Ecosystem and Nutrient Cycles Worksheet

Which of the following organisms plays a crucial role in denitrification?

• Nitrifying bacteria

• Nitrogen-fixing bacteria

• Denitrifying bacteria

• Decomposers

The primary source of energy for almost all ecosystems on Earth is:

• Chemical energy

• Thermal energy

• Solar energy

• Nuclear energy

In a biomass pyramid, the lowest level is occupied by:

• Primary consumers

• Secondary consumers

• Producers

• Decomposers

Explain the role of decomposers in nutrient cycles. Provide a specific example.

• Decomposers break down dead organisms, returning nutrients to the soil; for example, fungi decomposing a fallen tree.

• Decomposers produce energy through photosynthesis, like plants.

• Decomposers are primary consumers in the food chain, such as herbivores.

• Decomposers are responsible for pollination, like bees.

One way in which the phosphorus cycle differs from the carbon cycle is:

• Phosphorus cycle does not include a gaseous phase.

• Phosphorus cycle involves the atmosphere.

• Phosphorus cycle is faster than the carbon cycle.

• Phosphorus cycle is primarily driven by human activities

A farmer applies nitrogen-based fertiliser to their field. How might this impact the nitrogen cycle and potentially other ecosystems?

• It increases nitrogen levels in the soil, potentially leading to eutrophication in nearby water bodies.

• It decreases nitrogen levels in the soil, reducing plant growth.

• It has no impact on the nitrogen cycle or other ecosystems.

• It completely stops the nitrogen cycle.