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.