Class 7 Science Chapter 9: Life Processes in Animals | Complete NCERT Notes, Human Digestion, Respiration, Alimentary Canal, Activity 9.1 Solved
Complete Chapter 9 Guide: Human Digestive System (Mouth→Oesophagus→Stomach→Small Intestine→Large Intestine), Activity 9.1 Saliva on Starch Iodine Test, Respiration (Alveoli Gas Exchange), Breathing Mechanism (Diaphragm+Ribs), Ruminants (Cow Rumination), Birds Gizzard, Gills in Fish, Oral Hygiene, Lime Water CO2 Test, 25+ Practice Questions & Answers, CBSE Board Exams 2025
Updated: 6 months ago
Life Processes in Animals
Class 7 Science Chapter 9 | Complete NCERT Guide | Nutrition, Digestion, Respiration, Excretion in Animals
Full Chapter Summary & Detailed Notes - Life Processes in Animals
Introduction & Life Processes
All animals (including humans) perform certain essential activities to stay alive. These are collectively called life processes. The four major life processes are:
- Nutrition – taking in food and using it
- Respiration – obtaining and using oxygen to release energy
- Excretion – removal of waste
- Reproduction – producing young ones
This chapter focuses mainly on Nutrition and begins the study of Respiration.
9.1 Nutrition in Animals
Animals cannot make their own food (except a few exceptions); they depend directly or indirectly on plants. Animals show great variety in their feeding habits:
- Bees & sunbirds → suck nectar from flowers
- Infants (humans & many mammals) → feed on mother’s milk
- Snakes (e.g., python) → swallow the prey whole
- Many aquatic animals (e.g., whales, some fish) → filter tiny floating food particles
- Frogs → use sticky tongue to catch insects
Why do we need to digest food?
Food contains complex substances (carbohydrates, proteins, fats). These are large molecules that cannot pass through cell membranes. They must be broken down into simpler, soluble forms (glucose, amino acids, fatty acids) so that the body can absorb and use them for energy, growth and repair.
9.1.1 Digestion in Human Beings – The Alimentary Canal
Digestion takes place inside a long muscular tube called the alimentary canal (or digestive tract) that runs from mouth → anus. Length ≈ 8–10 metres when stretched.
Mouth
- Mechanical digestion: Teeth cut, tear, crush and grind food into smaller pieces → increases surface area.
- Chemical digestion: Saliva (secreted by salivary glands) contains the enzyme salivary amylase (ptyalin) that converts starch → maltose (sugar).
- That is why chapati/rice tastes sweet after chewing for 30–60 seconds.
- Tongue helps in mixing food with saliva and swallowing.
Oesophagus (Food pipe)
Food is pushed down by wave-like muscular contractions called peristalsis. No digestion occurs here.
Stomach
- A J-shaped muscular bag.
- Secretes gastric juice containing:
- Hydrochloric acid (kills germs, makes medium acidic)
- Pepsin (protein-digesting enzyme)
- Mucus (protects stomach wall)
- Food becomes a semi-liquid called chyme.
Small Intestine (≈ 6–7 m long)
Main site of complete digestion and absorption.
- Receives pancreatic juice (from pancreas) → amylase, trypsin, lipase.
- Receives bile juice (from liver, stored in gall bladder) → emulsifies fats, makes medium alkaline.
- Intestinal juice (succus entericus) completes digestion of all nutrients.
- Villi (finger-like projections) absorb simple nutrients into blood.
Large Intestine
Absorbs most of the water and some salts from undigested food. Remaining waste becomes solid faeces.
Rectum & Anus
Stores faeces temporarily. Faeces are expelled through anus (egestion).
Activity 9.1 – Action of Saliva on Starch (Iodine Test)
| Test tube | Contents | Colour with iodine | Reason |
|---|---|---|---|
| A | Boiled rice (not chewed) | Blue-black | Starch present |
| B | Boiled rice chewed 30–60 s | No blue-black (remains brown) | Saliva converted starch → sugar |
Science and Society – Oral Hygiene
- Brush twice daily, clean tongue.
