materials to plant parts with lower pressure.
In simple words: Food, mainly sugars, moves through the phloem tissue. This process, called translocation, uses energy to push food from where it's made (leaves) to other parts of the plant where it's needed or stored.

Exam Tip: Focus on phloem as the specific tissue for food transport (translocation) and mention the involvement of ATP and osmotic pressure for active movement.

 

Question 19. Describe the structure and functioning of nephrons.
Answer: **Structure of nephrons:** Each nephron has a Bowman's capsule which contains a glomerulus (a cluster of tiny blood vessels). Various arteries bring impure blood to the nephron. The cup-shaped Bowman's capsule forms a tubular part of the nephron that connects to a collecting duct.
**Working of Nephron:**
(i) Filtration: The renal artery, or afferent artery, is wide at first but then narrows into a tube within the glomerulus. This change in width creates pressure, which forces water and dissolved waste products out of the blood. This filtered liquid collects in the cup-like Bowman's capsule and then moves into the tubule that surrounds it.
(ii) Reabsorption: The filtered fluid then passes through the tubule, where important substances like water, glucose, and amino acids are selectively taken back by the capillaries that surround the tubule.
(iii) Urine formation: Any water and impurities that were not reabsorbed are sent to a collecting duct. This filtered liquid contains many dissolved nitrogenous wastes, such as urea, and is therefore called urine. From the collecting duct, the urine travels into the ureter and is stored in the urinary bladder.

The diagram 'Structure of a nephron' shows a kidney nephron. It starts with the Branch of renal artery, leading into the Glomerulus, which is inside Bowman's capsule. From the Bowman's capsule, a convoluted Tubular part of nephron extends, leading down towards a Collecting duct. A Renal artery and Branch of renal vein are also shown supplying the structure.
In simple words: Nephrons in kidneys filter blood using Bowman's capsule and a tubule. They first filter wastes out, then reabsorb useful substances, and finally, unabsorbed waste forms urine.

Exam Tip: Clearly outline the three main stages of nephron function: glomerular filtration, tubular reabsorption, and tubular secretion (implicitly covered by urine formation), linking them to specific parts of the nephron.

 

Question 20. What are the methods used by plants to get rid of excretory products?
Answer: Plants get rid of waste materials in several ways:

• Gaseous wastes – Carbon dioxide is released during breathing through tiny pores called stomata, and oxygen is released through stomata during photosynthesis.
• Liquid wastes (water) – Water vapor exits through stomata via a process called transpiration.
• Other wastes are kept in dead cells within leaves, which then fall off. Additionally, some waste products like resins and gums are stored in the old xylem of the plant, and other wastes are released from nodes into the soil.

In simple words: Plants release gas wastes through leaf pores, lose water vapor by transpiration, and store solid wastes in old leaves, bark, or release them into the soil.

Exam Tip: Categorize plant excretory products (gaseous, liquid, solid) and explain the specific mechanisms for their removal (stomata, transpiration, leaf fall, storage in old tissues).

 

Question 21. How is the amount of urine produced regulated?
Answer: The quantity of urine produced is controlled by how much excess water and dissolved waste the body needs to get rid of. For example, on a hot day, when we perspire and lose a lot of body fluid and salts, most of the water and salts in the kidney are reabsorbed back into the blood from the filtered liquid. This results in less urine being produced. In colder weather, when we don't sweat as much, more water and salts are reabsorbed, so a greater volume of urine is produced. This process maintains perfect fluid balance, called osmoregulation, in the body.
In simple words: The body controls urine production based on its water and waste levels. More water loss (like sweating) means less urine, while less water loss means more urine, keeping the body balanced.

Exam Tip: Emphasize the role of the kidneys in maintaining osmoregulation, adapting urine volume based on body hydration and metabolic waste load.

 

Activity 6.1.
Answer: **Aim:** To prove that chlorophyll is essential for photosynthesis.
**Material Required:** Potted plant with variegated leaves, sheet of paper, beaker, alcohol, water bath, Bunsen burner, dilute solution of iodine.
**Procedure:**

• Take a potted plant with variegated leaves (e.g., money plant or crotons).
• Keep the plant in a dark room for three days so that all the starch gets used up.
• Keep the plant in sunlight for about six hours.
• Pluck a leaf from the plant. Mark the green areas on 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.
• The color of the leaf changes from green to colorless as the chlorophyll is removed from it and the solution turns green.
• Now dip the leaf in a dilute solution of iodine for a few minutes. Take out the leaf and rinse off the iodine solution.

**Observations:** The color of the iodine on leaf at dark spots changes to blue-black and the green areas turn blue-black, showing the presence of starch.
**Conclusion:** This experiment shows that chlorophyll is needed for photosynthesis, the process plants use to make starch.
In simple words: This activity shows chlorophyll is needed for photosynthesis. We remove chlorophyll, test for starch with iodine, and find starch only where chlorophyll was present.

Exam Tip: When describing an experiment, always clearly state the Aim, Materials, Procedure (step-by-step), Observations, and Conclusion, ensuring logical flow and accurate scientific terms.

 

Activity 6.2.
Answer: **Aim:** To show that carbon dioxide is necessary for starch formation.
**Material Required:** Two potted plants, two bell shaped glass jars, watch glass, KOH, vaseline and glass plates. Cover both plants with separate bell-jars as shown in figure below.
**Procedure:** 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. Use vaseline to seal the bottom of the jars to the glass plates so that the set up is airtight. Keep the plants in sunlight for about two hours. Pluck a leaf from each plant and check for the presence of starch.
**Observation:** The leaf of the pot with KOH will not turn blue-black because KOH absorbs carbon dioxide required for photosynthesis. The leaf of pot without KOH will show blue-black color due to presence of \( CO_2 \) which is essential for starch formation in plants.
**Conclusion:** This experiment concludes that carbon dioxide is vital for plants to make starch.
The diagram 'Experimental set-up' shows two bell jars. Setup (a) has a potted plant and a watch-glass containing potassium hydroxide (KOH), indicating the absorption of CO2. Setup (b) has a potted plant without KOH. Both plants are sealed with a bell jar.
In simple words: This activity shows carbon dioxide is needed for starch. Plants without CO2 (because of KOH) don't make starch, unlike plants with CO2.

Exam Tip: In experiments testing a specific requirement, ensure a control setup (without the tested factor) is included for comparison, as demonstrated with the KOH setup here.

 

Activity 6.3.
Answer: **Aim:** To show the action of saliva on starch.
**Procedure:** Take 1ml starch solution (1%) in two test tubes (A and B).

• Add 1ml 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.
• Observe the color change.

**Material Required:** Starch solution, two test tubes, dilute iodine solution.
**Observations:** In test tube A \( \rightarrow \) starch + saliva + iodine \( \rightarrow \) No color change. In the test tube B \( \rightarrow \) starch + iodine \( \rightarrow \) color changes to blue-black.
**Conclusion:** This activity shows that in test tube A, saliva works on starch and breaks it down. In contrast, in test tube B, starch shows a color change with iodine, indicating its presence.
The diagram 'Action of saliva on starch solution' illustrates two test tubes. Test tube (a) shows 'Starch + Saliva + Iodine' resulting in 'No Blue-black color'. Test tube (b) shows 'Starch + Iodine' resulting in 'Blue-black color'.
In simple words: This activity demonstrates that saliva contains enzymes that break down starch, as shown by the absence of a blue-black color change with iodine when saliva is present.

Exam Tip: The iodine test for starch is crucial here. A blue-black color confirms starch presence, while no color change (or a yellow-brown color) indicates starch breakdown.

 

Activity 6.4.
Answer: **Aim:** To show presence of carbon dioxide in exhaled air.
**Procedure:**

• Take some freshly prepared lime water in a test tube. Blow air through this lime water.
• Use a syringe to pass air through some fresh lime water taken in another test tube. Lime water turns milky after some time.

**Material Required:** Test tube, freshly prepared lime water, delivery tube, syringe.
**Observation:** Limewater turns milky in test A and in test B it turns milky after some time.
The diagram shows two test tubes with lime water. Setup (a) illustrates 'Air being passed into lime water with a pichkari/syringe'. Setup (b) shows 'Air being exhaled into lime water' through a tube from a mouth.
In simple words: This activity uses limewater to show that exhaled breath contains more carbon dioxide than regular air, as it turns milky faster.

Exam Tip: The reaction of carbon dioxide with limewater (calcium hydroxide) to form calcium carbonate (milky precipitate) is a standard test for \( CO_2 \).

