Class 10: Science (In English) – Lesson 5. Life Processes
EXPLANATION & SUMMARY
🔵 Detailed Explanation
Introduction: The Essence of Life Processes
Living organisms differ from non-living things because they perform certain essential activities. These activities provide energy, remove wastes, and maintain internal balance. Collectively, these are called life processes. The primary ones discussed in this lesson are:
🔵 Nutrition
🟢 Respiration
🟡 Transportation
🔴 Excretion
💡 Concept: Without these processes, living beings cannot survive, grow, or reproduce.
🔵 Nutrition
Nutrition is the process of taking in food and converting it into usable energy.
Types of Nutrition
Autotrophic Nutrition
🌿
Carried out by green plants through photosynthesis.
Raw materials: Carbon dioxide, water, sunlight, chlorophyll.
Equation: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂
Steps:
➡️ Absorption of light by chlorophyll.
➡️ Splitting of water (photolysis).
➡️ Reduction of CO₂ to form glucose.
✔️ Importance: Provides food and oxygen for all life.
Heterotrophic Nutrition 🧠
Organisms depend on other organisms.
Types:
🔵 Holozoic: Humans, animals (ingestion, digestion, absorption, assimilation, egestion).
🟢 Saprophytic: Fungi, bacteria (feed on dead matter).
🟡 Parasitic: Depend on hosts (e.g., Cuscuta).
✏️ Note: Humans use holozoic nutrition, involving a complete digestive system.
🟢 Human Digestive System
Mouth: Teeth and saliva (amylase) begin starch digestion.
Oesophagus: Moves food by peristalsis.
Stomach: Secretes gastric juice—HCl, pepsin, mucus; digests proteins.
Small Intestine:
➡️ Liver secretes bile (emulsifies fats).
➡️ Pancreas secretes enzymes for carbohydrates, proteins, fats.
➡️ Absorption through villi into blood.
Large Intestine: Absorbs water, forms feces.
💡 Concept: Villi increase surface area for nutrient absorption.
🟡 Respiration
Respiration releases energy by breaking down glucose.
Aerobic respiration (with O₂):
Glucose → CO₂ + H₂O + Energy (38 ATP)
Anaerobic respiration (without O₂):
➡️ In yeast: Glucose → Alcohol + CO₂ + Energy
➡️ In muscles: Glucose → Lactic acid + Energy
✔️ Application: Muscle cramps occur due to lactic acid accumulation.
Human Respiratory System:
Organs: Nose, trachea, bronchi, lungs, alveoli.
Alveoli: Site of gaseous exchange. O₂ enters blood, CO₂ exits.
Transport: Oxygen carried by haemoglobin; CO₂ as bicarbonates.
✏️ Note: Breathing and respiration are different—breathing is physical, respiration is chemical.
🔴 Transportation in Humans
Circulatory System ensures distribution of nutrients, gases, and wastes.
Heart: 4 chambers (left and right atria, left and right ventricles).
Double circulation: Blood passes twice through heart per cycle, ensuring separation of oxygenated and deoxygenated blood.
Blood vessels:
🔵 Arteries: Thick walls, carry blood away from heart.
🟢 Veins: Thin walls, valves, carry blood toward heart.
🟡 Capillaries: Exchange of materials.
Lymph: Drains excess fluid, transports fats, protects against infections.
💡 Concept: Double circulation is an advanced adaptation for efficient oxygen supply.
🟢 Transportation in Plants
Xylem: Transports water and minerals via transpiration pull and root pressure.
Phloem: Transports food from leaves to all parts (translocation).
✔️ Application: Transpiration cools plants and maintains water balance.
🟡 Excretion
Excretion removes waste products formed during metabolism.
In Humans
Organs: Kidneys, ureters, bladder, urethra.
Nephron (functional unit):
➡️ Filtration in glomerulus.
➡️ Reabsorption in tubules.
➡️ Secretion of wastes.
Result: Urine (urea, salts, water).
✔️ Dialysis: Artificial purification of blood in kidney failure.
In Plants
Wastes stored in vacuoles.
Gaseous wastes released through stomata, lenticels.
Excrete resins, gums, latex as by-products.
Conclusion
Life processes such as nutrition, respiration, transportation, and excretion are vital for maintaining life. They ensure organisms obtain energy, eliminate wastes, and maintain internal balance. Without these, survival is impossible.
