Just like a food chain, energy enters the food web at the trophic level of the producers, which can also be called autotrophs. In the desert, autotrophs are often some type of cactus, grass, or shrub.
The main purpose of the INTRODUCTION is to give a description of the problem that will be addressed. In this section the researcher might discuss the nature of the research, the purpose of the research, the significance of the research problem, and the research question(s) to be addressed. Three essential parts of a good introduction are: RATIONALE.
A final factor in setting the right tone is to determine the purpose of the essay. An author's purpose is the reason for writing. There are three main types of author's purpose: to persuade, to inform or to entertain. If you are trying to convince your reader to believe or to do something, then you are persuading.