Review: Food Webs
L2 Decay and Recycling Organic Waste
Learning Objectives:
1. Describe the process of decay and what organisms are responsible.
2. Explain the conditions needed for decay to happen.
3. Analyse why the process of decay is so important.
Decay
• Nutrients are taken in by plants and passed
to consumers through the food chain.
• Where do the nutrients go next?
• Decay = process of decomposition, breaking
down waste and dead plants and animals
back into nutrients
The Decay Process
• Decomposers = group of organisms that break
down waste and dead animals and plants
• Detritus feeders = type of decomposer, animals
that starts the process of decay by eating waste
and dead animal and plant remains (examples:
maggots and some worms)
• Bacteria and fungi decomposers finish the job.
Decay = Recycling Nutrients
• Decomposers digest waste and dead plants and
animals and release waste products; water, carbon
dioxide, and mineral nutrients plants can absorb.
• Decay is an extremely important part of the
ecosystem.
• Decomposers recycle nutrients back into the soil for
plants, ensuring that there are enough nutrients to
start the food chain again.
• Decomposers also remove organic waste, preventing
the ecosystem from filling up with organic waste.
Conditions for Decay
• Warm conditions speed up the chemical
reactions for decay.
• Too cold and it will be very slow (that’s why
we use refrigerators)
• Too hot and the microorganisms
(decomposers) will die
• Most microorganisms grow better in moist
conditions.
• Access to oxygen is necessary as
decomposers use respiration for energy.
Uses for Decomposition
• Sewage treatment plants use
microorganisms to break down human
waste so that it is safe to release back
into environment.
• Compost heaps decompose plant
material and food waste into nutrients
that can be used as fertiliser for gardens.
Review: Carbon Cycle