7: Evolutionary Theory
- Page ID
- 299434
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)Scientific Method
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Science
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Use of empirical data to explain phenomena
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Philosophy
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Attempt to understand the nature of life and existence
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The scientific method
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Technique used in the construction and testing of scientific hypotheses
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In order for something to be considered a scientific form of analysis, it must be:
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Experimentally verifiable or falsifiable
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Predictive
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Hypothesis
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Proposed explanation for a phenomenon; must be testable
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Theory
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A complex set of ideas that have undergone rigorous testing, analysis, assessment, and retesting; a well-supported general idea that explains a large set of factual patterns and predicts other patterns
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Variables
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Independent variable
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Variable that is manipulated by the experimenter to produce an effect on the dependent variable
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Dependent variable
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Responds to the independent variable; measured by the experimenter
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Control
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Anything that is held constant and unchanged throughout an experiment
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Any change in the control would indicate that there is an invalid relationship between the independent and dependent variable
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Pre-Scientific Revolution
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Prior to 1800s:
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View that Earth is young, fixed
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Archbishop James Ussher: claimed earth is 6000 years old, based on biblical texts
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Essentialism (Plato, 427-347 B.C.)
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All organisms have essential characteristics that are unalterable
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Species were fixed and unchanging (fixity of species)
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Great Chain of Being (Aristotle, 384-322 B.C.)
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Scale from simple to complex
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Moving toward perfection
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Divine intervention
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Life ordered from simplest to most complex
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Used to justify status in society
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Sovereign rule given from God to the king…
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Many were were told that their place in society was “biologically justified”
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In summary:
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Earth was young
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Species were fixed and didn’t change
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Organisms had an “ideal” form (any variation was seen as disformity)
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“Simpler” organisms were ranked lower in the scale (Great Chain of Being) than more “complex” organisms
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Evolutionary Theory
- The domestication of plants and animals had been occurring worldwide for a long time, so it's certainly possible that many probably had some questions and explanations for genetics and the concept of natural selection before Darwin...
- Kitab al-Hayawan (Book of Animals) by Al Jahiz (776 - 868 A.D., Iraq)
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Has been interpreted as an early discussion on the concept of natural selection.
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Animal mimicry – noted that certain parasites adapt to the color of their host
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Discussed influence of climate, geographic region, and diet on living organisms
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Discussed animal communication and intelligence
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Discussed food chains, social organization of animals
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Hippocrates (460-370 B.C.)
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Beginning of the inheritance of acquired characteristics concept
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Some traits (which are inherited) improve or hinder survival
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Traits are inherited from parents
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Greek physician – influential in medicine
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“Hippocratic oath” – physician must swear, to a number of healing gods, to uphold specific ethical standards
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Zhuangzi (369 BC – 286 B.C.)
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The early philosopher Zhuangzi also discussed the idea of species changing over time (the idea that there are "building blocks" that lead to more complex life forms).
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Carolus Linneaus (1707-1778)
- Binomial nomenclature – taxonomic system for classifying organisms (Genus, species – example: Homo sapiens)
Geologic Change on Earth
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Stratigraphy
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Nicholas Steno – Steno’s Law/Law of Superposition
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Analysis of the order and position of stratigraphic layers
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Catastrophism
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Georges Cuvier (1769-1832)
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Proposed that geologic epochs ended with large-scale, violent natural catastrophes, causing organisms to go extinct and be replaced by new organisms
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Example: meteor strikes, massive floods, supervolcanoes, mega earthquakes
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George-Louis Leclerc Comte de Buffon (1707-1788)
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Critiqued catastrophism
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Argued that catastrophic events are rare
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Earth’s history can more likely be explained by uniform processes
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James Hutton (1726-1797)
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Deposition and erosion: self-regulating system on Earth
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Earth must be much older than 6000 years
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Uniformitarianism
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Charles Lyell (1797 – 1875), James Hutton
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Challenged catastrophism, as well
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Changes on earth’s crust result from continuous, uniform processes over time (these processes occurred in the past and continue to occur in the present)
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Examples: coastline reshaped by tsunami, destruction due to volcanic eruption, formation of mountain ranges, erosion
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Influences on Charles Darwin
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Charles Lyell
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Charles Darwin was interested in Charles Lyell’s work with uniformitarianism
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Influential to Darwin on his voyage on the Beagle
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Erasmus Darwin (1731 - 1802)
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Charles Darwin’s grandfather (also a scholar)
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Believed that there is a “struggle for existence”
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Thomas Malthus (1766 - 1834)
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Human populations increase more rapidly than resources (competition)
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Fitness – better “adapted” organisms are more reproductively successful
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Jean Baptiste de Lamarck (to be discussed later)
Photos:
- See Google slides below: