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Exploration | Class 9 Science | Chapter 3 - Tissues in Action | Q&A
CHAPTER 3

Tissues in Action

Questions & Solutions | Exploration | Class 9 Science

Think It Over Page 48

Think It Over
How is the study of cells and tissues significant for understanding the life processes and human welfare? How are tissues in plants and animals different, and why? How is the division of labour at various levels of organisation in multicellular organisms correlated with their structure and function?
Solution
The study of cells and tissues helps us understand how organisms function, heal, and respond to diseases. Plant tissues have cell walls for support; animal tissues lack cell walls for flexibility. Division of labour allows different tissues to perform specific functions efficiently, increasing overall organism survival.

Activity 3.1 Page 49

Activity 3.1
Let us design experiments. Take two glass jars and fill them with water. Take two onion bulbs and place one in each jar. Observe the growth of roots for a few days. Measure the length of roots on days 1, 2 and 3. On day 3, cut the root tips of the onion bulb in Jar B by about 1 cm. After this, observe the growth of roots in both the jars, measure their lengths for four more days (day 4 onwards), and record your observations in Table 3.1. What trend do you observe? What do you infer?
Solution
Roots in Jar A continue to grow in length. Roots in Jar B stop growing after the tips are cut. This shows that roots grow only from their tips, which contain actively dividing cells (apical meristem).

Meet a Scientist

Page 49 - B.G.L. Swamy
B.G.L. Swamy was a renowned Indian botanist known for his contributions to plant morphology and anatomy. His book, Hasuru Honnu, is a popular book in Kannada language. It is a blend of science, satire and culture. The book describes the botanical excursion in the forests of Western Ghats and is a treasure of plant descriptions, utilisation, conservation practices, botanical folklores and myths. The book won the Kendra Sahitya Akademi Award in 1978.
Solution
B.G.L. Swamy contributed significantly to plant morphology and anatomy. His book "Hasuru Honnu" blends science with culture and won the Kendra Sahitya Akademi Award.
Page 57 - Sipra Guha Mukherjee
Sipra Guha Mukherjee in collaboration with S.C. Maheshwari made a breakthrough discovery in the area of plant tissue culture. Their research led to the development of a complete plant through another culture, using an artificial nutrient medium under controlled laboratory conditions. This pioneering work greatly contributed to crop improvement and brought significant progress in modern agriculture.
Solution
Sipra Guha Mukherjee and S.C. Maheshwari pioneered plant tissue culture, enabling the development of complete plants from anther culture, advancing crop improvement and modern agriculture.
Page 62 - F.C. Steward
In 1958, F. C. Steward demonstrated that even single cells from vascular phloem of carrot retain the ability to regenerate whole plants. He was the first person to do so! He and his team conducted an experiment using the phloem cells of carrot. He grew these cells in a nutrient medium containing simple sugars and hormones under appropriate conditions. He observed that these phloem cells divided to form a mass of cells, which gradually divided and differentiated into a complete plant. This is known as totipotency.
Solution
F.C. Steward demonstrated totipotency in carrot phloem cells, showing that single plant cells can regenerate into whole plants, laying the foundation for plant tissue culture.

Pause and Ponder

Page 53 (Q1)
You may have noticed that fibres of coconut husk are hard and brittle, whereas the leaf stalks of coriander are soft and flexible. Find out the reason.
Solution
Coconut husk fibres contain sclerenchyma tissue with lignin deposits, making them hard and brittle. Coriander leaf stalks contain collenchyma tissue with pectin deposits, providing flexibility.
Page 54 (Q2)
Why do you think that a thick cuticle on the outer wall of epidermis is advantageous for a plant living in the desert but disadvantageous for a plant living underwater?
Solution
A thick cuticle reduces water loss in desert plants. Underwater plants do not need to prevent water loss; a thick cuticle would hinder gas exchange and absorption of nutrients from water.
Page 54 (Q3)
Once water is absorbed by plant roots, it has to travel against gravity through xylem. How do the 'dead' cells of the xylem work together with the living cells of leaves at the top to keep the water moving?
Solution
Transpiration from leaves creates a suction pull that draws water upward through xylem vessels. The cohesive and adhesive properties of water help maintain the continuous water column.
Page 54 (Q4)
What do you think will happen if there were no stomata in the epidermis of the stem or leaves?
Solution
Without stomata, gas exchange (CO₂ for photosynthesis, O₂ for respiration) and transpiration would be severely limited, affecting photosynthesis, water transport, and temperature regulation.
Page 60 (Q5)
Look at the picture given below (Fig. 3.17). Carefully observe the various poses of classical and folk dances of India. Can you identify which joints are involved? Also, what type of movement each joint allows?
Solution
Shoulder (ball and socket) allows circular movement; elbow and knee (hinge) allow bending in one direction; neck (pivot) allows side-to-side rotation; wrist and ankle allow complex movements.

