Tissues Class 9 Notes are given here for Class 9 students. A living organism is made up of a complex hierarchy of structures.
At the most basic level, we have cells, which are the basic structural and functional units of life.
When a group of these cells, similar in shape and structure, work together to perform a shared specific function, they are known as tissues. Below are the Class 9 Science Chapter 6 Notes for Tissues.
Class 9 Science Chapter 6 Notes Plant Tissues
Plant tissues are categorized based on their ability to divide into two main types: Meristematic and Permanent tissues.
What Is Meristematic Tissue Class 9?
Meristematic Tissue is defined as a specialized group of immature, living cells that possess the extraordinary ability to divide continuously throughout the plant's life.
These tissues are the primary engines of growth, characterized by small, tightly packed cells with thin cellulose walls, very dense cytoplasm, and prominent nuclei. Unlike mature cells, meristematic cells typically lack vacuoles because they are focused on rapid division rather than storage
Key Characteristics of Meristematic Cells:
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Division Power: They have the ability to divide continuously.
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Structure: These are typically small cells with thin cell walls.
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Vacuoles: Generally, vacuoles are absent in these cells.
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Packing: They are very tightly packed with no intercellular spaces.
Types of Meristematic Tissues:
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Apical Meristem: Found at the tips of stems, roots, and leaves. It is responsible for primary growth, helping the plant grow larger.
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Intercalary Meristem: Located at the base of leaves, nodes, or branches. It facilitates growth in these specific regions.
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Lateral Meristem: Found on the lateral sides of roots and shoots. It contributes to secondary growth by increasing the thickness (girth) of the plant.
Permanent Tissues
When meristematic cells lose their ability to divide and take on a permanent shape, size, and function, the process is called differentiation. This results in the formation of permanent tissues.
Simple Permanent Tissues
These are made of only one type of cell:
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Parenchyma: The most basic packing tissue in plants. Cells are alive, thin-walled, and loosely packed with large intercellular (intracellular) spaces. They primarily provide support and store food.
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Collenchyma: It is a living mechanical tissue found in plants. Its primary role is to provide both mechanical support and flexibility (elasticity) to the plant, allowing various parts to bend without breaking.
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Sclerenchyma: It is a simple permanent tissue characterized by its dead, highly thickened cells that provide maximum mechanical strength and rigidity to the plant. These cells are typically long and narrow with cell walls uniformly thickened by the deposition of lignin, a complex chemical substance that acts as a tough cement, making the tissue impermeable to water and extremely hard.
Complex Permanent Tissues
These are defined as tissues made up of more than one type of cell. Unlike simple permanent tissues, these different types of cells work together as a single unit to perform a common function. Their primary role is the transportation of water, minerals, and food throughout the plant body.
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Xylem: It is a complex permanent tissue responsible for the upward conduction of water and minerals from the roots to the leaves. It consists of four different types of cells: Tracheids, Vessels, Xylem Parenchyma, and Xylem Fibres. It forms a continuous channel that reaches all parts of the plant, ensuring a steady supply of water
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Phloem: It is the complex permanent tissue responsible for the translocation of food (mainly sugars) from the leaves (where it is produced) to other parts of the plant, such as roots and growing tips. It is composed of four types of elements: Sieve tubes, Companion cells, Phloem Parenchyma, and Phloem Fibres. Unlike xylem, materials can move in both directions within the phloem.
2. Animal Tissues
Animal tissues are more diverse, catering to the movement and complex physiological needs of animals.
Epithelial Tissue
Epithelial tissues are one of the four primary types of animal tissues, along with connective, muscular, and nervous tissues. They serve as the protective covering of both the internal and external surfaces of the body, as well as the lining of various organs, cavities, and vessels.
The main functions of epithelial tissues include protection, absorption, secretion, and sensation. There are several types of epithelial tissues, each with its own structure and function:
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Subtypes:
Squamous Epithelium: This type of epithelium is composed of thin, flat cells that resemble scales or flattened plates. Squamous epithelial cells are tightly packed and form a smooth, continuous layer.
Cuboidal Epithelium: Cuboidal epithelial cells are cube-shaped with a centrally located nucleus. They line the walls of small ducts and tubules in various glands and organs, including the kidney tubules and salivary glands.
Columnar Epithelium: Columnar epithelial cells are tall and elongated, with their nuclei typically located near the basal surface. They are found in the lining of the gastrointestinal tract (e.g., stomach, small intestine, and large intestine) and parts of the respiratory and reproductive systems.
Transitional Epithelium: Transitional epithelial cells have a variable appearance and can change shape from cuboidal to squamous under tension. This type of epithelium is found in regions of the body subjected to stretching and recoiling, such as the urinary bladder, ureters, and urethra.