 

Activity 6.5.
Answer: **Aim:** To show that anaerobic respiration produces carbon dioxide.
**Procedure:** Take some fruit juice or sugar solution and add some yeast to this. Take this mixture in a test tube fitted with a one-holed cork. Fit the cork with a bent glass tube. Dip the free end of the glass tube into a test tube containing freshly prepared lime water.
**Observation:** The limewater becomes cloudy, indicating that carbon dioxide is a product of fermentation in this activity.
In simple words: Yeast breaking down sugar produces carbon dioxide, which turns limewater milky, demonstrating anaerobic respiration.

Exam Tip: This experiment demonstrates fermentation (anaerobic respiration), which produces ethanol and carbon dioxide from sugar, clearly showing the release of \( CO_2 \).

 

Activity 6.6.
Answer: **Aim:** To observe breathing rate in fish and compare with humans.
Observe the fish in an aquarium. Notice how it opens and closes its mouth and its gill-slits. Count how many times it does this in a minute and compare it to your own breathing rate.
**Observation:** Fish breathe much quicker than humans do.
In simple words: Fish breathe faster than humans because they need to extract oxygen from water, which has less oxygen than air.

Exam Tip: The difference in breathing rates reflects the availability of oxygen in the environment; aquatic organisms typically need to process more water to get sufficient oxygen.

 

Activity 6.7.
Answer: **Aim:** To determine the normal range of haemoglobin count in humans.
Visit a local health center to learn about the typical haemoglobin levels for people, including children, adult men, and women.
**Observation:** Typically, men have higher haemoglobin levels than women, and children tend to have the lowest levels.
In simple words: Haemoglobin levels differ: men usually have more than women, and children have the least.

Exam Tip: Hemoglobin is crucial for oxygen transport. Factors like age, gender, and health status can influence its levels, which are important indicators of health.

 

Activity 6.8.
Answer: **Aim:** To show the process of transpiration.
**Material Required:** Two small pots, soil, plant, stick, plastic sheet.
**Procedure:** 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.
**Observation:** On the pot with the plant, tiny drops of water are visible on the plastic sheet covering it. However, no water droplets appear on the plastic sheet covering the pot with a stick.
**Conclusion:** This experiment demonstrates that living plants absorb water from the soil, which then moves to their leaves. Water is lost from the leaves through a process called transpiration.
The diagram shows two potted setups. Pot (a) contains a living plant with a plastic bag covering the soil and plant, and water droplets are visible inside the bag. Pot (b) contains a wooden stick, with a plastic bag covering the soil and stick, but no water droplets are seen inside the bag.
In simple words: This activity shows that plants release water vapor through their leaves (transpiration), unlike a non-living stick, proving they absorb and move water.

Exam Tip: The control setup (pot with a stick) is vital to confirm that the observed water droplets are indeed from plant transpiration and not from soil evaporation.

 

Question 1. The kidneys in human beings are a part of the system for –
(a) nutrition
(b) respiration
(c) excretion
(d) transportation
Answer: (c) excretion
In simple words: The kidneys are part of the body's system for getting rid of waste products.

Exam Tip: Recall that the kidneys filter blood to remove metabolic wastes and excess water, forming urine, which is the core function of excretion.

 

Question 2. The xylem in plants are responsible for –
(a) transport of water
(b) transport of food
(d) transport of oxygen
Answer: (a) transport of water
In simple words: Xylem in plants is mainly responsible for carrying water.

Exam Tip: Differentiate xylem from phloem; xylem is for water and minerals (upwards), while phloem is for food (bidirectional).

 

Question 3. The autotrophic mode of nutrition requires –
(a) carbon dioxide and water
(b) chlorophyll
(c) sunlight
(d) All of the options
Answer: (d) All of the options
In simple words: Autotrophic nutrition needs carbon dioxide, water, chlorophyll, and sunlight. Therefore, all of the options are correct.

Exam Tip: Remember the basic requirements for photosynthesis: water, carbon dioxide, sunlight, and chlorophyll. All are essential.

 

Question 4. The breakdown of pyruvate to give carbon dioxide, water and energy takes place in –
(a) cytoplasm
(b) chloroplast
(c) mitochondria
(d) nucleus
Answer: (c) mitochondria
In simple words: Pyruvate is broken down to release carbon dioxide, water, and energy within the mitochondria.

Exam Tip: Associate the complete oxidation of pyruvate (and thus most ATP production) with the mitochondria, which are often called the "powerhouses" of the cell.

 

Question 5. How are fats digested in our bodies? Where does this process take place?
Answer: Fats are broken down in the small intestine. The liver produces bile, which breaks down large fat particles into smaller ones, a process known as emulsification. Bile also creates an alkaline environment, which allows the pancreatic enzyme lipase to further digest fats into fatty acids. This alkaline setting is necessary for lipase to function properly.
In simple words: Fats are digested in the small intestine. Bile from the liver breaks down large fat globules (emulsification), and then pancreatic lipase enzyme further breaks them into fatty acids in an alkaline environment.

Exam Tip: Emphasize the role of bile in emulsification (physical breakdown) and lipase in chemical digestion, both primarily occurring in the small intestine.

 

Question 6. What is the role of saliva in the digestion of food?
Answer: Saliva, released in our mouth, contains enzymes like salivary amylase. This enzyme begins to break down starch into simpler sugars.
In simple words: Saliva starts starch digestion in the mouth using salivary amylase, breaking it into smaller sugar molecules.

Exam Tip: Remember that salivary amylase initiates carbohydrate digestion (starch) in the mouth, but its activity is short-lived in the acidic stomach environment.

 

Question 7. What are the necessary conditions for autotrophic nutrition and what are its by products?
Answer: For autotrophic nutrition to take place, the necessary conditions are that light, carbon dioxide, and water should reach a cell containing chlorophyll. Water first splits to release oxygen and hydrogen. This process is called photolysis of water. Hydrogen then combines with carbon dioxide to form glucose. The by-product of autotrophic nutrition is oxygen, which is released through stomata.
In simple words: For plants to make their own food, they need light, carbon dioxide, water, and chlorophyll. Water breaks down, then hydrogen joins with carbon dioxide to make glucose. Oxygen is left over and released.

Exam Tip: Remember the four key requirements for autotrophic nutrition (light, CO2, H2O, chlorophyll) and the main by-product (oxygen).

 

Question 8. What are the differences between aerobic and anaerobic respiration? Name some organisms that use the anaerobic mode of respiration.
Answer:
Aerobic respiration:
• It takes place in the presence of oxygen.
• Its end products are carbon dioxide and water.
• More energy is released.
• It happens in the cytoplasm and mitochondria.
• There is complete oxidation of glucose.
Anaerobic respiration:
• It takes place in the absence of oxygen.
• Its end products are ethanol and carbon dioxide.
• Less energy is released.
• It happens only in the cytoplasm.
• There is incomplete oxidation of glucose.
Some organisms that use the anaerobic mode of respiration are yeast and bacteria.
In simple words: Aerobic respiration uses oxygen, making lots of energy with carbon dioxide and water. Anaerobic respiration doesn't use oxygen, making less energy with ethanol or lactic acid. Yeast and bacteria use the anaerobic type.

Exam Tip: Clearly differentiate between the presence/absence of oxygen, energy yield, and final products for both types of respiration.

 

Question 9. How are alveoli designed to maximise the exchange of gases?
Answer: The alveoli are present at the terminal ends of bronchioles. They are balloon-shaped structures which increase the surface area for the exchange of gases and are richly supplied with blood vessels to take the oxygen to different cells.
In simple words: Alveoli are like tiny balloons at the end of air tubes in our lungs. Their shape gives them a big surface, and they have lots of blood vessels, which helps them swap gases like oxygen and carbon dioxide very well.

Exam Tip: Focus on the three key features of alveoli for gas exchange: large surface area, thin walls, and rich blood supply.

 

Question 10. What would be the consequences of a deficiency of haemoglobin in our bodies?
Answer: Haemoglobin is a red pigment present in our blood that carries oxygen to all parts of the body. If there is a deficiency of haemoglobin, then the amount of oxygen reaching our body cells will decrease. This may lead to the release of less energy in our body, which causes a disease called anaemia. Shortness of breath, tiredness, and weakness are common symptoms of anaemia.
In simple words: Haemoglobin in blood carries oxygen. If it's low, less oxygen gets to cells, meaning less energy. This causes anaemia, with symptoms like being out of breath, tired, and weak.

Exam Tip: Link haemoglobin directly to oxygen transport and energy production, explaining how its deficiency leads to anaemia and its symptoms.

 

Question 11. Describe double circulation in human beings. Why is it necessary?
Answer: The human heart consists of two sides: right and left. The right side of the heart receives de-oxygenated blood from the cells and tissues and sends it for purification to the lungs. The left side of the heart receives oxygenated blood from the lungs, which is then pumped to all parts of the body through blood vessels. This is known as double circulation. The energy demands of human beings are very large, so separating oxygenated and deoxygenated blood is essential to meet this energy demand.
In simple words: Our heart works in two loops. One loop sends oxygen-poor blood to the lungs to pick up oxygen. The other loop sends oxygen-rich blood from the lungs to the body. This separation is vital because our bodies need a lot of energy.

