Class 10 Science Life Processes Question Bank

A. MCQs — Choose the Correct Answer

1. The main purpose of life processes is to:

A. Produce movement only
B. Maintain the organisation and functioning of the organism
C. Increase body size only
D. Remove oxygen from the body

2. Which process provides organisms with materials and energy needed for maintenance?

A. Excretion
B. Nutrition
C. Transportation
D. Coordination

3. An organism that prepares its own food from simple inorganic substances is:

A. Heterotrophic
B. Autotrophic
C. Parasitic
D. Saprophytic

4. Which combination is essential for photosynthesis according to the chapter?

A. Oxygen, glucose and nitrogen
B. Carbon dioxide, water, sunlight and chlorophyll
C. Protein, oxygen and minerals
D. Carbon dioxide, oxygen and starch

5. The green structures inside leaf cells that contain chlorophyll are:

A. Mitochondria
B. Chloroplasts
C. Ribosomes
D. Vacuoles

6. Stomatal opening and closing is controlled by:

A. Xylem cells
B. Guard cells
C. Root hairs
D. Phloem cells

7. Which substance is used by plants as an internal reserve of carbohydrate?

A. Glycogen
B. Starch
C. Protein
D. Cellulose

8. Which organism obtains nutrition by digesting food outside its body and then absorbing it?

A. Human
B. Fungi
C. Amoeba
D. Fish

9. Amoeba captures food using:

A. Cilia
B. Pseudopodia-like extensions
C. Villi
D. Stomata

10. The enzyme in saliva that begins starch digestion is:

A. Pepsin
B. Trypsin
C. Salivary amylase
D. Lipase

11. The rhythmic muscular movement that pushes food through the alimentary canal is:

A. Diffusion
B. Peristalsis
C. Translocation
D. Filtration

12. Which substance provides an acidic medium in the stomach?

A. Bile
B. Hydrochloric acid
C. Mucus
D. Saliva

13. The main function of mucus in the stomach is to:

A. Digest fats
B. Protect the stomach lining
C. Absorb glucose
D. Neutralise all enzymes

14. Complete digestion of carbohydrates, proteins and fats mainly occurs in the:

A. Mouth
B. Stomach
C. Small intestine
D. Large intestine

15. Bile helps digestion mainly by:

A. Digesting proteins directly
B. Breaking large fat globules into smaller ones
C. Converting glucose into starch
D. Digesting starch in the mouth

16. Which pancreatic enzyme is associated with protein digestion?

A. Trypsin
B. Amylase
C. Pepsin
D. Salivary amylase

17. The main function of intestinal villi is to:

A. Produce bile
B. Increase the surface area for absorption
C. Store faeces
D. Produce hydrochloric acid

18. The first breakdown product of glucose during cellular respiration is:

A. Ethanol
B. Pyruvate
C. Lactic acid
D. Carbon dioxide

19. The initial breakdown of glucose into pyruvate occurs in the:

A. Nucleus
B. Cytoplasm
C. Chloroplast
D. Vacuole

20. Aerobic breakdown of pyruvate takes place in the:

A. Mitochondria
B. Nucleus
C. Ribosome
D. Cell wall

21. Which process generally releases more energy?

A. Aerobic respiration
B. Anaerobic respiration
C. Both release the same amount
D. Neither releases energy

22. In yeast, anaerobic breakdown of pyruvate produces:

A. Lactic acid only
B. Ethanol and carbon dioxide
C. Oxygen and water
D. Glucose and oxygen

23. During insufficient oxygen supply in human muscles, pyruvate may be converted into:

A. Ethanol
B. Lactic acid
C. Starch
D. Bile

24. The immediate energy currency used by cells is:

A. DNA
B. ATP
C. Glucose
D. Oxygen

25. Fish obtain dissolved oxygen mainly through:

A. Lungs
B. Gills
C. Skin only
D. Trachea

26. The structures in human lungs where gaseous exchange occurs are:

A. Bronchi
B. Alveoli
C. Trachea
D. Nostrils

27. The respiratory pigment that carries oxygen in human blood is:

A. Chlorophyll
B. Haemoglobin
C. Melanin
D. Insulin

28. Oxygen is transported mainly by:

A. Plasma alone
B. Red blood cells
C. Platelets
D. White blood cells

29. Which component of blood transports food, carbon dioxide and nitrogenous wastes in dissolved form?

A. Plasma
B. Platelets
C. Red blood cells
D. Haemoglobin

30. Which chamber pumps oxygenated blood to the rest of the body?

A. Right atrium
B. Right ventricle
C. Left atrium
D. Left ventricle

31. Which vessels carry blood away from the heart?

A. Veins
B. Arteries
C. Capillaries
D. Lymph vessels

32. Which blood vessels have walls approximately one cell thick?

A. Arteries
B. Veins
C. Capillaries
D. Aorta

33. Platelets are mainly involved in:

A. Oxygen transport
B. Blood clotting
C. Digestion
D. Photosynthesis

34. The tissue that transports water and minerals in plants is:

A. Phloem
B. Xylem
C. Epidermis
D. Cortex

35. The tissue responsible for transporting products of photosynthesis is:

A. Xylem
B. Phloem
C. Epidermis
D. Meristem

36. The loss of water vapour from aerial parts of plants is called:

A. Translocation
B. Transpiration
C. Respiration
D. Filtration

37. The major driving force for upward movement of water during the daytime is:

A. Transpiration pull
B. Digestion
C. Blood pressure
D. Peristalsis

38. The movement of soluble products of photosynthesis through phloem is called:

A. Filtration
B. Translocation
C. Diffusion
D. Respiration

39. The basic filtration unit of the kidney is the:

A. Alveolus
B. Nephron
C. Villus
D. Neuron

40. Which organ stores urine before it is expelled?

A. Kidney
B. Ureter
C. Urinary bladder
D. Urethra

B. Fill in the Blanks

1. The processes required to maintain life are called __________.

2. Organisms that prepare their own food are called __________.

3. Photosynthesis uses carbon dioxide and __________ as raw materials.

4. The green pigment required for photosynthesis is __________.

5. The tiny pores on leaves involved in gaseous exchange are called __________.

6. The cells that regulate stomatal opening and closing are called __________ cells.

7. Plants store excess carbohydrate mainly as __________.

8. The enzyme present in saliva that acts on starch is __________.

9. The rhythmic movement that pushes food through the alimentary canal is called __________.

10. The stomach secretes hydrochloric acid, pepsin and __________.

11. The finger-like projections in the small intestine are called __________.

12. Glucose is initially broken down into __________ during respiration.

13. Aerobic respiration requires __________.

14. In yeast, anaerobic respiration produces ethanol and __________.

15. ATP is known as the __________ of cellular processes.

16. The tiny structures in the lungs where gas exchange occurs are called __________.

17. Oxygen is transported in human blood mainly with the help of __________.

18. Blood vessels carrying blood away from the heart are called __________.

19. Water and minerals are transported in plants through __________.

20. Food produced in leaves is transported mainly through __________.

21. Loss of water vapour from plant surfaces is called __________.

22. The basic filtration unit of the kidney is the __________.

23. Urine is stored temporarily in the __________.

24. Removal of harmful metabolic wastes is called __________.

C. True or False

Write True or False.

Life processes continue even when an organism is apparently inactive.
All organisms obtain food in exactly the same way.
Green plants generally show autotrophic nutrition.
Chlorophyll is required for photosynthesis.
Stomata are involved in gaseous exchange.
Salivary amylase acts on starch.
Bile is produced by the pancreas.
Villi increase the absorptive surface of the small intestine.
Pyruvate is formed during the initial breakdown of glucose.
Aerobic respiration generally releases more energy than anaerobic respiration.
ATP acts as an energy currency in cells.
Fish obtain oxygen from dissolved oxygen in water through gills.
Alveoli have a large surface area for gas exchange.
Veins carry blood away from the heart.
Capillaries have very thin walls.
Xylem transports food from leaves to roots.
Phloem transports products of photosynthesis.
Transpiration contributes to upward water movement.
Nephrons filter blood and participate in urine formation.
Plants cannot remove or store waste materials.

D. Match the Columns

Column A	Column B
1. Chlorophyll	a. Blood clotting
2. Salivary amylase	b. Water transport
3. Villi	c. Light absorption
4. ATP	d. Starch digestion
5. Alveoli	e. Energy currency
6. Platelets	f. Gas exchange
7. Xylem	g. Food transport
8. Phloem	h. Absorption
9. Nephron	i. Filtration
10. Guard cells	j. Stomatal regulation

E. Assertion–Reason Questions

Choose:

A. Both A and R are true, and R correctly explains A.
B. Both A and R are true, but R does not correctly explain A.
C. A is true but R is false.
D. A is false but R is true.

1.

Assertion: Multicellular organisms require specialised transport systems.
Reason: Many cells are not directly in contact with the external environment.

2.

Assertion: Villi are present in the small intestine.
Reason: They increase the surface available for absorption.

3.

Assertion: Aerobic respiration releases more energy than anaerobic respiration.
Reason: Aerobic respiration involves further breakdown of pyruvate in the presence of oxygen.

4.

Assertion: Alveoli are highly efficient sites of gas exchange.
Reason: They have a large surface area and extensive blood supply.

5.

Assertion: The left ventricle has a thick muscular wall.
Reason: It pumps blood to the whole body.

6.

Assertion: Veins contain valves.
Reason: Valves help prevent backward movement of blood.

7.

Assertion: Transpiration helps in the upward movement of water in plants.
Reason: Water loss from leaves creates a suction force.

8.

Assertion: Phloem transport requires energy.
Reason: Materials such as sucrose are loaded into phloem using ATP.

9.

Assertion: Nephrons selectively reabsorb useful substances.
Reason: All substances filtered from blood must be removed as urine.

10.

Assertion: Plants can store certain waste products in leaves.
Reason: Plants can later shed those leaves.

F. One-Word / Very Short Answer Questions

What is the energy currency of the cell?
Name the pigment involved in photosynthesis.
Name the pores involved in gaseous exchange in leaves.
What is the first product formed from glucose during respiration?
Name the organelle where aerobic breakdown of pyruvate occurs.
Name the respiratory pigment in human beings.
Name the gas taken up during aerobic respiration.
Name the structures responsible for gas exchange in lungs.
Name the blood component involved in clotting.
Name the tissue transporting water in plants.
Name the tissue transporting food in plants.
What is the loss of water vapour from aerial parts of plants called?
What is translocation?
Name the functional unit of the kidney.
Name the tube carrying urine from kidney to bladder.
Name the organ that stores urine.
What is the process of removal of metabolic wastes called?
Name the enzyme in saliva that acts on starch.
Name the enzyme associated with protein digestion in the stomach.
Name the organ that produces bile.

G. Short Answer Questions — 2–3 Marks

Nutrition

Why are maintenance processes essential even when an organism is not visibly active?
Distinguish between autotrophic and heterotrophic nutrition.
What are the essential raw materials and conditions required for photosynthesis?
What is the role of chlorophyll in photosynthesis?
Explain the role of stomata in plants.
Why do plants require minerals such as nitrogen?
How does Amoeba obtain and digest food?
Why do different organisms have different methods of obtaining food?

Human digestion

What are the functions of saliva during digestion?
What is peristalsis and why is it important?
What are the functions of hydrochloric acid, pepsin and mucus in the stomach?
Why is bile important for digestion?
How do pancreatic enzymes help digestion?
Why is the small intestine well suited for absorption?
Why does the length of the small intestine vary among animals with different diets?

Respiration

What happens to glucose during the initial stage of respiration?
Differentiate between aerobic and anaerobic respiration.
Why can muscle cramps occur during sudden physical activity?
Why is ATP important to cells?
Why do aquatic animals generally need a faster breathing rate than terrestrial animals?
How are alveoli adapted for efficient gas exchange?
What role does haemoglobin play in respiration?

Transportation

Why is diffusion insufficient for transporting oxygen throughout a large multicellular organism?
What are the main components of the human transport system?
Why is separation of oxygenated and deoxygenated blood advantageous?
Distinguish between arteries and veins.
Why are capillaries suitable for exchange of substances?
What is the role of platelets?
What is lymph and what are two of its functions?
Why do plants need a transport system?

Plant transport

Differentiate between xylem and phloem.
What is transpiration?
How does transpiration help in water transport?
What is translocation in plants?
Why can phloem transport occur in different directions?

Excretion

What is excretion?
Name the major parts of the human excretory system.
What is the function of a nephron?
Why is selective reabsorption necessary during urine formation?
How do plants get rid of waste products?

H. Long Answer Questions — 4–5 Marks

1. Photosynthesis

Explain photosynthesis and describe the major events involved in the process. Also explain the role of chlorophyll and stomata.

2. Human digestion

Trace the journey of food through the human alimentary canal and explain the major digestive events occurring at each important stage.

3. Respiration

Explain the different pathways followed by pyruvate under aerobic and anaerobic conditions. Compare their energy outputs.

4. Human respiratory system

Describe how the structure of human lungs, particularly the alveoli, enables efficient exchange of gases.

5. Human circulation

Explain the pathway of blood through the four chambers of the human heart. Why is double circulation important?

6. Blood vessels

Compare arteries, veins and capillaries on the basis of direction of blood flow, wall structure and function.

7. Transport in plants

Explain how water and minerals move from roots to leaves. Include the role of root pressure and transpiration pull.

8. Phloem transport

Explain translocation and why it requires energy.

9. Human excretion

Describe the human excretory system and explain how a nephron contributes to urine formation.

10. Plant excretion

Explain the different ways in which plants manage and remove their metabolic wastes.

I. Diagram-Based Questions

These are especially useful for exam preparation.

Human digestive system

Draw a labelled diagram of the human alimentary canal.
Identify the organ where starch digestion begins.
Identify the organ where complete digestion mainly occurs.
Label the structure responsible for nutrient absorption.
Explain the role of villi.

Human respiratory system

Draw and label the human respiratory system.
Identify the site of gaseous exchange.
Explain how oxygen moves from alveoli to blood.
Why are alveolar walls thin?
How does the blood transport oxygen from the lungs?

Human heart

Draw a labelled four-chambered human heart.
Trace the path of deoxygenated blood from body to lungs.
Trace the path of oxygenated blood from lungs to body.
Why are ventricles more muscular than atria?
What is the function of valves?

Nephron

Draw a labelled nephron.
Identify the region where filtration begins.
Explain the significance of selective reabsorption.
Trace the movement of urine from kidney to outside the body.

Plant transport

Draw a simple diagram showing xylem and phloem transport.
Explain how transpiration contributes to upward water movement.
Show the direction of food movement through phloem in a suitable example.

J. Case-Based Questions

Case 1 — A leaf experiment

A student keeps a variegated plant in darkness for several days and later exposes it to sunlight. A starch test is then performed on its leaf.

Questions:

Why was the plant kept in darkness initially?
What does the starch test help detect?
Which regions of the leaf are expected to show starch formation?
What does this experiment demonstrate about chlorophyll?

Case 2 — Digestion

A student eats a meal containing carbohydrates, proteins and fats. The food passes through the mouth, stomach and small intestine before nutrients are absorbed.

Questions:

Which enzyme begins starch digestion?
What is the function of stomach acid?
Why is bile needed?
Where are the final products of digestion absorbed?
Which structures increase the absorptive surface?

Case 3 — Respiration during exercise

During sudden intense physical activity, oxygen availability to muscle cells may become insufficient.

Questions:

What molecule is produced from glucose before the next stage?
What can happen to pyruvate when oxygen is insufficient in muscles?
Which substance may accumulate and contribute to cramps?
Why does aerobic respiration normally provide more energy?

Case 4 — Circulation

A substance absorbed from the intestine must reach cells throughout the body, while carbon dioxide and other wastes must be transported away.

Questions:

Which fluid transports these substances?
Which blood cells mainly carry oxygen?
Which heart chamber pumps oxygenated blood to the body?
Why are capillaries essential for exchange?
Why is double circulation advantageous?

Case 5 — Plant transport

A tall plant absorbs water through its roots while sugars are produced in its leaves.

Questions:

Which tissue carries water upward?
What force significantly assists water movement during the day?
What is the loss of water vapour from leaves called?
Which tissue transports sugars?
Why can phloem transport occur in both directions?

Case 6 — Kidney function

Blood entering the kidneys contains useful substances as well as nitrogenous wastes. The kidneys produce urine while retaining substances that the body needs.

Questions:

What is the functional unit of the kidney?
What happens during filtration?
Name two useful substances that can be selectively reabsorbed.
What happens to the remaining waste?
Why is reabsorption important?

K. Higher-Order Thinking Questions

Why would a large multicellular organism struggle to survive if it depended only on diffusion for oxygen supply?
A plant has adequate water but its leaves cannot exchange gases efficiently. How would this affect photosynthesis?
Why is the small intestine more important for nutrient absorption than the stomach?
Why would damage to alveoli seriously affect energy production in the body?
Why does the heart need valves even though it already has muscular chambers?
Why are capillary walls much thinner than arterial walls?
A plant is growing taller and taller. Why does its transport requirement increase even though plants generally have lower energy needs than animals?
Why is transpiration both useful and potentially associated with water loss?
Why does the kidney reabsorb useful substances instead of simply allowing everything filtered from blood to leave as urine?
Why can plants use storage in leaves, vacuoles, gums and resins as part of their waste-management strategy?

