7th Basic Study Notes

 👉Malayalam

Chapter 1: Towards A Hundredfold Yield

• Cultivation Goals: When cultivating fruits, vegetables, or cereals, the common goals are a quick yield, plenty of yield, and good quality yield.
• Seed and Planting Material Selection:
  • Good quality seeds/planting materials are essential for better yield....
  • Seed Selection Factors: Seeds should be collected from ripened fruits produced during the middle of the plant’s lifespan. Factors to consider include shape, size, weight, and seed coat. Good quality seeds come from healthy, high-yielding plants and fruits with normal weight and normal size.
• Plant Reproduction Methods:
  • Vegetative Propagation (Asexual Reproduction): The process of producing new saplings from the vegetative parts of plants like root, stem, leaf, and underground stem. Examples include Curry leaf plant, Ginger plant, Bryophyllum, and Pepper plant.
  • Sexual Reproduction: Seeds are formed through sexual reproduction, and seedlings germinate from seeds.
  • Some plants, like Moringa and Sheemakonna (Gliricidia), can reproduce through both sexual reproduction (seeds) and vegetative propagation (stem cuttings).
• Methods for Producing Superior Quality Saplings:
  • Layering: A practice of producing plantlets by inducing roots in the stem of a mother plant, then cutting and planting it.
    • Process: Select a pencil-sized stem, make a 2-3 cm circular cut on the bark between nodes, apply a moist mixture of cocopeat, soil, and cow dung powder, and wrap with a polythene bag. Roots sprout within two months, then cut and plant.
    • Examples: Guava, Sapota, Java apple (jampa), Almond, Fig, Rose, Cashew tree.
    • Serpentine Layering: Done by bending long branches into the soil and covering them at intervals (nodes) to produce multiple saplings simultaneously. Examples: Bougainvillea, Jasmine, Betel, Pepper, Grapes, Chrysanthemum.
    • Advantages: Possess qualities of the mother plant, small size, early flowering and fruiting.
    • Disadvantages: Short lifespan, absence of taproot system, require more care.
    • Rooting by Dipping: Dipping stem cuttings in solutions with plant hormones like auxin can speed up root formation.
  • Grafting: A method of producing saplings by joining the stem (scion) of a superior quality plant with another plant that has roots (root stock) and belongs to the same species.
    • Process: Select a root stock (e.g., 6-month to 1-year-old Moovandan mango), cut it at 15cm from the bottom, and make a 4cm deep cut. Select a scion (e.g., Neelam mango stem with new buds), make tapered cuts, insert scion into root stock, and bind with polythene tape.
    • Advantages: Early flowering and fruiting. The new plant grows well in local soil and yields the desired fruit variety (e.g., Neelam mango on indigenous root stock).
    • Important Note: Buds growing beneath the grafted area should be removed to maintain the desired quality of the scion.
  • Budding: A method of producing superior quality planting material by joining the bud (scion) of a superior quality plant with another plant that has roots (root stock) and belongs to the same species.
    • Process: Chisel off a bud with bark from a superior plant (scion). Peel off bark from the root stock where the bud will be inserted. Attach the scion with a polythene tape, keeping the bud exposed. Once the bud grows, remove the upper portion of the stock.
    • Advantages: Higher productivity, thicker latex (for rubber), quality saplings at reasonable prices.
• Hybridization: The method of producing hybrid seeds by artificially pollinating two plants with different qualities but belonging to the same species.
  • Process (Artificial Pollination): Remove stamens from flowers to prevent self-pollination. Wrap the flower. Collect pollen grains from a plant of the same species with different qualities using a brush. Deposit pollen on the stigma of the chosen flower. Wrap the flower again. This is done immediately after blooming.
  • Cross-pollination is preferred to combine qualities of two plants.
  • Hybrid Seeds Examples: Chilli (Ujjwala, Jwalamukhi), Pea (Jyothika, Bhagyalakshmi), Paddy (Pavithra, Annapoorna), Coconut (Chandralaksha, Chandrasankara), Lady’s finger (Salkeerthi, Kiran).
• Agricultural Research Centres: Institutions that produce superior quality seeds through hybridization and distribute them to farmers.
  • Kerala Agricultural University (KAU), Mannuthi, Thrissur: Conducts research on crops, animals, birds, and disseminates knowledge.
  • Central Tuber Crops Research Institute (CTCRI), Sreekaryam, Thiruvananthapuram: Focuses on tuber crops.
  • Rubber Research Institute of India (RRII), Kottayam: Develops high-yielding rubber varieties.
  • Central Plantation Crops Research Institute (CPCRI), Kasaragod: Researches coconut, arecanut, and cocoa.
• Factors for Better Yield (Beyond Seeds):
  • Fertile Soil: Requires proper application of fertilizers.
    • Organic Fertilizers: Obtained from organic matter (e.g., cow dung, chicken manure). Required in higher quantity, not harmful to soil, cannot be supplied as a single component.
    • Chemical Fertilizers: Produced industrially (e.g., Urea, NPK mixture, Bonemeal). Required in lesser quantity, excess use destroys soil structure, components can be supplied as per requirement....
    • Mixed Method: Farmers in Kerala often use a mix of more organic and less chemical fertilizers.
    • Microbial Fertilizers: Use microbes (e.g., Pseudomonas, Azospirillum) as fertilizers.
  • Pest Control: Addressing pest infestation.
    • Biological Control: Using friendly insects (e.g., Lady bug, Trichogramma) or animals (e.g., Frog, Mabuya, Calotes, Bug) that feed on pests. Chemical pesticides destroy these agents.
    • Mechanical Control: Removing pests manually or using traps (e.g., basil leaf trap for gold coloured flies, pheromone traps).
    • Pesticides:
      • Chemical Pesticides: Prepared using chemical substances.
      • Organic Pesticides: Less harmful, examples include tobacco decoction, neem oil emulsion, garlic-kanthari (chilli) mixture. Tobacco decoction can be prepared by soaking chopped tobacco in water, filtering, and mixing with washing soap, then diluting and spraying.
• Weed Control: Methods include application of weedicides and manual removal.
• Artificial Intelligence (AI) in Agriculture: Technology used for pest detection and destruction with lasers, which is environment-friendly.
• Agricultural Sectors: Agriculture involves more than just growing plants.
  • Sericulture: Rearing silkworms.
  • Floriculture: Growing flowers.
  • Apiculture: Rearing honeybees.
  • Pisciculture: Rearing fishes.
  • Livestock Rearing: Rearing cattle.
  • Poultry Farming: Rearing poultry.
  • Mushroom Culture: Cultivating mushrooms.
  • Cuniculture: Rearing rabbits.

