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1. Interdependence of Organisms

• All organisms depend on each other and their environment to survive. This relationship is called interdependence.
• Ecosystem: A community of living organisms interacting with each other and their non-living environment.
• Biotic Factors: Living components (e.g., plants, animals, bacteria).
• Abiotic Factors: Non-living components (e.g., sunlight, water, soil, temperature).

2. Energy Flow in an Ecosystem

• Energy Source: The Sun is the primary source of energy for most ecosystems.
• Producers (Autotrophs):
  • Organisms like plants and algae that produce their own food through photosynthesis.
  • Convert solar energy into chemical energy (glucose).
• Consumers (Heterotrophs):
  • Organisms that eat other organisms to obtain energy.
  • Classified into:
    • Primary Consumers: Herbivores that eat plants (e.g., rabbits, caterpillars).
    • Secondary Consumers: Carnivores that eat herbivores (e.g., foxes, frogs).
    • Tertiary Consumers: Top predators that eat secondary consumers (e.g., hawks, lions).
• Decomposers:
  • Organisms like fungi and bacteria that break down dead material, returning nutrients to the soil.

3. Food Chains and Food Webs

• Food Chain:
  • A linear sequence showing how energy flows through an ecosystem.
  • Example: Grass → Rabbit → Fox.
• Food Web:
  • A network of interconnected food chains, showing how organisms have multiple feeding relationships.
  • More realistic than a food chain.

4. Energy Loss

• Energy is lost at each trophic level:
  • Only about 10% of the energy is transferred to the next level.
  • Most energy is lost as heat or used for life processes (e.g., movement, reproduction).
• This limits the number of trophic levels in an ecosystem.

5. Cycles of Matter

• Matter (e.g., water, carbon, nitrogen) cycles through ecosystems, ensuring resources are reused.

Water Cycle:

1. Evaporation: Water from oceans, lakes, and rivers turns into vapour.
2. Condensation: Water vapour cools and forms clouds.
3. Precipitation: Water falls as rain, snow, or sleet.
4. Collection: Water returns to oceans, rivers, or underground reservoirs.

Carbon Cycle:

• Carbon moves between the atmosphere, organisms, and Earth.

1. Photosynthesis: Plants absorb CO₂ and convert it into glucose.
2. Respiration: Organisms release CO₂ back into the atmosphere.
3. Decomposition: Decomposers break down dead organisms, releasing CO₂.
4. Combustion: Burning fossil fuels releases stored carbon into the atmosphere.

Nitrogen Cycle:

• Nitrogen is essential for proteins and DNA in organisms.

1. Nitrogen Fixation: Bacteria convert nitrogen gas (N₂) into forms plants can absorb.
2. Assimilation: Plants take up nitrogen compounds through their roots.
3. Decomposition: Dead organisms and waste return nitrogen to the soil.
4. Denitrification: Bacteria convert nitrogen compounds back to N₂ gas.

6. Examples of Interdependence

• Pollination: Bees depend on flowers for nectar, and flowers depend on bees to spread pollen.
• Predator-Prey Relationships: Wolves control deer populations, preventing overgrazing.
• Symbiosis:
  • Mutualism: Both species benefit (e.g., clownfish and sea anemones).
  • Commensalism: One species benefits, the other is unaffected (e.g., barnacles on whales).
  • Parasitism: One species benefits at the expense of the other (e.g., fleas on dogs).

7. Importance of Biodiversity

• Biodiversity ensures the stability of ecosystems by:
  • Supporting food webs.
  • Providing resources like food, medicine, and materials.
  • Helping ecosystems recover from disturbances (e.g., natural disasters).

Summary

• Organisms rely on each other and their environment in complex relationships.
• Energy flows through ecosystems via food chains and webs, with energy loss at each level.
• Matter cycles (e.g., water, carbon, nitrogen) ensure the availability of essential elements.
• Biodiversity and interdependence are critical for ecosystem stability and resilience.