- Rinse mouth after meals.
- Traditional methods: neem twig (datun), charcoal, salt, etc.
- Prevents tooth decay, gum disease and bad breath.
Key Takeaways & Exam Points
- Complex food → simple soluble form = digestion
- Two types of digestion: mechanical (teeth) & chemical (enzymes)
- Saliva → starch → sugar (sweet taste)
- Stomach → proteins begin to digest
- Small intestine → complete digestion + absorption
- Bile → emulsifies fats; villi → increase absorption area
- Large intestine → water absorption
Mouth (teeth + saliva) → Oesophagus → Stomach (acid + pepsin) → Small intestine (bile + pancreatic + intestinal juice + villi) → Large intestine (water) → Rectum → Anus
As an Amazon Associate, ProSyllabus earns from qualifying purchases. Prices shown are subject to change.
Test your CBSE Class 7 Annual Assessment prep
Quizzes
10 questions · ~10 minutes · instant rank & AI diagnosis
Integers and Rational Numbers Fundamentals | CBSE Class 7 Annual Assessment
Class 7 Social Science — Banks and the Magic of Finance (Practice Quiz)
Class 7 Social Science — Infrastructure: Engine of India's Development (Practice Quiz)
Class 7 Social Science — The State, the Government, and You (Practice Quiz)
Class 7 Social Science — India, a Home to Many (Practice Quiz)
Class 7 Social Science — Turning Tides: 11th and 12th Centuries (Practice Quiz)
Class 7 Social Science — Empires and Kingdoms: 6th to 10th Centuries (Practice Quiz)
Class 7 Social Science — India and Her Neighbours (Practice Quiz)
Class 7 Social Science — The Story of Indian Farming (Practice Quiz)
Class 7 Social Science — Understanding Markets (Practice Quiz)
Class 7 Social Science — From Barter to Money (Practice Quiz)
Class 7 Social Science — The Constitution of India — An Introduction (Practice Quiz)
Class 7 Social Science — From the Rulers to the Ruled: Types of Governments (Practice Quiz)
Class 7 Social Science — How the Land Becomes Sacred (Practice Quiz)
Class 7 Social Science — The Gupta Era: An Age of Tireless Creativity (Practice Quiz)
Class 7 Social Science — The Age of Reorganisation (Practice Quiz)
Class 7 Social Science — The Rise of Empires (Practice Quiz)
Class 7 Social Science — New Beginnings: Cities and States (Practice Quiz)
Class 7 Social Science — Climates of India (Practice Quiz)
Class 7 Social Science — Understanding the Weather (Practice Quiz)
Class 7 Social Science — Geographical Diversity of India (Practice Quiz)
Class 7 Sanskrit — परिशिष्टम् २ — धातुरूपाणि एवं सन्धि-परिचयः (Practice Quiz)
Class 7 Sanskrit — परिशिष्टम् १ — शब्दरूपाणि (Practice Quiz)
Class 7 Sanskrit — वर्णमात्रा-परिचयः (Practice Quiz)
Class 7 Sanskrit — वीराङ्गना पन्नाधाया (Practice Quiz)
Class 7 Sanskrit — द्वीपेषु रम्यः द्वीपोऽण्डमानः (Practice Quiz)
Class 7 Sanskrit — दशमः कः? (Practice Quiz)
Class 7 Sanskrit — अन्नाद् भवन्ति भूतानि (Practice Quiz)
Class 7 Sanskrit — हितं मनोहारि च दुर्लभं वचः (Practice Quiz)
Class 7 Sanskrit — ईशावास्यम् इदं सर्वम् (Practice Quiz)
Class 7 Sanskrit — क्रीडाम वयं श्लोकान्त्याक्षरीम् (Practice Quiz)
