Class 9 Science NCERT Notes – Chapter 6: Tissues (PDF, MindMap, Q&A, Quizzes)

Chapter 6 (Biology): Tissues – Class 9 NCERT Science Detailed Study Notes.

1. Introduction to Tissues

• Definition: A tissue is a group of cells that are similar in structure and/or work together to achieve a particular function.
• Unicellular vs. Multicellular Organisms:
  • In unicellular organisms (e.g., Amoeba), a single cell performs all basic life functions like movement, food intake, gas exchange, and excretion.
  • In multicellular organisms, millions of specialised cells are grouped into tissues to perform specific functions efficiently. This specialisation is known as division of labour.
• Examples of Tissues and Functions:
  • Human: Muscle cells contract for movement, nerve cells carry messages, and blood transports oxygen, food, hormones, and waste.
  • Plant: Vascular tissues (phloem) conduct food and water.

2. Comparison of Plant and Animal Tissues

There are fundamental differences between plant and animal tissues, reflecting their distinct modes of life.

Feature	Plants	Animals
Mobility	Stationary or fixed.	Mobile; move in search of food, mates, and shelter.
Energy Consumption	Consume less energy.	Consume more energy.
Tissue Type	Have a large quantity of supportive tissue, which often consists of dead cells.	Most tissues are living.
Growth Pattern	Growth is limited to specific regions containing dividing (meristematic) tissues.	Cell growth is more uniform; no distinct demarcation of dividing and non-dividing regions.
Structural Org.	Organ systems are less complex.	Organ and organ systems are far more specialised and localised.
Adaptation	Adapted for a sedentary existence.	Adapted for active locomotion.

3. Plant Tissues

Plant tissues are broadly classified into two main types: meristematic tissue and permanent tissue.

3.1 Meristematic Tissue (Growing Tissue)

This is the dividing tissue found only in the specific growth regions of a plant.

• Characteristics of Cells: Very active, have dense cytoplasm, thin cellulose walls, prominent nuclei, and lack vacuoles.
• Process: New cells produced by the meristem are initially identical, but they mature and undergo differentiation to become components of other tissues.
• Types of Meristematic Tissues:
  • Apical Meristem: Located at the growing tips of stems and roots. It is responsible for the increase in the length of the plant.
  • Lateral Meristem (Cambium): Found along the sides of the stem or root. It is responsible for the increase in the girth (width).
  • Intercalary Meristem: Located near the nodes in some plants.

3.2 Permanent Tissue

These tissues are formed from meristematic cells that have lost the ability to divide and have taken up a permanent shape, size, and function through differentiation.

3.2.1 Simple Permanent Tissue

Composed of only one type of cell.

• Parenchyma:
  • Structure: The most common simple tissue, consisting of unspecialised, living cells with thin walls. Cells are usually loosely arranged, creating large intercellular spaces.
  • Function: Primarily stores food.
  • Specializations:
    • Chlorenchyma: Parenchyma containing chlorophyll that performs photosynthesis.
    • Aerenchyma: Found in aquatic plants, contains large air cavities that provide buoyancy.
• Collenchyma:
  • Structure: Composed of living, elongated cells that are irregularly thickened at the corners, with very little intercellular space.
  • Function: Provides flexibility, allowing plant parts (like tendrils and stems) to bend without breaking. It also provides mechanical support.
  • Location: Found in leaf stalks, below the epidermis.
• Sclerenchyma:
  • Structure: Consists of long, narrow, dead cells with walls thickened by lignin. The walls are often so thick that there is no internal space.
  • Function: Makes the plant hard and stiff, providing strength.
  • Location: Found in stems, around vascular bundles, in the veins of leaves, and in the hard covering of seeds and nuts (e.g., husk of a coconut).

