Chapter 1: Sources of Food 🌱
A Comprehensive Guide for PSTET Paper-2 (Science)
Chapter Overview
| Section | Topic | PSTET Weightage | Page No. |
|:---:|:---|::---:|:---:|
| 1.1 | Plant Parts as Food | High | 2 |
| 1.2 | Animal Products as Food | Medium | 5 |
| 1.3 | Food Chain: Producers, Consumers, Decomposers | High | 8 |
| 1.4 | Agricultural Practices (Basic) | Low | 12 |
| Practice Zone | MCQs & Pedagogical Questions | - | 15 |
Learning Objectives 🎯
After studying this chapter, you will be able to:
✅ Identify different plant parts used as food by humans
✅ Classify animal products into various food categories
✅ Explain the concept of food chain with trophic levels
✅ Distinguish between producers, consumers, and decomposers
✅ Describe basic agricultural practices related to food production
✅ Apply pedagogical strategies to teach "Sources of Food" effectively
Pedagogical Link 🔗
For Teachers: This chapter connects directly to Class 6 Science NCERT Chapter 1 ("Food: Where Does It Come From?"). When teaching this topic to upper primary students, focus on:
Using real-life examples from students' daily meals
Encouraging students to observe and record their own food sources
Building connections between science and environmental awareness
Developing scientific observation skills through classification activities
Section 1.1: Plant Parts as Food 🌿
Introduction
Plants are the primary producers in our ecosystem and form the foundation of almost all food chains. Different parts of plants provide us with various nutrients essential for our growth and development. Let's explore which plant parts we consume as food.
1.1.1 Classification of Edible Plant Parts
Plants have several parts - roots, stems, leaves, flowers, fruits, and seeds. All these parts can be sources of food, though different plants provide different edible parts.
Table 1.1: Plant Parts as Food with Examples
| Plant Part | Description | Examples | Nutritional Significance | Teaching Tip |
|---|---|---|---|---|
| Roots 🥕 | Underground parts that absorb water and minerals | Carrot, Radish, Beetroot, Sweet Potato, Turnip | Rich in carbohydrates, fiber, and vitamins | Show actual vegetables in class; let students taste raw pieces |
| Stems 🥔 | Main supporting structure of plants | Potato (modified stem), Ginger, Onion, Garlic, Sugarcane | Store starch and water; provide energy | Clarify common misconception: potato is stem, not root! |
| Leaves 🥬 | Food factories through photosynthesis | Spinach, Cabbage, Lettuce, Fenugreek, Mustard | Rich in iron, calcium, and vitamins | Discuss why leafy vegetables are important for health |
| Flowers 🌼 | Reproductive parts | Broccoli, Cauliflower, Banana flower | Good source of antioxidants | Show flower-to-fruit transformation |
| Fruits 🍎 | Ripened ovaries containing seeds | Apple, Mango, Banana, Orange, Tomato, Brinjal | Rich in vitamins, minerals, fiber | Explain botanical vs. culinary fruits |
| Seeds 🌰 | Embryonic plants enclosed in covering | Wheat, Rice, Pulses (dal), Peas, Groundnut, Mustard seeds | High in proteins, oils, and energy | Discuss staple foods of different regions |
1.1.2 Detailed Explanation for PSTET
A. Roots as Food 🌽
Roots that we eat are primarily of two types:
Tap Roots: Develop from radicle (e.g., carrot, radish, turnip, beetroot)
Adventitious Roots: Develop from other plant parts (e.g., sweet potato)
📝 Key Point for Exam: Sweet potato is a modified adventitious root (tuberous root) while potato is a modified stem (tuber). This distinction is frequently asked in PSTET!
B. Stems as Food 🌾
Modified stems that serve as food storage organs:
Underground Stems: Potato (tuber), Ginger (rhizome), Onion (bulb), Garlic (bulb)
Aerial Stems: Sugarcane (stores sucrose), Bamboo shoots
🧪 Activity Idea: Ask students to bring one vegetable from home. Classify them according to which plant part they represent. This develops observation and classification skills.
C. Leaves as Food 🍃
Leaves are the kitchen of the plant where photosynthesis occurs. Common leafy vegetables:
Green Leafy Vegetables: Spinach (palak), Mustard leaves (sarson), Fenugreek (methi), Cabbage
Other Leaves: Coriander, Mint, Curry leaves (used as herbs)
🌍 Did You Know? Cabbage is actually a highly compressed mass of leaves forming a tight head!
