There is also an importantconcept to take into consideration when working with predator-prey relationships. It is that all animals are predators as well as prey for other predators. Since this is possible, this leads to a second consideration that a predatoris a meal for another predator or further known as a cycle in the foodweb. The morphological level examinesherbivore prey selection by carnivores to distinguish what size of preyis most valuable to the predator. An example of this is stream systemswith different sizes of fish and how they react to each other.
Thebehavioral level views the changes in herbivore vigilance and activityinduced by predators.
A certain experiment consisted of a spider, grasshopper, and any grassor herb, in which there was a control spider and a treated spider. The population level demonstrates the direct effects of predation and predationrisk on population of herbivore prey. This consists of terrestrialsystems having a certain population of a species that fills a spatial scale. The last is the food web level where there is a chain of predators preyingon predators. It is well established that predators can exerta great amount of pressure on prey populations in a natural community.