The Scientific Method
The scientific method is composed of several steps. We have outlined these steps below.
We note that not all biologists will follow this format precisely or in this order but most
researchers go through these steps during the course of their research.
1) Search for information and making observations. (Library, Internet)
A biologist usually begins a research project with a search through the biological literature. They
should be familiar with all articles relevant to their research. The purpose of a literature search is to
find out what is known about a given subject. If you know what is known then you also know
what is unknown. The area that is unknown is where biologists makes new contributions to
their field of study. Support or rejection of earlier ideas is another ongoing part of biological research.
The development of new technologies often provides biologists with new tools to test older ideas.
In both cases, a review of the literature is necessary.
2) Asking questions.
What is the structure of the DNA molecule (Watson and Crick 1953)? Previous studies of DNA
and proteins showed that DNA was the source of the genetic code. However, the structure of
the DNA molecule remained unknown until Watson and Crick (1953) first described the
shape of the double-helix.
What are the symptoms or indicators of human immunodeficiency virus (HIV) infection
(Widi-Wirski et al. 1988)? Ever since the discovery of HIV in the late 1970's, a consensus
on a concise description of the symptoms used to diagnose HIV infection has been lacking
because of the latency of the onset of the disease, the clinical spectrum of symptoms vary
across the world and expensive serological tests available in developed nations are unavailable
in third world countries. Diagnosis of this deadly disease requires an accurate description of
the symptoms that define a patient with HIV. Widi-Wirski et al. (1988) asked questions about
a reliable clinical definition for HIV infection that can be applied throughout the world.
They discuss different clinical definitions used in the literature.
What are current population trends in species of songbirds that breed in North America
(Sauer and Droege 1992)? Each year billions of songbirds migrate from their wintering grounds
in the tropics to North America. They establish nesting territories and produce offspring during
the summer. Then, they return to the tropics to spend the winter. If population ecologists want
to know something about the health of populations of these species they would ask questions
about population trends. Sauer and Droege (1992) asked questions about population trends in
100 species of neotropical migrants on their breeding grounds in North America. They found
that from 1978 - 1988, a majority of species experienced population declines.
How are molecules arranged that would cause the double helix configuration of DNA?
Watson and Crick (1953) discovered how molecules comprising the two strands of
DNA are arranged and how nitrogenous bases hold the two DNA strands together with hydrogen bonds.
How does HIV cause AIDS? After biologists discovered HIV they needed to know
how it caused AIDS. Several investigators (Weiss 1993, Nowak and McMichael 1995)
asked how HIV affects the body and causes AIDS. This lead to the discovery of how
HIV attacks the lymphocytes and destroys the body's immune system.
How has the environment caused changes in songbird populations in the western
hemisphere? When ornithologists observed declining populations of songbirds they
began to ask questions about how changes in the environment could be causing population
declines. Terborgh (1992) has reviewed several hypotheses that might explain these
declines including habitat fragmentation due to human development on the breeding grounds,
deforestation on the wintering grounds in the tropics, increased predation pressure by
avian nest predators (e.g., feral cat, Opossum and Raccoon), pollution, an abundance of brood parasites, and insecticides.
3) Developing testable hypotheses.
4) Test the hypothesis. Use El Nino as an example of how climate may affect fish and seabird populations.
Hypothesis 1: If El Niņo's warming is causing declines in seabird
Prediction: 1) then perturbations in oceanographic measurements
(e.g., temperature, salinity) of the marine ecosystem
should be temporary and followed by a recovery
until the next El Niņo event,
Prediction: 2) then populations of prey species of fish will decline in
response to these changes during El Niņo years
but will recover after each El Niņo event,
Prediction: 3) then seabird predators will be unable to breed because
they can not feed fish to their young during El Niņo
Prediction: 4) then after an El Niņo event, seabird populations will
approach their normal population sizes until the
next El Niņo event.
Hypothesis 2: If overfishing is causing declines in seabird populations,
Prediction: 1) then fish populations will exhibit a continuous
decline and will not recover after an El Niņo
Prediction: 2) then large numbers of seabirds will be unable
to breed because they can not feed fish to their young during El Niņo and normal weather years,
Prediction: 3) then seabird populations of will exhibit a continuous
decline that parallels a continuous decline in prey
species of fish,
Prediction: 4) then seabird populations will not recover to their
average population sizes after an El Niņo event.
5) Collect data.
6) Analyze data.
7) Interpret the results of the analysis.
8) Answer the biological question.
9) Present the results of the research.