Sciences

MYP 2 Notes

Substances: Pure and Impure

  • Pure Substance: Contains only one type of particle, either an element or a compound.
    • Examples of elements: Oxygen (O₂), Gold (Au)
    • Examples of compounds: Water (H₂O), Sodium Chloride (NaCl)
    • Properties are consistent, such as fixed melting and boiling points.
  • Impure Substance: Contains more than one type of particle; also called a mixture.
    • Examples: Saltwater (NaCl + H₂O), Air (mixture of gases)
    • Properties can vary depending on the composition.

Atoms

  • Atom: The smallest unit of an element; neutral because the number of protons equals the number of electrons.
  • Ion: A charged particle formed when an atom gains or loses electrons.
    • Cation: Positively charged (lost electrons), e.g., Na⁺
    • Anion: Negatively charged (gained electrons), e.g., Cl⁻

Elements

  • Symbols: One or two letters, e.g., H (Hydrogen), O (Oxygen), Na (Sodium)
  • Atomic Number: Number of protons in the nucleus; defines the element.
  • Mass Number: Total number of protons and neutrons in the nucleus.
  • Isotopes: Atoms of the same element with different numbers of neutrons, e.g., Carbon-12 and Carbon-14.

Periodic Table

  • Groups: Vertical columns; elements in the same group have similar chemical properties and the same number of valence electrons.
  • Periods: Horizontal rows; properties gradually change across a period as the atomic number increases.
  • Arrangement: Elements are arranged by increasing atomic number.
  • Metals, Non-metals, and Metalloids: Different regions of the table indicate general properties such as conductivity, malleability, and reactivity.

Compounds

  • Valency: The combining capacity of an element; indicates how many electrons it gains, loses, or shares.
  • Naming Compounds:
    • Metal + Non-metal (ionic compounds): e.g., Sodium Chloride (NaCl)
    • Non-metal + Non-metal (covalent compounds): e.g., Carbon Dioxide (CO₂)
    • Other common compounds: Oxides (CO, CO₂), Hydroxides (NaOH), Sulphates (CuSO₄), Carbonates (CaCO₃)
  • Chemical Reactions: Writing word and symbol equations.
    • Example (word equation): Hydrogen + Oxygen → Water
    • Example (symbol equation): 2H₂ + O₂ → 2H₂O

Mixtures

  • Mixtures contain more than one type of particle but are not chemically combined.
  • Methods of separating mixtures:
    • Evaporation: Removing a liquid from a solution to leave the solid behind.
    • Distillation: Separating liquids with different boiling points.
    • Fractional Distillation: Separating liquids in a mixture into fractions based on boiling points (e.g., crude oil).
    • Chromatography: Separating substances based on solubility or movement through a medium (e.g., inks, dyes).

Introduction to Acids and Alkalis

  • Properties of Acids:
    • Sour taste (e.g., lemon juice, vinegar)
    • Turns blue litmus paper red
    • pH less than 7
    • Conduct electricity in aqueous solution (electrolytes)
    • Reacts with metals to produce hydrogen gas (e.g., Zn + HCl → ZnCl₂ + H₂)
  • Properties of Alkalis (Bases):
    • Bitter taste (e.g., soap solution, baking soda solution)
    • Turns red litmus paper blue
    • pH greater than 7
    • Conduct electricity in aqueous solution (electrolytes)
    • Feel soapy or slippery
  • pH Scale and Indicators:
    • The pH scale ranges from 0–14 and measures how acidic or alkaline a solution is.
    • Acidic: pH < 7, Neutral: pH = 7, Alkaline: pH > 7
    • Common indicators:
      • LITMUS: Red in acid, blue in alkali
      • PHENOLPHTHALEIN: Colourless in acid, pink in alkali
      • METHYL ORANGE: Red in acid, yellow in alkali
  • Neutralisation Reaction:
    • Definition: A chemical reaction between an acid and an alkali to produce a salt and water.
    • General equation: Acid + Alkali → Salt + Water
    • Examples:
      • Hydrochloric acid + Sodium hydroxide → Sodium chloride + Water (HCl + NaOH → NaCl + H₂O)
      • Sulphuric acid + Potassium hydroxide → Potassium sulphate + Water (H₂SO₄ + 2KOH → K₂SO₄ + 2H₂O)

Biodiversity, Food Chain & Food Web

  • Biodiversity: Variety of life in an ecosystem
  • Food chain: Linear sequence showing energy transfer from one organism to another
  • Food web: Interconnected food chains showing complex feeding relationships

