Tissues Class 9 Free Notes and Mind Map (Free PDF Download)

This chapter explains the concept of tissues, the difference between plant and animal tissues, various types of plant tissues (meristematic and permanent tissues including simple and complex), different types of animal tissues (epithelial, connective, muscular, and nervous), and their structure, location, and functions. Understanding tissues helps us learn how multicellular organisms achieve division of labour and perform complex functions efficiently.

Introduction

All living organisms are made of cells. In unicellular organisms, a single cell performs all basic functions like movement, intake of food, gaseous exchange, and excretion. But in multicellular organisms, there are millions of cells. Most of these cells are specialised to carry out specific functions. Each specialised function is taken up by a different group of cells. Since these cells carry out only a particular function, they do it very efficiently.

In human beings, muscle cells contract and relax to cause movement, nerve cells carry messages, blood flows to transport oxygen, food, hormones and waste material. In plants, vascular tissues conduct food and water from one part to other parts. So, multicellular organisms show division of labour. Cells specialising in one function are often grouped together in the body. This cluster of cells is called a tissue, arranged and designed to give the highest possible efficiency of function.

Definition: A group of cells that are similar in structure and/or work together to achieve a particular function forms a tissue.

6.1 Are Plants and Animals Made of Same Types of Tissues?

Let us compare the structure and functions of plants and animals.

Differences Between Plant and Animal Tissues

Plants:

• Plants are stationary or fixed – they don’t move.
• Since they have to be upright, they have a large quantity of supportive tissue.
• The supportive tissue generally has dead cells.
• Growth in plants is limited to certain regions (localised).
• There are some tissues in plants that divide throughout their life (meristematic tissue).

Animals:

• Animals move around in search of food, mates and shelter.
• They consume more energy as compared to plants.
• Most of the tissues they contain are living cells.
• Cell growth in animals is more uniform.
• There is no demarcation of dividing and non-dividing regions in animals.

Based on dividing capacity, plant tissues can be classified as:

1. Growing or meristematic tissue
2. Permanent tissue

The structural organisation of organs and organ systems is far more specialised and localised in complex animals than in plants. This fundamental difference reflects the different modes of life – plants are adapted for a sedentary existence while animals are adapted for active locomotion.

Questions (6.1) and Solutions

Q1. What is a tissue?

Solution:

• A tissue is a group of cells that are similar in structure and/or work together to achieve a particular function.
• Cells in a tissue are organised and designed to perform a specific function with maximum efficiency.
• Examples: Blood, phloem, muscle, etc.

Q2. What is the utility of tissues in multicellular organisms?

Solution:

The utility of tissues in multicellular organisms:

• Division of labour: Different tissues perform different functions, making the organism more efficient.
• Specialisation: Cells in a tissue are specialised for a particular function and perform it very efficiently.
• Organisation: Tissues help in organising cells in a structured manner.
• Higher efficiency: Since specific cells perform specific functions, the overall functioning of the organism becomes more efficient.
• Complex functions: Tissues enable multicellular organisms to perform complex functions that single cells cannot do.

6.2 Plant Tissues

Plant tissues are broadly classified into two main types:

1. Meristematic tissue (growing tissue)
2. Permanent tissue (non-dividing tissue)

6.2.1 MERISTEMATIC TISSUE

The growth of plants occurs only in certain specific regions. This is because the dividing tissue, also known as meristematic tissue, is located only at these points.

Experiment with onion roots:

• Take two onion bulbs in jars with water.
• Observe root growth for a few days.
• On day 4, cut the root tips of one onion by about 1 cm.
• Continue observing both onions for five more days.

Observations:

1. The onion with intact root tips has longer roots because the meristematic tissue at the tips continues to divide.
2. The roots do not continue growing after we remove their tips.
3. The tips stop growing in the cut onion because the meristematic tissue (which divides and produces new cells) has been removed.

Types of Meristematic Tissue

Depending on the region where they are present, meristematic tissues are classified as:

1. Apical Meristem:

• Present at the growing tips of stems and roots.
• Increases the length of the stem and the root.

