Tissues in Action Class 9 Question Answer Science Exploration Chapter 3

Students can use Exploration Class 9 Science Solutions Chapter 3 Tissues in Action Question Answer NCERT Solutions as a quick reference guide.

Class 9 Science Exploration Chapter 3 Question Answer

Class 9 Science Ch 3 Tissues in Action Question Answer

Tissues in Action Class 9 Questions and Answers (Exercise)

Revise, Reflect, Refine (NCERT Textbook Page No. 44 – 46)

Question 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:
(iii) They have thin walls, dense cytoplasm and large prominent nucleus.
Thin cell walls allow easy division, dense cytoplasm provides materials needed for rapid cell division and a large nucleus controls cell activities efficiently.

Question 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:
(ii) Phloem.
Phloem is the tissue that transports food prepared in the leaves to all other parts of the plant, including the roots.

Question 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:
(iii) To allow quick exchange of materials across them. A thin layer of epithelial cells allrapid diffusion of gases, nutrients and waste products between the organ and the blood.

Question 4.
You can perform these two jumps (Fig.): 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:
In the straight-leg jump, the ankles, knees and hips remain stiff. The jump height is very low and the landing is hard.
In the normal jump, the knees and ankles bend and the hips flex; the body absorbs the shock of landing smoothly. Bending at the joints stores elastic energy and allows a higher jump with a softer landing.

Question 5.
Which type of joint is involved when you bend your knees and ankles?
(i) Ball and socket
(ii) Hinge
(iii) Pivot
Answer:
(ii) Hinge joint. The knee and ankle allow movement mainly in one direction (bending and straightening), just like a door hinge.

Question 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:
(iii) Assertion is true but Reason is false. The epithelium in the lungs is a single layer of thin flat cells, which allows rapid diffusion of gases, not multiple layers of tall cells.

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:
(i) Both Assertion and Reason are true, and Reason is the correct explanation of Assertion. Mitochondria provide continuous energy (ATP) and the rich blood supply provides a constant supply of oxygen and nutrients, allowing the heart to work without rest.

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:
(iv) Assertion is false but Reason is true. Tendons connect muscles to bones (not bone to bone). Ligaments connect bone to bone. The Reason correctly describes tendons as tough connective tissue that transmits force.

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:
(iii) Assertion is true but Reason is false. A hinge joint allows movement in one plane only (like a door hinge). Sliding movement in all directions describes a ball and socket joint.

Question 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.

(i) Analyse the graph in terms of the diameter of the stem over time and share the interpretation.
(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?
Answer:
(i) The diameter of the stem increases steadily as the tree ages. The graph shows a roughly proportional increase.

(ii) The number of annual rings equals the age of the tree in years. One new ring is formed each year by the lateral meristem. So, a 30-year-old tree has 30 annual rings.
(iii) The lateral meristem (also called cambium) is responsible for the increase in girth. It is located in a ring between the xylem and phloem in the stem.

Question 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.). 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?
Answer:
(i) Debarking removes the outer protective layer. This hampers protection from water loss, mechanical injury and infection by microorganisms.
(ii) Further damage to the trunk would affect the phloem tissue, which lies just beneath the bark.
(iii) If the phloem is severely damaged, the transport of food from leaves to roots would be disrupted. The roots would starve, and the tree could die.
(iv) It is assumed that the bark consists of dead cork cells and the phloem lies just beneath it. If the damage is shallow, only the bark is affected. If the damage is deeper, the phloem and even the cambium could be destroyed, making recovery impossible.

Question 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:
The tissue responsible for this flexibility is collenchyma. Collenchyma cells have unevenly thickened comers due to pectin, which allows them to bend without breaking.
If collenchyma were replaced by sclerenchyma, the stem would become rigid and hard because sclerenchyma has thick, lignified walls. The stem would not be able to bend and would snap under strong winds.

Question 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.). 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?
Answer:
(i) Type ‘B’ cuttings had nodes (which contain intercalary meristem), while type ‘A’ cuttings lacked nodes. The meristematic tissue at the nodes allowed type ‘B’ cuttings to sprout and grow.
(ii) The presence of nodes with intercalary meristem was the key difference in type ‘B’ cuttings.
(iiI) The observation was whether sprouting and new growth occurred after a few weeks.
(iv) Type of soil, amount of water, sunlight, temperature, length of cuttings and variety of sugarcane should remain the same to ensure a fair comparison.

