🔬 What Is a Tissue?
A tissue is a group of similar cells that work together to perform a specific function. Its cells generally share a common origin and structural features suited to that function.
1. Examples of tissues
| Tissue | Main function | Example / location |
|---|---|---|
| Epithelial | Covers and protects surfaces | Skin |
| Muscular | Produces movement | Muscles |
| Nervous | Transmits signals | Brain and nerves |
| Xylem | Transports water and minerals | Plant vascular tissue |
| Phloem | Transports prepared food | Plant vascular tissue |
2. Why do multicellular organisms need tissues?
A unicellular organism is a single cell doing every job needed for life. A multicellular organism has many cells, and different cells specialise for different tasks.
In humans
- Muscle cells help produce movement.
- Nerve cells transmit signals.
- Epithelial cells cover and line surfaces.
- Blood transports substances around the body.
In plants
- Meristematic tissues produce new cells for growth.
- Xylem transports water and minerals.
- Phloem transports prepared food.
- Protective tissues protect plant surfaces.
3. Division of labour
Division of labour is the distribution of different functions among specialised cells, tissues, organs or organ systems. Instead of every cell doing every task, different groups do specific jobs.
| Human body | Function | Plant body | Function |
|---|---|---|---|
| Muscle tissue | Movement | Meristematic tissue | Growth |
| Nervous tissue | Communication, coordination | Xylem | Water and mineral transport |
| Epithelial tissue | Covering, lining, protection | Phloem | Food transport |
| Blood | Transport of substances | Protective tissue | Protection |
Why is it important?
- Specialised functions are performed efficiently.
- Different tissues can work together.
- It supports the functioning of complex multicellular organisms.
4. Levels of organisation
Cell→Tissue→Organ→Organ system→Organism
- Cell: basic structural and functional unit of life (a muscle cell).
- Tissue: group of similar cells working together (muscular tissue).
- Organ: different tissues working together (the stomach).
- Organ system: organs working together for major functions (the digestive system).
- Organism: the complete living individual (a human being).
Important: different tissues form organs; different organs cooperate within organ systems.
5. Structure and function
| Tissue | Structural feature | How it helps |
|---|---|---|
| Epithelial | Cells closely packed | Covering and protection |
| Muscular | Contractile machinery in cells | Produces movement |
| Nervous | Neurons with specialised extensions | Transmits signals |
| Xylem | Specialised conducting elements | Transports water and minerals |
| Phloem | Specialised conducting cells | Transports prepared food |
Exam keyword: structural adaptation to function.
6. Tissue formation: a simple explanation
Cells→Specialisation→Tissues→Organs→Organ systems
In plants, meristematic cells divide and can later become specialised permanent tissues. In animals, cells also specialise to form different tissues. Not all cells in a tissue are identical in every detail; what matters is that they cooperate in a common function and have structure suited to it.
7. Practice questions
One mark
Q1. What is a tissue?A group of similar cells that work together to perform a specific function.
Q2. What is division of labour?Distribution of different functions among specialised cells, tissues, organs or organ systems.
Q3. Basic structural and functional unit of life?The cell.
Q4. Tissue responsible for body movement?Muscular tissue.
Q5. Plant tissue that transports water and minerals?Xylem.
Q6. Which tissue transmits signals in animals?Nervous tissue.
Q7. What forms when different tissues work together?An organ.
Q8. Organ system including stomach and intestines?The digestive system.
Two marks
Q1. Why are tissues important in multicellular organisms?They let cells specialise in particular functions. This division of labour improves efficiency and allows complex life processes.
Q2. Differentiate between a cell and a tissue.Cell: basic structural and functional unit of life. Tissue: group of similar cells working together for a specific function.
Q3. What is division of labour? Give one example.Distribution of different functions among specialised structures. E.g., muscular tissue produces movement while nervous tissue transmits signals.
Q4. Explain structure and function in tissues.Cells have structural features suited to their functions. E.g., muscle cells are specialised for contraction, so muscular tissue produces movement.
Three marks
Q1. Explain the levels of organisation.Cell (basic unit of life) → Tissue (similar cells working together) → Organ (different tissues performing a function) → Organ system (organs coordinating activities) → Organism (complete living individual).
Q2. Importance of division of labour.Different functions go to specialised structures: muscular tissue for movement, nervous tissue for signals, epithelial tissue for covering and protection. This lets complex life processes be performed efficiently.
Q3. How are tissues, organs and organ systems related?Similar cells form tissues. Different tissues combine to form organs. Several organs work together in organ systems for major life processes, and all organ systems together run the organism.
Assertion–Reason
1. A: Division of labour improves efficiency. R: Different specialised structures perform different functions.A
2. A: An organ is generally made of different tissues. R: Different tissues can work together to perform an organ’s functions.A
3. A: All tissues perform exactly the same function. R: Different tissues are specialised for different functions.D
4. A: Muscular tissue helps produce movement. R: Muscle cells are specialised for contraction.A
HOTS and competency-based
Q1. An organism has many cells, none specialised. What problem could arise?Functions might not be performed efficiently, as there would be little division of labour.
Q2. A student says muscle and nerve cells form the same tissue because both are in the body. Correct?No. They differ in structure and function: muscle cells form muscular tissue, nerve cells form nervous tissue.
Q3. A plant’s xylem is damaged. Which function is affected most directly?Transport of water and minerals from roots to other parts.
Q4. Why is the stomach an organ, not a tissue?It contains different tissues (epithelial, connective, muscular, nervous) working together for digestion.
Q5. A student writes: cell → organ → tissue → organism → organ system. Find the mistake.Wrong order. Correct: Cell → Tissue → Organ → Organ system → Organism.
Fill in the blanks
| # | Question | Answer |
|---|---|---|
| 1 | A group of similar cells performing a specific function is a ______. | Tissue |
| 2 | The basic structural and functional unit of life is the ______. | Cell |
| 3 | Distributing functions among specialised structures is division of ______. | Labour |
| 4 | Different tissues work together to form an ______. | Organ |
| 5 | A group of organs working together forms an organ ______. | System |
| 6 | Muscular tissue is specialised for ______. | Contraction / movement |
| 7 | Nervous tissue helps transmit ______. | Signals |
| 8 | ______ transports water and minerals in plants. | Xylem |
| 9 | Phloem transports prepared ______ in plants. | Food |
| 10 | Cell → Tissue → Organ → Organ system → ______. | Organism |