🟢 Summary
Nutrition: Autotrophic (photosynthesis), heterotrophic (holozoic, saprophytic, parasitic), human digestive system.
Respiration: Aerobic and anaerobic pathways, human respiratory organs, alveoli gas exchange, haemoglobin transport.
Transportation: Humans—heart, double circulation, blood vessels, lymph; Plants—xylem, phloem, transpiration pull, translocation.
Excretion: Humans—kidneys, nephrons, urine formation; Plants—vacuoles, stomata, resins.
📝 Quick Recap
🌿 Nutrition: Plants (photosynthesis), animals (holozoic).
⚡ Respiration: Aerobic vs anaerobic; energy as ATP.
🧠 Transport: Heart and vessels in humans, xylem & phloem in plants.
💧 Excretion: Kidneys in humans, vacuoles/resins in plants.
✔️ Life processes keep organisms alive and balanced.
————————————————————————————————————————————————————————————————————————————————————
QUESTIONS FROM TEXTBOOK
Question 1
The kidneys in human beings are a part of the system for
(a) nutrition
(b) respiration
(c) excretion
(d) transportation
Answer
✔️ Kidneys are part of the excretory system.
Their main function is to remove nitrogenous wastes (urea, uric acid, ammonia) from the blood.
They also maintain water–salt balance (osmoregulation) and pH balance.
Correct option: (c) excretion
Question 2
The xylem in plants are responsible for
(a) transport of water
(b) transport of food
(c) transport of amino acids
(d) transport of oxygen
Answer
✔️ Xylem conducts water and dissolved minerals from roots to aerial parts of the plant.
Transport occurs through root pressure, capillary action, and transpiration pull.
Correct option: (a) transport of water
Question 3
The autotrophic mode of nutrition requires
(a) carbon dioxide and water
(b) chlorophyll
(c) sunlight
(d) all of the above
Answer
✔️ For photosynthesis, plants require:
Carbon dioxide and water (raw materials).
Chlorophyll (pigment to trap sunlight).
Sunlight (energy source).
Correct option: (d) all of the above
Question 4
The breakdown of pyruvate to give carbon dioxide, water and energy takes place in
(a) cytoplasm
(b) mitochondria
(c) chloroplast
(d) nucleus
Answer
✔️ Pyruvate (formed in cytoplasm during glycolysis) enters mitochondria for complete oxidation in aerobic respiration.
Reaction: Pyruvate → CO₂ + H₂O + Energy (ATP).
This is known as the Krebs cycle followed by the electron transport chain.
Correct option: (b) mitochondria
Question 5
How are fats digested in our bodies? Where does this process take place?
Answer
✔️ Digestion of fats occurs mainly in the small intestine.
➡️ Steps:
Bile (from liver) emulsifies large fat globules into tiny droplets, increasing enzyme action surface.
Pancreatic lipase enzyme breaks down emulsified fats into fatty acids and glycerol.
These products are absorbed by villi into lymph vessels.
✏️ Note: No digestion of fats occurs in mouth or stomach; it is specific to small intestine.
Question 6
What is the role of saliva in the digestion of food?
Answer
✔️ Saliva plays two important roles:
Contains salivary amylase which digests starch into maltose (sugar).
Moistens and lubricates food, making swallowing easier.
💡 Concept: Salivary digestion is the first chemical step in human digestion.
Question 7
What are the necessary conditions for autotrophic nutrition and what are its by-products?
Answer
✔️ Conditions:
Carbon dioxide, water, sunlight, and chlorophyll.
✔️ Process: Photosynthesis.
Equation: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂
✔️ By-products: Oxygen (O₂) is released; glucose is formed as the main product.
Question 8
What are the differences between aerobic and anaerobic respiration? Name some organisms that use the anaerobic mode of respiration.
Answer
✔️ Differences:
Aerobic respiration: Uses O₂, occurs in mitochondria, complete breakdown of glucose, produces more ATP (38).
Anaerobic respiration: Does not use O₂, occurs in cytoplasm, incomplete breakdown of glucose, produces less ATP (2).
✔️ Organisms with anaerobic respiration: Yeast (alcoholic fermentation), certain bacteria, muscle cells during heavy exercise.
Question 9
How are the alveoli designed to maximise the exchange of gases?
Answer
✔️ Alveoli are tiny balloon-like sacs in the lungs with special adaptations:
Very thin walls for rapid diffusion.