3.2.2 Protective Tissue

• Epidermis:
  • Structure: The outermost layer of a plant, usually a single layer of cells. Cells form a continuous layer without intercellular spaces.
  • Function: Protects all parts of the plant from water loss, mechanical injury, and invasion by parasitic fungi.
  • Specializations:
    • Cuticle: A waxy, water-resistant layer secreted by epidermal cells on aerial parts to prevent water loss.
    • Stomata: Small pores on the leaf epidermis, each enclosed by two kidney-shaped guard cells. They are essential for gas exchange and transpiration (water loss as vapour).
    • Root Hairs: Long, hair-like extensions of epidermal cells in roots that increase the surface area for water absorption.
    • Cutin: In desert plants, the epidermis has a thick waxy coating of cutin for enhanced water-proofing.
• Cork:
  • Structure: As plants age, a strip of secondary meristem forms layers of cork cells. These cells are dead, compactly arranged without intercellular spaces, and have suberin in their walls.
  • Function: Suberin makes the cells impervious to gases and water, providing protection.

3.2.3 Complex Permanent Tissue

Composed of more than one type of cell, all coordinating to perform a common function. They are conducting tissues.

• Vascular Bundle: A structure constituted by xylem and phloem. Vascular tissue is essential for the survival of complex plants in terrestrial environments.
• Xylem:
  • Function: Transports water and minerals vertically from roots to other parts of the plant.
  • Constituents (Elements):
    • Tracheids and Vessels: Tubular structures with thick walls; many are dead cells. They form the primary water-conducting channels.
    • Xylem Parenchyma: Stores food.
    • Xylem Fibres: Primarily supportive in function.
• Phloem:
  • Function: Transports food from leaves to other parts of the plant.
  • Constituents (Elements):
    • Sieve Tubes: Tubular cells with perforated walls.
    • Companion Cells
    • Phloem Fibres: The only dead cells in phloem.
    • Phloem Parenchyma
    • (Note: Sieve cells are also listed as a component). All phloem cells are living except for phloem fibres.

4. Animal Tissues

Animal tissues are classified into four main types based on their function.

4.1 Epithelial Tissue

• Function: Acts as a covering or protective tissue. It covers most organs and cavities and forms a barrier to keep different body systems separate.
• Structure: Cells are tightly packed to form a continuous sheet with almost no intercellular spaces and a small amount of cementing material. All epithelium is separated from the underlying tissue by an extracellular fibrous basement membrane.
• Types of Epithelial Tissues:
  • Simple Squamous Epithelium: A single layer of extremely thin, flat cells forming a delicate lining. Found where transportation occurs through a selectively permeable surface, such as in blood vessels and lung alveoli. Also lines the mouth and oesophagus.
  • Stratified Squamous Epithelium: Cells are arranged in many layers to prevent wear and tear. This forms the skin.
  • Columnar Epithelium: Tall, pillar-like cells found where absorption and secretion occur, such as the inner lining of the intestine. Facilitates movement across the epithelial barrier.
  • Ciliated Columnar Epithelium: Columnar epithelium with cilia (hair-like projections) on the outer surface. The movement of cilia pushes mucus forward to clear it. Found in the respiratory tract.
  • Cuboidal Epithelium: Cube-shaped cells that provide mechanical support. Forms the lining of kidney tubules and ducts of salivary glands.
  • Glandular Epithelium: Epithelial cells specialised to secrete substances. Sometimes a portion of the tissue folds inward to form a multicellular gland.

4.2 Connective Tissue

• Structure: The cells are loosely spaced and embedded in an intercellular matrix, which can be jelly-like, fluid, dense, or rigid. The nature of the matrix defines the tissue’s function.
• Types of Connective Tissues:
  • Blood: Has a fluid matrix called plasma, which contains proteins, salts, and hormones. Red blood corpuscles (RBCs), white blood corpuscles (WBCs), and platelets are suspended in the plasma. It transports gases, digested food, hormones, and waste.
  • Bone: A strong, nonflexible tissue with a hard matrix composed of calcium and phosphorus compounds. It forms the body’s framework, supports main organs, and anchors muscles.
  • Ligament: A very elastic tissue with considerable strength that connects bone to bone. Contains very little matrix.
  • Tendon: A fibrous tissue with great strength but limited flexibility that connects muscle to bone.
  • Cartilage: Has widely spaced cells in a solid matrix of proteins and sugars. It smoothens bone surfaces at joints and is found in the nose, ear, trachea, and larynx.
  • Areolar Tissue: Fills the space inside organs, supports internal organs, and helps in tissue repair. Found between the skin and muscles, around blood vessels and nerves, and in the bone marrow.
  • Adipose Tissue: A fat-storing tissue found below the skin and between internal organs. The cells are filled with fat globules. It also acts as an insulator.

