Biology and the scientific method review
|Biology||The study of living things|
|Observation||Noticing and describing events in an orderly way|
|Hypothesis||A scientific explanation that can be tested through experimentation or observation|
|Controlled experiment||An experiment in which only one variable is changed|
|Independent variable||The variable that is deliberately changed in an experiment|
|Dependent variable||The variable this is observed and changes in response to the independent variable|
|Control group||Baseline group that does not have changes in the independent variable|
|Scientific theory||A well-tested and widely accepted explanation for a phenomenon|
|Research bias||Process during which the researcher influences the results, either knowingly or unknowingly|
|Placebo||A substance that has no therapeutic effect, often used as a control in experiments|
|Double-blind study||Study in which neither the participants nor the researchers know who is receiving a particular treatment|
The nature of biology
Properties of life
- Organization: Living things are highly organized (meaning they contain specialized, coordinated parts) and are made up of one or more cells.
- 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.
- Homeostasis: Living organisms regulate their internal environment to maintain the relatively narrow range of conditions needed for cell function.
- Growth: Living organisms undergo regulated growth. Individual cells become larger in size, and multicellular organisms accumulate many cells through cell division.
- Reproduction: Living organisms can reproduce themselves to create new organisms.
- Response: Living organisms respond to stimuli or changes in their environment.
- Evolution: Populations of living organisms can undergo evolution, meaning that the genetic makeup of a population may change over time.
Scientific method example: Failure to toast
- Observation: the toaster won't toast.
- Question: Why won't my toaster toast?
- Hypothesis: Maybe the outlet is broken.
- Prediction: If I plug the toaster into a different outlet, then it will toast the bread.
- Test of prediction: Plug the toaster into a different outlet and try again.
- Iteration time!
Reducing errors and bias
- 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.
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.