Introduction (Class 9 Science Chapter 3 Tissues in Action Notes)

Living organisms are made up of millions or even billions of cells. In multicellular organisms, similar cells group together to perform a specific function. Such groups of similar cells are called tissues.

The specialization of cells into tissues makes the functioning of organisms more efficient. Instead of every cell performing every function, different tissues perform different tasks. This concept is known as the division of labour.

Plants and animals have different types of tissues because they have different lifestyles and requirements. Plant tissues mainly provide support, transport, storage, and growth, whereas animal tissues help in movement, coordination, protection, and transport of substances.

This chapter explains the structure, classification, characteristics, and functions of plant and animal tissues in detail.

These notes are prepared according to the latest NCERT Exploration: Textbook of Science for Grade 9 and cover all important concepts in an easy-to-understand format.

Learning Objectives

After studying this chapter, you will be able to:

• Define tissue and explain its importance.
• Understand why multicellular organisms require tissues.
• Differentiate between plant tissues and animal tissues.
• Classify plant tissues into meristematic and permanent tissues.
• Classify animal tissues into epithelial, connective, muscular, and nervous tissues.
• Explain the structure and functions of different tissues.
• Understand the concept of division of labour.
• Identify tissues in plants and animals using diagrams.

What is a Tissue?

Definition

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

The cells of a tissue have similar structures and cooperate to perform a particular job.

Examples of Tissues

Plant Tissues

• Xylem
• Phloem
• Parenchyma
• Collenchyma
• Sclerenchyma

Animal Tissues

• Blood
• Bone
• Muscle
• Nerve
• Skin Epithelium

Why Do Organisms Need Tissues?

Single-celled organisms like Amoeba perform all life processes within one cell. However, multicellular organisms contain millions of cells.

If every cell performed every function, the body would not work efficiently.

Therefore, cells specialize into tissues.

Advantages of Tissues

Tissues provide several benefits:

• Division of labour
• Greater efficiency
• Better coordination
• Faster growth
• Improved repair of damaged parts
• Ability to perform complex functions

Division of Labour

Division of labour means that different tissues perform different functions.

Examples

• Muscle tissue helps in movement.
• Nervous tissue carries messages.
• Blood transports oxygen and nutrients.
• Xylem transports water.
• Phloem transports food.

Because each tissue performs a specialized function, the organism works more efficiently.

Difference Between Cell and Tissue

Types of Tissues

Tissues are broadly classified into two groups.

1. Plant Tissues

Found only in plants.

Functions include:

• Growth
• Support
• Food storage
• Transport of water
• Transport of food

2. Animal Tissues

Found only in animals.

Functions include:

• Protection
• Movement
• Transport
• Coordination
• Support

Plant Tissues

Plant tissues are divided into two major groups.

1. Meristematic Tissue

Responsible for plant growth.

Cells divide continuously.

2. Permanent Tissue

Formed from meristematic tissue.

Cells lose the ability to divide and perform specialized functions.

Animal Tissues

Animal tissues are classified into four major types.

• Epithelial Tissue
• Connective Tissue
• Muscular Tissue
• Nervous Tissue

Each type performs a unique function.

Characteristics of Plant Tissues

• Mostly made of dead cells (except some tissues).
• Provide mechanical support.
• Help in transport.
• Store food and water.
• Growth occurs only in meristematic tissues.

Characteristics of Animal Tissues

• Mostly made of living cells.
• Require more energy.
• Specialized for movement.
• Highly coordinated.
• Support rapid responses.

Plant vs Animal Tissues

Importance of Tissues

Tissues help organisms by:

• Performing specialized functions.
• Improving efficiency.
• Providing strength.
• Helping growth.
• Repairing damaged parts.
• Maintaining body functions.

Everyday Examples

• Skin is made of epithelial tissue.
• Blood transports oxygen throughout the body.
• Bones provide support.
• Muscles help us walk and run.
• Xylem carries water from roots to leaves.
• Phloem transports food from leaves to other plant parts.

Meristematic Tissue

Definition

Meristematic tissue is a group of actively dividing, immature cells that are responsible for the growth of plants.

These tissues are found only in the growing regions of plants.

