Final answer:
Decomposers are the missing element from the food web essential for maintaining equilibrium. They recycle nutrients by breaking down dead matter and waste, a process vital for the sustainability of ecosystems.
Step-by-step explanation:
The key component missing from the food web that is essential to maintain equilibrium is Decomposers. These organisms, such as bacteria and fungi, play a critical role in recycling nutrients by breaking down dead organisms and waste materials. Without decomposers, nutrients like carbon and nitrogen would not be released back into the ecosystem, leading to a pile-up of waste and a deficiency of essential nutrients for producers. This would disrupt the balance of the ecosystem and could result in many organisms being unable to survive.
Decomposers contribute to the stability and survival of an ecosystem by ensuring that nutrients are continuously cycled back to be used by producers. They help to break down complex organic matter into simpler substances that can be reabsorbed by plants, supporting various forms of life. Without the actions of decomposers, ecosystems would be unable to sustain themselves over time.