They fill one evolutionary niche in Darwinian reality - the Parasite that extracts resources from its host just long enough to reproduce and find another host. Still other groups see this and take advantage of the situation. Those are the Scavengers, waiting to feast on the carcass of the defeated host. Could also be considered opportunistic feeders.

They fill one evolutionary niche in Darwinian reality - the Parasite that extracts resources from its host just long enough to reproduce and find another host. Still other groups see this and take advantage of the situation. Those are the Scavengers, waiting to feast on the carcass of the defeated host. Both examples of opportunistic feeders.