1. The Nature of Science

2. Goal of Science Investigate and understand the natural world
Explain events in the natural world
Use those explanations to make useful predictions

3. Characteristics of Science
Assumes natural causes (no supernatural)
Is repeatable
Makes predictions
Uses Scientific Method
Authoritativeness

4. Inferences
A logical interpretation based on prior knowledge or experience
Example: A researcher tests water in a reservoir but cannot test every drop. She collects samples. If all the samples are safe, she infers that all the water in the reservoir is also safe

5. Hypothesis, Theory, and Law
A hypothesis is a proposed scientific explanation for a set of observations
A theory is a well-tested explanation that covers a broad range of observations
A law is a theory that has been so universally and completely tested that it is considered absolute and in essence, a fact. Most people now consider theory and law to be the same thing.

6. Amount of testing and observations
LESS
Hypothesis
Amount of testing and observations
Theory
MORE
Law

7. Hypothesis vs. Theory
In science, nothing can ever be proved. Things can only be disproved. There is always the possibility that new information will be found that changes a hypothesis or theory.

8. Scientific Method
An logical thought process used by scientists to understand our world
FIVE STEPS:
Ask a question (Form a question)
State a hypothesis
Design an experiment/procedure
Record and analyze data
Draw a conclusion

10. Variables

11. Variables
Anything that changes (or could change) in an experiment is a variable
Anything that could affect another thing is a variable

12. Independent Variable
An independent variable is the one that you, as the researcher, change in the experiment
It is also called “the manipulated variable” because it is the one you manipulate
Goes on the X-AXIS on graphs

13. Dependent Variable
This is the one that changes as the experiment progresses – it is dependent on the independent variable.
This is also called “the responding variable”
Goes on the Y-AXIS on graphs

14. Examples
“If the thickness of annual growth rings in trees is related to annual rainfall….”
The thickness of the rings is the dependent variable
The rainfall is the independent variable

15. Example:
You are curious to see if the temperature of the water affects the respiration of goldfish
Independent variable: Temperature of water
Dependent variable: Respiration (number of gill openings and closings)

16. The Hypothesis

17. Examples of Good Hypotheses:
If the direction of root growth is related to gravity, then growing roots will always turn toward the earth regardless of the orientation of the seed.
If the thickness of annual growth rings in trees is related to annual rainfall, then examining the ring thickness will reveal correlations to the records of rainfall in its environment.

18. Examples of Good Hypotheses:
If the hatching of brine shrimp is related to salinity, then the greater the salt concentration, the higher the hatching rate.
Better:
If the hatching of brine shrimp occurs more often in greater salinity, then when shrimp are raised in two different salt concentrations, they will hatch more often in the solution with the greater amount of salt.

19. Examples of Good Hypotheses:
Not so good:
If brine shrimp are raised in salt water, then they will hatch more.

20. Answers the question of the experiment
The Hypothesis…
Must be testable
you perform a test of how two variables might be related
assumes a natural cause that can be found
Makes a prediction
Answers the question of the experiment
Describes a relationship between the independent and dependent variables
Contains two things within it:
either directly or indirectly describes how the experiment will be done
states the outcome, or result of the experiment

21. Format of the hypothesis:
If ___________________, then __________, ____________

22. Format of the hypothesis:
If (statement showing proposed relationship between independent and dependent variables), then (describes experiment), (predicts outcome)

23. Format of the hypothesis:
If the temperature of water affects the respiration rate of goldfish, then when goldfish are tested in two different temperatures of water, the fish in cold water will have slower respiration than those in warmer water.

24. Question  Hypothesis Problems
Do male frogs croak after mating?
Hypothesis: If
then

25. Question  Hypothesis Problems
Do male frogs croak to find a mate?
Hypothesis:
If male frogs croak to find a mate
then when frogs that have mated are compared with frogs that have not, the mated frogs will no longer croak while the unmated frogs will.

26. The “predicting only” hypothesis problem
The following is NOT a hypothesis because it shows no relationship between an independent and dependent variable. It is a prediction only:
“If I use enzyme A, then protein B will break down”

27. Show relationship and predict
Is the breakdown of protein B related to the presence of enzyme A?
If enzyme A causes the breakdown of protein B, then when enzyme A and protein B are combine, protein B will break down.

28. Show relationship and predict
Do plants turn to face the light?
Bad:
“If I put a plant near light, then it will turn toward it.”
Good:
“If plants turn to face light, then when plants are put near a light, they will turn toward it”

29. Practice

30. Question:
Is there a relationship between height and jumping ability?

31. Identify 2 variables, relate them
Independent (manipulated) variable:
Dependent (responding) variable:
Relationship:

32. Identify 2 variables, relate them
Independent (manipulated) variable:
Overall height
Dependent (responding) variable:
Length a person can jump
Relationship:
The taller a person is, the farther they can jump