Characteristics of Meristematic Tissue

Meristematic cells possess several unique characteristics:

• Cells divide continuously.
• Cells are small and spherical.
• Thin primary cell wall.
• Dense cytoplasm.
• Large nucleus.
• Vacuoles are absent or very small.
• Cells are tightly packed.
• No intercellular spaces.
• Living cells.

These characteristics help meristematic cells divide rapidly.

Functions of Meristematic Tissue

Meristematic tissue performs many important functions.

• Increases the length of roots and stems.
• Increases the thickness of stems and roots.
• Produces new leaves and flowers.
• Helps in wound healing.
• Replaces damaged tissues.
• Gives rise to permanent tissues.

Types of Meristematic Tissue

Meristematic tissues are classified on the basis of their location.

There are three types:

• Apical Meristem
• Intercalary Meristem
• Lateral Meristem

1. Apical Meristem

Definition

Apical meristem is present at the tips of roots and shoots.

It is responsible for the increase in the length of the plant.

Location

• Root tip
• Shoot tip

Functions

• Primary growth.
• Formation of new leaves.
• Formation of flowers.
• Increase in plant height.
• Development of young branches.

Example

When a plant grows taller every year, the growth occurs because of the apical meristem.

2. Intercalary Meristem

Definition

Intercalary meristem is present at the base of leaves or between the nodes of stems.

Location

• Base of leaves
• Internodes of grasses
• Bamboo
• Sugarcane

Functions

• Rapid elongation of stems.
• Regrowth after grazing.
• Increase in internode length.

Example

Grass quickly grows again after being cut because of the intercalary meristem.

3. Lateral Meristem

Definition

Lateral meristem is present along the sides of stems and roots.

It is responsible for increasing the thickness of plants.

Location

• Stem
• Root

Functions

• Secondary growth.
• Increase in girth.
• Formation of wood.
• Formation of bark.

Example

The thick trunk of a mango or neem tree develops due to the activity of the lateral meristem.

Comparison of the Three Types of Meristematic Tissue

Permanent Tissue

Cells produced by meristematic tissue gradually mature and lose their ability to divide.

These mature cells become permanent tissues.

Definition

Permanent tissue is a group of mature cells that have lost the ability to divide and perform specific functions.

Characteristics of Permanent Tissue

• Mature cells.
• Cells do not divide.
• Larger vacuoles present.
• Definite shape and size.
• Intercellular spaces may be present.
• Specialized functions.
• Living or dead cells.

Functions of Permanent Tissue

Permanent tissues help in:

• Storage of food.
• Mechanical support.
• Photosynthesis.
• Transport of water.
• Transport of food.
• Protection.

Difference Between Meristematic Tissue and Permanent Tissue

Why Does a Plant Need Both Tissues?

Both tissues are essential for proper growth and survival.

Meristematic Tissue

• Produces new cells.
• Helps the plant grow.

Permanent Tissue

• Performs specialized activities.
• Supports the plant throughout its life.

Together, they ensure continuous growth and efficient functioning.

Everyday Examples

• The increase in the height of a sunflower is due to the apical meristem.
• Grass grows back quickly after mowing because of the intercalary meristem.
• The increasing thickness of a tree trunk each year is due to the lateral meristem.
• Mature leaves perform photosynthesis because they contain permanent tissues.

Simple Permanent Tissue

Definition

Simple permanent tissue is a tissue made up of only one type of similar mature cells that perform the same function.

Simple permanent tissues are of three types:

• Parenchyma
• Collenchyma
• Sclerenchyma

1. Parenchyma

Definition

Parenchyma is a simple permanent tissue made up of living, thin-walled cells.

It is the most common and widely distributed tissue in plants.

Characteristics of Parenchyma

• Living cells.
• Thin cellulose cell wall.
• Large central vacuole.
• Intercellular spaces present.
• Cells are usually oval, spherical, or polygonal.
• Soft tissue.

Location of Parenchyma

Parenchyma is found in:

• Cortex of roots
• Cortex of stems
• Pith
• Fruits
• Leaves
• Seeds

Functions of Parenchyma

Parenchyma performs several important functions.