2. Lateral Meristem (Cambium):

• Increases the girth (thickness) of the stem or root.

3. Intercalary Meristem:

• Located near the node in some plants.

Characteristics of Meristematic Cells

Cells of meristematic tissue are:

• Very active (dividing continuously)
• Have dense cytoplasm
• Have thin cellulose walls
• Have prominent nuclei
• Lack vacuoles (because vacuoles occupy space and meristematic cells need maximum cytoplasm for division)

New cells produced by meristem are initially like those of meristem itself, but as they grow and mature, their characteristics slowly change and they become differentiated as components of other tissues.

6.2.2 PERMANENT TISSUE

What happens to the cells formed by meristematic tissue? They take up a specific role and lose the ability to divide. As a result, they form a permanent tissue.

Differentiation: The process of taking up a permanent shape, size, and a function is called differentiation. Differentiation leads to the development of various types of permanent tissues.

Permanent tissues are of two types:

1. Simple permanent tissue
2. Complex permanent tissue

6.2.2 (i) SIMPLE PERMANENT TISSUE

Simple permanent tissues are made of one type of cells that look similar. A few layers of cells beneath the epidermis are generally simple permanent tissue.

1. Parenchyma

Parenchyma is the most common simple permanent tissue.

Characteristics:

• Consists of relatively unspecialised cells with thin cell walls.
• They are living cells.
• Usually loosely arranged, thus large spaces between cells (intercellular spaces) are found.
• This tissue generally stores food.

Special Types:

Chlorenchyma:

• Contains chlorophyll and performs photosynthesis.

Aerenchyma:

• Found in aquatic plants.
• Has large air cavities to help them float.

2. Collenchyma

Collenchyma provides flexibility in plants.

Characteristics:

• Allows bending of various parts of a plant like tendrils and stems of climbers without breaking.
• Provides mechanical support.
• Found in leaf stalks below the epidermis.
• Cells are living, elongated and irregularly thickened at the corners.
• Very little intercellular space.

3. Sclerenchyma

Sclerenchyma makes the plant hard and stiff.

Characteristics:

• The husk of coconut is made of sclerenchymatous tissue.
• Cells are dead.
• Cells are long and narrow.
• Walls are thickened due to lignin (lignified walls).
• Often these walls are so thick that there is no internal space inside the cell.
• Present in stems, around vascular bundles, in veins of leaves, and in hard covering of seeds and nuts.
• Provides strength to plant parts.

Table: Comparison of Simple Permanent Tissues

Epidermis

Epidermis is the outermost layer of cells in plants.

Characteristics:

• Usually made of a single layer of cells.
• In plants living in very dry habitats, the epidermis may be thicker (protection against water loss).
• Protects all parts of the plant.
• Epidermal cells on aerial parts secrete a waxy, water-resistant layer on their outer surface (aids in protection against water loss, mechanical injury, and invasion by parasitic fungi).
• Cells form a continuous layer without intercellular spaces.
• Most epidermal cells are relatively flat.
• Often their outer and side walls are thicker than the inner wall.

Stomata

Small pores in the epidermis of the leaf are called stomata.

Structure:

• Stomata are enclosed by two kidney-shaped cells called guard cells.

Functions:

• Necessary for exchanging gases with the atmosphere (CO₂ enters for photosynthesis, O₂ released).
• Transpiration (loss of water in the form of water vapour) also takes place through stomata.

Special Adaptations:

• Epidermal cells of roots have long hair-like parts that greatly increase the total absorptive surface area for water absorption.
• In desert plants, epidermis has a thick waxy coating of cutin (waterproof substance) on its outer surface to prevent water loss.

Cork

As plants grow older, the outer protective tissue undergoes certain changes. A strip of secondary meristem located in the cortex forms layers of cells which constitute the cork.

Characteristics of Cork:

• Cells are dead and compactly arranged without intercellular spaces.
• Have a substance called suberin in their walls that makes them impervious to gases and water.
• Provides protection to the plant.

6.2.2 (ii) COMPLEX PERMANENT TISSUE

Complex tissues are made of more than one type of cells. All these cells coordinate to perform a common function.

Examples: Xylem and Phloem (both are conducting tissues and constitute a vascular bundle).

Vascular tissue is a distinctive feature of complex plants that has made possible their survival in the terrestrial environment.

1. Xylem

Xylem conducts water and minerals from roots to other parts of the plant.

Constituents of Xylem:

1. Tracheids:

• Have thick walls.
• Are dead cells when mature.
• Tubular structures.
• Transport water and minerals vertically.

2. Vessels:

• Have thick walls.
• Are dead cells when mature.
• Tubular structures.
• Transport water and minerals vertically.

3. Xylem Parenchyma:

• Living cells.
• Stores food.

4. Xylem Fibres:

• Mainly supportive in function.

2. Phloem

Phloem transports food from leaves to other parts of the plant.

Constituents of Phloem:

1. Sieve Cells and Sieve Tubes:

• Tubular cells with perforated walls.
• Living cells.
• Conduct food materials.

2. Companion Cells:

• Living cells.
• Associated with sieve tubes.

3. Phloem Parenchyma:

• Living cells.
• Storage function.

4. Phloem Fibres:

• Provide mechanical support.
• Only dead cells in phloem.

Note: Except phloem fibres, other phloem cells are living cells.

Questions (6.2) and Solutions

Q1. Name types of simple tissues.

Solution:

The three types of simple permanent tissues are:

1. Parenchyma – for storage and photosynthesis
2. Collenchyma – for flexibility and mechanical support
3. Sclerenchyma – for strength and hardness

Q2. Where is apical meristem found?

Solution:

• Apical meristem is found at the growing tips of stems and roots.
• It is responsible for increasing the length of the stem and the root.

Q3. Which tissue makes up the husk of coconut?

Solution:

• Sclerenchyma tissue makes up the husk of coconut.
• It is a permanent tissue with dead cells having thick, lignified walls.
• It provides strength and hardness to the husk.

Q4. What are the constituents of phloem?

Solution:

The constituents of phloem are:

1. Sieve cells and sieve tubes – tubular cells with perforated walls for conducting food
2. Companion cells – associated with sieve tubes
3. Phloem parenchyma – for storage
4. Phloem fibres – for mechanical support (only dead cells in phloem)

Note: Except phloem fibres, all other phloem cells are living cells.

6.3 Animal Tissues

When we breathe, our chest moves. This movement is caused by specialised muscle cells. The contraction and relaxation of these cells result in movement.

During breathing, we inhale oxygen. It is absorbed in the lungs and transported to all body cells through blood. Blood flows and carries various substances:

• Oxygen and food to all cells
• Wastes from all parts of the body to liver and kidney for disposal

Blood and muscles are both examples of tissues found in our body. Based on the functions they perform, animal tissues are classified as:

1. Epithelial tissue
2. Connective tissue
3. Muscular tissue
4. Nervous tissue

6.3.1 EPITHELIAL TISSUE

The covering or protective tissues in the animal body are epithelial tissues.

Locations:

• Skin (covers the body)
• Lining of mouth
• Lining of blood vessels
• Lung alveoli
• Kidney tubules

Characteristics:

• Epithelial tissue cells are tightly packed and form a continuous sheet.
• Have only a small amount of cementing material between them.
• Almost no intercellular spaces.
• Anything entering or leaving the body must cross at least one layer of epithelium.
• The permeability of epithelial cells plays an important role in regulating exchange of materials.
• All epithelium is usually separated from underlying tissue by an extracellular fibrous basement membrane.

Types of Epithelial Tissue

1. Simple Squamous Epithelium:

• Structure: Extremely thin and flat cells forming a delicate lining (squama = scale).
• Location:
  • Lining of blood vessels
  • Lung alveoli
  • Where transportation of substances occurs through a selectively permeable surface
• Function: Allows easy passage of substances.