Chapter 2: Acids and Bases

• Indicators: Substances that help to identify acids and bases by changing their colour.
  • Pathimugam Water: A pink liquid that turns yellow in the presence of acidic substances like vinegar, lemon juice, or tamarind water....
  • Litmus Paper: A dye from lichens.
    • Blue Litmus: Turns red in acids.
    • Red Litmus: Turns blue in bases.
  • Natural Indicators:
    • Red Hibiscus Flower: Rubbed on white paper, it can be used instead of blue litmus paper (turns red in acidic liquids). If it turns red, it can then be used instead of red litmus paper.
    • Turmeric: An indicator for bases; turns colour when soap solution or baking powder solution is added.
    • Other coloured plant parts like red spinach, blue clitoria, red cabbage, beetroot can also act as indicators.
  • Laboratory Indicators:
    • Phenolphthalein: Changes colour in acids and bases.
    • Methyl Orange: Changes colour in acids and bases.
    • Universal Indicator: A mixture of many indicators, gives different colours based on nature and concentration of acid/base.
• Acids:
  • Definition: Substances that turn blue litmus into red.
  • Properties: Have a sour taste. React with metals to produce hydrogen gas.
  • Examples in Food Items:
    • Lactic acid: Buttermilk, Curd.
    • Acetic acid: Vinegar.
    • Citric acid: Lemon.
    • Tartaric acid: Tamarind.
    • Malic acid: Apple.
    • Ascorbic acid (Vitamin C): Gooseberry.
    • Oxalic acid: Tomato.
  • Examples in Laboratories: Hydrochloric acid, Nitric acid, Sulphuric acid, Acetic acid.
  • Uses:
    • Acetic acid (Vinegar): Used in pickles, food preservation.
    • Formic acid: Found in ant bodies; used for thickening latex.
    • Citric acid: Used to make drinks.
    • Sulphuric acid: Used in motor vehicle batteries and manufacturing chemical fertilizers.
    • Nitric acid: Used to make chemical fertilizers, paints, and dyes.
    • Tannic acid: Used to make leather and ink.
    • Carbonic acid: (use not specified but listed as an acid).
• Bases:
  • Definition: Substances that turn red litmus into blue.
  • Properties: Have an alkaline taste (e.g., soap, baking soda). Feel slippery to the touch (e.g., soap water, baking soda solution, ash suspension, lime water).
  • Examples in Laboratories: Calcium hydroxide (Lime), Sodium hydroxide (Caustic soda), Potassium hydroxide (Caustic potash), Aluminium hydroxide, Magnesium hydroxide....
  • Uses:
    • Calcium hydroxide: Glass manufacturing, reducing soil acidity.
    • Sodium hydroxide: Making soap, paper, and rayon.
    • Potassium hydroxide: Making soft soap.
    • Aluminium hydroxide, Magnesium hydroxide: Used in medicines (antacids).
• Acidity (in humans): Enhanced production of hydrochloric acid in the stomach can cause acidity, leading to abdominal pain, heartburn, nausea, and constipation. Antacids are prescribed to neutralize this.
• Safety Precautions with Chemicals: Avoid spilling on body parts, do not touch, smell, or taste, use droppers, use holders for test tubes. Strong acids can cause burns; first aid is to pour cold water on affected area.
• Soap Making: Ingredients include caustic soda, coconut oil, water, sodium silicate, stone powder, color, and perfume. Caustic soda dissolves in water releasing heat. The solution is mixed with coconut oil, then sodium silicate and stone powder are added for hardness and quantity. Color and perfume are added, and the mixture is stirred until thick, then poured into a mould and allowed to solidify for two weeks.

