The Science of Biology Chapter 1

What’s the Point…??? The Real Goal of science is to investigate and understand the natural world, to explain events in the natural world, and to use those explanations to make useful predictions.

How to think like a Scientist… We must Observe Data can be Quantitative or Qualitative

What is Quantitative??? Direct measurable data Numbers Descriptions can also be quantitative

Time to Explain our observations… Hypothesis – A proposed scientific explanation for a set of observations. Make sure to note that either of these explanations are fine as long as they are based on the data. If something comes along that disproves one hypothesis, then we must reject it. Until then, all data based hypothesis are valid.

An on going process…. Science. Science itself is always changing… We learn more and figure things out every day. When we get new evidence, we must change our ideas, hypothesis and theories that no longer fit the data. Everything in science is driven by data!

How Scientists Work Observations and questions Gather data Form a hypothesis Set up a Controlled experiment (if possible).

Example of how scientists work Observation and question—maggots appear on meat. How do they get there? Or where do they come from? Spontaneous generation Enter Scientist—Francesco Redi (1668) Spontaneous generation was the accepted theory of the time. Redi observed that the maggots appeared after flies landed there. Did the flies have something to do with the maggots?

Experiment—if possible test only one variable at a time. Observation/question—maggots appeared after flies had landed there. Did the flies have something to do with the maggots? Experiment—if possible test only one variable at a time. (a variable is a condition or thing that scientists believe can effect what is happening) Actually Redi even went as far as to say that the flies left behind eggs that were too small to see and that the maggots came from the eggs. Testing more than one variable makes it hard to know which variable made the difference.

Experiment Redi set up two jars One without a cover One with a cover (it let air through but nothing else)

Understanding Check! Redi had two jars, one covered and one uncovered. Which of the following best explains why he did that? 1—he wanted to keep air out of one of the jars 2—he did not want one of the jars to spoil 3—the cover kept out the flies 4—the cover kept out the maggots Answer is green Red- the cover didn’t keep out air Blue—he actually did want the jars to spoil—it was part of the experiment Green—correct Yellow—the cover didn’t keep out the maggots, it kept out the flies

What happened? The jar that was not covered had maggots in a few days. The jar that was covered had no maggots.

Understanding Check! What did Redi’s experiment show? 1—The maggots are baby flies 2—If you kept the flies out, no maggots appeared 3—the cover kept out flies 4—the maggots came from flies The answer is blue. Red and yellow would come later when people examined the eggs left by the flies. Green really wasn’t part of what the experiment was looking at, but blue is what the experiment found.

What’s the key to a successful experiment? Variables Manipulated variable (aka. Independent variable) is the ONE that is deliberately changed. Responding variable (aka. Dependent variable) is the one that changes in response to the manipulated variable.

Understanding Check! What was Redi’s manipulated or independent variable? 1—the meat in the jars 2—the jars 3—the cover on one jar 4—the maggots Answer is green. maggots were not controlled, the meat was in both jars and for blue, the actual jars themselves were the same.

Understanding Check! Which variable was the responding (dependent ) variable? 1—the flies 2—the jars 3—the cover 4—the maggots Ask them to go through the steps before bringing up the question The answer is yellow. The flies were allowed in as part of the experiment, the jars were the same, the cover was the independent variable, but the maggots depended on whether or not there were flies.

One last step! Repetition Other scientists need to use similar methods and get similar results If they can’t then your experiment was a fluke, not good data Redi’s experiment was repeated at least 3 times in various forms John Needham—mid 1700’s Lazzaro Spallanzani Louis Pasteur in 1864 Needham heated the liquid then tried to prove spontaneous generation when microorganisms reappeared in a sealed glass jar Spallanzani thought that Needham hadn’t heated the liquid enough so he did the same experiment but boiled the liquid and showed that no life appeared in the sealed bottle Some people said that life couldn’t appear with out air so Pasteur repeated Spallanzani’s experiment but gave the bottles long necks that kept out dust but not air. No life spontaneously appeared.

How Scientists Work Summary Question and Observation Possible explanation (hypothesis) based on data Experiment (or research) that is designed to test the hypothesis Data collection/Results Conclusions—figuring out what it means. Repetition—make sure it is good data

Theories Some words in science mean something different than how they are used in other places. Example: Cool Lunchroom use—meaning = good Science use—meaning = lower temperature In Science, the word theory applies to a well tested explanation that unifies a broad range of observations. There are many theories in science

Theories…. Ongoing investigation… Science is characterized by both continuity and change. When we get new data—if our explanation (hypothesis or theory) no longer fits, then it must be changed. Example: Address theory