Science: How to Do it Right A Research in Ecology Primer

Scientific Reasoning: Seeing Patterns

Radiation: Does it Harm Us? In the 1920s, Hermann Muller discovered that x-rays caused mutations in fruit flies.Hermann Muller

Radiation: Does it Harm Us?. A mutation is a change in an organism’s DNA, and it sometimes has physical consequences. A mutagen is anything that increases the occurrence of mutations.

Radiation: Does it Harm Us? Muller also discovered that x- rays can change the DNA of humans, causing defects. Other researchers noted that x- rays, gamma rays and other ionizing radiation caused mutations in various species. Since then it has been shown with many experiments that ionizing radiation is a mutagen.

Inductive Reasoning

Hypothesis A scientific hypothesis is a tentative explanation-- based on previous knowledge--for an observation. A scientific hypothesis is a tentative explanation-- based on previous knowledge--for an observation. It’s an “educated guess” that must be tested experimentally. It’s an “educated guess” that must be tested experimentally. It is the starting point of scientific inquiry. It is the starting point of scientific inquiry.

Theory A scientific theory is a well- substantiated explanation of some aspect of the natural world. A scientific theory is a well- substantiated explanation of some aspect of the natural world. It can incorporate facts, laws, inferences, and tested hypotheses. It can incorporate facts, laws, inferences, and tested hypotheses. A theory that has been rigorously tested and confirmed can be used to explain and predict natural phenomena. A theory that has been rigorously tested and confirmed can be used to explain and predict natural phenomena. In science, a “theory” is not a vague idea about an observation. In science, a “theory” is not a vague idea about an observation.

Law A scientific law generalizes a body of observations. A scientific law generalizes a body of observations. At the time it is made, no exceptions have been found to the law. At the time it is made, no exceptions have been found to the law. Scientific laws explain, but they do not describe or tell us why things happen. Scientific laws explain, but they do not describe or tell us why things happen. Example: Law of Gravity Example: Law of Gravity The Law predicts what will happen to a dropped object, but doesn’t’ explain why it happens. The Law predicts what will happen to a dropped object, but doesn’t’ explain why it happens.

Scientists are Skeptics! skep·tic - ˈ skeptik (noun) skep·tic - ˈ skeptik (noun) 1.A person inclined to question or doubt accepted opinions. Critical thinking means questioning things and insisting on EVIDENCE. Critical thinking means questioning things and insisting on EVIDENCE.

Inductive Reasoning

Once you have a theory… …it can be used to predict natural phenomena.

Deductive Reasoning

A Cautionary Tale: A theory alone is not enough to explain every observation. A theory alone is not enough to explain every observation. Careful confirmation must be done, and a good scientist never assumes anything Careful confirmation must be done, and a good scientist never assumes anything Because when you ASSUME, you can make an ASS out of U and ME. Because when you ASSUME, you can make an ASS out of U and ME.

August 6, 1945 The United States dropped atomic bombs on Hiroshima and Nagasaki, Japan Hiroshima was burned to ashes. Survivors suffered a living hell.

The Aftermath: Radiation Injuries Epilation Epilation Hemorrhage Hemorrhage Cataracts Cataracts Leukemias and other Cancers Leukemias and other Cancers

Deductive Reasoning

Experimental Design In 1948, the Atomic Bomb Casualty Commission (ABCC) began a six year study to monitor birth defects in Hiroshima and Nagasaki. In 1948, the Atomic Bomb Casualty Commission (ABCC) began a six year study to monitor birth defects in Hiroshima and Nagasaki. Atomic Bomb Casualty Commission Atomic Bomb Casualty Commission A total of 76,626 newborns were examined by ABCC physicians. A total of 76,626 newborns were examined by ABCC physicians. At the start of the study, women who were 20 weeks pregnant or more were made exempt from food rationing, but had to register for this privilege. At the start of the study, women who were 20 weeks pregnant or more were made exempt from food rationing, but had to register for this privilege. More than 90% of all pregnancies were thus registered, and their outcomes recorded. More than 90% of all pregnancies were thus registered, and their outcomes recorded.

