This MCQ module is based on: Organisation of Life — Why Tissues Matter
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Organisation of Life — Why Tissues Matter
🎓 Class 9
Science
CBSE
Theory
Ch 3 — Tissues in Action
⏱ ~9 min
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Organisation of Life — Why Tissues Matter
Class 9 Science · Chapter 3 · Part 1 — Levels of Biological Organisation
Introduction: From a Single Cell to a Whole Body
If you take a close look at a slice of onion or a drop of pond water under a microscope, you see lots of tiny boxes called cells. A single-celled creature like Amoeba performs every life process — eating, breathing, excreting, moving — using just that one cell. But what happens when an organism becomes large and complex, like a banyan tree or a human being? A single cell simply cannot carry out every function on its own.
To solve this problem, multicellular organisms have developed a clever strategy: division of labour. Different groups of cells specialise in different jobs. A nerve cell carries messages, a muscle cell contracts, a leaf cell makes food. When many cells of the same type team up to perform a particular task, they form a tissue.
Definition: A tissue is a collection of cells that look alike, share a common origin, and together carry out a particular function in the body of a multicellular organism.
3.1 Levels of Biological Organisation
Life is built up step by step. Each level is more complex than the one below it, but each level depends on the layer beneath it.
1
Cell
Smallest unit of life
2
Tissue
Similar cells, same job
3
Organ
Different tissues teamed up
4
Organ System
Organs working together
5
Organism
A complete living being
🧬 Levels of Life — Step through cell to organism L3 Apply
Click each level in turn (left to right) to walk through the worked example: "How is a heart actually built?". Each click adds a layer of organisation.
Click any level above to walk through the worked example: building a heart, step by step.
Why does a one-celled organism not need tissues?
An Amoeba moves with finger-like extensions of its single cell, eats by engulfing food, and breathes through its membrane. Because there is only one cell, every job happens inside that one cell. There is no need for specialisation — the whole creature is the cell.
Why do multicellular organisms need tissues?
In a tree or a tiger, billions of cells are present. If every cell tried to do everything, the body would be inefficient and waste energy. Instead, cells specialise. Some cells learn to conduct water (xylem), some carry messages (nerve cells), some store fat (adipose cells). This division of labour raises the efficiency of every life process and is the chief reason multicellular bodies have tissues.
Key Idea: Division of labour means different parts of the body do different specialised jobs. This makes large multicellular organisms efficient and successful.
3.2 Plant Tissues vs Animal Tissues — A First Look
Plants and animals are both multicellular, but their tissues are very different because their lifestyles are very different. A plant stays rooted in one place and grows for its entire life; an animal moves around to find food and shelter.
| Feature | Plant Tissues | Animal Tissues |
|---|---|---|
| Movement | Plants are stationary — most cells are stationary too. | Animals move; many tissues help in locomotion. |
| Growth | Limited to certain growing regions (meristems). | Growth is uniform till adulthood, then stops. |
| Cell wall | Present, made of cellulose. | Absent. |
| Energy needs | Lower — many tissues are dead and supportive. | Higher — tissues are alive and active. |
| Main types | Meristematic and Permanent (Simple, Complex) | Epithelial, Connective, Muscular, Nervous |
Activity 3.1 — Spotting Division of Labour Around YouL3 Apply
Predict first: List three jobs your body does right now (for example, breathing, beating heart, blinking). Do you think the same kind of cell does all three?
- Sit quietly for one minute and pay attention to as many things your body is doing as possible — heartbeat, eye movement, digestion, breathing, sweating, etc.
- Make a table with two columns: Function and Likely tissue or organ.
- For each function, write down which body part you think handles it.
- Discuss with a partner: would a single cell, like Amoeba, be able to do all these things together?
Heartbeat is done by cardiac muscle tissue; breathing involves epithelial tissue in the lungs; eye movement uses striated muscle tissue; digestion is done by glandular and epithelial tissues. No single cell can multitask like this — division of labour through tissues is essential.
Tissues build organs, organs build systems
An organ such as the heart is not made from a single tissue — it is built from several. The heart contains muscle tissue (to contract), connective tissue (to hold parts together), epithelial tissue (lining the chambers) and nervous tissue (controlling rhythm). Similarly, a leaf has epidermis, parenchyma, and vascular tissue all working together.
Remember: Tissues are the bridge between single cells and large complex bodies. Without tissues, there could be no organs, no organ systems, and no large multicellular life as we know it.
Competency-Based Questions
Riya watches an Amoeba under the microscope and is amazed that one tiny cell can eat, move, breathe and reproduce. She then dissects an earthworm and is surprised at how many different cell types it has.
Q1. Why does Amoeba not need tissues, but the earthworm does? L2
Amoeba is unicellular, so its single cell performs all life processes. The earthworm is multicellular and uses division of labour — different tissues handle different jobs efficiently.
Q2. Arrange in correct order: organ, cell, organism, tissue, organ system.
(a) — life is built up from the smallest unit (cell) to the whole organism.
Q3. Define the term 'tissue' in your own words. L1
A tissue is a group of cells that look the same and have a common origin and that work together to perform a particular function in the body.
Q4. State two differences between plant tissues and animal tissues. L2
(i) Plant tissues have cell walls, animal tissues do not. (ii) Plants grow from special regions called meristems, while animals grow uniformly during youth and stop later. Many plant tissues are dead and supportive; most animal tissues are alive and active.
Q5. The heart is built of several tissues. List the four tissues found in it and the role of each. L3
Cardiac muscle (rhythmic contraction), connective tissue (holds parts together), epithelial tissue (lines the chambers and blood vessels), nervous tissue (regulates the heartbeat).
Assertion–Reason Questions
Choose: (A) Both A and R true and R explains A. (B) Both true but R does not explain A. (C) A true, R false. (D) A false, R true.
Assertion: Multicellular organisms show division of labour.
Reason: Specialisation makes life processes more efficient.
(A) — division of labour exists precisely because specialisation increases efficiency.
Assertion: Amoeba does not have tissues.
Reason: Amoeba is a unicellular organism.
(A) — having only one cell, Amoeba cannot have a group of similar cells; hence no tissues exist.
Assertion: All cells in a tissue have the same origin.
Reason: Cells in a tissue may differ in shape but always perform different functions.
(C) — Assertion is true, but the reason is false. Cells in the same tissue look alike and perform the same function, not different ones.
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