Stratified Squamous Epithelium:

• Structure: Many layers of squamous cells to prevent wear and tear.
• Location:
  • Skin (protects the body)
  • Oesophagus
  • Lining of mouth
• Function: Protection against wear and tear.

2. Cuboidal Epithelium:

• Structure: Cells are cube-shaped.
• Location:
  • Lining of kidney tubules
  • Ducts of salivary glands
• Function: Provides mechanical support.

3. Columnar Epithelium:

• Structure: Tall epithelial cells (pillar-like).
• Location:
  • Inner lining of intestine (where absorption and secretion occur)
• Function: Facilitates movement across the epithelial barrier (absorption and secretion).

Ciliated Columnar Epithelium:

• Structure: Columnar cells with cilia (hair-like projections on outer surface).
• Location:
  • Respiratory tract
• Function: Cilia can move, and their movement pushes the mucus forward to clear it.

4. Glandular Epithelium:

• Structure: Epithelial cells acquire specialisation as gland cells.
• Function: Can secrete substances at the epithelial surface.
• Sometimes a portion of epithelial tissue folds inward, and a multicellular gland is formed.

6.3.2 CONNECTIVE TISSUE

Blood is a type of connective tissue. It is called ‘connective’ tissue because it connects different parts of the body.

Characteristics:

• Cells of connective tissue are loosely spaced.
• Cells are embedded in an intercellular matrix.
• The matrix may be jelly-like, fluid, dense or rigid.
• The nature of matrix differs according to the function of the particular connective tissue.

Types of Connective Tissue

1. Blood:

• Matrix: Fluid (liquid) matrix called plasma.
• Components suspended in plasma:
  • Red Blood Corpuscles (RBCs) – transport oxygen
  • White Blood Corpuscles (WBCs) – fight infections
  • Platelets – help in blood clotting
• Contents of plasma: Proteins, salts, hormones
• Function: Flows and transports gases, digested food, hormones, and waste materials to different parts of the body.

2. Bone:

• Structure: Bone cells are embedded in a hard matrix composed of calcium and phosphorus compounds.
• Function:
  • Forms the framework that supports the body
  • Anchors the muscles
  • Supports the main organs of the body
• Property: Strong and non-flexible tissue.

3. Ligament:

• Structure: Very elastic tissue with considerable strength; contains very little matrix.
• Function: Connects bones with bones (e.g., at joints).

4. Tendon:

• Structure: Fibrous tissue with great strength but limited flexibility.
• Function: Connects muscles to bones.

5. Cartilage:

• Structure: Has widely spaced cells; solid matrix composed of proteins and sugars.
• Location:
  • Nose, ear, trachea, larynx
  • Smoothens bone surfaces at joints
• Property: We can fold the cartilage of the ears (flexible), but we cannot bend the bones in our arms (difference in structure).

6. Areolar Connective Tissue:

• Location:
  • Found between skin and muscles
  • Around blood vessels and nerves
  • In the bone marrow
• Function:
  • Fills the space inside the organs
  • Supports internal organs
  • Helps in repair of tissues

7. Adipose Tissue:

• Structure: Cells are filled with fat globules.
• Location:
  • Below the skin
  • Between internal organs
• Function:
  • Storage of fats
  • Acts as an insulator (prevents heat loss)

6.3.3 MUSCULAR TISSUE

Muscular tissue consists of elongated cells, also called muscle fibres. This tissue is responsible for movement in our body.

Muscles contain special proteins called contractile proteins, which contract and relax to cause movement.

Types of Muscular Tissue

1. Striated Muscles (Skeletal Muscles):

Structure:

• Cells are long, cylindrical, unbranched and multinucleate (having many nuclei).
• Show alternate light and dark bands or striations when stained.

Location:

• Mostly attached to bones.

Function:

• Help in body movement.

Control:

• Voluntary muscles – we can move them by conscious will.

2. Smooth Muscles (Involuntary Muscles):

Structure:

• Cells are long with pointed ends (spindle-shaped) and uninucleate (having a single nucleus).
• Do not show striations – hence called unstriated muscles.

