Post on 18-Dec-2015
Biology 121: Diversity, Structure and Function
Sonoma State UniversityTom Buckley (plants)Nick Geist (reptiles)
Welcome
General course info
Roll call
Quick lecture on science
Why are you here?
Memorise biological facts
vs
Learn to think like a scientist
CO2
temperature
Correlation vs causation
Correlation vs causation
increasingCO2
increasingtemperature
Hypothesis: CO2 causes
warming
increasingCO2
increasingtemperature
Hypothesis: warming increases
CO2
Hypothesis: CO2 causes
warming
Correlation vs causation
othermechanism
increasingCO2
increasingtemperature
Hypothesis: something else causes both warming
and increasing CO2
Correlation vs causation
increasingCO2
increasingtemperature
Temperature tracks CO2,
therefore CO2 causes warming
induction or deduction?
Correlation vs causation
CO2 absorbs infrared
(IR) light
CO2 absorbs IR, therefore
CO2 warms the atmosphere
= DEDUCTION
increasingCO2
increasingtemperature
Correlation vs causation
= Induction vs deductionCorrelation vs causation
INDUCTION:
inference based on correlation
MAY be correct, may not
DEDUCTION:
inference based on causation
MUST be correct
increasingCO2
increasingtemperature
CO2 absorbs IR
warming increases fires, releasing CO2
Multiple causes are sometimes conflated in nature
CO2
temperature
Multiple causes are sometimes conflated in nature
What is science?
Thales: nature obeys knowable laws
Science: guess principles (hypothesise)
compare with observations (experiment)
Old idea: nature obeys arbitrary whim of deities
Aristotle: deductive logic can uncover these laws
William of Ockham: simplest explanation is probably correct
Newton: mathematics is the language of natural law
Scientific method
Idea
any
Hypothesis
falsifiable
Experiment
controlled
Controlled experiments
We can attribute cause to the changed factor
(no hidden assumptions)
CONTROL TREATMENTnothing is manipulated only one factor is manipulated
Controlled experiments Example from Ch 1
Observation: mammalian predators avoid poisonous coral snakes
Observation: kingsnakes look like coral snakes
Hypothesis: this similarity is the result of mimicry
Controlled experiments Example from Ch 1
Testable hypotheses/predictions:
2. mimicry occurs only in kingsnake populations that it helps
1. avoidance of coral snakes is based on appearance
Controlled experiments Example from Ch 1
Experiment: compare attack rates on artificial kingsnakes
vs. artificial brown snakes
CONTROL TREATMENTnothing is manipulated only one factor is manipulated
1. avoidance of coral snakes is based on appearance
Controlled experiments Example: Figure 1.27 "Inquiry"
Experiment: compare attack rates on artificial kingsnakes
vs. artificial brown snakes
CONTROL TREATMENTnothing is manipulated only one factor is manipulated
Controlled experiments
Experiment: repeat artificial snake experiment in areas
without coral snakes and areas with coral snakes
Hypothesis:
mimicry occurs only in kingsnake populations that it helps
(i.e., only when predators are adapted to avoid coral snakes)
Example from Ch 1
Controlled experiments Example from Ch 1
Controlled experiments Example: Figure 1.27 "Inquiry"
Experiment: repeat expt
in areas without coral snakes and areas with coral snakes
Hypothesis: mimicry occurs only in kingsnake populations that it helps*
(*i.e., only when predators are adapted to avoid coral snakes)
Control vs relevance
Control requires separationof processes
Interactions between processesmay be important
Control vs relevance
Control requires separationof processes
Interactions between processesmay be important
Why are you here?
To absorb enough facts to make sense of big questions
The questions, not the facts, are the point
To learn how to ask the questions for yourself
Review
What is the criterion an hypothesis to be appropriate for science?
must be testable -- i.e., can be disproven by objective observations
EXPERTISE is irrelevant
PRIOR KNOWLEDGE is irrelevant
hypotheses CANNOT BE PROVEN, ONLY DISPROVEN
ReviewWhat is the difference between induction and deduction?
deduction: inference that absolutely must be true
induction: any other inference
e.g., A implies B (A always causes B)
observe A .... DEDUCE that B is true (must be the case)
observe B ... INDUCE that A is true (seems likely, but may not be the case)
Review4. Suppose you want to determine whether Dr Buckley's lectures improve students' understanding of biology.
Your "treatment" group will attend lectures twice per week. What should the control group do?
EVERYTHING the treatment group does EXCEPT attend lectures
NOTHING ELSE DIFFERENT
e.g., DO NOT read other biology texts
DO NOT spend that time studying instead
DO NOT attend a different professor's class