Activities

Activity 1: Comparing Ecosystem Components

Aim: To identify and compare the biotic and abiotic components of different ecosystems.

Procedure:

1. Observe a small pond and a local garden (or forest patch).
2. List the following for each:
   • Abiotic factors: (e.g., Water turbidity, soil texture, sunlight intensity).
   • Producers: (e.g., Phytoplankton vs. Trees).
   • Consumers: (e.g., Zooplankton/Fish vs. Insects/Birds).
   • Decomposers: (e.g., Bottom-dwelling fungi vs. Earthworms).
3. Discuss the role of stratification in the terrestrial ecosystem.

Conclusion: Every ecosystem, regardless of size, functions through the interaction of its specific biotic and abiotic members.

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Activity 2: Calculating Energy Flow (10% Law)

Aim: To practice calculating energy transfer across trophic levels.

Procedure:

1. Assume a grassland ecosystem where the producers capture 1,000,000 Joules of solar energy.
2. Calculate the energy available at each level:
   • Producers (1st Trophic Level): 1% of solar energy = 10,000 J.
   • Primary Consumers (Herbivores): 10% of 10,000 J = 1,000 J.
   • Secondary Consumers (Carnivores): 10% of 1,000 J = 100 J.
   • Tertiary Consumers (Top Carnivore): 10% of 100 J = 10 J.
3. Discuss why most food chains are limited to 4–5 levels.

Conclusion: Energy decreases significantly at each level, limiting the number of trophic levels an ecosystem can support.

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Activity 3: Mapping the Decomposition Cycle

Aim: To visualize the stages of decomposition in a terrestrial ecosystem.

Procedure:

1. Study Figure 12.1 in the textbook.
2. Describe the journey of a fallen leaf:
   • Fragmentation: Eaten by earthworms.
   • Leaching: Minerals enter soil via rain.
   • Catabolism: Fungal/Bacterial action.
   • Humification: Formation of humus.
   • Mineralisation: Nutrients returned to soil for plants.
3. Discuss how temperature and moisture affect the speed of this cycle.

Conclusion: Decomposition is a critical recycling process that converts "dead" matter back into "live" nutrients.

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Activity 4: Inquiry into the Inverted Pyramid Paradox

Aim: To research why the pyramid of biomass in the sea is often inverted.

Procedure:

1. Define the "standing crop" of phytoplankton.
2. Research the "turnover rate" of phytoplankton vs. fishes.
3. Explain the paradox: How can a small biomass of producers support a larger biomass of consumers?
   • Clue: Fast reproduction and high productivity of phytoplankton compensate for their low standing biomass.

Conclusion: Inverted pyramids occur when the reproductive rate of the lower level is exceptionally high.