Nitrogen-rich compounds found in animal waste or the remains of dead plants and animals are converted to <u>ammonium ions</u> by decomposer bacteria.
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In biology, the biotic factors pertain to the living components of Earth while the abiotic factors are those non-living chemicals and physical factors. The only choice that is not an interaction between biotic and abiotic factors is the third choice, "C. male elk fighting over a female".
The answer would be yeast