Exam Tip: Clearly explain both pulmonary and systemic circulation loops and emphasize that separation ensures efficient oxygen delivery for high energy needs.

 

Question 12. What are the differences between the transport of materials in xylem and phloem?
Answer:
Transport in Xylem:
• Water and mineral salts are transported.
• The transport is generally passive.
• Vessels and tracheids are dead cells.
Transport in Phloem:
• Food in aqueous form is translocated.
• Sieve tubes and companion cells are living cells.
In simple words: Xylem moves water and minerals from roots up, usually without using energy, and is made of dead cells. Phloem moves food (sugars) around the plant, uses living cells, and needs energy.

Exam Tip: Focus on the type of material transported, energy requirement, and the nature of cells (living/dead) when comparing xylem and phloem.

 

Question 13. Compare the functioning of alveoli in the lungs and nephrons in the kidneys with respect to their structure and functioning.
Answer:
Alveoli:
• It is the structural and functional unit of lungs.
• It is thin walled, has a large surface area, and is richly supplied with blood vessels.
• It removes carbon dioxide from the blood.
Nephron:
• It is the structural and functional unit of kidneys.
• It is thin walled, has a large surface area, and is richly supplied with blood vessels.
• It removes nitrogenous wastes from the blood.
In simple words: Alveoli in lungs and nephrons in kidneys are both tiny, thin, and have lots of blood vessels to help them do their jobs. Alveoli remove carbon dioxide from blood, while nephrons remove nitrogenous waste.

Exam Tip: Highlight the similarities (thin walls, large surface area, rich blood supply) and key differences in their specific functions (gas exchange for alveoli, waste filtration for nephrons).

 

Gujarat Board Class 10 Science Life Processes Additional Important Questions and Answers

 

Very Short Answer Type Questions

 

Question 1. What is the mode of nutrition when an organism uses simple substances like CO2 and water to prepare food inside the body?
Answer: Autotrophic.
In simple words: When an organism uses simple things like carbon dioxide and water to make its own food, that's called autotrophic nutrition.

Exam Tip: Autotrophic nutrition is characteristic of plants and other organisms that produce their own food using simple inorganic substances.

 

Question 2. What are enzymes?
Answer: Enzymes are bio-catalysts which help in faster biochemical processes.
In simple words: Enzymes are special helpers in our bodies that make chemical reactions happen much faster.

Exam Tip: Remember that enzymes are proteins that act as biological catalysts, speeding up metabolic reactions without being consumed.

 

Question 3. What is the process by which a source of energy (food) is transferred from outside the body to inside of an organism?
Answer: It is the process by which a source of energy (food) is transferred from outside the body to inside of an organism.
In simple words: This is about how living things get food energy from outside their bodies into their cells.

Exam Tip: This refers to the fundamental process of nutrition, where organisms obtain and process nutrients for energy and growth.

 

Question 4. What are life processes?
Answer: All processes that perform the maintenance functions of living organisms are called life processes.
In simple words: Life processes are all the important things living beings do to stay alive and keep their bodies working.

Exam Tip: Key life processes include nutrition, respiration, transport, and excretion, all essential for an organism's survival.

 

Question 5. Which are the most common chemical reactions in a body?
Answer: Oxidation-reduction reaction.
In simple words: The most common chemical changes in our bodies involve oxidation and reduction reactions.

Exam Tip: Redox reactions are fundamental to energy metabolism, such as in cellular respiration and photosynthesis.

 

Question 6. Name an enzyme secreted by salivary glands as well as pancreas.
Answer: Amylase.
In simple words: Amylase is the enzyme that comes from both your salivary glands and your pancreas.

Exam Tip: Amylase is crucial for carbohydrate digestion, breaking down starches into simpler sugars in both the mouth and small intestine.

 

Question 7. In what form is food energy stored in plants and animals?
Answer:
1. Plants - Starch
2. Animals - Glycogen.
In simple words: Plants store their energy as starch, while animals keep theirs as glycogen.

Exam Tip: Starch and glycogen are both complex carbohydrates (polysaccharides) that serve as energy storage molecules in different organisms.

 

Question 8. Name the process by which energy is obtained by a living organism.
Answer: Respiration.
In simple words: Living things get energy through a process called respiration.

Exam Tip: Respiration involves breaking down glucose to release energy, which is then used for various cellular activities.

 

Question 9. What is peristaltic movement?
Answer: The rhythmic contraction and relaxation movement of the alimentary canal is called peristaltic movement.
In simple words: Peristaltic movement is the wavy muscle action that pushes food along inside your gut.

Exam Tip: Peristalsis is an involuntary process essential for moving food through the digestive tract from the esophagus to the intestines.

 

Question 10. In desert plants the stomata remain closed during the day and open at night. How do these plants photosynthesize?
Answer: Desert plants take up \( CO_2 \) at night and prepare an intermediate which is acted upon by the energy absorbed by the chlorophyll during the day.
In simple words: Desert plants open their stomata at night to take in carbon dioxide. This carbon dioxide is then stored and used during the day with stored sunlight energy to make food.

Exam Tip: This adaptation, known as CAM photosynthesis, helps desert plants conserve water by minimizing water loss during the hot day.

 

Question 11. Why is nitrogen essential for plants?
Answer: It is required for the synthesis of proteins and other compounds.
In simple words: Plants need nitrogen to build proteins and other important parts inside them.

Exam Tip: Nitrogen is a crucial macronutrient for plants, involved in the formation of DNA, RNA, chlorophyll, and amino acids.

 

Question 12. Name the intermediate 3-carbon molecule formed from six-carbon molecule of glucose during respiration.
Answer: Pyruvate.
In simple words: When glucose breaks down during respiration, it first turns into a 3-carbon molecule called pyruvate.

Exam Tip: Pyruvate is the end product of glycolysis, the first stage of both aerobic and anaerobic respiration.

 

Question 13. What is the site in cells where glucose is converted into 3-carbon molecule of pyruvate?
Answer: Cytoplasm.
In simple words: Glucose changes into pyruvate in the cytoplasm of a cell.

Exam Tip: Glycolysis, the process of converting glucose to pyruvate, takes place in the cytoplasm of all cells.

 

Question 14. Why are the rings of cartilage present in the air tube Trachea?
Answer: Rings of cartilage prevent the trachea from collapsing.
In simple words: The cartilage rings in your windpipe keep it open and stop it from flattening.

Exam Tip: These C-shaped cartilage rings are vital for maintaining an open airway, ensuring continuous airflow to and from the lungs.

 

Question 15. What products are formed during respiration in our muscles when there is less supply of oxygen?
Answer: Lactic acid.
In simple words: When your muscles don't get enough oxygen during exercise, they make lactic acid.

Exam Tip: Lactic acid accumulation is responsible for muscle fatigue and soreness after intense physical activity when oxygen supply is insufficient.

 

Question 16. Why is more energy released in aerobic respiration than in anaerobic respiration?
Answer: It is because complete oxidation of glucose takes place in aerobic respiration and incomplete oxidation in anaerobic respiration.
In simple words: Aerobic respiration makes more energy because it fully breaks down glucose, while anaerobic respiration only partially breaks it down.

Exam Tip: The complete breakdown of glucose in the presence of oxygen (aerobic) yields significantly more ATP (energy) compared to the partial breakdown without oxygen (anaerobic).

 

Question 17. Where is water absorbed in the digestive system?
Answer: Water is absorbed by the villi of the large intestine. Some water is also absorbed by the walls of the large intestine.
In simple words: Most water is absorbed in the large intestine, particularly by tiny finger-like structures called villi there.

Exam Tip: While some water absorption occurs in the small intestine, the large intestine is primarily responsible for absorbing the majority of water and compacting waste.

 

Question 18. What are the two functions of the kidneys?
Answer: Excretion and osmoregulation.
In simple words: Kidneys do two main jobs: they remove waste from your blood (excretion) and they control the balance of water and salts in your body (osmoregulation).

Exam Tip: Understanding these two functions highlights the kidneys' critical role in maintaining homeostasis in the body.

 

Question 19. Name the muscles of the stomach which regulate the release of food from the stomach to the small intestine.
Answer: Sphincter muscle.
In simple words: The sphincter muscle in your stomach controls when food moves into your small intestine.

Exam Tip: The pyloric sphincter specifically regulates the flow of chyme from the stomach into the duodenum, ensuring proper digestion.

 

Question 20. Name two organisms that break down food outside the body and then absorb it.
Answer: Fungi - bread mould, yeast, mushroom (Saprophytes).
In simple words: Fungi like bread mould, yeast, and mushrooms break down their food outside their bodies and then soak it up.

