Ecosystems, abiotic and biotic factors: Practice Questions

Which of the following describes a mutualistic relationship within an ecosystem?

A scientist is monitoring a river for pollution. They observe high populations of freshwater shrimps and stonefly larvae at site A, but only bloodworms and sludgeworms at site B, which is downstream from a sewage pipe. What can be concluded about the pollution levels at site B based on these indicator species?

A sample of organic waste in a compost bin has an initial mass of \( 45\text{ kg} \). After 12 days, the mass is \( 39.6\text{ kg} \). Calculate the rate of decomposition in grams per hour.

Which of the following biological factors is likely to have the greatest negative impact on global food security in the coming decades?

In the nitrogen cycle, specific bacteria play a role in converting different nitrogen compounds. Which process is carried out by nitrifying bacteria?

Identify one indicator species used to detect clean water and state what its presence indicates about the oxygen levels in that environment.

In a small woodland ecosystem, the total biomass of the producers is measured at \(5000\text{ kg}\). The primary consumers that feed on these producers have a total biomass of \(450\text{ kg}\).
a) Calculate the efficiency of biomass transfer from the producers to the primary consumers. Give your answer as a percentage.
b) Explain two reasons why a large proportion of the biomass is not transferred to the next trophic level.
c) Describe how this loss of energy affects the maximum length of a food chain in an ecosystem.

The diagram represents the nitrogen cycle in a meadow ecosystem. A farmer decides to plough the field, which improves aeration of the soil.

a) Name the group of bacteria that convert ammonia into nitrates in well-aerated soils.
b) Explain why the process of denitrification is reduced when the soil is well-aerated.
c) The farmer then adds a synthetic fertilizer containing nitrates. Describe how the over-use of these fertilizers can lead to eutrophication in a nearby pond and the subsequent death of fish.
d) Identify one species that could act as an indicator species for high levels of water pollution in that pond.