Correct option: (B).

A tissue is a group of cells, generally similar in structure, that work together to perform a particular function. Formation of tissues brings about division of labour in multicellular organisms.

Correct option: (B).

Cells form tissues, more than one type of tissue may form an organ, organs work together in organ systems, and organ systems collectively form an organism.

Correct option: (B) Meristematic tissue.

Meristematic tissues contain actively dividing cells. Their continued division adds new cells to the growing plant body.

Correct option: (A).

Apical meristems occur at root and shoot tips and contain continuously dividing cells responsible for elongation.

Correct option: (C).

Lateral meristem consists of dividing cells arranged along the circumference of the stem. Their activity produces cells inward and outward, increasing stem girth.

Correct option: (B).

Intercalary meristem occurs near nodes or at the base of internodes in plants such as grasses, allowing regrowth after mowing or grazing.

Correct option: (B).

Meristematic cells are small, thin-walled, tightly packed and possess dense cytoplasm with a large prominent nucleus. Vacuoles are generally absent.

Correct option: (B) Differentiation.

During differentiation, newly produced meristematic cells change in structure and function and become specialised permanent tissues.

Correct option: (A) Cuticle.

The epidermal cells may be covered by a waxy cutin layer called the cuticle. It reduces water loss and also provides protection.

Correct option: (B).

Root hairs are extensions of epidermal cells and increase the surface area available for absorption of water and minerals from soil.

Correct option: (B) Parenchyma.

Parenchyma consists of living thin-walled cells with intercellular spaces. It commonly stores food and may also perform other specialised functions.

Correct option: (A).

Collenchyma consists of living cells with unevenly thickened corners. Pectin deposition provides both mechanical support and flexibility.

Correct option: (B).

Sclerenchyma cells develop thick lignified walls, making them hard and strong. Coconut husk is a common example.

Correct option: (B) Xylem.

Xylem transports water and dissolved minerals from roots to other parts of the plant and also contributes to mechanical strength.

Correct option: (D) Xylem parenchyma.

Tracheids, vessels and xylem fibres are primarily sclerenchymatous, whereas xylem parenchyma is living.

Correct option: (A).

Sieve tubes are major conducting components of phloem and transport food from leaves to other parts of the plant.

Correct option: (B).

Companion cells regulate cellular functions associated with sieve tubes and help monitor loading and unloading of sugars.

Correct option: (C).

Xylem and phloem together form the conducting or vascular tissue system of plants.

Correct option: (B).

A single layer of thin flat epithelial cells provides a short distance for diffusion and is suitable for exchange in places such as lungs and blood vessels.

Correct option: (B) Matrix.

Blood has a fluid matrix, whereas bone has a hard rigid matrix containing calcium and phosphorus compounds.

Correct option: (B) Platelets.

Platelets participate in clotting at an injury site and therefore help limit blood loss.

Correct option: (B).

Tendons are strong connective tissues that attach muscle to bone and transmit the pulling force generated by muscle contraction.

Correct option: (A).

Ligaments connect bones to other bones, stabilise joints and limit excessive movement that could lead to dislocation.

Correct option: (C) Skeletal muscle.

Skeletal muscle fibres are long, cylindrical, unbranched, multinucleate and show alternating light and dark bands.

Correct option: (B).

Smooth muscles are involuntary, spindle-shaped and non-striated and carry out slow continuous movements in organs such as the intestine.

Correct option: (B) Dendrite.

Dendrites receive signals from other neurons. The axon carries a message away from the cell body toward axon terminals.

Correct option: (C).

The rounded head of the upper arm bone fits into a hollow in the shoulder region, allowing movement in several directions.

Correct option: (A).

The skull connects with the backbone through a pivot joint that allows rotation of the head from side to side.

Correct option: (B).

Totipotent plant cells can regain division ability, divide, differentiate and ultimately regenerate a complete plant under suitable culture conditions.

Correct option: (B).

Collenchyma provides both mechanical support and flexibility. Its living cells possess unevenly thickened corners containing pectin, allowing plant parts to bend without breaking.

Different groups of cells become specialised for different tasks. Therefore several biological processes can be performed efficiently and simultaneously. This division of labour enables multicellular organisms to perform complex life processes.