Exam Tip: These organisms are called saprophytes; they play a vital role as decomposers in ecosystems.

 

Question 21. What is the impact of leakage or loss of blood upon the pressure?
Answer: Blood pressure decreases.
In simple words: If blood leaks or is lost from your body, your blood pressure will go down.

Exam Tip: A significant decrease in blood volume directly leads to a drop in blood pressure, potentially causing shock.

 

Question 22. Name the respiratory pigment in higher animals.
Answer: Haemoglobin.
In simple words: Haemoglobin is the special color in the blood of bigger animals that helps them breathe.

Exam Tip: Haemoglobin's ability to bind reversibly with oxygen is crucial for efficient oxygen transport throughout the body.

 

Question 23. Name the blood vessel which carries blood away from the heart for purification.
Answer: Pulmonary artery.
In simple words: The pulmonary artery takes blood away from the heart to the lungs to get oxygen.

Exam Tip: Remember that arteries generally carry oxygenated blood, but the pulmonary artery is an exception, carrying deoxygenated blood to the lungs.

 

Question 24. What is lymph?
Answer: It is an extracellular fluid used in transportation.
In simple words: Lymph is a clear fluid outside cells that helps carry things around the body.

Exam Tip: Lymph is part of the lymphatic system, playing roles in immune function, fluid balance, and fat absorption.

 

Question 25. What is the full form of ATP?
Answer: Adenosine Triphosphate.
In simple words: ATP stands for Adenosine Triphosphate, which is like the energy currency of our cells.

Exam Tip: ATP is the primary energy currency used by all cells for metabolic processes, powering everything from muscle contraction to active transport.

 

Short Answer Type Questions

 

Question 1. Name two parasitic plants and animals.
Answer:
Parasitic plants - Cuscuta and Orchids
Parasitic animals - Lice, leech, tapeworm
In simple words: Cuscuta and orchids are plants that live off other plants. Lice, leeches, and tapeworms are animals that live off other animals.

Exam Tip: Remember that parasitic organisms live on or in a host organism, benefiting themselves while harming the host.

 

Question 2. How does nutrition occur in amoeba?
Answer: Amoeba gives out pseudopodia, which fuse over the food particle, forming a food vacuole. Inside the food vacuole, complex substances are broken down into simpler ones, which then diffuse into the cytoplasm. The remaining undigested material is moved to the surface of the cell and thrown out.
In simple words: Amoeba uses its "false feet" (pseudopodia) to surround food, creating a food bubble. Inside this bubble, food is broken down and absorbed. Any leftover waste is pushed out.

Exam Tip: Visualize the steps: ingestion (pseudopodia), digestion (food vacuole), absorption (cytoplasm), and egestion (expelling waste).

 

Question 3. Draw a diagram of open and closed stomata.
Answer:

Exam Tip: Pay attention to the turgidity of the guard cells and how it influences the shape of the stomatal pore.

 

Question 4. What causes the opening and closing of stomata?
Answer: The opening and closing of stomata is a function of the guard cells. When water flows into the guard cells, they swell, causing the stomata to open. When the guard cell shrinks, the stomata close.
In simple words: Stomata open and close because of guard cells. When guard cells fill with water, they swell and open the stomata. When they lose water, they shrink and close them.

Exam Tip: Understand that the turgor pressure within guard cells, regulated by water movement, is the primary mechanism for stomatal control.

 

Question 5. Explain digestion in the mouth.
Answer: In the mouth, food is ground with the teeth. The saliva in the mouth contains an enzyme called salivary amylase. This enzyme helps break down starch into sugar.
In simple words: In your mouth, your teeth chew food into smaller pieces. Your saliva has an enzyme called salivary amylase that starts breaking down starches into sugars.

Exam Tip: Remember that both mechanical (chewing) and chemical (salivary amylase) digestion begin in the mouth, specifically for carbohydrates.

 

Question 6. Why is respiration an exothermic reaction?
Answer: It is because the energy stored in the food is released during respiration. This energy is used to synthesize ATP molecules. The ATP molecules can then be used to provide energy for the different reactions taking place in the cell.
In simple words: Respiration is exothermic because it gives off energy that was stored in food. This released energy is used to make ATP, which then powers cell activities.

Exam Tip: An exothermic reaction releases energy (often as heat), while an endothermic reaction absorbs energy. Respiration releases energy, hence it's exothermic.

 

Question 7. When is lactic acid formed in our muscles?
Answer: Lactic acid (a three-carbon compound) forms in our muscle cells when there is insufficient oxygen. The build-up of lactic acid in our muscles during sudden activity causes cramps.
In simple words: Lactic acid forms in muscles when they don't get enough oxygen, like during hard exercise. This build-up causes muscle cramps.

Exam Tip: Lactic acid fermentation is an anaerobic process that allows muscles to continue producing ATP for a short time when oxygen is scarce.

 

Question 8. What is the range of pH in the small intestine and stomach respectively?
Answer: pH in the small intestine is greater than 7 (basic or alkaline). pH in the stomach is less than 7 (acidic medium).
In simple words: The small intestine has a pH above 7, so it's basic, while the stomach has a pH below 7, meaning it's acidic.

Exam Tip: Remember these pH ranges are crucial for the optimal functioning of different digestive enzymes in each organ.

 

Question 9. Name the glands associated with the common duct in the digestive system. Also name their secretions.
Answer:
Liver - Secretes bile juice.
Pancreas - Secretes pancreatic juice which contains amylase, lipase, and trypsin.
In simple words: The liver makes bile, and the pancreas makes pancreatic juice (with amylase, lipase, and trypsin). Both of these go into the digestive system through a shared tube.

Exam Tip: The liver and pancreas are accessory digestive organs, and their secretions are vital for chemical digestion in the small intestine.

 

Question 10. Write two important functions of transpiration in plants.
Answer: Transpiration is the loss of water from stomatal pores. It regulates the temperature and also causes the suction pull due to which the upward movement of water and minerals takes place.
In simple words: Transpiration helps plants stay cool by releasing water. It also creates a pull that draws water and minerals up from the roots to the leaves.

Exam Tip: Understand that transpiration aids in evaporative cooling and is the primary driving force for water and mineral transport in plants.

 

Question 11. What do the following transport:
1. Xylem?
2. Pulmonary artery?
3. Pulmonary vein?
4. Vena cava?
Answer:
1. Xylem - Transports water and minerals.
2. Pulmonary artery - deoxygenated blood to lungs.
3. Pulmonary vein - oxygenated blood to the left atrium.
4. Vena cava - brings deoxygenated blood to the right atrium of the heart.
In simple words: Xylem carries water and minerals. The pulmonary artery takes oxygen-poor blood to the lungs. The pulmonary vein brings oxygen-rich blood to the heart. The vena cava brings oxygen-poor blood from the body back to the heart.

Exam Tip: Be precise about the type of blood (oxygenated/deoxygenated) and the direction of flow for circulatory vessels, and the substances transported by plant tissues.

 

Question 12. Why are the walls of ventricles thicker and more muscular than the walls of atria?
Answer: Ventricles have to apply a lot of pressure and push blood out of the heart to reach all body cells. Hence, their walls are thicker and more muscular compared to the walls of atria.
In simple words: Ventricles need stronger muscles and thicker walls because they have to pump blood with high force to the entire body, unlike atria which only pump to the ventricles.

Exam Tip: Relate the thickness of cardiac muscle walls to the amount of force needed to pump blood to different parts of the circulatory system.

 

Question 13. Write one feature which is common to each of the following pairs of terms:
1. glycogen and starch
2. chlorophyll and haemoglobin
3. gills and lungs
4. arteries and veins
Answer:
1. glycogen and starch - both are carbohydrates and stored food products.
2. chlorophyll and haemoglobin - both are pigments
3. gills and lungs - both are respiratory organs
4. arteries and veins - both are blood vessels
In simple words: Glycogen and starch are both ways to store energy. Chlorophyll and haemoglobin are both colored substances. Gills and lungs both help with breathing. Arteries and veins are both types of blood tubes.

Exam Tip: Identify the fundamental category or function that links each pair of biological terms.

 

Question 14. Explain the process of breathing.
Answer:
1. When we inhale air, the chest cavity expands, and air rushes in to fill the expanded alveoli.
2. The exchange of gases takes place in the alveoli (by diffusion).
3. When we exhale, our chest cavity contracts, and air containing carbon dioxide and water vapor is expelled out.
In simple words: Breathing involves two parts: when you breathe in, your chest expands, pulling air into your lungs. Then, in the lungs, oxygen and carbon dioxide are swapped. When you breathe out, your chest shrinks, pushing air and waste gases out.

Exam Tip: Break down breathing into two phases - inhalation and exhalation - and explain the pressure changes and muscle actions involved in each.

