NCERT Solutions Class 9 Science Exploration Chapter 03 Tissues in Action

 

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.
In simple words: Meristematic cells can divide over and over because they have thin walls that stretch easily, packed cytoplasm full of working parts, and a big nucleus that guides cell division.

Exam Tip: Remember that meristematic cells lack vacuoles - this is a key distinguishing feature that allows them to pack organelles tightly for continuous division.

 

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
In simple words: Phloem is the tissue that carries sugars and food made by leaves down to the roots and other parts of the plant.

Exam Tip: Key recall point - Xylem moves water UP from roots, while Phloem moves food DOWN from leaves. This distinction is fundamental and frequently tested.

 

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.
In simple words: Thin epithelium lets substances move quickly across it. In the lungs, oxygen gets in fast. In the gut, food gets absorbed fast. This speed matters for survival.

Exam Tip: Examiners test the relationship between tissue thickness and function - thinner surfaces enable faster exchange, while thicker tissues (like skin) prioritize protection over speed.

 

Question 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:

In simple words: In a normal jump, all three joints bend and straighten together, spreading out the shock. In a straight-leg jump, the joints stay locked and the body hits the ground hard.

Exam Tip: This practical question tests understanding of joint mechanics and shock absorption - answer by comparing the range of motion at each joint and how that affects landing comfort and safety.

 

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
In simple words: The knee and ankle work like a door hinge - they open and close in one direction only, not side-to-side or round and round.

Exam Tip: Remember the three main joint types by their movement patterns - hinge joints (one plane), ball and socket joints (all directions), and pivot joints (rotation only).

 

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.

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.

Answer: A. (iii) - A is true, but R is false.
B. (i) - Both A and R are true and R is the correct explanation of A.
C. (iv) - A is false, but R is true.
D. (iii) - A is true, but R is false.
In simple words: For A - the epithelium IS good for gas exchange, but because it is THIN, not thick. For B - both facts are right and linked correctly. For C - tendons do carry muscle force, but they connect muscle to bone, not bone to bone. For D - hinge joints DO move one way, but because of bone shape that limits motion, not allows all directions.

Exam Tip: Assertion-Reason questions reward precise thinking - the reason must not only be true, but must correctly explain why the assertion is true. Watch for statements that sound right but do not support the main claim.

 

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 3.7.
Answer:

(i) Analyse the graph in terms of the diameter of the stem over time and share the interpretation.
The tree's diameter gets bigger as it gets older, but not at the same rate every year. Between year 10 and year 20, the diameter jumped a lot (from 8 cm to 24 cm), showing a time of very fast growth. After year 20, the tree still grew, but more slowly and steadily. Overall, older trees have wider trunks because they keep growing sideways throughout their lives.

(ii) What is the relation between the diameter of the teak tree to the annual rings formed?
The number of rings exactly matches the tree's age in years. A 5-year-old tree has 5 rings; a 40-year-old tree has 40 rings. Since the diameter also goes up with age, the pattern is clear: more rings means bigger diameter. Each ring was made by the side-dividing tissue (lateral meristem) in one year. So the diameter and ring count are directly connected - they both show how much the tree has grown.

(iii) Which specialised tissue is responsible for the girth of the stem and where is it located?
The Lateral Meristem is the tissue that makes the stem thicker. It sits in a ring around the stem, just under the bark. This tissue divides and makes new cells on both the inside and outside, which makes the trunk wider. Every year, it adds one new ring of wood, and we can see these rings when we cut across the trunk.
In simple words: The lateral meristem is a growing band that runs around the stem. It makes new wood and bark, which is why trees get fatter every year.

Exam Tip: Questions on tree rings and lateral meristems often ask you to link three ideas together - age, diameter, and ring count. Always explain the role of lateral meristem as the tissue that produces the annual rings.

 

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. 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?
Answer:

(i) Functions hampered by debarking

Protection is lost: The bark (made of cork cells) shields the inner tissues from physical injury, germs, water loss, and temperature swings. Stripping away the bark opens up living tissue beneath to germs and drying out.

