Revise, Reflect, Refine — Complete Solutions
The complete questions are written first, followed by clear, exam-ready answers. The QUESTION and ANSWER labels are highlighted, while headings are kept smaller for easy copying and reading.
🟦 QUESTION 1
Meristematic tissues divide repeatedly. What property of their cells allows them to do this?
(i) They have thick walls for protection.
(ii) They contain large vacuoles that store nutrients.
(iii) They have thin walls, dense cytoplasm and a large prominent nucleus.
(iv) They are functionally differentiated cells.
🟩 ANSWER
Correct option: (iii)
Meristematic cells have thin cell walls, dense cytoplasm and a large prominent nucleus.
They also possess:
- Very small or no vacuoles
- Little or no intercellular space
- A high rate of metabolic activity
These features allow them to divide repeatedly and produce new cells for plant growth.
🟦 QUESTION 2
If a plant is unable to transport food from leaves to roots, which tissue is malfunctioning?
(i) Xylem
(ii) Phloem
(iii) Epidermis
(iv) Sclerenchyma
🟩 ANSWER
Correct option: (ii) Phloem
The phloem transports food prepared in the leaves to the roots, stems, fruits and other parts of the plant.
The xylem, on the other hand, transports water and minerals from the roots to the upper parts of the plant.
🟦 QUESTION 3
Why are the epithelial tissues that line an animal’s internal organs usually only one or a few cells thick?
(i) To store food efficiently
(ii) To provide maximum strength
(iii) To allow quick exchange of materials across them
(iv) To reduce friction
🟩 ANSWER
Correct option: (iii) To allow quick exchange of materials across them
A thin epithelial layer provides a very short distance for the movement of substances.
Therefore, materials such as oxygen, carbon dioxide, nutrients and waste products can pass rapidly across it.
For example, the air sacs of the lungs have a thin epithelial lining that permits the quick exchange of respiratory gases.
🟦 QUESTION 4
Perform the following two jumps:
- Straight-leg jump: Keep your knees and ankles stiff.
- Normal jump: Bend your knees and ankles naturally.
How did your ankle, knee and hip positions differ between the two jumps?
🟩 ANSWER
Straight-leg jump
- The knees and ankles remain stiff and almost straight.
- The hip bends very little.
- The joints cannot act like springs.
- Less upward force is produced.
- The impact during landing is not absorbed effectively.
Normal jump
- The hips, knees and ankles bend before the jump.
- The joints straighten during take-off.
- The muscles produce greater upward force.
- The joints bend again while landing.
- The bending of joints absorbs the shock of landing.
Therefore, bending the hip, knee and ankle joints makes the normal jump more powerful, balanced and safe.
🟦 QUESTION 5
Which type of joint is involved when you bend your knees and ankles?
(i) Ball-and-socket joint
(ii) Hinge joint
(iii) Pivot joint
🟩 ANSWER
Correct option: (ii) Hinge joint
A hinge joint allows movement mainly in one direction, similar to the opening and closing of a door.
The knee and ankle mainly permit bending and straightening movements.
🟦 QUESTION 6
For each of the following Assertion–Reason questions, choose the correct option:
(i) Both Assertion and Reason are true, and Reason is the correct explanation of Assertion.
(ii) Both Assertion and Reason are true, but Reason is not the correct explanation of Assertion.
(iii) Assertion is true, but Reason is false.
(iv) Assertion is false, but Reason is true.
(A) Assertion: Epithelium is well-suited for gas exchange in the lungs.
Reason: It consists of multiple layers of tall cells that slow down diffusion.
🟩 ANSWER
Correct option: (iii) Assertion is true, but Reason is false.
The air sacs of the lungs are lined by a single layer of thin and flat epithelial cells, not multiple layers of tall cells.
The thin lining allows oxygen and carbon dioxide to diffuse rapidly.
(B) Assertion: Cardiac muscle can contract continuously without fatigue.
Reason: Cardiac muscle cells have many mitochondria and an abundant blood supply.
🟩 ANSWER
Correct option: (i) Both Assertion and Reason are true, and Reason correctly explains Assertion.
Cardiac muscle cells contain many mitochondria that continuously produce energy.
They also receive an abundant supply of blood, which provides oxygen and nutrients. This helps the heart muscles contract continuously without becoming fatigued under normal conditions.
(C) Assertion: Tendons connect bone to bone and allow joint movement.
Reason: Tendons are made of tough connective tissue that transmits force from muscle to bone.
🟩 ANSWER
Correct option: (iv) Assertion is false, but Reason is true.
Tendons connect muscles to bones, not one bone to another.
They transfer the pulling force produced by muscles to bones and help in movement.
Ligaments connect one bone to another.
(D) Assertion: In a hinge joint, movement occurs primarily in one plane.
Reason: The bone ends are shaped to allow sliding in all directions.
🟩 ANSWER
Correct option: (iii) Assertion is true, but Reason is false.
A hinge joint allows bending and straightening mainly in one plane.