Ready to Go Beyond

Page 54
In young plants, the outer protective layer is a single-layered epidermis. As plants grow older, some cells below the epidermis of the stem develop the ability to divide, act as lateral meristematic cells and form the cork cambium. The division of cork cambium cells gives rise to cork cells. Cork cells are dead, compactly arranged, and contain a substance which makes them impermeable to water and gases. This forms the bark of the tree.
Solution
Cork cambium (lateral meristem) produces cork cells that replace the epidermis in older stems and roots. Cork cells are dead, contain suberin, and form the protective bark.
Page 60
Stem cells in the bone marrow are special cells that can divide and make new cells. In a bone marrow transplant, stem cells from a healthy person are given to patients who have blood cancers like Leukemia or disorders, such as Thalassemia.
Solution
Bone marrow stem cells are undifferentiated cells that can produce various blood cells. Bone marrow transplants are used to treat blood cancers and genetic blood disorders.

Bridging Science and Society

Page 61
Yoga, described in ancient Indian texts includes physical postures, breathing and meditation. Research shows it improves flexibility, posture and breathing, reduces stress, and helps prevent lifestyle diseases. Every year, 21st June is observed as the International Yoga Day to promote role of Yoga in health and well-being.
Solution
Yoga improves musculoskeletal health, flexibility, posture, breathing, and reduces stress. International Yoga Day is celebrated on June 21st annually.
Page 62
In nature, plant pathologists have observed a disease in plants called crown gall disease (Fig. 3.20). In this disease, tumour-like swellings develop on the stems due to rapid and uncontrolled cell division. The disease is caused by a bacterium called Agrobacterium tumefaciens. Instead of only trying to cure this disease, scientists studied how a bacterium transfers its genetic material into plant cells. This knowledge was later used in plant tissue culture and genetic engineering. Today, Agrobacterium is used as a tool to introduce useful genes into plants for the production of valuable phytochemicals, improved crops and disease-resistant varieties.
Solution
Agrobacterium tumefaciens causes crown gall disease by transferring its DNA into plant cells. This mechanism is now used in genetic engineering to introduce beneficial genes into plants.

Activity 3.2 Page 56

Activity 3.2
Recall everyday experiences given in the first column of Table 3.3. Write your observations and questions in your notebook. Compare your observations with the observations given in Table 3.3. The everyday experiences mentioned above are related to blood and its components.
Solution
RBCs contain haemoglobin and carry oxygen. Platelets help in blood clotting. WBCs fight infections. Increased breathing during exercise supplies more oxygen to muscles. Pus formation indicates WBC activity at infection sites.

Activity 3.3 Page 57

Activity 3.3
Perform the actions given in Table 3.4. Record your experiences and compare them with the experiences given in Table 3.4. Study their functions and identify the connective tissues (Fig. 3.12).
Solution
Bone: hard and rigid, provides strength. Cartilage: soft and flexible, cushions joints. Tendon: connects muscle to bone. Ligament: connects bone to bone, limits excessive movement.

Activity 3.4 Page 59

Activity 3.4
Let us investigate: What percentage of total body weight comes from bones and muscles? Step on a weighing scale and record your total body weight. Use online references to find average bone and muscle mass percentage for your age, gender, and an Indian body type. Multiply your total body weight by the bone percentage and muscle percentage to estimate the weight of your bones and muscles.
Solution
On average, adult males have about 40-50% muscle, adult females have 30-40% muscle, and bone mass is about 12-15% for all adults. Bone and muscle mass differ between individuals due to genetics, diet, exercise, and overall health.

Activity 3.5 Page 59

Activity 3.5
Move different parts of your body and observe what movement(s) it can make. Complete Table 3.5. You may have noticed that some parts of our body can move easily in many directions, while others move only in a single direction. Why does this happen? The difference is due to the types of joints present.
Solution
Ball and socket joint (shoulder, hip) allows movement in multiple directions. Hinge joint (elbow, knee) allows movement in one plane. Pivot joint (neck) allows rotation. Fixed joints (skull) allow no movement.