4.3 Muscular Tissue

• Function: Responsible for movement in the body.
• Structure: Consists of elongated cells called muscle fibres, which contain special contractile proteins that contract and relax to cause movement.
• Types of Muscular Tissues:
  • Striated Muscle (Voluntary or Skeletal Muscle):
    • Control: Can be moved by conscious will.
    • Location: Mostly attached to bones, helping in body movement.
    • Structure: Cells are long, cylindrical, unbranched, and multinucleate (have many nuclei). They show alternate light and dark bands or striations.
  • Smooth Muscle (Unstriated or Involuntary Muscle):
    • Control: Controls movements that are not under conscious control.
    • Location: Found in the iris of the eye, ureters, bronchi of the lungs, alimentary canal, and blood vessels.
    • Structure: Cells are long with pointed ends (spindle-shaped) and uninucleate (have a single nucleus). They lack striations.
  • Cardiac Muscle (Involuntary Muscle):
    • Control: Involuntary; shows rhythmic contraction and relaxation throughout life.
    • Location: Found only in the heart.
    • Structure: Cells are cylindrical, branched, and uninucleate. They show striations.

4.4 Nervous Tissue

• Function: Cells are highly specialised for being stimulated and transmitting the stimulus (nerve impulse) very rapidly within the body.
• Location: Composes the brain, spinal cord, and nerves.
• Structure (Neuron): The cells of nervous tissue are called neurons or nerve cells. A neuron consists of:
  • Cell Body: Contains a nucleus and cytoplasm.
  • Dendrites: Many short, branched, hair-like parts arising from the cell body.
  • Axon: A single long, fiber-like part.
  • A nerve is formed by many nerve fibres bound together by connective tissue.

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Q&A Section

Short-Answer Questions (2-3 sentences each)

1. What is a tissue, and why is it important in multicellular organisms?
2. Explain the concept of “division of labour” using examples from both plants and animals.
3. Describe two key differences in the growth patterns of plants and animals.
4. What are the three types of meristematic tissues in plants, and where are they located?
5. What are the main characteristics of cells found in meristematic tissue?
6. Explain the process of differentiation in plant tissues.
7. Compare the cell walls and intercellular spaces of parenchyma and collenchyma.
8. What is sclerenchyma, and how does its structure contribute to its function? Give an example of where it is found.
9. Describe the structure and function of the plant epidermis.
10. What are stomata, and what two major functions do they perform for the plant?
11. How does cork tissue provide protection for older plants?
12. Differentiate between simple and complex permanent tissues in plants.
13. What are the four types of elements that make up xylem tissue?
14. Name the constituents of phloem and identify which of them are living cells.
15. What is epithelial tissue and what is its primary role in the animal body?
16. Describe the structure and location of stratified squamous epithelium.
17. Explain the function of cilia in ciliated columnar epithelium and state where this tissue is found.
18. What is the defining characteristic of connective tissue, and what forms can its matrix take?
19. Compare the functions and properties of ligaments and tendons.
20. What is adipose tissue, and what are its two main functions?
21. What are contractile proteins and what is their role in muscular tissue?
22. Differentiate between voluntary and involuntary muscles, giving an example of each.
23. Describe the three main structural features of cardiac muscle cells.
24. What are the three main parts of a neuron?
25. Explain how the functional combination of nerve and muscle tissue is fundamental to most animals.

Multiple Choice Questions (MCQs)

