What is the general role of keystone species in an ecosystem?

Eutrophication is the over-enrichment of water with nutrients, leading to excessive algae growth.

Symbiotic bacteria, involved in the nitrogen cycle, are found in... 

Nitrogen can be fixed by thunder. 

Ecotourists may pick plants of interest from ecotourism sites.

Which process converts carbon in dead organisms back into atmospheric carbon?

Look at the diagram below showing a nutrient cycle in an environment and

use it to answer the questions that follow.

Look at the diagram below showing a nutrient cycle in an environment. Identify the nutrient cycle.

Study the list of terms below.

(i) Photosynthesis

(ii) Respiration

(iii) Combustion

(iv) Decomposition

Which process(es) use(s) oxygen and release(s) carbon dioxide? Choose the most accurate option from those provided.

Precipitation forms part of the following nutrient cycle: