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Tissues in Action

CBSE · Class 9 · Science

NCERT Solutions for Tissues in Action — CBSE Class 9 Science.

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75 Questions Solved · 11 Sections

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Think It Over

1How is the study of cells and tissues significant for understanding the life processes and human welfare?Show solution
The study of cells and tissues helps us understand how living organisms grow, develop and perform life processes. Since cells are the basic unit of life and tissues are groups of cells working together, this study explains the structure–function relationship in plants and animals. It is also significant for human welfare because knowledge of tissues helps researchers understand growth, repair, movement, transport and control in the body, and it supports advances such as plant tissue culture, crop improvement, and medical use of stem cells and transplants.

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2How are tissues in plants and animals different, and why?Show solution
Plant and animal tissues are different because plants and animals have different body structures, life styles and needs. Plants are usually fixed in one place, so they need tissues for support, protection, transport of water and food, and growth at certain regions. Animals move from place to place, so they have tissues for movement, coordination, sensory functions, and internal support. Also, plant cells have a cell wall, while animal cells do not, so plant tissues are generally more rigid and animal tissues are more flexible. These differences arise because the structure and function of tissues are adapted to the way plants and animals live.

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3How is the division of labour at various levels of organisation in multicellular organisms correlated with their structure and function?Show solution
In multicellular organisms, there is a division of labour at different levels. Cells of similar type form a tissue, tissues form organs, organs form organ systems, and organ systems together form the organism. Each level is specialised for certain functions, so the body works more efficiently. For example, in animals muscle tissue helps movement and nervous tissue carries messages, while in plants xylem transports water and minerals and phloem transports food. Thus, the structure of each tissue or organ is closely related to its function, and specialisation increases efficiency and allows complex life processes.

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Activity 3.1: Let us design experiments

1Take two glass jars or couplin jars and fill them with water.Show solution

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2Now, take two onion bulbs and place one in each jar, as shown in Fig. 3.1.Show solution

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3Observe the growth of roots in both bulbs for a few days.Show solution

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4Measure the length of roots on days 1, 2 and 3.Show solution

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5On day 3, cut the root tips of the onion bulb in Jar B by about 1cm1\mathrm{cm}. After this, observe the growth of roots in both the jars, measure their lengthsShow solution

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6What trend do you observe in the data you recorded in Table 3.1? Are your observations similar to those presented in the graphical representation (Fig. 3.2)? What do you infer?Show solution
The data show that roots in Jar A continue to grow in length, but roots in Jar B stop growing after the tips are cut. Yes, this is similar to the graph in Fig. 3.2. The inference is that roots grow only from their tips because the tips contain actively dividing cells. This means the apical meristem at the root tip is responsible for growth in length.

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Pause and Ponder

1You 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.Show solution
Coconut husk fibres are made of sclerenchyma. Sclerenchyma cells have thick, lignified walls, so they are hard and brittle. Coriander leaf stalks are soft and flexible because they have more collenchyma/parenchyma, which provide flexibility instead of hardness.

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2Why 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?Show solution
A thick cuticle is useful for a desert plant because it reduces water loss by transpiration, helping the plant survive in dry conditions. But underwater plants do not need to conserve water, so a thick cuticle is unnecessary and disadvantageous because it can hinder exchange with the surrounding water and is not helpful for water conservation.

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3Once 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?Show solution
The dead xylem cells form tubes that transport water upward from the roots. At the top, the living cells of the leaves lose water through transpiration. This creates a transpiration pull that helps draw more water up through the xylem against gravity. So, xylem conducts water, and transpiration in the leaves keeps the water moving continuously.

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4What do you think will happen if there were no stomata in the epidermis of the stem or leaves?Show solution
If there were no stomata in the epidermis of stems or leaves, the plant would have serious problems in gas exchange and transpiration. Carbon dioxide would not enter easily for photosynthesis, oxygen exchange would be affected, and transpiration pull would be reduced, so water transport would also be disturbed. The plant would also lose an important way of removing water vapour and wastes.

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5Look 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?Show solution
The poses of dances involve movements at different joints such as the shoulder, elbow, wrist, neck, hip, knee and ankle. The shoulder and hip are ball-and-socket joints, allowing movement in many directions. The elbow, knee, ankle and finger joints mainly act as hinge joints, allowing bending and straightening in one plane. The neck has a pivot joint, which allows the head to turn side to side. These joints make the various dance movements possible.