1. Which tissue is responsible for increasing the girth of a plant’s stem?
   • a) Apical meristem b) Intercalary meristem c) Lateral meristem d) Phloem
2. Parenchyma that contains chlorophyll and performs photosynthesis is called:
   • a) Aerenchyma b) Chlorenchyma c) Collenchyma d) Sclerenchyma
3. The husk of a coconut is made of which type of tissue? a) Parenchyma b) Collenchyma c) Sclerenchyma d) Epidermis
4. The transport of food from leaves to other parts of the plant is carried out by:
   • a) Xylem b) Phloem c) Cambium d) Cork
5. Which of the following is NOT a component of xylem?
   • a) Tracheids b) Vessels c) Companion cells d) Xylem fibres
6. The outer protective layer of a plant is primarily formed by:
   • a) Collenchyma b) Vascular tissue c) Epidermis d) Endodermis
7. Which type of animal tissue forms the lining of blood vessels and lung alveoli?
   • a) Cuboidal epithelium b) Simple squamous epithelium c) Columnar epithelium d) Stratified squamous epithelium
8. The connective tissue that connects muscles to bones is called:
   • a) Ligament b) Tendon c) Cartilage d) Areolar tissue
9. Blood is a type of connective tissue because it has:
   • a) Tightly packed cells b) Contractile proteins c) A fluid matrix called plasma d) A hard, rigid matrix
10. Which type of muscle tissue is characterized by being cylindrical, branched, and uninucleate?
    • a) Striated muscle b) Smooth muscle c) Cardiac muscle d) Voluntary muscle
11. Cells of this tissue are dead, long, narrow, and have walls thickened by lignin.
    • a) Parenchyma b) Sclerenchyma c) Collenchyma d) Phloem
12. Areolar tissue is found:
    • a) Only in the heart b) As the hard covering of nuts c) Between the skin and muscles d) Forming the surface of the skin
13. A neuron consists of a cell body, axon, and:
    • a) Cilia b) Striations c) Dendrites d) Fat globules
14. Fat is stored in the human body as:
    • a) Areolar tissue b) Adipose tissue c) Cartilage d) Cuboidal epithelium
15. Rhythmic contraction and relaxation throughout life is a specific function of:
    • a) Voluntary muscle b) Unstriated muscle c) Cardiac muscle d) Skeletal muscle
16. The substance present in the walls of cork cells that makes them impervious to gases and water is:
    • a) Lignin b) Suberin c) Cutin d) Cellulose
17. Which of the following animal tissues is composed of tightly packed cells forming a continuous sheet?
    • a) Connective tissue b) Muscular tissue c) Nervous tissue d) Epithelial tissue
18. Involuntary muscles without striations are:
    • a) Skeletal muscles b) Cardiac muscles c) Smooth muscles d) Voluntary muscles
19. Which plant tissue provides flexibility, allowing parts like tendrils to bend without breaking?
    • a) Sclerenchyma b) Collenchyma c) Parenchyma d) Xylem
20. A group of cells similar in structure that work together to achieve a particular function is called a(n):
    • a) Organ b) Organism c) Tissue d) Organ system