L. Compare and Differentiate

Prepare these as table-based answers:

Autotrophic nutrition vs heterotrophic nutrition
Aerobic vs anaerobic respiration
Arteries vs veins
Arteries vs capillaries
Xylem vs phloem
Respiration vs breathing
Root pressure vs transpiration pull
Human excretion vs plant waste removal
Alveoli vs nephrons
Photosynthesis vs cellular respiration

M. Sequence / Arrange in Correct Order

1. Human digestion

Arrange:

Small intestine
Mouth
Stomach
Oesophagus
Large intestine

2. Blood circulation

Arrange the pathway:

Left ventricle
Lungs
Right atrium
Right ventricle
Left atrium
Body

3. Urine pathway

Arrange:

Urethra
Kidney
Urinary bladder
Ureter

4. Respiration

Arrange:

Glucose
Pyruvate
Further breakdown
Energy production

5. Plant water transport

Arrange:

Root
Xylem
Leaf
Transpiration

N. Statement-Based Questions

State whether each statement is correct or incorrect, and correct the incorrect ones.

Chlorophyll converts carbon dioxide directly into oxygen.
Guard cells regulate stomatal pores.
Saliva begins the digestion of starch.
Bile is secreted by the pancreas.
Villi reduce the surface area available for absorption.
Pyruvate is produced during the initial breakdown of glucose.
Anaerobic respiration generally produces more energy than aerobic respiration.
Haemoglobin helps transport oxygen.
Veins carry blood away from the heart.
Xylem transports water and minerals.
Phloem transports products of photosynthesis.
Transpiration is the loss of water vapour from aerial plant parts.
Nephrons are the filtration units of kidneys.
The urinary bladder produces urine.
Plants have no mechanism for dealing with wastes.

O. Most Important 15 Questions for Final Revision

If you have very little time, do these first:

Explain photosynthesis and state its requirements.
Explain the role of stomata and guard cells.
Describe digestion in the human alimentary canal.
Explain the functions of HCl, pepsin, mucus and bile.
Explain how villi help absorption.
Compare aerobic and anaerobic respiration.
Explain the role of ATP.
Describe the structure and function of alveoli.
Explain double circulation in humans.
Compare arteries, veins and capillaries.
Explain the functions of xylem and phloem.
Explain transpiration pull.
Describe translocation through phloem.
Explain the structure and functioning of a nephron.
Describe different methods of excretion in plants.

Complete Answers

A. MCQ Answers

Q	Answer	Key point
1	B	Life processes maintain the organism
2	B	Nutrition provides materials and energy
3	B	Autotrophs make their own food
4	B	CO₂ + water + sunlight + chlorophyll
5	B	Chloroplasts contain chlorophyll
6	B	Guard cells control stomata
7	B	Plants store carbohydrate as starch
8	B	Fungi digest food externally
9	B	Amoeba uses temporary extensions
10	C	Salivary amylase acts on starch
11	B	Peristalsis moves food
12	B	HCl provides acidic medium
13	B	Mucus protects stomach lining
14	C	Complete digestion mainly occurs here
15	B	Bile emulsifies fats
16	A	Trypsin digests proteins
17	B	Villi increase absorption area
18	B	Glucose first forms pyruvate
19	B	Initial breakdown occurs in cytoplasm
20	A	Aerobic breakdown occurs in mitochondria
21	A	Aerobic respiration releases more energy
22	B	Yeast → ethanol + CO₂
23	B	Muscles may form lactic acid
24	B	ATP is cellular energy currency
25	B	Fish use gills
26	B	Gas exchange occurs in alveoli
27	B	Haemoglobin carries oxygen
28	B	RBCs carry oxygen
29	A	Plasma carries dissolved substances
30	D	Left ventricle pumps to body
31	B	Arteries carry blood away
32	C	Capillaries have very thin walls
33	B	Platelets help clotting
34	B	Xylem transports water/minerals
35	B	Phloem transports photosynthetic products
36	B	Water vapour loss = transpiration
37	A	Transpiration pull drives upward movement
38	B	Food movement = translocation
39	B	Nephron is kidney’s filtration unit
40	C	Bladder stores urine

B. Fill in the Blanks — Answers

Life processes
Autotrophs
Water
Chlorophyll
Stomata
Guard
Starch
Salivary amylase
Peristalsis
Mucus
Villi
Pyruvate
Oxygen
Carbon dioxide
Energy currency
Alveoli
Haemoglobin
Arteries
Xylem
Phloem
Transpiration
Nephron
Urinary bladder
Excretion

C. True or False — Answers

True
False — Organisms have different nutritional methods.
True
True
True
True
False — Bile is produced by the liver.
True
True
True
True
True
True
False — Veins carry blood towards the heart.
True
False — Xylem transports water and minerals.
True
True
True
False — Plants have several methods for managing wastes.

D. Match the Columns — Answers

Column A	Correct match
1. Chlorophyll	c. Light absorption
2. Salivary amylase	d. Starch digestion
3. Villi	h. Absorption
4. ATP	e. Energy currency
5. Alveoli	f. Gas exchange
6. Platelets	a. Blood clotting
7. Xylem	b. Water transport
8. Phloem	g. Food transport
9. Nephron	i. Filtration
10. Guard cells	j. Stomatal regulation

E. Assertion–Reason — Answers

1.

Answer: A

Both statements are true, and the reason explains why specialised transport systems are required in multicellular organisms.

2.

Answer: A

Villi increase the surface area available for absorption.

3.

Answer: A

Aerobic respiration involves further breakdown of pyruvate using oxygen and therefore releases considerably more energy.

