Some species are so important in their environment, without them certain ecosystems would simply collapse. Their niches include skills in population control, engineering, habitat construction, and home building. This 4-class period, 5-E Model science unit for Grades 4-5 includes an introduction to Keystone Species, examples and explanations of why these organisms are so important, vocabulary, the how and why behind what we can do to help, Expository Writing, 3 Journal Entries, pencil & paper