D. Flowers as Food 🌸
Though less common, several flowers are edible:
Vegetable Flowers: Broccoli, Cauliflower (immature flower clusters)
Direct Flowers: Banana flower, Pumpkin flower, Rose (as flavoring)
E. Fruits as Food 🍇
Botanically, a fruit is a seed-bearing structure developed from the ovary after flowering. Common fruits include:
Sweet Fruits: Mango, Apple, Banana, Grapes
Vegetable-Fruits: Tomato, Brinjal, Pumpkin, Cucumber (botanically fruits, culinarily vegetables)
📚 NCERT Connection: Class 6 Science explains that fruits like tomato and brinjal are often confused as vegetables but are actually fruits!
F. Seeds as Food 🌰
Seeds are rich in stored food for the germinating plant:
Cereals: Wheat, Rice, Maize, Barley (major energy sources)
Pulses: Gram, Pea, Bean, Lentil (protein-rich)
Oilseeds: Mustard, Groundnut, Soybean, Sunflower (oil sources)
Spices: Cumin, Coriander seeds, Fenugreek seeds
📊 Important Statistics for PSTET:
India is the largest producer of pulses in the world
Punjab is known as the "Food Bowl of India" for wheat and rice production
1.1.3 Pedagogical Implications for Teaching Plant Parts as Food
| Teaching Strategy | Description | PSTET Relevance |
|---|---|---|
| Observation Method | Show real plants/vegetables and let students observe, touch, and identify parts | Directly tests understanding of 'Method of Science' |
| Classification Activity | Provide mixed vegetables; students classify by plant part | Develops analytical skills |
| Concept Mapping | Create visual maps showing plant → part → food item | Enhances memory retention |
| Local Resource Utilization | Use locally available plants to explain concepts | Connects to 'Innovation' in teaching |
Section 1.2: Animal Products as Food 🥛
Introduction
Animals provide us with a variety of food products rich in proteins, fats, and other nutrients. Different animals give us different products, and some animals are consumed directly as food.
1.2.1 Types of Animal-Derived Foods
Table 1.2: Animal Products as Food
| Product Category | Source Animal | Examples | Nutritional Value | Cultural Significance |
|---|---|---|---|---|
| Milk & Dairy 🥛 | Cow, Buffalo, Goat, Camel | Milk, Curd, Cheese, Butter, Ghee, Paneer | Complete protein, calcium, vitamin D | Staple in vegetarian diet; sacred in Indian culture |
| Eggs 🥚 | Hen, Duck, Quail | Boiled, Fried, Omelette | High-quality protein, vitamin B12 | Affordable protein source |
| Meat 🍗 | Goat, Chicken, Fish, Pig | Mutton, Chicken, Fish, Pork | Rich protein, iron, B vitamins | Major protein source for non-vegetarians |
| Honey 🍯 | Honey Bees | Raw honey, Processed honey | Natural sugars, antioxidants | Only animal product not involving animal harm |
| Other Products | Various | Fish oil, Cod liver oil | Omega-3 fatty acids | Used as supplements |
1.2.2 Detailed Analysis for PSTET
A. Milk: The Complete Food 🥛
Milk is often called a "complete food" because it contains:
Proteins: Casein, whey proteins
Fats: Butterfat
Carbohydrates: Lactose (milk sugar)
Minerals: Calcium, phosphorus
Vitamins: A, D, B12
🐄 India's Milk Production:
India is the largest producer of milk globally
Operation Flood (White Revolution) made India self-sufficient in milk production
Amul is India's largest milk cooperative
B. Eggs: Nature's Protein Package 🥚
An egg contains:
White Part (Albumen): Mainly water and protein (albumin)
Yellow Part (Yolk): Fats, proteins, vitamins, and minerals
📝 Key Fact: Egg is one of the few foods that naturally contain Vitamin D.
C. Meat and Fish 🐟
Different cultures consume different animals:
Common Meats: Chicken (most consumed globally), Mutton (goat meat), Fish
Regional Variations: Pork (northeastern India), Beef (Kerala, West Bengal), Rabbit, Duck
D. Honey: The Sweet Gift of Bees 🍯
Honey is produced by honey bees from flower nectar. It is unique because:
It is the only animal product that doesn't require killing the animal
It has medicinal properties and never spoils
It contains natural sugars (fructose and glucose)
🌍 Did You Know? Honey found in Egyptian tombs (3000 years old) was still edible!
1.2.3 Teaching Animal Products: Pedagogical Approaches
| Approach | Activity Idea | Learning Outcome |
|---|---|---|
| Experiential Learning | Visit a dairy farm or watch videos of milking | Understanding source of milk |
| Discussion Method | Discuss vegetarian vs. non-vegetarian food habits | Respect for diversity |
| Project Work | Trace the journey of milk from farm to home | Understanding food processing |
| Value Education | Discuss ethical treatment of animals | Developing empathy |
Section 1.3: Food Chain - Producers, Consumers, and Decomposers 🌍
Introduction
All living organisms need energy to survive. The flow of energy from one organism to another through eating and being eaten forms a food chain. Understanding food chains is fundamental to ecology and environmental science.