Location:

• Alimentary canal (for movement of food)
• Blood vessels (for contraction and relaxation)
• Iris of the eye
• Ureters
• Bronchi of lungs

Function:

• Control involuntary movements (we cannot start or stop them simply by wanting to).

Control:

• Involuntary muscles – not under conscious control.

3. Cardiac Muscles:

Structure:

• Cells are cylindrical, branched and uninucleate.
• Show rhythmic contraction and relaxation throughout life.

Location:

• Heart

Function:

• Cause pumping of blood (heart beats).

Control:

• Involuntary muscles – work automatically throughout life.

Table: Comparison of Muscular Tissues

6.3.4 NERVOUS TISSUE

All cells possess the ability to respond to stimuli. However, cells of the nervous tissue are highly specialised for being stimulated and then transmitting the stimulus very rapidly from one place to another within the body.

Composition:

• The brain, spinal cord and nerves are all composed of nervous tissue.
• The cells of this tissue are called nerve cells or neurons.

Structure of a Neuron

A neuron consists of:

1. Cell Body:

• Contains a nucleus and cytoplasm.

2. Axon:

• A single long fibre-like part (process) extending from the cell body.

3. Dendrites:

• Many short, branched parts (processes).

Size: An individual nerve cell may be up to a metre long.

Nerve: Many nerve fibres bound together by connective tissue make up a nerve.

Function of Nervous Tissue

Nerve Impulse:

• The signal that passes along the nerve fibre is called a nerve impulse.
• The nerve impulse from the nerve endings is transmitted to the dendrites of the next nerve cell.

Functions:

• Nerve impulses allow us to move our muscles when we want to.
• The functional combination of nerve and muscle tissue is fundamental to most animals.
• This combination enables animals to move rapidly in response to stimuli.

Questions (6.3) and Solutions

Q1. Name the tissue responsible for movement in our body.

Solution:

• Muscular tissue is responsible for movement in our body.
• It consists of elongated cells called muscle fibres.
• Muscles contain contractile proteins that contract and relax to cause movement.

Q2. What does a neuron look like?

Solution:

A neuron looks like:

• It has a cell body with a nucleus and cytoplasm.
• From the cell body, long thin hair-like parts arise.
• There is usually a single long fibre called the axon.
• There are many short, branched parts called dendrites.
• The axon can be up to a metre long.
• It resembles a tree with branches (dendrites) and a long root (axon).

Q3. Give three features of cardiac muscles.

Solution:

Three features of cardiac muscles are:

1. Structure: Cells are cylindrical, branched and uninucleate (one nucleus per cell).
2. Striations: Show striations (like skeletal muscles).
3. Control: They are involuntary muscles that show rhythmic contraction and relaxation throughout life without conscious control.
4. Location: Found only in the heart.
5. Function: Responsible for pumping blood throughout the body.

Q4. What are the functions of areolar tissue?

Solution:

Functions of areolar tissue:

1. Fills the space inside the organs.
2. Provides support to internal organs.
3. Helps in repair of tissues.
4. Acts as a packing material between skin and muscles.
5. Found around blood vessels and nerves, providing cushioning and support.

End-of-Chapter Exercises – Questions and Solutions

Q1. Define the term “tissue”.

Solution:

• A tissue is a group of cells that are similar in structure and/or work together to achieve a particular function.
• The cells in a tissue are organised in a specific manner to perform a common function with maximum efficiency.
• Examples: Blood, muscle, phloem, nervous tissue.

Q2. How many types of elements together make up the xylem tissue? Name them.

Solution:

Four types of elements make up the xylem tissue:

1. Tracheids – dead tubular cells for water transport
2. Vessels – dead tubular cells for water transport
3. Xylem parenchyma – living cells for storage
4. Xylem fibres – for mechanical support

Q3. How are simple tissues different from complex tissues in plants?

Solution:

Q4. Differentiate between parenchyma, collenchyma and sclerenchyma on the basis of their cell wall.

Solution:

Q5. What are the functions of the stomata?

