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Tamil Nadu (TNBSE)Class 5 Science★ 5-6 marks in TN Class 5 Term 3 exams — ecosystems, environmental pollution, waste management

Our Environment

Samacheer Kalvi (TN State Board) Class 5 Science — Chapter 8, Our Environment. Ecosystems, biodiversity and pollution. Study notes, key concepts, worked examples, practice questions and quick revision for exam preparation.

⏱ 12 min readMedium difficulty✓ Free · NCERT-aligned

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By the end of this chapter you'll be able to…

1Define an ecosystem as a community of living (biotic) organisms interacting with their non-living (abiotic) environment
2Identify the biotic (plants, animals, microorganisms) and abiotic (sunlight, water, soil, air, temperature) components of a pond ecosystem and a forest ecosystem
3Describe 3 types of pollution: air pollution (causes: vehicles, factories, burning waste; effects: respiratory diseases, acid rain, global warming), water pollution (causes: sewage, industrial waste, agricultural runoff; effects: waterborne diseases, death of aquatic life), soil pollution (causes: chemical fertilisers, pesticides, plastic waste, industrial dumping; effects: loss of soil fertility, contamination of groundwater)
4Explain the 4Rs of waste management: Reduce (use less), Reuse (use again), Recycle (convert waste to new products), Refuse (say no to single-use plastic)
5Understand source segregation: wet waste (green bin — kitchen waste, compostable) vs dry waste (blue bin — plastic, paper, metal, glass — recyclable)

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Why this chapter matters

Our Environment in Class 5 is the culminating environmental science chapter of primary school. Children study ecosystems — how living (biotic) and non-living (abiotic) components interact in a pond, forest, or grassland. They then confront the three major types of pollution — air, water, and soil — understanding causes, effects, and solutions. The chapter ends with practical waste management: the 4Rs (Reduce, Reuse, Recycle, Refuse) and the importance of source segregation. A Class 5 child finishing this chapter should understand that every wrapper they throw, every tap they leave running, and every tree that is cut affects the ecosystem they are part of.

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Our Environment — Class 5 Science (Samacheer Kalvi)

TN State Board (Samacheer Kalvi) Class 5 Science, Chapter 8. Ecosystems, biodiversity and pollution.

1. About this chapter

This chapter covers Our Environment as part of the Class 5 Samacheer Kalvi Science curriculum. It deals with ecosystems, biodiversity and pollution and builds conceptual understanding essential for the TN School Term Exam.

By the end of this chapter, students will be able to:

Define ecosystem and list its components
Explain types and effects of pollution

2. Key concepts

Concept 1: Define ecosystem and list its components.
Concept 2: Explain types and effects of pollution.

3. Important terms and formulas

Term / Formula	Description
Define ecosystem and list…	Define ecosystem and list its components
Explain types and effects…	Explain types and effects of pollution

4. Worked examples

Example 1. Applying a key concept from this chapter.

Solution: Identify the relevant principle → apply the formula or rule → state the answer with correct units.

Example 2. A typical exam-style question on our environment.

Solution: Break the problem into steps, use the appropriate formula and verify the answer.

5. Common mistakes

Mistake: Skipping units or forgetting to state them. Fix: Always write units alongside every quantity and answer.
Mistake: Confusing similar terms or concepts in this chapter. Fix: Make a comparison table of the terms during revision.

6. Practice (exam-style)

Define the main term or principle covered in Chapter 8.
Give two real-life examples related to our environment.
Solve a short numerical or descriptive question from this chapter.
State one important formula and explain each symbol.

7. Answer key (hints)

Refer to section 2 (Key concepts) above for the definition.
Examples should be drawn from daily experience and local context.
Apply the formula from section 3, show all steps clearly.
Formula with units — refer to the textbook glossary for symbol meanings.

8. Quick revision

Class 5 Science — Chapter 8: Our Environment.
Core idea: Ecosystems, biodiversity and pollution.
Key outcomes: Define ecosystem and list its components; Explain types and effects of pollution.
Always revise diagrams / tables from the Samacheer Kalvi textbook before the exam.

Key formulas & results

Everything you need to memorise, in one card. Screenshot this for revision.

Types of pollution

Air pollution → smoke from vehicles and factories, burning of garbage and crop stubble, bursting firecrackers, dust from construction. Effects: asthma, bronchitis, lung cancer, acid rain (SO₂ and NO₂ dissolve in rain), global warming (CO₂ traps heat). Water pollution → untreated sewage, industrial chemicals, oil spills, agricultural fertilisers/pesticides washed into rivers. Effects: cholera, typhoid, death of fish, eutrophication (excess algae growth depleting oxygen). Soil pollution → excessive use of chemical fertilisers and pesticides, dumping of industrial waste, plastic waste, mining. Effects: soil becomes infertile, toxic substances enter food chain through crops.

The Vellore and Tirupur textile dyeing industries in Tamil Nadu have historically been major sources of water pollution in the Noyyal River. Effluent treatment plants are now mandatory, but enforcement remains a challenge.

The 4Rs and source segregation

1. REFUSE → say no to things you don't need (plastic straws, single-use bags, excess packaging). 2. REDUCE → use less of what you do need (carry a cloth bag, use both sides of paper). 3. REUSE → use things again instead of throwing away (glass bottles, old clothes as dusting cloth, gift wrapping paper). 4. RECYCLE → convert waste into new products (old newspapers → recycled paper, PET bottles → fabric, metal cans → new metal items). Source segregation: WET WASTE (green bin) → kitchen waste, vegetable peels, food leftovers, garden waste → COMPOSTING. DRY WASTE (blue bin) → paper, plastic, metal, glass → RECYCLING.

In Tamil Nadu, many local bodies now practice doorstep collection of segregated waste. The compost from wet waste is used in parks and distributed to farmers. Some wards in cities like Trichy and Coimbatore have achieved near 100% waste segregation.

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Common mistakes & fixes

These are the exact errors that cost students marks in board exams. Read them once, save yourself the trouble.

WATCH OUT

✗ Throwing everything — including plastic — into a single bin

✓ When wet and dry waste are mixed, NEITHER can be processed properly. Wet waste contaminates dry recyclables, and plastic in wet waste prevents composting. Segregate at home — two bins, always.

WATCH OUT

✗ Burning dry leaves and garbage (common in many households)

✓ Burning creates severe air pollution — PM2.5 particles, CO, and toxic gases. Dry leaves should be COMPOSTED, not burned. Garbage should be segregated and disposed of properly, never burned.

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