Food transport is disrupted: Just under the bark lies the phloem. Debarking damages the phloem, cutting off food (sugars) made by leaves from reaching the roots.

Water loss increases: The waxy outer layer and cork stop the tree from losing water too fast. Without them, the tree dries out quickly.

(ii) If the trunk is further damaged beneath the bark, the Xylem would be affected. Xylem is the inner woody tissue that carries water and minerals from the roots to the leaves. If xylem breaks, water stops reaching the whole tree, and it wilts and dies.

(iii) If the phloem and xylem (both vascular tissues just beneath the bark) are severely damaged:

Water transport (by xylem) - roots cannot send water signals; leaves dry and shrivel.

Food transport (by phloem) - roots go hungry as they cannot get food from leaves; roots stop growing and cannot take in minerals.

The tree would eventually die because both transport systems have failed.

(iv) Assumptions made

We assume the phloem sits just beneath the bark and that the debarking exposed it.

We assume the xylem stayed mostly whole after the first debarking (only the outer bark and phloem were stripped).

We assume the tree has no backup routes (like grafting or new growth) to make up for the loss.

If we change the assumption that phloem is intact (i.e., phloem is also removed), then water transport would fail sooner, because roots would lose the signal to absorb water.
In simple words: Debarking hurts the tree in three ways - no protection, no food, and too much water loss. If inner tissues are also damaged, the tree runs out of water and dies.

Exam Tip: This multi-part question tests systems thinking - examiners want you to trace cause-and-effect chains and identify which tissues are critical. Always name the tissue (phloem, xylem) and explain what it does, not just say "transport stops."

 

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: Collenchyma is the tissue that gives young stems this bendy quality. It is made of living cells with uneven thickening at the corners due to pectin, which is flexible like rubber. This tissue offers both support AND flexibility to young stems, leaf stalks (petioles), and tendrils - letting them bend without snapping when monsoon winds blow hard.

Impact if collenchyma were replaced by sclerenchyma:

Sclerenchyma cells have thick, hardened (lignified) cell walls - they are dead cells that give hardness and strength but NO flexibility.

If the mango sapling's stem had sclerenchyma instead of collenchyma, the stem would turn stiff and brittle.

When monsoon winds hit, instead of bending, the stem would snap and break - badly hurting the plant.

This would also stop the plant from doing growth movements (like growing toward light), since rigid sclerenchyma cannot bend.

The plant's chances of surviving windy weather would drop sharply.
In simple words: Collenchyma lets the young stem flex and bounce back. Sclerenchyma would make it hard and snap. Young plants need bendiness to live through storms.

Exam Tip: Comparison questions like this one test whether you understand the link between tissue structure and function. Always name the specific feature (pectin makes it flexible; lignin makes it stiff) and predict the outcome logically.

 

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. 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?
Answer:

(i) Type B cuttings could grow because they held nodes with intercalary meristem - the actively dividing growing tissue found at nodes on the stem. This tissue let the cutting regrow new shoots and roots. Type A cuttings lacked this growing tissue (they likely came from the space between nodes only) and so could not regrow or sprout.

(ii) Type B cuttings included the nodes of the sugarcane stem - the spots where intercalary meristematic cells live. These meristematic cells keep the power to divide and change into new plant tissues. Type A cuttings most likely came from the spaces between nodes - which hold only finished tissues (no meristematic cells) - so they could not regrow.

(iii) The main observation was whether the cuttings sprouted new shoots and roots or not - shown by visible growth (new shoots/leaves showing up) after a few weeks. Also, measuring how long the new growth got over time would show the difference in numbers. The fact that Type B sprouted while Type A did not was the key finding.

(iv) Parameters to keep the same for fair comparison:

Length of cuttings - both types should be the same length.

Age and health of the parent plant - cuttings from the same plant or from plants of the same age.

