Chapter 5 – Life Processes | Previous Year Questions | Class 10 Science CBSE

Correct Answer: (c) (ii) and (iii)

Explanation:

• (ii) Stomata closes when the plant does not need CO₂ for photosynthesis – True. No need to lose water if CO₂ is not needed.
• (iii) Water flows out of guard cells – True. Loss of water makes guard cells flaccid, causing stomatal closure.

1. Hydrochloric acid: Provides acidic medium for pepsin to act and kills bacteria.
2. Villi: Increase surface area for absorption of digested food in the small intestine.
3. Anal Sphincter: Controls the release of feces from the rectum.
4. Lipase: Enzyme that digests fats into fatty acids and glycerol.

(i) Multicellular organisms have large body sizes, so diffusion alone isn’t enough. Respiratory pigments like hemoglobin help in transporting oxygen efficiently to all body parts.

(ii) Reasons:

1. Cartilage rings in throat: Prevent trachea from collapsing during breathing.
2. Residual air in lungs: Maintains continuous gas exchange even between breaths.
3. Diaphragm flattens and ribs lift: Increases chest cavity volume, drawing air into lungs (inhalation).
4. Alveoli wall with blood vessels: Enables efficient gas exchange between air and blood.

Correct Answer: (c) (B) and (C)

Explanation:

• (B) Left atrium → left ventricle → body (True)
• (C) Right atrium receives deoxygenated blood via vena cava (True)
• (A) Pulmonary artery carries deoxygenated blood, not oxygenated (False)
• (D) Aorta receives blood from left ventricle, not directly from left atrium (False)

The process is called Translocation.

Explanation: Translocation is the movement of food (mainly sugars) from leaves to other parts via phloem.

Correct Answer: (c) (B) and (C)

Same explanation as Q4, since the options are identical.

(a) Glands in buccal cavity:

Salivary glands – Secrete saliva which contains amylase (acts on starch/carbohydrates).

(b) Organs with sphincter at exit:

Stomach and Anus

(c) (i) No mucus by gastric glands:

Stomach lining will be damaged by HCl, leading to ulcers.

(ii) No villi in small intestine:

Greatly reduced absorption of nutrients.

OR

Bile juice does not contain enzymes, but it plays vital roles in digestion:

1. Emulsifies fats – Bile salts break large fat globules into smaller ones, helping lipase work more effectively.
2. Neutralizes stomach acid – Its alkalinity creates the right pH for enzymes in the small intestine.
3. Helps absorb fats and vitamins – It aids in absorbing fatty acids and fat-soluble vitamins (A, D, E, K).

So, even without enzymes, bile is essential for fat digestion and absorption.

Correct Answer: (b) (i) Amino acids, (ii) glucose, (iii) fatty acids and glycerol

Explanation:

• Proteins → amino acids
• Carbohydrates → glucose
• Fats → fatty acids + glycerol

Water reaches the leaves by transpiration pull through xylem vessels. Roots absorb water, which moves upward due to cohesion-tension and evaporation at leaves.

(d) Translocation

Explanation: Translocation refers to the transport of soluble products (like glucose) through the phloem.

(a) During intense running, muscle cells may not get enough oxygen to meet the energy demand. As a result, they switch from aerobic respiration to anaerobic respiration.

In anaerobic respiration:

• Glucose is broken down without oxygen, producing less energy.
• It leads to the formation of lactic acid, which accumulates in muscles and causes cramps and pain.

Glucose {\overset{\text{Cytoplasm}}{\longrightarrow}} Pyruvate {\overset{\text{Muscle Cell}}{\longrightarrow}} Lactic acid + Energy

OR

(b) Other name of lymph: Tissue fluid

Functions:

1. Transports nutrients and oxygen to cells.
2. Removes metabolic waste and returns it to blood.

(a) Take two healthy potted plants, A and B of nearly the same size.

• Keep them in darkness for three days. (Destarch the plant)
• Place a watch glass containing potassium hydroxide by the side of potted plant A but not in potted plant B.
• Cover both the plants with separate bell jars and seal the bottom of the jars with Vaseline.
• Keep both the plants in sunlight for two hours.
• Pluck one leaf each from both the plants and test for the presence of starch with iodine solution.
• Observation: The leaf of the potted plant A with KOH did not turn blue-black, indicating that starch was not present. The leaf of the potted plant B turns blue.
• Conclusion: KOH absorbs CO₂ so photosynthesis did not occur in potted plant A.

OR

(b) (i) In set up (I) lime water turns milky in more time as compared to set up (II) because the air we exhaled contains high percentage of CO₂ as compared to atmospheric air.

(ii) Label diagram of Stomata Function of Stomata

1. Gas exchange: Stomata allow carbon dioxide to enter the leaf for photosynthesis and oxygen to exit.
2. Transpiration: They help in the loss of excess water vapor from the plant through evaporation.

(b) lifted ribs and flattened diaphragm

Explanation:

During inhalation:

• Ribs lift up and out
• Diaphragm contracts and flattens → more space in chest → air enters lungs

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

Explanation:

• (A) True – Aquatic organisms breathe faster because oxygen is limited in water.
• (R) False – Oxygen content in air is higher than in water. That’s why aquatic animals need to breathe more rapidly.

