AP Biology/The Science of Biology

Study Time | 2 minutes. (This should be common knowledge for most. Review the keywords you need to, and skip to the next chapter.)


Biology Predictions
Properties of Life Theory
Homeostasis Scientific Method
Deductive Reasoning Control Experiment
Inductive Reasoning Control
Observation Variable
Inference Research
Hypothesis (Accepted/Rejected) Scientific Journal
Experiment Peer Review

What is Biology?Edit

Biology is the study of living things, literally the science of life. Though there is disagreement, five characteristics that usually define life are:

  1. Order - All organisms are cellular, with one or more, and are highly structured. Atoms create organic molecules, which combine into macromolecules, which construct cellular organelles, and so on. There is a rising hierarchy of order to life. Cells form tissues, which make up organs, which are part of organ systems, which work together to form a complex organism.
  2. Sensitivity - Organisms respond to their environment, or stimuli.
  3. Growth, development, and reproduction - The ability to grow and reproduce are fundamental traits inherent to all organisms. Organisms also possess hereditary molecules (usually DNA) that are passed to offspring.
  4. Regulation - Regulatory mechanisms coordinate an organism's internal functions, including food intake, waste disposal, and many more.
  5. Homeostasis - All organisms are capable of maintaining relatively constant internal conditions, different from their environment. The ability to maintain this internal balance is called homeostasis.

Scientific ReasoningEdit

Science is a methodology for learning about the world. The scientific method deals with systematic investigation, reproducible results, the formation and testing of hypotheses, and reasoning. Reasoning can be broken down into two categories: induction and deduction. Most reasoning in science is done through induction.

Inductive ReasoningEdit

Definition: Determining a general statement from several facts. (Not always accurate)
Example: We have had a test every Tuesday for the past three months; therefore, we will have a test next Tuesday (and all Tuesdays).

Deductive ReasoningEdit

Definition: Determining a single fact from a general statement. (Only as accurate as the statement)
Example: The teacher said she checks homework every Monday; therefore she will check homework on next Monday.

The Scientific MethodEdit

The scientific method is not a step by step, linear process. It is an intuitive process, a methodology for learning about the world through the application of knowledge. Scientists must be able to have an "imaginative preconception" of what the truth is. Scientists will often observe and then hypothesize the reason why a phenomenon occurred. They use all of their knowledge and a bit of imagination, all in an attempt to uncover something that might be true. A typical scientific investigation might go like so:

You observe that a room appears dark, and you ponder why the room is dark. In an attempt to find explanations to this curiosity, your mind unravels several different hypotheses. One hypothesis might state that the lights are turned off. Another hunch might be that the room's light bulb has burnt out. Worst yet, you could be going blind. To discover the truth, you experiment. You feel your way around the room and find a light switch and turn it on. No light. You repeat the experiment, flicking the switch back and forth. Still, nothing happens. Your initial hypothesis (the room is dark because the lights are off) has been rejected. You devise more experiments to test your hypotheses, utilizing a flashlight to prove that you are indeed not blind. In order to accept your last remaining hypothesis as the truth, you predict that changing the light bulb will fix the problem. It does. Another prediction you could make is that the light will not work in another socket because it is burnt out. This is easily testable. If all of your predictions succeed, the original hypothesis is considered valid and is accepted, usually after repetitive testing. In some cases, however, your predictions will not be correct, and you'll have to start over. You can see how there can never really be a degree of absolute certainty, but if the bulb does not work in all sockets and replacing it fixes the original problem, we can be reasonably certain that the bulb was burnt out.
How Science is Done
A diagram that illustrates scientific investigation

The general process is summed up by this diagram. Scientists first make observations that raise a particular question. In order to explain the observed phenomenon, they develop a number of possible explanations, or hypotheses. This is the inductive part of science, observing and constructing plausible arguments for why an event occurred. Experiments are then used to eliminate one of more of the possible hypotheses until there one hypothesis remains. Using deduction, scientists use the principles of their hypothesis to make predictions, and then test to make sure that their predictions are confirmed. After many trials (repeatability) and all predictions have been confirmed, the hypothesis then may become a theory.

Quick Definitions

Observation - quantitative and qualitative measurements of a particular phenomenon.
Inference - deriving new knowledge based upon old knowledge.
Hypotheses - a suggested explanation.
Rejected Hypothesis - an explanation that has been ruled out through experimentation.
Accepted Hypothesis - an explanation that has not been ruled out through excessive experimentation and makes verifiable predictions that are true.
Experiment - A test that is used to rule out a hypothesis or validate something already known.
Scientific Method - The process of scientific investigation.
Theory - A widely accepted hypothesis that stands the test of time. It has withstood many attempts at falsification.


As our ability to manipulate life in profound ways has increased with the advent of technologies like genetic modification, pharmacology, and cloning, we as a species have taken upon ourselves the obligation to be responsible with our power. Given our understanding of the processes that allow life to exist, we must use our knowledge to advance humanity. The study of this responsibility is called bioethics.