Growing conditions - same soil type, amount of water, sunlight, and temperature for both types.

Time of planting - both planted on the same date.

Orientation of cutting - both planted in the same direction (upright).

Number of cuttings - same count of each type to let you compare numbers properly.
In simple words: Type B works because it has nodes with growing cells. Type A does not work because it has only dead tissue. To test fairly, keep everything else the same - soil, light, water, and time.

Exam Tip: Experimental design questions reward you for identifying the one variable being tested (presence of nodes) and listing all the controls (factors kept constant). This shows you understand the scientific method.

 

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: Both Rohan and Rajiv are partly correct. Here is the full picture:

Rohan's statement is the basic meaning of a tissue and fits well for simple finished tissues like parenchyma, collenchyma, and sclerenchyma - where all cells are the same kind and do the same work (for example, all parenchyma cells store food and have thin walls).

Rajiv's argument is right for complex finished tissues like xylem and phloem:

In complex tissues, different cell types team up to do a shared big job (carrying things), even though each type does its own special role. So the tissue as a whole has one main job, but the single cells inside are NOT all the same in shape or special work. This is why Rajiv's update to Rohan's meaning is useful and correct.
In simple words: Simple tissues have all the same cells doing the same thing. Complex tissues have many types of cells, each with a different job, but they all work together for one main purpose.

Exam Tip: This discussion question tests your ability to reconcile conflicting ideas. Show you understand the threshold where Rohan's definition breaks down (at complex tissues) and why Rajiv's refinement matters for complete accuracy.

 

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: Sclerenchyma tissue has the structural features needed to give this kind of strength. Coconut husk fibres are made from sclerenchyma.

The structural features that make sclerenchyma fit for giving strength are:

Cells have thick, hardened (lignified) cell walls - lignin is an extremely strong material that makes cell walls stiff and long-lasting.

Most sclerenchyma cells are dead when fully grown - they no longer need living resources and are basically hollow pipes of strong lignified stuff.

The cells are long and thread-like in form, lined up in bundles, giving pull strength and resistance to ripping.

This is what gives coconut husk, jute, and walnut shells their hard and tough feel.

Parenchyma does not work the same way because:

Parenchyma cells have thin cell walls (not hardened) - they are soft and bendy, giving NO hard support or strength.

Parenchyma cells are alive and working - they would rot over time if used as a structural stuff, making them bad for tough, lasting things like mats.

They have big water sacs and air gaps - making them soft, easy to press, and not fit for thread-like, tough jobs.
In simple words: Sclerenchyma is dead, hard, and long - perfect for tough fibres. Parenchyma is alive, soft, and droops - it would rot and fall apart in a mat.

Exam Tip: Structure-function questions require you to name the specific chemical (lignin) and physical properties (thick walls, dead cells) and link them directly to an observed use (tough mats, ropes).

 

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 not complete and is partly off base. The correct picture: Plants have three kinds of meristematic tissue in different spots:

Questions Neha can ask Vibha to help her think it through:

"If meristems are only at root and shoot tips, then how does a tree trunk get fatter (girth) over the years?"

"When we mow a lawn or a cow eats grass, how does the grass regrow if the tip is gone? Which meristem does that?"

"When the tip of a plant is cut off and new branches show up from the nodes below, which meristem makes that happen?"

These questions would push Vibha to find lateral and intercalary meristems by herself.
In simple words: Meristems are not just at the tips. They are also around the sides (making thick trunks) and at the base of leaf spaces (making grass regrow after cutting).

Exam Tip: Misconception-correction questions test depth of learning. Show the three meristem types, their locations, and cite practical examples (lawn mowing, tree aging) to fully overturn the incomplete claim.

 

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 bigger water sac. Reasons:

Grown plant cells typically hold one big central water sac that can fill up to 80 - 90 percent of the cell space. It is wrapped by a selective filter membrane named the tonoplast.

The plant cell's water sac holds water, minerals, sugars, and waste. It also keeps turgor push - the inside push that keeps the plant cell stiff and the plant standing up.