4.

Answer: A

Large surface area, thin walls and extensive blood supply make alveoli efficient for gas exchange.

5.

Answer: A

The left ventricle has a thick muscular wall because it pumps blood throughout the body.

6.

Answer: A

Valves prevent backward movement of blood.

7.

Answer: A

Evaporation from leaves creates a suction that contributes to upward water movement.

8.

Answer: A

Phloem loading uses energy from ATP.

9.

Answer: C

The assertion is true, but the reason is false. Useful substances are selectively reabsorbed rather than all being eliminated.

10.

Answer: A

Plants can store wastes in leaves and later remove them when the leaves fall.

F. One-Word / Very Short Answers

ATP
Chlorophyll
Stomata
Pyruvate
Mitochondria
Haemoglobin
Oxygen
Alveoli
Platelets
Xylem
Phloem
Transpiration
Movement of soluble photosynthetic products through phloem
Nephron
Ureter
Urinary bladder
Excretion
Salivary amylase
Pepsin
Liver

G. Short Answer Questions

1. Why are maintenance processes essential even when an organism is not visibly active?

Living organisms continuously undergo internal molecular activities. Energy and materials are required to maintain their organised structures, even during rest or sleep.

2. Differentiate between autotrophic and heterotrophic nutrition.

Autotrophic	Heterotrophic
Organism makes its own food	Organism obtains food from other organisms
Uses simple inorganic substances	Usually obtains complex organic substances
Green plants are examples	Animals and fungi are examples

3. What are the essential raw materials and conditions required for photosynthesis?

The main requirements are:

Carbon dioxide
Water
Sunlight
Chlorophyll

Plants also require minerals such as nitrogen, phosphorus, iron and magnesium for growth and synthesis of body substances.

4. What is the role of chlorophyll in photosynthesis?

Chlorophyll absorbs light energy. This energy is converted into chemical energy that helps drive the reactions involved in photosynthesis.

5. Explain the role of stomata.

Stomata allow gaseous exchange between the plant and its surroundings. They also provide a route for water vapour loss. Guard cells regulate their opening and closing.

6. Why do plants require minerals such as nitrogen?

Nitrogen is needed for synthesising proteins and other important compounds required for plant growth and development.

7. How does Amoeba obtain and digest food?

Amoeba surrounds food using temporary finger-like extensions of its cell surface. These extensions enclose the food and form a food vacuole. Digestion occurs inside the vacuole, and simpler substances then enter the cytoplasm.

8. Why do different organisms have different methods of obtaining food?

Organisms differ in body design, habitat, food availability and the nature of their food. Therefore, their methods of obtaining and processing food are adapted to their particular conditions.

9. What are the functions of saliva?

Saliva:

Moistens food.
Helps make swallowing easier.
Contains salivary amylase, which begins starch digestion.

10. What is peristalsis and why is it important?

Peristalsis is the rhythmic contraction and relaxation of muscles in the alimentary canal. It pushes food forward through the digestive tract.

11. Functions of HCl, pepsin and mucus

HCl: Provides the acidic medium needed for pepsin.
Pepsin: Helps digest proteins.
Mucus: Protects the stomach lining from the acidic contents.

12. Why is bile important for digestion?

Bile helps make acidic food from the stomach more alkaline and breaks large fat globules into smaller ones. This increases the efficiency of enzyme action on fats.

13. How do pancreatic enzymes help digestion?

Pancreatic juice contains enzymes such as:

Trypsin for protein digestion.
Lipase for digestion of emulsified fats.

14. Why is the small intestine well suited for absorption?

Its inner lining has numerous villi, which greatly increase surface area. The villi also contain many blood vessels, allowing absorbed nutrients to be transported efficiently.

15. Why does small-intestine length vary among animals?

It is related to diet. Herbivores eating grass need a longer small intestine because plant material such as cellulose is more difficult to digest. Meat is comparatively easier to digest.

16. What happens to glucose during the initial stage of respiration?

Glucose is broken down in the cytoplasm to form a three-carbon compound called pyruvate.

17. Differentiate between aerobic and anaerobic respiration.

Aerobic respiration: Uses oxygen and releases more energy, producing carbon dioxide and water after further breakdown of pyruvate.

Anaerobic respiration: Does not use oxygen and generally releases less energy. In yeast it produces ethanol and carbon dioxide; in human muscles, pyruvate can form lactic acid.

18. Why can muscle cramps occur during sudden physical activity?

When oxygen supply to muscle cells becomes insufficient, pyruvate can be converted into lactic acid. Accumulation of lactic acid is associated with muscle cramps.

19. Why is ATP important to cells?

ATP stores usable energy released during respiration and supplies it for cellular activities such as muscle contraction, protein synthesis and nervous impulses.

20. Why do aquatic animals generally need faster breathing?

Water contains considerably less dissolved oxygen than air. Therefore, aquatic animals need to pass more water over their respiratory surfaces to obtain sufficient oxygen.

21. How are alveoli adapted for gas exchange?

Alveoli:

Have a large surface area.
Have thin walls.
Have an extensive blood-vessel network.

These features allow rapid exchange of oxygen and carbon dioxide.

22. What role does haemoglobin play?

Haemoglobin in red blood cells binds oxygen and transports it from the lungs to body tissues.

23. Why is diffusion insufficient in large multicellular organisms?

Many cells are located far from the external environment. Diffusion alone would be too slow to supply all cells with oxygen and nutrients and remove wastes efficiently.

24. Main components of the human transport system

The main components are:

Heart — pumps blood.
Blood — transports substances.
Blood vessels — provide pathways for blood flow.

25. Why is separation of oxygenated and deoxygenated blood advantageous?

It prevents mixing and allows highly oxygenated blood to reach body tissues efficiently. This is particularly important for animals with high energy requirements.

