Chapter-Tissues in Action Science Exploration class 9 in english Medium CBSE Notes

Chapter 3. Tissues in Action

This section explains why tissues are needed in multicellular organisms, the concept of division of labour, and the different types of plant tissues. It also introduces meristematic tissues, which are responsible for the growth of plants.

1. What is a Tissue?

In multicellular organisms, millions of cells perform different activities. Cells that have a similar structure and perform the same function group together to form a tissue. This organisation increases the efficiency of the organism.

Definition

A tissue is a group of similar cells having a common origin that work together to perform a specific function.

Characteristics of Tissues

• Similar Cells – Cells in a tissue have a similar structure and function.
• Common Function – All cells work together to perform one specific activity.
• Division of Labour – Different tissues perform different specialised functions.
• Higher Efficiency – Specialisation makes multicellular organisms more efficient.

Importance of Tissues

• Efficient Body Functions – Different tissues perform different tasks simultaneously.
• Growth and Repair – Help in growth, healing and replacement of damaged cells.
• Better Coordination – Different tissues coordinate to keep the organism alive.
• Formation of Organs – Tissues combine to form organs and organ systems.

2. Levels of Organisation

Living organisms are organised in different levels. Similar cells form tissues, tissues form organs, organs work together as organ systems, and organ systems together make a complete organism.

Organisation Sequence

Cell → Tissue → Organ → Organ System → Organism

Example

• Muscle Cell → Muscle Tissue
• Muscle Tissue → Heart
• Heart → Circulatory System
• Circulatory System → Human Body

3. Difference Between Plant and Animal Tissues

Plants and animals have different lifestyles. Plants remain fixed at one place, whereas animals move from one place to another. Therefore, their tissues differ in structure and function.

Plant Tissues	Animal Tissues
Growth is limited to specific regions.	Growth occurs throughout the body.
Many tissues provide mechanical support.	Many tissues help in movement.
Cells usually have a cell wall.	Cells do not have a cell wall.
Less energy is required.	More energy is required due to movement.
Examples: Xylem, Phloem.	Examples: Muscle, Nerve.

4. Plant Tissues

Plant tissues are groups of similar cells that perform specific functions such as growth, support, storage and transport of water and food.

Classification of Plant Tissues

• Meristematic Tissue – Responsible for the growth of plants.
• Permanent Tissue – Performs specialised functions after growth.

5. Meristematic Tissue

Meristematic tissues consist of actively dividing cells. These tissues are found in growing regions of plants and are responsible for increasing the length and thickness of the plant.

Definition

Meristematic tissue is a tissue made up of actively dividing cells that help plants grow.

Characteristics

• Actively Dividing Cells – Cells divide continuously.
• Thin Cell Wall – Primary cell wall is thin.
• Dense Cytoplasm – Cytoplasm is dense with a prominent nucleus.
• No Intercellular Spaces – Cells are tightly packed together.
• Small Vacuoles – Vacuoles are absent or very small.

Functions

• Plant Growth – Increases the size of the plant.
• Formation of New Cells – Produces permanent tissues.
• Healing – Helps repair damaged plant parts.

6. Types of Meristematic Tissue

Meristematic tissues are classified according to their location in the plant body.

Apical Meristem

• Location – Present at the tips of roots and shoots.
• Function – Increases the length of the plant (primary growth).

Intercalary Meristem

• Location – Present at the base of leaves or internodes.
• Function – Helps in rapid growth and regeneration, especially in grasses.

Lateral Meristem

• Location – Present along the sides of stems and roots.
• Function – Increases the thickness (secondary growth) of the plant.

Difference Between Types of Meristem

Type	Location	Function
Apical	Root and shoot tips	Increase in length
Intercalary	Leaf base and internodes	Rapid growth and regeneration
Lateral	Sides of stems and roots	Increase in thickness

7. Differentiation

As plants grow, meristematic cells gradually lose their ability to divide and become specialised for different functions. This process is known as differentiation.

Definition

Differentiation is the process by which meristematic cells become permanent tissues with specialised functions.

Importance

• Formation of Permanent Tissues – Produces specialised tissues.
• Division of Labour – Different tissues perform different functions.
• Efficient Plant Body – Helps plants carry out various life processes efficiently.

ATP Education Tip

Remember this sequence for examinations: Meristematic Tissue → Differentiation → Permanent Tissue. Also remember that Apical Meristem increases length, Lateral Meristem increases thickness, and Intercalary Meristem helps in rapid growth of grasses. These concepts are frequently asked in CBSE objective, competency-based and descriptive questions.

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