Class 9 New Science Book 2026 Ch3 Tissues in Action With Answer

Class 9 Science Ch 6: Tissues in Action (New Updated CBSE 2026 Book)

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 large prominent nucleus.
(iv) They are functionally differentiated cells.

Answer: (iii) They have thin walls, dense cytoplasm and large prominent nucleus.

Explanation:
Meristematic cells actively divide and help in plant growth. Their thin walls, dense cytoplasm, and large nucleus support continuous cell division.

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: (ii) Phloem

Explanation:
Phloem transports prepared food from leaves to other parts of the plant such as roots, stems, and fruits. If food transport stops, phloem is malfunctioning.

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: (iii) To allow quick exchange of materials across them.

Explanation:
Thin epithelial tissues help in rapid diffusion and exchange of substances such as gases, nutrients, and wastes across body surfaces.

4. You can perform these two jumps (Fig. 3.21):

Straight-leg jump — keep knees and ankles stiff.
Normal jump — bend knees and ankles naturally.

How did your ankle, knee and hip positions differ between the two jumps?

Answer:
In the straight-leg jump, the knees and ankles remain stiff with very little bending, making the jump harder and less flexible. In the normal jump, the knees, ankles, and hips bend naturally, helping the body absorb shock and produce a better jump.

5. Which type of joint is involved when you bend your knees and ankles?

(i) Ball and socket
(ii) Hinge
(iii) Pivot

Answer: (ii) Hinge

Explanation:
Hinge joints allow movement mainly in one direction, like opening and closing a door. Knees and ankles work as hinge joints during bending.

6. In each of the following cases (A, B, C and D), choose the correct option as given below:

(i) Both (A) and (R) are true, and (R) is the correct explanation of (A).
(ii) Both (A) and (R) are true, but (R) is not the correct explanation of (A).
(iii) (A) is true, but (R) is false.
(iv) (A) is false, but (R) 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: (iii) (A) is true, but (R) is false.

Explanation:
Epithelium in lungs is thin and simple, allowing rapid gas exchange. Multiple thick layers would slow diffusion.

B.

Assertion: Cardiac muscle can contract continuously without fatigue.
Reason: Cardiac muscle cells have a high number of mitochondria and an abundant blood supply.

Answer: (i) Both (A) and (R) are true, and (R) is the correct explanation of (A).

Explanation:
Cardiac muscles require constant energy. Numerous mitochondria and rich blood supply help them work continuously without fatigue.

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: (iv) (A) is false, but (R) is true.

Explanation:
Ligaments connect bone to bone, while tendons connect muscle to bone.

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: (iii) (A) is true, but (R) is false.

Explanation:
Hinge joints allow movement mainly in one direction only, not in all directions.

Question 7

Plot a graph between the age of a tree (in years) on the x-axis and the diameter of the tree (in cm) along with the number of annual rings formed over time on the y-axis, using the data given in Table 3.7.

Table 3.7: Data related to the age of a teak tree, and corresponding increase in the diameter of stem and number of annual rings

1. Analyse the graph in terms of the diameter of the stem over time and share the interpretation.
2. What is the relationship between the diameter of the teak tree and the annual rings formed?
3. Which specialised tissue is responsible for the girth of the stem and where is it located?

Answer

1. The graph shows that the diameter of the teak tree increases as the age of the tree increases. This indicates continuous secondary growth in the stem over time.


2. The number of annual rings increases with the increase in the diameter of the teak tree. Older trees have more annual rings and greater stem diameter.


3. The specialised tissue responsible for the increase in girth of the stem is the lateral meristem (cambium). It is located between the xylem and phloem in the stem.

Question

In a forest, it was observed that one of the trees was severely debarked by an elephant to meet its food requirements, as the bark is a rich source of nutrients. Based on your learning, answer the following:

• (i) Which function(s) of the tree is/are hampered by debarking?
• (ii) Which plant tissue would be affected by further damage to the tree trunk even after debarking?
• (iii) Which function of the tree would be hampered if the tissues beneath the bark were severely damaged?
• (iv) What assumptions are you making to answer the questions above? How would the answer change if your assumptions are also changed?

Answer

• (i) Debarking hampers the transport of food from leaves to other parts of the plant because the bark contains phloem tissue.
• (ii) The xylem tissue would be affected by further damage to the tree trunk even after debarking.
• (iii) If the tissues beneath the bark were severely damaged, the transport of water and minerals from roots to leaves would be hampered.
• (iv) The assumption made is that only the bark and nearby tissues are damaged while the inner xylem remains functional. If the xylem is also damaged completely, both water transport and food transport would stop, which could eventually kill the tree.

9. Aamrapali observed that a young mango sapling’s stem bends flexibly during monsoon winds and does not break. Which tissue is responsible for this flexibility? Predict and provide your explanation of the impact if the existing tissue was replaced by sclerenchyma.

Answer:
Collenchyma tissue is responsible for the flexibility of the young mango sapling stem. Collenchyma cells provide mechanical support while allowing bending and flexibility.

