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These are complete exercise solutions for Samacheer Kalvi 9th Science — Organization of Tissues. Solve each question yourself first, then verify your method and answer below. Pay special attention to the structural features that distinguish each tissue type.
Key Concepts (Quick Recap)
- Tissue: A group of structurally similar cells performing a common function.
- Plant tissues:
- Meristematic: Actively dividing cells — apical (tip growth), lateral (girth growth), intercalary (node growth).
- Permanent: Mature, non-dividing — simple (parenchyma, collenchyma, sclerenchyma) and complex (xylem, phloem).
- Parenchyma: Thin-walled, living, large intercellular spaces — storage, photosynthesis (chlorenchyma), buoyancy (aerenchyma).
- Collenchyma: Thickened walls at corners, living, flexible support in young stems.
- Sclerenchyma: Thick lignified walls, dead at maturity, no intercellular spaces — rigid mechanical support.
- Xylem: Conducts water and minerals upward; elements — tracheids, vessels, xylem parenchyma, xylem fibres.
- Phloem: Conducts food (translocation); elements — sieve tubes, companion cells, phloem parenchyma, phloem fibres.
- Animal tissues:
- Epithelial: Covers body surface, lines cavities; squamous, cuboidal, columnar, ciliated, glandular.
- Connective: Binds, supports, fills spaces; areolar, adipose, dense, bone, cartilage, blood, lymph.
- Muscular: Voluntary (striated/skeletal), involuntary (smooth), cardiac (heart only).
- Nervous: Neurons with cell body, dendrites, axon — transmits impulses.
I. Choose the Correct Answer
Q1. The tissue responsible for increase in girth (thickness) of a plant stem is: (a) Apical meristem (b) Intercalary meristem (c) Lateral meristem ✓ (d) Parenchyma
Answer(c) ✓ — Lateral meristem (cambium) is responsible for secondary growth, which increases the girth (diameter) of the stem and root.
Q2. Which plant tissue has thick lignified walls and is dead at maturity? (a) Parenchyma (b) Collenchyma (c) Sclerenchyma ✓ (d) Meristematic
Answer(c) ✓ — Sclerenchyma cells have thick, lignified secondary cell walls and are dead when mature. They provide rigid mechanical support.
Q3. The tissue that transports food in plants is: (a) Xylem (b) Phloem ✓ (c) Parenchyma (d) Collenchyma
Answer(b) ✓ — Phloem conducts synthesised food (sugars) from leaves to other parts of the plant by translocation.
Q4. Blood is an example of which type of tissue? (a) Epithelial (b) Muscular (c) Connective ✓ (d) Nervous
Answer(c) ✓ — Blood is a fluid connective tissue with plasma, RBCs, WBCs, and platelets. It connects various body parts by transporting substances.
Q5. Which animal tissue has striations and is voluntary? (a) Smooth muscle (b) Cardiac muscle (c) Skeletal (striated) muscle ✓ (d) Nervous tissue
Answer(c) ✓ — Skeletal (striated/voluntary) muscles are attached to bones, have alternate light and dark bands (striations), and are under conscious control.
Q6. Aerenchyma is a modified form of: (a) Parenchyma ✓ (b) Collenchyma (c) Sclerenchyma (d) Meristematic tissue
Answer(a) ✓ — Aerenchyma is parenchyma with large air cavities, found in aquatic plants. It provides buoyancy and helps them float.
Q7. Neurons are the functional units of: (a) Epithelial tissue (b) Connective tissue (c) Muscular tissue (d) Nervous tissue ✓
Answer(d) ✓ — Neurons (nerve cells) are the structural and functional units of nervous tissue. They receive, process, and transmit nerve impulses.
Q8. Which tissue lines the kidney tubules and salivary ducts? (a) Squamous epithelium (b) Cuboidal epithelium ✓ (c) Columnar epithelium (d) Ciliated epithelium
Answer(b) ✓ — Cuboidal epithelium consists of cube-shaped cells and lines kidney tubules, salivary ducts, and thyroid vesicles. It provides mechanical support and helps in absorption and secretion.
