Key terms

BiologyThe study of living things
ObservationNoticing and describing events in an orderly way
HypothesisA scientific explanation that can be tested through experimentation or observation
Controlled experimentAn experiment in which only one variable is changed
Independent variableThe variable that is deliberately changed in an experiment
Dependent variableThe variable this is observed and changes in response to the independent variable
Control groupBaseline group that does not have changes in the independent variable
Scientific theoryA well-tested and widely accepted explanation for a phenomenon
Research biasProcess during which the researcher influences the results, either knowingly or unknowingly
PlaceboA substance that has no therapeutic effect, often used as a control in experiments
Double-blind studyStudy in which neither the participants nor the researchers know who is receiving a particular treatment

The nature of biology

Biology is the branch of science concerned with the study of living things, or organisms. Biologists have identified traits common to all the living organisms that we know. Although nonliving things may show some of these properties, in order for something to be considered living, it must meet all of them.

Properties of life

  1. Organization: Living things are highly organized (meaning they contain specialized, coordinated parts) and are made up of one or more cells.
  2. Metabolism: Living things must use energy and consume nutrients to carry out the chemical reactions that sustain life. The sum total of the biochemical reactions occurring in an organism is called its metabolism.
  3. Homeostasis: Living organisms regulate their internal environment to maintain the relatively narrow range of conditions needed for cell function.
  4. Growth: Living organisms undergo regulated growth. Individual cells become larger in size, and multicellular organisms accumulate many cells through cell division.
  5. Reproduction: Living organisms can reproduce themselves to create new organisms.
  6. Response: Living organisms respond to stimuli or changes in their environment.
  7. Evolution: Populations of living organisms can undergo evolution, meaning that the genetic makeup of a population may change over time.

Scientific methodology

The scientific method involves making observations and asking questions.
Scientists form hypotheses based on these observations and then develop controlled experiments to collecting and analyze data. Using this data, they are able to draw conclusions and form questions for new scientific research.

Scientific method example: Failure to toast

  1. Observation: the toaster won't toast.
  1. Question: Why won't my toaster toast?
  1. Hypothesis: Maybe the outlet is broken.
  1. Prediction: If I plug the toaster into a different outlet, then it will toast the bread.
  1. Test of prediction: Plug the toaster into a different outlet and try again.
And the result is:
Left panel: My bread toasts! Hypothesis is supported. Right panel: My bread still won't toast. Hypothesis is not supported.
  1. Iteration time!
Left panel (in case of hypothesis being supported): But what is actually wrong with the outlet? Right panel (in case of hypothesis not being supported): Hmm...maybe there is a broken wire in the toaster.
Data from many experiments are used to create a better understanding of how the world works and develop scientific theories.

Experimental design

Experimentation is the heart of science. Scientists ask questions, gather evidence, share ideas, and analyze data.
In designing an experiment, the specific question (or questions) that the experiment is meant to answer must first be clearly identified. The independent variable and dependent variable must also be identified, since the goal of a designed experiment is to understand how one variable affects another.
A simple experiment should have only one independent variable. All other factors that could have an effect on the outcome of the experiment must be controlled or held constant. In addition, one group in the experiment should be a control group, a designated group used as a comparative reference point. This group will not have a manipulated independent variable.

Reducing errors and bias

It is important to design an experiment that leads to the most accurate results possible.
Scientists generally aim to be objective, but they are people and have their own likes, dislikes, and personal biases. Because of this, scientific data may be interpreted in different ways by different scientists.
Some ways to avoid this include:
  • Having a large sample size in the experiment: This helps to account for any small differences among the test subjects that may provide unexpected results.
  • Repeating experimental trials multiple times: Errors may result from slight differences in test subjects, or mistakes in methodology or data collection. Repeating trials helps reduce those effects.
  • Including all data points: Sometimes it is tempting to throw away data points that are inconsistent with the proposed hypothesis. However, this makes for an inaccurate study! All data points need to be included, whether they support the hypothesis or not.
  • Using placebos, when appropriate: Placebos prevent the test subjects from knowing whether they received a real therapeutic substance. This helps researchers determine whether a substance has a true effect.
  • Implementing double-blind studies, when appropriate: Double-blind studies prevent researchers from knowing the status of a particular participant. This helps eliminate observer bias.

Communicating findings

In order for research to be accepted, it must be shared within the scientific community. Scientists often collaborate in groups and communicate research with other groups. This communication must follow specific guidelines to make sure that the communication is appropriate.
Publishing research findings in peer-reviewed scientific journals allows scientists to share ideas, and provides other scientists with the opportunity to evaluate and test the data analysis provided.

Things to remember

  • A hypothesis is not necessarily the right explanation. Instead, it is a possible explanation that can be tested to see if it is likely correct, or if a new hypothesis needs to be made.
  • Not all explanations can be considered a hypothesis. A hypothesis must be testable and falsifiable in order to be valid. For example, “The universe is beautiful" is not a good hypothesis, because there is no experiment that could test this statement and show it to be false.
  • In most cases, the scientific method is an iterative process. In other words, it's a cycle rather than a straight line. The result of one experiment often becomes feedback that raises questions for more experimentation.
  • Scientists use the word "theory" in a very different way than non-scientists. When many people say "I have a theory," they really mean "I have a guess." Scientific theories, on the other hand, are well-tested and highly reliable scientific explanations of natural phenomena. They unify many repeated observations and data collected from lots of experiments.