"In a classic study, John Teal measured energy flow in a salt marsh ecosystem. The table below shows some of his results.
a. What percentage of the energy in sunlight was converted into chemical energy and incorporated into plant biomass? What term describes this new biomass?
b. What percentage of the energy in plant biomass was incorporated into the bodies of the primary consumers? What became of the rest of the energy (see Figure 37.16A)?
c. How much energy is available for secondary consumers?
Based on the efficiency of energy transfer by primary consumers, estimate how much energy will be available to tertiary consumers."

Verified step by step guidance

1. Step 1: To calculate the percentage of sunlight energy converted into chemical energy in plant biomass, use the formula: \( \text{Percentage} = \frac{\text{Chemical energy in producers}}{\text{Sunlight energy}} \times 100 \). Substitute the values: \( \text{Chemical energy in producers} = 6,585 \, \text{kcal/m}^2/\text{year} \) and \( \text{Sunlight energy} = 600,000 \, \text{kcal/m}^2/\text{year} \). The term describing this new biomass is 'Gross Primary Production (GPP)'.
2. Step 2: To calculate the percentage of energy in plant biomass incorporated into primary consumers, use the formula: \( \text{Percentage} = \frac{\text{Chemical energy in primary consumers}}{\text{Chemical energy in producers}} \times 100 \). Substitute the values: \( \text{Chemical energy in primary consumers} = 81 \, \text{kcal/m}^2/\text{year} \) and \( \text{Chemical energy in producers} = 6,585 \, \text{kcal/m}^2/\text{year} \). The rest of the energy is lost as heat, used in metabolic processes, or remains as unconsumed biomass.
3. Step 3: To determine the energy available for secondary consumers, note that the energy available to secondary consumers is the energy transferred from primary consumers. This is calculated using the efficiency of energy transfer, which is typically around 10%. Use the formula: \( \text{Energy available for secondary consumers} = \text{Chemical energy in primary consumers} \times \text{Efficiency} \). Substitute \( \text{Efficiency} = 0.10 \).
4. Step 4: To estimate the energy available to tertiary consumers, apply the same energy transfer efficiency (10%) to the energy available for secondary consumers. Use the formula: \( \text{Energy available for tertiary consumers} = \text{Energy available for secondary consumers} \times \text{Efficiency} \).
5. Step 5: Summarize the energy flow: Sunlight energy is converted into plant biomass (Gross Primary Production), a portion of which is transferred to primary consumers, then to secondary consumers, and finally to tertiary consumers, with energy losses at each trophic level due to heat, metabolism, and unconsumed biomass.

Key Concepts

Energy Conversion Efficiency

Energy conversion efficiency refers to the percentage of energy that is transformed from one form to another in an ecosystem. In this context, it measures how much of the sunlight energy is converted into chemical energy by producers (plants). This efficiency is crucial for understanding energy flow in ecosystems, as it determines the amount of energy available for subsequent trophic levels.

Primary Production

Primary production is the process by which autotrophs, primarily plants, convert sunlight into chemical energy through photosynthesis, resulting in new biomass. The biomass produced is referred to as 'net primary production' (NPP), which represents the energy available for herbivores and other consumers. Understanding primary production is essential for analyzing energy flow and ecosystem dynamics.

Trophic Levels and Energy Transfer

Trophic levels represent the hierarchical positions of organisms in an ecosystem based on their feeding relationships. Energy transfer between these levels is typically inefficient, with only a fraction of energy (about 10%) being passed from one level to the next. This concept is vital for estimating the energy available to secondary and tertiary consumers, as it highlights the diminishing energy available at higher trophic levels.