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Chapter 1: Section 2 How Scientists Work
Notes Scientific Method Chapter 1: Section 2 How Scientists Work
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How Scientists Work: Solving the Problems
Much of biology deals with solving problems These problems can be environmental, ecological, health related, etc. No matter what types of problems are being studied, scientists use the same problem-solving steps called… The Scientific Method
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Scientific Method Definition
The scientific method is- A logical and systematic approach or process to problem solving. An organized way of using evidence to learn about the natural world.
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Scientific Method Listing the Steps
Make an Observation Define the Problem Research the Problem State the Hypothesis Experiment to test Hypothesis Collect and Record Data Analyze Data Draw Conclusions Determine Limitations Report Results If needed, Do more investigation
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Scientific Method Let’s break each of these steps down into their individual components: Ask Question Do Background Research Construct Hypothesis Think! Try Again Test with an Experiment Analyze Results Draw Conclusion Hypothesis is True Hypothesis is False or Partially True Report Results
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1. Observing Make an observation See something unusual
As we all know, frogs have four legs. Make an observation See something unusual Frogs with incorrect number of legs! What’s up with these froggies?
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2. Questioning Recognize, state or define the problem
Must be in the form of a question The obvious question is: What is causing these deformities?
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3. Researching Gather information related to the problem
Read, observe, measure, take samples, etc. How frogs normally develop from eggs The % of frogs with the deformities Number of other species in the pond with deformities Previous or new pollutants in the pond Change in amount of UV (sunlight) exposure on eggs Etc.
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4. Hypothesizing A hypothesis is:
An educated guess, trial answer, possible solution, prediction Must be a statement Must be testable or measurable Is based on your research and previous experience
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5. Experimenting Testing the hypothesis
Pick the hypothesis that makes the most sense and is easy to test Then design a controlled experiment
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Experimenting Let’s look at the text book example of the Scientific Method using Redi’s Experiment on Spontaneous Generation He was trying to disprove the idea of Spontaneous Generation (or actually that flies came from maggots, which came from flies) Francesco Redi (1668)
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Stating the Problem Example: How do new living things come into being?
Spontaneous generation once commonly accepted Redi wanted to show what caused the appearance of maggots (and then flies) on meat
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Belief based on prior observations
If leaf lands on water it becomes a fish If bale of hay left in barn it produces mice Muddy soil gives rise to frogs Meat hung out in the market is the source of flies
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Belief based on prior observations
Redi observed that maggots appeared on meat a few days after flies were on meat No microscope = no way to see eggs But Redi believed that maggots came from eggs that were laid by flies
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Forming a Hypothesis Redi’s Hypothesis: Flies produce maggots.
How could he test this? Through a controlled experiment
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Redi’s Controlled Experiment
Redi used two groups of jars Jars that contained meat and no cover Jars that contained meat and gauze cover Jars with meat Uncovered jars Covered jars
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Control and Experimental Groups
used as a standard of comparison the group containing the factor (variable) that has been changed Control group: Experimental group: (manipulated or independent variable) Two groups of jars Uncovered jars Covered jars
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Variables in an Experiment
Variables - Factors that can be changed Controlled Variables - all the variables that remain constant Manipulated Variable - (also called the Independent Variable) - factor in an experiment that a scientist purposely changes Responding Variable- (also called the Dependent Variable) - the outcome or results, factor in an experiment that may change because of the manipulated variable…. what a scientist wants to observe
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Setting up a Controlled Experiment
In a controlled experiment, only one factor is changed at a time. Independent variable: the factor that is deliberately changed Dependent variable: the factor that the scientist wants to observe; it changes in response to the independent variable
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Variables in Redi’s Experiment
Controlled Variables: jars, type of meat, location, temperature, time Manipulated Variables: gauze covering that keeps flies away from meat
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Let’s think about this.…
Which is the control group? Which is the experimental group? Uncovered jars Covered jars Two groups of Jars with meat Uncovered jars Covered jars
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Redi’s Experiment on Spontaneous Generation
OBSERVATIONS: Flies land on meat that is left uncovered. Later, maggots appear on the meat. HYPOTHESIS: Flies produce maggots. PROCEDURE Manipulated Variables: gauze covering that keeps flies away from meat Uncovered jars Covered jars Several days pass Maggots appear No 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. Controlled Variables: jars, type of meat, location, temperature, time
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6. Collect and Record Data
observations and measurements made in an experiment Types of Recorded Data Quantitative - observations that involve measurements/numbers; i.e. 3 days, 12 maggots, 4 g, 13 sec, 8 liters Qualitative - observations that do not involve numbers, are of a descriptive nature i.e. white maggots covered the meat, leaves were all wilting
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7. Analyze the Data Examine data tables, charts, and graphs
Examine experimental notes Look for trends, patterns, and averages What does the data show Put your data into words
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8. Draw Conclusions Restate the hypothesis:
Example: Flies produce maggots. Accept or reject the hypothesis. Support your conclusion with specific, numerical data. What was Redi’s conclusion? Flies lay eggs too small to be seen. Maggots found on rotting meat are produced from the eggs laid by flies. Maggots are not appearing due to spontaneous generation!
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9. Determine Limitations
Scientists look for possible flaws in their research They look for faulty (inaccurate) data They look for experimental error or bias's They decide on the validity of their results They make suggestions for improvement or raise new questions
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10. Publish Results Communication is an essential part of science
Scientists report their results in journals, on the internet, or at conferences This allows their experiments to be evaluated and repeated Scientists can build on previous work of other scientists Redi’s experiment on insects generation
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Repeating the Investigation
Sometimes results are unexpected. John Needham challenged Redi’s experiment and designed his own to show that spontaneous generation CAN occur under certain circumstances. Lazzaro Spallanzini designed a slightly different experiment to improve on Needham’s work Repeat the experiment!
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Repeating the Experiment (continued)
Louis Pasteur further modified the experiment.
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Scientific Method How Scientists Work Solving the Problems
The reason scientific work is called “RE-search” rather than just "search " is because it is an ongoing process that often times changes our view of the natural world. It is subject to modification in light of new evidence and new ways of thinking.
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S C I E N T I F I C M E T H R E O V D I W
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Can you put these steps in order?
Define the Problem 2 Analyze Data 7 10 8 6 Report Results Make an Observation State the Hypothesis 5 1 4 the Problem 9 3 Determine Limitations
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Steps of Scientific Method in order
1 State the Hypothesis Make an Observation Define the Problem 2 the Problem 3 4 5 6 Analyze Data 7 8 9 10 Report Results Determine Limitations
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Scientific Theory A theory is an explanation of a set of related observations or events based upon proven hypotheses and verified multiple times by detached groups of researchers
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Scientific Law Scientific Method Scientific laws represent the cornerstone of scientific discovery They must be simple, true, universal, and absolute If a law ever did not apply, then all science based upon that law would collapse
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