The-Invisible-Living-World-Beyond-Our-Naked-Eye chapter 2.pdf/8th science curiosity /by k sandeep swamy

The-Invisible-Living-World-Beyond-Our-Naked-Eye chapter 2.pdf/8th science curiosity /by k sandeep swamy

• 1.
  The Invisible LivingWorld: Beyond Our Naked Eye Have you ever wondered what you might see if the invisible world around you became visible? How would your observation of this hidden world change the way you think about size, complexity, or even what counts as 'living'? By:K Sandeep Swamy (M.sc,B.Ed) For Online Classes (foundation and academics) contact : 9491878325 Subscribe Samyans Eduhub youtube channel
• 2.
  Probe and Ponder InvisibleWonders Have you ever wondered what you might see if the invisible world around you became visible? Changing Perspectives How do you think your observation of this hidden world might change the way you think about size, complexity, or even what counts as 'living'? Tiny Interactions Have you thought how these tiny living beings interact with each other?
• 3.
  The Amazing Varietyof Living Beings Just look around4there are so many beautiful plants and animals! They are of all shapes, sizes, and colors. Some living beings are tiny, while others are really big. They differ not only in their structure but also in many other features. All these living beings, whether plants or animals, are called organisms. Have you ever noticed the smallest organism around you that is visible to the naked eye? Think about it4how small a thing can your eyes actually see?
• 4.
  Magnifying Our View Youmight have seen some people using reading glasses. How does it help them see better? Or what happens when we use a magnifying glass to observe something? Activity 2.1: Let us observe Take a round-bottom flask made up of glass. Fill it with water. Close the mouth of the flask with a cork. Now, place the flask on an open book and look at the letters through it. Do you notice something interesting? The letters appear larger when seen through the flask! This happens because the flask filled with water acts like a magnifying glass.
• 5.
  The Discovery ofCells 1 1665 Robert Hooke published Micrographia, showing detailed drawings of tiny things using a microscope that magnified objects 200-300 times. 2 Cork Observation Hooke observed a thin slice of cork and saw it was made of many small, empty spaces that reminded him of a honeycomb. He called each small space a cell. 3 1660s Antonie van Leeuwenhoek made better lenses and microscopes, becoming the first person to clearly see and describe tiny living things like bacteria and blood cells.
• 6.
  What Is aCell? All living beings are made up of cells. You might wonder what cells actually look like. Let's take a closer look at the basic structure of a cell using a microscope through an activity. Prepare the Onion Sample Wash and cut an onion, then carefully peel a thin, transparent layer from its inner surface. Stain and Rinse Place the onion peel in a petri dish with safranin for 30 seconds to stain it, then rinse with water. Mount the Specimen Transfer the stained peel onto a glass slide, add a drop of glycerin, and gently cover with a coverslip. Observe Under Microscope Finally, place your prepared slide under a microscope to view the intricate structure of the onion cells.
• 7.
  Basic Parts ofa Cell Cell Membrane The thin outer layer that encloses the cytoplasm and nucleus. It separates one cell from another and is porous, allowing essential materials to enter and waste to exit. Cytoplasm The space between the cell membrane and nucleus. It contains other components of the cell and compounds such as carbohydrates, proteins, fats, and mineral salts. Most life processes take place here. Nucleus The round structure in the middle covered by a thin membrane. It regulates all activities that occur within the cell and controls growth. Cell Wall Some cells, like onion peel cells, have an extra outer layer called the cell wall, which provides rigidity and strength to plants.
• 8.
  Observing Human Cells Activity2.3: Let us investigate Rinse your mouth with clean water. 1. Use the blunt end of a clean toothpick to gently scrape the inside of your cheek. 2. Place the scraped material in a drop of water on a clean glass slide. 3. Add a drop of methylene blue over the material. 4. Add a drop of glycerin and place a coverslip. 5. Observe the slide under a microscope. 6. You will observe polygon-shaped structures called cheek cells, which form the inner lining of your mouth.
