Practice Questions

Name the five important steps in the process of decomposition.

Recall the percentage of incident solar radiation that constitutes Photosynthetically Active Radiation (PAR).

Justify the characterization of an aquarium as a 'man-made ecosystem'. Evaluate its self-sustainability.

Define 'standing crop' as it relates to an ecosystem.

Identify the primary producers in a typical aquatic ecosystem like a pond.

Critique the use of a pyramid of numbers to represent the structure of an ecosystem with a single large tree as the producer.

Evaluate the statement: 'A food web is simply a collection of isolated food chains.' Justify your evaluation.

A sparrow eats seeds and insects. Analyze its position in the food web by identifying the different trophic levels it can occupy.

Name two climatic factors that regulate the rate of decomposition in an ecosystem.

Apply the 10 percent law of energy transfer to determine the amount of energy available to a secondary consumer if the producer level has $10,000$ J of energy.

Critique the statement: 'Gross Primary Productivity (GPP) represents the energy available to consumers.'

A grassland ecosystem has a Net Primary Productivity (NPP) of $8000 \text{ kcal m}^{-2} \text{yr}^{-1}$. If the respiration loss (R) by the producers is $2000 \text{ kcal m}^{-2} \text{yr}^{-1}$, calculate the Gross Primary Productivity (GPP) for this ecosystem.

Analyze why the pyramid of energy is always upright and can never be inverted.

Analyze why measuring biomass in terms of dry weight is considered more accurate than using fresh weight.

Contrast primary productivity and secondary productivity. Provide an example for an organism responsible for each in a pond ecosystem.

Evaluate why measuring biomass as dry weight is a more accurate method for comparing trophic levels than using fresh weight.

What is the approximate annual net primary productivity of the whole biosphere in terms of dry weight?

Explain the relationship between Gross Primary Productivity (GPP), Net Primary Productivity (NPP), and Respiration (R). Include the formula that connects them.

Describe what a detritus food chain (DFC) is and name the group of organisms that initiate it.

Define primary productivity and state the units in which it is commonly expressed to compare different ecosystems.

Describe the structure of a pond ecosystem by listing and explaining its abiotic and biotic components.

Explain the term 'stratification' as it relates to an ecosystem and provide an example from a forest ecosystem.

Define 'humification' as a process in decomposition.

List the three main types of ecological pyramids and describe what each one represents.

Compare and contrast the Grazing Food Chain (GFC) and the Detritus Food Chain (DFC) based on their starting material and primary energy source in a terrestrial ecosystem.

Examine the statement: 'Decomposition is largely an oxygen-requiring process.' Justify this by explaining what happens to the rate of decomposition in anaerobic conditions and why.

Compare the pyramid of numbers for a grassland ecosystem with one that starts with a single large tree. Draw and label the shapes of both pyramids to demonstrate the difference.

Propose a reason why the pyramid of energy is always upright and can never be inverted. Justify your proposal with the Second Law of Thermodynamics.

Justify why a terrestrial ecosystem, unlike an aquatic one, has a much larger fraction of energy flowing through the detritus food chain (DFC) than the grazing food chain (GFC).

Propose how human beings can function at more than one trophic level simultaneously within their diet. Create an example food web to illustrate your point.

The annual Gross Primary Productivity (GPP) of a forest ecosystem is $1.5 \times 10^6 \text{ g m}^{-2} \text{yr}^{-1}$. The plants in this ecosystem use $6 \times 10^5 \text{ g m}^{-2} \text{yr}^{-1}$ for their metabolic activities (respiration). Calculate the Net Primary Productivity (NPP) and determine the biomass available to herbivores.

A scientist claims that introducing a highly efficient decomposer species into a cold, anaerobic marshland will significantly increase its nutrient cycling rate. Critique this claim, justifying your reasoning with principles of decomposition.

Create a hypothetical food chain for a marine ecosystem with four trophic levels. If the primary producers have a total biomass of $10,000 \text{ kg}$, calculate the approximate biomass available for the top carnivore, justifying your calculation with the 10% law.

Compare and contrast the key features of a terrestrial ecosystem (e.g., a forest) and an aquatic ecosystem (e.g., a pond). Analyze how the abiotic factors in each system shape their respective biotic communities.

If the annual net primary productivity of the entire biosphere is approximately 170 billion tons, and oceans contribute 55 billion tons despite covering 70% of the Earth's surface, analyze one key reason for this lower productivity in oceans.

Formulate a hypothesis explaining the low primary productivity of the deep sea hydro-thermal vents ecosystem despite its high biodiversity.

Summarize the key differences between a grazing food chain (GFC) and a detritus food chain (DFC).

Explain why the pyramid of energy is always upright. Also, explain the 10 percent law of energy transfer between trophic levels.

A simple food chain consists of grass, grasshopper, frog, and snake. If the grass (producer) captures $20,000$ J of solar energy, calculate the energy that would be available to the snake (tertiary consumer). Demonstrate the flow of energy through the trophic levels, assuming the 10 percent law applies at each transfer. Analyze why the length of food chains is generally limited.

In an aquatic ecosystem, the biomass of zooplankton is found to be $21 \text{ kg m}^{-2}$, while the biomass of phytoplankton is $4 \text{ kg m}^{-2}$. Analyze this situation and explain what type of biomass pyramid would be formed and why this is possible.

Design a simple, closed-system experiment to demonstrate the concept of Net Primary Productivity (NPP) using a common aquatic plant like Hydrilla. Formulate the equation you would use to determine NPP.

Design a study to evaluate the impact of introducing an invasive herbivore species into a grassland ecosystem. What key ecological parameters would you measure to assess the changes?

Examine the process of decomposition by explaining the five key steps involved. How do climatic factors like temperature and soil moisture influence this process?

Evaluate the paradox of the inverted pyramid of biomass in a marine ecosystem, where the biomass of fishes far exceeds that of phytoplankton. Justify how this is possible.

Propose a management plan for a large lake that is experiencing eutrophication due to agricultural runoff, with the goal of restoring its original productivity levels. Justify each step of your plan.