Plants are generally fixed in one place and require rigid supporting structures, while animals usually require flexibility for locomotion. Their modes of nutrition, transport and growth are also different, so their tissues become specialised differently.

Apical meristem occurs at root and shoot tips and increases length. Lateral meristem occurs along the circumference of stems and contributes to increase in girth.

Meristematic cells are specialised for rapid and repeated division. Their internal space is dominated by dense active cytoplasm and a prominent nucleus rather than a large storage vacuole. Large vacuoles would occupy space that is useful for active cellular machinery.

Simple permanent tissues are composed primarily of one type of cell; examples include parenchyma, collenchyma and sclerenchyma. Complex permanent tissues contain more than one type of cell working together; xylem and phloem are examples.

A thick cuticle reduces water loss from exposed plant surfaces. In a dry habitat, conserving water is especially important, so increased cuticle thickness helps limit excessive loss through transpiration.

• Parenchyma cells are living and thin-walled; most sclerenchyma cells are dead and possess thick lignified walls.
• Parenchyma commonly performs storage and sometimes photosynthesis, while sclerenchyma provides hard mechanical strength.

Each consists of several structurally different cell types that work together. Xylem includes tracheids, vessels, fibres and parenchyma, while phloem includes sieve tubes, companion cells, parenchyma and fibres.

• They permit gaseous exchange.
• They allow transpiration, which contributes to transpiration pull and water movement through xylem.

A tendon connects muscle to bone and transmits muscular force. A ligament connects bone to bone, stabilises a joint and limits excessive movement.

Cartilage has a softer and more flexible matrix than bone. It cushions the ends of bones, absorbs shock and helps movements occur with reduced mechanical stress.

• Skeletal muscle is generally voluntary and striated; smooth muscle is involuntary and non-striated.
• Skeletal fibres are long, cylindrical and multinucleate; smooth muscle cells are spindle-shaped and usually possess one nucleus.

Dendrites receive signals from other neurons or cells. The axon carries the message away from the cell body toward axon terminals, which transmit it to other cells.

Cartilage discs act as cushions between adjacent vertebrae and provide flexibility. They help the backbone bend and twist without damaging the spinal cord.

Dedifferentiation is the process by which specialised mature plant cells regain the ability to divide and form an undifferentiated mass of cells. These cells may later redifferentiate into specialised tissues under suitable conditions.

1. Grow roots from two similar onion bulbs placed over water and measure their root lengths for a few days.
2. Cut approximately 1 cm from the root tips of one set while leaving the other intact.
3. The intact roots continue elongating while roots with removed tips stop or show greatly reduced elongation.

The observation shows that actively dividing cells responsible for lengthwise growth occur at root tips—the apical meristem.

Lateral meristem adds new cells in a concentric manner, producing increase in stem diameter. In woody trunks this growth may be visible as annual rings. Wider and narrower rings can reflect relatively favourable or unfavourable growth conditions during particular years. The number of rings can therefore help estimate tree age.

• They possess thin cell walls.
• They contain dense cytoplasm and a large prominent nucleus.
• They are tightly packed, with little or no intercellular space, and large vacuoles are generally absent.

These characteristics support rapid metabolic activity and repeated division.

• The tightly packed epidermal layer provides protection from mechanical injury and invading organisms.
• The cuticle reduces excessive water loss.
• Specialised epidermal structures such as root hairs aid absorption, while stomata permit gaseous exchange and transpiration.

• Parenchyma: living, thin-walled cells with spaces; suited for storage and sometimes photosynthesis.
• Collenchyma: living cells with unevenly thickened corners; provide support with flexibility.
• Sclerenchyma: mostly dead cells with thick lignified walls; provide hardness and strength.

Large air spaces lower the effective density of plant tissues and increase buoyancy. This helps aquatic plants remain afloat. The adaptation shows how a simple permanent tissue can become specialised for a particular environment.

Xylem consists of:

• Tracheids
• Vessels
• Xylem fibres
• Xylem parenchyma

Tracheids and vessels are tubular and thick-walled. Xylem fibres provide strength. Xylem parenchyma is the living component identified in the chapter.

• Sieve tubes conduct food from leaves to other parts of the plant.
• Companion cells regulate sieve-tube cellular functions and help monitor loading and unloading of sugars.
• Phloem parenchyma stores food and substances such as resin, tannins and latex.

