Microorganisms, Forces & Matte

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### Microorganisms: Friend and Foe Microorganisms, or microbes, are tiny living organisms that cannot be seen with the unaided eye. They are classified into four major groups: bacteria, fungi, protozoa, and algae. Viruses are also microscopic but reproduce only inside host cells. #### Types of Microorganisms - **Bacteria**: Single-celled, found everywhere. - **Fungi**: Single or multicellular, grow on various surfaces (e.g., bread mould, Penicillium, Aspergillus). - **Protozoa**: Single-celled, often parasitic (e.g., Amoeba, Paramecium). - **Algae**: Single or multicellular, photosynthetic (e.g., Chlamydomonas, Spirogyra). - **Viruses**: Reproduce only inside host cells; cause diseases like cold, flu, polio, chickenpox. #### Friendly Microorganisms - **Curd & Bread Making**: *Lactobacillus* bacteria convert milk to curd. Yeast helps in fermentation for bread, idlis, and dosa batter. - **Alcohol Production**: Yeast converts sugar into alcohol (fermentation). Louis Pasteur discovered fermentation in 1857. - **Medicinal Use (Antibiotics)**: Kill or stop the growth of disease-causing microorganisms. Produced from bacteria and fungi (e.g., Streptomycin, Tetracycline, Erythromycin). Alexander Fleming discovered penicillin from mould in 1929. - **Vaccines**: Dead or weakened microbes introduced into the body to stimulate antibody production, providing immunity. Edward Jenner discovered the smallpox vaccine in 1798. - **Cleaning the Environment**: Microbes decompose organic waste into harmless substances. - **Increasing Soil Fertility**: Some bacteria and blue-green algae (e.g., *Rhizobium*, cyanobacteria) fix atmospheric nitrogen into the soil, acting as biological nitrogen fixers. #### Harmful Microorganisms (Pathogens) - **Disease-causing**: Pathogens enter the body through air, water, food, or direct contact. - **Communicable Diseases**: Spread from an infected person to a healthy person (e.g., cholera, common cold, chickenpox, tuberculosis). - **Carriers**: Insects/animals that transmit microbes (e.g., *Anopheles* mosquito for malaria, *Aedes* mosquito for dengue). - **Human Diseases**: - Bacteria: Tuberculosis, Typhoid, Cholera. - Virus: Measles, Chickenpox, Polio, Hepatitis A. - Protozoa: Malaria, Dysentery. - **Animal Diseases**: Anthrax (bacteria), Foot and mouth disease (virus). - **Plant Diseases**: Citrus Canker (bacteria), Rust of wheat (fungi), Yellow vein mosaic of bhindi (virus). - **Food Poisoning**: Caused by microorganisms growing on food and producing toxic substances. #### Food Preservation - **Chemical Methods (Preservatives)**: Salts, edible oils, sodium benzoate, sodium metabisulphite prevent microbial growth (e.g., in pickles, jams, squashes). - **Common Salt**: Used for meat, fish, amla, raw mangoes. - **Sugar**: Reduces moisture content (e.g., jams, jellies, squashes). - **Oil & Vinegar**: Prevents spoilage (e.g., pickles, vegetables, fish). - **Heat & Cold Treatments**: - Boiling milk kills microbes. - Refrigeration inhibits microbial growth. - **Pasteurisation**: Heating milk to 70°C for 15-30 seconds, then chilling rapidly to prevent microbial growth (Louis Pasteur). - **Storage & Packing**: Dry fruits and vegetables in sealed airtight packets. #### Nitrogen Cycle - **Atmospheric Nitrogen**: 78% of air, essential for proteins, chlorophyll, nucleic acids, vitamins. - **Nitrogen Fixation**: Bacteria and blue-green algae convert atmospheric nitrogen into usable compounds. - **Assimilation**: Plants absorb nitrogen compounds from soil; animals obtain nitrogen by eating plants. - **Ammonification/Nitrification**: When plants/animals die, soil bacteria/fungi convert nitrogenous waste into nitrogenous compounds. - **Denitrification**: Certain bacteria convert nitrogen compounds back into gaseous nitrogen, returning it to the atmosphere. ### Forces and Their Effects A **force** is a push or pull applied to an object, resulting from its interaction with another object. The SI unit of force is **newton (N)**. #### Effects of Force A force can: - Make an object move from rest. - Change the speed of a moving object. - Change the direction of motion of an object. - Change the shape of an object. - Cause some or all of these effects. #### Types of Forces ##### 1. Contact Forces Require physical contact between objects. - **Muscular Force**: Force exerted by muscles (e.g., lifting, pushing, running). Used by animals, birds, fish, insects for movement. - **Friction**: Force that opposes motion between two surfaces in contact. Arises