Chapter 3: The World of Electricity

• Electricity as Energy: Electricity is a form of energy that can be easily converted into other forms.
• Sources of Electricity: Devices that provide electricity.
  • Electric Cells: Convert chemical energy into electrical energy. Electrical energy is stored as chemical energy and converted when used.
    • Battery: An arrangement of more than one cell connected into a single unit. Cells can be connected in series for more electricity.
    • Rechargeable Cells: Can be recharged and reused (e.g., mobile phone batteries).
    • Non-rechargeable Cells: Cannot be reused once charge is depleted (e.g., clock cells).
  • Generators: Produce electricity using energy from fuels like petrol, kerosene, diesel. Convert chemical energy (from fuel) to mechanical energy, then to electrical energy....
  • Solar Cells: Devices that convert solar energy into electrical energy. Solar panel is a combination of two or more solar cells.
  • Hydroelectric Power Stations: Use the energy from water falling from a height to rotate turbines connected to generators. Major source of electricity in Kerala (e.g., Idukki). Merits include lower cost of fuel and less pollution compared to diesel generators.
  • Other Power Generation: Coal, diesel (thermal power stations), wind (windmills), tidal waves, nuclear energy (nuclear power stations).
• Lighting Devices (Bulbs):
  • Filament bulb.
  • Compact Fluorescent Lamp (CFL): Requires less energy than filament lamps, but less common now.
  • Light Emitting Diode (LED): Helps save energy considerably, requires less energy than CFLs. New generation LED bulbs are constantly invented.
  • LED Module: An arrangement of more than one LED bulb in a strip.
• Electric Circuit: An arrangement that passes electricity from an electric source to a device.
  • Components: Requires at least an electric source, connecting wire, and an electric device.
  • Closed Circuit: A complete circuit where electric devices can work.
  • Open Circuit: An incomplete circuit where electric devices cannot work.
  • Switch: A device used to make a circuit closed (on) or open (off) as required.
  • Circuit Symbols: Standardized signs used to indicate components (e.g., conducting wire, switch, cell, battery, bulb, motor, LED, buzzer).
• Flow of Electricity:
  • Conductors: Substances that allow electricity to pass through them. Examples: Iron, gold, copper, steel, graphite, water, and all metals.
  • Insulators: Substances that do not allow electricity to pass through them. Examples: Dry wooden block, paper, plastic, cloth.
  • Safety: Parts of electrical appliances that are touched are made of insulators. Do not operate a switch with a wet hand because water is a conductor, increasing the risk of shock.
• Electric Shock: Occurs when electric current passes through the body, which is an electric conductor due to water in living cells.
  • Causes: Contact with broken power lines or uninsulated circuits.
  • Dangers: Can cause severe burns, cardiac arrest (major reason for death).
  • Precautions: Using good quality devices, not removing plug without switching off, not changing bulb when switch is on, using wires with proper insulation, not turning on switch with wet hands, not repairing devices when switches are on, removing fan after main switch off, using footwear while ironing.
  • First Aid for Electric Shock:
    1. Disconnect electric contact immediately (switch off, remove fuse). If not possible, separate the person using a dry wooden stick or good insulator.
    2. Do not touch the person experiencing the shock directly.
    3. If heart failure, perform chest compressions.
    4. If breathing stops, give artificial respiration and keep the body warm.
    5. Take the person to a hospital if severe.
• Lightning: Caused by the transfer of very high electrical charge in clouds to nearby clouds or the earth, resulting in powerful electric currents.
• Energy Conservation: Preventing wastage of electricity is crucial because increased consumption requires more fuel for generation.