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Activity 3.2: Let us understand further

1Recall everyday experiences given in the first column of Table 3.3.Show solution

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2Write your observations and questions in your notebook.Show solution

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3Compare your observations with the observations given in Table 3.3.Show solution

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4What causes blood to clot?Show solution
Platelets help in blood clotting at the site of injury.

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Activity 3.3: Let us perform

1Perform the actions given in Table 3.4.Show solution

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2Record your experiences and compare them with the experiences given in Table 3.4.Show solution

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3Study their functions and identify the connective tissues (Fig. 3.12).Show solution

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Activity 3.4: Let us investigate

1Step on a weighing scale and record your total body weight.Show solution

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2Use online references or health resources to find average bone and muscle mass percentage for your age, gender, and an Indian body type (these may vary by ethnicity). For example, on average, adult males have about 40-50 per cent muscle, and adult females have ∼30−40\sim 30 - 40 per cent muscle, although bone mass is about 12-15 per cent for all adults.Show solution

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3Multiply your total body weight by the bone percentage and muscle percentage to estimate the weight of your bones and muscles.Show solution

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4Record the estimated bone weight and muscle weight, and compare them with your total body weight.Show solution

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5Compare your findings with those of your classmates and calculate the class average.Show solution

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6Discuss why do bone and muscle mass differ between individuals, and how do they contribute to the overall body weight?Show solution
Bone and muscle mass differ between individuals because of differences in age, gender, body composition, nutrition, and physical activity. For example, adult males usually have a higher muscle percentage than adult females, while bone mass is about 12–15% in adults on average. Together, bones and muscles contribute a large part of the body weight: bones give support and rigidity, while muscles provide movement and also add to body mass. Their proportions vary from person to person, so total body weight differs.

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Activity 3.5: Let us observe

1Move different parts of your body and observe what movement(s) it can make.Show solution

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2You 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. A joint is a junction between two or more bones. Joints allow movement but they cannot move the bones on their own. So, what actually causes the bones to move?Show solution
The bones move because of the action of muscles, especially the skeletal muscles attached to bones by tendons. Joints only allow movement; they do not move the bones by themselves. When a muscle contracts, it pulls on the bone through the tendon, producing movement at the joint. Different kinds of joints also limit the direction of movement, so some body parts move in many directions while others move in only one direction.

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3Why does this happen?Show solution
This happens because the body has different types of joints. Some joints, like the shoulder and hip, are ball-and-socket joints, so they allow movement in many directions. Others, like the elbow, knee and ankle, are hinge joints, so they allow movement mainly in one direction. Joints do not move the bones themselves; muscles cause the movement.

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Revise, Reflect, Refine

1Meristematic tissues divide repeatedly. What property of their cells allows them to do this?Show solution
Meristematic cells divide repeatedly because they have thin cell walls, dense cytoplasm, and a large prominent nucleus. These features support rapid cell division and continuous growth.

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2If a plant is unable to transport food from leaves to roots which tissue is malfunctioning?Show solution
Food is transported from leaves to roots by phloem. So if the plant cannot transport food, phloem is malfunctioning.

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3Why are the epithelial tissues that line an animal's internal organs usually only one or a few cells thick?Show solution
Epithelial tissues lining internal organs are usually only one or a few cells thick so that substances can pass across them quickly and efficiently. Thin layers are best for rapid exchange of gases, nutrients and wastes.

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4You 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?Show solution
In the straight-leg jump, the knees and ankles remain stiff, so there is very little bending at those joints and the hips also move less naturally. In the normal jump, the ankles, knees and hips bend to help absorb the force and make the jump smoother. So the difference is that the normal jump uses flexion at the joints, while the straight-leg jump keeps them rigid.

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5Which type of joint is involved when you bend your knees and ankles?Show solution
When you bend your knees and ankles, the joints involved are hinge joints, because they allow movement mainly in one direction.

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6In each of the following cases (A, B, C and D), choose the correct option as given below:Show solution
- A: Epithelium for gas exchange is true, but the reason is false because gas exchange needs a single thin layer, not multiple tall layers. So (iii).
- B: Cardiac muscle can contract continuously without fatigue is true, and the reason is also true and explains it. So (i).
- C: Tendons connect muscle to bone, not bone to bone, so the assertion is false. The reason is true. So (iv).
- D: In a hinge joint, movement is mainly in one plane is true. The reason is false because the bone ends are not shaped to allow sliding in all directions. So (iii) would be expected for D if using the standard list, but since the correct matching from the statement is that the assertion is true and the reason is false, the option is (iii).

