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      Class 9 Science

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      • Class 09
      • Class 9 Science
      CoursesClass 09ScienceClass 9 Science
      • 01.Matter in Our Surroundings
        9
        • Lecture1.1
          Matter and Its Properties 39 min
        • Lecture1.2
          States of Matter and Compressibility & Rigidity 21 min
        • Lecture1.3
          Moving through, Fluidity, Density, Diffusion, Pressure 26 min
        • Lecture1.4
          Change of State of Matter 56 min
        • Lecture1.5
          Evaporation and Boiling 39 min
        • Lecture1.6
          Cooling Effect of Evaporation Two More States of Matter 22 min
        • Lecture1.7
          Chapter Notes – Matter in Our Surroundings
        • Lecture1.8
          NCERT Solutions – Matter in Our Surroundings
        • Lecture1.9
          Revision Notes Matter in Our Surroundings
      • 02.Is Matter Around Us Pure
        9
        • Lecture2.1
          Elements and Compounds 20 min
        • Lecture2.2
          Mixtures, Homogeneous & Heterogeneous and Chemical & Physical Change 37 min
        • Lecture2.3
          Solution, Suspension, Colloid and Tyndal Effect 48 min
        • Lecture2.4
          Terms related to Solution and Solubility 42 min
        • Lecture2.5
          Separation of Mixtures 47 min
        • Lecture2.6
          Cleaning Drinking Water and Classification of Matter 29 min
        • Lecture2.7
          Chapter Notes – Is Matter Around Us Pure
        • Lecture2.8
          NCERT Solutions – Is Matter Around Us Pure
        • Lecture2.9
          Revision Notes Is Matter Around Us Pure
      • 03.Atoms and Molecules
        7
        • Lecture3.1
          Atom and its Properties, Atomic Mass, Molecule and Molecular Mass 40 min
        • Lecture3.2
          Ions, Valency and Writing the formulae of Compounds 47 min
        • Lecture3.3
          Mole Concept 42 min
        • Lecture3.4
          Calculation of no. of Moles, Percentage of an Element in a Compound and Laws of Chemical Combination 30 min
        • Lecture3.5
          Chapter Notes – Atoms and Molecules
        • Lecture3.6
          NCERT Solutions – Atoms and Molecules
        • Lecture3.7
          Revision Notes Atoms and Molecules
      • 04.Structure of The Atom
        7
        • Lecture4.1
          Charged Particles in Matter and Discovery of Sub – atomic Particles 31 min
        • Lecture4.2
          Atomic Model by J.J Thomson’s Model and Rutherford 57 min
        • Lecture4.3
          Ion, Mass Number, Isotopes, Isobar and Fractional Mass number of Elements 01 hour
        • Lecture4.4
          Electron Distribution in Orbits and Valency 01 hour
        • Lecture4.5
          Chapter Notes – Structure of The Atom
        • Lecture4.6
          NCERT Solutions – Structure of The Atom
        • Lecture4.7
          Revision Notes Structure of The Atom
      • 05.Cell - Fundamental Unit of Life
        7
        • Lecture5.1
          Introduction to Cell and Its Structure – Cell Wall 31 min
        • Lecture5.2
          Cell Membrane, Cytoplasm, Nucleus 32 min
        • Lecture5.3
          Ribosomes, Endoplasmic Reticulum, Golgi bodies, Lisosomes, Mitocondria 38 min
        • Lecture5.4
          Plastids, Vacuole; Types of Cell and Transport through Plasma Membrane 33 min
        • Lecture5.5
          Chapter Notes – Cell – Fundamental Unit of Life
        • Lecture5.6