26. Arteries vs veins

Arteries	Veins
Carry blood away from heart	Carry blood towards heart
Thick, elastic walls	Comparatively thinner walls
Blood is under higher pressure	Blood is under lower pressure
Generally lack valves in the main vessel system described	Have valves to prevent backflow

27. Why are capillaries suitable for exchange?

Capillaries have extremely thin walls, approximately one cell thick. This makes exchange of materials between blood and surrounding tissues easier.

28. What is the role of platelets?

Platelets help clot blood at damaged blood vessels, reducing blood loss and helping maintain the pressure and continuity of the circulatory system.

29. What is lymph and what are two functions?

Lymph is a colourless tissue fluid derived from material that leaves blood capillaries.

Functions include:

Returning excess tissue fluid to the blood.
Transporting absorbed fats from the intestine.

30. Why do plants need a transport system?

In large plants, roots and leaves can be far apart. Diffusion alone cannot efficiently transport water, minerals and food over such distances.

31. Differentiate between xylem and phloem.

Xylem	Phloem
Transports water and minerals	Transports photosynthetic products
Mainly carries materials from roots upwards	Can transport materials in different directions
Movement largely uses physical forces	Translocation uses energy

32. What is transpiration?

Transpiration is the loss of water in the form of water vapour from the aerial parts of a plant, especially through stomata.

33. How does transpiration help water transport?

Evaporation of water from leaf cells creates a suction force. This transpiration pull draws water upward through xylem from the roots.

34. What is translocation?

Translocation is the movement of soluble products of photosynthesis through phloem from their source to other parts of the plant.

35. Why can phloem transport occur in different directions?

Food and other substances are transported according to the plant’s requirements. Therefore, phloem can move materials towards growing or storage regions in different directions.

36. What is excretion?

Excretion is the biological removal of harmful metabolic waste products from the body.

37. Major parts of the human excretory system

Pair of kidneys
Pair of ureters
Urinary bladder
Urethra

38. What is the function of a nephron?

A nephron filters blood and helps form urine by filtration followed by selective reabsorption of useful substances.

39. Why is selective reabsorption necessary?

The initial filtrate contains useful substances such as glucose, amino acids, salts and much water. Reabsorption prevents unnecessary loss of these substances from the body.

40. How do plants get rid of wastes?

Plants may:

Lose excess water by transpiration.
Store wastes in vacuoles.
Store wastes in leaves that later fall.
Store wastes as gums and resins.
Release some wastes into surrounding soil.

H. Long Answer Questions

1. Explain photosynthesis.

Photosynthesis is the process by which autotrophic organisms use carbon dioxide and water to produce carbohydrates using light energy absorbed by chlorophyll.

The major events are:

Chlorophyll absorbs light.
Light energy is converted into chemical energy and water is split.
Carbon dioxide is reduced to form carbohydrates.
Excess carbohydrate can be stored as starch.

Stomata allow the gaseous exchange needed for the process.

2. Describe digestion in humans.

Food enters through the mouth, where chewing breaks it into smaller pieces and saliva begins starch digestion.

It passes through the oesophagus by peristalsis and enters the stomach. Gastric glands release HCl, pepsin and mucus. Protein digestion begins here.

Food then enters the small intestine, where bile helps with fats and pancreatic and intestinal enzymes complete digestion. The digested nutrients are absorbed through villi.

The large intestine absorbs additional water. The remaining material is eventually removed through the anus.

3. Explain the pathways of pyruvate.

Glucose is first broken down into pyruvate in the cytoplasm.

With oxygen:
Pyruvate is further broken down in mitochondria, producing carbon dioxide, water and a large amount of energy.

Without oxygen in yeast:
Pyruvate forms ethanol and carbon dioxide, releasing less energy.

When oxygen is insufficient in human muscles:
Pyruvate can form lactic acid.

Thus, respiration can follow different pathways depending on oxygen availability and the organism.

4. Explain how alveoli are adapted for gas exchange.

Alveoli are tiny balloon-like structures inside the lungs.

They are efficient because:

They occur in very large numbers, providing a large surface area.
Their walls are very thin.
They are surrounded by an extensive network of blood vessels.

Oxygen diffuses from alveolar air into blood, while carbon dioxide moves from blood into the alveoli for exhalation.

5. Explain double circulation in humans.

Deoxygenated blood from the body enters the right atrium, passes into the right ventricle, and is pumped to the lungs.

After oxygenation, blood returns to the left atrium, passes into the left ventricle, and is pumped to the entire body.

Thus blood passes through the heart twice in one complete cycle:

Heart → lungs → heart
Heart → body → heart

This separation prevents mixing of oxygenated and deoxygenated blood and ensures efficient oxygen supply.

6. Compare arteries, veins and capillaries.

Feature	Arteries	Veins	Capillaries
Direction	Away from heart	Towards heart	Connect arterial and venous networks
Walls	Thick and elastic	Comparatively thinner	Extremely thin
Pressure	High	Lower	Suitable for exchange
Special feature	Strong walls withstand pressure	Valves prevent backflow	One-cell-thick walls
Function	Carry blood from heart	Return blood to heart	Exchange substances with tissues

7. Explain movement of water from roots to leaves.

Root cells take up ions from the soil. Water then enters the roots, contributing to a continuous water column in xylem.

Root pressure contributes to upward movement, but it is generally insufficient to raise water to great heights.

During the day, water evaporates from leaf surfaces through stomata. This creates a transpiration pull, which draws water upward through the xylem.

8. Explain translocation.

Translocation is the transport of soluble products of photosynthesis through the phloem.

Materials such as sucrose are loaded into phloem using energy from ATP. This changes the osmotic conditions and causes water to enter the phloem. The resulting pressure helps move materials towards regions where they are required.

Transport can occur towards growing or storage organs and therefore may be upward or downward.