Tissue Chapter Class 9 Notes PDF
Tissue Chapter Class 9 Notes PDF provides concise, exam-oriented notes covering all major topics such as plant tissues, animal tissues, meristematic tissue, and permanent tissue. The PDF format makes it easy for students to revise key definitions, diagrams, and differences anytime. This will help students revise the concepts before tests and exams.
Below is the combined Tissue Chapter Class 9 Notes PDF by Physics Wallah. You can download it and revise at your pace:
Tissue Chapter Class 9 Notes PDF
Connective Tissue Class 9
Connective tissues are specialized tissues that bind, support, and connect different organs and structures of the body. Unlike other tissues, their cells are loosely spaced and embedded in an intercellular matrix, which can be fluid, jelly-like, dense, or rigid depending on the specific function of the tissue. They provide the essential structural framework that maintains the body’s integrity. Types Of Connective Tissue Class 9 are given below:
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Fluid Connective Tissue (Blood)
Blood is a unique connective tissue because its matrix is a liquid called plasma. This plasma contains Red Blood Cells (RBCs), White Blood Cells (WBCs), and Platelets. It circulates throughout the body to act as a transport system, carrying oxygen, nutrients, hormones, and waste materials to and from different organs.
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Supportive Connective Tissue (Bone and Cartilage)
This category provides the physical framework for the body. Bone is a hard, non-flexible tissue with a matrix composed of calcium and phosphorus, providing a strong skeleton that anchors muscles. Cartilage, on the other hand, has a solid but flexible matrix made of proteins and sugars; it smoothens bone surfaces at joints and provides structure to the nose, ears, and trachea.
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Fibrous Connective Tissue (Tendons and Ligaments)
These are dense, fibrous tissues responsible for critical connections within the musculoskeletal system. Ligaments are highly elastic and strong tissues that connect bone to bone, ensuring joint stability. Tendons are tougher, less flexible tissues that connect muscles to bones, allowing the skeletal system to move when muscles contract.
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Areolar and Adipose Tissue
These tissues serve as packing and storage materials. Areolar tissue is found between the skin and muscles and around blood vessels; it acts as a "packing tissue" to fill internal spaces and support organs. Adipose tissue is located below the skin and between internal organs; its cells are filled with fat globules, allowing it to store energy and act as an insulator against heat loss.
Muscular Tissues
Muscular Tissues is a specialized tissue responsible for all types of movements in the body. It consists of elongated cells called muscle fibers, which contain special proteins called contractile proteins (actin and myosin) that contract and relax to cause movement.
Based on their structure and control, muscular tissues are classified into three main types:
1. Skeletal Muscle (Striated / Voluntary)
These muscles are mostly attached to bones and help in body movement.
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Structure: The cells are long, cylindrical, unbranched, and have multiple nuclei (multinucleate). They show alternate light and dark bands or "striations" when viewed under a microscope.
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Control: They are voluntary, meaning we can move them according to our conscious will (e.g., moving our hands or legs).
2. Smooth Muscle (Non-striated / Involuntary)
These are found in the walls of internal hollow organs like the stomach, intestines, and blood vessels.
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Structure: The cells are spindle-shaped (tapering ends) and have a single central nucleus (uninucleate). They do not have striations.
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Control: They are involuntary, meaning their movement is not under our conscious control (e.g., the movement of food in the alimentary canal).
3. Cardiac Muscle (Heart Muscle)
As the name suggests, these muscles are found exclusively in the heart.
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Structure: The cells are cylindrical, branched, and uninucleate. They show faint striations.
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Control: They are involuntary and work rhythmically throughout life without getting tired, allowing the heart to pump blood.
Nervous Tissues
Nervous tissue is a specialized type of animal tissue that forms the nervous system, which includes the brain, spinal cord, and peripheral nerves. It plays a fundamental role in coordinating and regulating bodily functions, as well as processing sensory information, generating responses, and maintaining homeostasis.
The main components of nervous tissue are neurons and neuroglial cells (or glial cells), which work together to transmit electrical signals throughout the body and provide support and protection to neurons.
Neurons: Neurons, also known as nerve cells, are the functional units of the nervous system. They are specialized for transmitting electrical impulses, or action potentials, over long distances. Neurons consist of three main parts:
a. Cell Body (Soma): The cell body contains the nucleus and other organelles essential for the neuron's metabolic activities.
b. Axon: The axon is a long, slender projection that extends from the cell body and conducts electrical impulses away from the cell body to other neurons, muscles, or glands.
c. Axon Terminals: At the end of the axon, specialized structures called axon terminals or synaptic terminals transmit signals to other neurons or target cells through synapses, which are junctions between neurons.