Bell Ringer 1 Define Qualitative Observation and give

Bell Ringer: 1. Define Qualitative Observation and give an example of one in this room. 2. Define Quantitative Observation and give an example of one in this room 3. Define Inference and give example of inference based upon an observation in this room.

Notes Scientific Method

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

Scientific Method Definition § Scientific Method (Definition): § A logical and systematic approach or process to problem solving. § Purpose is to answer questions and solve problems

Hypothesis – Possible explanation for a set of observations or possible answer to a question. - Is only useful if it can be tested - May be disproved by a single experiment - “Educated Guess” Theory - Well tested explanation that unifies a broad range of observations - May be revised or replaced

Scientific Method Listing the Steps § § § § Make an Observation State Problem Form a testable Hypothesis Design an experiment Collect and Analyze Data Draw Conclusions Communicate Results ***If possible, controlled experiments are designed to isolate and test a single variable.

Variables in an Experiment § Variables (Definition) - Factors that can be changed § Controlled Variables - all the variables that remain constant § Manipulated Variable - variable in an experiment that a scientist purposely changes § Responding Variable- the outcome or results, factor in an experiment that may change because of the manipulated variable…. what a scientist wants to observe

Experimenting § Let’s look at the text book example of the Scientific Method using Françesco Redi’s Experiment on Spontaneous Generation § He was trying to disprove the idea of Spontaneous Generation Francesco Redi (1668)

Stating the Problem § Redi’s Problem: People believed that maggots grew out of raw meat. § How do new living things come into being? § Spontaneous Generation: once a commonly accepted theory § Redi wanted to show what caused the appearance of maggots on meat

Belief based on prior observations (inference) § § If a leaf lands on water it becomes a fish If a bale of hay is left in a barn it produced mice Muddy soil produces frogs Meat hung out in the market is the source of maggots/flies

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

Forming a Hypothesis Redi’s Hypothesis: Flies produce maggots. § How could he test this? § Through a controlled experiment

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

Control and Experimental Groups Control group: § used as a standard of comparison Experimental group: § the group containing the factor (variable) that has been changed (manipulated variable) Two groups of jars Uncovered jars Covered jars

Variables in Redi’s Experiment § Controlled Variables: jars, type of meat, location, temperature, time § Manipulated Variables: gauze covering that keeps flies away from meat § Responding Variable: § Maggots?

Let’s think about this. … 1. Which is the control group? Uncovered jars 2. Which is the experimental group? Two groups of Jars with meat Uncovered jars Covered jars

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 Covered jars Uncovered jars Controlled Variables: jars, type of meat, location, temperature, time Several days pass Manipulated Variables: gauze covering that keeps flies away from meat Responding Variable: whether maggots appear Maggots appear No maggots appear CONCLUSION: Maggots form only when flies come in contact with meat. Spontaneous generation of maggots did not occur.

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

Publish Results § Communication is an essential part of science Redi’s experiment on insects generation § 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

Repeating the Investigation § Sometimes results are unexpected. Repeat the experiment! § 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

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.