(b) Movement of water in and out of the guard cells

Explanation: Stomatal opening/closing is caused by the turgidity of guard cells, which depends on water movement.

Turgid = open; Flaccid = closed.

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

Explanation:

• Villi are rich in blood – True
• But villi help in absorption, not digestion, so the reason is incorrect.

(b) Difference in the concentration of ions between the root and the soil

Explanation: Roots actively absorb minerals, creating an osmotic gradient that causes water to move in by osmosis.

(b) Faster because the amount of dissolved oxygen in water is fairly low

Explanation: Aquatic organisms must breathe faster as water holds less oxygen compared to air.

(b) Transpiration: creates a suction force which pulls water inside the plant

Explanation: Transpiration causes a pull from leaves to roots through xylem – called transpirational pull.

(b) Transpiration and temperature regulation

Explanation: Transpiration helps in cooling the plant and maintaining leaf temperature.

(d) Assertion (A) is false, but Reason (R) is true

Explanation:

• False: Atria have thinner walls than ventricles.
• True: Ventricles need thick walls to pump blood at high pressure to body/lungs.

The plant kept in the dark could not survive longer because:

• It cannot perform photosynthesis, which is essential for producing food.
• Photosynthesis requires light to convert carbon dioxide and water into glucose and oxygen.
• Without light, the plant lacks the energy needed for this process, leading to its inability to produce the oxygen necessary for respiration.

As a result, the plant in the dark cannot sustain itself and eventually dies.

Events of photosynthesis:

1. Absorption of light by chlorophyll
2. Splitting of water into H₂ and O₂
3. Conversion of light energy to chemical energy (ATP and NADPH)
4. Reduction of CO₂ to carbohydrates

(i) Paramecium obtains food by holozoic nutrition. It uses cilia to sweep food particles into its oral groove, then forms a food vacuole for digestion.

(ii) Roles:

1. Hydrochloric acid: Creates acidic pH for pepsin action, kills microbes
2. Trypsin: Digests proteins in the small intestine
3. Muscular stomach walls: Churn food and mix digestive juices
4. Salivary amylase: Converts starch to maltose in the mouth

(a) The action of saliva on food can be demonstrated through a simple activity:

• Take two test tubes, A and B.
• In test tube A, add one teaspoon of boiled rice.
• In test tube B, add one teaspoon of boiled rice that has been chewed for 3 to 5 minutes.
• Add 3.4 mL of water to both test tubes.
• Add a few drops of iodine solution to each test tube.

Results:

• In test tube A, the rice changes colour due to the absence of enzymes.
• In test tube B, there is no colour change because the amylase enzyme in saliva breaks down the starch into simple sugars.

(b) Bile juice plays a crucial role in digestion:

1. It breaks down fats into fatty acids, making them easier to absorb.
2. Bile also provides an alkaline fluid that neutralises the acidic food from the stomach.

Lymph

Functions:

1. Transports nutrients and oxygen to cells
2. Collects waste and returns it to bloodstream

(a) If xylem is removed → No water transport from roots to leaves → plant wilts and dies

(b) If bleeding occurs → Platelets form clots to stop bleeding and prevent infection

(i) Double circulation:

Blood passes through the heart twice during one complete cycle:

1. Pulmonary circulation – Heart → Lungs → Heart
2. Systemic circulation – Heart → Body → Heart

(ii) Importance:

1. Prevents mixing of oxygenated & deoxygenated blood
2. Ensures high oxygen supply – critical for high-energy needs of birds and mammals

(i) Renal Artery – Brings oxygenated blood with waste (like urea) to kidneys

(ii) Urethra – Removes urine from the body

(iii) Glomerulus – Filters blood in nephron

(iv) Tubular part – Reabsorbs useful substances and secretes waste into urine

Leaves of a plant assist in excretion in the following ways:

• Stomata: Most carbon dioxide is released through tiny openings called stomata in the leaves.
• Transpiration: Plants lose excess water through a process known as transpiration, which is the evaporation of water from the leaf surface.
• Waste Storage: Many waste products are stored in leaves, which are eventually shed, allowing the plant to excrete these materials.

(d) a fungi, Rhizopus

Explanation: Rhizopus uses extracellular digestion – releases enzymes outside and then absorbs nutrients.

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

Explanation: This is incorrect – water is absorbed in the large intestine, not in villi of the small intestine.

(A) Vena Cava:

• Transports deoxygenated blood
• Path: Body → Right Atrium of heart

(B) Pulmonary Artery:

• Transports deoxygenated blood
• Path: Right Ventricle → Lungs

(A) ATP role: Stores and provides energy for cellular processes, including active transport, synthesis, etc.

(B) Sufficient gas exchange in plants ensured by:

• Stomata, large surface area of leaves, moist surfaces

(C) Direction of gas diffusion depends on:

• Concentration gradient of gases (O₂ and CO₂) inside and outside plant cells

(b) (i) Amylase (ii) Bile (iii) Trypsin

Explanation:

Saliva is secreted in the mouth (i) and contains the enzyme salivary amylase, which helps digest carbohydrates. The liver (ii) secretes bile to emulsify fats, breaking them into smaller globules for easier digestion. The pancreas (iii) produces pancreatic juice, which contains enzymes like trypsin for protein digestion.

