Tuesday means….
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Transcript of Tuesday means….
Tuesday means….
Homework collection…http://tasisbiology.wordpress.com
Let’s remember…
What are the (8) characteristics of living
things?
Characteristics of living things
From Prentice-Hall, Section 1-3, p. 15 – 17.
Living things:
1. Are composed of units called cells
2. Reproduce
3. Are based on a universal genetic code
4. Grow and develop
5. Obtain and use materials and energy
6. Respond to their environment
7. Maintain a stable internal environment
8. Change over time….when considered as a group
Today we are going to learn about…
THE SCIENTIFIC METHOD!
The fundamental cornerstone of ALL SCIENCE!!!
You will have a test on the Scientific Method and
Experimental Design next Thursday 13th/ Friday14th
Today’s ResourcesHandout on the Scientific Method
Worksheet on the Scientific Method
Simpsons Variables Worksheet
Prentice-Hall p. 8 – 14, 1060 - 1063
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
1. Observations and Inferences
The first step of the scientific method is OBSERVATION
On the basis of our observations, we develop INFERENCES
What’s the difference between an observation and an inference?
Inference: Conclusion based on evidence and reasoning
Reasoning – but not factLogical – but not necessarily
true…Inductive: Specific observations
extrapolate to general conclusionsDeductive: General observations
extrapolate to specific results…
Meet our sewer lice….With 2 colleagues, make as many observations
and inferences about your sewer lice
You have 5 minutes….
Observations Inferences
It is imperative to develop an OBJECTIVE, TESTABLE
RESEARCH QUESTION - one that can be tested
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
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
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
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
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
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
From hypothesis to controlled experiment
In order to ‘test’ our hypothesis and understand the world better, we must design a CONTROLLED EXPERIMENT
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)
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
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
How do we design a controlled experiment?
Designing a controlled experiment
Designing a controlled experiment
1. Formulate a focused research question
2. Identify ALL of the relevant variables (independent, dependent, controlled, uncontrolled)
3. Decide how to manipulate the independent variable – range
4. Decide how many repeats of the experiment you need to do
5. Decide if you are including a control group
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
How much data is enough: designing an experimental
model?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
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!
1. Control Group
2. Independent Variable
3. Dependent Variable
4. What should Smithers' conclusion be?
5. How could this experiment be improved?
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)
Identify the-16. Control Group
17. Independent Variable
18. Dependent Variable
19. Explain whether the data supports the advertisements claims about its product.
Homework for tomorrow2 questions from the Simpson’s
Worksheet (Bart and Lisa)
Convert one of the two experiments into a 5 X 5 model
20. Describe how Lisa would perform this experiment. Identify the control group, and the independent and dependent variables in your description.