The Scientific Process: Observation, Hypothesis, and Experiment in Science, Study notes of Ecology and Environment

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SCIENTIFIC PROCESS

Scientific process

Observation (I notice) Question (I wonder) Propose hypothesis (I explain) Support hypothesis Compare predicted results with actual results Design & conduct experiment Do NOT support hypothesis Partially support hypothesis

Science in Everyday Problem-Solving

Generating hypotheses

¨ Deduction ¤ From general to specific ¤ All swans are white, therefore 25 randomly selected swans will be white ¨ Induction ¤ From specific to general ¤ Twenty-five randomly collected swans were white, therefore all swans are white

Why do giraffes have long necks?

¨ Biologists test ideas about the way the natural world works by testing the predictions made by alternative hypotheses using carefully designed experiments. ¨ Simmons and Scheepers tested the food competition hypothesis that giraffes evolved long necks by natural selection because those with long necks reach food unavailable to others mammals.

Food competition hypothesis

¨ Predictions: ¤ Neck length is variable among giraffes ¤ Neck length in giraffes is heritable ¤ Giraffes feed high in trees

The sexual competition hypothesis

¨ An alternative hypothesis is that giraffes evolved long necks because longer-necked males win more fights than shorter-necked giraffes, and can then father more offspring. ¨ Data support this hypothesis.

Benefits of the scientific process

¨ Change is allowed and expected ¨ Based on observations or experiments ¨ Ideas are falsifiable ¨ Process is self-correcting ¤ Motivation to disprove the current paradigm

Critical thinking

¨ Science requires critical thinking skills ¤ You must practice You are interested in determining whether temperature affects the growth rate in salmon Hypothesis : Warmer temperatures increase the growth rate of salmon Experiment : You collect embryos from one female salmon and rear 100 in an incubator at 25˚C and another 100 in an incubator at 18˚C. The fish are fed the same diet and weighed after a year. Results : Fish reared at 25˚C weight more than fish reared at 18˚C (assume the statistics were significant and correct). Any weaknesses with the experimental design?

Correlation vs. causation

Cell theory

The cell theory

¨ The theory is quite simple but extremely important. ¨ It states the following: ¤ That all organisms are made of cells ¤ That all cells come from other cells

Development of microscopes

¨ Antonie van Leeuwenhoek (Dutch, 1600s) ¤ Was not a trained scientist ¤ Developed most powerful microscope of the time ¤ Made many contributions to biology n Described the circulatory system in vertebrates n Described several major animal groups (e.g. rotifers) n Observed sperm cells n Believed life came from males--and females just provided nutrition in the form of the egg and protection.

Discovery of cells