Scientific Method

Overview of the Scientific Method

The scientific method is a systematic approach used by scientists to investigate natural phenomena, answer questions, and solve problems. It involves a series of steps that ensure experiments are conducted objectively and results are reliable.

• Ask a Question: Identify a specific, measurable question based on observation (e.g., "Why does bariatric surgery reverse diabetes?").

• Do Background Research: Gather existing information to understand the context of the question.

• Construct a Hypothesis: Formulate a testable and falsifiable statement (e.g., "Surgery alters bile flow which is responsible for reversing diabetes").

• Test Your Hypothesis by Doing an Experiment: Design and conduct experiments to test the hypothesis (e.g., alter bile flow without surgery to observe effects).

• Analyze Your Data and Draw a Conclusion: Evaluate experimental results to determine if they support or refute the hypothesis.

• Report Your Results: Communicate findings, including whether the hypothesis was correct.

Formulating Scientific Questions

Testable and Measurable Questions

Scientific questions must be testable and measurable. This means they can be answered through observation or experimentation and produce quantifiable results.

• Are domestic dogs as smart as wolves?

• Does drinking milk from arthritic goats reduce HIV in infected individuals?

• Do honey bees prefer processed sugar over flower nectar?

• Should governments prohibit distribution of GM food during famine?

• How effective are marigold and rosemary as insect repellants?

Key Point: Questions should focus on variables that can be measured or observed.

Hypothesis

Characteristics of a Scientific Hypothesis

A hypothesis is a proposed explanation for a phenomenon. It must be testable and falsifiable, meaning it can be supported or refuted by experimental evidence.

• A hypothesis is not proved true, only supported or falsified by data.

• Examples of hypotheses:

  • Milk sours due to bacterial growth.

  • A diet in pregnant women may increase chances of ADHD in children.

  • Living on a farm protects children from developing hay fever.

  • The Y chromosome in modern humans is the same as the Y chromosome in Neanderthals.

  • Genetically modified foods have caused an increase in gluten intolerance.

  • Proteins from pythons can be used to build heart muscle.

Prediction

Making Predictions from Hypotheses

Once a hypothesis is constructed, a prediction can be made. Predictions are specific statements about what will happen in an experiment if the hypothesis is correct, often written as "if/then" statements.

• If the hypothesis is that bile diversion reverses diabetes, then cannulating the bile duct and diverting bile flow to the ileum will reverse diabetes.

• Predictions are tested experimentally.

• If results match the prediction, the hypothesis is supported; if not, it is falsified.

Variables in Experiments

Types of Variables

Experiments involve different types of variables that must be clearly defined and controlled.

• Independent Variable: The variable that the scientist changes or manipulates (e.g., type of plant, bile flow).

• Dependent Variable: The variable that is measured in response to changes in the independent variable (e.g., number of eggs laid, blood glucose level).

• Controlled Variables: Other variables that might influence the outcome; these are kept constant to ensure a fair test (e.g., time of day, temperature, humidity).

Hypothesis Testing: Example with Monarch Butterflies

Experimental Design

Scientific experiments often follow a logical sequence to test hypotheses. The monarch butterfly experiment is a classic example.

• Observation: Monarch butterflies are infected by protozoan parasites. Monarchs lay eggs on milkweed plants, which larvae eat after hatching. Some types of milkweed suppress parasite growth.

• Hypothesis: Female monarchs selectively lay eggs on milkweed plants that suppress parasite growth.

• Prediction: Infected females will lay more eggs on growth-suppressing plants than on non-growth-suppressing plants.

Procedure

• Monarch larvae were infected with parasites.

• Infected females were housed separately from uninfected females.

• Both infected and uninfected females were allowed to mate with males.

• 10 infected and 10 uninfected females were placed in a chamber with two milkweed plants (one suppressing parasite growth, one not).

• After 24 hours, butterflies were removed and eggs laid on each plant were counted.

Variables in the Monarch Experiment

• Dependent variable: Number of eggs laid on each plant.

• Independent variable: Butterfly infection status (infected or uninfected).

• Controlled variables: Time of day, temperature, time after mating, length of experiment, humidity, source of larvae.

Cardiovascular Fitness

Definition and Importance

Cardiovascular fitness refers to the ability of the heart and blood vessels to supply oxygen-rich blood to working muscles during sustained physical activity. It is a key measure of overall physical fitness and is influenced by various factors such as genetics, age, and lifestyle.

Harvard Step Test

Procedure and Calculation

The Harvard Step Test is a simple method to assess cardiovascular fitness by measuring recovery rate after exercise.

• Measure pulse rate (resting pulse rate).

• Step up and down on a block 30 times per minute for 4 minutes (using a metronome set to 120 beats per minute can help maintain the correct rate).

• After exercise, measure pulse rate at 1, 2, and 3 minutes.

• Calculate the fitness index using the following equation:

Where = bpm at 1 min after exercise; = bpm at 2 min; = bpm at 3 min.

Scientific Presentation and Reporting

Structure of Scientific Reports

Results of scientific experiments are reported in lab reports and scientific papers, which follow a standard structure:

• Introduction: Background to the experiment, rationale, and hypothesis.

• Methods: Description of how the experiment was carried out.

• Results: Presentation of data, including text, tables, and figures. Each table and figure should have a title and number.

• Discussion: Interpretation of results, evaluation of hypothesis, and comparison with previous research.

• References: Citations for all sources used.

Figures and Tables

• Figures should have descriptive titles and numbers.

• The independent variable is plotted on the X-axis; the dependent variable on the Y-axis.

• Graphs should be clearly labeled and include legends to identify groups.

• Line and bar graphs are commonly used, depending on the data type.

*Additional info: Academic context and definitions have been expanded for clarity and completeness. The Harvard Step Test equation is provided in LaTeX format as required.*