• Exchange: one thin layer of flat cells enables rapid diffusion.
• Protection: multiple tightly packed layers resist friction, injury and microbes.
• Absorption: a single layer of tall pillar-like cells, often with surface specialisations, aids efficient uptake.

• RBCs contain haemoglobin and carry oxygen; increased oxygen demand during exercise requires increased circulation.
• WBCs accumulate at infection sites and participate in defence, contributing to inflammation and pus formation.
• Platelets assist clot formation when a blood vessel is injured.

• Bone: hard matrix; strength, support and protection.
• Cartilage: softer flexible matrix; cushioning and flexibility.
• Tendon: connects muscle to bone and transmits pulling force.
• Ligament: connects bone to bone and stabilises joints.

The nervous system detects and coordinates the body’s requirements. During exercise, signals from the brain regulate skeletal muscles and also increase the rate of heart activity. Muscle tissues then produce the required movements. Thus muscles act in response to nervous instructions rather than functioning independently.

• Dendrites provide receiving surfaces for incoming signals.
• The cell body contains the nucleus and coordinates cell activities.
• A long axon carries signals over a distance, while axon terminals pass the message to other cells.

A skeletal muscle contracts and generates a pulling force. A tendon transmits this force from muscle to bone. The bone acts as a rigid support, and movement occurs around a joint. Ligaments help stabilise the joint while cartilage cushions bone ends.

• Ball-and-socket: movement in several directions including rotation; shoulder.
• Hinge: mainly bending and straightening in one direction; elbow or knee.
• Pivot: rotational movement around an axis; joint between skull and backbone permitting head turning.

• Bones form a strong framework and protect internal organs.
• Cartilage discs between vertebrae provide cushioning and flexibility.
• Flexible cartilage connecting ribs permits the rib cage to expand and contract during breathing.

Steward cultured cells from carrot phloem in a suitable nutrient medium containing sugars and hormones. Mature cells first regained division capacity, produced an undifferentiated mass, and later redifferentiated into roots, shoots and an entire plant.

The experiment demonstrated totipotency of certain mature plant cells.

Plant growth occurs mainly where actively dividing meristematic cells are located rather than equally throughout the body.

• Apical meristem: root and shoot tips; elongation.
• Lateral meristem: stem circumference; increase in diameter or girth.
• Intercalary meristem: near nodes or internodes of certain plants; permits regrowth after cutting or grazing.

Together they account for lengthwise growth, thickening and regeneration.

1. Use similar onion bulbs and identical jars containing equal amounts of water.
2. Allow roots to grow and record initial lengths.
3. Remove the same length of root tip from the experimental group; leave controls intact.
4. Measure root length daily for several days.

Independent variable: presence or removal of root tips.
Dependent variable: increase in root length.
Controlled factors: bulb size, water, light, temperature and observation period.

Reduced growth after tip removal supports the location of apical meristem at root tips.

• Epidermis: tightly packed outer protective covering.
• Cuticle: waxy layer that reduces water loss and offers additional protection.
• Root hairs: increase surface area for absorption of water and minerals.
• Stomata: permit gaseous exchange and transpiration.

Thus the dermal system is not merely a barrier; it also supports controlled interaction between the plant and its environment.

Water evaporates from leaves through stomata during transpiration. This loss contributes to a pulling force in the water column of xylem, known in the chapter as transpiration pull.

Xylem vessels and tracheids form tubular conducting pathways even though the mature conducting elements are largely non-living. Living leaf tissues continually lose water, sustaining the pull that helps move water upward from roots.

• Thin flat single-layered epithelium allows rapid exchange.
• Multilayered tightly packed epithelium provides protection.
• Specialised cuboidal/columnar glandular cells produce secretions.
• Special receptor cells with hair-like structures support sensory functions.
• Tall pillar-like absorbing cells form the lining of the small intestine.

The examples show that epithelial structure changes according to the job performed.

Connective tissue is defined by its role in connecting, transporting or supporting body structures, not simply by hardness.

• Blood has a fluid matrix and transports gases, nutrients, hormones and other materials.
• Bone has a rigid mineralised matrix and provides support and protection.
• The major difference in consistency arises from the nature of their matrix.
• Both therefore fulfil connective/supportive roles despite very different physical forms.