 

Question 15. What is residual volume?
Answer: The volume of air remaining in the lungs even after a forcible expiration is the residual volume.
In simple words: Residual volume is the air that always stays in your lungs, even after you try to breathe out as much as you can.

Exam Tip: This volume is crucial for preventing lung collapse and ensuring continuous gas exchange between breaths.

 

Question 16. Name the components of xylem and phloem.
Answer:
Xylem - Tracheids, vessels, xylem parenchyma, and xylem fibers.
Phloem - Sieve tubes, companion cells, phloem parenchyma, and phloem fibers.
In simple words: Xylem is made of tracheids, vessels, and fibers, plus parenchyma. Phloem has sieve tubes, companion cells, and also fibers and parenchyma.

Exam Tip: Remember the four main components for each tissue, noting that parenchyma and fibers are common to both, but the main conducting elements (tracheids/vessels vs. sieve tubes/companion cells) differ.

 

Question 17. What is the function of lymph?
Answer: Lymph carries digested and absorbed fat from the intestine and drains excess fluid from the extracellular space back into the blood.
In simple words: Lymph helps move absorbed fats from your gut and collects extra fluid from around cells, returning it to your blood.

Exam Tip: Emphasize lymph's dual roles in fat transport (via lacteals) and maintaining fluid balance (returning interstitial fluid).

 

Question 18. Name the components of blood.
Answer:
1. Plasma - It is the fluid in which other cells are suspended.
2. R.B.C. - Red blood cells contain haemoglobin which is responsible to carry oxygen.
3. W.B.C. - White blood cells help in killing germs.
4. Platelets - Help in blood clotting during an injury.
In simple words: Blood has four main parts: plasma (the liquid), red blood cells (carry oxygen), white blood cells (fight germs), and platelets (stop bleeding).

Exam Tip: Know the primary role of each component: plasma for transport, RBCs for oxygen, WBCs for immunity, and platelets for clotting.

 

Question 19. Give the events that occur during photosynthesis.
Answer: The following events occur during photosynthesis:
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.
In simple words: Photosynthesis involves three main steps: chlorophyll catches sunlight, light energy changes to chemical energy and splits water, and then carbon dioxide is turned into sugars.

Exam Tip: Categorize these as the initial light-dependent reactions (1 & 2) and subsequent light-independent reactions (3) of photosynthesis.

 

Question 20. Describe the digestive system.
Answer: The different parts of the digestive system are as follows:
1. Food gets digested through the mouth. It has the tongue, teeth, and the opening of the salivary gland.
2. The buccal cavity leads to the esophagus.
3. The esophagus opens into the stomach. The wall of the stomach contains gastric glands.
4. The stomach opens into the duodenum. This opening is regulated by a sphincter muscle which releases a small amount of food at a time.
5. The duodenum receives the secretions of the liver and the pancreas.
6. From the duodenum, food passes into the small intestine. The inner wall of the small intestine has many finger-like projections called villi. The villi increase the surface area and are richly supplied with blood vessels.
7. The small intestine opens into the large intestine.
8. The terminal portion of the large intestine is called the rectum that opens out through the anus.
In simple words: The digestive system starts with the mouth (teeth, tongue, saliva). Food goes down the esophagus to the stomach, which has gastric glands. Then it enters the duodenum, getting help from the liver and pancreas. Next is the small intestine with its villi for absorption, leading to the large intestine, and finally the rectum and anus for waste removal.

Exam Tip: Trace the path of food through the alimentary canal, identifying key organs, their secretions, and their specific roles in digestion and absorption.

 

Question 21. Explain the digestion in the stomach.
Answer: The gastric glands present in the stomach secrete:
1. HCI - It kills bacteria ingested with food and makes the food medium acidic so as to facilitate the action of the enzyme pepsin.
2. Pepsin - It helps to digest proteins.
3. Mucus - It protects the inner lining of the stomach from the action of HCI.
In simple words: In the stomach, glands make stomach acid (HCI) to kill germs and make the food acidic for pepsin. Pepsin breaks down proteins. Mucus protects the stomach lining from the acid.

Exam Tip: Focus on the three key secretions of the stomach (HCl, pepsin, mucus) and their distinct roles in both chemical digestion and protection.

 

Question 22. Explain digestion in the small intestine.
Answer: In the first part of the small intestine, secretions from the liver (bile) and the pancreas (pancreatic juice) are received. Bile salts break down large fat globules into smaller ones, a process called emulsification. Bile also makes the food alkaline so that pancreatic enzymes can act. Pancreatic enzymes include trypsin for digesting proteins and lipase for digesting fats. The walls of the small intestine secrete intestinal juices which finally digest the food as follows:
• Proteins \( \rightarrow \) amino acids
• Fats \( \rightarrow \) fatty acids and glycerol
• Carbohydrates \( \rightarrow \) glucose
In simple words: In the small intestine, bile from the liver breaks down fats, and pancreatic juice (with enzymes like trypsin and lipase) helps digest proteins and fats. The intestinal walls also make juices to finish breaking down proteins into amino acids, fats into fatty acids and glycerol, and carbohydrates into glucose.

Exam Tip: Highlight the roles of bile (emulsification, alkalinity), pancreatic enzymes (trypsin, lipase), and intestinal juices in the complete digestion of all three macronutrients.

 

Question 23. Give the characteristics of any respiratory surface.
Answer: Any respiratory surface, e.g., gills, skin, or alveoli, must have the following features:
• It should be thin.
• It should be moist.
• The surface area should be large.
• It should be richly supplied with blood vessels.
These features will ensure quick diffusion of gases.
In simple words: A good breathing surface, like gills or lungs, needs to be thin, wet, large, and have lots of tiny blood vessels. These things help gases move in and out quickly.

Exam Tip: Remember these four essential characteristics for efficient gas exchange, as they maximize the rate of diffusion.

 

Question 24. Give the pathway of air in the human respiratory system.
Answer:
External nostrils (Cleans and warms the air)
\( \downarrow \)
Nasal cavity
\( \downarrow \)
Internal nostril
\( \downarrow \)
Pharynx
\( \downarrow \)
Larynx (voice box)
\( \downarrow \)
Trachea (large tube having cartilaginous rings)
\( \downarrow \)
Bronchi
\( \downarrow \)
Bronchioles \( \rightarrow \) (fine tubes carrying air)
\( \downarrow \)
Alveoli (Increases the surface area for diffusion of gases)
In simple words: Air comes in through your nostrils (where it's cleaned and warmed), goes through the nasal cavity, then internal nostril, pharynx, and larynx (voice box). Next, it moves down the trachea (windpipe), then into the bronchi, which branch into smaller bronchioles, and finally reaches the alveoli where gas exchange happens.

Exam Tip: Memorize the sequential order of structures in the respiratory tract, understanding the role of each in conditioning and transporting air.

 

Question 25. Draw a labelled diagram of the transverse section of a leaf.
Answer:

Exam Tip: Label all key layers (epidermis, palisade, spongy mesophyll), structures (chloroplasts, air spaces, stomata, vascular bundles), and their respective roles in photosynthesis and gas exchange.

 

Question 28. Name the excretory organs of the human excretory system. Show all the organs with a labelled diagram.
Answer: The excretory organs in the human body are:

• A pair of kidneys
• A pair of ureters
• A urinary bladder
• A urethra

The diagram illustrating the human excretory system is provided below.
In simple words: The human body has specific organs to remove waste. These include two kidneys, two tubes called ureters, a bladder to store urine, and a urethra to release it.

Exam Tip: Remember to clearly label all major organs, arteries, and veins when drawing the human excretory system. Focus on accuracy to score well.

 

Question 29. Differentiate between arteries and veins.
Answer: Here is a comparison of the key differences between arteries and veins:

In simple words: Arteries are strong tubes carrying fresh, oxygen-rich blood from your heart to your body, usually deep inside. Veins are thinner tubes that bring used, oxygen-poor blood back to your heart, and they are closer to the skin, with small doors (valves) to stop blood from flowing backward.

Exam Tip: When differentiating, always focus on structure (wall thickness, presence of valves) and function (direction and type of blood carried) as these are the main contrasting points.

 

Question 30. Bile is made in the liver, stored in the gall bladder and passes into the small intestine. Describe the role of bile in digestion.
Answer: Bile gives an alkaline medium in the small intestine, which then assists the work of pancreatic amylase, lipase, and trypsin (protease) to break down the food. It also balances the acid that enters from the stomach.
In simple words: Bile helps make the small intestine less acidic, which allows other digestive juices to work better. It also breaks down large fat droplets into smaller ones, making them easier to digest.

Exam Tip: Remember that bile's two main functions are to emulsify fats (break them into smaller droplets) and to neutralize stomach acid, creating the optimal pH for pancreatic enzymes.