9. Describe the human excretory system and urine formation.

The human excretory system consists of two kidneys, two ureters, a urinary bladder and a urethra.

The kidneys contain numerous nephrons. Blood is filtered through thin-walled capillary clusters associated with Bowman’s capsules.

The filtrate contains both wastes and useful substances. As it moves through the nephron, useful substances such as glucose, amino acids, salts and much of the water are selectively reabsorbed.

The remaining fluid forms urine, which passes through the ureters to the urinary bladder and is eventually released through the urethra.

10. Explain excretion in plants.

Plants manage wastes in several ways:

Excess water is lost through transpiration.
Some wastes are stored in cellular vacuoles.
Some are stored in leaves that eventually fall.
Gums and resins can store wastes, particularly in older xylem.
Some waste substances are released into the surrounding soil.
Gases such as oxygen and carbon dioxide can be exchanged with the surroundings.

I. Diagram-Based Answers

Human digestive system

Correct sequence:

Mouth → Oesophagus → Stomach → Small intestine → Large intestine → Anus

Starch digestion begins: Mouth
Complete digestion: Small intestine
Main absorption: Small intestine
Absorptive structures: Villi

Human respiratory system

Air pathway:

Nostrils → Throat → Air passages → Lungs → Alveoli

Gas exchange site: Alveoli
Oxygen: Alveoli → Blood
Carbon dioxide: Blood → Alveoli
Thin alveolar walls shorten the diffusion distance.
Blood carries oxygen mainly through haemoglobin.

Human heart

Deoxygenated pathway:

Body → Right atrium → Right ventricle → Lungs

Oxygenated pathway:

Lungs → Left atrium → Left ventricle → Body

Ventricles are thicker because they pump blood out of the heart.
Valves prevent backward flow.

Nephron

Key structures/concepts to label:

Bowman’s capsule
Capillary cluster
Coiled tubule
Ureter/outflow pathway

Main sequence:

Filtration → Selective reabsorption → Urine formation

Plant transport

Xylem

Soil → Roots → Xylem → Stem → Leaves

Phloem

Leaves/source → Growing or storage regions

Phloem movement can occur in either direction depending on the plant’s requirements.

J. Case-Based Answers

Case 1 — Leaf experiment

1.

The plant is kept in darkness so previously stored starch is used up. This helps make the later starch test meaningful.

2.

The starch test detects whether starch has accumulated in the leaf.

3.

The green regions are expected to show starch formation after suitable exposure to light.

4.

It demonstrates that chlorophyll-containing regions are associated with photosynthesis.

Case 2 — Digestion

1.

Salivary amylase

2.

HCl provides the acidic medium needed for the action of pepsin.

3.

Bile helps neutralise the acidic food entering the small intestine and emulsifies fats.

4.

Mainly in the small intestine.

5.

Villi

Case 3 — Respiration during exercise

1.

Pyruvate

2.

It can be converted into lactic acid in human muscle cells when oxygen is insufficient.

3.

Lactic acid

4.

Aerobic respiration involves further breakdown of pyruvate in the presence of oxygen and releases considerably more energy.

Case 4 — Circulation

1.

Blood

2.

Red blood cells, using haemoglobin.

3.

Left ventricle

4.

Capillaries have thin walls that allow exchange between blood and tissues.

5.

Double circulation helps keep oxygenated and deoxygenated blood separate and allows efficient oxygen delivery.

Case 5 — Plant transport

1.

Xylem

2.

Transpiration pull

3.

Transpiration

4.

Phloem

5.

Because phloem transports materials according to the plant’s requirements, which can involve movement towards different growing or storage regions.

Case 6 — Kidney function

1.

Nephron

2.

Blood is filtered through thin-walled capillary structures associated with Bowman’s capsule.

3.

Examples: glucose, amino acids, salts and water.

4.

The remaining material becomes urine.

5.

It prevents useful substances and excessive amounts of water from being unnecessarily lost from the body.

K. Higher-Order Thinking Answers

1.

Diffusion alone is too slow over long distances. In large organisms, specialised transport systems are required to deliver oxygen and nutrients and remove wastes efficiently.

2.

Poor gas exchange would reduce the availability of carbon dioxide for photosynthesis and therefore interfere with food production.

3.

The small intestine receives digestive secretions and contains villi that provide a large surface area for absorption. Therefore, it is much more suited to nutrient absorption than the stomach.

4.

Damaged alveoli would reduce efficient oxygen uptake. Less oxygen reaching cells would interfere with aerobic respiration and energy production.

5.

Valves ensure that blood moves in the correct direction and prevent backward flow when chambers contract.

6.

Capillaries are exchange surfaces, so their very thin walls allow substances to move between blood and tissues efficiently.

7.

As a plant becomes taller, the distance between roots and leaves increases. Therefore, simple diffusion becomes inadequate and a transport system is needed.

8.

Transpiration causes water loss, but it also creates transpiration pull, which assists the upward movement of water and minerals and helps regulate temperature.

9.

Filtration produces a mixture containing both wastes and useful substances. Selective reabsorption returns needed substances to the blood and prevents their unnecessary loss.

10.

Plants can store wastes in places such as vacuoles and leaves. Since leaves can eventually fall, stored waste can thereby be removed from the plant.

L. Compare and Differentiate — Answers

1. Autotrophic vs Heterotrophic Nutrition

Autotrophic	Heterotrophic
Organism makes its own food	Obtains food from other organisms
Uses simple inorganic substances	Uses complex organic food
Green plants are examples	Animals and fungi are examples

2. Aerobic vs Anaerobic Respiration

Aerobic	Anaerobic
Requires oxygen	Does not require oxygen
More energy released	Less energy released
Produces CO₂ and water after further breakdown	Products vary with pathway
Further breakdown occurs in mitochondria	Does not follow the aerobic mitochondrial pathway

3. Arteries vs Veins

Arteries	Veins
Away from heart	Towards heart
Thick, elastic walls	Thinner walls
Higher pressure	Lower pressure
No valves in the main arterial pathway described	Valves present

4. Arteries vs Capillaries

Arteries	Capillaries
Carry blood away from heart	Connect small vessels near tissues
Thick walls	One-cell-thick walls
Carry blood under relatively high pressure	Specialised for exchange

5. Xylem vs Phloem

Xylem	Phloem
Water + minerals	Photosynthetic products + other substances
Mainly upward transport	Can move in different directions
Mostly physical forces	Uses energy for translocation

6. Respiration vs Breathing

Breathing: Physical process of taking in and releasing air.

Respiration: Chemical breakdown of food in cells to release usable energy.

7. Root Pressure vs Transpiration Pull

Root pressure: Pressure generated in roots that contributes to upward movement of water.

Transpiration pull: Suction produced by water loss from leaves; it is a major driving force for water movement during the day.

8. Human vs Plant Excretion

Humans: Use specialised organs, especially kidneys, to remove metabolic wastes.

Plants: Use several methods including storage in vacuoles, leaves, gums/resins, transpiration and release into surrounding soil.

9. Alveoli vs Nephrons

Alveoli	Nephrons
Found in lungs	Found in kidneys
Exchange respiratory gases	Filter blood and form urine
Thin walls and rich blood supply	Filtration followed by selective reabsorption

10. Photosynthesis vs Cellular Respiration

Photosynthesis	Cellular respiration
Makes carbohydrates	Breaks down organic food
Uses light energy	Releases usable energy
Uses CO₂ and water	Produces energy, with CO₂ and water in aerobic pathway
Occurs in chlorophyll-containing structures	Initial glucose breakdown occurs in cytoplasm; aerobic further breakdown occurs in mitochondria

M. Sequence Answers

1. Human digestion

Mouth → Oesophagus → Stomach → Small intestine → Large intestine

2. Blood circulation

Right atrium → Right ventricle → Lungs → Left atrium → Left ventricle → Body

3. Urine pathway

Kidney → Ureter → Urinary bladder → Urethra

4. Respiration

Glucose → Pyruvate → Further breakdown → Energy release

5. Plant water transport

Root → Xylem → Leaf → Transpiration

N. Statement-Based Answers

Q	Answer	Correction if needed
1	❌ Incorrect	Chlorophyll absorbs light energy; it does not directly convert CO₂ into oxygen.
2	✅ Correct	—
3	✅ Correct	—
4	❌ Incorrect	Bile is produced by the liver.
5	❌ Incorrect	Villi increase surface area for absorption.
6	✅ Correct	—
7	❌ Incorrect	Aerobic respiration releases more energy.
8	✅ Correct	—
9	❌ Incorrect	Veins carry blood towards the heart.
10	✅ Correct	—
11	✅ Correct	—
12	✅ Correct	—
13	✅ Correct	—
14	❌ Incorrect	The urinary bladder stores urine; kidneys produce it.
15	❌ Incorrect	Plants use several mechanisms to manage and remove wastes.

O. Top 15 Final-Revision Answers

1. Photosynthesis

Photosynthesis uses CO₂ and water to produce carbohydrates using light energy absorbed by chlorophyll. Oxygen is released during the process. Major events include light absorption, conversion of light energy, water splitting and conversion of carbon dioxide into carbohydrates.

2. Stomata and guard cells

Stomata are pores through which gases are exchanged. Guard cells control their opening and closing, thereby regulating gas exchange and water loss.

3. Human digestion

Food is mechanically processed in the mouth and mixed with saliva. It travels by peristalsis to the stomach, where protein digestion begins. In the small intestine, digestion of carbohydrates, proteins and fats is completed with the help of intestinal, pancreatic and bile secretions. Nutrients are absorbed through villi.

4. HCl, pepsin, mucus and bile

HCl: Acidic medium for pepsin.
Pepsin: Protein digestion.
Mucus: Protects stomach lining.
Bile: Makes acidic food more alkaline and emulsifies fats.

5. Villi

Villi increase the surface area of the small intestine and contain blood vessels, enabling efficient absorption and transport of digested nutrients.

6. Aerobic vs anaerobic respiration

Aerobic respiration uses oxygen and releases more energy. Anaerobic respiration does not use oxygen and releases less energy. Yeast can produce ethanol and CO₂ anaerobically, while human muscles may produce lactic acid when oxygen is insufficient.

7. ATP

ATP acts as the cell’s usable energy currency. Energy released during respiration is stored in ATP and then used for cellular activities.

8. Alveoli

Alveoli have thin walls, a large surface area and extensive blood supply. These adaptations enable efficient oxygen and carbon dioxide exchange.

9. Double circulation

Deoxygenated blood travels from body → right side of heart → lungs. Oxygenated blood returns to left side of heart → body. Thus, blood passes through the heart twice in one complete cycle.

10. Arteries, veins and capillaries

Arteries carry blood away from the heart and have thick elastic walls. Veins return blood and contain valves. Capillaries have very thin walls and permit exchange with tissues.

11. Xylem and phloem

Xylem: water and minerals.
Phloem: products of photosynthesis and other transported substances.

12. Transpiration pull

Water evaporating from leaves creates a suction force. This pulls water upward through the xylem from roots to aerial parts.

13. Translocation

Translocation is the movement of soluble photosynthetic products through phloem. It uses energy and can occur in different directions according to plant requirements.

14. Nephron

A nephron filters blood and forms urine. Filtration occurs through a capillary network associated with Bowman’s capsule, followed by selective reabsorption of useful substances and much of the water.

15. Excretion in plants

Plants remove or manage wastes through transpiration, storage in vacuoles, storage in leaves that later fall, storage as gums/resins and release of certain substances into the surrounding soil.