Our Environment
1. What is Environment?
The environment includes everything around us — living (biotic) and non-living (abiotic).
| Component | Examples |
|---|---|
| Biotic | Plants, animals, microorganisms, humans |
| Abiotic | Air, water, soil, sunlight, temperature, rocks |
The environment provides all the resources needed for survival: air to breathe, water to drink, food to eat, and shelter.
2. Ecosystem
An ecosystem is a community of living organisms interacting with each other and with their non-living environment.
Components of an Ecosystem
| Component | Description | Examples |
|---|---|---|
| Producers | Make their own food (photosynthesis) | Green plants, algae |
| Consumers | Eat other organisms | Animals, humans |
| Decomposers | Break down dead organisms | Bacteria, fungi |
Types of Ecosystems
| Type | Examples |
|---|---|
| Natural — Terrestrial | Forest, grassland, desert, tundra |
| Natural — Aquatic | Pond, lake, river, ocean |
| Artificial | Garden, aquarium, crop field |
Worked Example: Classify as producer, consumer, or decomposer: (a) Grass (b) Tiger (c) Mushroom (d) Cow.
(a) Grass: Producer. (b) Tiger: Consumer. (c) Mushroom: Decomposer. (d) Cow: Consumer.
3. Food Chain
A food chain shows who eats whom in an ecosystem. It shows the flow of energy.
Example: Grass -> Grasshopper -> Frog -> Snake -> Eagle
Trophic Levels (steps in a food chain)
| Level | Description | Example |
|---|---|---|
| First | Producers (plants) | Grass, algae |
| Second | Primary consumers (herbivores) | Grasshopper, cow, deer |
| Third | Secondary consumers (carnivores) | Frog, snake |
| Fourth | Tertiary consumers (top carnivores) | Eagle, lion |
Key facts about food chains:
- Energy flows from producers to consumers.
- Only about 10% of energy passes from one level to the next.
- Most food chains have 3-5 levels (limited energy at top).
Food web: A network of interconnected food chains in an ecosystem.
Common Mistake: Thinking decomposers are at the top of the food chain. Decomposers act at ALL levels, breaking down dead organisms at every stage.
Exam Focus (3 marks): 'Construct a food chain from a pond ecosystem with four levels.'
Algae (producer) -> Tiny fish (primary consumer) -> Big fish (secondary consumer) -> Heron (tertiary consumer).
4. Adaptations
Adaptation is a special feature or behaviour that helps an organism survive in its environment.
Camel (Desert Adaptation)
| Feature | Adaptation |
|---|---|
| Hump | Stores fat for energy when food is scarce |
| Long legs | Keep the body away from hot sand |
| Broad feet | Prevent sinking into sand |
| Thick eyelashes | Protect eyes from sandstorms |
| Nostrils | Can be closed to keep out sand |
| Concentrated urine | Reduces water loss |
| Thick fur on back | Reflects sunlight, insulates from heat |
Common Mistake: Thinking the camel's hump stores water. The hump stores FAT, not water. The fat can be broken down to produce both energy and water.
Fish (Aquatic Adaptation)
| Feature | Adaptation |
|---|---|
| Streamlined body | Reduces water resistance, helps swim fast |
| Fins | Help in swimming and maintaining balance |
| Scales | Protect the body and reduce friction |
| Gills | Extract oxygen from water |
| Swim bladder | Helps in floating at desired depth |
Cactus (Desert Adaptation)
| Feature | Adaptation |
|---|---|
| Thick, fleshy stem | Stores water |
| Spines (modified leaves) | Reduce water loss, protect from animals |
| Shallow but wide roots | Absorb rainwater quickly over a large area |
| Waxy coating on stem | Prevents water loss (transpiration) |
| Few or no leaves | Reduces surface area for water loss |
Exam Focus (4 marks): 'Explain three adaptations of a cactus for survival in the desert.'
(1) The stem is thick and fleshy to store water. (2) Leaves are reduced to spines to minimise water loss. (3) Roots are shallow but spread wide to absorb rainwater quickly.
5. Conservation of the Environment
Why Conserve?
- Biodiversity loss: Species are going extinct due to habitat destruction.
- Pollution: Air, water, and land pollution harm all life.
- Climate change: Rising temperatures affect ecosystems worldwide.
- Resource depletion: Non-renewable resources are running out.
Ways to Conserve
- Reduce, Reuse, Recycle: Minimise waste.
- Plant trees: Reforestation restores habitats.
- Save water: Turn off taps, fix leaks.
- Use renewable energy: Solar, wind, hydel power.
- Protect wildlife: Do not hunt, support sanctuaries and national parks.
- Avoid plastics: Use cloth bags, metal bottles.
Protected areas in India: Jim Corbett National Park (tigers), Kaziranga National Park (rhinos), Keoladeo National Park (birds).
6. Self-Test
- Define ecosystem. Name its components.
- Differentiate between biotic and abiotic components.
- Construct a food chain with four trophic levels from a forest ecosystem.
- Why is the camel's hump not used to store water?
- List three adaptations of: (a) Fish (b) Cactus.
- Why are decomposers important in an ecosystem?
- Suggest two ways to conserve the environment.
7. Answers to Self-Test
- A community of organisms interacting with their environment. Components: producers, consumers, decomposers.
- Biotic: living (plants, animals). Abiotic: non-living (air, water, soil).
- Grass -> Deer -> Tiger -> Vulture. (Or any valid forest food chain.)
- The hump stores fat, not water. Fat provides energy and can be metabolised to produce water.
- (a) Fish: streamlined body, gills, fins. (b) Cactus: thick stem (stores water), spines (reduce water loss), wide roots.
- Decomposers break down dead organisms, returning nutrients to the soil for producers to use.
- (1) Plant more trees. (2) Reduce, reuse, and recycle waste.
