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AUTOTROPHS (make their own food):
┌─────────────────────────────────┐
│ Green Plants │
│ Sunlight + CO₂ + Water │
│ ↓ Chlorophyll │
│ Glucose + Oxygen │
└─────────────────────────────────┘
HETEROTROPHS (depend on others):
├── Herbivores (eat plants): Cow, rabbit
├── Carnivores (eat animals): Lion, wolf
├── Omnivores (eat both): Humans, crow
├── Parasites: Cuscuta (on plants), lice (on animals)
└── Saprotrophic: Fungi, bacteria (decompose dead matter)
SUN
☀
│ Light energy
▼
┌─────────────┐
CO₂ ──→ │ LEAF CELL │ ──→ O₂ (released)
│ │
H₂O ──→ │ Chloroplast │
(roots) │ (green) │
└─────────────┘
│
▼
GLUCOSE (C₆H₁₂O₆)
stored as starch
Equation:
6CO₂ + 6H₂O ──sunlight/chlorophyll──→ C₆H₁₂O₆ + 6O₂
UPPER EPIDERMIS (protective layer)
────────────────────────────────────────────
[Palisade cells — tightly packed, many chloroplasts]
████████████████████████████████████████████████
────────────────────────────────────────────
[Spongy cells — loosely packed, air spaces]
● ● ● ● ● ● ● ● ● ● ● ● ●
────────────────────────────────────────────
LOWER EPIDERMIS
[Stomata — tiny pores for gas exchange]
○ ○ ○ ○
Guard Cells control stomata opening:
Open: CO₂ enters, O₂ exits, water vapor exits
Closed: When water is scarce, prevent wilting
| Plant | Mode | How it feeds | |-------|------|-------------| | Cuscuta (Amarbel) | Parasite | Twines around host, extracts food | | Pitcher Plant | Insectivorous | Traps and digests insects (N-poor soil) | | Rhizobium in legumes | Symbiotic | Bacteria fixes N₂, plant provides shelter |
MOUTH
│ Teeth (chewing), Saliva (amylase breaks starch)
▼
OESOPHAGUS (food pipe)
│ Peristalsis — wave-like muscle contractions move food
▼
STOMACH
│ Gastric juice (HCl + pepsin) → breaks proteins
│ Churning → turns food to chyme
▼
SMALL INTESTINE (6-7 meters)
│ ┌─ Duodenum: bile (from liver) + pancreatic juice
│ │ Bile emulsifies fats; Pancreatic juice digests all 3
│ └─ Ileum: Villi absorb nutrients into blood
▼
LARGE INTESTINE (1.5 meters)
│ Absorbs water, forms solid waste (feces)
▼
RECTUM → ANUS (waste expelled)
Small intestine wall — inside view:
≋≋≋≋≋≋≋≋≋≋≋≋≋≋≋≋≋≋≋≋≋≋≋≋≋ (wall folds)
↑ ↑ ↑ ↑ ↑
Villus Villus Villus Villus
Each Villus:
┌────────┐
│ ░░░░░░ │ ← Thin wall (1 cell thick)
│ ║Blood║ │ ← Blood capillaries inside
│ vessel │
└────────┘
Function: Increase surface area for maximum absorption
┌───┐
│ ╪ │ ← Scale markings (°C)
│ ║ │
│ ║ │ ← Glass tube (narrow bore)
│ ║ │
│ ║ │
100°C─┼─║─
│ ║ │ ← Mercury/liquid expands with heat
37°C─┼─║─
│ ║ │
0°C─┼─║─
│ │
└───┘
← Bulb (mercury reservoir)
Normal body temp: 37°C (98.6°F)
CONDUCTION (solids):
Heat travels through material — particle to particle
🔥─────────────────────────────────→ Heat
Hot end Metal rod Cold end
Good conductors: Metals (iron, copper, silver)
Poor conductors (insulators): Wood, plastic, air, glass
CONVECTION (liquids and gases):
Hot fluid rises, cold fluid sinks → creates circular current
┌──────────────────┐
│ ← Cold water │
│ sinks │ ← Hot water
│ ↑ │ rises
│ 🔥 flame │ │
└──────────────────┘
Examples: Sea breeze, room heating, boiling water
RADIATION (no medium needed):
Heat travels as electromagnetic waves
☀ ───(heat waves)──→ 🌍
Sun (through vacuum of space) Earth
Examples: Sunlight, campfire warmth, electric heater
ACIDS NEUTRAL BASES (ALKALIS)
0──1──2──3──4──5──6──7──8──9──10──11──12──13──14
│ │ │
Most acidic Water Most alkaline
(Battery acid) pH=7 (Caustic soda)
Common examples:
pH 0-2: Battery acid (H₂SO₄), Stomach acid (HCl)
pH 3: Vinegar, Lemon juice
pH 5: Rain water (slightly acidic, CO₂ dissolved)
pH 7: Pure water (neutral)
pH 8: Baking soda solution
pH 10: Milk of magnesia
pH 13: Bleach, caustic soda (NaOH)
| Indicator | In Acid | In Neutral | In Base | |-----------|---------|-----------|---------| | Litmus (Red) | Red | Red | Blue | | Litmus (Blue) | Red | Blue | Blue | | Turmeric | Yellow | Yellow | Red | | China Rose | Pink | Pink | Green | | Phenolphthalein | Colorless | Colorless | Pink |
ACID + BASE → SALT + WATER
(H⁺ ions) (OH⁻ ions) (neutral)
Example:
HCl + NaOH → NaCl + H₂O
(Hydrochloric (Sodium (Common (Water)
acid) hydroxide) salt)
Real-life uses of neutralization:
• Antacids (base) neutralize excess stomach acid
• Lime (base) added to acidic soil to neutralize it
• Toothpaste (slightly basic) neutralizes mouth acids
• Wasp sting (alkaline) → apply vinegar (acid)
• Bee sting (acidic) → apply baking soda (base)
| Feature | Physical Change | Chemical Change | |---------|----------------|----------------| | New substance? | No | Yes | | Reversible? | Usually yes | Usually no | | Properties change? | No (same substance) | Yes (different substance) | | Examples | Melting ice, dissolving sugar, tearing paper | Burning, rusting, cooking, digestion |
