Notes on TISSUES Chapter 6 of class 9 and Extra Questions

Notes on TISSUES Chapter 6 of class 9 and Extra Questions

In this article, you will get simple and easy-to-understand notes on Tissue Chapter 6 of Class 9.  These notes are written in simple language to help you revise quickly before exams. You will also get a set of extra important questions and answers from the chapter to practice well and score better in your exams.

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NCERT Solutions for Class 9 Science Chapter 6 Tissues

What is tissue?

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

Differences Between Plant and Animal Tissues:

Types of Plant Tissues

Plant Tissues are of two types: Meristematic & Permanent tissues.

Meristematic Tissue

In plants, growth takes place only in specific regions. These regions have special tissues called Meristematic Tissues. Meristematic tissues are responsible for the continuous growth of plants by forming new cells at specific regions.

Meristematic Tissues are found at certain points, like tips of roots, stems, and nodes.

Features of Meristematic Tissue:

1. Classification of Meristem: Based on location, meristematic tissues are divided into three types:

1. Apical Meristem: It is present at the tips of roots and stems. It helps in increasing the length of the stem and the root.
2. Lateral Meristem: It is found on the sides of stems and roots. It helps in increasing thickness of the stem or root.
3. Intercalary Meristem: It is located near the nodes in some plants. It helps in the growth of leaves and branches.

2. Characteristics of Meristematic Cells:

• Cells of meristematic tissue are very active.
• These cells have dense cytoplasm, thin cellulose walls, and large nuclei.
• They do not have vacuoles because they focus on division, not storage.
• New cells formed by meristematic tissue later become permanent tissues.

Permanent Tissue

When meristematic cells divide and mature, they lose their ability to divide and become Permanent Tissues.

• Differentiation – The process by which cells of the meristematic tissues convert themselves into permanent tissue by taking a fixed shape, size and function is called differentiation.

• Permanent tissues lose the ability to divide but perform important roles like storage, support, and transport.

Types of Permanent Tissue

Simple Permanent Tissues are of three types:

• Parenchyma
• Collenchyma
• Sclerenchyma

Parenchyma

• Parenchyma is the most common simple permanent tissue in plants.
• This tissue consists of simple cells with thin cell walls.
• They are living cells.
• They are usually loosely arranged, thus large spaces between cells (intercellular spaces) are found in this tissue.
• This tissue generally stores food.
• When parenchyma contains chlorophyll and performs photosynthesis, then it is called chlorenchyma.
• In aquatic plants, large air cavities are present in parenchyma to help them float. Such a parenchyma type is called aerenchyma.

Collenchyma

• Collenchyma provides flexibility in plants.
• It allows bending of various parts of a plant without breaking.
• It also provides mechanical support.
• This tissue is found mainly in leaf stalks below the epidermis.
• The cells of this tissue are living, elongated and irregularly thickened at the corners.
• There is very little intercellular space.

Sclerenchyma

• Sclerenchyma provides strength and stiffness to plants.
• This tissue creates tough materials like coconut husk.
• Sclerenchyma is made of dead cells with very thick walls due to lignin.
• These walls are often so thick that there is no internal space inside the cell.
• Sclerenchyma provides strength to stems, leaf veins, and seed coverings.
• It is present in stems, veins of leaves and in the hard covering of seeds and nuts.

Epidermis

• The outermost layer of the cell is known as the Epidermis.
• It covers the entire plant including roots, stems, leaves, flowers, fruits, and seeds.
• It protects the plant from water loss, injury, and infections.
• It secretes waxy coating on aerial parts of the plant to resist water loss.
• Cells of epidermal tissue form a continuous layer without intercellular spaces.
• Desert plant epidermis develops thick waxy coating of cutin for extra protection.

Stomata:

• Stomata are small pores present in the epidermis of the leaf.
• Each pore has two kidney-shaped cells called guard cells.
• Stomata help in gas exchange (oxygen and carbon dioxide) and transpiration (loss of water as vapour).

Root Hairs:

• Epidermal cells of roots have long hair-like structures.
• They increase the surface area for water and mineral absorption.

Cork:

• As plants grow older, the epidermis of stems is replaced by cork.
• Cork is a protective tissue made of dead cells with a chemical called suberin that makes them waterproof.

Functions of Epidermis

• It protects the plant from physical injury and water loss.
• It prevents the entry of pathogens.
• It helps in gas exchange through stomata.
• It reduces excessive water loss in dry areas using the waxy cutin layer.

Complex Permanent Tissue

• Complex permanent tissues are made of more than one type of cells.
• These cells work together to perform a common function.
• Complex tissues mainly help in the transport of water, minerals, and food in plants.
• Xylem and phloem are examples of such complex tissues.
• Xylem and phloem tissues work as conducting tissues in plants.
• These tissues together form structures called vascular bundles.
• This tissue system made it possible for plants to survive on land.