Animal cells, by contrast, may have small, short-lived water sacs (if any) for moving or storing stuff, but these are much tinier and not as steady or lasting as in plant cells.

Since both cells are the same size, the plant cell's big water sac leaves less room for liquid (cytoplasm) and other parts, while the animal cell would have more liquid and parts by comparison to its size.

(ii) Assumptions made:

We assume the plant cell is a grown-up plant cell (like from a leaf or stem), not a young growing cell (which has no water sac).

We assume the animal cell is a normal body cell (not a special cell like a fat cell/adipocyte, which saves big fat droplets).

If the guess shifts (like the plant cell is a young growing cell), then neither cell would have a big water sac.
In simple words: Plant cells have one huge water sac to stay firm. Animal cells have many small water sacs or none. If the plant cell is young, it has no big water sac yet.

Exam Tip: Comparative cell structure questions expect you to link form to function - the large vacuole is not just a feature, but a necessity for plant turgor and rigidity. Always state your assumptions because they determine whether your answer holds true.

 

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: The claim "Each plant tissue performs only one specific function" is not fully right and needs careful testing. To check this claim, we should pose questions like:

1. Does parenchyma only save food or does it do other jobs too?

2. Does epidermis only shield or does it help in other tasks?

3. Do complex tissues like xylem do only one job?

Parenchyma is the top example to argue against this claim. Although parenchyma mainly keeps food, it also does photosynthesis in the green parts of the plant. In water plants, special parenchyma makes air pockets which help them stay up. So parenchyma clearly does more than one job.

Epidermis is one more good example. It forms the outer shield of the plant body and guards against hurt and germs. But it also has pores in leaves that let air pass and let water escape. In roots, outer layer cells make root hair which suck up water and minerals from dirt. So epidermis does shielding, air swap, and water loss - clearly more than one job.

Xylem is a complex finished tissue which not only carries water and minerals from roots to other parts of the plant but also gives hard support and holds up the plant. Therefore, the claim is off. Multiple plant tissues do more than one special job, and the instances of parenchyma, epidermis, and xylem clearly show this.
In simple words: Most plant tissues do more than one job. Parenchyma makes food AND stores it. Skin protects AND lets air in. The claim is wrong because real life is more complex.

Exam Tip: Critical thinking questions reward detailed, multi-tissue examples over vague statements. Pick two or three tissues, name their multiple functions clearly, and explain why the blanket claim fails for each one.

 

Very Short Answer Type Questions

 

One Word or One Sentence Answers

 

Question 1. What is a tissue?
Answer: A tissue is a group of cells that are alike in form and function that work as one unit to do a job.

Exam Tip: Tissue definition questions require you to name three key elements - cells, similarity (structure and function), and shared purpose.

 

Question 2. Name the three types of meristematic tissues found in plants.
Answer: Apical meristem, Lateral meristem, and Intercalary meristem.

Exam Tip: Memorize these three names and their basic locations (tip, side, base of internodes) for quick recall.

 

Question 3. Where is the apical meristem located?
Answer: At the tips of roots and shoots of a plant.

Exam Tip: "Apical" = tip. Apical meristem is at the top and bottom tips of every plant.

 

Question 4. Which meristematic tissue is responsible for the increase in girth (thickness) of a stem?
Answer: Lateral meristem.

Exam Tip: "Lateral" = side. Side meristem makes the stem fatter.

 

Question 5. What is differentiation?
Answer: Differentiation is the process by which growing cells lose the power to divide and become special to make finished tissues.

Exam Tip: Differentiation turns growing cells into permanent tissues - a one-way change.

 

Question 6. Name the only living component of xylem.
Answer: Xylem parenchyma.

Exam Tip: Vessels and tracheids are dead; only parenchyma cells stay alive in xylem.

 

Question 7. Which tissue transports food from leaves to other parts of the plant?
Answer: Phloem.

