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How Scientists Work Chapter 1
Scientific Method 4 Refers to the process of inquiry and investigation that researchers use to gain knowledge. 4 It’s used to understand the world around us
Flowchart Section 1 -2 Scientific Method—Designing an Experiment State the Problem Analyze Results Form a Hypothesis Draw a Conclusion Set Up a Controlled Experiment Publish Results Record Results Go to Section:
Step 1 State the problem 4 The first step in designing an experiment is to state the 4 4 4 4 problem. The “problem” is normally found by an observation or a question Why do some animals have spots? What causes cancer? Why do some animals hibernate? How can the spread of AIDs be controlled? During the 16 th century, some people believed that living things arose from non living things. “How do new living things, or organisms, come into being? ”
Observation 4 When using the “scientific method” you need to use your Observation Skills. 4 An observation involves using one or more of the senses to gather information.
Inference 4 You also may have to use Inference in your scientific processes 4 An inference is a logical interpretation based on prior knowledge and experience.
OBSERVING LIFE Observations & Inferences? 4 On the next slide you will see partial sections of images. Your objective is to record the following on a separate sheet of paper: 1. Image # 2. Describe what you see. (Observations) 3. Hypothesize what the image is. (Inference)
Think and Process Like a Scientist! 4 1. 4 2. 5. 4 3. 6.
And the Results Are…. . 4 1. 4 2. 4 3. ANT Lung Cancer Drosophila 4. Chromosome 5. Insect Eye 6. Insect Camouflage
Think and Process Like a Scientist! 4 7. 4 8. 9. 10.
And the Results Are…. . 4 7. 9. A Cell Ingesting food Glass LIZARD 4 8. Stamen: Male Part of a flower 10. Insect Mimicry
1. Your observations 2. Your Inference. 3. Your Hypothesis Observation Inference Statement The picture is X curved & fragmented. The picture is of a dinosaur HYPOTHESIS: If the remains possess……, then it must be a dinosaur. X
WATCH OUT! WARNING! Why does everyone need to think like a scientist? LIFE APPLICATIONS PETS: You assume or infer that today your dog pooped in his special poop corner! POLICE: Why is it important for Cops to make observations instead of Inferences.
2 types of Observations 4 A Quantitative Observation involves numbers, such as counting or measuring. (Your Data that you get) 4 Example: The plant has five offshoots 4 A Qualitative (Descriptive) Observation involves characteristics that cannot be easily measured or counted such as color or texture. 4 Example: The red bird flew into the birdhouse.
2 Types of DATA 4 Quantitative data 4 Data reported in the form of numbers and statistics 4 Qualitative data 4 Data reported in the form of words and written descriptions.
Which is the better DATA TABLE? 4 Run A or Run B? Run (A) Temp ( C) 1 30 2 50 3 10 4 20 5 40 Time (mins) 8. 0 2. 1 33. 0 16. 0 4. 1 Run (B) Temp ( C) 1 10 Time (mins) 33. 0 2 20 16. 0 3 30 8. 0 4 40 4. 1 5 50 2. 1
Evidence q Information gathered from observations= Evidence Two types: q. Quantitative Data: (numbers) q. Qualitative Data: (descriptions) Give me an example of Qualitative Data vs. Quantitative Data?
What is science? FACTS q organizing evidence to learn about the natural world q based on observations: information from senses q Finding Nemo
What is NOT science? 4 Religion –faith- based supernatural world 4 National Inquirer 4 The Hulk (Science Fiction)
Think like a Scientist! 4 1. Observations 4 2. Make Inferences 4 3. Form Hypothesis
Step 2 Form a Hypothesis 4 A Hypothesis is: 4 A possible explanation of observations 4 A suggested solution to a scientific problem. 4 A possible answer to a scientific question.
Experiment or Experimental Design 4 This is the plan for the research study. 4 The experiment has to be carefully constructed so that other scientists can replicate it to test its validity and reliability 4 A Hypothesis has to be tested! 4 If a hypothesis cannot be tested, it has NO VALUE! 4 Use only one variable at a time to run a test.