(i) (b) Released CO₂

(ii) (a) Carbon dioxide

(iii) (c) Oxidation of carbon to carbon dioxide

(iv) (a) Starch

Explanation:

KOH absorbs CO₂ → Photosynthesis doesn’t occur without CO₂ → No starch formed → Iodine test remains negative.

(c) (ii) and (iv)

Explanation: Single-celled organisms rely on diffusion for gas exchange, and their entire surface is involved in food intake.

(c) Large amount of water flows out from the guard cells.

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

Explanation:

• Assertion (A) is true: Nitrogen is essential for plant growth and is absorbed primarily as nitrates (NO₃⁻) or nitrites (NO₂⁻).
• Reason (R) is also true: Soil contains these inorganic forms of nitrogen, along with other essential minerals like phosphorus.
• Since plants absorb nitrogen from the soil in these forms, R directly explains A.

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

Why it’s wrong:

• Photosynthesis requires sunlight, so the plants must be exposed to sunlight before the starch test, not after.
• The starch test is done after the experiment to check whether photosynthesis occurred (i.e., if starch was produced).

(b) Type of food consumed

Explanation:

• Deer are herbivores, and they consume plant-based food that is rich in cellulose. Plant matter takes longer to digest, so herbivores have a longer small intestine to allow more time for digestion and absorption.
• Tiger is a carnivore, and meat is easier to digest, so it has a shorter small intestine.

(a) Glucose {\overset{\text{Cytoplasm}}{\longrightarrow}} Pyruvate {\overset{\text{Muscle Cell}}{\longrightarrow}} Lactic acid + Energy

(c) ATP

Explanation:

• During cellular respiration, the energy released from the breakdown of glucose is used to synthesize ATP (Adenosine Triphosphate).
• ATP is the energy currency of the cell, used to power various biological processes.

(a) (ii) and (iv)

Explanation:

During inhalation, we lift our ribs and flatten our diaphragm (A), which enlarges the chest cavity. This creates a vacuum that pulls air into the lungs, filling the expanded alveoli. When we exhale, our ribs and diaphragm return to their normal positions, causing the chest cavity to shrink. This pushes air out of the lungs.

• The lungs always retain a residual volume of air, ensuring there is enough time for oxygen absorption and carbon dioxide release.
• This residual volume remains constant under normal conditions.

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

Explanation:

• Assertion (A) is false: Aquatic organisms actually breathe faster, not slower, because oxygen is less available in water.
• Reason (R) is true: Water contains much less dissolved oxygen than air.

(c) Filter the air that we breathe in

Explanation:

1. The mucus lining in the nasal passage traps dust, microbes, and other foreign particles, helping to clean and filter the air before it enters the lungs.
2. It also helps humidify and slightly warm the air, but filtering is the primary function.

(a) Carbon dioxide + Water

Explanation:

Carbon dioxide + Water are the end products of aerobic respiration, which requires oxygen.

If oxygen is not available (anaerobic conditions), the products are:

• In muscle cells: Lactic acid
• In yeast: Alcohol + Carbon dioxide

(b) Both have thin and moist surface for gaseous exchange

Explanation:

• Both gills in fish and lungs in humans are adapted for efficient gas exchange.
• They share the characteristic of having a thin and moist surface, which facilitates the diffusion of oxygen and carbon dioxide.

(c) Percentage of carbon dioxide is more in the exhaled air.

Explanation:

The diagram shows a person blowing air (exhaling) into lime water. Lime water is a test for carbon dioxide. When CO₂ is bubbled through lime water, it reacts to form calcium carbonate, which turns the lime water milky.

This experiment is a classic demonstration used to show that exhaled air contains more CO₂ than inhaled air, as the lime water only turns milky after the person breathes into it, not before.

So, it helps to conclude that exhaled air has a higher concentration of carbon dioxide.

(a) Keep oxygenated blood from mixing with deoxygenated blood

Explanation:

• The right side of the heart handles deoxygenated blood (from the body to the lungs), and the left side handles oxygenated blood (from the lungs to the body).
• The separation ensures efficient circulation and maximum oxygen delivery, especially important for warm-blooded animals like humans that have high energy needs.

(a) The energy needs of the buds to grow

Explanation:

• In spring, buds begin to grow and develop into new leaves or flowers.
• To support this growth, stored sugars (mainly in the form of starch converted to glucose) from the roots or stem are transported to the buds to provide energy through cellular respiration.

(d) Transpiration

Explanation:

• Transpiration is the process of water evaporation from the leaves.
• This creates a suction force (transpiration pull) that helps in the upward movement of water through the xylem in tall trees.

(b) Capillaries

Explanation: Capillaries are the thinnest blood vessels with one-cell-thick walls, allowing easy exchange of gases, nutrients, and waste between blood and tissues.

(d) (i), (ii) and (iii).

Explanation

Blood vessel A represents the pulmonary artery, while blood vessel B signifies the pulmonary vein.

The key functions of these blood vessels are:

• Pulmonary artery: Carries deoxygenated blood from the right ventricle of the heart to the lungs for oxygenation.
• Pulmonary vein: Transports oxygen-rich blood from the lungs to the left atrium of the heart.