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Answer Keys

Answer Key: Short-Answer Questions

1. A tissue is a cluster of cells similar in structure and function, working together. Tissues are vital in multicellular organisms because they allow for specialization and a division of labour, where different cell groups perform specific tasks with high efficiency.
2. Division of labour is the specialization of cells to carry out specific functions efficiently. In plants, vascular tissues like phloem conduct food. In animals, muscle cells contract for movement while nerve cells transmit messages.
3. Plant growth is restricted to specific regions called meristems, which divide throughout the plant’s life. In contrast, animal cell growth is more uniform throughout the body and is not confined to specific dividing regions.
4. The three types of meristematic tissues are apical, lateral, and intercalary. Apical meristem is found at the tips of stems and roots, lateral meristem is along the sides of the stem, and intercalary meristem is located near the nodes.
5. Cells in meristematic tissue are very active, with dense cytoplasm, prominent nuclei, and thin cellulose walls. They characteristically lack vacuoles, which would otherwise be filled with cell sap and hinder active division.
6. Differentiation is the process by which cells formed by meristematic tissue take up a permanent shape, size, and a specific function. This process leads to the development of various permanent tissues as the cells lose their ability to divide.
7. Parenchyma cells have thin cell walls and are loosely arranged, resulting in large intercellular spaces. Collenchyma cells have cell walls that are irregularly thickened at the corners and have very little intercellular space.
8. Sclerenchyma is a supportive tissue composed of dead cells with walls heavily thickened by lignin. This structure makes the plant hard and stiff, providing strength. It is found in the husk of a coconut.
9. The epidermis is the single, outermost layer of cells covering a plant. It acts as a protective barrier against water loss, mechanical injury, and fungal invasion by forming a continuous sheet.
10. Stomata are small pores in the leaf epidermis, enclosed by guard cells. They are necessary for exchanging gases (like carbon dioxide and oxygen) with the atmosphere and for transpiration, which is the loss of water in the form of water vapour.
11. Cork tissue is composed of dead, compactly arranged cells whose walls contain a chemical called suberin. Suberin makes the cells impervious to gases and water, forming a protective outer layer on older stems.
12. Simple permanent tissues, such as parenchyma, are made of only one type of cell. Complex permanent tissues, like xylem and phloem, are made of more than one type of cell that coordinate to perform a common function.
13. Xylem tissue is made up of four types of elements: tracheids, vessels, xylem parenchyma, and xylem fibres.
14. Phloem is constituted by sieve cells, sieve tubes, companion cells, phloem fibres, and phloem parenchyma. Except for the phloem fibres, all other phloem cells are living.
15. Epithelial tissue is the covering or protective tissue in the animal body. Its primary role is to cover most organs and cavities, forming a barrier that keeps different body systems separate.
16. Stratified squamous epithelium consists of epithelial cells arranged in a pattern of many layers. This layered structure helps prevent wear and tear and is found in the skin, which protects the body.
17. Cilia are hair-like projections on the outer surface of columnar epithelial cells. Their movement pushes mucus forward to clear it from passages. This tissue is found in the respiratory tract.
18. The defining characteristic of connective tissue is that its cells are loosely spaced and embedded in an intercellular matrix. This matrix can be jelly-like, fluid, dense, or rigid, depending on the tissue’s function.
19. Ligaments connect bone to bone and are very elastic with considerable strength. Tendons connect muscle to bone; they have great strength but are fibrous with limited flexibility.
20. Adipose tissue is a fat-storing connective tissue found below the skin and between internal organs. Its two main functions are storing energy in the form of fat and acting as an insulator for the body.
21. Contractile proteins are special proteins found within muscle cells (muscle fibres). They have the ability to contract and relax, which is the mechanism that causes movement in the body.
22. Voluntary muscles, like the striated muscles in our limbs, can be moved by conscious will. Involuntary muscles, like the smooth muscles in the alimentary canal, cannot be started or stopped simply by wanting to do so.
23. Cardiac muscle cells are cylindrical in shape, branched, and uninucleate (containing a single nucleus).
24. A neuron consists of a cell body (containing the nucleus and cytoplasm), dendrites (short, branched processes), and an axon (a single, long process).
25. The functional combination of nerve and muscle tissue is fundamental because nervous tissue rapidly transmits stimuli (nerve impulses), which allows muscle tissue to contract and produce movement. This combination enables animals to move rapidly in response to stimuli.

Answer Key: MCQs

1. c) Lateral meristem
2. b) Chlorenchyma
3. c) Sclerenchyma
4. b) Phloem
5. c) Companion cells
6. c) Epidermis
7. b) Simple squamous epithelium
8. b) Tendon
9. c) A fluid matrix called plasma
10. c) Cardiac muscle
11. b) Sclerenchyma
12. c) Between the skin and muscles
13. c) Dendrites
14. b) Adipose tissue
15. c) Cardiac muscle
16. b) Suberin
17. d) Epithelial tissue
18. c) Smooth muscles
19. b) Collenchyma
20. c) Tissue