Energy Flow & Trophic Levels

  • Energy Flow: Energy in ecosystems originates from the Sun and passes through living organisms in a specific order:
    • Sun → Producers → Consumers → Decomposers
    • Energy is lost at each stage, mainly as heat, so less energy is available at higher trophic levels.
  • Trophic Levels: Each level in a food chain or food web represents a trophic level:
    • Producers (Autotrophs): Organisms that make their own food via photosynthesis, e.g., plants, algae, phytoplankton.
    • Primary Consumers (Herbivores): Organisms that eat producers, e.g., rabbits, cows, caterpillars.
    • Secondary Consumers (Carnivores/Omnivores): Organisms that eat primary consumers, e.g., snakes, foxes, frogs.
    • Tertiary Consumers (Top Predators): Organisms at the top of the food chain that eat secondary consumers, e.g., eagles, lions, sharks.
    • Decomposers: Organisms that break down dead plants and animals, recycling nutrients back into the soil, e.g., bacteria, fungi, earthworms.
  • Food Chains vs Food Webs:
    • Food Chain: A linear sequence showing who eats whom.
    • Food Web: A network of interconnected food chains showing multiple feeding relationships.
  • Energy Pyramids: Shows energy decrease at each trophic level:
    • Producers at the base have the most energy.
    • Energy decreases as it moves up: Primary → Secondary → Tertiary consumers.
    • Typically, only 10% of energy is passed to the next level (10% rule).

Ecological Pyramids

  • Types of Ecological Pyramids:
    • Number Pyramid: Shows the number of organisms at each trophic level. Example: Many grass plants support fewer herbivores and even fewer carnivores.
    • Biomass Pyramid: Shows the total mass of living material at each trophic level. Measured in grams per square meter (g/m²).
    • Energy Pyramid: Shows the energy available at each trophic level. Energy decreases at higher levels (10% of energy is passed to the next level).
  • Energy decreases as you move up trophic levels because energy is lost as heat, used for metabolism, or not consumed.

Management of Natural Resources

  • Conserving natural resources is essential to maintain ecological balance and ensure sustainability for future generations.
  • Methods of Resource Management:
    • Afforestation: Planting trees to restore forests, prevent soil erosion, and absorb carbon dioxide.
    • Water Conservation: Rainwater harvesting, drip irrigation, reducing wastage, and protecting water sources.
    • Sustainable Agriculture: Crop rotation, organic farming, and reducing chemical fertilizers/pesticides to protect soil and water.

Human Activities Impact on Environment

  • Major human activities affecting the environment:
    • Overpopulation
    • Industrialisation
    • Urbanisation
    • Deforestation
  • Pollution Types:
    • Air pollution: Smoke, industrial emissions, vehicle exhaust
    • Water pollution: Industrial discharge, sewage, agricultural runoff
    • Land pollution: Dumping of solid waste, pesticides, deforestation effects
  • Causes and Effects:
    • Air: Acid rain, smog, respiratory problems, effects on plants and animals; living indicators include lichens and mosses.
    • Water: Eutrophication (excess nutrients causing algal blooms), bioaccumulation (toxins building in organisms), biomagnification (toxins increase up the food chain).
    • Land: Soil degradation, deforestation, loss of habitat, contribution to global warming, increased carbon footprint.

Waves

  • Types of Waves:
    • Longitudinal Waves: The particles of the medium vibrate parallel to the direction of wave travel. Example: Sound waves in air, compression waves in springs.
    • Transverse Waves: The particles of the medium vibrate perpendicular to the direction of wave travel. Example: Water waves, light waves, waves on a string.
  • Wave Properties:
    • Wavelength (λ): Distance between two consecutive crests or troughs.
    • Frequency (f): Number of waves passing a point per second (measured in Hertz, Hz).
    • Amplitude: Maximum displacement of particles from the rest position; related to wave energy.
    • Crest: Highest point of a transverse wave.
    • Trough: Lowest point of a transverse wave.
    • Speed of wave (v): Distance travelled per unit time. v = frequency × wavelength (v = f × λ).

Classification of Waves

  • Mechanical Waves: Require a medium (solid, liquid, or gas) to travel. Energy is transferred through particle vibration.
    • Examples: Sound waves, seismic waves, waves on a rope or spring.
  • Electromagnetic Waves: Do not require a medium; can travel through a vacuum.
    • Examples: Light, radio waves, microwaves, X-rays.
    • All electromagnetic waves travel at the speed of light in a vacuum (~3 × 10⁸ m/s).