(b) Sieve tubes and companion cells

Explanation:

• Sieve tubes: Main conducting elements in phloem that transport food (mainly sucrose).
• Companion cells: Help in the functioning and loading/unloading of materials into sieve tubes by providing energy and support.

(c) In passing the waste products in the dialysing solution

Explanation: The semi-permeable membrane allows waste products like urea and excess salts to pass from the blood into the dialysing solution, mimicking the filtration process of kidneys.

(c) To reabsorb essential nutrients from the blood.

Explanation: The artificial kidney does not reabsorb nutrients. It only filters out waste and excess fluid. Reabsorption is a function of the real nephron tubules, not the dialysis machine.

(a) Urea and excess salts

Explanation: These are the waste materials removed from the blood during dialysis.

(c) Tubules

Explanation: The proximal and distal convoluted tubules reabsorb water, glucose, amino acids, and some salts back into the blood after filtration.

Absorption:

Plants absorb water from the soil through root hairs by osmosis. These hairs increase surface area and absorb water from the soil where water concentration is higher than in root cells.

Transport:

Water moves from root hairs → cortex → xylem of the root → stem → leaves via xylem vessels using:

• Root pressure
• Capillary action
• Transpiration pull (major force, caused by water loss from leaves creating suction)

If blood loss isn’t stopped:

• The person may go into shock due to reduced blood volume.
• Oxygen delivery to tissues decreases, leading to organ failure or even death in severe cases.

How the body prevents it:

• The body triggers clotting mechanisms.
• Platelets collect at the injury site and release chemicals to form fibrin threads, creating a blood clot that seals the wound.

The inner walls of the small intestine have villi, which are finger-like projections that increase surface area for absorption.

These villi contain blood vessels that absorb nutrients via diffusion or active transport into the bloodstream.

Absorption is necessary because digested food contains nutrients like glucose, amino acids, fatty acids, vitamins, and minerals which are required for energy, growth, and repair of the body.

a – Hydrochloric acid (HCl)

b – Pepsin

c – Mucus

d – HCl makes medium acidic for the activation of an enzyme pepsin.

e – Pepsin acts in an acidic medium, which breaks down proteins into peptones.

f – The mucus protects the inner lining of the stomach from the corroding action of HCl.

(a) Role in the process of digestion:

(i) Enzyme Trypsin:

• Trypsin is produced by the pancreas and acts in the small intestine.
• It helps in breaking down proteins into peptides and amino acids.

(ii) Enzyme Lipase:

• Lipase is also secreted by the pancreas.
• It helps in breaking down fats into fatty acids and glycerol.

(b) Two functions of finger-like projections (villi) in the small intestine:

1. Increase surface area for maximum absorption of digested food.
2. Contain blood capillaries to transport absorbed nutrients into the bloodstream efficiently.

(a) Function of alveoli in respiration:

• Alveoli are tiny, balloon-like structures in the lungs where gaseous exchange occurs.
• They allow oxygen from inhaled air to diffuse into the blood and carbon dioxide from the blood to diffuse out into the air to be exhaled.

(b) Reason why breathing is faster in aquatic organisms:

• Water contains much less dissolved oxygen than air.
• To meet their oxygen demands, aquatic organisms like fish must breathe faster and pump more water over their gills to extract enough oxygen.

(c) Pathway showing the breakdown of glucose:

• Glucose (6-carbon molecule) → Pyruvate (3-carbon molecule) + Energy (in cytoplasm)

Then:

• In presence of oxygen (aerobic respiration, in mitochondria):
  Pyruvate → Carbon dioxide + Water + Energy
• In absence of oxygen (anaerobic respiration in muscle cells):
  Pyruvate → Lactic acid + Energy
• In absence of oxygen (anaerobic respiration in yeast):
  Pyruvate → Ethanol + Carbon dioxide + Energy

(a) Ventricles have thicker muscular walls than atria: Because ventricles pump blood to longer distances — the right ventricle pumps to the lungs and the left ventricle pumps to the entire body. This requires more force, so their walls are thicker and more muscular than the atria, which only pump blood into the ventricles.

(b) The transport system in plants is slow: Plants lack a heart-like pumping organ. Transport relies on passive processes like diffusion, transpiration pull, root pressure, and capillary action, making it slower compared to animals.

(c) Circulation of blood in aquatic vertebrates differs from that in terrestrial vertebrates: Aquatic vertebrates like fish have single circulation — blood passes through the heart only once per cycle. Terrestrial vertebrates have double circulation — blood passes through the heart twice, which allows efficient oxygenation and higher metabolic activity.

(d) During the daytime, water and minerals travel faster through the xylem as compared to the night: Because transpiration is higher during the day due to sunlight, more water evaporates from the leaves, creating a stronger transpiration pull that draws water and minerals upward faster.

(e) Veins have valves, whereas arteries do not: Veins carry blood at low pressure and often against gravity. Valves prevent the backflow of blood. Arteries carry blood at high pressure from the heart, so backflow does not occur and valves are unnecessary.

(a) “Blood circulation in fishes is different from the blood circulation in human beings”. Justify the statement.

In fishes, blood circulation is single circulation.

