# The Nature of Science.

## Presentation on theme: "The Nature of Science."— Presentation transcript:

The Nature of Science

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

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

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

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.

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

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.

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

Variables

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

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

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

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

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)

The Hypothesis

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.

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.

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

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

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

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

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.

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

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.

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”

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.

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”

Practice

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

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

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