2Goal of Science Investigate and understand the natural world Explain events in the natural worldUse those explanations to make useful predictions
3Characteristics of Science Assumes natural causes (no supernatural)Is repeatableMakes predictionsUses Scientific MethodAuthoritativeness
4InferencesA logical interpretation based on prior knowledge or experienceExample: 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
5Hypothesis, Theory, and Law A hypothesis is a proposed scientific explanation for a set of observationsA theory is a well-tested explanation that covers a broad range of observationsA 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.
6Amount of testing and observations LESSHypothesisAmount of testing and observationsTheoryMORELaw
7Hypothesis vs. TheoryIn 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.
8Scientific MethodAn logical thought process used by scientists to understand our worldFIVE STEPS:Ask a question (Form a question)State a hypothesisDesign an experiment/procedureRecord and analyze dataDraw a conclusion
11VariablesAnything that changes (or could change) in an experiment is a variableAnything that could affect another thing is a variable
12Independent VariableAn independent variable is the one that you, as the researcher, change in the experimentIt is also called “the manipulated variable” because it is the one you manipulateGoes on the X-AXIS on graphs
13Dependent VariableThis 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
14Examples“If the thickness of annual growth rings in trees is related to annual rainfall….”The thickness of the rings is the dependent variableThe rainfall is the independent variable
15Example:You are curious to see if the temperature of the water affects the respiration of goldfishIndependent variable: Temperature of waterDependent variable: Respiration (number of gill openings and closings)
17Examples 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.
18Examples 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.
19Examples of Good Hypotheses: Not so good:If brine shrimp are raised in salt water, then they will hatch more.
20Answers the question of the experiment The Hypothesis…Must be testableyou perform a test of how two variables might be relatedassumes a natural cause that can be foundMakes a predictionAnswers the question of the experimentDescribes a relationship between the independent and dependent variablesContains two things within it:either directly or indirectly describes how the experiment will be donestates the outcome, or result of the experiment
21Format of the hypothesis: If ___________________, then __________, ____________
22Format of the hypothesis: If (statement showing proposed relationship between independent and dependent variables), then (describes experiment), (predicts outcome)
23Format 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.
24Question Hypothesis Problems Do male frogs croak after mating?Hypothesis:Ifthen
25Question Hypothesis Problems Do male frogs croak to find a mate?Hypothesis:If male frogs croak to find a matethen when frogs that have mated are compared with frogs that have not, the mated frogs will no longer croak while the unmated frogs will.
26The “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”
27Show 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.
28Show 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”
30Question:Is there a relationship between height and jumping ability?
31Identify 2 variables, relate them Independent (manipulated) variable:Dependent (responding) variable:Relationship:
32Identify 2 variables, relate them Independent (manipulated) variable:Overall heightDependent (responding) variable:Length a person can jumpRelationship:The taller a person is, the farther they can jump