Surrounded by dense network of capillaries.
Moist surface for efficient gas dissolution.
Large number (millions) providing vast surface area.
💡 Concept: These features ensure maximum oxygen intake and carbon dioxide release.
Question 10
What would be the consequences of a deficiency of haemoglobin in our bodies?
Answer
✔️ Haemoglobin binds and transports oxygen in blood.
➡️ If haemoglobin is deficient:
Less oxygen transported to cells.
Leads to tiredness, weakness, breathlessness.
Severe deficiency causes anaemia.
Question 11
Describe double circulation of blood in human beings. Why is it necessary?
Answer
✔️ Double circulation means blood passes through the heart twice in one complete cycle:
Pulmonary circulation: Right side → lungs → left side (oxygenation of blood).
Systemic circulation: Left side → body → right side (distribution of oxygenated blood and return of deoxygenated blood).
✔️ Necessity:
Keeps oxygenated and deoxygenated blood separate.
Ensures high efficiency of oxygen supply, vital for warm-blooded animals like humans.
Question 12
What are the differences between the transport of materials in xylem and phloem?
Answer
✔️ Differences:
Xylem: Transports water and minerals from roots to leaves, movement is unidirectional, passive process (does not require energy).
Phloem: Transports food (sugars) from leaves to other parts, movement is bidirectional, active process (requires energy).
Question 13
Compare the functioning of alveoli in the lungs and nephrons in the kidneys with respect to their structure and functioning.
Answer
✔️ Alveoli:
Structure: Tiny sacs with thin walls and rich capillary network.
Function: Exchange of O₂ and CO₂ between air and blood by diffusion.
✔️ Nephrons:
Structure: Microscopic filtration units with glomerulus and tubules.
Function: Filter blood, remove nitrogenous wastes, reabsorb useful substances, form urine.
💡 Concept: Both are structural and functional units—alveoli for respiration, nephrons for excretion.
————————————————————————————————————————————————————————————————————————————————————
OTHER IMPORTANT QUESTIONS FOR EXAMS
Question 1
Which of the following is the functional unit of kidney?
Neuron
Nephron
Alveolus
Glomerulus
Answer: 2
Question 2
In humans, which organ secretes bile?
Stomach
Pancreas
Liver
Gall bladder
Answer: 3
Question 3
Which pigment is essential for photosynthesis?
Haemoglobin
Chlorophyll
Keratin
Myoglobin
Answer: 2
Question 4
Which blood vessel carries oxygenated blood from lungs to heart?
Pulmonary vein
Pulmonary artery
Aorta
Vena cava
Answer: 1
Question 5
Which enzyme is present in saliva?
Pepsin
Amylase
Lipase
Trypsin
Answer: 2
Question 6
Which waste product is majorly excreted by humans?
Carbon monoxide
Urea
Alcohol
Starch
Answer: 2
Question 7
Which tissue transports food in plants?
Xylem
Phloem
Parenchyma
Collenchyma
Answer: 2
Question 8
What is the site of gaseous exchange in human lungs?
Bronchi
Trachea
Alveoli
Diaphragm
Answer: 3
Question 9
Which process in plants removes excess water?
Photosynthesis
Translocation
Transpiration
Respiration
Answer: 3
Question 10
In humans, double circulation is necessary to
mix oxygenated and deoxygenated blood
increase pressure of blood
separate oxygenated and deoxygenated blood
stop respiration
Answer: 3
Question 11
A: Haemoglobin is responsible for transport of oxygen in blood.
R: Haemoglobin combines with CO₂ in lungs.
Both A and R true; R is the correct explanation of A
Both A and R true; R is NOT the correct explanation of A
A true; R false
A false; R true
Answer: 3
Question 12
A: Bile emulsifies fats into small droplets.
R: Bile contains enzymes that digest starch.
Both A and R true; R is the correct explanation of A
Both A and R true; R is NOT the correct explanation of A
A true; R false
A false; R true
Answer: 3
Question 13
A: Transpiration helps in upward movement of water in plants.
R: It creates a suction force in xylem vessels.
Both A and R true; R is the correct explanation of A
Both A and R true; R is NOT the correct explanation of A
A true; R false
A false; R true
Answer: 1
Question 14
A: Anaerobic respiration produces more ATP than aerobic respiration.
R: In anaerobic respiration, glucose is incompletely oxidised.
