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Tuesday means….

Learn about the characteristics of living things and the scientific method through observations, inferences, hypotheses, and controlled experiments. Includes resources and worksheets.

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Tuesday means….

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  1. Tuesday means….

  2. Homework collection… http://tasisbiology.wordpress.com

  3. Let’s remember… What are the (8) characteristics of living things?

  4. Characteristics of living things From Prentice-Hall, Section 1-3, p. 15 – 17. Living things: Are composed of units called cells Reproduce Are based on a universal genetic code Grow and develop Obtain and use materials and energy Respond to their environment Maintain a stable internal environment Change over time….when considered as a group

  5. Today we are going to learn about… THE SCIENTIFIC METHOD! The fundamental cornerstone of ALL SCIENCE!!!

  6. You will have a test on the Scientific Method and Experimental Design next Thursday 13th/ Friday14th

  7. Today’s Resources • Handout on the Scientific Method • Worksheet on the Scientific Method • Simpsons Variables Worksheet • Prentice-Hall p. 8 – 14, 1060 - 1063

  8. Words we will understand by the end of today… • Observation • Inference • Hypothesis…and the Null Hypothesis • Data – quantitative and qualitative • Variables • Controlled experiment • Control group

  9. 1. Observations and Inferences • The first step of the scientific method is OBSERVATION • On the basis of our observations, we develop INFERENCES

  10. What’s the difference between an observation and an inference? • Inference: Conclusion based on evidence and reasoning • Reasoning – but not fact • Logical – but not necessarily true… • Inductive:Specific observations extrapolate to general conclusions • Deductive: General observations extrapolate to specific results…

  11. Meet our sewer lice…. With 2 colleagues, make as many observations and inferences about your sewer lice You have 5 minutes….

  12. Observations Inferences

  13. It is imperative to develop an OBJECTIVE, TESTABLE RESEARCH QUESTION - one that can be tested

  14. Worksheet: P3/4: ‘Testable Questions’ Page 3 Group 1: Q 1 - 6 Group 2: Q 7 - 12 Group 3: Q 13 - 17 Page 4 Group 1: Q. 2 Group 2: Q. 3 Group 3: Q 4

  15. Words we will understand by the end of today… • Observation • Inference • Hypothesis…and the Null Hypothesis • Data – quantitative and qualitative • Variables • Controlled experiment • Control group

  16. Based on our observations, we formulate a research question • Our research question is presented as a hypothesis, based on our biological reasoning • We typically present the Null hypothesis

  17. So why do all experiments require a hypothesis? • ‘If………..then………………’ • We must have a principle that we can objectively test • We generally state the Null Hypothesis for cause-and-effect relationships

  18. Words we will understand by the end of today… • Observation • Inference • Hypothesis…and the Null Hypothesis • Data – quantitative and qualitative • Variables • Controlled experiment • Control group

  19. When does a hypothesis become a theory? • When a hypothesis is repeatedly confirmed by experiment and observation (USING THE SCIENTIFIC METHOD), it may become generally considered as a THEORY • THEORIES are the most reliable, rigourous, and comprehensive form of scientific knowledge • Some well known scientific theories: • Cell theory • Evolutionary theory • Theory of relativity • Climate change theory

  20. From hypothesis to controlled experiment In order to ‘test’ our hypothesis and understand the world better, we must design a CONTROLLED EXPERIMENT

  21. Designing an experiment: IDENTIFYING VARIABLES Variables are conditions that affect the outcome of an experiment It is essential that you identify all of the variables which could affect the outcome of your experiment BEFORE you begin Ideally, you want to control (I.e. make constant) ALL of the variables, with the exception of WHAT YOU CHANGE (the independent variable) and WHAT YOU MEASURE (the dependent variable)

  22. Designing an experiment What do we want to CHANGE? What do we want to measure? Are there any other ‘things’ which can affect the ‘thing’ we are measuring? What we change on purpose is called the INDEPENDENT VARIABLE What we MEASURE is called the DEPENDENT VARIABLE

  23. Identify the experimental VARIABLES • Independent – what you change (X- axis) • Dependent – what you measure (Y-Axis) • Controlled Variables – what remains constant (what YOU control) • (Uncontrolled – variables which may be hard to control) • Ideally you should have all variables controlled, excepting one dependent and one independent variable

  24. How do we design a controlled experiment?

  25. Designing a controlled experiment

  26. Designing a controlled experiment • Formulate a focused research question • Identify ALL of the relevant variables (independent, dependent, controlled, uncontrolled) • Decide how to manipulate the independent variable – range • Decide how many repeats of the experiment you need to do • Decide if you are including a control group

  27. Identify the experimental VARIABLES Dependent – what you measure (Y-Axis) Independent – what you change (X- axis) Controlled – what remains constant (Uncontrolled – variables which may be hard to control) Ideally you should have all variables controlled, excepting one dependent and one independent variable

  28. Experiments can be designed in many different ways…. Simple observational study Simple comparison (e.g. test group and control group) ‘Crossover’:each group receives each ‘treatment’ Multiple concentrations/doses etc: multiple groups How much data is enough: designing an experimental model?

  29. The classical five by five model • Used for many biological tests • 5 different test groups • Repeat the test on each group 5 times • This experimental model will provide plenty of information!

  30. Smithers thinks that a special juice will increase the productivity of workers. He creates two groups of 50 workers each and assigns each group the same task (in this case, they're supposed to staple a set of papers). Group A is given the special juice to drink while they work. Group B is not given the special juice. After an hour, Smithers counts how many stacks of papers each group has made. Group A made 1,587 stacks, Group B made 2,113 stacks. No special juice The juice Number of papers stapled Stay off the juice! (The juice doesn’t work) 1. Control Group 2. Independent Variable 3. Dependent Variable 4. What should Smithers' conclusion be? 5. How could this experiment be improved?

  31. Identify the-16. Control Group 17. Independent Variable 18. Dependent Variable 19. Explain whether the data supports the advertisements claims about its product.

  32. Homework for tomorrow 2 questions from the Simpson’s Worksheet (Bart and Lisa) Convert one of the two experiments into a 5 X 5 model

  33. 20. Describe how Lisa would perform this experiment. Identify the control group, and the independent and dependent variables in your description.

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