Q9. The waxy layer secreted by epidermis of leaves is called: (a) Suberin (b) Cutin ✓ (c) Lignin (d) Chitin
Answer(b) ✓ — The epidermis of leaves secretes a waxy, water-resistant layer called cutin, which forms the cuticle and prevents water loss.
Q10. Companion cells are associated with: (a) Xylem vessels (b) Sieve tubes ✓ (c) Tracheids (d) Collenchyma
Answer(b) ✓ — Companion cells are specialised parenchymatous cells found alongside sieve tubes in phloem. They help regulate the metabolic activities of sieve tube elements.
II. Fill in the Blanks
1. A group of similar cells performing a specific function is called a tissue. 2. The tissue responsible for increase in length of the plant is apical meristem. 3. Sclerenchyma tissue provides rigidity and mechanical strength to the plant. 4. Xylem transports water and minerals from roots to the aerial parts. 5. Phloem transports food (synthesised organic nutrients) from leaves to other parts. 6. The lining of blood vessels is made of squamous epithelium tissue. 7. Adipose tissue stores fat beneath the skin and acts as an insulator. 8. The cell wall of collenchyma is thickened at the corners (angles). 9. Aerenchyma is the modified parenchyma with large air cavities found in aquatic plants. 10. Cardiac muscle tissue is found only in the heart and is involuntary in action.
III. True or False
1. Meristematic cells have a large nucleus and dense cytoplasm.
AnswerTrue — Meristematic cells are actively dividing with a prominent nucleus, dense cytoplasm, and thin cell walls. They lack vacuoles.
2. Permanent tissues can divide throughout their life.
AnswerFalse — Correction: Permanent tissues are mature, non-dividing cells that have lost the ability to divide. Meristematic tissues can divide.
3. Sclerenchyma cells are living at maturity.
AnswerFalse — Correction: Sclerenchyma cells are dead at maturity because their cell walls are heavily thickened with lignin, leaving no space for cytoplasm.
4. Xylem is a complex permanent tissue.
AnswerTrue — Xylem is a complex tissue made of four types of cells: tracheids, vessels, xylem parenchyma, and xylem fibres.
5. Squamous epithelium provides protection against wear and tear.
AnswerTrue — Squamous epithelium forms a thin, flat layer that protects underlying tissues in areas like skin, oesophagus, and blood vessel lining.
6. Blood is a muscular tissue.
AnswerFalse — Correction: Blood is a fluid connective tissue. It consists of plasma and cells (RBCs, WBCs, platelets) suspended in it.
7. Smooth muscles are voluntary in action.
AnswerFalse — Correction: Smooth muscles are involuntary (not under conscious control). They are found in walls of internal organs like intestines, blood vessels, and uterus.
8. Neurons have dendrites and axons.
AnswerTrue — A neuron consists of a cell body (cyton), short branched dendrites (receive impulses), and a long axon (transmits impulses away from the cell body).
9. Cork cells contain suberin in their walls.
AnswerTrue — Cork (phellem) cells are dead cells with walls impregnated with suberin, making them impermeable to water and gases.
10. Collenchyma provides flexibility to the plant.
AnswerTrue — Collenchyma has thickened walls at corners but is living and flexible, allowing easy bending of young stems and leaf stalks without breaking.
IV. Match the Following
Set 1: Plant Tissues and Their Functions
| Column I (Tissue) | Column II (Function) |
|---|
| 1. Apical meristem | (c) Increase in length (primary growth) |
| 2. Lateral meristem | (e) Increase in girth (secondary growth) |
| 3. Parenchyma | (a) Storage and photosynthesis |
| 4. Collenchyma | (f) Flexible mechanical support |
| 5. Sclerenchyma | (b) Rigid mechanical support |
| 6. Xylem | (d) Conduction of water and minerals |
| 7. Phloem | (g) Conduction of food (translocation) |
Set 2: Animal Tissues and Their Locations
| Column I (Tissue) | Column II (Location/Function) |
|---|
| 1. Squamous epithelium | (d) Lining of blood vessels and oesophagus |
| 2. Cuboidal epithelium | (e) Kidney tubules and salivary ducts |
| 3. Columnar epithelium | (a) Intestine lining (absorption) |
| 4. Ciliated epithelium | (f) Respiratory tract (moves mucus) |
| 5. Adipose tissue | (b) Beneath skin (fat storage, insulation) |
| 6. Bone | (c) Skeletal framework (support and protection) |
| 7. Smooth muscle | (g) Walls of stomach and intestines (involuntary) |
V. Short Answers
Q1. Define tissue. Why are tissues important?