• The heart has two chambers: one atrium and one ventricle.
• Blood flows: Heart → Gills (for oxygenation) → Body → Back to Heart
• Blood passes through the heart only once in a complete cycle.

In contrast, in human beings, blood circulation is double circulation:

• The heart has four chambers: two atria and two ventricles.
• Blood flows through the heart twice in each cycle – once for oxygenation and once for distribution.
• This provides efficient separation of oxygenated and deoxygenated blood, essential for warm-blooded animals with high energy needs.

(b) Describe “blood circulation” in human beings.

Humans have a double circulation system:

1. Pulmonary circulation – Deoxygenated blood from the right side of the heart is pumped to the lungs for oxygenation.
2. Systemic circulation – Oxygenated blood from the left side of the heart is pumped to all parts of the body.

The process:

1. Right atrium receives deoxygenated blood from the body.
2. It flows into the right ventricle, which pumps it to the lungs via the pulmonary artery.
3. In the lungs, blood becomes oxygenated and returns to the left atrium via the pulmonary veins.
4. Then it enters the left ventricle, which pumps it through the aorta to the rest of the body.

(a) Structure and function of the basic filtering unit of the kidney:

The basic filtering unit of the kidney is called the nephron.

Structure of nephron:

1. Bowman’s capsule – A cup-shaped structure that surrounds a bunch of capillaries called the glomerulus.
2. Glomerulus – A network of capillaries where blood filtration starts.
3. Renal tubule – A long, coiled tube connected to Bowman’s capsule, responsible for reabsorption and secretion.
4. Collecting duct – Collects the final urine from multiple nephrons.

Function of nephron:

• Filtration: Blood enters the glomerulus under pressure, and waste products, water, glucose, salts, etc., are filtered into Bowman’s capsule.
• Reabsorption: Useful substances like glucose, water, and some salts are reabsorbed from the tubule into the blood.
• Secretion: Additional wastes are secreted into the tubule.
• Final urine (mostly urea, excess salts, and water) passes into the collecting duct.

(b) Two factors on which the reabsorption of water from urine depends:

1. Amount of excess water in the body – If the body is dehydrated, more water is reabsorbed.
2. Concentration of antidiuretic hormone (ADH) – ADH regulates water reabsorption by increasing permeability of the kidney tubules.

(a) The Excretory system (urinary system) in human beings consists of a pair of kidneys, a pair of ureters, a urinary bladder and a urethra.

(b) In the kidney, the wastes are converted to urine by three processes:

(i) Ultrafiltration: A large amount of water, along with certain harmful substances like urea, uric acid, K, ammonium salts, creatinine, etc., and certain useful substances like glucose, amino acids, Na, etc., pass through glomerular capillaries and glomerular membrane into the cavity of Bowman’s capsule of nephrons under pressure.

The filtrate so formed is called nephric filtrate, which is moved towards the ureter.

(ii) Selective reabsorption: A large amount of water and sodium, a whole of glucose and amino acids, and a small amount of urea are passed back from the nephric filtrate into the blood capillaries.
It occurs either by back diffusion (i.e., water and urea) or active transport (i.e., Na, glucose, and amino acids). It generally occurs in the PCT (Proximal convoluted tubule) of nephrons.

(iii) Tubular secretion: Certain harmful chemicals like uric acid, creatinine, K, etc., are passed from blood capillaries surrounding the nephron into nephric filtrate by active transport.

It generally occurs in the DCT (Distal convoluted tubule) of nephrons.
Now, the fluid is termed as urine and is excreted out of the excretory organs.

(a) Nutrition is necessary for the human body because it provides essential nutrients required for:

• Energy production
• Growth and repair of body tissues
• Proper functioning of organs and maintenance of body processes

(b) The movement of food is caused by peristalsis — a wave-like muscular contraction and relaxation of the walls of the alimentary canal that pushes the food forward.

(c) Herbivores eat plant-based food, which is rich in cellulose and is harder to digest. They need a longer small intestine to allow more time for digestion and absorption. Whereas, Carnivores eat meat, which is easier to digest, so they have a shorter intestine.

(d) If mucus is not secreted, the hydrochloric acid (HCl) in the stomach will corrode the stomach lining, causing ulcers or damage to the tissues.

• Aquatic organisms like fish extract oxygen from water, which contains much less dissolved oxygen than air.
• As a result, they need to breathe faster to obtain sufficient oxygen to meet their energy needs.
• Terrestrial organisms, on the other hand, get oxygen from air, which has a higher concentration of oxygen, so their breathing rate is comparatively slower.

Label diagram of the human respiratory system

(A) Correct sequence of steps for oxygen-rich blood from lungs to body organs:

1. Pulmonary veins carry oxygen-rich blood from the lungs to the
2. Left atrium of the heart
3. Blood flows into the left ventricle
4. The left ventricle pumps the oxygen-rich blood into the
5. Aorta
6. From the aorta, blood is distributed to various organs and tissues of the body through a network of arteries and capillaries

(b) If blood vessels leak, blood can escape into surrounding tissues.

• This may cause internal bleeding, swelling, inflammation, and impaired oxygen and nutrient supply to affected areas.
• Continuous leakage can lead to drop in blood pressure and may become life-threatening if not treated.