Chapter 4: When Light Reflects

• Light Transmission:
  • Transparent Objects: Transmit light very well, allowing clear vision through them. Examples: Window glass, pure water, air, clear water....
  • Translucent Objects: Transmit light partially, making objects appear blurred. Examples: Butter paper, scratched glass piece, oiled paper, polythene cover, turbid water, fog, mobile phone screen guard....
  • Opaque Objects: Do not transmit light at all. Examples: Wooden block, cloth, white paper, black chart paper, coin, mirror, marble, soil, tiles, stone, hardboard....
• Modifying Transparency: A transparent glass sheet can be made translucent or opaque by sooting it. Pure water can be made translucent by adding ink, and air can be made translucent by adding incense stick smoke.
• Reflection of Light: The returning of light when it strikes an object.
  • Regular Reflection: Occurs when light falls on smooth surfaces and reflects with regularity. This allows clear images. Examples: Mirrors, smooth tiles, new steel plates, polished furniture, stagnant water....
  • Diffused Reflection (Irregular Reflection): Occurs when light falls on rough surfaces and gets scattered in different directions. This does not form clear images. Examples: Sandpaper, paper, wooden block, walls of a home (allowing light inside during daytime).... Rough surfaces cannot reflect light well because their unevenness causes scattered reflection.
• Key Terms in Reflection:
  • Incident Ray: The ray of light falling on the mirror.
  • Point of Incidence: The point where the incident ray falls on the mirror.
  • Normal: A line drawn perpendicular (90°) to the mirror at the point of incidence.
  • Reflected Ray: The light ray reflecting from the mirror.
  • Angle of Incidence: The angle between the incident ray and the normal.
  • Angle of Reflection: The angle between the reflected ray and the normal.
• Laws of Reflection:
  1. The angle of incidence and the angle of reflection are equal.
  2. The incident ray, the reflected ray, and the normal at the point of incidence are all on the same plane.
• Light and Sight:
  • We see an object when light coming from a source falls on that object, gets reflected, and then reaches our eyes.
  • We see a source of light when the light from it reaches our eyes directly.
• Plane Mirror and Image Characteristics:
  • Plane Mirror: A mirror with a flat surface.
  • Lateral Inversion: The phenomenon where the left side of an object appears as the right side of the image, and vice-versa, in a plane mirror. This is why words like "AMBULANCE" are written in reverse on the front of the vehicle.
  • Distance to the Image: In a plane mirror, the distance between the object and the mirror is equal to the distance between the image and the mirror.
  • Size of the Image: In a plane mirror, the size of the object will be equal to the size of the image.
• Multiple Reflection: A large number of images are formed when a light source is placed between two parallel plane mirrors. Examples: Barber shops.
  • Angle between Mirrors and Number of Images: The number of images formed (N) when two plane mirrors are placed at an angle (x) to each other is given by the formula: N = (360/x) - 1. As the angle between mirrors decreases, the number of images increases, and vice-versa.
• Optical Devices based on Reflection:
  • Kaleidoscope: Uses three plane mirror pieces fixed in a triangular pattern. When colored bangle pieces or beads are placed inside, it creates different, beautiful patterns due to multiple reflection when tilted.
  • Periscope: Uses two plane mirrors fixed at specific angles inside a tube (e.g., cardboard box). Allows viewing objects that are not in the direct line of sight (e.g., seeing over obstacles, for submarines, soldiers in trenches).... It produces an upper view when looking through the lower end.