          NCERT Solutions – Cell – Fundamental Unit of Life
        • Lecture5.7
          Revision Notes Cell – Fundamental Unit of Life
      • 06.Tissues
        8
        • Lecture6.1
          Division of Labour, Plant Tissues – Merismatic Tissue 20 min
        • Lecture6.2
          Plant Tissue-Permanent Tissue: Simple Permanent Tissue 34 min
        • Lecture6.3
          Plant Tissue-Permanent Tissue: Complex and Protective Tissue 31 min
        • Lecture6.4
          Animal Tissue- Muscular Tissue and Nervous Tissue 27 min
        • Lecture6.5
          Animal Tissue- Connective Tissue and Epithelial Tissue 42 min
        • Lecture6.6
          Chapter Notes – Tissues
        • Lecture6.7
          NCERT Solutions – Tissues
        • Lecture6.8
          Revision Notes Tissues
      • 07.Diversity in Living Organisms
        8
        • Lecture7.1
          Introduction to Biodiversity and Classification, Nomenclature 35 min
        • Lecture7.2
          The Five Kingdoms 29 min
        • Lecture7.3
          Plantae Kingdom 42 min
        • Lecture7.4
          Animalia Kingdom 01 hour
        • Lecture7.5
          Classification of Chordates and Revision of Animalia Kingdom 33 min
        • Lecture7.6
          Chapter Notes – Diversity in Living Organisms
        • Lecture7.7
          NCERT Solutions – Diversity in Living Organisms
        • Lecture7.8
          Revision Notes Diversity in Living Organisms
      • 08.Motion
        11
        • Lecture8.1
          Straight Line Motion, Position, Vector and Scalar; 23 min
        • Lecture8.2
          Distance & Displacement 48 min
        • Lecture8.3
          Speed and Velocity 57 min
        • Lecture8.4
          Acceleration and Deacceleration, Uniform & Non-uniform Acceleration 47 min
        • Lecture8.5
          Equations of Uniformly Accelerated Motion 58 min
        • Lecture8.6
          Uniform Circular Motion 30 min
        • Lecture8.7
          Graphical representation of Motion 30 min
        • Lecture8.8
          Calculations Using Graph 28 min
        • Lecture8.9
          Chapter Notes – Motion
        • Lecture8.10
          NCERT Solutions – Motion
        • Lecture8.11
          Revision Notes Motion
      • 09.Force and Newtons Laws of Motion
        12
        • Lecture9.1
          Force and Net or Resultant Force 46 min
        • Lecture9.2
          Newton’s 1st Law 46 min
        • Lecture9.3
          Momentum 46 min
        • Lecture9.4
          Newton’s 2nd Law 27 min
        • Lecture9.5
          Newton’s 2nd Law in Terms of Acceleration; 42 min
        • Lecture9.6
          Newton’s 1st Law from 2nd law and Practical Examples of Newton’s 2nd Law 42 min
        • Lecture9.7
          Newton’s 3rd Law and its Practical Examples 35 min
        • Lecture9.8
          Conservation of Momentum 33 min
        • Lecture9.9
          Practical Applications of Conservation of Momentum 29 min
        • Lecture9.10
          Chapter Notes – Force and Newtons Laws of Motion
        • Lecture9.11
          NCERT Solutions – Force and Newtons Laws of Motion
        • Lecture9.12
          Revision Notes Force and Newtons Laws of Motion
      • 10.Gravitation
        9
        • Lecture10.1
          Universal Law of Gravitation and Free Fall 41 min
        • Lecture10.2
          Falling Bodies: case 1 46 min
        • Lecture10.3
          Falling bodies: case 2 and Air Resistance 42 min
        • Lecture10.4