1.3.1 Trophic Levels in a Food Chain
According to ecological principles, different species within a food chain are organized into trophic levels (feeding levels) .
Table 1.3: Trophic Levels Explained
| Trophic Level | Category | Description | Examples | Energy Role |
|---|---|---|---|---|
| First Level | Producers 🌿 | Green plants that synthesize food using sunlight | Grasses, Trees, Algae, Aquatic plants | Convert solar energy to chemical energy |
| Second Level | Primary Consumers 🐇 | Herbivores that eat producers | Cow, Deer, Rabbit, Grasshopper, Insects | Obtain energy from plants |
| Third Level | Secondary Consumers 🐸 | Small carnivores that eat herbivores | Frog, Small fish, Snake, Lizard | Obtain energy from herbivores |
| Fourth Level | Tertiary Consumers 🦁 | Large carnivores that eat other carnivores | Lion, Tiger, Eagle, Shark | Top predators in ecosystem |
| All Levels | Decomposers 🍄 | Break down dead organisms | Bacteria, Fungi, Earthworms | Recycle nutrients back to soil |
1.3.2 Detailed Explanation of Each Component
A. Producers (Autotrophs) 🌿
Producers are organisms that can produce their own food using sunlight, water, and carbon dioxide through photosynthesis .
Key Characteristics:
Contain chlorophyll (green pigment)
Convert solar energy into chemical energy
Form the first trophic level in all food chains
Include: green plants, algae, phytoplankton
📝 PSTET Formula: Producers + Sunlight + CO₂ + Water → Glucose + Oxygen
B. Consumers (Heterotrophs) 🐾
Consumers cannot produce their own food and depend on producers or other consumers for nutrition .
Types of Consumers:
Primary Consumers (Herbivores): Animals that eat only plants
Examples: Cow, goat, deer, rabbit, grasshopper, elephant
Also called first-order consumers
Secondary Consumers (Small Carnivores): Animals that eat herbivores
Examples: Frog (eats insects), snake (eats frog), cat, small fish
Also called second-order consumers or first-degree carnivores
Tertiary Consumers (Large Carnivores): Animals that eat other carnivores
Examples: Lion, tiger, eagle, shark, wolf
Also called top carnivores or apex predators
Omnivores: Animals that eat both plants and animals
Examples: Humans, bear, crow, dog
Table 1.4: Consumer Classification with Examples
| Consumer Type | Food Preference | Terrestrial Examples | Aquatic Examples |
|---|---|---|---|
| Herbivores | Plants only | Cow, Deer, Rabbit | Certain fish, Mollusks |
| Carnivores | Animals only | Lion, Tiger, Snake | Shark, Whale |
| Omnivores | Both plants and animals | Human, Bear, Crow | Turtle, Some fish |
| Scavengers | Dead animals | Vulture, Jackal | Crab, Lobster |
C. Decomposers (Saprotrophs) 🍄
Decomposers break down dead plants and animals into simpler substances, returning nutrients to the soil .
Key Characteristics:
Also called detrivores or saprotrophs
Include bacteria and fungi
Essential for nutrient recycling
Without decomposers, Earth would be covered with dead bodies
Examples:
Fungi: Mushrooms, mold, yeast
Bacteria: Decomposing bacteria in soil
Other: Earthworms (called "farmer's friend")
1.3.3 The 10% Law of Energy Transfer
When energy passes from one trophic level to the next, only about 10% is transferred. The remaining 90% is lost as heat during metabolism .
