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

Science: Science: How to Do it RightHow to Do it RightA Research in Ecology PrimerA Research in Ecology Primer

Scientific Reasoning: Scientific Reasoning: Seeing Patterns Seeing Patterns

Radiation: Radiation: Does it Harm Does it Harm Us?Us?

In the 1920s, Hermann Muller discovered that x-rays caused mutations in fruit flies.


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.


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 ReasoningInductive Reasoning


HypothesisHypothesis

A A scientific hypothesisscientific hypothesis is a is a tentative tentative explanationexplanation--based on --based on previous knowledge--previous knowledge--for an observation. for an observation.

ItIt’’s an s an ““educated educated guessguess”” that must be that must be tested experimentally.tested experimentally.

It is the starting point It is the starting point of scientific inquiry.of scientific inquiry.

TheoryTheory

A A scientific theory scientific theory is a is a well-substantiated well-substantiated explanation explanation of some of some aspect of the natural aspect of the natural world.world.

It can incorporate facts, laws, It can incorporate facts, laws, inferences, and tested inferences, and tested hypotheses.hypotheses.

A theory that has been A theory that has been rigorously tested and rigorously tested and confirmed can be used to confirmed can be used to explain explain and and predict predict natural natural phenomena. phenomena.

In science, a In science, a ““theorytheory”” is is not not a a vague idea about an vague idea about an observation.observation.

LawLaw

A A scientific law scientific law generalizes a body of generalizes a body of observations. observations.

At the time it is made, At the time it is made, no no exceptionsexceptions have been have been found to the law. found to the law.

Scientific laws explain, but Scientific laws explain, but they do not describe or tell they do not describe or tell us why things happen.us why things happen.

Example: Law of GravityExample: Law of Gravity

The Law predicts The Law predicts what what will will happen to a dropped happen to a dropped object, but doesnobject, but doesn’’tt ’’ explain explain why why it happens.it happens.

Scientists are Scientists are Skeptics!Skeptics!

skep·ticskep·tic - ˈskeptik - ˈskeptik (noun)(noun)

1.1. A person inclined to A person inclined to question or doubt accepted question or doubt accepted opinions.opinions.

Critical thinking Critical thinking means means questioning things and questioning things and insisting on insisting on EVIDENCEEVIDENCE..


Once you have a Once you have a theory…theory…

……it can be used to predict it can be used to predict natural phenomena.natural phenomena.

Deductive ReasoningDeductive Reasoning

A Cautionary Tale:A Cautionary Tale:

A theory alone is not A theory alone is not enough to explain every enough to explain every observation.observation.

Careful confirmation must Careful confirmation must be done, and a good be done, and a good scientist never assumes scientist never assumes anythinganything

Because when you Because when you ASSUMEASSUME, , you can make an you can make an ASS ASS out of out of U U and and MEME..

August 6, 1945August 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: The Aftermath: Radiation InjuriesRadiation Injuries

EpilationEpilation

HemorrhageHemorrhage

CataractsCataracts

Leukemias and Leukemias and other Cancersother Cancers

Deductive ReasoningDeductive Reasoning

Experimental DesignExperimental Design

In 1948, the In 1948, the Atomic Bomb Casualty Atomic Bomb Casualty Commission (ABCC) Commission (ABCC) began a six year study to began a six year study to monitor birth defects in Hiroshima and Nagasaki.monitor birth defects in Hiroshima and Nagasaki.

A total of 76,626 newborns were examined by A total of 76,626 newborns were examined by ABCC physicians. ABCC physicians.

At the start of the study, women who were 20 At the start of the study, women who were 20 weeks pregnant or more were made exempt weeks pregnant or more were made exempt from food rationing, but had to from food rationing, but had to register register for this for this privilege.privilege.

More than 90% of all pregnancies were thus More than 90% of all pregnancies were thus registered, and their outcomes recorded.registered, and their outcomes recorded.

