Fallacy
Humans are the apex predator at the top of the food chain, and just like any other being in the circle of life, we kill and eat lesser animals.
Response
The terms 'food chain' and 'food web' refer to a natural ecological system whereby producers in a specific habitat are eaten by consumers in that same habitat. The term 'circle of life' has no scientific meaning at all. In neither case do the terms refer to the human consumption of animals, since humans do not exist as consumers in a natural ecological system where cows, pigs, cats, dogs, fish and other food animals are producers.
The only use of the terms 'food chain' or 'circle of life' in the context of human food choices is to legitimize the slaughter of sentient individuals by calling that slaughter a necessary and natural part of human life, which means the apex predator justification for eating animals is a failure on two fronts. First, the terms themselves either do not apply to the ecological relationship we have with animals or they have no meaning at all. Second, we do not need to eat animals in order to survive, so the underlying moral imperative of 'might makes right' is not ethically defensible. By analogy, a bank robber might claim to be at the top of the corporate ladder since he had the ability to take what belonged to others and chose to do so.