Example:
If producers have 1000 J of energy
Primary consumers receive only 100 J
Secondary consumers receive only 10 J
Tertiary consumers receive only 1 J
🌿 This explains why:
Food chains rarely have more than 4-5 levels
Top carnivores need large territories
Plant-based diets are more energy-efficient
1.3.4 Food Chain Examples for Classroom Teaching
Example 1: Grassland Food Chain 🌾
Grass (Producer) → Grasshopper (Primary Consumer) → Frog (Secondary Consumer) → Snake (Tertiary Consumer) → Eagle (Top Carnivore) ← Decomposers (Bacteria, Fungi)
Example 2: Aquatic Food Chain 🌊
Phytoplankton (Producer) → Zooplankton (Primary Consumer) → Small Fish (Secondary Consumer) → Large Fish (Tertiary Consumer) ← Decomposers
Example 3: Forest Food Chain 🌳
Tree (Producer) → Deer (Primary Consumer) → Lion (Tertiary Consumer) ← Decomposers
1.3.5 Pedagogical Strategies for Teaching Food Chains
| Teaching Method | Classroom Activity | PSTET Focus |
|---|---|---|
| Discovery Method | Students discover local food chains through observation | Scientific process skills |
| Role Play | Students act as different organisms in a food chain | Engaging multiple intelligences |
| Flowchart Creation | Draw and label food chains with arrows showing energy flow | Visual learning |
| Gaming | "Who Eats Whom?" card game | Reinforcement through fun |
| Integrated Approach | Connect with Environmental Studies and Geography | Cross-curricular learning |
Section 1.4: Preparation of Soil and Agricultural Practices 🌾
Introduction
Before we get food from plants, the soil must be prepared. Agriculture is the science and art of cultivating soil, growing crops, and raising livestock. This section provides a basic introduction to agricultural practices related to food sources.
1.4.1 Basic Agricultural Practices
Table 1.5: Steps in Agriculture
| Step | Practice | Description | Purpose |
|---|---|---|---|
| 1 | Soil Preparation 🚜 | Ploughing, levelling, and adding manure | Make soil suitable for sowing |
| 2 | Sowing 🌱 | Placing seeds in soil | Plant crops |
| 3 | Adding Manure & Fertilizers 🧪 | Enriching soil with nutrients | Provide plant nutrition |
| 4 | Irrigation 💧 | Watering crops | Provide water for growth |
| 5 | Weeding 🌿 | Removing unwanted plants | Reduce competition for nutrients |
| 6 | Harvesting ✂️ | Cutting mature crops | Collect food |
| 7 | Storage 🏪 | Preserving harvested crops | Prevent spoilage |
1.4.2 Soil Preparation in Detail
A. Ploughing (Tilling)
Turning and loosening soil using a plough
Tools: Wooden/iron plough, tractor, hoe, cultivator
Benefits:
Allows roots to penetrate deeply
Brings nutrient-rich soil to top
Improves soil aeration
Helps in mixing manure
B. Levelling
Smoothing the ploughed field
Tool: Leveller (wooden plank)
Benefits:
Uniform water distribution
Prevents water logging
Easy for sowing
C. Manuring
Adding organic matter to soil
Sources: Cow dung, compost, green manure
Benefits:
Adds nutrients
Improves soil structure
Increases water holding capacity
1.4.3 Traditional vs Modern Agricultural Practices
| Aspect | Traditional Practices | Modern Practices |
|---|---|---|
| Ploughing | Bullock-drawn plough | Tractor, Rotavator |
| Seeds | Saved from previous crop | Hybrid, HYV seeds |
| Irrigation | Wells, canals, rainfall | Sprinklers, Drip irrigation |
| Fertilizers | Cow dung, compost | Chemical fertilizers |
| Pest Control | Natural methods | Pesticides, Insecticides |
| Storage | Traditional bins | Silos, Cold storage |
1.4.4 Agricultural Practices in Punjab (State-Specific)
Punjab is known as the "Food Bowl of India" due to its significant contribution to food grain production.
Key Facts about Punjab Agriculture:
Major Crops: Wheat (Rabi season), Rice/Paddy (Kharif season)
Green Revolution: Punjab was the epicenter of Green Revolution in India
Irrigation: Extensive canal network and tube wells
Production: Contributes majorly to central food pool
Challenges: Groundwater depletion, stubble burning, soil degradation
Chapter Summary: Key Points for Revision 📝
Quick Revision Table
| Topic | Key Points | Common PSTET Questions |
|---|---|---|
| Plant Parts as Food | Roots (carrot), Stems (potato), Leaves (spinach), Flowers (cauliflower), Fruits (apple), Seeds (wheat) | Potato is stem/root? Sweet potato is? |
| Animal Products | Milk, egg, meat, honey; India largest milk producer | Complete food? Honey uniqueness? |
| Producers | Green plants, autotrophs, first trophic level | What is producer in pond? |
| Consumers | Primary (herbivores), Secondary (carnivores), Tertiary (top carnivores) | Example of secondary consumer? |
| Decomposers | Bacteria, fungi; recycle nutrients | Why are decomposers important? |
| 10% Law | Only 10% energy transfers between trophic levels | Why food chains are short? |
| Agriculture | Soil preparation, sowing, irrigation, harvesting | Steps in agriculture? |
Practice Zone: PSTET-Style Questions 🎯
Content-Based MCQs
Q1. Which of the following is a modified stem?