• Injury: platelets help form a clot and limit blood loss.
• Infection: WBCs accumulate in affected tissues and participate in defence, contributing to inflammation and pus.
• Exercise: muscles require additional oxygen, so breathing and blood flow increase.
• RBC haemoglobin helps transport the oxygen required by working tissues.

• Skeletal muscles contract to generate force.
• Tendons connect muscle to bone and transmit the force.
• Bones act as rigid structures that move around joints.
• Ligaments stabilise bone-to-bone connections while cartilage cushions the ends of bones.

Movement therefore results from coordinated action rather than any single tissue functioning alone.

Skeletal muscle consists of long striated multinucleate fibres attached to bones and supports voluntary forceful movements.

Smooth muscle has spindle-shaped non-striated cells and supports slow involuntary movements in organs such as the intestine.

Cardiac muscle consists of branched cylindrical fibres with faint striations and works rhythmically throughout life in the heart.

1. Nervous tissue receives and processes information.
2. The brain coordinates a response and sends instructions through neurons.
3. Skeletal muscles respond by contracting.
4. Tendons transmit muscular force to bones, which move around joints under ligamentous support.

Thus nervous tissue provides control while muscles, connective tissues and bones execute the movement.

• Ball-and-socket: rounded bone end fits in hollow; movement in many directions and rotation.
• Hinge: movement mainly in one plane, like a door hinge.
• Pivot: permits rotational movement around an axis.
• Fixed: bones are firmly joined and no movement occurs, providing protection.

• The vertebral column consists of vertebrae forming a flexible support that helps the body remain upright.
• Cartilage discs between vertebrae provide cushioning and permit bending.
• The rib cage consists of 12 pairs of ribs and protects the heart and lungs.
• Flexible cartilage attachments allow rib movement during breathing.

In Steward’s experiment, mature carrot phloem cells were placed under suitable culture conditions.

• They first dedifferentiated, regaining their ability to divide.
• The resulting unspecialised cells proliferated.
• They later redifferentiated into specialised root and shoot tissues.
• The ability of one suitable plant cell to regenerate a complete plant demonstrates totipotency.

Removing the shoot tip removes much of the apical meristem responsible for elongation, so lengthwise growth at that point decreases.

Meristematic regions associated with nodes remain intact. These can produce new branches, explaining the increasingly bushy appearance. The observation demonstrates that meristematic tissue is not restricted to one single location in the plant.

Plant X probably retains functioning intercalary meristem near its nodes or at the base of internodes. These meristematic cells continue to divide after cutting.

If Plant Y lacks such an active region at or below the cut, removal of its growth region would strongly reduce regeneration.

The plant could still grow in length through apical meristems and may regenerate certain regions through intercalary meristems. However, increase in stem diameter would be strongly restricted because lateral meristem is responsible for adding cells around the stem circumference.

No. Ring number can indicate the number of growth periods, whereas ring width varies with growth conditions. A younger tree experiencing more favourable conditions may develop wider rings and a larger diameter than an older tree that grew slowly under less favourable conditions.

Meristematic cells are characterised by dense cytoplasm, a prominent nucleus and absence of large vacuoles because they are specialised for rapid division.

A large vacuole would occupy much of the cell’s internal space and would be inconsistent with the high proportion of active cytoplasm associated with repeated division. Rapid meristematic activity would therefore likely be impaired.

• Water loss from exposed surfaces would increase.
• The epidermal surface would have reduced protection against some forms of mechanical injury and environmental stress.

The effect would be especially serious in a dry habitat because water conservation is critical.

A desert plant benefits from restriction of water loss. A submerged leaf is surrounded by water and does not face the same dehydration problem.

An excessively thick external barrier could interfere with effective exchange between the leaf surface and the surrounding aquatic environment without providing the same water-conservation advantage.

Xylem can only transport water that first enters the plant. Root hairs greatly increase the absorbing surface in contact with soil.

Loss of root hairs reduces the rate and effective surface area for initial uptake of water and minerals, so less material becomes available for xylem transport despite an intact vascular system.