 

Question 31. Label P, Q and R in the alimentary canal above and state the function of each. Explain what happens to fat at R.
Answer: Based on the diagram of the alimentary canal:
P is the gall bladder; it keeps the bile produced by the liver.
R is the early part of the small intestine (duodenum); it assists in the full breakdown of food where digestive juices from the pancreas enter.
Q is the lower section of the small intestine; this is where digested nutrients are taken in.

At R, which is the duodenum part of the small intestine, fats are broken down (emulsified). This means large fat particles are changed into tiny droplets, making them easier for enzymes to work on.
In simple words: P is the gallbladder, storing bile from the liver. R is the small intestine's first part where pancreatic enzymes help digest food and large fats are broken into small droplets. Q is the small intestine's lower part where the body takes in nutrients.

Exam Tip: For diagrams of the digestive system, always know the names and primary roles of each organ. Pay special attention to where key substances like bile and pancreatic enzymes act.

 

Question 32. Name the organs where the following functions in humans are performed
1. Absorption of food.
2. Absorption of water
Answer:
1. Small intestine.
2. Large intestine.
In simple words: The small intestine is where most nutrients from food are taken into the body, while the large intestine's main job is to soak up water.

Exam Tip: Remember these two distinct roles for the small and large intestines. The small intestine handles nutrient absorption, and the large intestine focuses on water recovery.

 

Question 33. Name the respiratory organs of –
1. fish
2. mosquito
3. earthworm
Answer: The respiratory organs for each organism are as follows:
1. Fish: Gills
2. Mosquito: Tracheal tubes (via spiracles)
3. Earthworm: Moist skin
In simple words: Fish breathe using gills, mosquitoes use tiny tubes called tracheae that open through spiracles, and earthworms breathe through their damp skin.

Exam Tip: Different organisms have adapted unique respiratory organs based on their environment and metabolic needs. Know the specific structures for aquatic, terrestrial, and insect life forms.

 

Question 34. (a) The composition of the air inside the lungs changes during breathing.
(i) State three differences between inhaled air and the exhaled air.
(ii) Describe three features of the alveoli which assist gaseous exchange.
(b) (i) State what is meant by anaerobic respiration.
(ii) Where does anaerobic respiration occur in human?
Answer:
(a) (i) Inhaled air has a higher amount of oxygen, a lower amount of carbon dioxide, and less water vapor compared to exhaled air.
(ii) Three features of the alveoli that help with gas exchange are:

• The wall of the alveolus is very thin (one cell thick).
• There is a damp outer layer to the alveoli.
• There are many tiny alveoli, and the air within them is always refreshed.

(b) (i) Anaerobic respiration is the energy release from glucose breakdown in cells without requiring oxygen.
(ii) In human beings, anaerobic respiration occurs in muscle cells.
In simple words: (a) (i) When you breathe in, air has more oxygen, less carbon dioxide, and less moisture than when you breathe out. (ii) Alveoli help exchange gases because they have very thin walls, are moist, and there are many of them, always getting fresh air. (b) (i) Anaerobic respiration is when cells make energy from glucose without using oxygen. (ii) This happens in your muscles.

Exam Tip: For part (a)(i), quantify the differences (e.g., more/less oxygen/CO2) and mention water vapor. For (a)(ii), focus on the structural adaptations of alveoli (thin walls, large surface area, rich blood supply, moist surface). For (b)(i), emphasize the "without oxygen" aspect. For (b)(ii), remember muscle cells are the key site in humans.

 

Question 1. (a) The process of making food by green plants in the presence of sunlight, chlorophyll, water and carbon dioxide, is called photosynthesis.
(b) Various steps involved in the above reaction are:
Answer:
(a) Photosynthesis is indeed the process where green plants create their food using sunlight, chlorophyll, water, and carbon dioxide.
(b) The various steps involved in this reaction include:

• Chlorophyll absorbs light energy.
• Light energy is converted into chemical energy, and water molecules are split into hydrogen and oxygen.
• Carbon dioxide is reduced to form carbohydrates.

In simple words: (a) Photosynthesis is how green plants make their food using sunshine, water, air (carbon dioxide), and a green stuff called chlorophyll. (b) First, chlorophyll catches sunlight. Next, that light energy turns into chemical energy, and water splits into hydrogen and oxygen. Finally, carbon dioxide is changed into food (carbohydrates).

Exam Tip: When explaining photosynthesis, always mention the key ingredients (sunlight, chlorophyll, water, CO2) and the products (glucose/carbohydrates, oxygen). For the steps, describe the energy transformation and molecule splitting clearly.

 

Question 2. (a) What is the importance of stomatal pores?
(b) Where are they present?
(c) How do they open and close?
Answer:
(a) Stomata are small openings that permit the movement of gases, such as oxygen and carbon dioxide, for photosynthesis and respiration. Water also moves out through them, which is known as transpiration.
(b) These stomatal pores are found mostly on the underside of the leaf.
(c) The opening and closing of stomata are regulated by specialized guard cells. When the guard cells expand by taking in water, the stomata open. Conversely, when the guard cells contract by releasing water, the stomata close.
In simple words: (a) Stomata are tiny holes that let plants breathe in and out gases like oxygen and carbon dioxide, and also release water vapor. (b) You'll mostly find them on the bottom of leaves. (c) Tiny cells called guard cells control them: they swell to open the stomata and shrink to close them.

Exam Tip: For stomata, emphasize their dual role in gas exchange (CO2 for photosynthesis, O2 for respiration) and water regulation (transpiration). Understand the mechanism of guard cells in opening and closing them.

 

Question 3. (a) Name all the digestive enzymes present in our digestive system.
(b) Explain the process of digestion of carbohydrates, fats and proteins.
(c) Why do people complain of acidity problems on consuming too much of fats and proteins?
Answer:
(a) The digestive enzymes found in our body are: Salivary amylase, pepsin, trypsin, lipase, and pancreatic amylase.

(b) Here's how carbohydrates, fats, and proteins are digested:
Carbohydrates: These are processed by salivary amylase in the mouth, which changes complex starch into simpler sugars. If not fully broken down in the mouth, then pancreatic amylase breaks it down further to glucose in the small intestine.
Fats: Bile from the liver breaks down large fat droplets into smaller ones. This emulsified fat is then acted on by pancreatic lipase, which digests fats into fatty acids.
Proteins: Proteins are initially broken down by pepsin in the stomach to form peptones. These are later digested by trypsin from the pancreas into amino acids. Finally, enzymes in the small intestine ultimately change protein to amino acids, complex carbohydrates to glucose, and fats to fatty acids and glycerol.

(c) Foods rich in fats and proteins, when digested, release fatty acids and amino acids respectively. This results in a significant amount of acid being produced in the body, which causes acidity issues.
In simple words: (a) Our digestive system uses enzymes like salivary amylase, pepsin, trypsin, lipase, and pancreatic amylase. (b) Carbohydrates start breaking down in the mouth and finish in the small intestine. Fats are first broken into tiny droplets by bile, then digested by lipase. Proteins start in the stomach with pepsin and are fully digested in the small intestine by trypsin and other enzymes. (c) Eating too many fatty and protein-rich foods can make your body produce a lot of acid, leading to discomfort.

Exam Tip: For digestion questions, remember the specific enzymes and their roles, the organs where each nutrient type is primarily digested, and the end products of digestion for carbohydrates, fats, and proteins. Also, understand the role of accessory organs like the liver and pancreas.

 

Question 4. (a) Explain, how urine is produced in human body?
(b) What are the excretory wastes in plants?
Answer:
(a) The renal artery, carrying blood with impurities, goes to the kidney. Inside the kidney, there are tiny filtering units called nephrons, which get this blood. Wastes, along with water, are pushed out into Bowman's capsule. This happens because of the glomerulus, which is a coiled network of capillaries within the Bowman's capsule. The water and waste substances are gathered in a tubule that leads to the ureter. Following filtration, necessary and useful substances are reabsorbed back into the blood before the filtered liquid moves into the ureter. Eventually, the ureter takes the urine, containing much urea and water, to the urinary bladder for storage.
In simple words: (a) Blood with waste goes to the kidneys. Tiny filters called nephrons push out waste and water into a capsule. Most useful stuff is taken back, and the remaining waste water (urine) goes through a tube to the bladder to be stored until it's released.

(b) Excretory wastes in plants:

• The main waste from photosynthesis is oxygen, and from respiration is carbon dioxide.
• Extra water is released through transpiration.
• Plants keep waste materials in their leaves, which eventually fall off.
• Plants possess dead cell tissues where waste products can be kept, for example, gums and resin in older xylem wood.
• Waste products can also be kept in cell vacuoles.
• Plants also release certain waste substances into the surrounding soil.

