Tissues — Class 9 Science: quick revision, 15 bites

Tissues: The Building Blocks of Life

Cells team up to form tissues.

In multicellular organisms, cells are organized into **tissues**. A tissue is a group of similar cells that work together to perform a specific function. This division of labour allows organisms to grow larger and more complex.

Takeaway. Tissues are groups of similar cells performing a specific function.

Meristematic Tissue

Growth happens here.

**Meristematic tissue** is found in growing regions of plants. Its cells divide actively to produce new cells, leading to increase in length (primary growth) and thickness (secondary growth).

Takeaway. Meristematic tissue is responsible for plant growth.

Permanent Tissue

Once grown, cells specialize.

**Permanent tissues** are derived from meristematic tissue. Their cells have lost the ability to divide and have taken up specific roles. They are classified into **simple** and **complex** tissues.

Takeaway. Permanent tissues are specialized and non-dividing.

Simple vs Complex Permanent Tissues

One cell type vs many.

Takeaway. Simple tissues have one cell type; complex tissues have multiple.

Parenchyma

The most common plant tissue.

**Parenchyma** is a simple permanent tissue with living, thin-walled cells. It is found in all soft parts of plants. Its main functions are **storage** and **photosynthesis** (when containing chloroplasts).

Takeaway. Parenchyma stores food and helps in photosynthesis.

Collenchyma

Flexible support for growing parts.

**Collenchyma** is a simple permanent tissue with living cells that have **thickened corners** due to cellulose deposition. It provides **mechanical support** and flexibility to growing parts like stems and leaves.

Takeaway. Collenchyma provides flexible support to growing plant parts.

Sclerenchyma

Dead but strong.

**Sclerenchyma** is a simple permanent tissue with **dead cells** that have **thick lignified walls**. It provides **rigidity** and **strength** to the plant. It is found in stems, roots, and veins of leaves.

Takeaway. Sclerenchyma makes plant parts hard and stiff.

Xylem

Water transport superhighway.

**Xylem** is a complex permanent tissue that conducts **water and minerals** from roots to other parts. It consists of **tracheids**, **vessels**, **xylem parenchyma**, and **xylem fibres**.

Takeaway. Xylem transports water and minerals upward.

Phloem

Food transport network.

**Phloem** is a complex permanent tissue that transports **food** (sugars) from leaves to other parts. It consists of **sieve tubes**, **companion cells**, **phloem parenchyma**, and **phloem fibres**.

Takeaway. Phloem transports food in plants.

Epithelial Tissue

The body's protective covering.

**Epithelial tissue** covers the external surfaces and lines internal cavities of animals. It forms a protective barrier and is involved in absorption, secretion, and filtration.

Takeaway. Epithelial tissue covers and protects body surfaces.

Connective Tissue

Connecting and supporting the body.

**Connective tissue** connects, supports, and binds other tissues. Its cells are loosely spaced in an intercellular matrix. Examples include **bone**, **cartilage**, **blood**, and **adipose tissue**.

Takeaway. Connective tissue binds and supports other tissues.

Muscular Tissue

Movement made possible.

**Muscular tissue** is responsible for movement in the body. It consists of elongated cells called **muscle fibres** that contain contractile proteins. It is of three types: **striated**, **smooth**, and **cardiac**.

Takeaway. Muscular tissue enables movement through contraction.

Nervous Tissue

Control and coordination.

**Nervous tissue** is made of specialized cells called **neurons**. It receives and transmits stimuli, enabling rapid communication within the body. It is found in the brain, spinal cord, and nerves.

Takeaway. Nervous tissue transmits electrical impulses for coordination.

Plant vs Animal Tissues

Different needs, different tissues.

Takeaway. Plant and animal tissues differ in structure and function.

Exam Tip: Tissue Functions

Remember the key functions.

In exams, questions often ask for the **function** of specific tissues. Make a table linking each tissue to its main function. For example: **Xylem** → water conduction; **Phloem** → food conduction; **Epithelial** → protection; **Nervous** → coordination.

Takeaway. Link each tissue to its primary function for quick recall.