• Light Pollution: Excess artificial light at night that disrupts the natural environment.
  • Harmful Effects: Harmful to many nocturnal organisms (e.g., owls) that hunt in the dark. Also prevents humans from seeing many sky views that are only visible on clear nights.

Chapter 5: Human Body: A Wonder - Digestion and Respiration

Part 1: Digestion

• Nutrition: The process by which organisms obtain and utilize food. It has 5 stages:
  1. Ingestion: Taking food into the body, primarily through the mouth.
  2. Digestion: The process of breaking down food into simpler forms.
  3. Absorption: Nutrients from digested food entering the blood.
  4. Assimilation: Absorbed nutrients becoming part of the body.
  5. Egestion: Elimination of undigested digestive waste from the body.
• Ingestion (Mouth):
  • Food mixes with saliva.
  • Lips, tongue, and teeth play roles in ingestion.
  • Teeth: Used to masticate (chew) food. Structure is adapted for biting, chewing, and grinding.
    • Enamel: The outermost and hardest layer of the tooth.
    • Milk Teeth (Deciduous Teeth): First set of 20 teeth (10 upper, 10 lower) in infants, appearing around six months.
    • Permanent Teeth: Replace milk teeth. If broken or fall off, new teeth do not grow.
    • Types of Permanent Teeth (Adult):
      • Incisors (8): Four in upper, four in lower jaw, at the front. Used for biting and tearing.
      • Canines (4): Two in upper, two in lower jaw, adjacent to incisors. Used for biting and tearing. Carnivores have highly developed canines for tearing meat.
      • Premolars (8): Two on both sides in upper and lower jaws, adjacent to canines. Used for chewing and grinding.
      • Molars (12): Six in upper, six in lower jaw, near premolars at the back. Used for chewing and grinding. Herbivores have well-developed premolars and molars for masticating food.
    • Tooth Decay (Dental Caries): Caused by lactic acid, produced by bacteria feeding on food particles stuck between teeth. Lactic acid reacts with enamel (a calcium compound), damaging teeth over time.
    • Dental Care: Clean mouth thoroughly after food, especially sweets. Brush teeth in the morning before breakfast and at night after dinner.
  • Tongue: Contains taste buds, helps in swallowing, and moves food inside the mouth for chewing.
  • Saliva: Produced by salivary glands; plays an important role in digestion (e.g., mixing with food).
• Oesophagus: A long muscular tube connecting the mouth to the stomach. Food moves through it by peristalsis (wave-like muscular movements).
• Stomach:
  • Food remains for 4 to 5 hours.
  • Peristaltic movement of the stomach wall turns food into a paste.
  • Gastric juice (produced by stomach glands) and a small amount of hydrochloric acid are secreted.
  • Hydrochloric acid helps in protein digestion and pathogen destruction.
• Small Intestine:
  • Human small intestine is five to six meters long.
  • Digestion is completed here.
  • Bile (from the liver) and pancreatic juice (from the pancreas) mix with partially digested food in the first part.
  • Absorption of nutrients also takes place here.
  • Villi: Small finger-like projections on the wall of the small intestine through which nutrients are absorbed into the blood.
• Large Intestine: After nutrient absorption, digestive residues move here. Water and some salts are absorbed from the digestive waste.
• Rectum and Anus: Digestive waste is stored in the rectum and then egested through the anus.
• Nutrition in Other Organisms: Single-celled organisms like Amoeba also undergo all five stages of nutrition: ingestion, digestion, absorption, assimilation, and egestion.

