The Scientific Method: Principles and Application in Biology

Lecture 2: The Scientific Method

What is Science?

Science is the systematic study of the natural world through observation and experimentation. It aims to acquire reliable knowledge about the universe by following structured processes.

• Science seeks to explain natural phenomena using evidence-based methods.

• The primary process used to acquire scientific knowledge is the scientific method.

The Scientific Method: A Process for Testing Ideas

The scientific method is a logical, cyclical process used to investigate questions and test hypotheses about the natural world. It consists of several key steps:

• Observe and generalize: Gather data and look for patterns or trends.

• Formulate a hypothesis: Propose a tentative explanation or prediction based on observations.

• Make a testable prediction: Develop predictions that can be evaluated through experimentation or further observation.

• Experiment or observe: Design and conduct experiments or make additional observations to test the predictions.

• Modify the hypothesis and retest as needed: Revise the hypothesis based on results and repeat the process to refine understanding.

Reasoning in Science

Two main types of reasoning are used in the scientific method:

• Inductive reasoning: Making broad generalizations from specific observations.

• Deductive reasoning: Drawing specific conclusions from general principles or premises.

Example of Inductive Reasoning:

• Observation: "Every winter in the past was colder than the preceding summer."

• Generalization: "Winter will always be colder than summer."

Example of Deductive Reasoning:

• If all birds have feathers and robins are birds, then robins have feathers.

• Logical form: If A = B and B = C, then A = C.

Formulating a Hypothesis

A hypothesis is a tentative statement about the natural world that can be tested through experimentation or observation.

• Hypotheses should be based on prior knowledge and observations.

• They must be testable and falsifiable.

Example: Global climate change is caused by increased $CO_2$ levels in the atmosphere, primarily due to human activities.

Making a Testable Prediction

Predictions are specific statements that can be tested to support or refute a hypothesis.

• Predictions are often phrased as "if...then" statements.

• They are derived using deductive reasoning.

• Predictions must be tested under various conditions to ensure reliability.

Example: If rooting hormones promote root growth, then plants treated with rooting hormones will develop longer roots than untreated plants.

Experimentation and Observation

Experiments are carefully planned and executed manipulations of variables to test predictions.

• Independent variable: The factor intentionally manipulated in an experiment.

• Dependent variable: The observed change or response caused by manipulation of the independent variable.

• Controlled experiment: All variables except the one being tested are kept constant.

Modifying the Hypothesis and Retesting

Based on experimental results, hypotheses may need to be revised and retested.

• If a prediction is false, the hypothesis must be modified.

• If a prediction is true, further testing is usually needed to draw a final conclusion.

• The process is iterative and may require multiple cycles of testing and revision.

Example: Testing a Hypothesis in Plant Growth

Researchers hypothesized that rooting hormones would stimulate the production of new roots at a faster rate than without hormones. Two stem cuttings of equal length from a geranium plant were used:

• One cutting was dipped in rooting hormone and planted in wet sand.

• The other cutting was planted in wet sand without hormone.

• Both were given water and sunlight for 4 weeks.

• After 4 weeks, both plants were removed and the lengths of the roots were measured and found to be the same.

Conclusion: The hypothesis was not supported by the data, so it may need to be revised and retested.

Variables in Experiments

Type of Variable	Description	Example
Independent Variable	The variable that is intentionally changed or manipulated.	Use of rooting hormone
Dependent Variable	The variable that is measured or observed in response to changes in the independent variable.	Length of roots after 4 weeks
Controlled Variables	All other factors kept constant to ensure a fair test.	Amount of water, sunlight, type of sand

Evaluating Scientific Sources

Reliable scientific information should be obtained from reputable sources. The internet contains both accurate and inaccurate information, so it is important to evaluate the quality of sources.

• Check the credentials of the author or organization.

• Determine the purpose and date of publication.

• Prefer peer-reviewed sources and established organizations (e.g., National Geographic, Smithsonian, Scientific American, World Health Organization (WHO)).

Summary Table: Steps in the Scientific Method

Step	Description
1. Observe and Generalize	Collect data and look for patterns.
2. Formulate a Hypothesis	Propose a tentative explanation.
3. Make a Testable Prediction	Develop predictions that can be tested.
4. Experiment or Observe	Test predictions through experiments or further observation.
5. Modify Hypothesis and Retest	Revise hypothesis based on results and repeat as needed.

Key Equations and Logical Forms

• Deductive reasoning logical form: $\text{If } A = B \text{ and } B = C, \text{ then } A = C$

Additional info: The notes have been expanded to include definitions, examples, and structured tables for clarity and completeness.