Transpiration through stomata would fall sharply. Since transpiration contributes to the pull moving water upward through xylem, reduced water loss from leaves would reduce this driving force.

Thus xylem may remain structurally intact yet whole-plant water transport can still be affected because transport depends on coordinated activity of several tissues.

Mechanical strength and rigidity would increase, but flexibility would decrease. Collenchyma is adapted to support living growing regions while allowing bending. Heavily lignified sclerenchyma provides hard strength but is less suited to repeated flexible movement.

The stem would therefore become more rigid and more likely to resist bending rather than flex smoothly.

No. The definition involving similar cells applies especially well to simple tissues. Complex permanent tissues deliberately contain several cell types working together.

The listed components identify xylem. Their different structures allow them collectively to conduct water/minerals and provide mechanical support.

Food transport would be impaired because companion cells regulate important cellular functions of sieve tubes and are involved in sugar loading and unloading.

Therefore simply retaining the tube-shaped pathway is insufficient; phloem transport depends on cooperation between different cell types.

Roots depend on food produced in photosynthetic organs. Phloem transports that food to non-photosynthetic regions such as roots.

Removing a continuous ring of phloem interrupts the food-conducting pathway. Water may continue moving through xylem for some time, but root tissues can become deprived of food required for cellular activities.

No. Structure must match function.

The skin benefits from multiple layers because protection from friction and injury is important. In lungs, exchange requires a short diffusion distance, so a thin single-layered epithelium is more suitable. Replacing it with a thick multilayered barrier would hinder rapid gas exchange.

After a small cut, clot formation would be impaired or delayed because platelets are responsible for helping blood clot at an injury site.

Oxygen transport may remain comparatively normal because RBCs are present, and immune-cell number is assumed normal because WBCs are not reduced.

The joint would lose much of its cushioning and flexibility. Bone’s rigid mineralised matrix provides strength but is not designed to act as the soft shock-absorbing surface normally provided by cartilage.

Movement would therefore become less smooth and mechanical stress at the joint would increase.

Muscle contraction produces force, but that force must reach the bone. The tendon normally connects muscle to bone and transmits the pull.

If the tendon is severed, muscle fibres can still contract, yet the mechanical link to the bone is interrupted and effective joint movement may fail.

Joint stability would decrease. Ligaments connect bone to bone and limit excessive movement.

If a ligament becomes abnormally loose, the bones may move beyond the normal safe range even though muscular force transmission through tendons remains intact. Risk of instability or dislocation therefore increases.

• Skeletal muscle is primarily adapted for voluntary movement rather than the slow automatic movements required in the intestine.
• The intestine would lose specialised involuntary smooth-muscle activity required for continuous movement of its contents.

The hypothetical example illustrates the principle that specialised structure determines tissue function.

Similarity in striation does not mean identical function. Cardiac muscle is specialised for automatic, rhythmic and lifelong activity in the heart, whereas skeletal muscle normally performs voluntary movements.

The branching organisation and physiological specialisation of cardiac muscle therefore cannot simply be replaced by ordinary skeletal fibres.

The axon can carry signals away from the cell body, but the neuron must first receive incoming information. Dendrites are specialised for this receiving function.

A neuron with an intact output pathway but little effective input would therefore fail to participate normally in the communication network.

Movement is not simply muscle contraction. Nervous tissue receives, processes and transmits information needed to coordinate the musculoskeletal system.

If sensory information reaching the control system is impaired, the brain receives less information about the body and environment. Therefore even functional muscles may produce poorly coordinated responses.

A normal jump uses coordinated movement at several joints, especially hinge-type bending and straightening at the knees and associated ankle movement, along with movement at the hip.

Keeping joints stiff restricts the normal range over which muscles can move bones. The body therefore loses much of the coordinated musculoskeletal action that contributes to effective jumping.

The rib cage needs some flexibility to expand and contract. Flexible cartilage contributes to this movement.

If the relevant cartilage became completely rigid, rib-cage movement would decrease. Expansion of chest volume during breathing would become more difficult even though the rib bones themselves remained unbroken.

No complete demonstration of totipotency would occur.

The required sequence is approximately:

If the mature cells never dedifferentiate and regain division capacity, the regenerative pathway stops at the first critical stage. Mere survival of the cells is therefore not sufficient to establish totipotency.