In simple words: (b) Plants get rid of waste like oxygen (from making food) and carbon dioxide (from breathing). They also lose extra water through their leaves. Some waste is stored in old leaves that drop off, in dead parts of the wood (like gums), in cell storage sacs, or even released into the ground around them.

Exam Tip: For plants, remember that their waste management differs significantly from animals. Highlight oxygen and CO2 as gaseous wastes, transpiration for water, and storage in leaves, bark, or vacuoles for solid/liquid wastes.

 

Question 5. (a) Give five functions of blood.
(b) “Fishes show single circulation”. Explain.
Answer:
(a) Functions of blood:

• Plasma carries food, carbon dioxide, and nitrogenous waste in a dissolved state.
• Red blood cells transport oxygen to all cells throughout the body.
• White blood cells (WBCs) help combat infections and function as the body's defense, eliminating germs.
• Platelets assist in blood clotting, which stops leaks.
• Blood also helps keep our body temperature stable.

(b) Fish possess only two chambers in their hearts. Blood is pumped to the gills to become oxygenated, and from there it flows directly to the remaining parts of the body. Therefore, blood travels through the heart just once during each full circuit through the body.
In simple words: (a) Blood carries nutrients, waste, and oxygen, fights germs with white blood cells, helps stop bleeding with platelets, and keeps your body warm. (b) Fish have a "single circulation" because their blood goes through their heart only once per full body trip, moving from the heart to gills, then to the body, and back to the heart.

Exam Tip: When listing blood functions, aim for a comprehensive overview including transport (nutrients, gases, waste, hormones), defense, clotting, and temperature regulation. For single circulation, clearly explain the pathway of blood from the heart to gills, then body, and back to the heart without returning to the heart for a second pump.

 

Question 6. (a) Draw a sectional view of human heart and label on it, aorta, right ventricle and pulmonary vein.
(b) State the functions of the following components of transport system:
(i) Blood
(ii) Lymph
Answer:
(a) Here is a sectional view of the human heart, showing the requested labels along with others:

(b) Functions of the transport system components:
(i) Blood:

• Blood helps keep the body temperature stable.
• It transports various materials like food, water, and amino acids.
• Blood maintains immunity by fighting against germs.
• It assists in clotting in case of an injury.
• It transports oxygen to maintain energy levels throughout the body.

(ii) Lymph:

• It carries digested and absorbed fat from the intestine.
• It drains excess fluid from the extracellular space back into the blood.

In simple words: (a) The human heart pumps blood, and its chambers and major vessels like the aorta, pulmonary vein, and right ventricle are shown in the diagram. (b) Blood helps regulate body temperature, carries food and oxygen, fights illness, and stops bleeding. Lymph collects extra fluid from body tissues and transports fats.

Exam Tip: For the heart diagram, practice drawing and labeling the main chambers, valves, and major blood vessels (aorta, vena cava, pulmonary artery, pulmonary vein). For blood and lymph functions, remember their distinct but complementary roles in transport, defense, and fluid balance.

Questions On High Order Thinking Skills (Hots)

 

Question 1. (a) What is this structure called and give its state-open or closed?
(b) Where are they present?
(c) What controls the opening and closing of it?
(d) Draw the opposite figure to this.
Answer:
(a) The structure is called an open stoma (plural stomata). Its state is open.
(b) They are typically found in leaves.
(c) Their opening and closing are controlled by specialized guard cells.
(d) The opposite figure, a closed stomata, is shown in the diagram below, alongside an open one.
In simple words: (a) This is an open stomata. (b) You find them on leaves. (c) Guard cells make them open and close. (d) The diagram shows both open and closed stomata, with the closed one being the opposite.

Exam Tip: When asked to draw stomata, accurately depict the guard cells (bean-shaped), the central pore, and relevant organelles like chloroplasts and the nucleus. Ensure the difference between open and closed states is clear.

 

Question 2. (i) The organ that produces pepsin.
(ii) The alkaline medium producing organ.
(iii) It helps in absorption of digested food.
(iv) It help in absorption of water.
(v) The part that controls the exit of the waste materials.
Answer:
(i) Stomach
(ii) Liver
(iii) Villi
(iv) Large intestine
(v) Rectum
In simple words: (i) The stomach makes pepsin. (ii) The liver produces alkaline bile. (iii) Villi help absorb digested food. (iv) The large intestine helps absorb water. (v) The rectum controls waste exit.

Exam Tip: When identifying organs from a diagram, ensure your labels are precise and match the exact function described in the question. Pay attention to specific roles like enzyme production versus absorption.

 

Question 3. Three organisms ate food in the form of glucose and the end products after respiration are:.
a - ethanol + CO2
b - CO2 + H2O
c - Lactic acid + water
Explain how is this possible?
Answer: This is possible because:
(a) This occurs due to anaerobic respiration, also known as fermentation.
(b) This is a result of aerobic respiration.
(c) This happens because of anaerobic respiration taking place in muscle cells.
In simple words: Different organisms break down food in different ways. (a) Ethanol and CO2 come from breathing without oxygen (like fermentation). (b) CO2 and water come from breathing with oxygen. (c) Lactic acid and water come from breathing without oxygen in muscle cells.

Exam Tip: Distinguish clearly between aerobic and anaerobic respiration based on oxygen presence and their respective end products. Remember fermentation for ethanol and CO2, and lactic acid for anaerobic respiration in muscles.

 

Question 4. Name the following in human system:
1. Balloon like structures richly supplied with blood capillaries.
2. Prevents the back flow of blood in heart.
3. Squeeze out the water with amino acids and other wastes and separates from the blood.
4. Bring impure blood to kidney.
5. Rythmic contraction and relaxation of walls of digestive system.
Answer:
1. Alveoli
2. Valve
3. Bowman's capsule
4. Afferent artery
5. Peristalsis
In simple words: 1. Alveoli are tiny air sacs like balloons with many blood vessels. 2. Valves in the heart stop blood from flowing backward. 3. Bowman's capsule filters water, amino acids, and other wastes from the blood. 4. The afferent artery brings dirty blood to the kidney. 5. Peristalsis is the wave-like movement of the gut.

Exam Tip: For "Name the following" questions, provide the precise biological term. Ensure you understand the function of each structure or process, especially for complex terms like Bowman's capsule and peristalsis.

 

Question 5. Name the excretory wastes of the following:
1. Digestive systems
2. Kidney
3. Skin
4. Lungs
5. Plants stem
6. Leaves
Answer: The excretory wastes for each are:
1. Digestive systems: Faeces
2. Kidney: Urea
3. Skin: Sweat
4. Lungs: CO2
5. Plants stem: Resin
6. Leaves: O2, H2O and CO2
In simple words: 1. Our digestive system's waste is faeces. 2. Kidneys get rid of urea. 3. Skin excretes sweat. 4. Lungs release carbon dioxide. 5. Plant stems have waste like resin. 6. Leaves release oxygen, water, and carbon dioxide as waste.

Exam Tip: When identifying excretory wastes, think about the primary function of each organ or system and what metabolic byproducts it removes from the body or plant.

 

Question 6. Give the role of the following in plants and animals:
1. Guard cells
2. Tracheids and vessels
3. Lymph
4. Phloem
5. Bio-catalyst
Answer: The role of each component is as follows:
1. Guard cells: In plants, guard cells regulate the opening and closing of stomata, controlling gas exchange and transpiration.
2. Tracheids and vessels: In plants, tracheids and vessels are components of xylem tissue, responsible for transporting water and minerals from roots to other parts.
3. Lymph: In animals, lymph is a fluid that circulates throughout the body, carrying digested fats from the intestine, draining excess tissue fluid, and playing a role in the immune system.
4. Phloem: In plants, phloem is a vascular tissue that transports sugars (food) produced during photosynthesis from the leaves to other parts of the plant, such as roots and growing areas.
5. Bio-catalyst: A bio-catalyst (e.g., an enzyme) is a substance that speeds up biochemical reactions in both plants and animals without being consumed in the process.
In simple words: 1. Guard cells in plants open and close pores to control breathing and water loss. 2. Tracheids and vessels are plant tubes that move water and minerals. 3. Lymph in animals collects extra fluid and fats, and helps fight germs. 4. Phloem in plants moves food (sugars) from leaves to other parts. 5. Bio-catalysts (like enzymes) make chemical reactions happen faster in living things.

Exam Tip: When defining roles, specify if the component is found in plants, animals, or both. Provide a clear, concise function for each, focusing on its primary biological importance.

