Chapter Overview & Weightage
Tissues (Chapter 6, Class 9 Science) is a core Biology chapter that introduces the hierarchy of organisation: cell → tissue → organ → organ system → organism. This chapter carries 8–12 marks in CBSE Class 9 exams and is essential background for Class 10’s “Life Processes” chapter.
| Question Type | Marks | Topics |
|---|---|---|
| MCQ | 1 | Definitions, examples of tissue types |
| Short Answer (SA-I) | 2 | Name and describe a tissue type |
| Short Answer (SA-II) | 3 | Compare two tissue types, function + structure |
| Long Answer | 5 | Types of plant/animal tissue with diagrams |
Diagram-based questions on meristematic tissue, blood, bone, and nerve are common. Practice labelling diagrams — a correct labelled diagram alone can fetch 2–3 marks.
Key Concepts You Must Know
What is a tissue? A group of cells with similar structure and function, often with the same origin.
Plant Tissues
Meristematic Tissue: Cells that actively divide. Found in growing regions.
- Apical meristem: tips of roots and shoots → increases length
- Lateral meristem: along sides → increases girth (e.g., vascular cambium, cork cambium)
- Intercalary meristem: at base of internodes (e.g., grasses) → regeneration after grazing
Permanent Tissues: Cells that have lost the ability to divide. Two types:
- Simple Permanent: All cells of same type
- Parenchyma: Thin-walled, loosely packed, large vacuoles. Stores food, does photosynthesis (chlorenchyma), floats in water (aerenchyma)
- Collenchyma: Unevenly thickened corners. Provides flexibility — found in leaf stalks
- Sclerenchyma: Thick, lignified cell walls, dead at maturity. Provides rigidity — coconut husk, jute fibres
- Complex Permanent: Different types of cells working together
- Xylem: Conducts water upward. Components: tracheids, vessels, xylem parenchyma, xylem fibres
- Phloem: Conducts food (usually downward). Components: sieve tubes, companion cells, phloem parenchyma, phloem fibres
Animal Tissues
Epithelial Tissue: Covers body surfaces and lines cavities. Types based on shape: squamous (flat), cuboidal, columnar; based on layers: simple, stratified. Functions: protection, secretion, absorption.
Connective Tissue: Connects and supports. Types:
- Blood: Plasma (liquid matrix) + RBCs + WBCs + platelets. Transports O₂, nutrients, waste, hormones
- Bone: Hard, calcified matrix. Supports and protects
- Cartilage: Flexible matrix. Nose, ear, joints, trachea
- Ligament: Connects bone to bone (elastic)
- Tendon: Connects muscle to bone (inelastic, strong)
Muscular Tissue:
- Striated/Skeletal: Voluntary, multinucleated, striated (striped). Attached to bones
- Smooth/Visceral: Involuntary, uninucleated, not striated. Walls of intestines, blood vessels
- Cardiac: Involuntary, uninucleated, slightly striated. Heart only. Never fatigues
Nervous Tissue: Neurons. Cell body + dendrites + axon. Transmits electrical impulses. Responds to stimuli.
Important Formulas
There are no mathematical formulas in this chapter. The “formula” to learn is the structure → function relationship for each tissue type.
Solved Previous Year Questions
PYQ 1 — Meristematic Tissue (3 marks)
Q: What is meristematic tissue? Mention its location and state two characteristics.
Solution: Meristematic tissue consists of cells that actively divide by mitosis. Found at the tips of roots and shoots (apical meristem), along the sides (lateral meristem), and at the base of internodes (intercalary meristem).
Two characteristics: (1) Cells are small with thin cell walls and large nuclei. (2) No vacuoles or very small vacuoles — cells must divide rapidly and cannot afford storage.
PYQ 2 — Comparison Question (3 marks)
Q: Compare ligaments and tendons.
Solution:
| Feature | Ligament | Tendon |
|---|---|---|
| Connects | Bone to bone | Muscle to bone |
| Elasticity | Elastic | Inelastic (tough) |
| Tissue type | Connective | Connective |
| Function | Holds joints together | Transmits muscle force to bone |
PYQ 3 — Cardiac vs Striated Muscle (2 marks)
Q: Give two differences between cardiac and striated (skeletal) muscle.
Solution:
| Feature | Cardiac | Skeletal/Striated |
|---|---|---|
| Control | Involuntary | Voluntary |
| Location | Heart only | Attached to bones |
| Nucleus | Uninucleate | Multinucleate |
| Fatigue | Does not fatigue | Fatigues |
PYQ 4 — Why do plant cells need sclerenchyma (2 marks)?
Solution: Sclerenchyma cells have thick, lignified walls. At maturity, they are dead — the living contents are no longer needed because the thick wall does the work. They provide mechanical strength and rigidity to plant parts. Jute (stem fibres), coconut husk, and seed coats contain sclerenchyma. Without it, tall plants could not remain erect.
Difficulty Distribution
| Difficulty | % of Questions | Types |
|---|---|---|
| Easy | 40% | Definitions, examples, simple identification |
| Medium | 45% | Compare two tissue types, explain function |
| Hard | 15% | Multi-tissue diagrams with labelling, why questions |
Expert Strategy
Draw comparison tables for every pair of tissues — xylem vs phloem, cardiac vs skeletal muscle, ligament vs tendon. Examiners love comparison questions and a table immediately shows you know both.
For diagram questions, practise drawing and labelling: (a) parenchyma/collenchyma/sclerenchyma cells, (b) blood smear (showing RBCs, WBCs), (c) types of muscle fibres. Each label is worth a mark.
The mnemonics “CSPY” for phloem components (Companion cells, Sieve tubes, Phloem parenchyma, phloem fibres) and “TPVF” for xylem (Tracheids, Pits/vessels, xylem parenchyma, xylem Fibres) can help you list all four components in any phloem/xylem question.
Common Traps
Trap 1 — Sclerenchyma is dead: Students forget that sclerenchyma cells are dead at maturity. The question “which plant tissue cells are dead?” can be answered: sclerenchyma (and cork cells). Parenchyma and collenchyma are alive.
Trap 2 — Blood is connective tissue: Blood is classified as connective tissue, not a separate category. The matrix (plasma) is liquid — this surprises students. Bone, blood, and cartilage are all connective tissues.
Trap 3 — Phloem conducts “food” not just sugar: Students write “phloem conducts sugar.” More precisely, it conducts elaborated food — primarily sucrose, but also amino acids and other organic compounds.