due to irregularities on surfaces. Greater on rough surfaces. Acts in a direction opposite to motion. Also acts on objects moving through liquids and gases (e.g., air resistance, water resistance). ##### 2. Non-Contact Forces Act on objects even without physical contact. - **Magnetic Force**: Force exerted by magnets on other magnets or magnetic materials. Like poles repel, unlike poles attract. - **Electrostatic Force**: Force exerted by a charged body on another charged or uncharged body. Occurs when electrical charges build up on surfaces (static charges). Like charges repel, unlike charges attract. - **Gravitational Force (Gravity)**: The force with which Earth (or any celestial body) attracts objects towards itself. Always an attractive force. #### Weight and Mass - **Mass**: The quantity of matter present in an object. Measured in grams (g) or kilograms (kg). Its value remains constant everywhere. - **Weight**: The force with which Earth pulls an object towards itself. Measured in Newtons (N). Weight can change depending on the gravitational force (e.g., on Moon vs. Earth). - **Spring Balance**: A device used to measure weight (force). #### Floating and Sinking (Buoyancy) - **Upthrust (Buoyant Force)**: An upward force applied by a liquid on an object immersed in it. - **Archimedes' Principle**: An object fully or partially immersed in a liquid experiences an upward force equal to the weight of the liquid displaced by the object. - **Floating**: Occurs when the buoyant force is equal to or greater than the object's weight. - **Sinking**: Occurs when the object's weight is greater than the buoyant force. - **Density**: A key factor in floating/sinking. #### Density Density is defined as the mass per unit volume of a substance. - **Formula**: $$ \text{Density} = \frac{\text{Mass}}{\text{Volume}} $$ - **SI Unit**: Kilogram per cubic meter (kg/m³). Other units: g/mL, g/cm³. - **Effect of Temperature**: Generally, density decreases with increasing temperature (volume increases, mass constant). Hot air rises because it is less dense. - **Effect of Pressure**: For gases, increasing pressure increases density. For liquids and solids, the effect is negligible. - **Relative Density**: Ratio of the density of a substance to the density of water at a specific temperature. It is a unitless number. #### Measuring Mass and Volume - **Mass**: Measured using a weighing balance (digital or two-pan). - **Volume**: - **Regular Shapes**: Calculated using formulas (e.g., cuboid: $V = l \times w \times h$). - **Irregular Shapes**: Determined by water displacement method using a measuring cylinder. - **Measuring Cylinder**: A cylindrical container with markings (mL) to measure liquid volume. Smallest readable volume depends on cylinder capacity. - **Meniscus**: The curved surface of a liquid in a measuring cylinder. Reading should be taken at the bottom of the meniscus for clear liquids. ### Nature of Matter: Elements, Compounds, and Mixtures #### Mixtures A mixture is formed when two or more substances are mixed together, where each substance retains its individual properties and does not react chemically with each other. The individual substances are called **components**. ##### Types of Mixtures - **Non-uniform Mixtures (Heterogeneous)**: Components are generally visible and not evenly distributed (e.g., sprout salad, sand and water). - **Uniform Mixtures (Homogeneous / Solutions)**: Components are evenly distributed and cannot be distinguished (e.g., sugar dissolved in water, stainless steel, air). - **Alloys**: Homogeneous mixtures of metals (e.g., brass, bronze, stainless steel). #### Pure Substances A pure substance has no other substance present in it and consists of the same type of particles. - **Elements**: Simplest substances that cannot be broken down into simpler substances by physical or chemical means. They are the building blocks of all matter. Made up of identical particles called atoms. - **Examples**: Gold, silver, sulfur, carbon, hydrogen, oxygen. - **Classification**: Metals, non-metals, metalloids. - **States**: Most are solid at room temperature; 11 are gaseous (e.g., oxygen, nitrogen); 2 are liquid (mercury, bromine). - **Compounds**: Formed when two or more elements combine chemically in a fixed ratio. The properties of a compound are different from its constituent elements. - **Examples**: Water ($H_2O$), common salt (NaCl), sugar ($C_{12}H_{22}O_{11}$). - **Separation**: Cannot be separated by physical methods; requires chemical methods. #### Elements, Compounds, and Mixtures in Daily Life - **Air**: A mixture of gases (nitrogen, oxygen, argon, carbon dioxide, water vapour). - **Water**: A compound of hydrogen and oxygen. - **Minerals**: Natural, solid substances found in Earth. - Can be pure elements (e.g., gold, silver, copper, sulfur, carbon). - Most are compounds (e.g., quartz, calcite, mica). ### Light: Mirrors and Lenses #### Spherical Mirrors Mirrors with reflecting surfaces that are part of a hollow sphere. - **Concave Mirror**: Reflecting surface curves inwards. Forms erect and enlarged images when objects are close; inverted and smaller images when objects are farther away. Used in torches, headlights, dental mirrors. - **Convex Mirror**: Reflecting surface curves outwards. Always forms erect and diminished images. Provides a wider field of view. Used as side-view mirrors in vehicles, road safety mirrors, surveillance mirrors. #### Laws of Reflection Valid for all types of mirrors (plane, concave, convex). 1. The angle of incidence (i) is equal to the angle of reflection (r). 2. The incident ray, the normal to the mirror at the point of incidence, and the reflected ray all lie in the same plane. #### Lenses A piece of transparent material (e.g., glass, plastic) with curved surfaces that refract light. - **Convex Lens (Converging Lens)**: Thicker at the middle, thinner at the edges. Converges parallel light beams. Forms enlarged, diminished, or same-size images; can be erect or inverted depending on object distance. Used in magnifying glasses, cameras, telescopes, microscopes, eyeglasses, human eye. - **Concave Lens (Diverging Lens)**: Thicker at the edges, thinner at the middle. Diverges parallel light beams. Always forms erect and diminished images. Used in eyeglasses. ### How Nature Works in Harmony (Ecosystems) An **ecosystem** consists of biotic (living) and abiotic (non-living) components interacting with each other. #### Components of an Ecosystem - **Biotic Components**: Living organisms (plants, animals, microorganisms). - **Producers (Autotrophs)**: Make their own food (e.g., plants via photosynthesis). - **Consumers (Heterotrophs)**: Obtain food by eating other organisms. - **Herbivores**: Eat plants (e.g., deer, hare). - **Carnivores**: Eat animals (e.g., leopard, eagle). - **Omnivores**: Eat both plants and animals (e.g., crows, foxes, mice). - **Decomposers (Saprotrophs)**: Break down dead organic matter, recycling nutrients (e.g., bacteria, fungi like mushrooms). - **Abiotic Components**: Non-living physical and chemical factors (e.g., air, water, soil, sunlight, temperature). #### Interactions in an Ecosystem - **Biotic-Biotic Interactions**: - **Food Chains**: Linear sequence showing "who eats whom" (e.g., Grass → Grasshopper → Frog → Snake → Eagle). Each organism occupies a **trophic level**. - Producers (1st trophic level) - Herbivores (2nd trophic level) - Small Carnivores (3rd trophic level) - Large Carnivores (4th trophic level) - **Food Webs**: Interconnected food chains, forming a network. - **Competition**: Organisms compete for resources (food, water, space, sunlight). Helps control population size. - **Symbiotic Relationships**: - **Mutualism**: Both organisms benefit (e.g., honeybees and flowers). - **Commensalism**: One benefits, the other is unaffected (e.g., orchids on trees). - **Parasitism**: One benefits, the other is harmed (e.g., ticks on dogs). - **Biotic-Abiotic Interactions**: - Organisms depend on abiotic factors (e.g., plants need sunlight, water, CO2; animals need oxygen). - Abiotic factors are influenced by biotic factors (e.g., plants release oxygen, hold soil, retain moisture). #### Types of Ecosystems - **Aquatic Ecosystems**: Ponds, rivers, lakes, oceans. - **Terrestrial Ecosystems**: Forests, grasslands, deserts, farmlands. - **Human-made Ecosystems**: Farmlands, parks, fish ponds. #### Ecosystem Balance and Disturbances - Ecosystems maintain balance through interactions, keeping populations and resources stable. - **Changes**: Natural or human-made changes can disrupt this balance. - **Human Activities**: Pollution, deforestation, habitat loss, climate change, invasive species, overexploitation of resources. - **Consequences**: Loss of biodiversity, soil degradation, increased pests (e.g., frog leg export leading to increased agricultural pests). #### Ecological Concepts - **Population**: A group of the same type of organisms in a habitat at a given time. - **Community**: Comprises multiple populations sharing the same habitat. - **Decomposition**: Process by which decomposers break down dead organic matter, recycling nutrients back into the environment.