Section 1.2: The Methods of Biology

Why does rain bring out the worms?

Observing and Hypothesizing Curiosity is often what motivates biologists to try to answer simple questions about everyday observations The knowledge obtained when scientists answer questions provides better understanding of general principles or may lead to practical applications or new questions

The Methods Biologists Use

Scientific Methods The common steps that scientists use to gather information and answer questions Scientific methods usually begin with identifying a problem to solve

The Story of the Brown Tree Snake

Hypothesis An explanation for a question or a problem that can be formally tested A hypothesis is not a random guess! The scientist has some idea of what the answer might be through personal observations, extensive research, or previous investigations

Experiment tests a hypothesis by collecting information under controlled conditions

What is a controlled experiment? Some experiments involve two groups: the control group and the experimental group

Control The group in which all conditions are kept the same

Experimental Group test group in which all conditions are kept the same except for the single condition being tested

Does fertilizer help plants grow taller? Water + Fertilizer Water

Designing an experiment In a controlled experiment, only one condition is changed at a time

Does fertilizer help plants grow taller? Water + Fertilizer Water Controls Same volume of water Same temperature Same sun exposure

Independent variable The condition in an experiment being changed

Dependent variable The condition that results from a change in the independent variable

Does fertilizer help plants grow taller? (centimeters) Growth Fertilizer No Fertilizer

Now You Try…

Formulate a hypothesis based on this experiment. A number of rats are divided into two groups: One group is fed a normal diet, whereas the other group is fed the same diet but with one necessary mineral left out. The animals receiving the normal diet remained healthy; those in the other group grew weaker. Formulate a hypothesis based on this experiment.

A scientist conducted an experiment to determine the effect of environment on the color of fur of a Himalayan rabbit. The Himalayan rabbit typically has a white coat except for its colder nose, feet, tail, and ears, which are black. The scientist shaved an area of hair on the back of each rabbit, then placed an ice pack over the shaved area on one rabbit (A).

Using Tools To carry out investigations, scientists need tools that enable them to record information

Gathering Data To answer their questions about scientific problems, scientists seek information from other investigations

Data Info obtained from investigations or experimental results

Thinking about what happened After careful review of the results, the scientist must come up with a conclusion Was the hypothesis supported by the data? Was it not supported? Is more data needed? Does the experiment need to be repeated? After analyzing the data, most scientists have more questions than they had before the investigation

Reporting results Results and conclusions of investigations are reported in scientific journals

Verifying results When a hypothesis that is supported by many separate observations and investigations, usually over a long period of time, becomes a theory

Theory An explanation of a natural phenomenon that is supported by a large body of scientific evidence obtained from many different investigations A theory results from continual verification and refinement of a hypothesis In addition to theories, scientists also recognize certain facts of nature called laws or principles Ex.) gravity

Hypothesis vs. Theory An explanation for a question or a problem that can be formally tested An explanation of a natural phenomenon that is supported by a large body of scientific evidence obtained from many different investigations

Do Now Get your Questions of the Days out and place it on top of your desk so I can stamp it. In your notebook, please describe this class in anyway you’d like.

Do Now 200 carrot seeds each were used in an investigation to test for the influence of temperature on germination of seeds. Group A had 150 seeds and was kept at a temperature of 20 degrees Celcius and Group B had 50 seeds and was kept at 10 degrees Celcius. All other conditions were the same.