1.  Nitrate is essential to plants because it provides nitrogen that the plant needs to build amino acids which in turn are built into proteins. What would happen to aquatic plants in a lake if the lake is downhill from a farm where a farmer sprays large quantities of nitrate fertilizer? How would this affect the ecosystem in the lake?   
What am I being asked to do? Create a constructed response to answer the questions
What information from the question do I need in order to answer this question? Need to know specifically what questions are being asked (2 questions)
What information from our unit of study applies to this question? Since the question asks about nitrate fertilizer, we need to look at the nitrogen cycle
What is the correct answer? One possible correct answer: “Since nitrate fertilizer provides nitrogen to plants to build proteins, and since the lake is downhill from where the fertilizer is sprayed, water and/or irrigation may wash excess fertilizer down to the lake and promote growth of aquatic plants. (Now, question 2): “The overgrowth of plants may crowd out other organisms, like fish, that need space in which to live and oxygen, therefore some species may die.
How did I get that answer? Applied the knowledge of the nitrogen cycle and deductions about the effect of fertilizers and the fact that water will run into the lake and make projections on the growth of plants