EvolutionEvolution

EvolutionEvolution• the underlying theme woven

throughout the text, refers to the processes that have transformed life on earth from its earliest forms to the enormous diversity that characterizes it today

24 November 185924 November 1859

On Origin of the Species by Means of Natural

Selection

by Charles Darwin

Origin of the SpeciesOrigin of the Species

Made 2 major points:–Species evolved from ancestral

species and were not created

–Natural Selection is the mechanism that could result in this evolutionary change

Origin of the SpeciesOrigin of the Species• Challenged Western culture

• Darwin’s viewpoint contrasted sharply with the currently accepted concepts:

–the earth’s age

–the 1 week creation

Origin of the SpeciesOrigin of the SpeciesMany Greek philosophers believed

in the gradual evolution of life

However:–Western Culture was

influenced by Plato and Aristotle

Platonic PhilosophyPlatonic Philosophy

Idealism – essentialism

2 coexisting worlds an ideal eternal “real” world an illusionary imperfect world

“ours”

Platonic PhilosophyPlatonic Philosophy

• Variations in plant and animal populations were imperfect forms of the ideal forms

• Evolution would be counterproductive in a world where ideal forms were already perfect

Aristotle PhilosophyAristotle Philosophy

• Organisms range from simple to complex. Occupied levels of an ascending ladder. (scala naturae)

• Species are fixed and do not evolve

• Lasted for 2000 years

Creationist - EssentialistCreationist - Essentialist

Species were individually created and fixed became embedded I western thought as the Old Testament account of creation from the Judeo-Christian culture fortified prejudice against evolution

Creationist - EssentialistCreationist - Essentialist

• Natural Theology: a philosophy that a creator’s plan could be revealed by studying nature

• Adaptations of organisms were evidence that a creator had a purpose for each

Creationist - EssentialistCreationist - Essentialist

• Natural Theology’s major objective was to classify each species of God’s created steps of the Aristotle ladder

Carolus Carolus LinnaeusLinnaeus

1707-1778

Carolus LinnaeusCarolus Linnaeus

• A Swedish physician and botanist, sought order in the diversity of life

• ad majorem Dei gloriam–For the greater glory of God

Carolus LinnaeusCarolus Linnaeus

• Known as the father of taxonomy– binomial nomenclaturebinomial nomenclature

• Developed a classification scheme which included a ranking hierarchy

Carolus LinnaeusCarolus Linnaeus

• The clustering of species in taxonomic groups did not imply evolutionary trends

• Purpose was to reveal God’s plan

Deus creavit, Linnaeus disposuit

(God creates, Linnaeus arranges)

Georges CuvierGeorges Cuvier1769-18321769-1832

Georges CuvierGeorges Cuvier• Realized that life’s history was recorded in

fossil-containing strata and documented the succession of fossil species in the Paris Basin

Georges CuvierGeorges Cuvier• Noted that each strata was

characterized by unique set of fossil species and that the older the statrum, the more dissimular the flora and fauna from modern life forms

Georges CuvierGeorges Cuvier• Understood that extinction had

been a common occurance in the history of life since, new species appeared and others disappeared

Georges CuvierGeorges Cuvier• He was still an opponent to

evolution:–Differences in species due to

catastrophic events (droughts, fires floods)

Georges CuvierGeorges Cuvier• New species result of:

–Localized catastrophe resulted in mass extensions

–Repopulation of out side species

Theories of Ecological Theories of Ecological GradualismGradualism

• Gained popularity that would influence Darwin’s concept

Theories of Ecological Theories of Ecological GradualismGradualism

• Principle that profound change is the cumulative product of slow, continuous process

Theories of Ecological Theories of Ecological GradualismGradualism

• Proposed by James Hutton–1875 Scottish Geologist

Theories of Ecological Theories of Ecological GradualismGradualism

• He proposed that we look it was possible to explain the various land forms by looking at mechanisms currently operating in the world

• example: canyons formed by erosion exposing fossils

Charles LyellCharles Lyell

• Expanded Huton’s concept into the theory called uniformitarianism

Charles LyellCharles Lyell

• Uniformitarianism:–in this theory, geological processes

are uniform and have operated from the origin of the Earth to the present.

Charles LyellCharles Lyell

• Idea that the geological processes are so uniform that their rates and effects must balance out through time

• Example: process of mountain building is followed by erosion

DarwinDarwin

• Rejected uniformitarianism but was intrigued by the conclusions of Hutton and Lyell–1. Earth must be ancient (>6000 yr)

–2. substantial change could occur over time

Jean Baptiste LamarckJean Baptiste Lamarck

• First published a document trying to explain the model of evolution in 1809

Jean Baptiste LamarckJean Baptiste Lamarck

• Believed that evolution was driven by innate tendency toward increasing complexity– As organisms attain perfection they

become better and better adapted to their environment

Jean Baptiste LamarckJean Baptiste Lamarck

Proposed 2 mechanisms

1. Use and Disuse

use it or loose it

2. Inheritance of acquired characteristics

by genetics

• Althought his theory was in error, Lamarck deserves credit for proposing:– 1. Evolution is the best explanation for fossil

record and extant diversity of life– 2. The Earth is Ancient– 3. Adaptation to the environment is primarily

product of evolution