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Essay Questions & Answers

1. Describe the key differences between plant and animal tissues, relating these differences to the organisms’ overall lifestyle and functions.
   • Answer: Plant and animal tissues exhibit fundamental differences that reflect their distinct modes of life. Plants are stationary, leading to a structure dominated by supportive tissues, many of which (like sclerenchyma) are composed of dead cells to provide rigid support. Animals, being mobile, require tissues that facilitate movement and have higher energy consumption; consequently, most of their tissues are living. Growth in plants is localized to specific dividing regions called meristems, whereas animal growth is more uniform. This reflects the plant’s need to grow towards resources like light, while animals develop more symmetrically. Finally, the organ systems in complex animals are far more specialized and localized than in plants, a difference driven by animals’ active lifestyles, complex feeding methods, and the need for rapid response to environmental stimuli.
2. Explain the classification of plant tissues into meristematic and permanent types. Further, describe the sub-types of meristematic tissue and their specific roles in plant growth.
   • Answer: Plant tissues are classified into two main types based on their dividing capacity. Meristematic tissue is the dividing tissue responsible for plant growth. Permanent tissues are derived from meristematic tissue after the cells lose their ability to divide and take on a specific role, a process called differentiation. Meristematic tissues are classified based on their location and the type of growth they produce:
     • Apical Meristem: Found at the growing tips of stems and roots, it is responsible for primary growth, which is the increase in the length of the plant.
     • Lateral Meristem (Cambium): Located along the sides of the stem and root, it is responsible for secondary growth, which is the increase in the girth or thickness of the plant.
     • Intercalary Meristem: Found at the base of leaves or internodes (near the node), it is responsible for growth in length in those specific areas, particularly in grasses.
3. Compare and contrast the three types of simple permanent tissues in plants: parenchyma, collenchyma, and sclerenchyma. Discuss their structure, cell type (living/dead), and primary functions.
   • Answer: Parenchyma, collenchyma, and sclerenchyma are three types of simple permanent tissues, each with a distinct structure and function.
     • Parenchyma is the most common and is composed of relatively unspecialised living cells with thin walls and large intercellular spaces. Its primary function is food storage, but it can be specialised as chlorenchyma for photosynthesis or aerenchyma for buoyancy.
     • Collenchyma consists of living, elongated cells with cell walls that are irregularly thickened at the corners, and it has very little intercellular space. Its main function is to provide mechanical support combined with flexibility, allowing plant parts like stems and tendrils to bend without breaking.
     • Sclerenchyma is composed of dead, long, and narrow cells with walls that are heavily thickened with a substance called lignin, leaving no internal space. This rigid structure provides significant strength and makes plant parts hard and stiff. It is found in the husk of coconuts and the hard coverings of seeds.
4. Detail the structure and function of complex tissues in plants, specifically xylem and phloem. List the constituent cell types for each.
   • Answer: Complex tissues in plants consist of more than one type of cell that work together to perform a common function, primarily transport. The two complex tissues are xylem and phloem, which together form the vascular bundle.
     • Xylem: Its primary function is to conduct water and minerals from the roots vertically up to the rest of the plant. It also provides mechanical support. Xylem is composed of four elements: tracheids and vessels (tubular, thick-walled dead cells that form the main conducting channels), xylem parenchyma (living cells that store food), and xylem fibres (dead cells that are supportive).
     • Phloem: Its primary function is to transport food, produced during photosynthesis, from the leaves to all other parts of the plant. Phloem is composed of five types of cells: sieve tubes (tubular cells with perforated walls), companion cells, sieve cells, phloem parenchyma, and phloem fibres. With the exception of phloem fibres, all other components of phloem are living cells.
5. Describe the different types of epithelial tissues found in animals. For each type, explain its structure and provide an example of its location and function.
   • Answer: Epithelial tissues are classified based on the shape and arrangement of their cells.
     • Simple Squamous Epithelium: A single layer of thin, flat cells. It forms a delicate lining ideal for the transport of substances. It is found in the lining of blood vessels and lung alveoli.
     • Stratified Squamous Epithelium: Cells are arranged in multiple layers to prevent wear and tear. It forms the protective outer layer of the skin.
     • Columnar Epithelium: Composed of tall, pillar-like cells. It is involved in absorption and secretion and is found lining the intestine.
     • Ciliated Columnar Epithelium: Columnar cells with cilia on their surface. The cilia move to push mucus. It is found in the respiratory tract.