Types of Complex Permanent Tissue

1. Xylem

• Xylem consists of tracheids, vessels, xylem parenchyma, and xylem fibres.
• Tracheids and vessels transport water and minerals vertically upward.
• Tracheids and vessels have thick walls and are tubular structures.
• Xylem parenchyma stores food and helps in the lateral transport of water.
• Xylem fibres are mainly supportive in function.

2. Phloem

• Phloem consists of sieve tubes, companion cells, phloem parenchyma, and phloem fibres.
• Phloem transports food from leaves to all parts of the plant.
• Sieve tubes are tubular cells with perforated walls.
• Except phloem fibres, other phloem cells are living cells.

Animal Tissues

On the basis of the functions they perform, Animal tissues are divided into four main types: such as

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

Epithelial Tissue

• Epithelial tissues are the primary covering and protective layers in the animal body. They cover most organs and cavities and form the outer layer of the skin.

Where are the epithelial tissues found in the human body?

• Skin
• Lining of the mouth and oesophagus
• Lining of blood vessels
• Lung alveoli
• Kidney tubules
• Lining of the intestine
• Respiratory tract
• Glands

What is Epithelial Tissue?

• Epithelial tissues form the covering or protective tissues in animal bodies.
• They cover most organs and cavities within the body.
• It also forms a barrier to keep different body systems separate from each other.

Structure and Characteristics

• Epithelial cells are tightly packed together and form continuous sheets.
• They have only a small amount of cementing material between them.
• These tissues have almost no intercellular spaces between cells.
• 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 material exchange.
• It controls exchange between the body and external environment and also between different body parts.
• All epithelium is usually separated from underlying tissue by an extracellular fibrous basement membrane.

Functions of Epithelial Tissue

The main functions of epithelial tissue are:

1. It protects the underlying organs and tissues from damage.
2. It forms a barrier between different body parts and the external environment.
3. It allows exchange of gases in the lungs and waste filtration in the kidneys.
4. It absorbs nutrients and water in organs like the intestine.
5. It secretes substances such as sweat, saliva, enzymes, and hormones.

Types of Epithelial Tissues

Simple Squamous Epithelium

• Simple squamous epithelium is a single layer of extremely thin and flat cells that forms a delicate lining.
• It allows transportation of substances.

Where are the Simple Squamous Epithelium found in the human body?

• Skin
• Lining of the mouth and oesophagus
• Lining of blood vessels
• Lung alveoli

What is Stratified Squamous Epithelium?

When epithelial cells are arranged in a pattern of many layers, the epithelium is called stratified squamous epithelium.

Columnar Epithelium

• Columnar epithelium is made up of tall, pillar-like cells arranged in a single layer.
• Location: This tissue is found in the inner lining of the intestine.
• Function: Columnar epithelium helps in absorption and secretion.

Ciliated Columnar Epithelium

• It has hair-like cilia on the outer surfaces of epithelial cells. This type of epithelium is called ciliated columnar epithelium.
• These cilia can move, and their movement pushes mucus forward to clear it.
• It helps keep the respiratory passages clean by moving particles and mucus out.

Cuboidal Epithelium

• Cuboidal epithelium has cube-shaped cells.
• It forms the lining of kidney tubules and ducts of salivary glands.
• This tissue provides mechanical support to these structures.

Glandular Epithelium

• Epithelial cells often acquire additional specialisation as gland cells.
• These gland cells can secrete substances at the epithelial surface.
• This specialised tissue is called glandular epithelium.

Connective Tissue

Connective tissue connects, supports, and binds different parts of the body together. It provides strength, flexibility, and transport in animals. The cells in connective tissue are loosely packed and embedded in an intercellular matrix. The matrix can be jelly like, fluid, dense or rigid depending on the type of connective tissue.

Types of Connective Tissue and Their Functions

1. Blood

• Blood is a fluid (liquid) matrix called plasma.
• Plasma contains red blood cells (RBCs), white blood cells (WBCs), and platelets. It also contains proteins, salts and hormones.
• Blood transports oxygen, food, hormones, and wastes throughout the body.

2. Bone

• Bone forms the framework of the body.
• It supports and protects main organs like the brain, heart, and lungs.
• It is a strong and nonflexible tissue.
• Bone cells are embedded in a hard matrix that is composed of calcium and phosphorus compounds.
• It provides support, protection, and shape to the body.

3. Ligaments

• Ligaments connect bones to bones.
• Ligaments contain very little matrix.
• They are very elastic and provide strength while allowing movement.

4. Tendons

• Tendons connect muscles to bones.
• Tendons are fibrous tissue with great strength but limited flexibility.

5. Cartilage

• Cartilage is a soft and flexible tissue with a solid but smooth matrix.
• The solid matrix is composed of proteins and sugars.
• Cartilage smoothens bone surfaces at joints.
• It is present in the nose, ear, trachea, and larynx.

6. Areolar Tissue

• Areolar tissue is a soft connective tissue found between the skin and muscles, around blood vessels and nerves and in the bone marrow..
• It fills spaces inside organs and helps in tissue repair. It also supports internal organs.

7. Adipose Tissue

• Adipose tissue stores fat in the body.
• It is found beneath the skin and between internal organs.
• It acts as an insulator and provides cushioning.