Exam Tip: Phloem = food transport. Xylem = water transport. Keep them straight.

 

Question 8. What is the waxy layer present on the outer surface of the epidermis called?
Answer: Cuticle.

Exam Tip: The cuticle is a waxy, waterproof coating that stops water loss.

 

Question 9. Name the pores present in the epidermis of leaves that help in gaseous exchange.
Answer: Stomata.

Exam Tip: Stomata are tiny pores for gas swap and water loss in leaves.

 

Question 10. What are the cells of nervous tissue called?
Answer: Neurons (nerve cells).

Exam Tip: Neurons are the basic units of the nerve system.

 

Question 11. Which type of muscle tissue is found only in the heart?
Answer: Cardiac muscle.

Exam Tip: Cardiac muscle beats without tiring - it is made for non-stop work.

 

Question 12. What connects muscle to bone?
Answer: Tendon.

Exam Tip: Tendon = muscle to bone. Ligament = bone to bone. Do not mix them up.

 

Question 13. What type of joint is present at the shoulder?
Answer: Ball and socket joint.

Exam Tip: Ball and socket joints (shoulder, hip) move in all directions. Hinge joints (knee, elbow) move one way only.

 

Question 14. Name the flexible column of small bones that forms the backbone.
Answer: Vertebral column (spine), made up of vertebrae.

Exam Tip: The spine is 33 bones (vertebrae) stacked with shock-soaking discs.

 

Question 15. What is the full form of RBC and how long does an RBC live?
Answer: RBC stands for Red Blood Cell; it lives for about 4 months and is swapped out regularly.

Exam Tip: Red blood cells are made in the bone marrow and live about 120 days.

 

Short Answer Type Questions

 

Answers in approximately 30 words

 

Question 1. Why do plant cells have a cell wall but animal cells do not?
Answer: Plants stay in one spot and need stiffness and strength to stand upright, so their cells have a cell wall. Animals move around, so their cells have no stiff wall, giving them the flex they need to get around.

Exam Tip: Cell wall presence is about lifestyle - plants need support; animals need mobility.

 

Question 2. What are annual growth rings and what information do they provide?
Answer: Annual growth rings are ring-like marks on a tree trunk cross-section, made by the side-dividing tissue. By counting these rings, you can guess the tree's age and learn what weather hit it during growth years.

Exam Tip: Each ring = one year. Thick rings = good growth year. Thin rings = hard year.

 

Question 3. Why do meristematic cells lack vacuoles?
Answer: Growing cells divide all the time and quickly. Water sacs store water and liquid, and their space would eat up room for hard work. Without water sacs, cells stay tiny and packed tight, letting them divide well and fast.

Exam Tip: No vacuoles = tight packing = rapid division. This is a key feature that sets growing cells apart from ripe cells.

 

Question 4. What are sieve tubes and companion cells? What is the function of companion cells?
Answer: Sieve tubes are long, pipe-like cells in phloem joined end-to-end by drilled walls; they move food. Buddy cells are special food-storing cells that help sieve tubes and watch the load and unload of sugars in them.

Exam Tip: Sieve tubes carry the goods (food). Companion cells do the work (monitoring and directing).

 

Question 5. Distinguish between voluntary and involuntary movements with one example each.
Answer: Voluntary moves are under your brain's say (like writing, running) and happen with bone muscles. Involuntary moves go on by themselves without brain say (like heartbeat, food move in gut) and come from smooth and heart muscles.

Exam Tip: Voluntary = you choose it = skeleton muscle. Involuntary = it just happens = smooth and cardiac muscle.

 

Question 6. What is the role of cartilage in the human body?
Answer: Cartilage has a soft, jelly-like base that gives flex and soaks up bumps at bone ends. It sits at joints, nose, ears, and between spine bones, keeping bones from rubbing together.

Exam Tip: Cartilage = flexible, shock-absorbing. Bone = hard, rigid support. Together they make movement smooth and safe.