          Value of g, Mass and Weight, Weight on Moon, Circular Motion and Gravitation 48 min
        • Lecture10.5
          Thrust and Pressure and Pressure in fluids 37 min
        • Lecture10.6
          Archimedes Principle; Density 37 min
        • Lecture10.7
          Chapter Notes – Gravitation
        • Lecture10.8
          NCERT Solutions – Gravitation
        • Lecture10.9
          Revision Notes Gravitation
      • 11.Work and Energy
        7
        • Lecture11.1
          Work and Workdone Against Gravity, Oblique Displacement 01 hour
        • Lecture11.2
          Energy and Different Forms of Energy, Derivation of Formulae of K.E. 58 min
        • Lecture11.3
          Transformation of Energy and Law of Conservation of Energy 01 hour
        • Lecture11.4
          Rate of doing Work and Commercial Unit of Energy 43 min
        • Lecture11.5
          Chapter Notes – Work and Energy
        • Lecture11.6
          NCERT Solutions – Work and Energy
        • Lecture11.7
          Revision Notes Work and Energy
      • 12.Sound
        8
        • Lecture12.1
          Production and Propagation of Sound and Medium for Sound 30 min
        • Lecture12.2
          Frequency and Velocity of Sound Wave, Characteristic of Sound 01 hour
        • Lecture12.3
          Sonic Boom, Light faster than Sound, Reflection of Sound, Echo and Reverberation 56 min
        • Lecture12.4
          Types of Sound Based on Frequency 42 min
        • Lecture12.5
          Human Ear and Intensity of Sound 25 min
        • Lecture12.6
          Chapter Notes – Sound
        • Lecture12.7
          NCERT Solutions – Sound
        • Lecture12.8
          Revision Notes Sound
      • 13.Why do We Fall Ill
        7
        • Lecture13.1
          Factors Determining Health, Disease, Look of Disease, Cause of Disease, Types of Diseases 24 min
        • Lecture13.2
          Infectious Diseases, Immune System, Treatment of Diseases 55 min
        • Lecture13.3
          Prevention from Disease, Vaccination – Immunisation 36 min
        • Lecture13.4
          AIDS, Different Modes for Different Diseases 18 min
        • Lecture13.5
          Chapter Notes – Why do We Fall Ill
        • Lecture13.6
          NCERT Solutions – Why do We Fall Ill
        • Lecture13.7
          Revision Notes Why do We Fall Ill
      • 14.Natural Resources
        7
        • Lecture14.1
          Natural Resource-Air and its Pollution 57 min
        • Lecture14.2
          Natural Resource-Water and Soil and its Pollution 49 min
        • Lecture14.3
          Biogeochemical Cycles 33 min
        • Lecture14.4
          Green House Effect, Global Warming and Ozone Layer Depletion 30 min
        • Lecture14.5
          Chapter Notes – Natural Resources
        • Lecture14.6
          NCERT Solutions – Natural Resources
        • Lecture14.7
          Revision Notes Natural Resources
      • 15.Improvements in Food Resources
        7
        • Lecture15.1
          Various Revolution Held in India; Types of Crops; Crop Season; Crop Variety Improvement 31 min
        • Lecture15.2
          Crop Production Improvement 45 min
        • Lecture15.3
          Crop Protection Improvement and Organic Farming 29 min
        • Lecture15.4
          Animal Husbandry 40 min
        • Lecture15.5
          Chapter Notes – Improvements in Food Resources
        • Lecture15.6
          NCERT Solutions – Improvements in Food Resources
        • Lecture15.7
          Revision Notes Improvements in Food Resources