Both A and R true; R is the correct explanation of A
Both A and R true; R is NOT the correct explanation of A
A true; R false
A false; R true
Answer: 4
Question 15
A: Nephrons filter blood in kidneys.
R: They remove nitrogenous wastes and excess salts.
Both A and R true; R is the correct explanation of A
Both A and R true; R is NOT the correct explanation of A
A true; R false
A false; R true
Answer: 1
Question 16
A: Pulmonary artery carries oxygen-rich blood.
R: Pulmonary artery arises from left ventricle.
Both A and R true; R is the correct explanation of A
Both A and R true; R is NOT the correct explanation of A
A true; R false
A false; R true
Answer: 4
Question 17
A: Villi are finger-like projections in small intestine.
R: They increase surface area for absorption of digested food.
Both A and R true; R is the correct explanation of A
Both A and R true; R is NOT the correct explanation of A
A true; R false
A false; R true
Answer: 1
Question 18
A: Oxygen diffuses from alveoli into blood due to higher concentration in alveoli.
R: Diffusion always occurs from lower to higher concentration.
Both A and R true; R is the correct explanation of A
Both A and R true; R is NOT the correct explanation of A
A true; R false
A false; R true
Answer: 3
Question 19
A: Phloem transports food bidirectionally.
R: Transport of food requires energy in plants.
Both A and R true; R is the correct explanation of A
Both A and R true; R is NOT the correct explanation of A
A true; R false
A false; R true
Answer: 1
Question 20
A: Plants excrete resins, gums, and latex as waste products.
R: Plants have kidneys for excretion.
Both A and R true; R is the correct explanation of A
Both A and R true; R is NOT the correct explanation of A
A true; R false
A false; R true
Answer: 3
🟢 Section B (Q21–26: Very Short Answers, 2 marks each)
Question 21
What is peristalsis?
Answer
Rhythmic, wave-like muscular contractions of the alimentary canal.
Pushes food forward from oesophagus to stomach and through intestines.
Question 22
Why is transpiration important in plants?
Answer
Helps in upward movement of water and minerals.
Cools plant surface and maintains water cycle.
Question 23
State the role of hydrochloric acid in stomach.
Answer
Provides acidic medium for action of enzyme pepsin.
Kills harmful bacteria in food.
Question 24
What is the difference between breathing and respiration?
Answer
Breathing: Physical process of inhalation and exhalation.
Respiration: Biochemical process of breakdown of glucose to release energy.
Question 25
Why are capillaries suited for exchange of materials?
Answer
Thin-walled and narrow, allowing diffusion of gases and nutrients.
Dense network ensures close contact with tissues.
Question 26
What is excretion in plants?
Answer
Removal of metabolic wastes like CO₂, water, resins, gums.
Occurs through stomata, lenticels, or storage in vacuoles.
🟡 Section C (Q27–33: Short Answers, 3 marks each)
Question 27
Explain the process of photosynthesis with a balanced chemical equation.
Answer
Process by which green plants make food using CO₂, water, sunlight, chlorophyll.
Steps: Light absorption, splitting of water, reduction of CO₂, glucose formation.
Equation: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂
Question 28
List three differences between arteries and veins.
Answer
Arteries: Thick walls, carry blood away from heart, high pressure.
Veins: Thin walls, carry blood to heart, valves prevent backflow.
Arteries carry oxygenated blood (except pulmonary artery), veins carry deoxygenated blood (except pulmonary vein).
Question 29
Explain the role of diaphragm in breathing.
Answer
Inhalation: Diaphragm contracts, moves downward → increases chest cavity volume → air enters lungs.
Exhalation: Diaphragm relaxes, moves upward → decreases volume → air expelled.
Question 30
Why do herbivores have a longer small intestine compared to carnivores?
Answer
Herbivores digest cellulose-rich plant food.
Require longer time and surface area for absorption.
Carnivores eat protein-rich food, digested faster, so shorter intestine.
Question 31
How does urine formation take place in nephron?
Answer
Filtration of blood in Bowman’s capsule.
Reabsorption of useful substances (glucose, water, salts).
Secretion of wastes, forming urine that passes into collecting duct.
Question 32
Give reasons:
(a) Desert plants open stomata at night.
(b) Oxygen is released during photosynthesis.
Answer
(a) To reduce water loss due to transpiration in hot day conditions.
(b) Splitting of water molecules during photosynthesis releases O₂ as by-product.