Sound

  • Making sound waves: Vibrations in a medium
  • Speed of sound depends on medium (fastest in solids)
  • Detecting sound:
    • Amplitude → Loudness
    • Frequency → Pitch (example: musical instruments)
  • Types of sound waves:
    • Ultrasound: Above human hearing (>20 kHz)
    • Infrasound: Below human hearing (<20 Hz)

Light

  • Sources of Light:
    • Luminous: Produce their own light (e.g., Sun, electric bulb, firefly)
    • Non-luminous: Do not produce their own light; visible due to reflection (e.g., Moon, planets, objects illuminated by sunlight)
  • Electromagnetic Waves: Light is an EM wave; can travel through vacuum; part of the EM spectrum.
    • Applications: Communication (radio, TV, internet), medical imaging (X-rays), cooking (microwaves), lasers
  • Properties of Light:
    • Reflection: Bouncing back of light from a surface
    • Refraction: Bending of light when it passes from one medium to another
    • Dispersion: Splitting of white light into its component colors (spectrum) through a prism

Reflection of Light

  • Types:
    • Regular Reflection: From smooth surfaces like mirrors; produces clear images
    • Irregular Reflection: From rough surfaces; scatters light, producing no clear image
  • Applications: Periscopes, kaleidoscopes, rear-view mirrors, solar panels

Refraction of Light

  • Refractive Index: Measure of bending of light in a medium; higher index = greater bending
  • Critical Angle & Total Internal Reflection (TIR):
    • Critical Angle: Minimum angle of incidence for TIR to occur
    • TIR: Light reflects completely inside a denser medium; no refraction
    • Applications of TIR: Optical fibers (communications), periscopes, binoculars, prism-based instruments
  • Dispersion: Prism splits white light into rainbow colors; occurs because different colors have different speeds in glass
  • Formation of Rainbow: Sunlight refracted, internally reflected, and dispersed in raindrops, producing spectrum of colors in the sky
  • Mirages:
    • Optical illusions caused by refraction of light in layers of air with different temperatures
    • Example: Hot desert or road surfaces appear to have water; light bends from cooler air to hotter air near the ground
    • Type of TIR can create inverted or shimmering images
  • Structure of Eye and Function:
    • Cornea: Transparent outer layer; refracts light into the eye
    • Pupil: Regulates amount of light entering
    • Lens: Focuses light onto the retina by changing shape (accommodation)
    • Retina: Contains photoreceptor cells (rods and cones) converting light into electrical signals
    • Optic Nerve: Transmits signals to the brain for interpretation as vision
  • Application of Lasers:
    • Medical: Eye surgery, cutting tissues, dental procedures
    • Industrial: Cutting, welding, measurement
    • Communication: Optical fiber data transmission
    • Scientific: Holography, barcode scanners

Human Ear

  • Outer Ear:
    • Pinna (Auricle): External visible part that collects sound waves and directs them into the ear canal.
    • External Auditory Canal: Channels sound waves to the eardrum; lined with hairs and wax to protect against dust and microbes.
    • Function: Captures sound efficiently and protects inner structures.
  • Middle Ear:
    • Tympanic Membrane (Eardrum): Vibrates in response to sound waves, converting them to mechanical vibrations.
    • Ossicles: Three tiny bones that amplify sound vibrations:
      • Malleus (Hammer) – attached to the eardrum
      • Incus (Anvil) – connects malleus to stapes
      • Stapes (Stirrup) – transmits vibrations to the inner ear via the oval window
    • Eustachian Tube: Connects middle ear to the throat; maintains equal air pressure on both sides of the eardrum.
    • Function: Amplifies sound and balances pressure to protect hearing.
  • Inner Ear:
    • Cochlea: Spiral-shaped organ; contains fluid and hair cells (sensory receptors) that convert vibrations into electrical impulses sent to the brain via the auditory nerve.
    • Semicircular Canals: Three looped tubes filled with fluid; detect rotational movement for balance.
    • Vestibule: Central chamber; detects linear motion and gravity for balance.
    • Auditory (Cochlear) Nerve: Carries electrical signals from cochlea to the brain for interpretation as sound.
    • Function: Converts mechanical vibrations to nerve impulses and maintains balance.

