Biology is the study of life. All living things share characteristics like being made of cells, growing, obtaining and using energy, and responding to their environment. Scientists use biology to help solve problems like preserving the environment, improving food supply, understanding genetics, and fighting diseases. The scientific method involves observing the natural world, asking questions, proposing hypotheses to explain observations, experimenting to test hypotheses, and drawing conclusions. Key parts of an experiment include a control group, experimental group, independent variable, and dependent variable. A theory is formed when repeated experiments consistently confirm a hypothesis.