Answer
A tissue is a group of structurally similar cells that work together to perform a specific function. Tissues are important because: 1. They allow division of labour — different tissues perform different functions efficiently. 2. They provide organisation — cells are organised into tissues, tissues into organs, organs into organ systems. 3. They enable specialisation — cells within a tissue are adapted for a particular function.
Q2. Differentiate between meristematic and permanent tissues.
Answer
| Feature | Meristematic Tissue | Permanent Tissue |
|---|
| Cell division | Actively dividing | Non-dividing (mature) |
| Cell size | Small | Large (varying) |
| Cell wall | Thin | Thick (may be lignified) |
| Cytoplasm | Dense | Sparse |
| Nucleus | Large, prominent | Small or absent (in some) |
| Vacuoles | Absent or very small | Large (present) |
| Intercellular spaces | Absent | Present (in parenchyma) |
| Function | Growth (length/girth) | Storage, support, conduction |
Q3. What are the types of meristematic tissue? Where are they found?
Answer
1. Apical meristem: Found at the growing tips of stems and roots. Responsible for increase in length (primary growth). 2. Lateral meristem (Cambium): Found along the sides of stems and roots. Responsible for increase in girth (secondary growth). 3. Intercalary meristem: Found at the nodes (base of internodes) in grasses and monocots. Responsible for regrowth of parts after grazing or mowing.
Q4. Describe the structure and function of parenchyma.
Answer
Structure:
- Cells are living, thin-walled, and loosely packed.
- Large intercellular spaces between cells.
- Large central vacuole.
- Cytoplasm and nucleus are present.
Functions:
- Storage: Stores food (starch, sugars, proteins), water, and waste products.
- Photosynthesis: When parenchyma contains chloroplasts, it is called chlorenchyma (e.g., mesophyll in leaves).
- Buoyancy: In aquatic plants, parenchyma with large air cavities is called aerenchyma — helps plants float.
- Healing: Parenchyma cells can divide and help in wound healing.
Q5. Compare collenchyma and sclerenchyma.
Answer
| Feature | Collenchyma | Sclerenchyma |
|---|
| Cell wall | Thickened at corners (cellulose + pectin) | Uniformly thick (lignin) |
| Living/Dead | Living | Dead at maturity |
| Cytoplasm | Present | Absent |
| Intercellular spaces | Absent | Very narrow or absent |
| Nature of support | Flexible (allows bending) | Rigid (provides hardness) |
| Location | Below epidermis in young stems, leaf stalks | Veins of leaves, hard seed coats, husk of coconut |
| Examples | Stalks of celery, leaf stalks of Begonia | Coconut husk, jute fibres, seed coats |
Q6. What is the epidermis? What is its role in plants?
Answer
The epidermis is the outermost layer of cells covering the entire plant body (leaves, stems, roots). It is a single layer of flattened, closely packed cells without intercellular spaces.
Role: 1. Protection: Protects inner tissues from mechanical injury, pathogens, and desiccation. 2. Cuticle: Secretes a waxy, water-resistant cuticle (cutin) on the surface to reduce water loss (transpiration). 3. Stomata: Contains stomata (pores) guarded by guard cells, for gas exchange and transpiration. 4. Root hairs: Epidermal cells in roots form root hairs for water and mineral absorption.
In older stems and roots, the epidermis is replaced by cork (phellem) — dead cells with suberin in their walls, making them impermeable.
VI. Detailed Answers
Q1. Describe the different types of simple permanent tissues in plants.