Step 3 Design an Experiment 4 An experiment is performed under carefully controlled conditions to test a hypothesis.
Can any of these be tested? 4 Rice is not thrown at weddings any longer because the birds will swallow the rice, drink water and explode their stomach 4 Cow tipping is easy. 4 It is easy to come up behind a cow as it is sleeping and tip it over. 4 Design an experiment 4 John Lennon was a better composer than Beethoven. to support or refute
Spontaneous Generation 4 Let’s get back to the 16 th century question. During the 16 th 4 4 century, some people believed that living things arose from non living things. “How do new living things, or organisms, come into being? ” Scientists came up with a term that describes how living things arose from nonliving things. It was called Spontaneous Generation -Life arose from non living matter). In 1668, Frank Redi proposed a different hypothesis. He believed that flies laid eggs on meat to produce maggots. (Hypothesis)
Figure 1 -8 Redi’s Experiment on Spontaneous Generation Redi’s Experiment Section 1 -2 OBSERVATIONS: Flies land on meat that is left uncovered. Later, maggots appear on the meat. HYPOTHESIS: Flies produce maggots. PROCEDURE Uncovered jars Controlled Variables: jars, type of meat, location, temperature, time Covered jars Several days pass Manipulated Variables: gauze covering that keeps flies away from meat Responding Variable: Maggots appear whether maggots appear No maggots appear CONCLUSION: Maggots form only when flies come in contact with meat. Spontaneous generation of maggots did not occur. Go to Section:
Variables 4 In science, testing a hypothesis often involves designing an experiment. The factors in an experiment that can change are called variables.
1. Independent Variable/ Manipulated Variable 4 The Independent variable is also called the manipulated variable. 4 A hypothesis should be tested by an experiment in which ONLY one variable is changed. 4 These are the conditions that will change. 4 This is the one that you “mess with” or change. 4 Examples: Time, Temperature are the main examples
2. Dependent variable/ responding variable 4 The responses or answers that you get from your experiment
Which is the dependent & independent? 4 Hypothesis: At warmer temperatures, mold will grow faster on bread. 4 What is the Independent variable? 4 Temperature. 4 Dependent variable? 4 Mold growth on the bread
Question 4 A green plant was placed in a flask and a light was placed 4 4 at different distances from the plant. The table below lists the number of bubbles of oxygen gas given off by the plant per minute. What is the independent variable? Distance between the plant and the light What is the dependent variable? Amount of time the plant releases oxygen gas Distance of light from plant (cm) Number of bubbles per minute 10 60 20 25 30 10 40 5
3. Controlled or Constants 4 These do not change. 4 These are variables that you can control and always stay the same. 4 You need a control to show the differences in the experiment. 4 Examples. Types of glass, plants, amount of soil, amount of water, same medicine, same temperature.
Question 4 Biologist perform controlled experiments in the laboratory to gather reliable results. A controlled experiment is one that 4 A) Cannot be repeated over and over again 4 B) Tests at least 2 variables at a time 4 C) Takes a long time to determine the results 4 D) Compares experimental and control group results
Control Group Example 4 Drug companies are constantly studying new medications to help patients. If a pharmaceutical company was researching a new medicine to fight strep throat, it might design an experiment in which it had a pool of patients with strep throat. 4 A portion of the group, the control group, would take the standard antibiotic treatment. 4 The rest of the group, the experimental group, would take the new medication. 4 How does this help scientists with the new medicine?
4 Alexander Fleming had two identical cultures of bacteria which were grown under the same conditions; penicillium mold had been added to only one of the cultures. The bacterial culture in contact with the mold died, while the other culture grew. 4 Fleming concluded that the chemical penicillin, which he isolated from the mold, was responsible for stopping the bacterial growth. 4 1. Which was the control group (which culture)? 4 2. What was the independent variable (manipulated variable) in this experiment? 4 3. What was the dependent variable (responding variable) in this experiment? 4 4. What were the constant controls? (the ones that remained the same) More than one answer here.
