NCERT Class 9 Science Chapter 6 Notes Tissues- Download PDF Notes

NCERT Class 9 Science Chapter 6 Notes Tissues: The examination of tissues is important in the organization and functioning of multicellular organisms. This chapter in NCERT presents the notion that tissues are collections of analogous cells that function in specific ways. The chapter gives comprehensive information on various types of plant and animal tissues, structures, functions, and roles in the living processes of organisms. NCERT Solutions for Class 9 Science Chapter 5 proves to be beneficial in systematic study by providing concept clarity and increased retention.

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1. NCERT Class 9 Chapter 6 Class Notes
2. Plant Tissues
3. Animal Tissues
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CBSE exam students can use these notes for quick revision. They have definitions, examples, and explanations of key concepts such as meristematic and permanent tissues in plants, epithelial, connective, muscular, and nervous tissues in animals. NCERT Notes for Class 9 Science and NCERT Notes for Class 9 are helpful in systematic study by giving concept clarity and better retention.

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NCERT Class 9 Chapter 6 Class Notes

What is a tissue?

• In unicellular organisms, one single cell performs all the basic functions.
• In multicellular cells, where there are millions of cells, every cell is assigned one particular function to perform.
• As can be seen in human beings, muscle cells are responsible for contraction and relaxation, blood is responsible for the transportation of important materials, and nerve cells are important for transferring messages.
• The chapter explains how it can be concluded that in multicellular organisms there is division of labour.
• A specific set of cells at one location within the body performs one specific function.
• A group of cells that are similar in structure work together to achieve a particular function and form a tissue.

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

• We can get to know whether plant tissues and animal tissues are the same by looking into their structures.
• As we know, plants are stationary; they don’t need to move and to stay upright, they also need supportive tissue that is mostly composed of dead cells,
• whereas when it comes to animals, they are always moving around in search of food, shelter, etc., and that’s why they require more energy as compared to plants because they contain living cells.
• When it comes to dividing, it can be seen that in plants there are certain demarcated areas where growth takes place, and also that growth in plants can take place throughout their lifetime.
• Based on those growth phases, they can be divided into permanent and meristematic tissues as well,
• In animals, growth can take place only within a certain period.
• The growth and the basic difference in their functionality lie in the complexity of plants and animals, as it can be very well observed that animals have much more complex organisation as compared to plants.

Plant Tissues

Meristematic Tissue:

Fig: location of meristematic tissue

• Meristematic Tissues are the tissues that have the capacity to divide. Initially, the cells which are formed after division look the same but gradually, they occupy different structures according to their functions.
• Meristematic tissue is present at some particular, specific sites at the plants; based on that, they can be primary meristematic or secondary meristematic.
• Primary meristematic involves apical merismatic, which is present at the root and shoot tips of the plant and is involved in increasing the length of the plant.
• Intercalary meristematic is present in the form of patches at the nodes of the plant.
• Secondary meristematics, also known as lateral meristematics or cambium, is involved in increasing the girth of a plant. All the cells of the merismatic tissue have thin cell walls and dense cytoplasm.

Permanent Tissue:

Fig: Section of a stem

• After meristematic tissue loses its capacity to divide, it acquires a specific function and forms permanent tissue, and this process is known as differentiation.
• Permanent tissues can be further categorised as simple permanent tissue and complex permanent tissue, where simple permanent tissues are made up of all the same kinds of cells, whereas complex permanent tissues are made up of different kinds of cells.

Simple Permanent Tissue

• Under simple tissue comes parenchyma, which is present below the epidermis of a plant.
• These cells are living and isodiametric in shape, have thin cells, and are loosely arranged to fill the space.
• These have large intercellular spaces between them and provide the function of food storage.
• Sometimes, it contains chloroplasts and thus performs photosynthesis; it’s known as chlorenchyma.
• In aquatic plants, it consists of air spaces that help them to float, and then it is known as aerenchyma.
• Another simple permanent tissue is collenchyma, which provides flexibility and mechanical support to plants.
• It helps the plants bend and present themselves in tendrils and climbers, as well as below the epidermis in leaf stalks.
• These are living cells below the epidermis with irregular thickening around them and comparatively fewer intracellular spaces between their cells.
• Sclerenchyma is also a simple, permanent tissue that provides strength to plants.
• It is present in the dead parts of the plant, as all the cells are dead.
• They are elongated cells with a thick cell wall due to the deposition of lignin.
• The fewer intercellular spaces are present in between the cells, as can be seen in the husk of a coconut.

Fig: (1) Parenchyma (2) Collenchyma (3) Sclerenchyma

• The epidermal cells of the roots perform the function of water absorption.
• They also commonly bear long hair-like parts known as root hairs, these are the ones responsible for a significant increase in overall absorptive surface area.
• The epidermis of some plants, such as desert plants, has a thick waxy covering of cutin on its outer surface, which is a chemical compound with waterproof properties.
• Plants' outer protective tissue undergoes modifications as they get older.
• The cork is made up of layers of cells formed by a strip of secondary meristem found in the cortex.
• The cork cells are dead and grouped tightly with no intercellular gaps between them.
• They also have a material in their walls called suberin, which prevents gases and water from entering.