Specialized Cells

  • Blood Cells:
    • Red Blood Cells (RBCs): Biconcave shape; contain hemoglobin; transport oxygen from lungs to tissues and carbon dioxide from tissues to lungs.
    • White Blood Cells (WBCs): Part of immune system; defend body against infections.
    • Platelets: Help in blood clotting to prevent excessive bleeding.
  • Root Hair Cells:
    • Found in the roots of plants; long hair-like extensions increase surface area for absorption.
    • Absorb water and mineral salts from the soil and transport them to other parts of the plant.
  • Muscle Cells (Fibres):
    • Specialized for contraction and relaxation to produce movement.
    • Contain many mitochondria to provide energy (ATP) for contraction.
    • Types: Skeletal (voluntary), Cardiac (heart), Smooth (involuntary, in organs).
  • Other Examples of Specialized Cells:
    • Nerve Cells (Neurons): Transmit electrical impulses; long axon and dendrites for communication.
    • Guard Cells: Control opening and closing of stomata in leaves for gas exchange.
    • Ciliated Cells: Line trachea; cilia move mucus and trapped particles out of respiratory tract.

Human Body Organization

  • Cells → Tissues → Organs → Organ Systems → Organism

Cells

  • Definition: The basic structural and functional unit of life; all living organisms are made of cells.
  • Types of Cells:
    • Prokaryotic Cells: Simple cells without a nucleus (e.g., bacteria); have cell membrane, cytoplasm, and genetic material (DNA) free in the cytoplasm.
    • Eukaryotic Cells: Complex cells with a nucleus and organelles; found in plants, animals, fungi, and protists.
  • Plant vs Animal Cells:
    • Plant Cells: Cell wall (rigid structure), chloroplasts (photosynthesis), large central vacuole (storage, turgor pressure).
    • Animal Cells: No cell wall, no chloroplasts, smaller vacuoles; flexible shape for movement.
  • Cell Organelles and Functions:
    • Nucleus: Contains DNA; controls cell activities.
    • Cytoplasm: Jelly-like substance where chemical reactions occur.
    • Cell Membrane: Controls movement of substances in and out of the cell.
    • Mitochondria: Site of cellular respiration; produces energy (ATP).
    • Ribosomes: Protein synthesis.
    • Endoplasmic Reticulum (ER): Rough ER – with ribosomes, protein transport; Smooth ER – lipid synthesis.
    • Golgi Apparatus: Packaging and transport of proteins and lipids.
    • Lysosomes: Contain digestive enzymes to break down waste and foreign particles (mostly in animal cells).
    • Chloroplasts: Site of photosynthesis (plants only).
    • Vacuoles: Storage of water, nutrients, and waste; large central vacuole in plant cells maintains turgor pressure.
  • Cell Functions:
    • Provide structure and support
    • Carry out metabolism
    • Produce energy
    • Respond to stimuli
    • Reproduce to form new cells

Tissues

  • Definition: A group of similar cells that perform a specific function together.
  • Animal Tissues:
    • Epithelium: Covers body surfaces and lines cavities; protects and absorbs substances.
      • Examples: Skin epithelium, lining of the gut, glandular epithelium
    • Connective Tissue: Supports, connects, or separates tissues and organs.
      • Examples: Bone, cartilage, tendons, ligaments, blood
    • Muscle Tissue: Contracts to produce movement.
      • Types: Skeletal (voluntary), Cardiac (heart), Smooth (involuntary, walls of organs)
    • Nervous Tissue: Transmits electrical impulses for communication between body parts.
      • Example: Neurons in the brain and spinal cord
  • Plant Tissues:
    • Meristematic Tissue: Undifferentiated cells capable of division; responsible for plant growth.
      • Examples: Apical meristem (tips of roots and shoots), Lateral meristem (stem thickness)
    • Permanent Tissue: Differentiated cells performing specific functions.
      • Simple Permanent Tissues:
        • Parenchyma – storage and photosynthesis
        • Collenchyma – flexible support
        • Sclerenchyma – hard support (fibers and sclereids)
      • Complex Permanent Tissues:
        • Xylem – conducts water and minerals; provides support
        • Phloem – transports food (sugars) throughout the plant

Organs

  • Definition: An organ is a group of different tissues that work together to perform a specific function.
  • Examples of Organs in Animals:
    • Heart: Made of muscle tissue, connective tissue, and epithelial tissue; pumps blood throughout the body.
    • Lungs: Made of epithelial, connective, and muscle tissues; responsible for gas exchange (oxygen in, carbon dioxide out).
    • Stomach: Made of muscle tissue, epithelial tissue, and connective tissue; digests food by mechanical churning and enzyme action.
    • Brain: Made of nervous tissue and connective tissue; controls body activities, senses, and responses.
  • Examples of Organs in Plants:
    • Leaf: Made of epidermis, mesophyll, and vascular tissues; performs photosynthesis and gas exchange.
    • Root: Made of epidermis, cortex, and vascular tissues; absorbs water and minerals and anchors the plant.
    • Stem: Made of epidermis, cortex, vascular tissues, and supporting tissues; transports water, minerals, and food; provides support.
    • Flower: Made of reproductive tissues, petals, and supporting tissues; involved in reproduction and pollination.
  • Function of Organs:
    • Perform specialized tasks necessary for the survival of the organism
    • Work in coordination with other organs to form organ systems