Experimental Results You’ll sometimes see horrific pictures of malformed babies born after Hiroshima and Nagasaki. You’ll sometimes see horrific pictures of malformed babies born after Hiroshima and Nagasaki. But were these abnormal babies caused by the radiation? But were these abnormal babies caused by the radiation? Fewer than 1% of the babies born during this period showed signs of birth defects. Fewer than 1% of the babies born during this period showed signs of birth defects. Statistical testing revealed that this rate of birth defects was not significantly different from that occurring in areas without radiation contamination. Statistical testing revealed that this rate of birth defects was not significantly different from that occurring in areas without radiation contamination.

Let’s watch a movie.

A Leap of Logic? THEORY: “Ionizing radiation promotes birth defects.” OBSERVATION: “This rabbit, which was born near an area in Japan contaminated by radiation, has a birth defect.” CONCLUSION: “This rabbit’s birth defect was caused by ionizing radiation.” Did we skip a step or two?

Only the Facts. Multiple hypotheses make good science! What are some other possible hypotheses about the reason the bunny has no ears?

The Strong Hypothesis A scientific hypothesis cannot be proven correct. A scientific hypothesis cannot be proven correct. Piling up evidence to support a hypothesis does not address the fact that there may be a contradiction lying in wait! Piling up evidence to support a hypothesis does not address the fact that there may be a contradiction lying in wait!

The Strong Hypothesis

The most powerful hypothesis is one that can withstand attempts to FALSIFY it The most powerful hypothesis is one that can withstand attempts to FALSIFY it (i.e., prove it wrong) (i.e., prove it wrong)

The Scientific Method OBSERVATION OBSERVATION HYPOTHESIS (as many as are logical!) HYPOTHESIS (as many as are logical!) EXPERIMENTAL DESIGN EXPERIMENTAL DESIGN PREDICTION PREDICTION DATA COLLECTION DATA COLLECTION DATA ANALYSIS DATA ANALYSIS CONCLUSION CONCLUSION

The Scientific Method OBSERVATION: OBSERVATION: A natural phenomenon poses a problem or question.

The Scientific Method HYPOTHESIS - The investigator poses the question in such a way that it can be tested by rigorously designed experiments or field observations. HYPOTHESIS - The investigator poses the question in such a way that it can be tested by rigorously designed experiments or field observations. Null hypothesis - Stated in terms of "no difference between observed results and expected results" of an experiment. Abbreviated H o. Null hypothesis - Stated in terms of "no difference between observed results and expected results" of an experiment. Abbreviated H o. Alternative hypothesis - The opposite of the null, and actually the statement of interest. Abbreviated H a. Alternative hypothesis - The opposite of the null, and actually the statement of interest. Abbreviated H a.

The Scientific Method EXPERIMENTAL DESIGN - carefully designed to yield data to either support or refute the hypothesis. EXPERIMENTAL DESIGN - carefully designed to yield data to either support or refute the hypothesis. Large enough sample size Large enough sample size Exclusion of confounding factors Exclusion of confounding factors Statistical tests Statistical tests

The Scientific Method PREDICTION - A statement about the expected results of an experiment. PREDICTION - A statement about the expected results of an experiment. DATA COLLECTION - The experiments are run, and data are collected. DATA COLLECTION - The experiments are run, and data are collected. DATA ANALYSIS - The data are subjected to rigorous analysis via quantification and/or statistical tests to determine whether any deviation from the expected result is truly meaningful, or merely due to chance. DATA ANALYSIS - The data are subjected to rigorous analysis via quantification and/or statistical tests to determine whether any deviation from the expected result is truly meaningful, or merely due to chance. CONCLUSION - The investigator accepts or rejects the null hypothesis. CONCLUSION - The investigator accepts or rejects the null hypothesis.

The Reward Good science is about finding truth and getting the facts. Good science is about finding truth and getting the facts. Knowing the cause, might we some day find a cure? Knowing the cause, might we some day find a cure?