Question

part 2. quantifying energy flow and the rule of 10 percent
food chains and webs
three hundred trout are needed to support one man for a year. the trout, in turn, must consume 90,000 frogs, that must consume 27 million grasshoppers that live off of 1,000 tons of grass.
-- g. tyler miller, jr., american chemist (1971)
only a small fraction of energy available at any trophic level is transferred to the next trophic level. that fraction is estimated to be about 10 percent of the available energy. the other 90 percent of the energy is needed by organisms at that trophic level for living, growing, and reproducing.
this relationship is shown in the energy pyramid above. it suggests that for any food chain, the primary producer trophic level has the most energy and the top trophic level has the least.

1. why is a pyramid an effective model for quantifying energy flow?
2. place the organisms from your original food chain on the pyramid provided.
3. using the rule of 10 percent in energy transfer, record the species names for each trophic level and the amount of energy available at that level if your producer level had 3,500,000 kilocalories of energy/area.
4. in one or two sentences, describe how the available energy may affect the population sizes of organisms at different trophic levels.

Explanation:

Question 8:

• Step1: Visual representation

A pyramid visually shows the decrease in energy at each trophic level. As you move up the pyramid, the width (representing energy) gets smaller, clearly indicating the 10 - percent energy transfer rule.

• Step2: Hierarchical structure

It represents the hierarchical nature of food chains. Producers at the base have the most energy, and top - level consumers have the least, which is easily understandable in a pyramid shape.

Question 10:

• Step1: Primary consumers

If the producer level has 3,500,000 kilocalories of energy/area, for primary consumers (10% energy transfer), the energy available is $3,500,000\times0.1 = 350,000$ kilocalories.

• Step2: Secondary consumers

For secondary consumers, the energy is $350,000\times0.1=35,000$ kilocalories.

• Step3: Tertiary consumers

For tertiary consumers, the energy is $35,000\times0.1 = 3,500$ kilocalories.

Question 11:

• Step1: Energy - population relationship

The amount of available energy limits the population size. Higher trophic levels have less energy, so they can support fewer individuals compared to lower trophic levels with more available energy.

Answer:

Question 8: A pyramid is effective because it visually represents the decrease in energy with each trophic level and the hierarchical structure of food chains.
Question 10:

• Producers: 3,500,000 kilocalories, species name (e.g., grass if it's the producer in the food - chain).
• Primary consumers: 350,000 kilocalories, species name (e.g., grasshoppers).
• Secondary consumers: 35,000 kilocalories, species name (e.g., frogs).
• Tertiary consumers: 3,500 kilocalories, species name (e.g., trout).

Question 11: The available energy limits population size; higher trophic levels have less energy and support fewer individuals than lower trophic levels.