Answer
Simple permanent tissues are made of only one type of cell. There are three types:
1. Parenchyma:
Answer
- Thin-walled, living cells with large intercellular spaces.
- Large central vacuole, prominent nucleus.
- Provides storage, photosynthesis (chlorenchyma), and buoyancy (aerenchyma).
- Present in cortex, pith, mesophyll of leaves.
- Can regain the ability to divide (when needed for healing).
2. Collenchyma:
Answer
- Living cells with cell walls thickened at the corners (due to cellulose and pectin deposition).
- No intercellular spaces.
- Provides flexible mechanical support — allows bending without breaking.
- Found below the epidermis in young stems, petioles (leaf stalks), and midribs of leaves.
- Example: Stalks of celery are collenchyma.
3. Sclerenchyma:
Answer
- Dead cells with heavily thickened, lignified cell walls.
- No intercellular spaces, no cytoplasm or nucleus.
- Provides rigid mechanical support and protection.
- Two types: Fibres (long, narrow) and Sclereids (short, irregular).
- Found in veins of leaves, hard seed coats, husk of coconut, and around vascular bundles in stems.
Q2. Explain the structure and function of xylem and phloem (complex permanent tissues).
Answer
Xylem (Water-conducting tissue):
| Element | Structure | Function |
|---|
| Tracheids | Dead, elongated, lignified, with bordered pits | Conduct water vertically; provide mechanical support |
| Vessels | Dead, long tubular structures formed by vessel elements end-to-end | Main pathway for water transport (most efficient) |
| Xylem parenchyma | Living, thin-walled cells | Store food and help in lateral conduction |
| Xylem fibres | Dead, long, narrow, thick-walled | Provide mechanical strength |
- Xylem conducts water and dissolved minerals from roots upward to all plant parts (ascent of sap).
- Primary xylem is formed during primary growth; secondary xylem (wood) during secondary growth.
Phloem (Food-conducting tissue):
| Element | Structure | Function |
|---|
| Sieve tubes | Living, no nucleus, sieve plates at end walls | Conduct food (sugars) through sieve pores |
| Companion cells | Living, nucleated, alongside sieve tubes | Regulate metabolic activities of sieve tubes |
| Phloem parenchyma | Living, thin-walled cells | Store food and other substances |
| Phloem fibres | Dead, sclerenchymatous | Provide mechanical support |
- Phloem transports synthesised food (sucrose, amino acids) from leaves to all plant parts — this process is called translocation.
- Transport is bidirectional (upward and downward, unlike xylem which is upward only).
Q3. Describe the different types of epithelial tissues with their locations and functions.
Answer
| Type | Shape | Location | Function |
|---|
| Squamous | Flat, thin, scale-like | Lining of blood vessels, heart, oesophagus, alveoli, skin (outer layer) | Protection, diffusion, filtration |
| Cuboidal | Cube-shaped (equal height and width) | Kidney tubules, salivary ducts, thyroid vesicles | Absorption, secretion, mechanical support |
| Columnar | Tall, pillar-like | Inner lining of intestine, stomach | Absorption, secretion (mucus) |
| Ciliated columnar | Columnar with cilia on free surface | Respiratory tract, fallopian tubes | Move mucus/particles/ova in a direction |
| Glandular | Modified columnar/cuboidal | Sweat glands, salivary glands, mammary glands | Secrete substances (sweat, saliva, milk, enzymes) |
| Stratified squamous | Multiple layers of flat cells | Skin (epidermis) | Protection against wear and tear |
Key features of epithelial tissue:
- Cells are tightly packed with almost no intercellular spaces.
- Rest on a basement membrane (a non-cellular layer of protein and polysaccharides).
- One surface is free (apical), the other is attached to the basement membrane (basal).
- Forms a barrier between the body and the external environment.
Q4. Describe the three types of muscular tissue and compare them.
