the answer for PLATO is:
"Yes, because these organisms likely depend on each other for survival. For example, plants and grasses can make food for insects and other small animals, such as rats. Carnivores can eat the small animals and obtain energy from them. Humans are also living things, sk they contribute to the ecosystems of these organisms. They can provide food for rats and insects. Humans can also water the plants"
Paraphrase that as you will.
The answer is Tyrosine. Conditionally essential amino acids is when non essentials amino acid becomes essential. In Phenylketonuria Tyrosine becomes a conditionally essential amino acid that must be provided in the diet. Phenylalanine accumulates and fails to convert to tyrosine during this condition.
It could be underneath a glacier.