        Chapter Notes – Cell – Fundamental Unit of Life

        The Fundamental Unit of Life

        The body of all organisms is made up of very small units called cell.

        A cell is capable of independent existence and can carry out all the functions which are necessary for a living being. Unicellular organisms are capable of independent existence which shows a cell’s capability to exist independently like in amoeba. Due to this, a cell is called the fundamental, structural and functional unit of living organisms and basic unit of life.

        Discovery of Cell and Cell Theory

        Cell was first discovered by Robert Hooke in 1665. He observed that just like honeycomb, organisms are also composed of small compartments. He named these compartments as Cells.

        Cell theory state that:

        • All living organisms are composed of cells.
        • Cell is the fundamental unit of life.
        • All new cells come from pre-existing cells.

        Shape and Size of Cells

        Cells vary in shape and size. They may be oval, spherical, rectangular, spindle shaped, or totally irregular like the nerve cell. The Size of cell also varies in different animals and plants. Most of the cells are microscopic in size like red blood cells (RBC) while some cells are fairly large like nerve cells. Average size of cells varies from 0.5 to 20.

        Types of Cells:

        The cells can be categorized in two types:

        1. Prokaryotic Cell 2. Eukaryotic Cell

        Prokaryotic cell

        In some organisms, DNA and RNA (genetic substances) are bound by a membrane; this is termed as true nucleus. Prokaryotic cells are cells in which true nucleus is absent. They are primitive and incomplete cells. Prokaryotes are always unicellular organisms. Bacteria, blue green algae areD:\Diagrams\proka.jpgexamples of prokaryotes.

        Eukaryotic Cell

        Eukaryotic cells are cells in which true nucleus is present. They are advanced and complete cells. Eukaryotes include all living organisms (both unicellular and multi-cellular organisms) except bacteria and blue green algae.

        D:\Diagrams\Eukeryotic.jpgCell Structures

        Cell is composed of some basic structures:

        Plasma Membrane: Plasma membrane is the covering of the cell that separates the contents of the cell from its external environment. It is a living part of the cell. It is very thin, delicate, elastic and selectively permeable membrane. Plasma membrane is composed of lipid and protein.

        Function:

        As it is selectively permeable membrane, it allows the flow of limited substances in and out of the cell.

        Cell wall: Cell wall is non-living, thick and freely permeable covering made up of cellulose. Cell wall is available in eukaryotic plant cells and in prokaryotic cells.

        Functions:

        • It determines the shape of the cell.
        • It protects the plasma membrane.
        • It prevents desiccation or dryness in cells.
        • It helps in the transport of various substances in and out of the cell.

        Protoplasm: It is a jelly-like, viscous, colourless semi-fluid substance in various cell organelles present in colloidal form.

        Protoplasm consists two parts: cytoplasm and nucleoplasm.

        Cytoplasm is that part of protoplasm which surrounds the nucleus.

        Nucleoplasm is that part of protoplasm which is located inside the nucleus.

        Functions:

        • Protoplasm acts as a store of vital chemicals like amino acids, proteins, sugars etc.
        • It is the site of some metabolic reactions.

        Golgi Body: Golgi body are also called Golgi Complex/ Golgi Apparatus. It is first discovered by Camillo Golgi. It consists of membrane bound structures arranged parallel to each other.

        Functions:

        • Golgi bodies store, modify, package and dispatch the substances.
        • They help in the formation of lysosomes.

        Ribosomes: These are extremely small, dense and round bodies interspersed in the cytoplasm. Ribosomes are made up of ribonucleic acid(RNA) and proteins. In prokaryotic cell, ribosomes are of 70 types. In eukaryotic cells, ribosomes are of 80 types. Ribosome is responsible for protein synthesis.

        Mitochondria: Mitochondria are small rod-shaped organelles. It is a double membrane structure. Outer membrane is smooth whereas inner membrane is projected into numerous finger-like structures; called cristae. Mitochondria contain their own DNA and ribosomes.

        Functions:

        • They provide energy for the vital activities of living cells.
        • They store energy releases during reactions, in the form of ATP (Energy currency of the cell). Therefore it is also called power house of the cell.

        Centrosome and Centrioles:

        Centrosome is found only in eukaryotic animal cells. It is not bounded by any membrane but consists of centrioles. Centrioles are hollow cylindrical structures arranged at right angle to each other and made up of microtubules.

        Centrioles help in cell division and also help in the formation of cilia and flagella.

        Plastids: Plastids are present in most of the plant cells and absent in animals cells. They are usually spherical or discoidal in shaped. These are double membrane bound organelles. Plastids also have its own DNA and ribosomes.

