The Science of Biology Biology 392

Observing the World If you are a thinker, you question things you observe and may not understand and you try to find an answer. There are many ways to find these answers. If you are a scientific thinker you find your answer using the scientific method. Example: Why is the sky blue?

1-1 What is science?  an organized way of using evidence to learn about the natural world  It also refers to the body of knowledge that scientists have accumulated over time.  It is not based on belief or faith, magic, or legend but on actual evidence. It is concerned with the natural world, not the supernatural world.

What is Biology? Biology is a specific field of science that studies life

Important Skills used When Doing Science: Observing- process of gathering information using your senses in a careful, orderly way Inferencing- making a logical interpretation based on prior knowledge or experience

Good Scientists...  are skeptics: They question existing ideas and new hypotheses.  are open-minded: They are always willing to consider new ideas when evidence demands it  rely on basic natural laws: They understand that the universe functions as a system of interacting processes.  repeat experiments: through an immense amount of research a certain hypothesis might become so well-supported that scientists consider it a theory (example: biogenesis).  keep up with new knowledge gained through research : They continually revise and re-evaluate their ideas. NOTHING IS “FACT”. * Many questions you have now or will have in the future involve science. You must understand science to make intelligent decisions about such issues.

How is Science Done?  Scientists use the scientific method. When scientists have a question about something in the world they use this method to find an answer:  State the Problem or Question  Research  State a hypothesis  Design an experiment with a control group, constants and variables  Analyze data/ results  Conclusion or Summary

1. State the Problem or Question What have I observed? What do I want to know?

2. Research Has anyone asked this before? Did they discover an answer? How did they go about looking for an answer? What other things do I need to understand to answer my question?

3. Form a Hypothesis Based on the research you have done, write a possible answer or solution – your best educated guess – to your question.

4. Design an Experiment  Control Group: Part of your experiment that is not varied in anyway. You can compare your test groups to this set standard group.  Independent variable- The change/difference you make in the experiment (the thing you are testing). Also called manipulated variable  Dependent variable - The differences that result from the experiment, the resulting effect. Also called responding variable.  Constants- Things in the experiment that do not change, kept exactly the same for each test group so they do not affect the results.

5. Data/Results  It is easier to understand the data if it is put into a table and/or graphed.  Make sure all data is clearly labeled. Charts and graph should always include units and titles.  When graphing the independent variable should be on the x axis and the dependent variable should be on the y axis.

6. Analysis What happened? What was expected? What was unexpected? What trends did you notice in the data?

7. Conclusion or Summary Indicate whether or not the data supports the hypothesis and explain why or why not. Suggest possible improvements to the experiment. Suggest further avenues of research or uses for the information discovered.

Learning Checkpoint  What is inferencing?  What are the steps of the scientific method?  In which step would you find charts and graphs?  What is the difference between an independent variable and a dependent variable?  What is the purpose of a control group?  What does it mean to have a controlled experiment?

1-2 An Example of Science at Work  Observed: sometimes organisms just “arose” from nonliving things: eg. maggots came from meat.  The Question: How do new living things come into being?  Hypothesis: In some cases, nonliving objects can spontaneously generate living organisms. 1 st Experiment- 1668, Francesco Redi:  Meat in covered and uncovered jars  proposed a new hypothesis: The maggots came from eggs left by flies on the meat that were too small to see.  Concluded: Maggots came from flies.

OBSERVATIONS: Flies land on meat that is left uncovered. Later, maggots appear on the meat. HYPOTHESIS: Flies produce maggots. PROCEDURE Controlled Variables: jars, type of meat, location, temperature, time Manipulated Variables: gauze covering that keeps flies away from meat Uncovered jarsCovered jars Several days pass Maggots appearNo maggots appear Responding Variable: whether maggots appear CONCLUSION: Maggots form only when flies come in contact with meat. Spontaneous generation of maggots did not occur. Redi’s Experiment

Science continues...New Ideas with new discoveries  New discovery!- tiny microorganisms (discovered by Anton van Leeuwenhoek) 2 nd Experiment- Mid 1700s, John Needham:  Repeats Redi’s experiment.  His hypothesis: Spontaneous generation can occur under the right conditions.  Result: microorganisms appear in sealed flask of boiled gravy.

Science Experiments are always repeated: 3 rd Experiment- Lazzaro Spallanzani:  T hinks Needham did not boil gravy long enough to kill existing microorganisms.  Results: When left exposed to air, microorganisms will appear in boiled gravy.  He concluded that microorganisms could not come from gravy but appeared instead from microorganisms existing in the air.

Spallanzani’s Tests Gravy is boiled.Flask is open. Gravy is teeming with microorganisms. Gravy is boiled. Flask is sealed. Gravy is free of microorganisms. Needham tried first but didn’t bring gravy to hot enough temperature.

New Question: Is air the “life force”? 4 th Experiment- 1864, Louis Pasteur:  Set out to dismiss the notion that the “life force”, air was needed to generate life.  Used curved neck on flask so air could get in but organisms would not.  Concluded that all living things can only come from living things.  This has been tested over and over and is now considered a theory called biogenesis.

Learning Checkpoint  Did all 4 scientists use good scientific thinking and a controlled experiment?  What is spontaneous generation?  What was the point of the “swan neck” Pasteur added to his flask?  What is biogenesis?