TISSUES CHAPTER CLASS 9 NCERT

 

🔹 Subject: Science (Biology)🔹 Class: 9 🔸 Chapter Number: 6 (as per NCERT Book)

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🔷 Introduction

• Definition of Tissue: A group of cells that are similar in structure and perform a specific function.
• Need for Tissues: In multicellular organisms, division of labour occurs — different tissues perform different functions efficiently.
• Types of Tissues: Mainly classified into Plant Tissues and Animal Tissues.

 

🌿 Plant Tissues

Plants have two main types of tissues:

1. Meristematic Tissue (Growth Tissues)

• Location: Found in the growing regions of the plant (tips of roots and shoots).
• Characteristics:
• Actively dividing cells
• Thin cell walls
• Dense cytoplasm, large nuclei, no vacuoles
• Types of Meristematic Tissue:
• Apical Meristem: Found at root and shoot tips; responsible for growth in length.
• Lateral Meristem (e.g., cambium): Causes growth in girth (width).
• Intercalary Meristem: Located at nodes or internodes in some plants; helps in elongation.

2. Permanent Tissue

Formed from meristematic tissue once the cells lose the ability to divide.

A. Simple Permanent Tissue

• Made of similar types of cells.
• Types:

1.    Parenchyma:

§  Living cells, thin cell walls

§  Functions: Photosynthesis, storage

§  May have chloroplasts → Called chlorenchyma

§  In aquatic plants: air cavities → aerenchyma

2.    Collenchyma:

§  Living cells, thickened corners

§  Provides mechanical support and flexibility (e.g., in petioles)

3.    Sclerenchyma:

§  Dead cells with thick lignified walls

§  Provides rigid support (e.g., coconut husk fibers)

B. Complex Permanent Tissue

• Made of different kinds of cells performing a common function.
• Types:

1.    Xylem (Conducts water and minerals from roots to other parts):

§  Tracheids, Vessels, Xylem Parenchyma, Xylem Fibres (Tracheids and vessels are tubular structures. This allows them to transport water and minerals vertically.)

2.    Phloem (Transports food from leaves to the rest of the plant):

§  Sieve tubes, Companion cells, Phloem Parenchyma, Phloem Fibres

 

🐾 Animal Tissues

Animal tissues are more specialized and complex due to varied activities. Four major types:

1. Epithelial Tissue (Covering or lining tissue)

• Covers body surfaces, lines internal organs and cavities.
• Types:

1.    Simple Squamous – thin, flat cells (e.g., in blood vessels)

2.    Cuboidal – cube-shaped (e.g., kidney tubules)

3.    Columnar – tall, pillar-like cells (e.g., lining of intestine)

4.    Ciliated Epithelium – columnar/cuboidal cells with cilia (e.g., respiratory tract)

5.    Stratified Epithelium – layers of cells for protection (e.g., skin)

 

 

2. Connective Tissue (Binding and supporting)

• Connects, supports, and binds organs.
• Types:

1.    Areolar Tissue – beneath skin; fills space between organs

2.    Adipose Tissue – stores fat

3.    Bone – hard matrix; supports and protects

4.    Cartilage – flexible; at joints, nose, ear

5.    Ligament – bone to bone (elastic)

6.    Tendon – muscle to bone (tough, less elastic)

7.    Blood – fluid connective tissue; transports nutrients, gases

3. Muscular Tissue (Movement)

• Responsible for movement of body parts.
• Types:

1.    Striated (Skeletal) Muscle – voluntary, striped, attached to bones

2.    Smooth Muscle – involuntary, non-striated, in internal organs

3.    Cardiac Muscle – involuntary, striated, found only in the heart

4. Nervous Tissue (Control and coordination)

• Made of neurons (nerve cells)
• Function: Transmit electrical impulses throughout the body
• Components: Cell body, axon, dendrites

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🔸 Conclusion

• Tissues enable efficient division of labour in both plants and animals.
• Plant tissues mainly support and transport.
• Animal tissues are more specialized and adapted for varied body functions like movement, coordination, and internal transport.

 

CLASSS 9 NCERT SCIENCE

CHITTARANJAN PARK, SOUTH DELHI