10 BIOLOGY OUR ENVIRONMENT – REVISION NOTES

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 OUR ENVIRONMENT – REVISION NOTES 

1. Environment

  • Environment includes all living and non-living components.

  • Living organisms interact with:

    • Other organisms

    • Physical surroundings

  • These interactions maintain balance in nature.

2. Ecosystem

  • An ecosystem is formed by the interaction of:

    • Biotic components (living)

    • Abiotic components (non-living)

Examples

  • Natural ecosystems: forest, pond, lake

  • Artificial ecosystems: garden, crop field, aquarium

3. Components of an Ecosystem

A. Biotic Components

  • Plants

  • Animals

  • Microorganisms

  • Human beings

B. Abiotic Components

  • Temperature

  • Rainfall

  • Air

  • Soil

  • Minerals

4. Classification of Organisms Based on Nutrition

1. Producers

  • Green plants and some bacteria

  • Prepare food by photosynthesis

  • Use sunlight, carbon dioxide, water and chlorophyll

  • Form the base of all ecosystems

2. Consumers

  • Depend directly or indirectly on producers

  • Types:

    • Herbivores – eat plants

    • Carnivores – eat animals

    • Omnivores – eat plants and animals

    • Parasites – depend on host

3. Decomposers

  • Bacteria and fungi

  • Break down dead plants and animals

  • Convert complex organic matter into simple substances

  • Maintain soil fertility

  • Essential for nutrient recycling

5. Food Chain

  • A food chain shows transfer of food and energy.

  • Example:

    • Grass → Goat → Human

6. Trophic Levels

  • Each step in a food chain is a trophic level.

  1. Producers

  2. Primary consumers (herbivores)

  3. Secondary consumers

  4. Tertiary consumers

7. Flow of Energy

  • Energy flows only in one direction.

  • Green plants capture only 1% of solar energy.

  • 10% Law:

    • Only 10% of energy is transferred to the next trophic level.

  • Due to energy loss:

    • Food chains are limited to 3–4 levels.

8. Food Web

  • A food web is a network of interconnected food chains.

  • One organism can be part of many food chains.

  • Food webs make ecosystems more stable.

9. Biological Magnification

  • Harmful chemicals like pesticides enter food chains.

  • These chemicals are non-biodegradable.

  • Their concentration increases at each trophic level.

  • Humans are most affected as they occupy the top level.

10. Ozone Layer

  • Ozone is made of three oxygen atoms (O₃).

  • Present in the upper atmosphere.

  • Protects Earth from harmful ultraviolet (UV) rays.

Ozone Depletion

  • Caused mainly by CFCs (Chlorofluorocarbons).

  • CFCs are used in:

    • Refrigerators

    • Air conditioners

    • Fire extinguishers

  • Ozone depletion leads to:

    • Skin cancer

    • Eye damage

    • Harm to plants and animals

11. Waste Management

Biodegradable Waste

  • Can be decomposed by microorganisms

  • Examples:

    • Vegetable peels

    • Paper

    • Food waste

Non-Biodegradable Waste

  • Cannot be decomposed

  • Examples:

    • Plastic

    • Glass

    • Metals

12. Effects of Waste on Environment

Biodegradable Waste

  • Produces bad smell

  • Releases gases during decomposition

  • Causes pollution if accumulated in excess

Non-Biodegradable Waste

  • Accumulates in the environment

  • Causes soil and water pollution

  • Enters food chains

  • Causes health problems

13. Managing Garbage

  • Follow 3R Principle:

    • Reduce – avoid unnecessary items

    • Reuse – use items again

    • Recycle – convert waste into new products

  • Waste should be segregated at source.

14. Key Exam Points

  • Producers are the foundation of ecosystem.

  • Energy flow is unidirectional.

  • Only 10% energy is transferred between trophic levels.

  • Biological magnification increases with trophic level.

  • Ozone layer protects life from UV radiation.

  • Plastics are non-biodegradable.

  • Waste disposal is a serious environmental issue.