Biology is a process of inquiry. It can start anywhere in the cycle.
Scientists make careful and systematic observations, then they record those observations as data. Scientists then form a hypothesis as a possible answer to a question. Then test their hypotheses and analyze their data.
Scientists develop experiments to test their hypothesis. When conducting experiments independent variables are manipulated, and dependent variables are observed and measured. Constants are conditions that are kept the same.
A theory explains a wide range of observations and experimental results. A theory is supported by a great deal of scientific evidence, because of this theories can change when there is new evidence.