Learning Objectives
- Understand the components of an ecosystem
- Learn about food chains and food webs
- Understand the flow of energy in an ecosystem
- Learn about the ozone layer and its depletion
- Understand waste management and biodegradability
Key Concepts
Ecosystem
An ecosystem is a self-sustaining unit of living organisms (biotic) interacting with their physical environment (abiotic factors: sunlight, temperature, water, soil, air).
Biotic components:
- Producers (autotrophs): Green plants and algae that make food through photosynthesis.
- Consumers (heterotrophs): Primary consumers (herbivores) â Secondary consumers (small carnivores) â Tertiary consumers (top carnivores).
- Decomposers: Bacteria and fungi that break down dead organic matter and recycle nutrients.
Food Chains and Food Webs
A food chain is a linear sequence showing the transfer of energy from one trophic level to the next.
Example: Grass â Grasshopper â Frog â Snake â Eagle
A food web is a network of interconnected food chains in an ecosystem, showing more realistic feeding relationships.
Flow of Energy
10% Law (Lindeman's rule): Only about 10% of the energy at one trophic level is transferred to the next level. The remaining 90% is lost as heat during life processes.
This limits the number of trophic levels in a food chain (usually 3-4 levels).
Biological Magnification
Non-biodegradable chemicals (pesticides like DDT, heavy metals) accumulate in organisms and their concentration increases at each successive trophic level. Top predators have the highest concentration, which can be harmful.
Ozone Layer
The ozone (Oâ) layer in the stratosphere shields the Earth from harmful ultraviolet (UV) radiation.
Ozone is formed: Oâ â O + O (UV) and O + Oâ â Oâ. It is also broken down by UV back to Oâ (dynamic equilibrium).
Ozone depletion: Caused by chlorofluorocarbons (CFCs) used in refrigerators, ACs, and aerosols. CFCs release chlorine atoms that catalytically destroy ozone. This leads to increased UV radiation reaching Earth, causing skin cancer, cataracts, and harm to ecosystems.
UNEP (United Nations Environment Programme) led efforts to limit CFC use.
Waste Management
- Biodegradable waste: Can be broken down by biological processes. Examples: vegetable peels, paper, cotton. Can be composted.
- Non-biodegradable waste: Cannot be broken down easily. Examples: plastics, glass, metals, pesticides. Must be recycled or safely disposed.
Summary
Ecosystems consist of biotic and abiotic components interacting together. Energy flows through food chains and webs, with only 10% transferred per trophic level. Biological magnification concentrates harmful chemicals in top predators. The ozone layer protects Earth from UV radiation but is threatened by CFCs. Proper waste management distinguishes between biodegradable and non-biodegradable waste.
Important Terms
- Trophic Level
- A step in a food chain representing a feeding position (producer, primary consumer, etc.)
- Biological Magnification
- Progressive increase in concentration of non-biodegradable substances through trophic levels
- Ozone Layer
- A protective layer of Oâ in the stratosphere that absorbs UV radiation
- Biodegradable
- Substances that can be decomposed by natural biological processes
- Decomposers
- Organisms like bacteria and fungi that break down dead organic matter
Quick Revision
- Food chain: Producer â Primary consumer â Secondary consumer â Tertiary consumer
- 10% Law: Only 10% energy is transferred to the next trophic level
- Biological magnification: pesticide concentration increases up the food chain
- Ozone depletion caused by CFCs; leads to increased UV radiation
- Biodegradable waste can be composted; non-biodegradable must be recycled or disposed safely