Answer
| Feature | Skeletal (Striated) | Smooth (Unstriated) | Cardiac |
|---|
| Location | Attached to bones | Walls of stomach, intestines, blood vessels | Wall of heart only |
| Control | Voluntary (conscious) | Involuntary (automatic) | Involuntary (automatic) |
| Shape | Long, cylindrical, multinucleate | Spindle-shaped, uninucleate | Branched, uninucleate |
| Striations | Present (light and dark bands) | Absent | Present (faint) |
| Contraction | Powerful, rapid, fatigue-prone | Slow, sustained, fatigue-resistant | Rhythmic, tireless |
| Intercalated discs | Absent | Absent | Present (unique feature) |
1. Skeletal (Striated/Voluntary) muscle:
Answer
- Attached to bones by tendons.
- Long, cylindrical fibres with multiple nuclei at the periphery.
- Alternate light (I-band) and dark (A-band) striations.
- Under conscious control — used for body movement.
2. Smooth (Unstriated/Involuntary) muscle:
Answer
- Spindle-shaped cells with a single central nucleus.
- No striations — appear smooth under the microscope.
- Found in walls of hollow organs (intestine, blood vessels, uterus, urinary bladder).
- Under involuntary control — responsible for peristalsis and other automatic movements.
3. Cardiac muscle:
Answer
- Found only in the walls of the heart.
- Branched fibres with intercalated discs (special junctions for rapid impulse transmission).
- Uninucleate, faint striations.
- Involuntary and tireless — contracts rhythmically throughout life without fatigue.
Common Mistakes
1. Confusing meristematic and permanent tissues — Meristematic tissues divide actively and have thin walls, dense cytoplasm, and large nuclei. Permanent tissues are mature, non-dividing, and may have thick walls.
2. Calling xylem and phloem "simple tissues" — Xylem and phloem are complex permanent tissues because each is made of multiple cell types (tracheids, vessels, fibres, parenchyma in xylem; sieve tubes, companion cells, fibres, parenchyma in phloem).
3. Confusing collenchyma and sclerenchyma — Collenchyma is living, flexible, with wall thickening at corners. Sclerenchyma is dead, rigid, with uniformly thickened lignified walls.
4. Saying blood is an epithelial or muscular tissue — Blood is a connective tissue (fluid connective tissue). It has plasma (matrix) and cells (RBCs, WBCs, platelets) that connect different body parts by transporting substances.
5. Confusing skeletal and cardiac muscle — Skeletal muscle is voluntary, multinucleate, and attached to bones. Cardiac muscle is involuntary, uninucleate, branched, with intercalated discs, and found only in the heart.
6. Forgetting that sieve tubes lack a nucleus — Mature sieve tube elements in phloem are living but enucleate (no nucleus). Companion cells alongside them have nuclei and regulate their activity.
7. Mixing up apical, lateral, and intercalary meristems — Apical = growth in length (tips of stem/root). Lateral = growth in girth (cambium). Intercalary = growth at nodes (grasses, monocots).
Exam Checklist
- [ ] Definition of tissue and importance of tissue-level organisation
- [ ] Meristematic tissue: types (apical, lateral, intercalary) — location and function of each
- [ ] Simple permanent tissues: parenchyma, collenchyma, sclerenchyma — structure, function, differences
- [ ] Complex permanent tissues: xylem (4 elements) and phloem (4 elements) — structure and function
- [ ] Epidermis, cuticle, stomata, cork — protective tissues
- [ ] Epithelial tissues: squamous, cuboidal, columnar, ciliated, glandular — location and function
- [ ] Connective tissues: areolar, adipose, bone, cartilage, blood — structure and function
- [ ] Muscular tissues: skeletal, smooth, cardiac — comparison table memorised
- [ ] Nervous tissue: neuron structure (cyton, dendrites, axon) and function
- [ ] Common mistakes: xylem/phloem as complex tissue, sieve tubes enucleate, collenchyma vs sclerenchyma
Internal Links
- [Organization of Tissues Guide](/school/tamil-nadu-state-board/class/9/science/organization-of-tissues)
- [All Class 9 Science Solutions](/school/tamil-nadu-state-board/class/9/science/solutions)
- [Class 9 Science Subject Guide](/school/tamil-nadu-state-board/class/9/science)