1. Storage

Stores:

• Food
• Water
• Starch
• Sugars

2. Photosynthesis

Parenchyma containing chloroplasts is called Chlorenchyma.

It prepares food through photosynthesis.

3. Buoyancy

Parenchyma with large air spaces is called Aerenchyma.

It helps aquatic plants float on water.

4. Healing

Helps repair damaged plant tissues.

5. Support

Provides support when cells are fully filled with water (turgid).

Special Types of Parenchyma

Chlorenchyma

Contains chloroplasts.

Function:

• Photosynthesis.

Example:

• Green leaves.

Aerenchyma

Contains large air cavities.

Function:

• Provides buoyancy.
• Facilitates gaseous exchange.

Example:

• Lotus
• Water hyacinth

2. Collenchyma

Definition

Collenchyma is a simple permanent tissue made up of living elongated cells with unevenly thickened corners.

Characteristics of Collenchyma

• Living cells.
• Elongated shape.
• Uneven thickening at corners.
• Very little intercellular space.
• Flexible tissue.

Location of Collenchyma

Found in:

• Leaf stalk (petiole)
• Young stems
• Leaf margins

Functions of Collenchyma

• Provides mechanical support.
• Gives flexibility.
• Prevents tearing of leaves.
• Allows bending without breaking.

Everyday Example

The bending of a young stem without breaking is possible because of collenchyma.

3. Sclerenchyma

Definition

Sclerenchyma is a simple permanent tissue made up of dead cells with very thick, lignified cell walls.

Characteristics of Sclerenchyma

• Dead cells.
• Thick cell walls.
• Walls contain lignin.
• No cytoplasm.
• Very hard tissue.
• No intercellular spaces.

Location of Sclerenchyma

Found in:

• Coconut husk
• Seed coats
• Nuts
• Mature stems
• Around vascular bundles

Functions of Sclerenchyma

• Provides great strength.
• Gives rigidity.
• Protects seeds.
• Supports mature plant parts.

Everyday Example

The hard shell of a coconut is mainly due to sclerenchyma.

Difference Between Parenchyma, Collenchyma and Sclerenchyma

Comparison of Simple Permanent Tissues

Importance of Simple Permanent Tissues

Simple permanent tissues help plants by:

• Storing food and water.
• Preparing food.
• Supporting young stems.
• Providing flexibility.
• Giving mechanical strength.
• Protecting seeds and fruits.

Real-Life Examples

• Potato stores starch in parenchyma cells.
• Green leaves contain chlorenchyma for photosynthesis.
• Lotus floats due to aerenchyma.
• Banana leaf bends because of collenchyma.
• Coconut shell is hard because of sclerenchyma.

Complex Permanent Tissue

Definition

Complex permanent tissue is a tissue made up of different types of cells that work together to perform a common function, mainly the transport of substances in plants.

Types of Complex Permanent Tissues

There are two types:

1. Xylem
2. Phloem

Xylem

Definition

Xylem is a complex permanent tissue responsible for transporting water and dissolved minerals from the roots to the stems, leaves, and other parts of the plant.

It also provides mechanical support to the plant.

Components of Xylem

Xylem is made up of four types of cells:

• Tracheids
• Vessels
• Xylem Fibres
• Xylem Parenchyma

1. Tracheids

Characteristics

• Long and narrow cells.
• Dead at maturity.
• Thick lignified walls.
• Tapering ends.

Function

• Transport water.
• Provide mechanical support.

2. Vessels

Characteristics

• Long tube-like structures.
• Dead cells.
• Thick lignified walls.
• Wider than tracheids.

Function

• Rapid transport of water and minerals.

3. Xylem Parenchyma

Characteristics

• Living cells.
• Thin cell walls.

Function

• Stores food.
• Helps in lateral transport of water.

4. Xylem Fibres

Characteristics

• Dead cells.
• Thick lignified walls.

Function

• Provide strength and mechanical support.

Functions of Xylem

Xylem performs several important functions:

• Transports water from roots to leaves.
• Carries dissolved minerals.
• Provides strength to stems.
• Supports the plant body.

Phloem

Definition

Phloem is a complex permanent tissue responsible for transporting prepared food (sugars) from the leaves to all parts of the plant.

