Biology 121: Diversity, Structure and Function Sonoma State University Tom Buckley (plants) Nick...

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