class 9 tissue chapter notes ncert

Class 9 Science: Tissue Chapter Notes

1. What is a Tissue?

A tissue is a group of cells that work together to perform a specific function. Tissues are of two main types: Plant Tissues and Animal Tissues.

2. Types of Plant Tissues

A. Meristematic Tissue

These tissues are responsible for growth in plants. The cells in meristematic tissue actively divide to produce new cells.

• Apical Meristem: Found at the tips of roots and shoots, responsible for growth in length.
• Intercalary Meristem: Found at the base of leaves or internodes, responsible for growth in certain parts.
• Lateral Meristem: Found on the sides of stems and roots, responsible for growth in thickness (e.g., Cambium).

B. Permanent Tissue

These are formed by meristematic tissues and do not divide. They are further divided into:

• Simple Permanent Tissue: Made of only one type of cell.
• Complex Permanent Tissue: Made of different types of cells that work together to perform a function.

Types of Simple Permanent Tissue:

• Parenchyma: Soft and packing tissue, involved in storage and photosynthesis.
• Collenchyma: Provides mechanical support and flexibility to plants.
• Sclerenchyma: Provides strength and rigidity to plants.

Types of Complex Permanent Tissue:

• Xylem: Conducts water and minerals from roots to other parts of the plant. It consists of tracheids, vessels, xylem fibers, and xylem parenchyma.
• Phloem: Transports food from leaves to other parts of the plant. It consists of sieve tubes, companion cells, phloem fibers, and phloem parenchyma.

3. Types of Animal Tissues

A. Epithelial Tissue

This tissue covers and protects the body and its organs. It forms a protective barrier and helps in absorption and secretion.

• Squamous Epithelium: Flat cells, found in linings of blood vessels and lungs.
• Cuboidal Epithelium: Cube-shaped cells, found in kidney tubules and gland ducts.
• Columnar Epithelium: Tall, pillar-like cells, found in the lining of the intestines and stomach.
• Ciliated Epithelium: Contains cilia, found in respiratory tract and fallopian tubes.

B. Connective Tissue

This tissue supports, connects, and binds different parts of the body.

• Bone: Rigid connective tissue, forms the skeleton.
• Cartilage: Flexible connective tissue, found in nose, ears, and joints.
• Blood: Fluid connective tissue, transports nutrients, gases, and waste products.
• Areolar Tissue: Binds skin to muscles, fills spaces between organs.
• Adipose Tissue: Stores fat, insulates the body.

C. Muscular Tissue

This tissue helps in movement and contraction. It is of three types:

• Skeletal Muscle: Voluntary muscles attached to bones, help in movement.
• Smooth Muscle: Involuntary muscles, found in organs like stomach, intestines.
• Cardiac Muscle: Involuntary muscle, found only in the heart, helps in pumping blood.

D. Nervous Tissue

This tissue is specialized for transmitting messages in the form of nerve impulses. It is made up of cells called neurons, which are the basic units of the nervous system.

4. Differences between Meristematic and Permanent Tissues

Feature	Meristematic Tissue	Permanent Tissue
Cell Division	Cells actively divide	Cells do not divide
Cell Shape	Small, thin-walled cells	Larger, more specialized cells
Location	Found in growing regions like tips of roots and shoots	Found in mature regions of the plant