This process is called translocation.

Components of Phloem

Phloem consists of four types of cells:

• Sieve Tubes
• Companion Cells
• Phloem Parenchyma
• Phloem Fibres

1. Sieve Tubes

Characteristics

• Living elongated cells.
• End walls contain pores called sieve plates.
• Lack a nucleus at maturity.

Function

• Transport prepared food.

2. Companion Cells

Characteristics

• Living cells.
• Closely associated with sieve tubes.

Function

• Help sieve tubes in transporting food.

3. Phloem Parenchyma

Characteristics

• Living cells.

Function

• Store food.
• Help in lateral transport of nutrients.

4. Phloem Fibres

Characteristics

• Dead cells.
• Thick walls.

Function

• Provide mechanical strength.

Functions of Phloem

Phloem helps in:

• Transporting food from leaves.
• Supplying nutrients to growing parts.
• Storing food.
• Providing support.

Transportation in Plants

Plants require transportation because different parts perform different functions.

Water and Minerals

• Absorbed by roots.
• Transported upward by xylem.

Food

• Prepared in leaves by photosynthesis.
• Transported to all plant parts by phloem.

Difference Between Xylem and Phloem

Vascular Bundle

The combination of xylem and phloem forms a vascular bundle.

Importance

• Efficient transport of substances.
• Mechanical support.
• Connects roots, stems, and leaves.

Everyday Examples

• Water absorbed by roots reaches the leaves through xylem.
• Sugar produced in leaves is transported to fruits and roots by phloem.
• Tall trees remain upright because xylem provides strength.
• Sweet fruits receive sugars through the phloem.

Comparison of Plant Tissues

Animal Tissues

Definition

Animal tissues are groups of similar cells that work together to perform specific functions such as protection, support, movement, transport, and coordination.

1. Epithelial Tissue

Definition

Epithelial tissue is a protective tissue that covers the outer surface of the body and lines the internal organs and body cavities.

It acts as the first line of defence against injury, infection, and dehydration.

Characteristics of Epithelial Tissue

• Cells are closely packed.
• Very little intercellular space.
• Rest on a basement membrane.
• Can regenerate quickly.
• Mostly living cells.

Functions of Epithelial Tissue

• Protection.
• Absorption.
• Secretion.
• Excretion.
• Filtration.
• Diffusion of gases.

Types of Epithelial Tissue

A. Squamous Epithelium

Characteristics

• Thin and flat cells.
• Forms a smooth lining.

Location

• Lungs (alveoli)
• Blood vessels
• Mouth lining

Function

• Allows rapid diffusion.
• Protects delicate organs.

B. Cuboidal Epithelium

Characteristics

• Cube-shaped cells.

Location

• Kidney tubules
• Salivary glands
• Sweat glands

Function

• Secretion.
• Absorption.

C. Columnar Epithelium

Characteristics

• Tall, pillar-like cells.

Location

• Stomach
• Intestine

Function

• Absorbs nutrients.
• Secretes digestive enzymes and mucus.

D. Ciliated Epithelium

Characteristics

• Cells have tiny hair-like projections called cilia.

Location

• Respiratory tract
• Oviduct (Fallopian tube)

Function

• Moves mucus and dust particles.
• Helps move the ovum towards the uterus.

E. Glandular Epithelium

Characteristics

• Modified epithelial cells.

Function

• Produces and secretes substances such as hormones, enzymes, saliva, sweat, and mucus.

Summary of Epithelial Tissue

2. Connective Tissue

Definition

Connective tissue is a tissue that connects, supports, binds, protects, and transports materials throughout the body.

It is the most abundant tissue in animals.

Characteristics of Connective Tissue

• Cells are widely spaced.
• Matrix is abundant.
• Matrix may be solid, liquid, or semi-solid.
• Provides support and strength.

Types of Connective Tissue

A. Areolar Tissue

Location

• Between skin and muscles.
• Around blood vessels.

Functions

• Binds tissues together.
• Fills empty spaces.
• Supports organs.

B. Adipose Tissue

Location

• Beneath the skin.
• Around kidneys.
• Around the heart.

