Food chains are ① a way
of sharing out amongst all living things the energy
that plants capture from sunlight. The nutrients plants need in
order to continue growing would soon be used up unless these were
recycled back into the soil ②for plants
to use again. Decomposers--tiny animals, fungi, and
bacteria--have a vital role in breaking-up dead plant and animal
material and releasing ③their locked-up
nutrients back into the soil. Amongst the most important
nutrients for plant growth are nitrates. Although nitrogen gas
makes up four-fifths of the atmosphere, only a few microscopic
plants and animals (micro-organisms) are able to make nitrates
from nitrogen, so they have a very important role as soil enrichers.
Otherwise, plants rely on decomposers to recycle the nitrates
needed ④for their continued growth.