It does not permit movement in all directions. Movement in many directions is possible in a ball-and-socket joint.
🟦 QUESTION 7
Plot a graph between the age of a teak tree in years on the x-axis and its diameter in centimetres, along with the number of annual rings, on the y-axis using the following data:
| Age of tree | Diameter | Annual rings |
|---|---|---|
| 5 years | 4 cm | 5 |
| 10 years | 8 cm | 10 |
| 20 years | 24 cm | 20 |
| 25 years | 28 cm | 25 |
| 30 years | 32 cm | 30 |
| 40 years | 40 cm | 40 |
(i) Analyse the graph in terms of the diameter of the stem over time.
(ii) What is the relationship between the diameter and the annual rings?
(iii) Which specialised tissue is responsible for the girth of the stem, and where is it located?
🟩 ANSWER
Graph plotting instructions
- Take the age of the tree on the x-axis.
- Take the diameter and annual rings on the y-axis.
- Plot two separate lines and label them clearly.
Points for diameter:
(5, 4), (10, 8), (20, 24), (25, 28), (30, 32), (40, 40)
Points for annual rings:
(5, 5), (10, 10), (20, 20), (25, 25), (30, 30), (40, 40)
(i) Analysis of stem diameter
The graph shows that the diameter of the teak tree increases as its age increases.
However, the diameter does not increase at exactly the same rate every year. Growth may depend on:
- Water availability
- Mineral nutrients
- Temperature
- Sunlight
- Climatic conditions
(ii) Relationship between diameter and annual rings
As the number of annual rings increases, the diameter of the tree also increases.
Usually, one annual ring is formed in one year. Therefore, annual rings can be used to estimate the age of a tree.
The thickness of the rings may vary according to the growing conditions of that year.
(iii) Tissue responsible for girth
The lateral meristem, especially the vascular cambium, is responsible for increasing the girth of the stem.
It is located along the sides of stems and roots, generally between the xylem and phloem.
🟦 QUESTION 8
In a forest, a tree was severely debarked by an elephant because the bark is a source of food. Answer the following questions:
(i) Which functions of the tree are hampered by debarking?
(ii) Which plant tissues would be affected by further damage beneath the bark?
(iii) Which functions would be hampered if the tissues beneath the bark were severely damaged?
(iv) What assumptions are you making while answering these questions?
🟩 ANSWER
(i) Functions hampered by debarking
Debarking may affect:
- Protection: Bark protects the tree from injury, microorganisms and extreme weather.
- Prevention of water loss: The cork layer reduces evaporation.
- Food transport: The inner bark contains phloem, which carries food.
- Growth in girth: Damage to cambium may affect secondary growth.
(ii) Tissues affected by deeper damage
Further damage may affect:
- Phloem
- Vascular cambium
- Xylem, if the injury reaches deeper parts
(iii) Functions affected
- Damage to phloem will disturb food transport.
- Damage to vascular cambium will reduce growth in girth.
- Damage to xylem will disturb water and mineral transport.
Severe damage may eventually cause the tree to die.
(iv) Assumptions
The answer assumes that:
- A considerable portion of the bark has been removed.
- The phloem and cambium may also be damaged.
- The damage is large enough to disturb normal plant functions.
If only a small superficial area were damaged, the tree might repair itself and survive.
If the bark were removed completely around the trunk, food transport to the roots could stop, causing the tree to die.
🟦 QUESTION 9
Aamrapali observed that the stem of a young mango sapling bends during strong monsoon winds without breaking. Which tissue is responsible for this flexibility? What would happen if this tissue were replaced by sclerenchyma?
🟩 ANSWER
The tissue responsible for flexibility is collenchyma.
Collenchyma is made of living cells with unevenly thickened corners. It provides both support and flexibility to young stems.
If collenchyma were replaced by sclerenchyma:
- The stem would become hard and rigid.
- It would lose much of its flexibility.
- It would not bend easily during strong winds.
- It might break under sudden pressure.
Sclerenchyma cells have thick, lignified walls and mainly provide strength and rigidity.
🟦 QUESTION 10
Sohan used two types of sugarcane cuttings, A and B. After a few weeks, type B cuttings sprouted and developed into plants, while type A cuttings did not sprout.
(i) Why did type B cuttings grow while type A did not?
(ii) What difference was present in type B compared with type A?
(iii) What observations or measurements could be made to determine the effect?
(iv) What parameters should be kept the same to ensure a fair comparison?
🟩 ANSWER
(i) Reason for the growth of type B
Type B cuttings contained at least one healthy node with a bud and meristematic tissue.
The meristematic cells divided repeatedly and produced new roots and shoots.
Type A cuttings probably lacked a node or living bud.
(ii) Difference between the cuttings
Type B had a healthy node and bud, whereas type A either had no node or had a damaged or inactive bud.
