The independent variable is what the scientist has opted to change. The scientist will observe and see what happens once that change has been made. A great experiment to help better understand the independent variable would be the Pea Plant Experiment. The Austrian monk cross-pollinated pea plants, trying to establish which characteristics were passed down through the generations. In this case, the inheritable characteristic of the parent plant was the independent variable. For example, when plants with green seedpods were crossed with plants with yellow seedpods, pod color was the independent variable (1). A dependent variable is when the scientist will observe responses from any changes that were made to the independent variable. If you open a faucet (the independent variable), the quantity of water flowing (dependent variable) changes in response--you observe that the water flow increases. The number of dependent variables in an experiment varies, but there is often more than one (2). A dependent variable can completely change ones experiment from the dependent variable completely changes. This in turn, can be a very eye-opening experiment. Controlled variables (also known as constant variables) are the variables in an experiment that do not change. For example, if you are doing an experiment measuring the fizz released from different types of soda, you might control the size of the container so that all brands of soda would be in 12-oz cans. If you are performing an experiment on the effect of spraying plants with different chemicals, you would try to maintain the same pressure and maybe the same volume when spraying your plants (3). In my personal opinion, I am very fascinated with each variable, however, I would have to say that the controlled variable sparks my interest a bit more. The reason being is that it remains consistent and you, as the scientist, are in ‘control’ of your experiment.
(1) (https://explorable.com/independent-variable)
(2) (http://www.sciencebuddies.org/science-fair-projects/project_variables.shtml)
(3) (http://chemistry.about.com/od/introductiontochemistry/a/What-Is-An-Experiment.htm)

Experiments have often allowed us to see that principles are right. I have read in our chapters, that in speaking about principles strictly dealing with Biology as the subject, there a few different ‘Principles of Biology.’ They are as follows: cell theory, gene theory, evolution, homeostasis, and thermodynamics. I am sure that a lot, if not all, of these principles ring a bell to you, as we reviewed almost all of them during the first few chapters this week. A belief is a more personal. It has a lot to do with a persons attitude