The Methods of Biology Objectives n n Compare

The Methods of Biology

Objectives n n Compare different scientific methods Differentiate among hypothesis, theory, and principle Vocabulary n n n n Control Data Dependent Variable Experiment Hypothesis Independent Variable Scientific method Theory

n n The goal of science is to INVESTIGATE and understand nature, to explain events in nature, and to use those explanations to make useful HYPOTHESES. We investigate by making OBSERVATIONS using our 5 senses to collect DATA.

THE SCIENTIFIC METHOD: The scientific method is a series of steps that scientists use to answer questions 1. 2. 3. 4. 5. 6. 7. 8. 9. State the problem Gather information Make a hypothesis Design an experiment Collect data Analyze results Make a conclusion Form a theory Repeat the experiment

Step 1: State the Problem n n n Look at the world around you! What don’t you understand? What would you like to know more about?

Step 2: Gather Information n What do you already know from n n Observations? Reading? Previous investigations? What don’t you know and find out more about it?

Step 3: Make a Hypothesis n n n A hypothesis is a possible explanation based on observed characteristics of an object. IF…THEN… Example: If I study my vocabulary words, then I will do well on the quiz

Step 4: Design an Experiment n An experiment is an investigation that tests a hypothesis.

Experiments must include a: n n n Control group – group in which all conditions are kept the same Experimental group– test group - all conditions are kept the same except for the single condition being tested (variable)

Variables… n Independent Variable – n n Factors that are different between groups the researcher can “control” this x axis of graph Dependent Variable n n n Condition that results from the change The result or DATA collected y axis of graph

Step 5: Collect Data n n n Data is collected by making observations using your senses or by making measurements Data can support or disprove a hypothesis Organized in a table

Step 6: Analyze Results n Data is turned into graphs to interpret trends and make correlations

Step 7: Make a Conclusion n A statement describing what was learned from the experiment and if the data supported the hypothesis.

Step 8: Form a Theory n A theory is a hypothesis that is supported by a large body of scientific evidence

Step 9: Repeat the Experiment n For experiments to be considered valid, they are repeated several times to ensure that the same results would occur every time.

THEORIES: n n n A theory is a HYPOTHESIS that covers a broad range Example: the THEORY of Evolution Example: the Big Bang THEORY

How do you Improve an Experiment? 1. Reduce experimental BIAS 2. Redo the Experiment 3. Increase the sample size 4. Control other variables

Summary & Evaluation A scientist conducts an experiment to test the effect of light on plant growth. In each experiment, three plants of the same variety are each given 10 m. L of water. One plant is exposed to full sunlight for 8 hours, one is exposed to full sunlight for 4 hours, and one plant is kept in a dark room. Plant height is measured after two weeks. What is the independent variable in this experiment? A. soil volume B. amount of sunlight C. plant height D. amount of water The answer is B. The independent variable is the condition that is changed. In this case, the amount of sunlight is changed for each plant. Plant heights are measured results of the experiment, so plant height is the dependent variable.

Summary & Evaluation Which of the following is the group in an experiment in which all conditions are kept the same? A. standard B. independent variable C. experimental D. control The answer is D. Conditions are kept the same in the control group. The experimental group is the test group.