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 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 Questions



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.