Muscular Tissue

Muscular tissue helps in movement of different body parts. The cells of muscular tissue are elongated and thread-like and are called muscle fibres. These fibres have special proteins called contractile proteins that can contract and relax to cause movement.

Types of Muscular Tissue

1. Striated Muscles (Voluntary Muscles)

• Striated muscles are also called skeletal muscles as they are mostly attached to bones and help in body movement.
• They appear striped (striated) under a microscope.
• The cells are long, cylindrical, and multinucleated (many nuclei).

2. Smooth Muscles (Involuntary Muscles)

• Smooth muscles are present in alimentary canal, in the iris of the eye, in ureters and in the bronchi of the lungs.
• Their movements are involuntary.
• The cells are spindle-shaped with pointed ends and have a single nucleus.
• These muscles do not have striations (unstriated muscles).

3. Cardiac Muscles

• Cardiac muscles are found only in the heart.
• They are involuntary muscles but never get tired.
• The cells are branched, cylindrical, and have one nucleus.
• They show rhythmic contractions to pump blood throughout life.

Nervous Tissue

Nervous tissue controls and coordinates all the activities of the body. It helps the body to respond quickly to changes in the surroundings. Nervous tissue makes up the brain, spinal cord, and nerves.

Structure of Nervous Tissue

• Nervous tissue is made up of nerve cells, also called neurons.
• Each neuron has three main parts:

1. Cell body – A cell body contains a nucleus and cytoplasm.
2. Dendrites – Dendrites are the short, branched extensions of a neuron that carry messages towards the cell body.
3. Axon – Each neuron has single long part called axon that carries messages away from the cell body to other neurons or muscles.

Functions of Nervous Tissue

• Nervous tissue receives stimuli from the environment.
• It carries messages in the form of electrical signals called nerve impulses.
• It coordinates muscle movements and controls body activities.
• It helps in thinking, memory, and reflex actions.

Important Extra Questions on TISSUES Chapter 7 class 9

1. Define aerenchyma.

Answer: When the cells have air-filled large cavities of parenchyma, it is called aerenchyma. Aerenchyma helps aquatic plants in floating.

2. What is differentiation?

Answer: The process of taking up a permanent shape, size and function by cells is called differentiation.

3. What are guard cells?

Answer: Each stomata is bounded by a pair of specialised kidney-shaped epidermal cells called guard cells

4. Give four differences between bone and cartilage.

Answer:

5. Give the functions of bone.

Answer: 

The main functions of bone are:

1. Bone gives shape and support to the body.
2. It protects vital organs like the brain, heart, and lungs.
3. It helps in movement by acting as a framework for muscles.
4. It stores minerals like calcium and phosphorus.
5. It contains bone marrow that produces blood cells.

6. Give the functions of cartilage. 

Answer: 

• Cartilage smoothens bone surfaces at joints.
• It provides structural support in the nose, ear, trachea, and larynx.
• It allows bending and flexibility.

7. What are the functions of areolar tissue?

Answer: 

• Areolar tissue fills the space inside organs.
• It supports internal organs and holds them in position..
• It helps in repair of tissues after an injury.

8. Give difference between xylem and phloem.

Answer: 

9. Name and give the function of each cell of xylem:

Answer: 

10. Give difference between ligament and tendon.

11. Give difference between striated muscles and unstriated muscles.

Answer:

 12. State the difference between bone and blood.

Answer:

13. Why is blood called connective tissue?

Answer: 

Blood is called connective tissue because it connects different parts of the body by transporting materials between them.

Blood performs its connecting role by transporting oxygen and food to all body cells. At the same time, blood collects waste materials from all parts of the body and carries them to the liver and kidney for disposal.

From a structural perspective, blood has the basic characteristics of connective tissue. Like other connective tissues, blood contains cells that are embedded in an intercellular matrix. In blood, the RBC, WBC, and platelets are suspended in a fluid matrix called plasma, which contains proteins, salts, and hormones.

14. State the difference between simple tissues of plants.

Answer: 

The simple tissues of plants are:
(i) Parenchyma (v) Collenchyma (iii) Sclerenchyma

15. Show the difference between striated muscle fibre, smooth muscle fibre and cardiac muscle fibre.

Answer: 

16. Explain the structure, function and location of nervous tissue.

Answer: 

Structure of Nervous Tissue

• Nervous tissue is made up of specialized cells called neurons.
• Each neuron has a cell body with a nucleus in the center.
• Dendrites are small, branched extensions that receive signals and carry them towards the cell body.
• A long fibre called the axon carries messages away from the cell body to muscles, glands, or other neurons.

Functions of Nervous Tissue

• Nervous tissue receives information from the environment and sense organs.
• It transmits messages in the form of electrical impulses.
• It coordinates body activities and helps in thinking, learning, and memory.
• It controls voluntary and involuntary actions through the brain and spinal cord.

Location of Nervous Tissue

• Nervous tissue is present in the brain, spinal cord, and nerves throughout the body.