Methods of Biology The series of steps used by scientists to gather information and answer questions is called the Scientific Method. If you had a question or a problem to solve, what steps would you go through to resolve it?

7 Steps of the Scientific Method Number 1 - State the Problem Take note of something no one has seen before or has yet to explain

7 Steps of the Scientific Method Number 2 - Gather Information Information gathered should be: Credible - trustworthy Accurate - correct – based on supported data Relevant - applicable, related to the topic of the investigation These sources could be Previous scientific investigations Science journals Textbooks Other credible sources, such as scientifically reliable internet sites.

Observation vs. Inference Observation - Gathering information using your senses Inference – making a judgment based upon an observation and past experience Fact or Fiction?

Make at least 3 observations about this picture. Make at least 3 inferences about this picture.

Make three observations and inferences with this new information Does the new information change your responses?

What does this final picture do to your previous inferences?

What does this picture do to your previous inferences?

7 Steps of the Scientific Method Number 3 - Form a Hypothesis Create a testable explanation for the situation that you observed

7 Steps of the Scientific Method Number 4 - Test the Hypothesis - Experiment Design an experiment An organized procedure for collecting information under controlled conditions The experiment will have two groups Control – all conditions are kept the same Experimental – conditions match that of the control except for the one factor being tested

7 Steps of the Scientific Method Testing… An important part in the experiment design is the sample size – the number of test subjects A large sample size increases the reliability of results A large sample size decreases the effect of errors on the outcome

7 Steps of the Scientific Method Testing… The condition that is changed in the experiment is the independent variable – it will be the only thing that can affect the outcome The outcome observed is the dependent variable – it depends upon the changes made to the independent variable Note: Some experiments cannot be controlled so other observation methods have to be used Example: wildlife study

Independent vs. Dependent Variables Mark the dependent and independent variable in each situation Suzy wanted to test how changing her diet affected her weight. The track team members that ran extra laps at practice ran better times at the next meet. Jack planted half of his roses in the shade and the other half in the direct sunlight and measured the differences in plant height and bloom production.

7 Steps of the Scientific Method Number 5 - Record and Analyze Data Record Data Data – information obtained from experiments Observations Results Data should be precise and accurate Precision – the degree to which measurements made in the same way agree with each other If you and I measure it, do we get the same thing? Accuracy – the degree to which the value measured agrees with the true or accepted value Even if we both got the same thing, did we measure it correctly? Data must then be analyzed or interpreted Graphs Tables Charts

7 Steps of the Scientific Method Number 6 - State a Conclusion Did the data support the hypothesis? If yes… Verify results Can the experiment be repeated? Do other scientists support the findings? If no… Repeat the experiment Revise the experiment Develop a new hypothesis Always Report Results!

7 Steps of the Scientific Method Number 7 - Repeat No matter what happened! Fact – Observable phenomenon that can be confirmed by scientists many times Form a Theory – a hypothesis tested over a long period of time, supported by separate experiments

Fact vs. Theory Which is Fact…Which is Theory? Dinosaurs were cold blooded. The caterpillar is 3.5 cm long.

Identifying Study Components A student noticed that when a dog is cut, the dog periodically licks its wounds. Usually after a few days, the wound begins to heal without ever showing signs of infection. The following steps outline the student's line of reasoning: I wonder why the dog's wound doesn't become infected. The dog's saliva must prevent the growth of infection-causing bacteria. I'll obtain a bacterial culture and grow the same kind of bacteria in two identical culture dishes. Once the bacteria start growing, I'll add dog saliva to only one of the dishes and leave the other alone. I'll cover both dishes. Then I'll observe what happens each day for a week. Even after adding the dog saliva to one of the dishes, the bacteria continued to grow in both dishes over the course of the week. However, the bacteria in the treated dish grew more slowly than the bacteria in the untreated dish. I think I'll try something else. I'll start with two identical culture dishes, as before, and use the same kind of bacteria in each dish, but this time I'll treat one dish with dog saliva before I add the bacteria. I'll observe what happens each day for a week. What was the student’s hypothesis? Which step described the experimental set up? Identify the control What is the independent variable? What is the dependent variable? What data did the student collect? What is a possible conclusion from this experiment? Is that conclusion a fact or an inference?

Identifying Study Components A student noticed that when a dog is cut, the dog periodically licks its wounds. Usually after a few days, the wound begins to heal without ever showing signs of infection. The following steps outline the student's line of reasoning: I wonder why the dog's wound doesn't become infected. The dog's saliva must prevent the growth of infection-causing bacteria. I'll obtain a bacterial culture and grow the same kind of bacteria in two identical culture dishes. Once the bacteria start growing, I'll add dog saliva to only one of the dishes and leave the other alone. I'll cover both dishes. Then I'll observe what happens each day for a week. Even after adding the dog saliva to one of the dishes, the bacteria continued to grow in both dishes over the course of the week. However, the bacteria in the treated dish grew more slowly than the bacteria in the untreated dish. I think I'll try something else. I'll start with two identical culture dishes, as before, and use the same kind of bacteria in each dish, but this time I'll treat one dish with dog saliva before I add the bacteria. I'll observe what happens each day for a week. What was the student’s hypothesis? Which step described the experimental set up? Identify the control What is the independent variable? What is the dependent variable? What data did the student collect? What is a possible conclusion from this experiment? Is that conclusion a fact or an inference?