Part 2: Respiration

• Respiration: The process through which organisms receive oxygen from their environment and eliminate carbon dioxide.
• Human Respiration:
  • Breathing: The process of taking air in and out. Humans cannot take oxygen from water like fish due to different respiratory systems.
  • Inhalation: Taking air into the lungs.
    • Mechanism: Diaphragm contracts and flattens slightly. Rib cage lifts upwards. The volume of the thoracic cavity increases. Atmospheric air enters the lungs, and the lungs expand.
  • Exhalation: Movement of air from the lungs to the outside.
    • Mechanism: Diaphragm relaxes and returns to its previous dome-shaped position. Rib cage moves down. The volume of the thoracic cavity decreases, and lungs contract. Air from the lungs moves out.
  • Respiratory Tract: The air passage from nostrils to lungs. Pathway: Nostrils → Trachea → Bronchi → Bronchioles → Alveoli.
  • Composition of Inhaled vs. Exhaled Air:
    • Oxygen: Decreases from 21% (inhaled) to 15% (exhaled).
    • Carbon Dioxide: Increases from 0.04% (inhaled) to 4% (exhaled).
    • Moisture: Increases from 0.96% (inhaled) to 3% (exhaled).
    • Nitrogen: Remains constant at 78%.
    • Conclusion: Oxygen is utilized in respiration.
  • Choking (Food in Trachea) First Aid:
    • For adults: Ask the person to cough forcefully. If severe, perform Heimlich maneuver (press firmly on the stomach from behind).
    • For babies: Place the baby face down on your forearm, resting on your thigh. Give forceful blows between the shoulder blades with the palm of your other hand. Seek medical attention if necessary.
• Smoking and Health Issues: Impairs lung function. Carbon, tar, and toxic substances from cigarette smoke remain in the lungs, causing persistent cough. Tobacco contains cancer-causing chemicals.
• Diversity in Respiration (Other Organisms):
  • Earthworm: Respires through moist skin.
  • Fish: Respire through gills.
  • Frog: Uses lungs on land and moist skin underwater.
  • Spider: Respires using book lungs.
  • Paramecium: An aquatic unicellular organism; takes in oxygen dissolved in water and gives out carbon dioxide through its cell membrane.
• Respiration in Plants: Plants also absorb oxygen from the atmosphere and release carbon dioxide. Stomata (fine pores on leaves and tender stems) help in gas exchange.