🔬 Chapter 9 — Life Processes in Animals
Class 7 Science | Curiosity | EduGrown Notes
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🐄 Life Processes in Animals — Nutrition, Digestion, Respiration!
🍽️ Nutrition & Digestion in Animals
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🍽️Nutrition = process of obtaining and using food for energy and growth
🔄Digestion = breaking down complex food into simpler forms that the body can absorb and use
🫀Digestion happens in the alimentary canal — a long tube from mouth to anus
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🔬 Human digestive system — from mouth to anus!
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🐄 Different animals eat different food types
🫁 Journey of Food Through the Digestive System
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| Part | What Happens |
|---|---|
| 👄 Mouth | Teeth crush food (mechanical digestion) | Saliva breaks starch into sugar (chemical digestion) |
| 🌊 Oesophagus (Food pipe) | Moves food to stomach by wave-like motion (peristalsis) |
| 🫙 Stomach | Churns food + mixes with gastric juice (acid + digestive enzymes) → partly digested food |
| 🌿 Small Intestine | Bile from liver + pancreatic juice help complete digestion | Nutrients absorbed into blood here! |
| 💧 Large Intestine | Absorbs water from undigested food | Forms semi-solid waste |
| ⬇️ Anus | Waste (faeces) excreted out |
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🍽️ Different types of animals have different nutrition modes!
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🔬 Nutrition varies — herbivores, carnivores, omnivores
🦷 Saliva & Teeth — First Steps in Digestion
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🦷Teeth crush and chew food into smaller pieces — Mechanical digestion
💧Saliva contains a digestive juice (salivary amylase) that breaks starch into sugar — Chemical digestion
🍚That's why chapati/rice tastes sweet after chewing for 30–60 seconds!
🧪Test: Iodine + starch = blue-black colour | Iodine + chewed rice = no blue-black (starch broken down!)
💨 Respiration in Animals
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💨Respiration = process of releasing energy from food (glucose) in cells using oxygen
🧪Equation: Glucose + Oxygen → Carbon dioxide + Water + Energy!
🫁Breathing ≠ Respiration! Breathing = taking air in/out | Respiration = chemical process in cells
🌬️ Aerobic Respiration
→Uses oxygen — occurs in most animals
→Glucose + O₂ → CO₂ + H₂O + Energy
→Releases more energy
⚡ Anaerobic Respiration
→Without oxygen — in yeast, some bacteria, muscles during intense exercise
→Glucose → Lactic acid + Energy (muscles get tired!)
⭐ Quick Summary
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📝 Key Points
🍽️Digestion: Mouth → Oesophagus → Stomach → Small Intestine → Large Intestine → Anus
🦷Saliva breaks starch to sugar | Small intestine = main site of nutrient absorption
💨Aerobic respiration: Glucose + O₂ → CO₂ + H₂O + Energy
🧪Iodine test: starch = blue-black | No starch = no colour change (saliva broke it down!)