Welcome to Class! 8-24 and 8-25 Complete the following:  Take out Syllabus and lab safety contract signature  Take out Lab safety quiz online  Take out Journal with Cornell notes for Homework grade (be sure to Enter new entry as well as label the page you took notes on for today “What is Science?”)  Glue in vocabulary #1 next available page

Agenda  Revisit materials learned from last week  Lecture notes on What is Science?  Kahoot interactive Quiz  Create Flow Map of Scientific Method  Concept map compare and contrast Hypothesis vs. Theory  Homefun: Assigned Vocabularies

What Is Science?

The Nature of Science Science  Uses evidence to construct testable explanations and predictions of natural phenomena  Generates knowledge

Beginnings of Biology Many of the original understandings of life came from philosophers who did not actually conduct experiments, rather using logic and reason.

Aristotle, an influential Greek philosopher, proposed that life could arise from non-living matter. “So with animals, some spring from parent animals according to their kind, whilst others grow spontaneously and not from kindred stock; and of these instances of spontaneous generation some come from putrefying earth or vegetable matter, as is the case with a number of insects, while others are spontaneously generated in the inside of animals out of the secretions of their several organs.“ —Aristotle, History of Animals, Book V, Part 1

Scientific Method The idea of spontaneous generation was eventually discarded through the use of the scientific method. Scientific methodology involves: –observing and asking questions, –forming hypotheses –conducting controlled experiments, –collecting and analyzing data –drawing conclusions.

Scientific investigations begin with observation, the act of noticing and describing events or processes in a careful, orderly way. A hypothesis is an explanation for an observation based on prior knowledge. –Aristotle’s idea of spontaneous generation began with the observation that maggots would arise from meat or dead flesh, fleas from dust, tapeworms from other organisms, etc.

During Aristotle’s time, all scientific ideas were based on thought and logic, not experimentation. Experiments test a hypothesis under controlled conditions. –Whenever possible, a hypothesis should be tested by an experiment in which the independent variable is changed. –The variable that is changed or affected is called the dependent variable, and will be measured. –Any other variables should be held unchanged or constant.

All experiments involve the collection of data. –If this includes numerical measurements (time, distance, etc), the data is quantitative. –If this includes non- numerical descriptive observations, the data is qualitative.

An Italian physician named Francisco Redi proposed an experiment to test spontaneous generation. –A flask containing raw meat was left in the open. This was the control group, since no new variable was being introduced.

Two additional flasks were set up, one completely sealed, and the other covered with gauze to allow air flow. –These were the experimental groups that were being exposed to the independent variable. –The dependent variable, the appearance of maggots, was recorded.

Only the unsealed flask grew maggots. Redi’s conclusion was that his hypothesis was correct -- maggots did not spontaneously generate, but grew from tiny eggs laid by flies. –Conclusions always indicate whether the original hypothesis is supported or rejected.

Sources of Error Accounting for every single variable in a scientific study is nearly impossible. There are many factors that can cause error or otherwise cause an incorrect conclusion. Probability helps to predict the likeliness of an experimental result occurring simply due to random chance. –The effects of random chance are countered with having a large sample size in the experiment.

Another major problem with experiments is when scientists or patients influence the data to produce a specific result. –This is called bias.

Depending on the results of the experiment, the hypothesis may be rejected or modified. New experiments may be designed and conducted until some version of the hypothesis is supported.

Hypotheses should not be confused with theories, which are large, broad explanations composed of many hypotheses and experimental results. –A theory would not be rejected by a single experiment, but a hypothesis could be. –An example of a theory is the germ theory, which states that some diseases are the result of the presence and actions of microorganisms within the body.

Scientific Methodology: Observation Science is a general style of investigation, not a rigid step-by-step process.

Scientific Methodology: Asking Questions Why do marsh grasses grow to different heights in different places?

Scientific Methodology: Hypothesis Inference: a logical interpretation based on Hypothesis: a tentative scientific explanation that can be what scientists already know tested further

Scientific Methodology: Experiment Testing hypotheses often involves designing experiments that measure factors that can change, or variables.

Scientific Methodology: Collecting Data data are numbers. data are descriptive. Qualitative Quantitative

Scientific Methodology: Analyzing Data Data analysis in science often relies on the use of statistics.

Scientific Methodology: Review

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