PHYSICAL CHANGE — Ice melting:
ICE → WATER → STEAM
H₂O (solid) H₂O (liquid) H₂O (gas)
Frozen crystals Liquid molecules Free molecules
All are H₂O — only STATE changes
Cooling reverses: steam → water → ice
CHEMICAL CHANGE — Iron rusting:
Fe (iron) + O₂ + H₂O → Fe₂O₃ (iron oxide = rust)
Grey/shiny Red-brown, flaky
CANNOT reverse rusting to get original iron back
WEATHER = Short-term atmospheric conditions (day-to-day)
"Today is hot and humid" → WEATHER
CLIMATE = Long-term average weather pattern (30+ years)
"Rajasthan has hot, dry climate" → CLIMATE
POLAR REGION (Arctic/Antarctic):
Temperature: −40°C to 0°C
Polar Bear:
├── White fur = camouflage in snow
├── Thick fat layer = insulation from cold
├── Small ears = less heat loss
└── Fur on paws = grip on ice, insulation
Penguin:
├── Huddling together = conserve body heat
├── Streamlined body = swimming
└── Thick fat layer under feathers = insulation
TROPICAL RAINFOREST:
Temperature: 25-35°C, heavy rainfall year-round
Toucan:
├── Large beak = reach fruits on thin branches
└── Bright colors = attract mates
Tree Frog:
├── Sticky feet = climb trees
├── Bright colors = warn predators
└── Camouflage green = hide in leaves
AEROBIC RESPIRATION (with oxygen):
Glucose + Oxygen → CO₂ + Water + ENERGY (38 ATP)
C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + Energy
Occurs in: Mitochondria
Products: CO₂, H₂O, lots of energy
ANAEROBIC RESPIRATION (without oxygen):
IN YEAST:
Glucose → Ethanol (alcohol) + CO₂ + small energy
[Used in bread-making, beer brewing]
IN HUMANS (during heavy exercise):
Glucose → Lactic acid + small energy
[Causes muscle cramp/fatigue]
IN SOME BACTERIA:
Various products — used in making yogurt, cheese
NASAL CAVITY
│ (air enters, filters, warms)
TRACHEA (wind pipe)
╱ ╲
LEFT RIGHT
BRONCHUS BRONCHUS
│ │
LEFT RIGHT
LUNG LUNG
(2 lobes) (3 lobes)
│ │
Bronchioles ──────Bronchioles
│ │
Alveoli (air sacs) — Alveoli
Alveoli: Tiny balloon-like sacs where gas exchange occurs
O₂ passes from alveoli → blood (capillaries)
CO₂ passes from blood → alveoli → exhaled
Surface area of all alveoli ≈ 70 m² (tennis court!)
DOUBLE CIRCULATION (in humans):
Pulmonary (lung) circulation:
Right heart → Lungs (O₂ picked up) → Left heart
Systemic circulation:
Left heart → Body organs (O₂ delivered) → Right heart
HEART — 4 chambers:
┌────────────────────────┐
│ Right Atrium (RA) │ Left Atrium (LA) │
│ receives deoxygenated │ receives oxygenated │
│ blood │ blood │
│─────────────────────┼─────────────────│
│ Right Ventricle │ Left Ventricle │
│ pumps to lungs │ pumps to body │
└────────────────────────┘
Blood vessels:
Arteries: carry blood AWAY from heart (thick walls)
Veins: carry blood TO heart (thin walls, valves)
Capillaries: tiny vessels for gas/nutrient exchange
XYLEM: Carries WATER and MINERALS (soil → leaves)
Direction: upward only
Dead cells, form tubes
PHLOEM: Carries FOOD (leaves → all parts)
Direction: up and down
Living cells
Cross section of stem:
┌────────────────────────────┐
│ Epidermis (outer layer) │
│ ┌──────────────────────┐ │
│ │ Cortex │ │
│ │ ┌────────────────┐ │ │
│ │ │ Vascular Bundle│ │ │
│ │ │ [Xylem|Phloem]│ │ │
│ │ └────────────────┘ │ │
│ └──────────────────────┘ │
└────────────────────────────┘
Biology:
Chemistry:
Physics:
Class 7 Science complete notes — nutrition in plants and animals, fibre to fabric, heat, acids & bases, physical and chemical changes, weather & climate, soil, respiration, transportation, reproduction, forests.
44 pages · 1.6 MB · Updated 2026-03-11
Physical change: only form/shape changes, original substance can be recovered (e.g., melting ice, tearing paper). Chemical change: new substance is formed, usually irreversible (e.g., burning wood, rusting iron, cooking food). Indicators of chemical change: new smell, color change, gas produced, heat/light released.
Photosynthesis is the process by which green plants make their own food using sunlight, water, and CO₂. Formula: 6CO₂ + 6H₂O + sunlight → C₆H₁₂O₆ (glucose) + 6O₂. It occurs in chloroplasts (chlorophyll is the green pigment). Sunlight provides energy, water comes from soil via roots, CO₂ enters through stomata.
Aerobic respiration uses oxygen: C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + 38 ATP (energy). Anaerobic respiration occurs without oxygen: in yeast → alcohol + CO₂; in muscles during heavy exercise → lactic acid. Aerobic produces much more energy than anaerobic.
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