Practical Based Questions (Solved)

 

Question 1. Before testing leaves for the presence of starch, the green chlorophyll must be removed.
The chlorophyll can be removed by boiling the leaf in ethanol.
(i) Describe how ethanol can be boiled safely.
(ii) Suggest why the chlorophyll needs to be removed
Answer:
(i) Since ethanol is highly flammable, it must be handled with great care. A test tube with ethanol and a leaf should be placed in a beaker of water. If ethanol touches skin, it should be washed off immediately. The beaker should be placed on a tripod stand with a wire gauze. Then, a gentle flame can be used to warm the water bath, allowing the alcohol to warm and chlorophyll to be removed.
(ii) Chlorophyll must be removed because its green color would hide any color changes indicating the presence of starch, making observations difficult. This allows for careful observation of the results.
In simple words: (i) To boil ethanol safely, put the test tube with ethanol and the leaf in a beaker of water, then heat the water gently. Always be careful because ethanol can catch fire easily, and wash it off if it gets on your skin. (ii) Chlorophyll needs to be taken out so its green color doesn't hide the color changes that show if starch is there.

Exam Tip: For safety procedures, emphasize the precautions (water bath for flammable liquids) and immediate actions (washing off chemicals). For the "why" aspect, clearly link chlorophyll's color to its interference with starch test observation.

 

Question 2. A student wanted to find out if starch was present in both leaves grown in direct sunlight and leaves grown in the shade. Plan an investigation to determine if starch is present in both types of leaf.
Answer: To investigate, the student should collect both types of leaves (from sunlight and shade) and boil them individually in alcohol using a water bath to take out the chlorophyll. Next, rinse both leaves with distilled water, then place them flat on a white tile and add a few drops of iodine solution. Any part of the leaf that turns blue-black would indicate the presence of starch.
In simple words: To check for starch, take a leaf from sun and a leaf from shade. Boil each in alcohol to remove green color. Wash them, then put iodine drops on them. If a part turns blue-black, it means starch is there.

Exam Tip: When planning an experiment, always include a control (e.g., comparing a shaded leaf to a sunlit leaf). Detail each step clearly, from preparation (decolorization) to observation (iodine test result).

 

Question 3. Name the process carried out by any person that releases energy. State the balanced chemical equation that describes this process.
Answer: The process performed by any person to gain energy is known as respiration. The balanced chemical equation representing respiration is: \( C_6H_{12}O_6 + O_2 \rightarrow CO_2 + H_2O + \text{energy} \).
In simple words: People get energy through a process called respiration. This process takes sugar and oxygen, and turns them into carbon dioxide, water, and energy.

Exam Tip: When providing a chemical equation, ensure it is balanced and includes all reactants and products. Clearly state the energy release as a product of respiration.

 

Question 4. For studying the stomata pore a student want to prepare a slide and focus it under a microscope.
1. Name any two leaves one should use for this experiment.
2. Describe how a peel is plucked from the leaf
3. Name the stain used for the mount.
4. How can you avoid the air bubbles and drying of the mount?
Answer:
1. Two suitable leaves for this experiment are the Rheo leaf or lily leaf.
2. To get a peel, gently stretch the leaf's dorsal (upper) part and bend it to carefully remove a thin layer of the epidermis.
3. The stain used for the microscope slide mount is Safranin.
4. Air bubbles can be avoided by gently lowering the coverslip at an angle. To prevent the mount from drying out, glycerine should be added.
In simple words: 1. You can use a Rheo leaf or a lily leaf. 2. To get a peel, gently stretch and bend the leaf's top layer. 3. Use Safranin to stain it. 4. To avoid air bubbles, lower the coverslip slowly at an angle, and add glycerine to stop it from drying.

Exam Tip: For practical questions, remember common biological materials (Rheo/lily leaves for stomata), techniques (peeling epidermis), and reagents (Safranin stain, glycerine for mounting). Always include safety and proper technique to avoid errors like air bubbles.

 

Question 5. If you have to prove that carbon dioxide is present in air how can you show it? Plan an investigation for the set up in the lab.
Answer:
Aim: To demonstrate the presence of carbon dioxide in the air.
Materials: You will need a test tube, a syringe, freshly prepared lime water, a glass tube, and a delivery tube.
Procedure: Pour freshly prepared lime water into the test tube. Securely attach the glass tube with the syringe, and then push air through the lime water using the syringe's piston. After some time, the clear lime water will turn cloudy or milky white. This color change occurs because carbon dioxide present in the air reacts with the lime water, forming an insoluble precipitate of calcium carbonate.
In simple words: To show CO2 in air, get lime water, a test tube, and a syringe. Push air from the syringe into the lime water. The lime water will turn milky because CO2 in the air reacts with it, making a chalky substance.

Exam Tip: The classic test for carbon dioxide is using limewater (calcium hydroxide solution). Remember that the formation of a milky precipitate (calcium carbonate) indicates the presence of CO2. Clearly outline the aim, materials, and procedure in your plan.

 

Question 6. To study the respiration of germinating seeds:
(a) Name two chemicals that are kept in the test tube to absorb carbon dioxide gas released in the concial flask.
(b) Explain why the level of water in the bent tube rises in the set up A
(c) State the observation in set up B
Answer:
(a) Potassium hydroxide (KOH) and sodium hydroxide (NaOH) are two chemicals that can be used to absorb the \( CO_2 \) gas.
(b) The water level rises in this flask because the germinating seeds use oxygen for respiration, and the \( CO_2 \) produced is absorbed by the KOH solution. This creates a partial vacuum, causing the higher external atmospheric pressure to push the water up the bent tube.
(c) In set-up B, the lime water will become milky or cloudy. This happens because the germinating seeds release \( CO_2 \) gas during respiration, which reacts with the lime water.
In simple words: (a) KOH and NaOH are used to soak up the carbon dioxide. (b) The water level rises in setup A because the seeds use oxygen, and the KOH takes in the CO2, making less air inside, so outside air pressure pushes water in. (c) In setup B, the lime water turns milky because the seeds let out CO2.

Exam Tip: For respiration experiments with seeds, distinguish between the role of KOH (absorbs \( CO_2 \)) and limewater (tests for \( CO_2 \)). The rise in water level in Set-up A indicates oxygen consumption, while milky limewater in Set-up B confirms \( CO_2 \) production.

 

Question 7. A student wants to study the rate of respiration in yeast cells at different temperatures.
Predict the result and list the materials required for the set up.
Answer:
Result: Yeast cells kept at room temperature will exhibit a quicker rate of respiration and germination compared to those in hot water, as very high temperatures can denature enzymes and slow down activity.
Materials required: For this setup, you will need yeast powder, a conical flask, a cork, a delivery or bent tube, a small beaker, water, and freshly prepared lime water.
In simple words: Yeast works best at regular room temperature; too hot water will make it slower. You'll need yeast, a flask, cork, tubes, a small beaker, water, and fresh lime water.

Exam Tip: When predicting results for experiments involving biological processes and temperature, remember that enzymes have optimal temperatures. Extreme heat typically denatures enzymes, reducing or stopping their activity. Always list all necessary apparatus and chemicals.

 

Question 8. A student records the observation to study the rate of respiration in three different people. Study the data collected and answer the questions given below:

(a) Which variable is kept constant?
(b) Which variable is changed?
(c) Which reading is anomalous?
(d) Suggest one improvement in this experiment.
Answer:
(a) The time period for recording the breathing rate is kept constant at one minute.
(b) The variable that is changed is the type of activity, specifically walking, running, and climbing stairs.
(c) The reading for Person 2 climbing the stairs appears anomalous. Compared to other readings, climbing stairs should typically be more strenuous, leading to a higher breathing rate than recorded for this person.
(d) For improved results, the age of all three participants should be the same. Additionally, the speed or intensity of each activity should be carefully controlled and monitored.
In simple words: (a) The time for counting breaths (one minute) stayed the same. (b) The type of activity (walking, running, stair climbing) was changed. (c) Person 2's breathing while climbing stairs seems odd; it should be higher since climbing is hard. (d) Everyone in the test should be the same age, and they should do each activity at the same exact speed.

Exam Tip: For experimental analysis, identify controlled variables (kept constant), independent variables (changed), and dependent variables (measured). Anomalous readings often stand out against expected trends. Improvements should focus on controlling more variables for validity and reliability.

 

Question 8.
(a) Which variable is kept constant?
(b) Which variable is changed?
(c) Which reading is anomalous?
(d) Suggest one improvement in this experiment.
Answer:
(a) Time remains constant for checking the breathing rate; it is always one minute.
(b) The type of activity alters; this includes walking, running, and then climbing stairs.
(c) Person 2's stair climbing, compared to other measurements, should have been more difficult, and their breathing rate should have been faster.
(d) The age of all three individuals should have been identical for improved outcomes, and the activity's pace could have been watched.
In simple words: In this experiment, the time for measuring breathing was always one minute. The actions changed, like walking or running. Person 2's stair climbing result seemed unusual; it should have shown a higher breathing rate. For better results, all people should have been the same age, and how fast they did the activities should have been checked carefully.

Exam Tip: When analyzing experimental data, carefully identify constant and changing variables, and look for any results that seem inconsistent or unexpected.