 

Question 7. What is the intercalary meristem, and how does it help a lawn regrow after mowing?
Answer: Intercalary meristem sits at the base of leaf spaces (nodes of the stem). When grass is mowed, the shoot tops are cut but the intercalary meristem at the nodes stays, letting the grass come back and grow.

Exam Tip: Intercalary meristem = why grass regrows after mowing. The tip gets cut but the base stays alive.

 

Question 8. What is totipotency? Who first demonstrated it, and in which plant?
Answer: Totipotency is the skill of a single ripe plant cell to split, go back to a young state, and regrow into a whole new plant. F. C. Steward first showed this in 1958 using food-carrying cells of carrot.

Exam Tip: Totipotency = one cell can make a whole plant. This is a big part of plant biotech and tissue culture.

 

Question 1. What is the difference between meristematic tissue and permanent tissue in plants?
Answer: Meristematic tissue is made of cells that divide actively. These cells are tiny, have thin walls, packed cytoplasm, a big clear nucleus, and no vacuoles. They keep dividing to bring new cells to the plant. Permanent tissue forms after meristematic cells stop dividing and change - a change where they become skilled to do certain jobs like holding up, guarding, keeping things, or moving water and food. To keep it simple, meristematic tissue makes the plant grow bigger, while permanent tissue does all the work once that region stops growing.
In simple words: Meristematic tissue makes the plant grow. Permanent tissue does the plant's jobs like support and food movement.

Exam Tip: Always describe the cell features (thin walls, no vacuoles) for meristematic tissue and mention the specialization process for permanent tissue to score full marks.

 

Question 2. Why do roots of a plant stop growing if the root tip is cut off?
Answer: Roots only grow from their tips. Inside the root tip is the apical meristem - an area where cells divide very fast. When you cut off the root tip, you take away these dividing cells. Since no other part of the root can divide in the same way, the root cannot grow anymore. This idea was shown in Activity 3.1 using onion bulbs in jars. The roots in Jar B (where the tips were removed on Day 3) did not grow, but the roots in Jar A kept growing as normal.
In simple words: The root tip has the cells that make roots grow. Once the tip is gone, no other part can grow roots.

Exam Tip: Reference the practical experiment (Activity 3.1 with onion bulbs) to show you understand how growth happens in plant roots.

 

Question 3. What is the role of xylem and phloem in plants? Are they living or dead tissues?
Answer: Xylem moves water and minerals up from the roots to the rest of the plant. It also makes the plant strong and stiff. It has tracheids, vessels, xylem parenchyma, and xylem fibres. Only the xylem parenchyma stays alive; most parts are dead. Phloem carries food (made from sugar in leaves) to all other plant parts. It has sieve tubes, buddy cells, phloem parenchyma, and phloem fibres. Unlike xylem, most of phloem is living. Together, xylem and phloem are known as complex permanent tissues or vascular tissues.
In simple words: Xylem moves water up. Phloem moves food down. Xylem is mostly dead but phloem is mostly alive.

Exam Tip: When asked about living/dead status, always specify which parts stay alive in each tissue - this distinction is frequently tested.

 

Question 4. What are the four types of animal tissues?
Answer: The four animal tissues are: 1. Epithelial tissue - covers the outside of the body (skin) and lines the inside of organs. It keeps out harm, lets things in through absorption, releases substances, and senses changes. 2. Connective tissue - joins and holds other tissues and organs in place. It takes the form of blood, bone, cartilage, tendons, and ligaments. 3. Muscular tissue - makes movement happen. It comes in three kinds: skeletal (you control it), smooth (your body runs it), and heart muscle. 4. Nervous tissue - builds the brain, spinal cord, and nerves. It has neurons that gather signals and send them out as electrical messages.
In simple words: Epithelial covers the body. Connective joins parts. Muscular makes things move. Nervous sends messages.

Exam Tip: When listing all four tissues, always include one function or example for each type to ensure complete marks.