Complex Permanent Tissue

• As you already know, complex tissues are made up of different kinds of cells. All these cells coordinate together to perform a common function.
• Complex permanent tissue can be further categorised into xylem and phloem, and both are conducting tissues constituting vascular bundles.

Fig: (a),(b) and (c) showing xylem elements and (d) showing sections of Phloem.

• Xylem tissue is made up of tracheids, vessels, xylem fibres, and xylem parenchyma.
• Tracheids and vessels are both tubular structures that are responsible for the transportation of water, whereas xylem parenchyma stores food and xylem fibre provides support to plants.
• Phloem consists of sieve tubes, companion cells, phloem fibre, and phloem parenchyma.
• Except for phloem fibres, all are living cells, and all cells together help in the transportation of food from leaves to other parts of the plant. Sieve tubes have perforated structures known as sieve plates.

Animal Tissues

• If we take the example of the human body, when we breathe, we can feel the lungs being uplifted, which is done by the muscular tissue in our body.
• The oxygen that is collected in the lungs is transported to other parts of the body with the help of blood, which is also responsible for the transport of food and other nutrients from one part of the body to another, as well as the release of waste from our body.

Epithelial Tissue:

• This tissue forms the outermost protective layer of the body and also lines the internal and external parts of the organs.
• It acts as a separation between different organs in the body.
• Epithelial tissue works for the functions of protection, secretion, and absorption.
• Based on its structure and function, epithelium tissue can be classified as simple or compound.

Fig: Different kinds of epithelial cells

• In compound epithelium tissue, multiple layers of epithelial cells are present.

In the case of simple epithelial tissue:

• A simple epithelial tissue that is present in the walls of blood vessels and the air sacs of the lungs is known as squamous epithelium tissue. It forms a diffusion boundary as well.

• A simple epithelial tissue that is present in the ducts of glands and the tubular parts of the nephron in the Kidneys is known as the cuboidal epithelium. The main function of the cuboidal epithelium is secretion and absorption.

• The simple epithelial tissue that is present in the stomach lining and intestine lining is the columnar epithelium. Its main function is secretion and absorption.

• A type of simple epithelial tissue is known as the ciliated epithelium when the columnar or cuboidal cells bear cilia. They are present on the inner surface of hollow organs like bronchioles and fallopian tubes. It functions to move particles or mucus in a specific direction.

• Simple epithelial tissue also includes glandular epithelium. When some of the columnar or cuboidal cells get specialised for secretion, it is known as the glandular epithelium. It is further categorised as exocrine and endocrine glands

Connective Tissue:

• Connective tissues are the tissues that connect the body organs. Cells of these tissues are loosely arranged in a matrix. The nature of the matrix depends upon the function of the tissue.

Fig: Connective Tissue

• Connective tissue can be categorised into three categories. They are loose connective tissue, dense connective tissue, and specialised connective tissue.
• Loose connective tissues consist of Areolar and Adipose tissues. Areolar make the filling between the organs for protection, and adipose tissue stores the food in the form of glycogen.
• Ligaments and tendons come under dense connective tissue. Ligaments and tendons both are fibrous tissues. Ligaments are present between two bones and tendons are present between muscles and bones. This can be remembered by BLB, where B stands for bones and L stands for ligaments. One ligament is present between two bones.
• Under specialised connective tissue, bones, cartilage and blood are present.
• Bones are harder than cartilage because of the presence of a hard matrix that is made up of calcium. The major function of blood is the transportation of energy, gases, hormones, etc. 95 % of blood is plasma that contains RBCs. That is responsible for the transport of oxygen. It contains WBCs for increasing immunity and platelets for clotting purposes.
• Lymph is a part of the blood that contains fewer proteins and fewer RBCs, making it pale in colour. It is used to transport fats.

Muscular Tissue:

• Muscular tissue constitutes 40% of our body and can be classified as skeletal muscular tissue, smooth muscle tissue, and cardiac muscular tissue.

Fig: Muscular tissue

• skeletal muscles are cylindrical, unbranched, multinucleated, striated, and voluntary; that is, they are under our control and are found around the skeleton, for example, biceps.

• Smooth muscles are spindle-shaped, uninucleated, and involuntary; that is, they are not under our control and are striated, They are found in intestine organs.

• Cardiac tissue is simple, as it is found only in the heart and is involuntary; it's uninucleated, branched, and striated.

Nervous Tissue:

Fig: Neuron

• The nervous system consists of long neural cells called neurons, which are responsible for transporting stimuli from one part of the body to another.
• A neuron is made up of a cell body (which contains a nucleus and cytoplasm), dendrites (long, thin, hair-like portions that emerge from the cell body), and an axon (a single long component).
• A nerve impulse is a signal that travels along a nerve fibre.
• Nerve impulses provide us with the ability to move our muscles when we wish to.
• Most animals rely on a functional combination of nerve and muscle tissue to function.
• This combination allows animals to respond to stimuli quickly.

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The grip of the term "tissues" is pivotal to developing a sound understanding of the subject of biology because it teaches how cells get integrated to contribute to organs as well as organ systems. The NCERT Class 9 Science Chapter 6 Notes are based on intricate aspects and make such complex topics perfectly suited for instantaneous revision and use in exams. Using these notes and NCERT Solutions, learners can improve conceptual clarity along with retention. To enhance your learning and ace examinations, download the NCERT Notes PDF and read anytime, anywhere.

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