Organs

  • Definition: An organ is a group of different tissues that work together to perform a specific function.
  • Examples of Organs in Animals:
    • Heart: Made of muscle tissue, connective tissue, and epithelial tissue; pumps blood throughout the body.
    • Lungs: Made of epithelial, connective, and muscle tissues; responsible for gas exchange (oxygen in, carbon dioxide out).
    • Stomach: Made of muscle tissue, epithelial tissue, and connective tissue; digests food by mechanical churning and enzyme action.
    • Brain: Made of nervous tissue and connective tissue; controls body activities, senses, and responses.
  • Examples of Organs in Plants:
    • Leaf: Made of epidermis, mesophyll, and vascular tissues; performs photosynthesis and gas exchange.
    • Root: Made of epidermis, cortex, and vascular tissues; absorbs water and minerals and anchors the plant.
    • Stem: Made of epidermis, cortex, vascular tissues, and supporting tissues; transports water, minerals, and food; provides support.
    • Flower: Made of reproductive tissues, petals, and supporting tissues; involved in reproduction and pollination.
  • Function of Organs:
    • Perform specialized tasks necessary for the survival of the organism
    • Work in coordination with other organs to form organ systems

Organ Systems

Cardiovascular (Circulatory) System

  • Definition: The system responsible for transporting blood, nutrients, oxygen, carbon dioxide, and hormones throughout the body.
  • Main Components:
    • Heart: Muscular organ that pumps blood; has four chambers:
      • Right Atrium – receives deoxygenated blood from the body
      • Right Ventricle – pumps deoxygenated blood to the lungs
      • Left Atrium – receives oxygenated blood from the lungs
      • Left Ventricle – pumps oxygenated blood to the body
    • Blood Vessels:
      • Arteries – carry blood away from the heart (usually oxygen-rich)
      • Veins – carry blood toward the heart (usually deoxygenated)
      • Capillaries – tiny vessels where exchange of gases, nutrients, and waste occurs between blood and tissues
    • Blood: Transport medium; components include:
      • Red Blood Cells – carry oxygen
      • White Blood Cells – fight infection
      • Platelets – help in clotting
      • Plasma – transports nutrients, hormones, and waste
  • Blood Circulation:
    • Pulmonary Circulation: Right ventricle → lungs → left atrium; exchanges CO₂ for O₂.
    • Systemic Circulation: Left ventricle → body tissues → right atrium; delivers oxygen and nutrients, collects waste.
  • Functions:
    • Transports oxygen, carbon dioxide, nutrients, hormones, and waste products
    • Maintains body temperature and pH balance
    • Protects against disease via white blood cells
    • Helps in wound healing through clotting (platelets)

Digestive System

  • Definition: The system responsible for breaking down food into smaller molecules that the body can absorb and use for energy, growth, and repair.
  • Main Organs and Their Functions:
    • Mouth: Mechanical digestion by chewing; chemical digestion begins with saliva (contains amylase that breaks down starch).
    • Esophagus: Muscular tube that connects mouth to stomach; uses peristalsis (wave-like contractions) to move food.
    • Stomach: Muscular sac; churns food and mixes it with gastric juice (contains pepsin for protein digestion and hydrochloric acid to kill microbes).
    • Small Intestine: Long coiled tube; main site of chemical digestion and nutrient absorption.
      • Duodenum – receives bile from liver and pancreatic juice from pancreas
      • Jejunum & Ileum – absorption of nutrients into the blood
    • Large Intestine: Absorbs water and minerals; forms feces; houses beneficial bacteria for digestion.
    • Liver: Produces bile (emulsifies fats), detoxifies blood, stores vitamins and glycogen.
    • Gallbladder: Stores and releases bile into small intestine.
    • Pancreas: Produces pancreatic juice with enzymes (amylase, lipase, protease) for digestion; regulates blood sugar with insulin and glucagon.
    • Rectum and Anus: Stores feces and expels it from the body.
  • Process of Digestion:
    • Ingestion – taking in food through the mouth
    • Propulsion – moving food along the digestive tract (swallowing and peristalsis)
    • Mechanical Digestion – chewing and churning
    • Chemical Digestion – breaking down complex molecules with enzymes
    • Absorption – nutrients absorbed into blood or lymph in the small intestine
    • Defecation – removal of indigestible substances as feces
  • Functions:
    • Provides nutrients, vitamins, and minerals for energy, growth, and repair
    • Removes waste materials
    • Supports overall metabolic processes