• 9.
  Plant Cell Structures Cellsin all parts of a plant have tiny rod-shaped structures called plastids. Some plastids, like chloroplasts, contain chlorophyll, which makes them green and helps in photosynthesis. Plant cells also have a large, empty-looking space called a vacuole. This helps the plant cell store important substances, get rid of waste, and maintain the shape of the cell, giving strength and support to the plant. In animal cells, vacuoles are usually not present, or if present, they are usually small. These small vacuoles store certain substances dissolved in water.
• 10.
  Variation in CellShape and Structure Muscle Cell Shaped like a spindle. The thin, flexible, and spindle-shaped structure helps muscle cells contract and relax, enabling movement in the body. Nerve Cell Very long with branches. The elongated shape and branched structure help neurons reach different parts of the body and pass on messages quickly. The unique shape, size, and structure of cells help them carry out their specific functions in the body.
• 11.
  Levels of Organisationin Living Organisms Cell The basic unit of life, just like a brick is the basic unit of a wall. Tissue A group of similar cells that form a type of tissue. Organ Different tissues organized to form an organ. Organ System Several organs working together to form an organ system that performs a major function of the body. Organism All the organ systems together make up a complete organism4like a plant or an animal. These levels of organisation help us understand how simple building blocks like cells come together to form a complex living being.
• 12.
  Did You Know? TheLargest Cell The yolk of an ostrich egg is a single cell4the largest known cell in the living world4measuring about 130 mm to 170 mm in diameter. The egg contains extra non-cellular material: a shell for protection and a white liquid that nourishes the cell during its continued development.
• 13.
  What Are Microorganisms? Someliving organisms are made up of just one or very few cells. They are so small that they cannot be seen with the naked eye. These are called microorganisms. Some microorganisms, like bacteria and Amoeba, are made of just one cell (unicellular). Others, like some fungi and algae, have many cells (multicellular). They are found all around us4in water, soil, air, and even inside our body! To observe the cells of a microorganism, we need to use a microscope which magnifies their size and makes them visible to us.
• 14.
  Observing Microorganisms 1 Pond WaterObservation Collect pond or stagnant water in a container Place a drop on a microscope slide Cover with a coverslip and observe under microscope Look for tiny moving organisms 2 Soil Suspension Observation Collect moist soil in a beaker Add water and stir to create soil suspension Let the mixture settle Take a drop from the top layer and observe under microscope The tiny creatures that cannot be seen with the naked eye are called microorganisms (micro means very small; organisms means living beings) or microbes.
• 15.
  Types of Microorganismsin Pond Water Amoeba (Protozoa) Single cell, moving, irregular shape Paramecium (Protozoa) Single cell, moves from one place to another, movement takes place with the help of specialized structures Algae Single cell, looks green because of the presence of green pigment, movement takes place with the help of specialized structures
• 16.
  Types of Microorganismsin Soil Bread Mould (Fungi) Branched filament without chlorophyll having sac-like structure Mould (Fungi) Branched filament without chlorophyll having brush-like structure Bacteria Spherical, comma, spiral or rod-shaped, with hair-like structures around the cell
• 17.
  Viruses: Acellular Microorganisms Virusesare microscopic and acellular (not made of cells). They multiply only when they enter a living cell. They may infect plants, animals, or bacterial cells and may cause diseases. Unlike bacteria, fungi, and other microorganisms, viruses cannot reproduce on their own. They need a host cell to make copies of themselves. Viruses are sometimes described as being "on the edge of life" because they have some properties of living things but lack others.
• 18.
  Microorganisms in OurEnvironment Have you ever seen a lemon, tomato, orange, or any other food item rot after being left outside for some time? If yes, you may have noticed a powdery or cotton-like growth on them. This happens because they have been infected by microbes. Microorganisms can be found everywhere, be it in water, soil, air, or even in some food items. But why do microorganisms not infect pickles and murabbas? This is because you add many spices with salt or sugar which act as preservatives.
• 19.
  Microorganisms as EnvironmentalCleaners Collect Waste Collect garden soil and add fruit and vegetable peels to a container. Cover with soil and leave aside. Microbial Action Microorganisms in the soil, like fungi and bacteria, act on the plant waste and slowly break it down. Nutrient Recycling After 2-3 weeks, the waste turns into dark- colored manure, rich in nutrients that helps increase soil fertility. Microorganisms help clean our environment by breaking down waste and returning important nutrients to nature.
• 20.
  Microorganisms in FoodProduction Yeast in Bread Making Yeast is a type of fungus that grows well in warm conditions. When added to dough with sugar and warm water, it releases carbon dioxide, making the dough soft and fluffy. This property is used in making breads, cakes, and more! Bacteria in Curd Formation Bacteria like Lactobacillus feed on the sugar in milk (lactose), multiply, and ferment the milk to form curd. They produce lactic acid, which makes curd sour. These bacteria grow well in warm conditions. Bacteria in Soil Fertility Bacteria like Rhizobium live in root nodules of legumes such as beans, peas, and lentils. They trap nitrogen from the air and make it useful for plants, helping them grow better without chemical fertilizers.
• 21.
  Amazing Microalgae: TinyHelpers in Water Microalgae are microscopic plant-like organisms that live in water, soil, air, and even on trees. They make their own food using sunlight and release oxygen, producing more than half of the Earth's oxygen supply. They are rich in nutrients and serve as a food source for many aquatic animals. Some, like Spirulina, Chlorella, and Diatoms, are also used by humans as health supplements and medicines. Spirulina, a microalga, is called a superfood because it contains more than 60% protein by weight and is a good source of vitamin B12.
• 22.
  Unicellular vs. MulticellularOrganisms The body of all living organisms is made up of tiny building blocks called cells. A single cell contains various components that help organisms perform various functions. Unicellular Organisms Made up of just one cell (e.g., bacteria, protozoa, yeast) Carry out all functions necessary for survival in a single cell Multicellular Organisms Made up of many cells (e.g., plants, animals, some fungi and algae) Cells carry out specialized functions and cooperate with each other
• 23.
  Cell Structures inDifferent Organisms Animal Cells Surrounded by a cell membrane Have a well-defined nucleus May have small vacuoles No cell wall or chloroplasts Plant Cells Have a cell wall and cell membrane Have a well-defined nucleus Contain plastids including chloroplasts Have a large vacuole Bacterial Cells Have a cell wall and cell membrane No well-defined nucleus, instead have a nucleoid No membrane-bound organelles Much smaller than plant and animal cells
• 24.
  Beneficial Applications ofMicroorganisms Environmental Cleanup Microorganisms decompose plant and animal waste, cleaning the environment and returning nutrients to the soil. Food Production Microbes like yeast and bacteria help in making bread, curd, cheese, idli, dosa, and many other food items through fermentation. Agriculture Bacteria like Rhizobium in root nodules of legumes trap nitrogen from the air, increasing soil fertility naturally. Biogas Production Some bacteria decompose waste in oxygen-free environments, producing methane gas that can be used as fuel.
• 25.
  Key Takeaways: TheInvisible Living World Cell: Basic Unit of Life All living organisms are made up of cells. A typical cell has a cell membrane, cytoplasm, and nucleus. Plant, fungal, and bacterial cells have an additional cell wall. Levels of Organization Cell ³ Tissue ³ Organ ³ Organ System ³ Organism. These levels show how simple cells come together to form complex living beings. Microorganisms Tiny organisms not visible to the naked eye. They can be unicellular or multicellular and are found everywhere4in water, soil, air, and even inside our bodies. Beneficial Microbes Many microorganisms help in food production, environmental cleanup, increasing soil fertility, and even producing biogas as an energy source.