(iii) Observations or measurements
Sohan could record:
- Number of cuttings that sprouted
- Time taken for sprouting
- Length of new shoots
- Number of leaves
- Number and length of roots
- Percentage of successful sprouting
(iv) Conditions to be kept the same
- Variety of sugarcane
- Age and health of the parent plant
- Length and thickness of cuttings
- Type and amount of soil
- Amount of water
- Planting depth
- Sunlight
- Temperature
- Fertiliser
- Duration of observation
Only the presence or absence of a healthy node and bud should differ.
🟦 QUESTION 11
Rohan states, “A tissue is a group of similar cells performing similar functions.” Rajiv says that this is true for simple tissues but is different for complex tissues. Explain.
🟩 ANSWER
Rohan’s statement is correct for simple tissues, but it does not fully describe complex tissues.
Simple tissues
Simple tissues are made of one type of similar cells performing related functions.
Examples:
- Parenchyma
- Collenchyma
- Sclerenchyma
Complex tissues
Complex tissues contain different types of cells that work together to perform a common function.
For example:
- Xylem contains tracheids, vessels, xylem parenchyma and xylem fibres.
- Phloem contains sieve tubes, companion cells, phloem parenchyma and phloem fibres.
Therefore:
A tissue is a group of similar or different specialised cells organised to perform one or more common functions.
🟦 QUESTION 12
Coconut husk fibres are used to make mats because they are tough and fibrous. Which tissue provides this strength? Why can living parenchyma not serve the same purpose?
🟩 ANSWER
The tissue present in coconut husk fibres is sclerenchyma.
Sclerenchyma cells:
- Have very thick walls
- Contain lignin
- Are usually dead at maturity
- Have little or no internal space
- Form long, tough fibres
- Provide mechanical strength and rigidity
Parenchyma cells cannot perform the same function because they:
- Have thin cell walls
- Are living cells
- Are loosely packed
- Have intercellular spaces
- Mainly store food and water or perform photosynthesis
Therefore, parenchyma is soft and cannot provide the same toughness as sclerenchyma.
🟦 QUESTION 13
Vibha says, “Meristematic cells are located only at the root and shoot apices.” Is this statement correct? What questions can Neha ask Vibha to help her understand the correct concept?
🟩 ANSWER
Vibha’s statement is incorrect.
Meristematic tissues are present at different locations in a plant.
| Type of meristem | Location | Function |
|---|---|---|
| Apical meristem | Root and shoot tips | Increases length |
| Lateral meristem | Sides of stems and roots | Increases girth |
| Intercalary meristem | Nodes, internodes or leaf bases | Helps in regrowth |
Neha may ask:
- Which tissue increases the thickness of a tree trunk?
- How does grass regrow after grazing or cutting?
- Which tissue is present at nodes and internodes?
- Are actively dividing cells found only at plant tips?
These questions show that meristematic tissues are also present in lateral and intercalary regions.
🟦 QUESTION 14
A plant cell and an animal cell are of the same size.
(i) Which cell will have a larger vacuole? Give reasons.
(ii) What assumptions are you making while answering?
🟩 ANSWER
(i) Cell with a larger vacuole
A typical mature plant cell will have a larger vacuole.
A mature plant cell usually contains one large central vacuole filled with cell sap.
Its functions include:
- Storing water
- Storing minerals and sugars
- Storing waste materials
- Maintaining turgor pressure
- Keeping the plant cell firm
Animal cells may contain small temporary vacuoles, but they are generally much smaller.
(ii) Assumptions
The answer assumes that:
- The plant cell is a mature plant cell.
- The animal cell is a typical animal cell.
- Neither cell is unusually specialised.
- The plant cell is not a meristematic cell.
- Both cells are under normal conditions.
Equal cell size does not mean that their vacuoles will also be equal in size.
🟦 QUESTION 15
A textbook states, “Each plant tissue performs only one specific function.” What questions would you ask to test this statement? Which examples of tissues would you study?
🟩 ANSWER
The statement is not completely correct because many plant tissues perform more than one function.
1. Does parenchyma only store food?
No.
- Ordinary parenchyma stores food and water.
- Chlorenchyma performs photosynthesis.
- Aerenchyma stores air and helps aquatic plants float.
2. Does epidermis only protect the plant?
No.
- Epidermis protects the plant.
- Root epidermis absorbs water and minerals.
- Stomata help in gaseous exchange and transpiration.
- The cuticle reduces water loss.
3. Does xylem only transport water?
No.
Xylem:
- Transports water and minerals
- Provides mechanical support
4. Does phloem only transport food?
No.
Phloem:
- Transports prepared food
- Stores food
- Provides support through phloem fibres
5. Does collenchyma only provide support?
No.
Collenchyma provides:
- Mechanical support
- Flexibility to young stems and leaf stalks
| Plant tissue | Major functions |
|---|---|
| Parenchyma | Storage and photosynthesis |
| Aerenchyma | Air storage and floating |
| Epidermis | Protection, absorption and gaseous exchange |
| Xylem | Water transport and support |
| Phloem | Food transport, storage and support |
| Collenchyma | Support and flexibility |
Therefore, plant tissues are specialised, but many of them perform more than one related function.