Answers 4 1. The bacteria without the penicillium was the control group 4 2. The penicillium was the independent variable since it was added to the bacteria 4 3. The dependent variable was the bacteria’s response. 4 4. The control constants were; the culture of the bacteria, type of substance that the bacteria was grown, the temperature of the bacteria, the dishes that the bacteria were grown in.
Experiment 4 A number of rats are divided into two groups: One group is fed a normal diet, while the other group is fed the same diet but with one necessary mineral left out. The animals receiving the normal diet remained healthy; those in the other group grew weaker. 4 Which is the experimental group? 4 Which is the control group? 4 Formulate a hypothesis based on this experiment.
Answer 4 The experimental group were the mice in which the mineral was missing. 4 The control group were the mice that had the normal diet. 4 Sample answer: The missing mineral in the diet is needed for the health of the rats.
Anton Van Leeuwenhoek 4 Scientist from the Netherlands. 4 1 st person to use lenses to see microscopic organisms in pond water. (He named the microscopic organisms “animalcules” or tiny animals. 4 He made drawings of the “tiny animals” and showed them to other scientists. 4 His observations/discovery of the “tiny animals” affected the arguments concerning spontaneous generation. 4 Scientists could not agree if the tiny animals were alive or how they came to exist. Was SG true or not?
Needham’s Experiment 4 In the 1700’s, a man named John Needham, (British), used an experiment designed to attack Redi’s work. 4 He took a bottle of gravy, heated it, left it open for a while, then sealed it and still found “little animals” in the gravy later. 4 He hypothesized that the animals came from the juice of the gravy.
Section 1 -2 Go to Section: Figure 1 -10 Spallanzani’s Experiment Gravy is boiled. Flask is open. Gravy is teeming with microorganisms. Gravy is boiled. Flask is sealed. Gravy is free of microorganisms.
Other Scientists… 4 Hypothesized that Spallanzani did not allow Oxygen into the sealed flask. Therefore, the little animals (that supposedly lived in the gravy) could not breathe and as a result, no little animals appeared during the experiment.
Tell me… 4 What flaw did supporters of spontaneous generation find with Spallanzani’s experimentation and his resulting conclusion that nonliving gravy did not produce living things?
Answer 4 Spallanzani had excluded air from his experimental sealed jar, and other scientists hypothesized that air was a necessary factor in the process of generating life because air contained the “life force” needed to produce new life.
Figure 1 -11 Pasteur’s Experiment Section 1 -2 Pastuer’s Experiment Broth is boiled. Go to Section: Broth is free of microorganisms for a year. Curved neck is removed. Broth is teeming with microorganisms.
Steps 4, 5, 6, and 7 4 Record Results-get your data 4 Analyze Results-see if you can accept or reject your hypothesis 4 Draw a Conclusion-Redi reasoned, logically, that spontaneous generation did not exist 4 Publish Results—when he published his results, many other scientists wanted to disprove him
Recording and Analyzing Results 4 Scientists keep written records of the observations or data so that other scientists can reproduce the results. 4 Redi’s investigation showed that maggots appeared on the control jars. (What about Spallanzani or Pastuer? What was the control and what was the manipulated variable? ) 4 No maggots appeared in the jars covered with gauze.
Scientific Method 4 Observation 4 Question 4 Review 4 Hypothesis 4 Data collection and analysis 4 Conclusion 4 Theory
Drawing a Conclusion 4 Scientists use the data from the experiment to evaluate the hypothesis and draw a conclusion. 4 In Redi’s experiment, his results supported his hypothesis. 4 He concluded that the maggots were produced by the flies.
Theory 4 If, after numerous tests, a major hypothesis cannot be shown to be false (you prove it to be true), it may be accepted as a theory. 4 A theory is a well tested explanation that unifies a broad range of observations. 4 If your data supports your hypothesis that has been tested in several different ways, then it may become a theory