a) Carrot
b) Sweet potato
c) Potato
d) Radish
Q2. In a food chain, which organisms are called primary consumers?
a) Green plants
b) Herbivores
c) Carnivores
d) Decomposers
Q3. According to the 10% law of energy transfer, if producers have 10,000 J of energy, how much will be available to tertiary consumers?
a) 1000 J
b) 100 J
c) 10 J
d) 1 J
Q4. Which of the following is NOT an animal product?
a) Honey
b) Egg
c) Mushroom
d) Cheese
Q5. The first trophic level in a food chain always consists of:
a) Primary consumers
b) Producers
c) Decomposers
d) Secondary consumers
Pedagogical MCQs
Q6. A teacher brings various vegetables to class and asks students to classify them based on which plant part they represent. This teaching method is an example of:
a) Lecture method
b) Discovery method
c) Rote learning
d) Textbook method
Q7. To teach the concept of food chain effectively to Class 6 students, the most appropriate teaching aid would be:
a) Only textbook reading
b) Diagrams showing arrows from one organism to another
c) Writing definitions on board
d) Memorizing examples
Q8. While teaching about food sources, a teacher should emphasize:
a) Only theoretical knowledge
b) Connecting with students' daily meals
c) Memorizing scientific names
d) Completing syllabus quickly
Answer Key with Explanations
| Q.No. | Answer | Explanation |
|---|---|---|
| 1 | c) Potato | Potato is a modified stem (tuber); carrot, radish, sweet potato are modified roots |
| 2 | b) Herbivores | Primary consumers are herbivores that eat producers (plants) |
| 3 | c) 10 J | 10% of 10,000 = 1000 J (PC); 10% of 1000 = 100 J (SC); 10% of 100 = 10 J (TC) |
| 4 | c) Mushroom | Mushroom is a fungus (decomposer), not an animal product |
| 5 | b) Producers | First trophic level always has producers (autotrophs) |
| 6 | b) Discovery method | Students discover classification through observation |
| 7 | b) Diagrams with arrows | Visual representation helps understand energy flow |
| 8 | b) Connecting with daily meals | Makes learning meaningful and relevant |
Pedagogical Reflection for Teachers 🤔
Think-Pair-Share Activity:
Think: How would you explain to your students why potato is a stem and sweet potato is a root?
Pair: Discuss with a fellow teacher how food chains can be observed in your school garden.
Share: Design a 10-minute activity to teach "Sources of Food" using locally available resources.
NCERT Textbook Linkages 📚
| Class | Chapter | Topic |
|---|---|---|
| Class 6 | Chapter 1 | Food: Where Does It Come From? |
| Class 6 | Chapter 15 | Air Around Us (contains photosynthesis basics) |
| Class 7 | Chapter 1 | Nutrition in Plants |
| Class 7 | Chapter 2 | Nutrition in Animals |
Chapter End Notes
Key Terminology Glossary
| Term | Definition |
|---|---|
| Autotrophs | Organisms that produce their own food (producers) |
| Heterotrophs | Organisms that depend on others for food (consumers) |
| Herbivores | Animals that eat only plants |
| Carnivores | Animals that eat other animals |
| Omnivores | Animals that eat both plants and animals |
| Decomposers | Organisms that break down dead matter |
| Trophic Level | Feeding level in a food chain |
| Food Chain | Sequence of organisms eating one another |
| Agriculture | Science of cultivating soil and growing crops |
Quick Tips for PSTET Aspirants ⚡
✅ Memorize with Mnemonics:
"Please Come To Dinner" = Producers → Consumers (Primary) → Tertiary → Decomposers
"Raju Sells Fresh Fruits" = Root, Stem, Flower, Fruit (plant parts as food)
✅ Common Exam Traps:
Potato = Stem, Sweet Potato = Root
Tomato = Fruit (botanically), Vegetable (culinary)
Mushroom = Fungus (decomposer), not plant
Honey = Animal product, but no animal killed
✅ Important Facts:
India: Largest milk producer, largest pulse producer
Punjab: Major contributor to wheat and rice production
Green Revolution: Started in India during 1960s
Answers to "Check Your Understanding"
[To be filled by student]
📝 Note for Self-Study: After completing this chapter, ensure you can:
Name 5 plants and the parts we eat from each
List 5 animal products used as food
Draw and label a food chain with 4 organisms
Explain the 10% law of energy transfer
Describe the basic steps of agriculture
End of Chapter 1
Next Chapter: Chapter 2 - Components of Food (Nutrition)
Topics Covered: Nutrients, Balanced Diet, Deficiency Diseases, Testing for Nutrients