Question 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:
Rohan gave correct statement for simple tissues (like parenchyma, collenchyma, sclerenchyma), where all cells are of the same type. However, Rajiv also gave correct statement because complex tissues (like xylem and phloem) are made of more than one type of cell, all working together for a common function. For example, xylem has tracheids, vessels, xylem parenchyma and xylem fibres. Thus, a tissue is defined as a group of cells that work together to perform a specific function, and these cells may or may not be similar.

Question 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:

• The tissue responsible is sclerenchyma. Its cells have thick walls due to deposition of lignin, making them hard and strong. Most sclerenchyma cells are dead.
• Parenchyma could not serve this purpose because parenchyma cells have thin walls and are soft. Its cells would not be able to withstand the mechanical stress required for making tough mats.

Question 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:
Vibha’s statement is incorrect. Meristematic cells are found not only at root and shoot tips (apical meristem) but also along the sides of the stem (lateral meristem) and at the base of intemodes or above nodes (intercalary meristem). Neha can ask, “Are meristematic cells only at root and shoot tips? How do stems increase in thickness? And how does grass regrow after being cut?”

Question 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?
Answer:
(i) The plant cell will have a larger vacuole. Plant cells typically have a large central vacuole that stores water, sap and waste products, and helps maintain turgidity. Animal cells may have small vacuoles or none at all.
(ii) It is assumed that both plant and animal cells are mature, differentiated cells (not meristematic cells) because in meristematic plant cells, vacuoles are generally absent.

Question 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:
This statement is not entirely correct.
Questions asked to critically examine the statement are,
(i) Does parenchyma only store food?
No, it can also perform photosynthesis in green parts.
(ii) Does xylem only transport water?
No, it also provides mechanical support.
(iii) Does epidermis only protect?
No, it also helps in gaseous exchange through stomata and absorption through root hairs.
These examples show that many plant tissues are multifunctional.

Class 9 Science Chapter 3 Tissues in Action Question Answer (InText)

Think It Over (NCERT Textbook Page No. 28)

Question 1.
How is the study of cells and tissues significant for understanding the life processes and human welfare?
Answer:
The study of cells and tissues helps us understand how living organisms grow, develop and function. Cells are the basic unit of life and tissues are groups of cells that perform specific functions. This knowledge is important for medical science, agriculture and biotechnology. Understanding tissues helps scientists replicate and modify biological processes for human welfare.

Question 2.
How are tissues in plants and animals different, and why?
Answer:

• Plant tissues and animal tissues are different because plants and animals have different needs.
• Plants are fixed and need support to stay upright, so they have tissues with rigid cell walls such as sclerenchyma and xylem. Animals can move, so they have flexible, contractile tissues like muscles and nerves.
• Plants make their own food by photosynthesis and have specialised tissues like chlorenchyma, while animals need tissues for digestion of food obtained from external sources.

Question 3.
How is the division of labour at various levels of organisation in multicellular organisms correlated with their structure and function?
Answer:
In multicellular organisms, different groups of cells are specialised to perform different functions.

• Cells of similar type form tissues, tissues form organs, organs form organ systems and organ systems form the complete organism.
• The structure of each tissue is suited to its function. For example, muscle tissue has contractile fibres for movement, nervous tissue has long axons for transmitting signals, and xylem has hollow tubes for transporting water.
• This division of labour increases efficiency and allows the organism to carry out complex life processes.

Pause and Ponder (NCERT Textbook Page No. 33)

Question 1.
You may have noticed that fibres of coconut husk are hard and brittle, whereas the leafstalks of coriander are soft and flexible. Find out the reason.
Answer:

• Coconut husk fibres are made of sclerenchyma tissue, which has thick, lignified cell walls and mostly dead cells. This makes the fibres hard and brittle.
• Coriander leaf stalks have collenchyma tissue with unevenly thickened comers due to pectin. Collenchyma cells are living and flexible, which is why coriander stalks are soft and can bend without breaking.

Pause and Ponder (NCERT Textbook Page No. 34)

Question 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:
A thick cuticle reduces water loss by transpiration. In deserts, water is scarce, so a thick cuticle helps the plant conserve water. However, for an aquatic plant, a thick cuticle is a disadvantage because such plants need to absorb water and dissolved gases directly through their surface. A thick cuticle would block absorption of water and minerals.

