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I. The Goal of Science
I. The Goal of Science
To describe the structure and function of the physical universe
I. The Goal of Science
To describe the structure and function of the physical universe
A. Structural Questions
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I. The Goal of Science
To describe the structure and function of the physical universe
A. Structural Questions
- What IS that?
I. The Goal of Science
To describe the structure and function of the physical universe
A. Structural Questions
- What IS that? - What is it made of?
I. The Goal of Science
To describe the structure and function of the physical universe
A. Structural Questions
- What IS that? - What is it made of? - Where does this fit in my structural description of nature?
I. The Goal of Science
To describe the structure and function of the physical universe
A. Structural Questions
Atomic structure, molecular structure, genetic structure, organismal structure, phylogenetic structure, trophic structure, astronomic structure
I. The Goal of Science
To describe the structure and function of the physical universe
A. Structural Questions
Methods: - descriptive… look in a new way (with new
chemical markers, or stronger telescopes or microscopes.
I. The Goal of Science
To describe the structure and function of the physical universe
A. Structural Questions
Methods: - comparative: what is it similar to that I’ve already
described?
I. The Goal of Science
To describe the structure and function of the physical universe
A. Structural Questions
Methods: - experimental: To “see” quarks, you need to blast
protons against one another in a particle accelerator.
To define a species, molecular systematists determine average DNA similarity between groups and test models statistically.
I. The Goal of Science
To describe the structure and function of the physical universe
A. Structural Questions B. Functional Questions
- How does that work?
http://dsc.discovery.com/videos/time-warp-hummingbird-hover.html
I. The Goal of Science
To describe the structure and function of the physical universe
A. Structural Questions B. Functional Questions
- How does that work? - What causes that?
I. The Goal of Science
To describe the structure and function of the physical universe
A. Structural Questions B. Functional Questions
- How does that work? - What causes that? - Does THIS affect THAT?
I. The Goal of Science
To describe the structure and function of the physical universe
A. Structural Questions B. Functional Questions
- How does that work? - What causes that? - Does THIS affect THAT?
Study processes through time or with different variable states.
I. The Goal of Science
To describe the structure and function of the physical universe
A. Structural Questions B. Functional Questions
Methods: - Natural/historical experiment… compare variable
states across space or time (hard to infer causality – no control over other variables)… can be a post-dictive experiment.
Did a meteorite cause the K-T mass extinction event?
What would we expect to see if it did? - big hole dating to that time
Did a meteorite cause the K-T mass extinction event?
What would we expect to see if it did? - big hole dating to that time - Iridium layer dating to same time
I. The Goal of Science
To describe the structure and function of the physical universe
A. Structural Questions B. Functional Questions
Methods: - Field Experiment: Purposefully change variables in
nature and see how dependent variable changes. (Can infer causality, hard to control all variables).
Does grazing affect species diversity?
I. The Goal of Science
To describe the structure and function of the physical universe
A. Structural Questions B. Functional Questions
Methods: - Lab Experiment: Purposefully change variables in
controlled lab environment and see how dependent variable changes. (Can infer causality, easier to control all variables, may not occur in nature…lab artifact).
Do iron oxides and plants affect arsenic concentrations in water?
I. The Goal of Science
To describe the structure and function of the physical universe
A. Structural Questions B. Functional Questions C. Types of Experimental Questions
C. Types of Experimental Questions
Do frequency distributions (counts) differ?:
- Differ from an expected theoretical ratio(sex ratio of 50:50?)
- Differ from one another?
C. Types of Experimental Questions
Do frequency distributions (counts) differ?:
Do means of groups differ?
C. Types of Experimental Questions
Do frequency distributions (counts) differ?:
Do means of groups differ?
Is there a relationship between variables?
I. The Goal of Science
To describe the structure and function of the physical universe
A. Structural Questions B. Functional Questions C. Types of Experimental Questions D. Choosing a Method:
- Question may limit options - Maximize realism over control - Constraints of time, energy, and money
II. What makes a good hypothesis?
• Firmly connected to observations or prior research. Not a wild guess.
• A meaningful explanation of a natural phenomenon.• A clear statement, not a vague objective.• A single explanation, not multiple ones.• Eliminates competing explanations.• Generates testable predictions that would either confirm or
falsify the explanation.
III. Logical structure of a hypothesis
• Based on _______ (observations, prior results)…
• we can hypothesize that ______ (explanation)…
• and that therefore under _____ conditions, we should expect to find ______.
(Note that this is the logical structure but not necessarily how you would choose to write it.)
EXAMPLES
III. Some goals of biological hypotheses
• Clarification of multiple variables that were confounded in the original observation.– Age (independent of gender or other factors) is
associated with higher blood pressure.• Explanation of mechanisms.
– Older people have higher b.p. because their their arteries are less elastic.
• Explanation of adaptive/evolutionary value.– Hemlock trees produce chemicals that suppress
seedling growth, because this reduces competition and lets the hemlocks survive and reproduce better.