Question 33
Explain the mechanism of transport of food in phloem.
Answer
Food prepared in leaves is transported to other parts by phloem (translocation).
Movement is bidirectional.
Requires energy in form of ATP to load sucrose into sieve tubes, creating pressure gradient for flow.
Question 34
Explain the structure and working of human heart with the help of a flow sequence of blood circulation.
Answer
Human heart: Muscular organ with 4 chambers – Right atrium, Right ventricle, Left atrium, Left ventricle.
Flow sequence:
🔵 Deoxygenated blood from body → Right atrium → Right ventricle → Pulmonary artery → Lungs.
🟢 In lungs: Exchange of gases, blood becomes oxygenated.
🟡 Oxygenated blood from lungs → Pulmonary vein → Left atrium → Left ventricle → Aorta → Entire body.
Valves ensure one-way flow of blood.
Double circulation ensures separation of oxygenated and deoxygenated blood → efficient oxygen supply.
✔️ Importance: Maintains high energy output required for warm-blooded animals like humans.
Question 35
Describe the human respiratory system. Explain the process of breathing in detail.
Answer
Organs: Nose → Pharynx → Trachea (windpipe with C-shaped cartilage rings) → Bronchi → Bronchioles → Alveoli.
Breathing process:
➡️ Inhalation: Diaphragm contracts & moves down, ribs move outward → chest cavity expands → air rushes in.
➡️ Exhalation: Diaphragm relaxes & moves up, ribs fall inward → chest cavity volume decreases → air pushed out.
Gas exchange:
O₂ diffuses from alveoli into blood (higher concentration in alveoli).
CO₂ diffuses from blood into alveoli.
Transport: O₂ carried by haemoglobin, CO₂ as bicarbonates.
✔️ Breathing ensures continuous supply of oxygen for cellular respiration and removal of carbon dioxide.
Question 36
Explain the process of digestion of carbohydrates, proteins and fats in human alimentary canal with related enzymes and secretions.
Answer
Mouth: Salivary amylase breaks starch → maltose.
Stomach: Gastric juice (HCl + pepsin + mucus). Pepsin digests proteins → peptones.
Small intestine:
🔵 Bile (from liver): Emulsifies fats into droplets.
🟢 Pancreatic juice (from pancreas): Amylase (carbs → maltose), Trypsin (proteins → peptides), Lipase (fats → fatty acids & glycerol).
🟡 Intestinal juice: Final breakdown – maltase, peptidase, lipase complete digestion.
Absorption: Through villi into blood/lymph.
Large intestine: Absorbs water, undigested matter removed as feces.
✔️ Complete digestion ensures supply of glucose, amino acids, fatty acids and glycerol for body functions.
🟣 Section E (Q37–Q39: Case/Source Based, 4 marks each)
Question 37
Case: A student performs an experiment by blowing air into lime water through a straw. He observes that lime water turns milky.
Questions:
(a) Why does lime water turn milky?
(b) Write the equation of the reaction.
(c) What does this experiment prove about respiration?
Answer
(a) Lime water turns milky due to formation of calcium carbonate.
(b) Ca(OH)₂ + CO₂ → CaCO₃ + H₂O
(c) Exhaled air contains CO₂ → proves that CO₂ is a product of respiration.
Question 38
Case: A person suffers from kidney failure and is advised dialysis.
Questions:
(a) What is dialysis?
(b) How does it help in purification of blood?
(c) Name two wastes removed by dialysis.
Answer
(a) Dialysis: Artificial method of purifying blood using a dialysis machine when kidneys fail.
(b) Blood passes through semi-permeable membrane in machine → wastes diffuse out → cleaned blood returned to body.
(c) Removes urea, excess salts and water.
Question 39
Case: A potted plant is kept in sunlight for several hours. A leaf is then tested with iodine solution after removing chlorophyll.
Questions:
(a) Why is the leaf treated with alcohol before testing with iodine?
(b) Why is iodine solution used?
(c) What will be the colour change if starch is present?
(d) What does this experiment prove?
Answer
(a) Alcohol removes chlorophyll, making the leaf colourless for starch test.
(b) Iodine solution detects starch.
(c) Blue–black colour appears if starch is present.
(d) Proves that photosynthesis occurs in leaves and starch is formed as its product.
————————————————————————————————————————————————————————————————————————————————————
MIND MAPS
————————————————————————————————————————————————————————————————————————————————————