Functions

• Stores fat.
• Provides insulation.
• Protects organs.

C. Tendons

Connect

Muscle to bone.

Function

• Help in body movement.
• Strong and inelastic.

D. Ligaments

Connect

Bone to bone.

Function

• Hold bones together.
• Flexible and elastic.

E. Cartilage

Location

• Nose
• Ear
• Joints
• Trachea

Functions

• Provides flexibility.
• Reduces friction.
• Supports soft organs.

F. Bone

Characteristics

• Hard tissue.
• Rich in calcium salts.

Functions

• Supports the body.
• Protects internal organs.
• Produces blood cells (bone marrow).
• Stores minerals.

G. Blood

Blood is a fluid connective tissue.

Components

• Plasma
• Red Blood Cells (RBCs)
• White Blood Cells (WBCs)
• Platelets

Functions

• Transports oxygen.
• Carries nutrients.
• Removes wastes.
• Protects against infection.
• Helps in blood clotting.

Difference Between Tendons and Ligaments

Difference Between Bone and Cartilage

Everyday Examples

• Skin is made of epithelial tissue.
• Fat stored under the skin is adipose tissue.
• Bones form the skeleton.
• Cartilage allows the nose and ears to bend without breaking.
• Blood carries oxygen from the lungs to body cells.
• Tendons help you lift objects by connecting muscles to bones.
• Ligaments stabilize the knee and elbow joints.

3. Muscular Tissue

Definition

Muscular tissue is a tissue made up of elongated muscle cells (muscle fibres) that contract and relax to produce movement.

It is responsible for all types of body movements.

Characteristics of Muscular Tissue

• Long and cylindrical cells.
• Contractile in nature.
• Rich in proteins (actin and myosin).
• Well supplied with blood vessels.
• Produce force and movement.

Functions of Muscular Tissue

• Movement of body parts.
• Maintenance of posture.
• Pumping of blood.
• Movement of food through the alimentary canal.
• Production of body heat.

Types of Muscular Tissue

There are three types of muscular tissue.

• Striated Muscle
• Smooth Muscle
• Cardiac Muscle

1. Striated Muscle (Skeletal Muscle)

Definition

Striated muscles are voluntary muscles attached to bones that help in body movement.

They are also called skeletal muscles.

Characteristics

• Long and cylindrical fibres.
• Multinucleate.
• Light and dark bands (striations) present.
• Work under our control.

Location

• Arms
• Legs
• Neck
• Face

Functions

• Walking
• Running
• Writing
• Lifting objects
• Body movements

2. Smooth Muscle (Unstriated Muscle)

Definition

Smooth muscles are involuntary muscles found in the walls of internal organs.

Characteristics

• Spindle-shaped cells.
• Single nucleus.
• No striations.
• Work automatically.

Location

• Stomach
• Intestine
• Urinary bladder
• Blood vessels

Functions

• Movement of food.
• Control of blood flow.
• Emptying of the urinary bladder.
• Digestion.

3. Cardiac Muscle

Definition

Cardiac muscles are involuntary muscles found only in the heart.

They contract continuously throughout life.

Characteristics

• Branched fibres.
• Striated appearance.
• Single nucleus.
• Never become tired.
• Contract rhythmically.

Functions

• Pump blood continuously.
• Maintain blood circulation.
• Supply oxygen and nutrients to the body.

Difference Between Types of Muscles

4. Nervous Tissue

Definition

Nervous tissue is a specialized tissue that receives, processes, and transmits nerve impulses throughout the body.

It forms the brain, spinal cord, and nerves.

Structural Unit of Nervous Tissue

The basic structural and functional unit of nervous tissue is the neuron (nerve cell).

Structure of a Neuron

A neuron consists of:

• Cell body (Cyton)
• Dendrites
• Axon
• Nerve endings

Parts of a Neuron

1. Cell Body (Cyton)

Contains the nucleus and controls the activities of the neuron.

2. Dendrites

Short, branched extensions that receive nerve impulses from receptors or other neurons.

3. Axon

A long fibre that carries nerve impulses away from the cell body.

4. Nerve Endings

Transmit impulses to another neuron, muscle, or gland.