Trypsin (also Lipase or Amylase – any one is correct)

Peristalsis – a wave-like muscular contraction of the walls of the alimentary canal.

(a) Functions in the human alimentary canal:

(i) Saliva – Contains amylase which breaks down starch into sugar.

(ii) HCl in the stomach – Creates an acidic medium for activation of pepsin and kills germs.

(iii) Bile juice – Emulsifies fats and neutralizes acidic chyme from stomach.

(iv) Villi – Increase surface area for absorption of digested nutrients in small intestine.

(b) Enzyme functions:

(i) Pepsin – Digests proteins into peptones.

(ii) Lipase – Breaks down fats into fatty acids and glycerol.

(1) Aerobic respiration (with oxygen) –

Glucose → CO₂ + H₂O + Energy

(2) Anaerobic respiration (without oxygen) –

• In muscle cells: Glucose → Lactic acid + Energy
• In yeast: Glucose → Alcohol + CO₂ + Energy

In the absence or shortage of oxygen, glucose is oxidized in the following ways:

1. In cytoplasm, glucose is oxidized to pyruvate and release energy.
2. In the muscles of humans, i.e., under anaerobic conditions, pyruvate breaks down to lactic acid and releases energy.
3. In yeast, i.e., during the fermentation process, pyruvate converts to ethanol while carbon dioxide releases a certain amount of energy.

(a) Two differences between xylem and phloem:

1. Creates transpiration pull, which helps in the upward movement of water and minerals from roots to leaves.
2. Cools the plant body as water evaporates from leaf surfaces.

Three types of blood vessels and one feature of each:

1. Arteries – Carry blood away from the heart; they have thick, elastic walls to withstand high pressure.
2. Veins – Carry blood toward the heart; they have valves to prevent the backflow of blood.
3. Capillaries – Connect arteries and veins; they have thin walls (one-cell thick) to allow exchange of gases, nutrients, and waste between blood and tissues.

(a) Two water-conducting tissues in plants:

1. Xylem vessels
2. Tracheids

How water enters continuously into the root xylem:

1. Water enters root hair cells by osmosis and moves from cell to cell toward the xylem.
2. Transpiration pull, root pressure, and capillary action help draw water upward through the xylem continuously.

(b) Reason for plants have low energy needs compared to animals:

1. Plants are stationary and do not perform vigorous physical activities.
2. Most plant cells perform basic functions and do not require energy for movement, coordination, or complex behaviors like animals do.

Four functions of the human heart:

1. heart pumps oxygenated blood to the body.
2. heart pumps deoxygenated blood to the lungs for oxygenation.
3. heart maintains blood pressure for continuous blood flow.
4. heart ensures separation of oxygenated and deoxygenated blood through its four chambers.

Double circulation ensures that oxygenated and deoxygenated blood do not mix, allowing efficient delivery of oxygen-rich blood to body tissues. It maintains high metabolic efficiency, which is essential for warm-blooded animals like humans.

(a) Excretion is the biological process by which waste products of metabolism (such as urea, excess salts, and water) are removed from the body.

Reason for animals should excrete waste matter: If not removed, these waste materials can become toxic and harm body tissues, leading to illness or death. Excretion helps maintain internal balance (homeostasis).

(b) A pair of kidneys are the main excretory organs in a human being. It helps excrete nitrogenous waste in the form of urea, toxins, excess salts, water-soluble vitamins, etc. and then eliminates it in the form of urine.

Substance taken in the small test tube: Potassium hydroxide (KOH)

Function: KOH absorbs carbon dioxide (CO₂) released during respiration.

Consequence of its use:

As CO₂ is absorbed by KOH, a vacuum is created in the flask, leading to a rise in the water level in the delivery tube, which confirms that CO₂ is produced during respiration.

(A) X – KOH pellets

Y – Wet germinating seeds

(B) Seeds use oxygen present in the flask and release carbon dioxide which is absorbed by potassium hydroxide. Thus, partial vacuum is created in the conical flask, as a result, water from the beaker rises in the delivery tube.

(i) Saliva – Contains salivary amylase, an enzyme that starts the digestion of starch by breaking it into sugars.

(ii) HCl in the stomach – Creates an acidic medium for activation of pepsin and kills germs.

(iii) Bile juice – Emulsifies fats and neutralizes acidic chyme from stomach.

(iv) Villi – Increase surface area of the small intestine for efficient absorption of digested nutrients into the bloodstream.

(A) Aquatic organisms obtain oxygen from water, which contains much less dissolved oxygen than air. To meet their oxygen needs, they must breathe faster than terrestrial organisms, which get oxygen more easily from air.

(B) Reason plants have low energy needs compared to animals:

• Plants are stationary and do not perform complex or energy-demanding movements.
• Their cells carry out only basic life processes, unlike animals that need energy for movement, response, and coordination.

(a) Two components of blood:

1. Red Blood Cells (RBCs)
2. Plasma

(b) Movement of oxygenated blood in the body:

• Oxygenated blood from the lungs enters the left atrium via the pulmonary veins.
• Then it flows to the left ventricle, which pumps it into the aorta.
• The aorta distributes the oxygenated blood to all parts of the body.

(c) Valves between atria and ventricles prevent backflow of blood from the ventricles to the atria during ventricular contraction.