     • Cuboidal Epithelium: Cube-shaped cells that provide mechanical support. It forms the lining of kidney tubules and the ducts of salivary glands.
     • Glandular Epithelium: Epithelial cells specialised to secrete substances. It can fold inwards to form multicellular glands, such as salivary glands.
6. What is connective tissue? Describe five different types of connective tissue, explaining the nature of their matrix and their specific functions in the animal body.
   • Answer: Connective tissue is characterised by cells that are loosely spaced and embedded in an intercellular matrix. The nature of this matrix dictates the tissue’s function.
     • Blood: Has a fluid matrix called plasma. It transports gases, nutrients, hormones, and waste materials throughout the body.
     • Bone: Has a hard, rigid matrix composed of calcium and phosphorus compounds. It forms the body’s framework, anchors muscles, and supports organs.
     • Cartilage: Has a solid matrix made of proteins and sugars. It is flexible and smoothens bone surfaces at joints. It is found in the ear, nose, and trachea.
     • Ligament: A fibrous, elastic tissue with very little matrix. It connects bone to bone and provides stability to joints.
     • Areolar Tissue: Has a jelly-like matrix. It fills spaces between organs, supports internal organs, and aids in tissue repair. It is found between the skin and muscles.
7. Compare and contrast the three types of muscular tissue: striated, smooth, and cardiac. Discuss their structure (shape, nuclei, striations), control (voluntary/involuntary), and location.
   • Answer: Muscular tissues are responsible for movement and are classified into three types:
     • Striated Muscle (Skeletal): These are voluntary muscles, meaning their movement is under conscious control. The cells are long, cylindrical, unbranched, and multinucleate. They show alternate light and dark bands called striations and are attached to bones.
     • Smooth Muscle (Unstriated): These are involuntary muscles. The cells are long and spindle-shaped with pointed ends, and they are uninucleate. They lack striations and are found in the walls of internal organs like the alimentary canal, blood vessels, and iris.
     • Cardiac Muscle: This is an involuntary muscle found only in the heart. Its cells are cylindrical, branched, and uninucleate. Like skeletal muscle, it is striated. It is responsible for the rhythmic contraction and relaxation of the heart throughout life.
8. Explain the protective role of tissues in plants. Discuss the functions of the epidermis and cork in detail.
   • Answer: Protective tissues in plants shield them from the external environment. The primary protective tissue is the epidermis. It is the outermost single layer of cells that covers the entire plant, protecting it from water loss, mechanical injury, and parasitic fungi. Epidermal cells on aerial parts often secrete a waxy, water-resistant cuticle. The epidermis also contains stomata for gas exchange and transpiration. As plants grow older, the outer epidermis is replaced by cork. Cork is formed by a secondary meristem and consists of dead cells that are compactly arranged. The walls of these cells contain a chemical called suberin, which makes them impervious to gases and water, thus providing a durable, protective barrier for older stems and roots.
9. Draw and label a neuron. Describe the function of each labelled part and explain how nerve impulses are transmitted in the body.
   • Answer: (A student would draw a diagram of a neuron here, labelling the cell body, nucleus, dendrites, axon, and nerve ending). A neuron is the basic unit of nervous tissue.
     • The cell body contains the nucleus and cytoplasm and is the main metabolic centre of the cell.
     • Dendrites are short, branched extensions that receive stimuli or nerve impulses from other neurons and transmit them towards the cell body.
     • The axon is a single, long fibre that transmits the nerve impulse away from the cell body to other neurons or to muscle cells. The signal that passes along a nerve fibre is called a nerve impulse. The impulse is transmitted from the nerve endings of one neuron’s axon to the dendrites of the next neuron. This rapid transmission of stimuli allows for quick responses and coordination of body functions, such as moving muscles.
10. Discuss the concept of a vascular bundle in plants. Why is the development of this vascular tissue a distinctive feature that made the survival of complex plants in a terrestrial environment possible?
    • Answer: A vascular bundle is a structural unit in plants composed of the two complex conducting tissues: xylem and phloem. Xylem is responsible for transporting water and minerals from the roots upwards, while phloem transports food from the leaves to where it is needed. The development of this vascular tissue was a crucial adaptation for the survival of complex plants on land. In a terrestrial environment, water and nutrients are primarily in the soil, while the energy source (sunlight) is above ground. A vascular system provides an efficient transport network to move water up to the leaves for photosynthesis and to distribute the resulting food (sugars) down to the roots and other non-photosynthetic parts for energy and growth. This internal plumbing system allowed plants to grow larger, taller, and colonise diverse land habitats far from a constant supply of water.

