1Revise, Reflect, Refine15 questions
Q.1Meristematic 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.v
Answer:(iii) They have thin walls, dense cytoplasm and large prominent nucleus.
Q.2If a plant is unable to transport food from leaves to roots which tissue is malfunctioning? (i) Xylem (ii) Phloem (iii) Epidermis (iv) Sclerenchymav
Q.3Why 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.v
Answer:(iii) To allow quick exchange of materials across them.
Q.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 Fig. 3.21 jumps?v
Answer:In a straight-leg jump, ankles, knees and hips remain relatively stiff, so the body cannot push effectively. In a normal jump these joints bend and then extend, allowing muscles and tendons to produce a stronger upward push.
Q.5Which type of joint is involved when you bend your knees and ankles? (i) Ball and socket (ii) Hinge (iii) Pivotv
Q.6In 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.v
Answer:A: (iii) assertion true, reason false. B: (i) both true and reason explains assertion. C: (iv) assertion false, reason true. D: (iii) assertion true, reason false.
Q.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 .7. .7: Data related to the age of a teak tree, and corresponding increase in the diameter of stem and number of annual rings DBH (Diameter at Age of the teak Number of annual S. No. Breast Height) of tree (Years) rings formed tree (cm)v
Answer:The graph should show stem diameter increasing with age and annual rings increasing with age. Annual rings correspond closely to age in years. The vascular cambium, a lateral meristem located between xylem and phloem, produces secondary growth and increases girth.
Q.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: (i) Which function(s) of the tree is/are hampered by debarking? (ii) Which plant tissue would be affected by Fig. 3.22 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?v
Answer:Debarking mainly damages phloem, so transport of food from leaves to roots and protection are hampered. Further trunk damage may injure cambium and xylem. If xylem beneath the bark is severely damaged, water and mineral transport to leaves is affected. This assumes bark removal first exposes phloem before deep xylem injury.
Q.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.v
Answer:Collenchyma gives flexibility to young stems. If replaced by sclerenchyma, the stem would become more rigid and less flexible, so it may resist compression but could crack or break more easily in strong wind.
Q.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’ (A) (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 Fig. 3.23 change had an effect? (iv) What parameters should be kept the same for both types of cuttings to ensure a fair comparison?v
Answer:Type B cuttings sprouted because they had a node or bud containing meristematic tissue; type A lacked a viable bud. The measured effect is sprouting/root-shoot growth. Same variety, cutting size, soil, water, light, temperature and planting depth should be kept constant.
Q.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.v
Answer:Rohan’s statement fits simple tissues made of similar cells. Rajiv is right that complex tissues such as xylem and phloem contain different kinds of cells working together for one function, such as transport.
Q.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.v
Answer:Sclerenchyma provides the strength in coconut husk fibres because its cells have thick, lignified walls and are often dead at maturity. Living parenchyma is thin-walled and soft, so it cannot provide the same toughness.
Q.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?v
Answer:The statement is incomplete. Apical meristems are at root and shoot tips, but lateral meristems such as cambium increase girth, and intercalary meristems occur at nodes/leaf bases in some plants. Neha could ask: which tissue makes stems thicker if meristems occur only at tips?
Q.14A 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?v
Answer:The plant cell usually has the larger vacuole because a mature plant cell has a large central vacuole for storage and turgidity. This assumes a typical mature plant cell and typical animal cell of the same size.
Q.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?v
Answer:Ask whether one tissue can perform more than one role and whether complex tissues contain different cells for related functions. Parenchyma may store food, photosynthesise and heal wounds; xylem transports water and gives support; phloem transports food. These examples disprove “only one specific function”.