(d) One structural difference between arteries and veins:

• Arteries have thick, elastic walls to withstand high pressure.
• Veins have thinner walls and valves to prevent backflow of blood.

(a) Name of the process: Photosynthesis

Type of nutrition:

• Autotrophic nutrition – Green plants make their own food using sunlight, carbon dioxide, and water.

Raw materials required:

1. Carbon dioxide (CO₂) – from the atmosphere
2. Water (H₂O) – from the soil
3. Sunlight – energy source
4. Chlorophyll – green pigment in leaves that captures sunlight

Chemical equation:

6CO₂ + 12H₂O → C₆H₁₂O₆ + 6H₂O + 6O₂

(b) Three events during photosynthesis:

1. Absorption of light energy by chlorophyll.
2. Conversion of light energy into chemical energy (ATP and NADPH) and splitting of water into hydrogen and oxygen.
3. Reduction of carbon dioxide to form glucose (C₆H₁₂O₆) using hydrogen.

(a) The reaction when glucose breaks down anaerobically in yeast:

Glucose (C₆H₁₂O₆) → Ethanol (C₂H₅OH) + Carbon dioxide (CO₂) + Energy

(b) Fishes take water in through their mouths and force it over the gills. Gills extract dissolved oxygen from the water and pass it into the bloodstream. Carbon dioxide from the blood diffuses out into the water and is expelled.

(c) Alveoli

Functions of alveoli:

1. Provide a large surface area for gas exchange.
2. Allow oxygen to diffuse into the blood and carbon dioxide to diffuse out.

(d) Respiratory pigment in humans: Hemoglobin

Role: Hemoglobin carries oxygen from the lungs to the body tissues and brings carbon dioxide from the tissues back to the lungs.

(a) Two components of blood:

1. Red Blood Cells (RBCs)
2. Plasma

(b) Oxygenated blood from the lungs enters the left atrium → flows into the left ventricle → pumped into the aorta → distributed to the entire body.

(c) Valves prevent the backflow of blood from the ventricles into the atria during contraction.

(d) One structural difference between arteries and veins:

• Arteries have thick, elastic walls to handle high pressure.
• Veins have thinner walls and contain valves to prevent backflow of blood.

(a) Excretion is the biological process by which waste products of metabolism (like urea, excess salts, and water) are removed from the body.

(b) Nephron

(c Diagram of human excretory system

Kidneys – (i) Form urine

Ureters – (ii) Long tubes that collect urine from the kidneys

Urinary bladder – (iii) Stores urine until it is passed out

Diffusion is insufficient in multicellular organisms like humans because:

• Large body size and complex structure mean that oxygen needs to travel long distances to reach every cell.
• Diffusion is a slow process and cannot supply oxygen efficiently to deep tissues and organs.
• Therefore, humans need a specialized respiratory and circulatory system to transport oxygen quickly and adequately throughout the body.

The vein that brings blood to the left atrium from the lungs is the pulmonary vein.

Photosynthesis is important for a number of reasons:

1. Food for all: By photosynthesis, green plants synthesize food from simple raw materials like CO₂ and H₂O. Thus, it sustains life on earth.
2. Oxygen: Oxygen released during the process of photosynthesis is needed by animals and humans for respiration. Oxygen also supports the combustion of fuels.

The balanced chemical equation involved in the process of photosynthesis is given as:

6CO₂ + 12H₂O → C₆H₁₂O₆ + 6H₂O + 6O₂

Difference between Autotrophs and Heterotrophs:

Translocation in phloem is the movement of food (mainly sucrose) from leaves (source) to other parts (sinks) of the plant.

• At the source, sucrose is actively loaded into phloem using energy (ATP).
• This draws in water by osmosis, creating high pressure.
• The pressure causes the solution to flow towards the sink.
• At the sink, sucrose is unloaded using energy, and water moves out, lowering pressure.

This pressure flow ensures food transport using energy.

(a) Anaerobic breakdown of glucose in yeast:

C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂ + Energy

(b) Mechanism by which fishes breathe in water:

• Fishes take in water through the mouth and force it over the gills.
• Gills extract dissolved oxygen from water and pass it into the bloodstream.
• Carbon dioxide from the blood diffuses out into the water.

(c) Balloon-like structures in the lungs: Alveoli

Two functions:

1. Provide a large surface area for gaseous exchange.
2. Enable diffusion of oxygen into the blood and carbon dioxide out of the blood.

(d) Respiratory pigment in humans: Hemoglobin

Role: Hemoglobin binds with oxygen in the lungs and transports it to tissues and cells throughout the body.

(a) Name of the process: Photosynthesis

Type of nutrition:

• Autotrophic nutrition – Green plants make their own food using sunlight, carbon dioxide, and water.

Raw materials required:

1. Carbon dioxide (CO₂) – from the atmosphere
2. Water (H₂O) – from the soil
3. Sunlight – energy source
4. Chlorophyll – green pigment in leaves that captures sunlight

Chemical equation:

6CO₂ + 12H₂O → C₆H₁₂O₆ + 6H₂O + 6O₂

(b) Three events during photosynthesis:

1. Absorption of light energy by chlorophyll.
2. Conversion of light energy into chemical energy (ATP and NADPH) and splitting of water into hydrogen and oxygen.
3. Reduction of carbon dioxide to form glucose (C₆H₁₂O₆) using hydrogen.

