Our Environment Chapter 15 Class 10 Science Revision Notes

Introduction

The environment includes our physical surroundings like air (or atmosphere), water bodies, soil (land) and all organisms such as plants, animals, human beings, and micro-organisms like bacteria and fungi (called decomposers).

Waste materials produced by human and animal activities are poisonous to some extent and can be divided into:

• Biodegradable wastes
• Non-biodegradable wastes

Ecosystem

• An ecosystem is a self-contained unit of living organisms and their non-living environment (e.g., forest, pond, lake, grassland).
• Components of an ecosystem:
  • Biotic components: Producer, Consumer, Decomposer/Saprophyte
  • Abiotic components: Soil, air, water, temperature, etc.
• Consumers are divided into:
  • Herbivores
  • Carnivores
  • Omnivores
• Planktons: Microscopic organisms floating on water.
  • Phytoplanktons: Microscopic aquatic plants
  • Zooplanktons: Microscopic aquatic animals (e.g., protozoa)
• Decomposers: Micro-organisms that break down complex organic matter into simpler substances.

Food Chains and Food Webs

• A food chain is a sequence of organisms where one consumes the other to transfer energy.
• It is unidirectional – energy flows in one direction only.
• In aquatic ecosystems, food chains start with phytoplanktons.
• Trophic levels: The steps in a food chain where energy transfer occurs.
• Food web: A network of inter-connected food chains.

Human Activities and Environment

Global Warming

Pollutants like carbon dioxide increase Earth’s temperature. Deforestation also contributes to global warming.

Ozone Layer and Its Importance

• Ozone (O₃) is a molecule of three oxygen atoms.
• Ozone protects Earth from harmful UV rays from the Sun.
• Formed by the action of UV rays on oxygen (O₂) molecules.
• Depletion of the ozone layer is caused by CFCs (chlorofluorocarbons).

Important Points

• Flow of materials in an ecosystem is cyclic, but energy flow is unidirectional.
• Energy is transferred from one trophic level to another in a food chain.
• 10% Law: Only 10% of energy is passed to the next trophic level.
• Biological magnification: Increase in concentration of harmful chemicals (like pesticides) at each trophic level.

Waste Disposal Methods

Waste should be disposed scientifically. Common methods include:

• Recycling
• Preparation of compost
• Incineration
• Landfill
• Sewage treatment