Class 9 › Science › Exploration Tissues in Action Class 9 Science · Exploration · Chapter 3
Summary Questions & answers Practise this chapter → Building on the cell, this chapter explains how similar cells group together as tissues so that a multicellular body can share out work (division of labour) and grow more efficiently. Because plants are usually fixed in place and make their own food while animals move and ingest food, their tissues differ. Plant tissues are either meristematic (actively dividing) or permanent (specialised, mostly non-dividing). There are three meristems — apical (at root and shoot tips, gives growth in length), lateral (a ring inside the stem, gives growth in girth and forms annual rings), and intercalary (at the base of internodes, lets grasses regrow after cutting). When meristematic cells stop dividing and become specialised, the process is called differentiation, forming permanent tissues. Permanent tissues are simple (one cell type — parenchyma stores food, collenchyma gives flexible support, sclerenchyma gives hard rigid strength) or complex (xylem carries water and minerals upward; phloem carries food). The protective epidermis bears a waxy cuticle, root hairs and stomata. Plant tissues are organised into dermal, ground and vascular tissue systems. Animal tissues are of four kinds: epithelial (covering and lining; flat, columnar, glandular or sensory), connective (blood, bone, cartilage, tendons, ligaments — cells set in a matrix), muscular (skeletal/voluntary striated, smooth/involuntary, and cardiac in the heart) and nervous (neurons with cell body, dendrites and axon). Finally, bones, muscles, joints, cartilage, tendons and ligaments form the musculoskeletal system controlled by the nervous system, with joints such as ball-and-socket, hinge, pivot and fixed types.
Meristematic tissue
Tissue of small, thin-walled, dividing cells with dense cytoplasm and no vacuole, responsible for plant growth.
Differentiation
The process by which dividing meristematic cells become specialised permanent cells for support, transport or storage.
Xylem and phloem
Complex permanent (vascular) tissues — xylem carries water and minerals upward, phloem carries food made in leaves to the rest of the plant.
Epithelial tissue
Animal tissue forming the outer covering of the body and the lining of internal organs; cells are closely packed.
Connective tissue
Tissue that connects and supports other tissues (blood, bone, cartilage, tendons, ligaments); cells lie in a matrix.
Neuron
The cell of nervous tissue, with a cell body, dendrites and an axon, specialised to receive and transmit messages.
Musculoskeletal system
The system of bones, muscles, joints, cartilage, tendons and ligaments that supports the body and produces movement under nervous control.
Q1 Why are plant and animal tissues different? Answer Q2 Name the three types of meristematic tissue and what each does. Answer Q3 What is differentiation in plants? Answer Q4 Compare parenchyma, collenchyma and sclerenchyma. Answer Q5 How do xylem and phloem differ in function? Answer Q6 List the four types of animal tissue. Answer Q7 Why is blood considered a connective tissue? Answer Q8 Distinguish the three kinds of muscle. Answer Q9 Name the parts of a neuron and their roles. Answer Q10 Match each joint type with a movement: shoulder, elbow, neck, skull. Answer Q1 How is the study of cells and tissues significant for understanding the life processes and human welfare? Answer Q2 How are tissues in plants and animals different, and why? Answer Q3 How is the division of labour at various levels of organisation in multicellular organisms correlated with their structure and function? Answer Q1 1. 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. Answer Q1 2. 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? Answer Q2 3. 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? Answer Q3 4. What do you think will happen if there were no stomata in the epidermis of the stem or leaves? Answer Q1 5. 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? Answer Q1 (a) What do you conclude about the characteristics of phloem cells of carrot? Answer Q2 (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? Answer Q3 (c) Will you get the same results if you culture animal cells instead of carrot cells? Answer Q4 (d) Think and mention any two commercial applications of the study above. Answer Q1 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 Q2 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 Q3 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 Q4 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 Q5 5. Which type of joint is involved when you bend your knees and ankles? (i) Ball and socket (ii) Hinge (iii) Pivot Answer Q6 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 Q7 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. 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 Q8 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. 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 Q9 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. 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 Q10 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. 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 (i) Analyse the graph in terms of the diameter of the stem over time and share the interpretation. Answer Q11 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. 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 (ii) What is the relation between the diameter of the teak tree to the annual rings formed? Answer Q12 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. 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 (iii) Which specialised tissue is responsible for the girth of the stem and where is it located? Answer Q13 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? Answer Q14 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: (ii) Which plant tissue would be affected by further damage to the tree trunk even after debarking? Answer Q15 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: (iii) Which function of the tree would be hampered if the tissues beneath the bark were severely damaged? Answer Q16 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: (iv) What assumptions are you making to answer the questions above? How would the answer change if your assumptions are also changed? Answer Q17 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 Q18 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? Answer Q19 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. (ii) What difference was present in type ‘B’ compared to type ‘A’? Answer Q20 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. (iii) What observation or measurement was made to determine whether this change had an effect? Answer Q21 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. (iv) What parameters should be kept the same for both types of cuttings to ensure a fair comparison? Answer Q22 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 Q23 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 Q24 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 Q25 14. A plant cell and an animal cell are of the same size. (i) Which cell will have a larger vacuole? Give reasons. Answer Q26 14. A plant cell and an animal cell are of the same size. (ii) What assumptions are you making to answer the question above? Answer Q27 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 Q1 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 Q2 Perform the following activity. (i) Sit with your feet flat on the floor. (ii) Place your fingers on the back of your ankle just above the heel (Fig. 3.24). (iii) Point your toes down and up, and you will feel the tendon moving. Tendons are designed to withstand huge pulling forces. Try exploring other tendons in your body around the different joints. Answer Q3 Reflect on any of the physical practices you are familiar with, such as yoga, kabaddi, etc. How would it support bone and muscle health? Answer Q4 Reflect 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? Answer Q5 Turn a nature walk into a research project. (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. Answer Q6 Study 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. Answer Q1 Will 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? Answer
A group of similar cells working together to perform a specific function is called a:
A Tissue B Organ C Organ system D Organism
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