Nervous System

  • Definition: The system that controls and coordinates body activities and allows the body to respond to internal and external stimuli.
  • Main Components:
    • Brain: Control center of the body; processes information, thoughts, memory, emotions, and coordinates movement.
      • Cerebrum – controls voluntary actions, intelligence, memory, and senses
      • Cerebellum – coordinates balance and muscle movement
      • Medulla Oblongata – controls involuntary functions like heartbeat, breathing, and digestion
    • Spinal Cord: Connects the brain to the body; conducts messages to and from the brain; responsible for reflex actions.
    • Nerves: Bundles of neurons that carry signals between the central nervous system and the rest of the body.
  • Types of Neurons:
    • Sensory Neurons: Carry impulses from receptors (skin, eyes, ears) to the brain and spinal cord.
    • Motor Neurons: Carry impulses from the brain and spinal cord to muscles or glands to trigger action.
    • Interneurons: Found in the brain and spinal cord; connect sensory and motor neurons and process information.
  • Reflex Action:
    • Automatic, fast, and involuntary response to a stimulus to protect the body
    • Reflex Arc: Receptor → Sensory Neuron → Interneuron → Motor Neuron → Effector (muscle/gland)
  • Functions of Nervous System:
    • Detects changes in the environment (stimuli) and sends messages to the brain
    • Coordinates voluntary and involuntary actions
    • Maintains homeostasis by controlling body functions
    • Enables learning, memory, and decision-making

Muscular System

  • Definition: The system responsible for movement of the body, posture, and internal organ function through contraction and relaxation of muscles.
  • Types of Muscles:
    • Skeletal (Voluntary) Muscles: Attached to bones via tendons; responsible for voluntary movements like walking, running, and lifting objects; striated (striped appearance).
    • Cardiac Muscle: Found in the heart; involuntary; striated; contracts rhythmically to pump blood throughout the body.
    • Smooth (Involuntary) Muscles: Found in walls of internal organs (stomach, intestines, blood vessels); involuntary; not striated; help in movement of substances inside the body.
  • Structure of Skeletal Muscle:
    • Made up of muscle fibers (cells) bundled together
    • Muscle fibers contain myofibrils composed of actin and myosin filaments
    • Filaments slide past each other to produce contraction
  • Functions of Muscular System:
    • Movement of body parts and internal organs
    • Maintaining posture and body position
    • Stabilizing joints
    • Generating heat during activity to maintain body temperature
  • Muscle Interaction with Skeleton:
    • Muscles work in pairs (antagonistic pairs) – while one muscle contracts, the opposite relaxes
    • Examples: Biceps and Triceps for bending and straightening the arm
  • Germ Layer Reference:
    • Ectoderm: Gives rise mainly to skin, hair, nails, and nervous system (not muscles).
    • Mesoderm: Gives rise to muscles, bones, circulatory system, excretory system, and reproductive organs.
    • Endoderm: Forms lining of digestive tract, respiratory tract, and some glands.

    • Skeletal System

    • Definition: The system that provides support, shape, and protection to the body, allows movement, and produces blood cells.
    • Embryonic Origin:
      • Derived from mesoderm (specifically somites and lateral plate mesoderm)
    • Main Components:
      • Bones: Rigid structures made of calcium, phosphorus, and collagen; classified into:
        • Long bones (e.g., femur, humerus) – support weight and enable movement
        • Short bones (e.g., carpals, tarsals) – provide stability and limited movement
        • Flat bones (e.g., skull, ribs) – protect internal organs
        • Irregular bones (e.g., vertebrae, pelvis) – complex shapes for support and protection
        • Sesamoid bones (e.g., patella) – embedded in tendons to improve leverage
      • Joints: Points where two or more bones meet; allow movement. Types include:
        • Immovable (fibrous) – skull bones
        • Partially movable (cartilaginous) – vertebrae
        • Freely movable (synovial) – shoulder, elbow, knee
      • Cartilage: Flexible connective tissue that cushions joints and supports soft structures (nose, ears).
      • Ligaments: Connect bones to bones; provide stability to joints.
      • Tendons: Connect muscles to bones; transmit force to produce movement.
    • Functions:
      • Supports and gives shape to the body
      • Protects vital organs (brain, heart, lungs)
      • Facilitates movement by providing attachment points for muscles
      • Produces blood cells (in bone marrow)
      • Stores minerals such as calcium and phosphorus

