Chapter 13: Our Environment
13.1 Ecosystem — What Are Its Components?
13.1.1 Ecosystem Structure
- Ecosystem: A self-sustaining system comprising all interacting biotic components (living organisms) and abiotic components (physical factors like temperature, rainfall, wind, soil, and minerals).
- Producers: Organisms (primarily green plants and certain bacteria) that synthesize organic food substances from inorganic materials using solar energy and chlorophyll.
- Consumers: Organisms that depend on producers directly or indirectly for nutrition; categorized into herbivores, carnivores, omnivores, and parasites.
- Decomposers: Microorganisms (like bacteria and fungi) that break down dead remains and complex organic waste into simple inorganic nutrients, replenishing the ecosystem.
13.2 Food Chains and Webs
13.2.1 Energy Flow and Magnification
- Trophic Levels: The various sequential stages of a food chain where energy transfer occurs, starting from producers (first level) to tertiary consumers (fourth level).
- 10% Law: On average, only 10% of the food energy consumed is converted into organic matter and made available to the next trophic level.
- Food Web: A branching network of interconnected food chains reflecting the complex feeding habits of various organisms in an ecosystem.
- Biological Magnification: The progressive accumulation and concentration increase of non-degradable chemical toxins (such as pesticides) at successive trophic levels.
13.3 Environmental Impact of Human Activities
13.3.1 Ozone Layer Depletion
- Ozone (O3): A critical trioxygen molecule in the stratosphere that absorbs and filters out harmful solar ultraviolet (UV) radiation.
- CFCs (Chlorofluorocarbons): Synthetic ozone-depleting substances commonly utilized in refrigeration and fire extinguishers.
- UNEP: The United Nations Environment Programme, which organized global initiatives like the 1987 treaty to freeze CFC production levels.
13.3.2 Solid Waste Management
- Biodegradable Waste: Domestic or biological waste materials that can be easily decomposed by microbes.
- Non-biodegradable Waste: Long-lasting synthetic materials (such as plastics) that persist in the environment and generate pollution.