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Glossary of Key Terms

• Adipose Tissue: A type of connective tissue that stores fat; its cells are filled with fat globules. Acts as an insulator.
• Aerenchyma: A type of parenchyma tissue in aquatic plants with large air cavities to provide buoyancy.
• Apical Meristem: Dividing tissue present at the growing tips of stems and roots, responsible for increasing their length.
• Areolar Tissue: A type of connective tissue that fills the space inside organs, supports internal organs, and helps in tissue repair.
• Axon: The single long part (process) of a neuron that transmits nerve impulses away from the cell body.
• Blood: A type of connective tissue with a fluid matrix (plasma) that transports gases, food, hormones, and waste.
• Bone: A strong and nonflexible connective tissue with a hard matrix that forms the supportive framework of the body.
• Cambium: Another term for lateral meristem, responsible for increasing the girth of the stem or root.
• Cardiac Muscle: Involuntary muscle tissue found only in the heart, characterised by rhythmic contraction and relaxation. Cells are cylindrical, branched, and uninucleate.
• Cartilage: A type of connective tissue with a solid matrix of proteins and sugars that smoothens bone surfaces at joints.
• Chlorenchyma: Parenchyma tissue that contains chlorophyll and performs photosynthesis.
• Cilia: Hair-like projections on the outer surfaces of some epithelial cells.
• Collenchyma: A simple permanent plant tissue that provides flexibility and mechanical support, allowing bending without breaking. Cells are living and irregularly thickened at the corners.
• Complex Tissue: A type of permanent tissue made of more than one type of cell that coordinates to perform a common function (e.g., xylem, phloem).
• Connective Tissue: A major type of animal tissue in which cells are loosely spaced and embedded in an intercellular matrix.
• Contractile Proteins: Special proteins in muscle cells that contract and relax to cause movement.
• Cork: An outer protective tissue in older plants, composed of dead cells with suberin in their walls.
• Cutin: A chemical substance with waterproof quality that forms a thick waxy coating on the epidermis of some desert plants.
• Dendrite: Short, branched, hair-like parts of a neuron that receive stimuli.
• Differentiation: The process by which cells take up a permanent shape, size, and function, losing their ability to divide.
• Epidermis: The outermost layer of cells in a plant, providing protection.
• Epithelial Tissue: The covering or protective tissue in the animal body.
• Guard Cells: Two kidney-shaped cells that enclose a stoma and regulate its opening and closing.
• Intercalary Meristem: Meristematic tissue located near the node in some plants.
• Lateral Meristem: Meristematic tissue responsible for the increase in the girth of the stem or root.
• Ligament: A very elastic connective tissue that connects bone to bone.
• Lignin: A chemical substance that thickens the walls of sclerenchyma cells, making them hard and stiff.
• Matrix: The intercellular substance in which connective tissue cells are embedded.
• Meristematic Tissue: Dividing tissue in plants, located in specific growing regions.
• Muscle Fibre: An elongated cell that makes up muscular tissue.
• Nerve Impulse: The signal that passes along a nerve fibre.
• Nervous Tissue: Highly specialised animal tissue composed of neurons, responsible for transmitting stimuli.
• Neuron: A nerve cell; the basic unit of the nervous tissue.
• Parenchyma: The most common simple permanent tissue in plants, composed of unspecialised living cells, primarily for food storage.
• Permanent Tissue: Plant tissues derived from meristematic tissue that have lost the ability to divide.
• Phloem: A complex plant tissue that transports food from leaves to other parts of the plant.
• Plasma: The fluid (liquid) matrix of blood.
• Sclerenchyma: A simple permanent plant tissue with thick, lignified walls that makes the plant hard and stiff and provides strength. Its cells are dead.
• Simple Tissue: A type of permanent tissue made of only one type of cell.
• Smooth Muscle: Involuntary, unstriated muscle tissue found in the walls of internal organs.
• Stomata: Small pores in the epidermis of a leaf, used for gas exchange and transpiration.
• Striated Muscle: Voluntary muscle tissue, also called skeletal muscle, that is attached to bones and shows alternate light and dark bands (striations).
• Suberin: A substance in the walls of cork cells that makes them impervious to gases and water.
• Tendon: A fibrous connective tissue with great strength but limited flexibility that connects muscle to bone.
• Tissue: A group of cells that are similar in structure and/or work together to achieve a particular function.
• Transpiration: The loss of water from a plant in the form of water vapour, primarily through stomata.
• Vascular Bundle: A structure in plants formed by the conducting tissues, xylem and phloem.
• Xylem: A complex plant tissue that conducts water and minerals from the roots to other parts of the plant.