    Balanced Diet and Vitamins

    • Nutrients:
      • Proteins, Carbohydrates, Fats – provide energy and building materials
      • Vitamins and Minerals – regulate body processes
      • Fibre – aids digestion and prevents constipation
    • Malnutrition: Occurs when diet lacks essential nutrients; can lead to stunted growth, weakened immunity, and deficiency diseases.
    • Vitamin Types, Sources, Functions, and Deficiency Diseases:
      • Vitamin A: Sources: Carrots, sweet potatoes, spinach; Functions: Maintains healthy vision, skin, and immune system; Deficiency: Night blindness, dry skin.
      • Vitamin B1 (Thiamine): Sources: Whole grains, nuts, meat; Functions: Helps convert food into energy, supports nervous system; Deficiency: Beri-Beri (weakness, nerve damage).
      • Vitamin B2 (Riboflavin): Sources: Milk, eggs, green leafy vegetables; Functions: Energy metabolism, healthy skin and eyes; Deficiency: Cracks at corners of mouth, skin disorders.
      • Vitamin B3 (Niacin): Sources: Meat, fish, legumes; Functions: Energy production, nerve function; Deficiency: Pellagra (diarrhea, dermatitis, dementia).
      • Vitamin B12: Sources: Meat, eggs, dairy; Functions: Red blood cell formation, nerve health; Deficiency: Pernicious anemia, fatigue, nerve damage.
      • Vitamin C (Ascorbic Acid): Sources: Citrus fruits, tomatoes, bell peppers; Functions: Collagen formation, wound healing, immune system; Deficiency: Scurvy (bleeding gums, weakness, slow wound healing).
      • Vitamin D: Sources: Sunlight, fish oil, fortified milk; Functions: Calcium absorption, bone health; Deficiency: Rickets in children (soft bones), Osteomalacia in adults.
      • Vitamin E: Sources: Nuts, seeds, vegetable oils; Functions: Antioxidant, protects cells; Deficiency: Rare, may cause nerve and muscle damage.
      • Vitamin K: Sources: Green leafy vegetables, cabbage; Functions: Blood clotting, bone health; Deficiency: Easy bruising, excessive bleeding.
    • Deficiency Diseases:
        • Kwashiorkor:
          • Cause: Severe protein deficiency, often in children weaned off breast milk and fed a diet low in protein but high in carbohydrates.
          • Symptoms:
            • Swelling (edema) in legs, feet, and belly due to fluid retention
            • Enlarged liver (fatty liver)
            • Thin, weak muscles
            • Stunted growth and delayed development
            • Changes in hair color and texture
            • Skin problems: dermatitis and patchy pigmentation
            • Irritability and apathy
          • Effects on Body: Weak immune system, increased susceptibility to infections, delayed wound healing, and in severe cases, can be fatal.
        • Marasmus:
          • Cause: Severe deficiency of calories (energy) and protein, often due to prolonged starvation or famine; can affect all ages but especially infants and young children.
          • Symptoms:
            • Extreme thinness and loss of muscle and fat tissue
            • Weakness and lethargy
            • Stunted growth and delayed development
            • Prominent bones and wrinkled skin
            • Sunken eyes and cheeks
            • Low body temperature and slowed heart rate
          • Effects on Body: Severe weakening of the immune system, vulnerability to infections, organ failure in extreme cases, can be fatal without proper nutrition.