END-OF-CHAPTER EXERCISES Pages 64-67

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.
Solution
Option (iii) is correct. Meristematic cells have thin walls, dense cytoplasm, and a large prominent nucleus, allowing continuous and rapid 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
Solution
Option (ii) is correct. Phloem transports food from leaves to other parts of the plant.
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.
Solution
Option (iii) is correct. Thin epithelium allows rapid diffusion, absorption, and secretion of materials.
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?
Solution
In normal jumps, knees and ankles bend to absorb shock and provide thrust. In straight-leg jumps, joints remain stiff, reducing shock absorption and increasing impact.
5.
Which type of joint is involved when you bend your knees and ankles? (i) Ball and socket (ii) Hinge (iii) Pivot
Solution
Option (ii) is correct. Knee and ankle joints are hinge joints, allowing bending and straightening in one plane.
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. B. Assertion: Cardiac muscle can contract continuously without fatigue. Reason: Cardiac muscle cells have a high number of mitochondria and an abundant blood supply. 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. D. Assertion: In a hinge joint, movement occurs primarily in one plane. Reason: The bone ends are shaped to allow sliding in all directions.
Solution
A: (iii) A is true, R is false (lung epithelium is single-layered, not multi-layered).
B: (i) Both true, R explains A correctly.
C: (iii) A is false (tendons connect muscle to bone, not bone to bone), R is true.
D: (iii) A is true, R is false (hinge joint allows movement in one plane, not all directions).
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 the Table 3.7. (i) Analyse the graph in terms of the diameter of the stem over time. (ii) What is the relation between the diameter of the teak tree to the annual rings formed? (iii) Which specialised tissue is responsible for the girth of the stem and where is it located?
Solution
(i) Diameter increases with age. (ii) Number of annual rings equals the age of the tree. (iii) Lateral meristem (cambium) located between xylem and phloem is responsible for increase in girth.
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 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?
Solution
(i) Protection and transport of food (phloem is in bark). (ii) Cambium and xylem. (iii) Transport of water and minerals (xylem). (iv) Assumption: Only bark is removed, not deeper layers. If deeper layers are damaged, the tree may die.
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.
Solution
Collenchyma provides flexibility. If replaced by sclerenchyma (which is rigid and dead), the stem would become brittle and break easily under stress.
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 difference was present in type 'B' compared to type 'A'? (iii) What observation or measurement was made to determine whether this change had an effect? (iv) What parameters should be kept the same for both types of cuttings to ensure a fair comparison?
Solution
(i) Type 'B' likely had nodes (meristematic tissue) while type 'A' did not. (ii) Type 'B' contained nodes or buds. (iii) Sprouting and root development were observed. (iv) Same soil, water, light, temperature, and cutting length.
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.
Solution
Simple tissues are made of one cell type (e.g., parenchyma). Complex tissues (xylem, phloem) are made of multiple cell types working together to perform a common function.
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.
Solution
Sclerenchyma (with lignin deposition) provides strength and hardness. Living parenchyma cells have thin walls and would not provide the required structural support.
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?
Solution
The statement is incorrect. Meristematic cells are also present at nodes (intercalary meristem) and in a ring (lateral meristem). Neha could ask: "What about the increase in girth of the stem?"
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?
Solution
(i) Plant cell will have a larger vacuole (central vacuole) for storage and turgor pressure. (ii) Assumption: Both are typical mature cells; animal cells may have small temporary vacuoles.
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?
Solution
Questions: "Does parenchyma only store food, or does it also perform photosynthesis?" "Does xylem only transport water, or does it also provide support?" Examples: Parenchyma (stores food, performs photosynthesis), Xylem (transports water, provides mechanical support).

Chapter Summary

  • Tissues are groups of similar cells that work together to perform specific functions.
  • Plant tissues are classified as meristematic (dividing) and permanent (non-dividing).
  • Simple permanent tissues: parenchyma (storage), collenchyma (flexibility), sclerenchyma (strength).
  • Complex permanent tissues: xylem (water transport) and phloem (food transport).
  • Animal tissues: epithelial (covering), connective (support), muscular (movement), nervous (control).
  • Epithelial tissue lines organs and body surfaces.
  • Connective tissue includes bone, cartilage, blood, tendons, and ligaments.
  • Muscular tissue includes skeletal (voluntary), smooth (involuntary), and cardiac (heart).
  • Nervous tissue consists of neurons that transmit impulses.

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Chapter 3: Tissues in Action — All Questions with Solutions

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