Question 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:
The dead, hollow cells of xylem (tracheids and vessels) form continuous tubes from the roots to the leaves. When water evaporates from the leaves through stomata (transpiration), it creates a pulling force called the transpiration pull. This pull draws water upward through the xylem tubes. So, the living cells of the leaves create the driving force, while the dead xylem cells provide the pathway for water to travel upward against gravity.

Question 4.
What do you think will happen if there were no stomata in the epidermis of the stem or leaves?
Answer:
(i) Without stomata, the plant would not be able to exchange gases (carbon dioxide and oxygen) with the atmosphere.
(ii) Photosynthesis would be affected because the plant could not take in carbon dioxide.
(iii) Transpiration would also stop, which would disrupt the upward transport of water through xylem.
(iv) The plant would not be able to cool itself or eliminate waste gases, and would eventually die.

Question 5.
Look at the picture given below (Fig.). 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:
Classical and folk-dance poses involve different types of joints.
(i) Ball and socket joints at the shoulders and hips allow wide, circular arm and leg movements.
(ii) Hinge joints at the knees and elbows allow bending and straightening.
(iii) Pivot joints at the neck allow the head to turn from side to side.
(iv) Fixed joints in the skull are not involved in movement but protect the brain during vigorous dance.
The flexibility and range of dance movements depend on the type of joint at each body part.

Class 9 Science Chapter 3 Question Answer (Activities)

Activity 3.1:
Let us design experiments (NCERT Textbook Page No. 29)

1. Take two glass jars or couplin jars and fill them with water.
2. serve the growth of roots in both bulbs for a few days.
3. Measure the length of roots on days 1, 2 and 3.
4. 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 observe the growth of roots lengths for four more days (day 4 onwards), and record your observations in the table.

Are your observations similar to those presented in the graphical representation given here.
Answer:

• Roots in Jar A continue to grow in length over all seven days.
• Roots in Jar B grow normally up to Day 3, but stop growing after the tips are cut.
• This shows that roots grow only from their tips, which contain the actively dividing cells of the apical meristem.
• When the tips are removed, the root apical meristematic cells are lost and growth (length) of root stops.
• Our observations are expected to be similar to those presented in the graphical representation given here.

Activity 3.2:
Let us understand further (NCERT Textbook Page No. 36)

• Recall everyday experiences given in the first column of Table.
• Write your observations and questions in your notebook.
•  Compare your observations with the observations given in Table.

Answer:

• When a cut occurs, platelets help the blood to clot and stop the bleeding.
• During a skin infection, WBCs collect at the infected area, causing redness, swelling and possible pus formation.
• During exercise, muscles need more oxygen, so breathing becomes faster and blood flow increases, making the face turn red.

Activity 3.3:
Let us perform (NCERT Textbook Page No. 37)

1. Perform the actions given in Table below.
2. Record your experiences and compare them with the experiences given in Table.
3. Study their functions and identify the connective tissues (Fig.).

Answer:
(i) Touching the elbow shows a hard, rigid structure which is bone.
(if) Pressing and folding the ear shows a soft, flexible structure that returns to its shape, which is cartilage.
(iii) Feeling the forearm muscles while wiggling the fingers shows that tendons transmit movement from muscle to bone.
(iv) Moving the leg at the knee shows that ligaments stop the joint from moving beyond a safe limit.

Activity 3.4:
Let us investigate ((NCERT Textbook Page No. 39)

1. Step on a weighing scale and record your total body weight.
2. Use 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 per cent muscle, although bone mass is about 12-15 per cent for all adults.
3. Multiply your total body weight by the bone percentage and muscle percentage to estimate the weight of your bones and muscles.
4. Record the estimated bone weight and muscle weight, and compare them with your total body weight.
5. Compare your findings with those of your classmates and calculate the class average.

Discuss why do bone and muscle mass differ between individuals, and how do they contribute to the overall body weight?

Answer:

• Students weigh themselves and multiply their body weight by the bone percentage (about 12 to 15%) and muscle percentage (about 30 to 50% depending on gender) to estimate bone and muscle mass.
• Bone and muscle mass vary between individuals due to differences in age, gender, diet, exercise habits and body composition.

Activity 3.5:
Let us Observe ((NCERT Textbook Page No. 39)

Answer:

• The elbow allows only bending movement (hinge joint).
• The shoulder allows rotation in all directions (ball and socket joint).
• The knee allows bending movement (hinge joint).
• The neck allows turning side to side movement (pivot joint).
• Fingers and toes allow bending movements (hinge joints).
• The wrist allows bending movement and some rotational movement.