    Electricity

    • Static Electricity:
      • Charging: When certain materials are rubbed together, electrons may be transferred, leaving one object positively charged and the other negatively charged.
      • Discharging: Sudden flow of electric charge from one object to another (e.g., sparks, lightning).
      • Conductors and Insulators:
        • Conductors – allow free movement of electrons (e.g., metals: copper, aluminum)
        • Insulators – do not allow free movement of electrons (e.g., rubber, plastic, glass)
      • Effects of Static Electricity: Can attract small objects, cause sparks, damage electronics; natural example: lightning causes thunder.
      • Reducing Risks: Use of grounding, avoiding flammable materials near sparks, wearing insulating shoes or gloves.
    • Electric Circuits:
      • Components, Symbols, and Diagrams:
        • Power source (battery)
        • Resistors, bulbs, or loads
        • Switches
        • Connecting wires
        • Use of standard symbols to draw circuit diagrams
      • Types of Circuits:
        • Series Circuits:
          • All components are connected in a single path.
          • Current is the same through all components (Itotal = I1 = I2 = …).
          • Voltage divides among components (Vtotal = V1 + V2 + …).
          • If one component fails (e.g., a bulb burns out), the entire circuit stops working.
          • Resistances add up: Rtotal = R1 + R2 + …
          • Example: Traditional Christmas lights (older types) are wired in series.
          • Advantages: Simple design, easy to calculate current.
          • Disadvantages: One faulty component breaks the circuit; voltage divides, so devices may be dimmer.
        • Parallel Circuits:
          • Components are connected in multiple paths (branches).
          • Voltage across each branch is the same (Vbranch = Vtotal).
          • Current divides among branches depending on resistance (Itotal = I1 + I2 + …).
          • If one component fails, other branches continue to work.
          • Total resistance decreases: 1/Rtotal = 1/R1 + 1/R2 + …
          • Example: Household wiring – each appliance works independently.
          • Advantages: Devices operate independently; full voltage supplied to each device.
          • Disadvantages: More complex design; higher current drawn may need thicker wires.
        1. Current (I): Flow of electric charge; measured in amperes (A) using an ammeter; same in series, divided in parallel circuits.
        2. Voltage (V): Energy per unit charge; measured in volts (V) using a voltmeter; divides in series, same across parallel branches.
        3. Resistance (R): Opposition to flow of current; measured in ohms (Ω); affects current according to Ohm’s Law: V = I × R.

      Calculating Resistance

      • Definition: Resistance (R) is the opposition offered by a material to the flow of electric current. Measured in ohms (Ω).
      • Ohm’s Law:
        • V = I × R
        • Where V = voltage (volts), I = current (amperes), R = resistance (ohms)
        • Can be rearranged to calculate:
          • R = V / I
          • I = V / R
      • Resistance in Series Circuits:
        • All resistances add up: Rtotal = R1 + R2 + R3 + …
        • Current is the same through all components.
        • Voltage divides among resistors according to their resistance.
        • Example: R1 = 4 Ω, R2 = 6 Ω → Rtotal = 10 Ω
      • Resistance in Parallel Circuits:
        • Total resistance decreases: 1 / Rtotal = 1 / R1 + 1 / R2 + 1 / R3 + …
        • Voltage is the same across each branch.
        • Current divides among branches inversely proportional to resistance.
        • Example: R1 = 4 Ω, R2 = 6 Ω → 1 / Rtotal = 1/4 + 1/6 = 5/12 → Rtotal = 12/5 = 2.4 Ω
      • Factors Affecting Resistance:
        • Material: Metals have low resistance, insulators high resistance
        • Length of conductor: Longer wires have higher resistance
        • Cross-sectional area: Thicker wires have lower resistance
        • Temperature: Resistance increases with temperature in metals

    Magnetism

    • Types of Magnetic Materials:
      • Ferromagnetic: Strongly attracted to magnets; can become permanent magnets (e.g., iron, cobalt, nickel).
      • Paramagnetic: Weakly attracted to magnets; do not retain magnetism (e.g., aluminum, platinum).
      • Diamagnetic: Weakly repelled by magnets; no permanent magnetism (e.g., copper, bismuth, water).
    • Magnetising and Demagnetising Methods:
      • Single touch: Stroking a magnetic material with one pole of a magnet.
      • Double touch: Stroking the material alternately with both poles of a magnet.
      • Electric method: Passing electric current through a coil (solenoid) to magnetize a material.
      • Demagnetising: Heating, hammering, or applying alternating current can remove magnetism.
    • Magnetic Fields:
      • Invisible regions around a magnet where magnetic forces act.
      • Field lines: Drawn from the North (N) pole to the South (S) pole outside the magnet.
      • Field lines never cross; density indicates strength (closer lines = stronger field).
      • Earth's magnetic field acts like a giant bar magnet: protects Earth from solar wind; compass aligns with it.
    • Types of Magnets:
      • Permanent magnets: Retain their magnetism; used in compasses, fridge magnets, generators.
      • Electromagnets: Made by passing electric current through a coil around a soft iron core; strength depends on current, number of coils, and core material.
      • Applications of electromagnets: Relays, electric bells, cranes for lifting metals, MRI machines.