Class 7 Sanskrit — सेवा हि परमो धर्मः (Practice Quiz)
Class 7 Sanskrit — न लभ्यते चेत् आम्लं द्राक्षाफलम् (Practice Quiz)
Class 7 Sanskrit — मित्राय नमः (Practice Quiz)
Class 7 Sanskrit — नित्यं पिबामः सुभाषितरसम् (Practice Quiz)
Class 7 Sanskrit — वन्दे भारतमातरम् (Practice Quiz)
Class 7 Hindi — मीरा के पद (Practice Quiz)
Class 7 Hindi — चिड़िया (Practice Quiz)
Class 7 Hindi — बिरजू महाराज से साक्षात्कार (Practice Quiz)
Class 7 Hindi — वर्षा-बहार (Practice Quiz)
Class 7 Hindi — गिरिधर कविराय की कुंडलियाँ (Practice Quiz)
Class 7 Hindi — नहीं होना बीमार (Practice Quiz)
Class 7 Hindi — पानी रे पानी (Practice Quiz)
Class 7 Hindi — फूल और काँटा (Practice Quiz)
Class 7 Hindi — तीन बुद्धिमान (Practice Quiz)
Class 7 Hindi — माँ, कह एक कहानी (Practice Quiz)
Class 7 English — Bravehearts (Practice Quiz)
Class 7 English — Travel and Adventure (Practice Quiz)
Class 7 English — Dreams and Discoveries (Practice Quiz)
Class 7 English — Wit and Humour (Practice Quiz)
Class 7 English — Learning Together (Practice Quiz)
Class 7 Maths — Finding the Unknown (Practice Quiz)
Class 7 Maths — Constructions and Tilings (Practice Quiz)
Class 7 Maths — Connecting the Dots… (Practice Quiz)
Class 7 Maths — Another Peek Beyond the Point (Practice Quiz)
Class 7 Maths — Finding Common Ground (Practice Quiz)
Class 7 Maths — Operations with Integers (Practice Quiz)
Class 7 Maths — Geometric Twins (Practice Quiz)
Class 7 Maths — Working with Fractions (Practice Quiz)
Class 7 Maths — A Tale of Three Intersecting Lines (Practice Quiz)
Class 7 Maths — Number Play (Practice Quiz)
Class 7 Maths — Parallel and Intersecting Lines (Practice Quiz)
Class 7 Maths — Expressions Using Letter-Numbers (Practice Quiz)
Class 7 Maths — A Peek Beyond the Point (Practice Quiz)
Class 7 Maths — Arithmetic Expressions (Practice Quiz)
Class 7 Maths — Large Numbers Around Us (Practice Quiz)
Class 7 Science — Earth, Moon, and the Sun (Practice Quiz)
Class 7 Science — Light: Shadows and Reflections (Practice Quiz)
Class 7 Science — Life Processes in Plants (Practice Quiz)
Class 7 Science — Life Processes in Animals (Practice Quiz)
Class 7 Science — Measurement of Time and Motion (Practice Quiz)
Class 7 Science — Heat Transfer in Nature (Practice Quiz)
Class 7 Science — Adolescence: A Stage of Growth and Change (Practice Quiz)
Class 7 Science — Changes Around Us: Physical and Chemical (Practice Quiz)
Class 7 Science — The World of Metals and Non-metals (Practice Quiz)
Class 7 Science — Electricity: Circuits and their Components (Practice Quiz)
Class 7 Science — Exploring Substances: Acidic, Basic, and Neutral (Practice Quiz)
Class 7 Science — The Ever-Evolving World of Science (Practice Quiz)
Simple Equations and Applications Practice Quiz | CBSE Class 7 Annual Assessment
Visualising Solid Shapes Advanced Challenge | CBSE Class 7 Annual Assessment
Tracing Changes Through Time Fundamentals | CBSE Class 7 Annual Assessment
Nutrition in Plants Fundamentals | CBSE Class 7 Annual Assessment
Group Discussions
No forum posts available.