 

Question 5. What is the difference between voluntary and involuntary muscles? Which tissue is the heart made of?
Answer: Voluntary muscles (skeletal muscles) work when you choose to move them - like when you run or hold a pen. They are long and tube-shaped with many nuclei and have stripes (light and dark bands). Involuntary muscles (smooth muscles) work on their own without you deciding, such as in your stomach and bowel. Their cells look like spindles with just one nucleus. The heart uses cardiac muscle, which is special - it works without you thinking about it and never gets tired across your whole life, yet its cells are round, branch out, and have soft stripes with one nucleus each.
In simple words: Voluntary muscles are ones you move on purpose. Involuntary muscles work by themselves. Heart muscle is special because it never stops and never gets tired.

Exam Tip: Use specific examples (running for voluntary; stomach for involuntary) and emphasize the heart's unique ability to work non-stop without fatigue.

 

Question 6. What is the musculoskeletal system and why is it important?
Answer: The musculoskeletal system brings together bones, muscles, joints, cartilage, tendons, and ligaments. It lets us stand tall, move around, hold good posture, and guard soft organs inside. Muscles pull bones by way of tendons to make joints bend and move. The grown-up human skeleton makes up roughly 12 - 15% of how much the body weighs. The brain and nerves run this system - when the brain tells muscles to squeeze, that squeeze goes through tendons to bones, which then move.
In simple words: The musculoskeletal system has bones and muscles that let you stand and move. Nerves tell muscles when to pull.

Exam Tip: Mention the percentage of body weight (12 - 15%) and explain the nerve-muscle-bone chain to show complete understanding.

 

Question 7. What are the different types of joints in the human body?
Answer: This chapter names four joint types: 1. Ball and socket joint (shoulder, hip) - lets you move in every direction - front, back, side, and round. 2. Hinge joint (elbow, knee) - lets movement happen only one way, like a door swinging - bending and opening. 3. Pivot joint (where neck meets spine) - allows you to spin, like turning your head left and right. 4. Fixed joints (skull bones) - bones lock together and cannot shift, keeping the brain safe inside.
In simple words: Ball joints move any way. Hinge joints move one way. Pivot joints spin. Fixed joints don't move at all.

Exam Tip: For each joint type, give a clear example and describe its range of motion - examiners expect both facts and real-body applications.

 

Question 8. What is differentiation in plants? How does meristematic tissue become permanent tissue?
Answer: Differentiation is the shift where meristematic cells cannot divide anymore and shift in shape to turn into skilled (permanent) tissues. As meristematic tissue divides and divides, some new cells stay meristematic, while others pick up certain jobs - like holding the plant up, saving nutrients, or moving water. These cells grow thick walls, get longer or even pass away (like in sclerenchyma), all to fit their exact role. This move from meristematic to permanent tissue by way of differentiation is what shapes the full-grown plant frame.
In simple words: Cells that divide stop dividing and change shape to do special jobs. This change builds the whole plant.

Exam Tip: Explain both the structural changes (thick walls, elongation) and the functional specialization to show that differentiation involves both form and purpose.

 

Question 9. Why can plants regrow after mowing or pruning, but wounds in animals often don't regenerate?
Answer: Plants can grow back after cutting because they have intercalary meristem at the joints of stems - places where cells divide and stay active even when the top is removed. Grass grows back after mowing since its intercalary meristem at the joints gets left alone. Animals, by contrast, hold far fewer cells that can build themselves back. Most mature animal cells are locked into their roles and cannot split and regrow hard tissues. Yet, as noted in the "Ready to Go Beyond" part, stem cells in bone marrow can split and make new blood cells, and this is used in bone marrow moves to treat sicknesses like blood cancer.
In simple words: Plants have dividing cells all over their stems so they regrow. Animals have fewer cells that can divide, so they can't regrow most tissues.

Exam Tip: Contrast intercalary meristem in plants with the limited regenerative capacity in animals, and mention bone marrow transplants as a real-world example of how some animal tissues can regenerate.