Define species, population, community, and ecosystem.

A species is a group of organisms that can breed together to produce fertile offspring
populations are all the organisms of one species in a habitat at a given time
a community is the populations of different species in a habitat 
an ecosystem is all the organisms living in a particular area and all the abiotic conditions. 

That result from subduction of oceanic plates beneath lighter continental plates. most of the earth's volcanoes are located around the pacific ring of fire because that the location of most of the earth's subduction zones.

Mgo2 is the oxidation state of manganese oxide