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medium difficulty9 min

Why Tissues Are Needed

A tissue is a group of similar cells that work together to perform a specific function in an organism.

In one line: Same job, same team: similar cells doing one job make a tissue.

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Understand it

  • A unicellular organism uses one cell to carry out all life processes, but a multicellular organism has many jobs happening at the same time.
  • Its cells become specialised, so similar cells can work together as tissues.
  • This division of labour makes functions such as movement, transport, protection, and coordination faster and more efficient.
  • Tissues also form the next level of organisation: cells form tissues, tissues form organs, organs form organ systems, and organ systems work together in the organism.

Example

Muscle cells form muscle tissue for movement, nerve cells form nervous tissue for carrying messages, and xylem tissue in plants helps transport water.

Rule to remember

Cell → Tissue → Organ → Organ System → Organism.

Similar specialised cells form a tissue; tissues combine to form organs; organs work together as organ systems.

Sequence to remember

Cell>
Tissue>
Organ>
Organ system>
Organism

See it worked out

Follow the example line by line, then use the same method on new questions.

Worked example

Amoeba performs all life processes in one cell.

  1. 1In humans, muscle cells specialise in contraction and form muscle tissue, while nerve cells specialise in carrying messages and form nervous tissue.
  2. 2This specialisation helps the body perform many functions efficiently at the same time.

Method you can reuse

Write the definition first, then state the need as division of labour, then show the hierarchy from cell to organ system, and finally add one example such as muscle tissue for movement or nervous tissue for messages.

Sketch it in your answer

Use a flow chart: Cell → Tissue → Organ → Organ System → Organism. Add examples such as muscle cell → muscle tissue → heart and xylem cells → xylem tissue → stem/root.

Check yourself

Answer the question in your head before opening the answer.

Try it yourself

Why are tissues important in multicellular organisms?

Think first, then show answer
Tissues are important because similar specialised cells work together for one function, allowing division of labour. For example, muscle tissue helps in movement and nervous tissue carries messages.

Common wrong answer

A common wrong answer is 'a tissue is a group of cells.' It is incomplete because it misses similar cells, specialisation, and a specific function.

Don't mix this up

Students often write that a tissue is just a group of cells. That is incomplete because the cells must usually be similar in structure and must work together for a specific function.

Exam tip

For a strong answer, write the definition, explain division of labour, show the order cell → tissue → organ → organ system → organism, and give one real tissue example.

Write it in the exam

How CBSE asks it

Questions may ask why tissues are needed in multicellular organisms, how unicellular and multicellular organisation differs, or the correct order from cell to organ system.

1-mark answer

Tissues are needed because similar specialised cells work together to perform one function efficiently in multicellular organisms.

2-mark answer

A tissue is a group of similar cells performing a specific function. Tissues allow division of labour, such as muscle tissue for movement and nervous tissue for carrying messages.

3-mark answer

A tissue is a group of similar cells that work together for a specific function. In multicellular organisms, tissues are needed for division of labour because one cell cannot perform all body functions efficiently. Cells form tissues, tissues form organs, and organs form organ systems; for example, muscle tissue helps movement and xylem tissue transports water in plants.
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