Scientific Method and Biological Theories

The Process of Science

  • The scientific method is a standard series of steps used in gaining new knowledge through research.
  • The scientific method can be divided into five steps:
    1. Observation
    2. Hypothesis
    3. Predictions and Experiments
    4. Data Collection and Statistical Analysis
    5. Results and Conclusions

Flow Diagram for Scientific Method

  • Observation leads to potential hypotheses.
  • Hypotheses can be rejected based on experimental results.
  • Remaining possible hypotheses are considered.
  • The last remaining possible hypothesis can be modified.
  • Predictions are made, and experiments are conducted to confirm them.
  • Confirmed predictions lead to a conclusion.

Observations and Hypotheses

  • Observation
    • Scientists use their senses to gather information about a phenomenon or natural event.
  • Hypotheses
    • A hypothesis is a tentative explanation for what was observed.
    • It is developed through inductive reasoning.
    • It is testable.
    • Example: Bumble bees prefer white flowers to orange ones.

Predictions & Experiments

  • An experiment is a series of procedures designed to test a hypothesis.
  • It utilizes deductive reasoning to make a prediction or expected outcome.
  • The manner in which a scientist conducts an experiment is called the experimental design.
  • A good experimental design ensures that the scientist is examining the contribution of a specific variable, called the experimental (independent) variable, to the observation.
  • The independent variable is the factor being tested.

Predictions and Experiments

  • A test group is exposed to the experimental variable.
  • A control group goes through all aspects of the experiment but is not exposed to the experimental variable.
  • If the control and test groups show the same results, the hypothesis is not supported.
  • The data are the results of an experiment.
  • Results should be observable and objective.
  • Tables and graphs are two possible formats for data.

Presenting and Analyzing Data

  • Statistical Data
    • Data are analyzed using statistics.
  • Measures of variation
    • Standard error: How far off the average of the data is
  • Statistical Significance
    • Probability value (p)
    • Less than 5% is acceptable (p < 0.05)
    • The lower the p value, the greater the confidence in the results

Presentation of Scientific Data

  • Example of a graph presenting scientific data with x and y axes. The y-axis represents blood cholesterol levels (mg/dL) and the x-axis represents weeks.
  • The graph shows variation in blood cholesterol levels with standard error indicated.

Conclusions and Peer Review

  • The data are interpreted to determine whether the hypothesis is supported or not.
  • If prediction happens, hypothesis is supported.
  • If not, hypothesis is rejected.
  • Findings are reported in scientific journals.
  • Peers review the findings.
  • Other scientists then attempt to duplicate or dismiss the published findings.

Scientific Publications

  • Once the data have been analyzed, it is usually published in scientific journals.
  • Not all studies are accepted by journals. They must be reviewed by experts first.

Scientific Theory Versus Law

  • Scientific Theory: Concepts that join together two or more well-supported and related hypotheses.
    • Supported by a broad range of observations, experiments, and data.
  • Scientific Principle / Law: Widely accepted set of theories.
    • No serious challenges to validity.

Basic Theories of Biology

  • Cell Theory: All organisms are composed of cells, and new cells come only from preexisting cells.
  • Homeostasis: The internal environment of an organism stays relatively constant—within a range that is protective of life.
  • Evolution: All living organisms have a common ancestor, but each is adapted to a particular way of life.