Scientific Method Science is ultimately based on observation

Scientific Method: Science is ultimately based on observation (perceiving objects or events using one of the five senses) Observations often lead to questions ---> which lead to experiments to answer the questions. The common steps that biologists and other scientists use to gather information and answer questions

Scientific Method usually begins with scientists identifying a problem to solve by observing the world around them 2 nd- formulating a hypothesis: an explanation for a question or a problem that can be formally tested • A hypothesis is not a random guess. • A hypothesis can never be proven only shown to be valid; however it can be proven false.

Hypothesis Examples Good 1. Plants will grow taller when given Miracle Grow. 2. Girls will score higher on math tests than boys. 3. Hermit crabs choose colorful shells over drab shells. Bad 1. Plants will grow better when given Miracle Grow. 2. Girls are smarter than boys. 3. Hermit crabs like colorful shells.

Scientific Method 3 rd- design a controlled experiment to test the hypothesis What is a controlled experiment? • In a controlled experiment, only one condition is changed at a time. • All variables are kept constant except the one you are testing Setting up a test in duplicate- involves two groups: the control group and the experimental group

What is a controlled experiment? The control is the group in which all conditions are kept the same. The control is a “reference point” for comparison q The experimental group is the test group, in which all conditions are kept the same except for the single condition being tested.

Designing an experiment • In a controlled experiment, only one condition is changed at a time. The condition in an experiment that is changed is the independent variable ~controlled by the experimenter All factors kept the same are called the controlled factors or constants.

Designing an experiment While changing the independent variable, the scientist observes or measures a secondition that results from the change This condition is the dependent variable, because any changes in it depend on changes made to the independent variable

Designing an experiment Formulate a PROCEDURE Replicate Sample size (large enough) Collect data – A scientist carefully collects and organizes data from the experiment. Data should always be presented in a neat fashion, usually tables or graphs.

Designing an experiment Conclusion: Based on the data, a scientist then determines whether the hypothesis was supported or refuted. Be careful here, scientists usually don't use the word "prove" because there are no absolutes in science. In science, every conclusion must assume that the conclusion is only "true to the best of our knowledge". This is an important distinction between science and other subjects. Science is subject to change when new evidence is found. And while experimentation and observations can provide strong evidence for a conclusion, it is not absolute proof.

• Controlled experiments are most often used in laboratory settings. • However, not all investigations are controlled. • An investigation such as this, which has no control, is the type of biological investigation most often used in field work.

Theory and Law Theory- sets of hypotheses that have always been supported by experimentation. Explanations that apply to a broad range of phenomena that occur in nature. Scientific Law- Statements about events that always occur in nature. A law does not explain why the event occurs, only that it occurs. Theories are used to explain laws.