        Plastids are of three types:

        1. Chloroplasts: Green coloured plastids containing chlorophyll. Chloroplasts manufacture food by the process of photosynthesis.
        2. Chromoplasts: Colourful plastids. They provide colour to flowers and fruits.
        3. Leucoplasts: Colourless plastids. They help in the storage of various substances like starch, proteins and fats.

        Lysosomes: Lysosomes are formed by golgi bodies. They are small, spherical, sac like structures which contain several digestive enzymes enclosed in a membrane. They are found in eukaryotic cells mostly in animals.

        Functions:

        • Lisosomes help in digestion of foreign substances and worn-out cell organelles.
        • They provide protection against bacteria and virus.
        • They help to keep the cell clean.
        • During the disturbance in cellular metabolism, for eg; when the gets damaged, lysosomes may burst and the enzymes digest their own cell. Therefore, lysosomes are also known as suicide bags of a cell.

        Vacuoles: Vacuoles are liquid / solid filled in a membrane. In plant cells, vacuoles are large and permanent. In animal cells, vacuoles are small in size and temporary. In mature plant cell, it occupies 90% space of cell volume. Due to its size, other organelles including nucleus shift towards plasma membrane.

        Endoplasmic Reticulum: It is a network of tube like structures from nuclear membrane to plasma membrane. It is absent in prokaryotic cells and matured RBCs of mammals.

        There are two types of endoplasmic reticulum:

        1. Rough ER: In rough endoplasmic reticulum, ribosomes are present on the surface.
        2. Smooth ER: Ribosomes are absent.

        Functions:

        • It gives internal support to cell.
        • It helps in transport of various substances from nuclear membrane to plasma membrane or vice versa.
        • It helps in the formation of plasma membrane and golgi bodies.
        • Rough ER helps in synthesis and transportation of proteins.
        • Smooth ER helps in synthesis and transport of lipids.

        Nucleus: Nucleus is dense and spherical organelle. Nucleus is bounded by two membranes, both forming nuclear envelope. Nuclear envelope contains many pores known as nuclear pores. The fluid which is inside the nucleus is called nucleoplasm. Nucleus contains chromosomes and chromosomes contain genes which are the carriers of genetic information.

        Functions:

        • Nucleus controls all the metabolic activities of cell.
        • Nucleus is the storehouse of genes. Without nucleus, cell can neither survive nor shows specialized activities.

        Transport of Substances through Plasma Membrane

        Substance can pass through plasma membrane by two processes: Diffusion and Osmosis.

        Diffusion: It is the process of movement of substances from its high concentration to low concentration.

        During the respiration, carbon dioxide is given out a waste product and accumulates in higher concentration inside the cell compared to outside. Due to the difference in concentration inside and outside the cell, CO2 start moving out of the cell.

        Osmosis: It is the process of movement of water from its high concentration to its low concentration through semi-permeable membrane.

        • If the medium surrounding the cell has higher water concentration than in cell, cell will gain water by osmosis. Such dilute solution is called Hypotonic solution. Though water molecules pass across plasma membrane in both sides but more water will enter inside the cell. The cell is therefore, swell up and increase in volume. This process is called Endosmosis.
        • If the medium surrounding the cell is exactly the same water concentration as inside the cell, there will no net movement of water across membrane resulting in no change in size of cell. Such solution is called Isotonic solution.
        • If the medium surrounding the cell has lower water concentration than inside the cell, the cell will lose water through osmosis. Such concentrated solution is called Hypertonic solution. The cell will therefore, shrink and reduce in volume. This process is known as Exosmosis.
        Prev Plastids, Vacuole; Types of Cell and Transport through Plasma Membrane
        Next NCERT Solutions – Cell – Fundamental Unit of Life

          3 Comments

        1. virat yadav
          November 6, 2021
          Reply

          Excellent explaination

        2. Daym Boi
          November 15, 2021
          Reply

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        3. albinanoopj
          September 26, 2022
          Reply

          Amazing content…appreciate it.

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