What is Science? Plant Biology 006, Summer 2012

Science is a way of knowing Science is a way of knowing. It is a formal process of asking questions about the world and seeking explanations.

The key element of the scientific method is hypothetico-deductive reasoning. So what is that?

Hypothetico refers to hypothesis Hypothetico refers to hypothesis. A hypothesis is a provisional explanation of some phenomenon.

Deductive refers to the use of deductive reasoning to test the hypothesis. Deduction is reasoning from the general premise to the specific observation. It differs from induction, which involves moving from a set of specific facts to a general conclusion.

Example: Hypothesis: All dogs have fleas. Inductive approach is based on accumulating evidence in support of the hypothesis. Examine all the dogs you can find. If you examine enough and they all have fleas, you can claim that the evidence supports your hypothesis. However, this approach is vulnerable: even if you examine ten thousand dogs and they all have fleas, who’s to say that the ten-thousand-and-first won’t be flea-free?

Example: Hypothesis: All dogs have fleas. Deductive approach is based on falsifying the hypo- thesis. If, in the course of your canine examination, you find even one single dog without fleas, the hypothesis has been falsified. It is then revised or discarded in favor of an alternative hypothesis.

The hypothetico-deductive method proceeds by proposing a testable hypothesis and then trying to falsify it.

Figure 1.19 Idealized version of the scientific method

Figure 1.20 Applying hypothetico-deductive reasoning to a campground problem

Jan Baptista van Helmont ca. 1577-1644 .

Figure 1.19 Idealized version of the scientific method Trees grow larger with passing time. Why do trees grow larger with passing time? Trees grow larger by absorbing material from the soil. If a tree is grown in a pot of soil, the weight of the soil should decrease as the weight of the tree increases.

What happened? At the end of five years, the willow tree had increased in weight by 74.4 kilograms. The soil had decreased in weight by only 57 grams!

Figure 1.19 Idealized version of the scientific method Trees grow larger with passing time. Why do trees grow larger with passing time? Trees grow larger by absorbing material from the soil. If a tree is grown in a pot of soil, the weight of the soil should decrease as the weight of the tree increases. Result: the soil did not decrease in weight.

Conclusion: The hypothesis had been falsified: it was demonstrated that plants do not increase in size by absorbing material from the soil.

Q. Which of the following best represents an application of the Scientific Method? A student memorizes the Periodic Table of the Elements A homeowner checks his fuel tank to see if that’s why his furnace won’t come on An anthropologists finds a fossil hominid older than any yet known Geneticists completely sequence the human genome