If collenchyma were replaced by sclerenchyma, the stem would become hard and rigid because sclerenchyma cells have thick lignified walls. The sapling would lose flexibility and could break easily during strong winds.

10. Sohan designed an experiment for the regeneration of sugarcane, where he used cuttings to grow sugarcane. He used two types of cuttings, type ‘A’ and type ‘B’. After a few weeks, type ‘B’ cuttings sprouted and developed into sugarcane plants, whereas the type ‘A’ cuttings did not sprout.

(i) Why were the type ‘B’ cuttings able to grow as sugarcane but type ‘A’ could not?

Answer:
Type ‘B’ cuttings were able to grow because they contained nodes with buds or meristematic tissue capable of cell division and growth. Type ‘A’ lacked these growing regions.

(ii) What difference was present in type ‘B’ compared to type ‘A’?

Answer:
Type ‘B’ had nodes with buds or meristematic tissue, whereas type ‘A’ did not.

(iii) What observation or measurement was made to determine whether this change had an effect?

Answer:
The sprouting and growth of new shoots and roots were observed to determine the effect.

(iv) What parameters should be kept the same for both types of cuttings to ensure a fair comparison?

Answer:
Both cuttings should receive the same amount of water, sunlight, soil, temperature, nutrients, and time for growth.

11. During the discussion in class, Rohan gives a statement that, “A tissue is a group of similar cells performing similar functions”. But Rajiv counter argues that, “this is true in case of simple tissues but little different in case of complex tissues”. Provide your explanation in view of the discussion in class.

Answer:
Rohan’s statement is correct for simple tissues because simple tissues are made of similar types of cells performing the same function. Examples are parenchyma, collenchyma, and sclerenchyma.

Rajiv is also correct because complex tissues are made of different types of cells working together to perform a common function. For example, xylem and phloem contain different kinds of cells that help in transport.

12. Coconut husk fibres are used for mats which are tough and fibrous. Which tissue has structural features suitable for providing this strength? Explain why living parenchyma couldn’t serve the same purpose.

Answer:
Sclerenchyma tissue provides the toughness and strength in coconut husk fibres. Its cells have thick lignified walls that make them hard and strong.

Living parenchyma cells have thin walls and are mainly meant for storage and metabolic activities. They are soft and cannot provide the same mechanical strength as sclerenchyma.

13. Vibha claims to her friend Neha that, “Meristematic cells are located only at the root and shoot apices”. What do you think about this statement? What question can Neha ask Vibha to help her understand further if the statement is incorrect?

Answer:
The statement is incorrect because meristematic tissues are not found only at root and shoot apices. They are also present in the lateral meristem (cambium) and intercalary meristem.

Neha can ask:
“If meristematic tissue is present only at the tips, then how does the stem increase in thickness or how do grasses regrow after cutting?”

14. A plant cell and an animal cell are of the same size.

(i) Which cell will have a larger vacuole? Give reasons.

Answer:
The plant cell will have a larger vacuole. Plant cells usually contain a large central vacuole that stores water, food, and wastes and helps maintain turgidity.

(ii) What assumptions are you making to answer the question above?

Answer:
The assumption is that both cells are mature and healthy cells under normal conditions. If the cells are immature or specialised differently, the vacuole size may vary.

15. A textbook states, “Each plant tissue performs only one specific function”. What questions would you ask to critically examine the correctness of this statement? What examples of tissues would you take to find out the answers to these questions?

Answer:

Questions that can be asked are:

• Does every plant tissue perform only one function?
• Can a tissue perform more than one function at the same time?
• Do some tissues provide both support and transport?
• Can the same tissue behave differently in different plants or conditions?

Examples of tissues to examine:

• Parenchyma: stores food and also performs photosynthesis when chlorophyll is present.
• Collenchyma: provides support and flexibility.
• Xylem: transports water and also provides mechanical strength.
• Phloem: transports food throughout the plant.

These examples show that many plant tissues perform more than one function.

Visit a doctor and find out what happens in ligament rupture, cartilage rupture and fracture of bones. How can we reduce the risk by changing our lifestyle and nutritional balance?

Answer:

• Ligament rupture: A ligament gets stretched or torn, causing pain, swelling, and instability in the joint.
• Cartilage rupture: Damage to cartilage causes pain, stiffness, and difficulty in movement because cartilage cushions the joints.
• Fracture of bones: A bone cracks or breaks due to injury, accident, or weakness.

Ways to reduce the risk:

• Eat a balanced diet rich in calcium, protein, vitamin D, and minerals.
• Exercise regularly to strengthen bones and muscles.
• Maintain proper body weight.
• Avoid smoking and excessive junk food.
• Use proper posture and protective equipment during sports and physical activities.
• Get enough sunlight for vitamin D production.

Activity: Observation of Tendons

(i) Sit with your feet flat on the floor.
(ii) Place your fingers on the back of your ankle just above the heel.
(iii) Point your toes down and up, and you will feel the tendon moving.

Observation:
The tendon can be felt moving when the foot is moved. Tendons are strong connective tissues that attach muscles to bones and help in body movement. They can withstand strong pulling forces during movement.