Your parents probably told you from a young age to wash your hands often in order to avoid germs. But what are germs, exactly? Where are they commonly found? If you plan to address germs in your biology experiment, try taking swabs of commonly handled public objects, such as doorknobs and rails on public transportation. Examine the swabs under a microscope and identify the germs found there by using your biology textbook for research. Determine which germs from your swab are harmful, how common they are and the number of different germs you've found on each of your chosen surfaces.
You can use yourself in an experiment to determine the way that human kidneys work. Select five different digestible liquids, such as water, soda, juice, tea and coffee. Ingest a set amount of each of your chosen liquids -- for instance, a standard eight fluid ounces -- first thing in the morning before drinking any other liquids over the course of five days. Keep a chart that records the time between consumption and urination, the color of the resulting urine and the pH levels of the urine. Urine that is darker tends to have lower pH levels while lighter urine has higher pH levels. You can then test the pH level using pH strips from your school laboratory (they're also readily available for order over the Internet). A healthy pH reading is 7.5 or higher. The data from this experiment will help you determine which liquids are good for your body's functionality.
Study how mold is contingent on different environmental conditions. Take leftover food, cut it into three different pieces and place each piece on three separate but identical plates. Place each plate in three different climates, such as a refrigerator, a dark corner of a room and a place where the food will be exposed to direct sunlight for several hours a day. Using your magnifying glass, observe mold growth on the food in each of the environments over a period of two weeks. Note your observations on three identical charts and compare the collected data at the end of 14 days. In which atmosphere does mold grow the fastest? In which environment did the mold appear first? Write additional questions and record the answers you've discovered about each individual piece of food.
Grow plants of the same species using different liquids and sources of light to nourish them. How fast and in what way does the same plant grow when being fed with bottled water versus tap water and/or natural light versus artificial light? Create a chart for your observations and take photos documenting each step of the growth process.