Therefore the answers are: A-iii, B-i, C-iv, D-iii.

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7Plot 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.Show solution
Plot a graph with age of the tree on the x-axis and diameter and number of annual rings on the y-axis using the data points:

- Age 5 years → diameter 4 cm, rings 5
- Age 10 years → diameter 8 cm, rings 10
- Age 20 years → diameter 24 cm, rings 20
- Age 25 years → diameter 28 cm, rings 25
- Age 30 years → diameter 32 cm, rings 30
- Age 40 years → diameter 40 cm, rings 40

Join the points smoothly or as separate line graphs for diameter and annual rings. The graph will show an increasing trend for both diameter and rings with age.

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7(i)Analyse the graph in terms of the diameter of the stem over time and share the interpretation.Show solution
The graph shows that the diameter of the stem increases with age. In young trees the increase may be slower, and with time the trunk becomes thicker. This means the tree grows in girth as it gets older, and the increase in diameter reflects the activity of lateral meristem.

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7(ii)What is the relation between the diameter of the teak tree to the annual rings formed?
7(iii)Which specialised tissue is responsible for the girth of the stem and where is it located?
8In 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:
8(i)Which function(s) of the tree is/are hampered by debarking?
8(ii)Which plant tissue would be affected by further damage to the tree trunk even after debarking?
8(iii)Which function of the tree would be hampered if the tissues beneath the bark were severely damaged?
8(iv)What assumptions are you making to answer the questions above? How would the answer change if your assumptions are also changed?
9Aamrapali 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.
10Sohan 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.
10(i)Why were the type 'B' cuttings able to grow as sugarcane but type 'A' could not?
10(ii)What difference was present in type 'B' compared to type 'A'?
10(iii)What observation or measurement was made to determine whether this change had an effect?
10(iv)What parameters should be kept the same for both types of cuttings to ensure a fair comparison?
11During 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.
12Coconut 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.
13Vibha 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?
14A plant cell and an animal cell are of the same size.
14(i)Which cell will have a larger vacuole? Give reasons.
14(ii)What assumptions are you making to answer the question above?
15A 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?

The Journey Beyond

1Visit 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?
2Perform the following activity.
3Reflect on any of the physical practices you are familiar with, such as yoga, kabaddi, etc. How would it support bone and muscle health?
4Reflect on any gardening methods you know, such as pruning, grafting, irrigation or crop rotation. How does each practice support the healthy functioning of plant tissues like meristems, conducting tissues or supporting tissues?
5Turn a nature walk into a research project.
6Study various dance forms of different tribal communities across the country. Each student learn and experience at least five steps. Observe the joint movements involved in performing these steps and then develop a dance or drama on the concept of joint movements. Perform this at the school's annual function so that students from different grades can learn from it.
1Sit with your feet flat on the floor.
2Place your fingers on the back of your ankle just above the heel (Fig. 3.24).
3Point your toes down and up, and you will feel the tendon moving.
(i)Observe different leaves and study their adaptations for various environments, such as desert, very moist or aquatic habitats.
(ii)Consult an elder community resource persons about their knowledge on different plant leaves, such as leaves that remain fresh for a long time, repel water or deter insects. Find out their traditional uses, such as making plates, preparing cooling wraps or functioning as insect repellents.
12Will it be possible to obtain a complete animal from an animal cell like plants? If yes, what would be the advantages and challenges of this development?

Think as a Scientist

(a)What do you conclude about the characteristics of phloem cells of carrot?
(b)In which of the three combinations would you obtain the highest and lowest biomass? What could be the possible reason(s) for this observation?
(c)Will you get the same results if you culture animal cells instead of carrot cells?
(d)Think and mention any two commercial applications of the study above.

Activity 3.6: Let us investigate

1What percentage of total body weight comes from bones and muscles?

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Frequently Asked Questions

What are the important topics in Tissues in Action for CBSE Class 9 Science?
Tissues in Action covers several key topics that are frequently asked in CBSE Class 9 board exams. Focus on the core concepts listed on this page and practise related questions to build confidence.
How to score full marks in Tissues in Action — CBSE Class 9 Science?
Understand the core concepts first, then work through the 89 practice questions available for this chapter. Revise formulas and definitions regularly, and use flashcards for quick recall before the exam.
Where can I get free NCERT Solutions for Tissues in Action Class 9 Science?
This page has free step-by-step NCERT Solutions for every exercise question in Tissues in Action (CBSE Class 9 Science) — written the way examiners award marks: given, formula, working, answer.

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