Class 9 Science

Chapter 3 Solutions — Tissues in Action

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Solutions

Overview

Step-by-step NCERT solutions for Tissues in Action (Chapter 3, NCERT Class 9 Science) — every question and answer worked out in full, not just the final result. You can also read the Tissues in Action textbook chapter.

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What these solutions cover

All 15 questions in Tissues in Action are solved in the PDF. Here's what's inside, exercise by exercise:

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1.
Meristematic tissues divide repeatedly. Which 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.
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
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.
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?
5.
Which type of joint is involved when you bend your knees and ankles?
- (i) Ball and socket
- (ii) Hinge
- (iii) Pivot
6.
In each of the following cases (A, B, C and D), choose the correct option:
- (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…
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: S.No. | Age (Years) | DBH (cm) | Annual rings 1 | 5 | 4 | 5 2 | 10 | 8 | 10 3 | 20 | 24 | 20 4 | 25 | 28 | 25 5 | 30 | 32 | 30 6 | 40 | 40 | 40 (i) Analyse the graph in terms of the…
8.
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 (Fig. 3.22). 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…
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.
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' (Fig. 3.23). 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?
- (ii) What…
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.
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.
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?
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 to answer the question above?
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?

Sample

Worked examples

3 questions from Tissues in Action, solved step by step.

Revise, Reflect, Refine

Meristematic tissues divide repeatedly. Which 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.

Meristematic tissues are responsible for growth in plants and must divide repeatedly.

Option (i) is incorrect: meristematic cells have thin, not thick, cell walls — thick walls would restrict division.

Option (ii) is incorrect: meristematic cells have very small or absent vacuoles; large vacuoles are a feature of mature parenchyma cells, not actively dividing cells.

Option (iii) is correct: meristematic cells have thin, flexible cell walls that allow the cell to expand and divide. Their dense cytoplasm and large, prominent nucleus reflect active metabolism and the genetic machinery needed for repeated cell division.

Option (iv) is incorrect: meristematic cells are undifferentiated — they have not yet taken on any specialised function. Functionally differentiated cells have lost the ability to divide.

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

Revise, Reflect, Refine

If a plant is unable to transport food from leaves to roots which tissue is malfunctioning? (i) Xylem (ii) Phloem (iii) Epidermis (iv) Sclerenchyma

In plants, transport of food (sugars and other organic solutes) manufactured in leaves by photosynthesis to non-photosynthetic parts such as roots is called translocation.

Option (i) is incorrect: xylem transports water and dissolved minerals from roots upward to leaves and shoots — it does not carry food.

Option (ii) is correct: phloem is the vascular tissue responsible for translocation of food from source (leaves) to sink (roots, stems, fruits, seeds). Sieve tube elements and companion cells are the functional units of this transport. If phloem is malfunctioning, food cannot reach the roots.

Option (iii) is incorrect: epidermis is the outermost protective layer and is not involved in long-distance food transport.

Option (iv) is incorrect: sclerenchyma provides mechanical support through dead, thick-walled cells and plays no role in food transport.

Answer: (ii) Phloem

Revise, Reflect, Refine

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.

Epithelial tissues lining internal organs (e.g., alveoli in the lungs, walls of the small intestine, kidney tubules) must permit rapid transfer of substances such as oxygen, carbon dioxide, nutrients, and wastes between the organ cavity and the surrounding blood vessels.

Option (i) is incorrect: storage is the function of cells such as parenchyma or adipose tissue, not epithelium.

Option (ii) is incorrect: maximum mechanical strength is provided by stratified (multi-layered) epithelia such as skin, not by single-layered epithelia lining internal organs.

Option (iii) is correct: the rate of diffusion is inversely proportional to the distance travelled. A layer that is only one or a few cells thick minimises the diffusion distance, allowing substances to cross the epithelium rapidly. This is critical for gas exchange in the alveoli and nutrient absorption in the intestinal villi.

Option (iv) is incorrect: friction reduction is a secondary role in certain locations (e.g., ciliated epithelium moves mucus), but it is not why the epithelium is so thin.

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

All 15 questions in Tissues in Action are solved step by step in the Solutions PDF above.

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Chapter 3 Solutions — Tissues in Action

Overview

What these solutions cover

Revise, Reflect, Refine

Worked examples

If a plant is unable to transport food from leaves to roots which tissue is malfunctioning? (i) Xylem (ii) Phloem (iii) Epidermis (iv) Sclerenchyma

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.

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