(a) Components of the transport system in human beings and their functions:

(1) Heart – Pumps blood to all parts of the body.

(2) Blood – Transports oxygen, nutrients, hormones, and waste products.

• Red blood cells (RBCs): Carry oxygen
• White blood cells (WBCs): Fight infections
• Platelets: Help in blood clotting
• Plasma: Transports nutrients, hormones, and waste

(3) Blood Vessels:

• Arteries: Carry oxygenated blood away from the heart
• Veins: Carry deoxygenated blood back to the heart
• Capillaries: Allow exchange of gases, nutrients, and waste at the tissue level

(b) How a blood clot forms when a blood vessel leaks:

When a blood vessel is damaged, platelets collect at the injury site and release clotting factors. These convert a protein called fibrinogen into fibrin, which forms a mesh that traps blood cells and forms a clot, sealing the leak and stopping further bleeding.

Translocation is the process of transport of food (mainly sucrose) from the leaves (source) to other parts of the plant (roots, stems, fruits – sinks) through the phloem.

The raw materials required are:

1. Carbon dioxide (CO₂) – from the air
2. Water (H₂O) – from the soil
3. Sunlight – as energy source
4. Chlorophyll – pigment that captures solar energy

Glucose is first broken down in the cell cytoplasm into a three-carbon molecule called pyruvate. Pyruvate is further broken down in the following ways to provide energy.

(i) Mouth

(ii) Gall Bladder

(iii) Pancreas

(iv) Large Intestine

(v) Small intestine

(a) Forms of storage:

(i) Unused carbohydrates in plants are stored as starch.

(ii) Energy derived from food in humans is stored in the form of ATP (Adenosine Triphosphate).

(b) Nutrition in the amoeba:

1. Ingestion: Amoeba uses temporary finger-like extensions of its cell surface called pseudopodia to surround and engulf the food particle.
2. Formation of food vacuole: The pseudopodia fuse around the food particle, enclosing it in a food vacuole inside the cytoplasm.
3. Digestion: Inside the food vacuole, complex substances are broken down into simpler substances by digestive enzymes.
4. Absorption: The simpler substances diffuse into the cytoplasm of the Amoeba to be used as nutrients.
5. Egestion: The undigested material is moved to the surface of the cell and expelled out of the body.

This process is an example of holozoic nutrition and is typical in unicellular organisms like Amoeba.

(i) Fine hair and mucus are present in the nasal passage:

To trap dust, germs, and other harmful particles from the air we breathe in, thus protecting the respiratory system.

(ii) Rings of cartilage are present in the throat:

The cartilaginous rings keep the trachea open and prevent it from collapsing when air passes through it.

A parasite is an organism that lives on or inside another organism (host) and derives nutrients at the host’s expense.

Examples:

• Plant parasite: Cuscuta (Amarbel)
• Animal parasite: Plasmodium (malaria-causing parasite)

Organisms that digest food outside the body and absorb it:

Examples: Fungi and bread mould

(i) Xylem – Transports water and minerals from roots to other parts of the plant.

(ii) Phloem – Transports food (sugar) from leaves to all parts of the plant.

(iii) Pulmonary vein – Carries oxygenated blood from lungs to heart.

(iv) Vena cava – Carries deoxygenated blood from body to heart.

(v) Pulmonary artery – Carries deoxygenated blood from heart to lungs.

(vi) Aorta – Carries oxygenated blood from heart to rest of the body.

In single-celled organisms, the surface area to volume ratio is large, so diffusion is fast and efficient to meet all metabolic needs. In multicellular organisms, the body is made up of many cells, and diffusion alone is too slow to transport substances over long distances. Hence, they require specialized transport systems.

(a) Digestive enzymes: It breaks down complex food molecules into simpler absorbable forms (e.g., proteins → amino acids, starch → sugars).

(b) Hydrochloric acid (HCl): It Creates an acidic medium for enzyme pepsin to function and kills bacteria in food.

(c) Villi: It is a finger-like projections in the small intestine that increase surface area for efficient absorption of nutrients into the bloodstream.

Location: Gastric glands are located in the walls of the stomach.

Function: They secrete

1. Hydrochloric acid (HCl) – creates acidic medium and kills germs.
2. Pepsin enzyme – digests proteins.
3. Mucus – protects the stomach lining from acid damage.

In Amoeba, nutrition occurs by phagocytosis: It engulfs food using pseudopodia, forming a food vacuole where digestion takes place.

In Paramoecium, food is taken in through a specialized feeding groove called the oral groove. Cilia help sweep food into this groove.

Difference: Amoeba uses pseudopodia, while Paramoecium uses cilia and a fixed feeding region.

Breathing through the nose is advisable because:

1. The nasal passage filters, moistens, and warms the air.
2. Mucus and hair in the nose trap dust and germs, preventing them from entering the lungs.

Transpiration is the loss of water vapor from the aerial parts (mainly leaves) of the plant through stomata.

Transpiration creates a transpiration pull, which helps draw water upward from the roots through the xylem, aiding in the movement of water and minerals to different parts of the plant.