<u>Species</u>: Example of species are Risso´s dolphin -<em>Grampus griseus</em>-, Bottlenose dolphin -<em>Tursips truncatus</em>-, Killer whale - <em>Orcinus orca</em>-, Squids -<em>Loligo sp.</em>-, hake fish -<em>Merluccius hubbsi </em>-. (Note: Names in italic are the scientific name of each species)
<u>Population</u><u>:</u> Groups of individuals from the same species, with similar characteristics, capable of crossing, leaving offspring and living in the same habitat at the same time. The size of the population can be determined by the researcher or the extension of an investigation. <u>Example of populations</u>: Risso´s dolphin population, Bottlenose dolphin population, Killer whale population. All of these species are sociable or gregarious, forming groups that might be composed of 2 to 200 or more individuals of the same species.
<u>Community</u>: Relationship or interaction between different species groups that live in the same habitat and at the same time. At this level, it is interesting to study inter-specific interactions that could cause changes in the populations´ size. These could be the cases of competition, predation, parasitism, mutualism, and etcetera. In the example of species given before, the three dolphin species interact with each other in different ways. Rissos´dolphin usually interacts in a friendly way with Bottlenose dolphin. It is not rear to see them traveling together in the same group, feeding together and communicating with each other or other dolphin species. They might <u>compete</u> for resources, as sometimes they feed on the <u>same prey</u> (squids or hake fishes) but this is not all the time. On the other hand, Risso´s dolphin and Bottlenose dolphin are one of the Killer whale´s prey, so their interaction with this last one is <u>predator-prey</u><u>.</u> Risso´s dolphin and bottlenose dolphin mus develope strategies, most of them involved with communication, to be aware of the killer whale presence and to be able to scape and protect their calves.