Experimental ResultsExperimental Results

YouYou’’ll sometimes see horrific pictures of malformed ll sometimes see horrific pictures of malformed babies born after Hiroshima and Nagasaki. babies born after Hiroshima and Nagasaki.

But were these abnormal babies caused by the But were these abnormal babies caused by the radiation?radiation?

Fewer than 1% of the babies born during this Fewer than 1% of the babies born during this period showed signs of birth defects.period showed signs of birth defects.

Statistical testing revealed that this rate of birth Statistical testing revealed that this rate of birth defects was defects was not significantly different not significantly different from that from that occurring in areas without radiation contamination.occurring in areas without radiation contamination.

LetLet’’s watch a movie.s watch a movie.

https://www.youtube.com/watch?v=Iw2R7y65nFg

A Leap of Logic?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.Only the Facts.

Multiple hypotheses make good science!

What are some other possible hypotheses about the reason the bunny has no ears?

The Strong HypothesisThe Strong Hypothesis

A scientific hypothesis cannot be A scientific hypothesis cannot be proven correct.proven correct.

Piling up evidence to support a Piling up evidence to support a hypothesis does not address the hypothesis does not address the fact that there may be a fact that there may be a contradiction lying in wait!contradiction lying in wait!





The most powerful The most powerful hypothesis is one that can hypothesis is one that can withstand attempts to withstand attempts to FALSIFY FALSIFY it it

(i.e., prove it wrong)(i.e., prove it wrong)

The Scientific MethodThe Scientific Method

OBSERVATIONOBSERVATION

HYPOTHESIS (as many as are logical!) HYPOTHESIS (as many as are logical!) EXPERIMENTAL DESIGNEXPERIMENTAL DESIGN PREDICTIONPREDICTION DATA COLLECTIONDATA COLLECTION DATA ANALYSISDATA ANALYSIS CONCLUSIONCONCLUSION


OBSERVATIONOBSERVATION::

A natural phenomenon poses a problem or A natural phenomenon poses a problem or question. question.


HYPOTHESIS HYPOTHESIS - The investigator poses the - The investigator poses the question in such a way that it can be tested by question in such a way that it can be tested by rigorously designed experiments or field rigorously designed experiments or field observations. observations.

Null hypothesisNull hypothesis - Stated in terms of "no - Stated in terms of "no difference between observed results and expected difference between observed results and expected results" of an experiment. Abbreviated results" of an experiment. Abbreviated HHoo. .

Alternative hypothesisAlternative hypothesis - The opposite of the - The opposite of the null, and actually the statement of interest. null, and actually the statement of interest. Abbreviated Abbreviated HHaa. .


EXPERIMENTAL DESIGNEXPERIMENTAL DESIGN- carefully designed - carefully designed to yield data to either support or refute the to yield data to either support or refute the hypothesis. hypothesis. Large enough Large enough sample sizesample size Exclusion of Exclusion of confounding factorsconfounding factors Statistical testsStatistical tests


PREDICTIONPREDICTION- A statement about the expected - A statement about the expected results of an experiment. results of an experiment.

DATA COLLECTIONDATA COLLECTION- The experiments are run, - The experiments are run, and data are collected.and data are collected.

DATA ANALYSISDATA ANALYSIS- The data are subjected to - The data are subjected to rigorous analysis via quantification and/or rigorous analysis via quantification and/or statistical tests to determine whether any statistical tests to determine whether any deviation from the expected result is truly deviation from the expected result is truly meaningful, or merely due to chance. meaningful, or merely due to chance.

CONCLUSIONCONCLUSION- The investigator accepts or - The investigator accepts or rejects the null hypothesis. rejects the null hypothesis.

The RewardThe Reward

Good science is Good science is about finding truth about finding truth and getting the and getting the facts. facts.

Knowing the cause, Knowing the cause, might we some day might we some day find a cure?find a cure?

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