Functions of Nervous Tissue

• Receives stimuli.
• Conducts nerve impulses.
• Controls body activities.
• Coordinates different organs.
• Enables quick responses.
• Helps in thinking, learning, and memory.

Importance of Nervous Tissue

Without nervous tissue:

• Muscles cannot move properly.
• Reflex actions cannot occur.
• The body cannot respond to danger.
• Coordination between organs is lost.

Difference Between Plant and Animal Tissues

Summary of Animal Tissues

Everyday Examples

• Running is possible due to striated muscles.
• Digestion occurs because of smooth muscles in the stomach and intestines.
• The heart beats continuously because of cardiac muscles.
• Touching a hot object and immediately withdrawing the hand is controlled by nervous tissue.
• Riding a bicycle requires coordination between muscles and nerves.

Important Definitions

Tissue

A group of similar cells working together to perform a specific function.

Meristematic Tissue

Actively dividing tissue responsible for plant growth.

Permanent Tissue

Mature tissue that performs specialized functions.

Xylem

Complex permanent tissue that transports water and minerals.

Phloem

Complex permanent tissue that transports food.

Epithelial Tissue

Protective tissue covering body surfaces and organs.

Connective Tissue

Tissue that connects, supports, and transports substances.

Muscular Tissue

Contractile tissue responsible for movement.

Nervous Tissue

Specialized tissue that transmits nerve impulses.

Neuron

The structural and functional unit of the nervous system.

Chapter Summary

• A tissue is a group of similar cells performing a common function.
• Plant tissues are classified into meristematic and permanent tissues.
• Permanent tissues are of two types: simple and complex.
• Parenchyma stores food and performs photosynthesis.
• Collenchyma provides flexible support.
• Sclerenchyma gives strength and rigidity.
• Xylem transports water and minerals.
• Phloem transports food.
• Animal tissues include epithelial, connective, muscular, and nervous tissues.
• Muscular tissue helps in movement.
• Nervous tissue controls and coordinates body activities.

Frequently Asked Questions (FAQs)

1. What is a tissue?

A tissue is a group of similar cells working together to perform a specific function.

2. Why are tissues important?

They provide division of labour, making the functioning of multicellular organisms more efficient.

3. What are the two main types of plant tissues?

• Meristematic tissue
• Permanent tissue

4. Which tissue transports water in plants?

Xylem transports water and minerals.

5. Which tissue transports food in plants?

Phloem transports food prepared during photosynthesis.

6. What are the four types of animal tissues?

• Epithelial
• Connective
• Muscular
• Nervous

7. Which muscle works without our control?

Smooth muscle and cardiac muscle are involuntary muscles.

8. Which muscle is found only in the heart?

Cardiac muscle.

9. What is the structural and functional unit of the nervous system?

The neuron.

10. Which tissue connects muscles to bones?

Tendons connect muscles to bones.

Exam Tips

• Learn the classifications of plant and animal tissues.
• Memorise the functions of parenchyma, collenchyma, and sclerenchyma.
• Remember: Xylem = Water, Phloem = Food.
• Practice the differences between tendons and ligaments.
• Learn the three types of muscular tissue with their locations.
• Understand the structure of a neuron and its parts.
• Draw neat, labelled diagrams of plant tissues, muscle types, and a neuron for better scoring.

Quick Revision

• Tissues are groups of similar cells performing specific functions.
• Meristematic tissues are responsible for plant growth.
• Permanent tissues perform specialized functions.
• Xylem carries water and minerals, while phloem transports food.
• Animal tissues include epithelial, connective, muscular, and nervous tissues.
• Striated muscles are voluntary, smooth muscles are involuntary, and cardiac muscles are found only in the heart.
• Neurons transmit nerve impulses and coordinate body functions.

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FAQ

What is a tissue?

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

What are the two main types of plant tissues?

Meristematic tissue and permanent tissue.

How many types of animal tissues are there?

There are four main types: epithelial, connective, muscular, and nervous tissues.

Are these notes enough for exams?

These notes are useful for quick revision. For complete preparation with NCERT solutions, MCQs, case-based questions, mind maps, and practice papers, the complete eBook is recommended.

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