Solution:

Functions of stomata:

1. Exchange of gases – Carbon dioxide enters for photosynthesis, and oxygen is released.
2. Transpiration – Loss of water in the form of water vapour takes place through stomata.
3. Stomata are controlled by guard cells which open and close the pores according to the plant’s needs.

Q6. Diagrammatically show the difference between the three types of muscle fibres.

Solution:

Diagram should show:

Striated Muscle:

• Long, cylindrical, unbranched cells
• Multiple nuclei at periphery
• Clear striations (light and dark bands)

Smooth Muscle:

• Spindle-shaped (pointed ends) cells
• Single nucleus in center
• No striations (smooth appearance)

Cardiac Muscle:

• Cylindrical, branched cells
• Single nucleus in center
• Striations present
• Cells connected end to end

Q7. What is the specific function of the cardiac muscle?

Solution:

Specific function of cardiac muscle:

• Cardiac muscle is responsible for rhythmic contraction and relaxation of the heart.
• It causes pumping of blood throughout the body.
• It works continuously throughout life without tiring.
• It is an involuntary muscle – works automatically without conscious control.

Q8. Differentiate between striated, unstriated and cardiac muscles on the basis of their structure and site/location in the body.

Solution:

Q9. Draw a labelled diagram of a neuron.

Solution:

Diagram should show:

• Cell body with nucleus
• Dendrites (many short, branched parts)
• Axon (single long fibre)
• Nerve ending (at the end of axon)
• Labels for each part

Q10. Name the following:

(a) Tissue that forms the inner lining of our mouth.

Solution: Squamous epithelium (stratified squamous epithelium)

(b) Tissue that connects muscle to bone in humans.

Solution: Tendon

(c) Tissue that transports food in plants.

Solution: Phloem

(d) Tissue that stores fat in our body.

Solution: Adipose tissue

(e) Connective tissue with a fluid matrix.

Solution: Blood

(f) Tissue present in the brain.

Solution: Nervous tissue

Q11. Identify the type of tissue in the following: skin, bark of tree, bone, lining of kidney tubule, vascular bundle.

Solution:

Q12. Name the regions in which parenchyma tissue is present.

Solution:

Parenchyma tissue is present in:

1. Throughout the plant body – beneath the epidermis
2. Leaves – in the mesophyll (chlorenchyma for photosynthesis)
3. Stems and roots – for storage of food
4. Fruits – as the soft edible part
5. Pith – in the center of stems
6. Cortex – in stems and roots
7. Aquatic plants – as aerenchyma (with air cavities for floating)

Q13. What is the role of epidermis in plants?

Solution:

Role of epidermis in plants:

1. Protection – Protects all parts of the plant (outer covering).
2. Prevents water loss – Epidermal cells secrete a waxy layer on aerial parts.
3. Prevents mechanical injury – Acts as a barrier.
4. Prevents invasion – Protects against parasitic fungi.
5. Gas exchange – Contains stomata for exchange of gases (CO₂ and O₂).
6. Transpiration – Stomata help in loss of water vapour.
7. Water absorption – Root epidermis has root hairs for increased water absorption.

Q14. How does the cork act as a protective tissue?

Solution:

Cork acts as a protective tissue in the following ways:

1. Dead cells – Cork cells are dead and compactly arranged without intercellular spaces, forming a strong protective layer.
2. Suberin – Cell walls contain suberin, which makes them impervious to gases and water, preventing water loss.
3. Replaces epidermis – In older plants, cork replaces the epidermis as the outer protective layer.
4. Prevents mechanical injury – The compact arrangement protects against physical damage.
5. Prevents infection – Acts as a barrier against pathogens.

Q15. Complete the following chart:

Solution:

text                    Permanent Tissue
                    /              \
            Simple                   Complex
            /  |  \                  /      \
    Parenchyma Collenchyma Sclerenchyma   Xylem   Phloem

Explanation:

• Permanent tissues are divided into Simple and Complex tissues.
• Simple tissues: Parenchyma, Collenchyma, Sclerenchyma (made of one type of cells).
• Complex tissues: Xylem, Phloem (made of more than one type of cells).

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