Earth History GEOL 2110
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Transcript of Earth History GEOL 2110
Earth History GEOL 2110
Lecture 5EVOLUTION
Part I
Major Concepts• In the late 1700/early 1800’s, a number of natural scientists
had proposed that evolution of life was likely, however, without a mechanism to explain evolution, the idea was generally dismissed.
• Darwin’s Origin of Species (1859) not only provided multiple lines of emperical evidence for evolution, but moreover, proposed a plausible cause (natural selection).
• With the discovery of genetic theory in the early 1900’s providing a mechanism for evolution, it became overwhelmingly accepted as a “fact” of science.
• The genetics within isolated, small populations provided the triggers for the “origin” of new species
• The mechanisms of evolution are still being figured out, but not the concept of evolution is not in doubt and has achieved the status of a paradigm of science.
Early Ideas about Evolution
• To the early Greeks and Romans, the notion that nature changes/evolves was well accepted
• Christian teachings required that all organisms were created together, at once, and unchanged for all of time
• The notion that God would let organisms go extinct (as proposed by Cuvier and Smith) was antithetical to genesis and heretical
Early Ideas about EvolutionGeorges de Buffon
Histoire Naturelle (1847)• defined the concept of species
(the ability to interbreed)• was the first to emphasize the
importance of environment causingechanges (evolution) within fixed species
• recognized that organism seek to adapt to their environment but did not offer an explanation how this might occur
• noted evidence for inheritance of traits, but again did not offer an explanation.
• Enough time for Evolution was a major sticking point
Early Ideas about Evolution
Erasmus Darwin (1731–1802)Charles’s Grandfather
• as an animal breeder, recognized the subtle changes from generation to generation
• argued that the fitness of an organism to feed itself, protect itself against predators, and its ability to succeed in mating were important factors controlling its survival and thereby its ability to pass on these characteristics to its offspring.
•Still the question remains - how does inheritance work?
Early Ideas about EvolutionDefined “biology” as a study of the plant and animal world• Ideas about evolution published in 1809, where he argued that the fundamental course of nature is change and this change was controlled by environment• Did not ascribe to Buffon’s fixed species concept, but rather believed that organism represent a continuum of change.•Did not believe in extinction, but rather the “loss” of an organism was due to it’s changing into or replacement by another simpler form.
Jean Baptiste de Monet – Chevalier de LAMARCK
(1744–1829)
Inheritance of Acquired CharacteristicsLamarck’s Giraffes
But again, how are these acquired characteristics passed on?
Darwinian Evolution• Born in the year that Lamarck published
his ideas about evolution• Embarked on a 5-year voyage (1832-
1835) around the world on the HMS Beagle where he was charged with documenting the diversity of flora and fauna in the tropics and Southern hemisphere.
• Struck by: • Variety of species• Number and diversity of individuals per
species• The importance of competition for food,
safety from predators, and shelter as his grandfather pointed out
Charles Darwin (1809-1882)
Darwin’s Epiphany
Darwin
Captain FitzroyHMS Beagle
Ship-side ReadingMalthus (1798) Principles of PopulationLyell (1830) Principles of Geology
Natural Selection
• Natural environments change• Individuals within a population of
organisms change• Individual changes that are best fitted
(adapted) to the changes in the environment are the most likely to survive
• “survival of the fittest”
Radiation into Environmental NichesThe Finches of the Galapagos
• Only birds on the islands – no competition
• 4 different genera
• 15 different species
• Each adapted a different beak type reflecting their dietary preference
On the Origin of Species• First draft completed in 1839, but
not published until 1859
• Fearful of backlash from British scholars and clergy
• For 20 years, compiled supporting data
• Primary goals of the book:• Document evidence for
Evolution• Propose a mechanism
(Natural Selection)
Evidence of EvolutionBranching Organization of Life
Early classifications of the animal and plant kingdom show groups within groups within groups based on anatomical features
Best portrayed by a branching family tree implies related lineages
Today, genetic coding affirms that grouping
Evidence of EvolutionHomologous Elements
Diverse organisms share similar organs and features
For example, the bones of appendages in a variety of vertebrates
Green –humerusRed – radiusBlue – ulnaTan – wrist and phalanges
Evidence of EvolutionVestigal Structures and Imperfections
Unnecessary body parts
Why would such things be “created”?
HumansTail bonesAppendicies
Evidence of EvolutionEmbryonic History
All vertebrate embryos go through similar early stages of development
“Ontogeny recapitulates Phylogeny” Hackel (1866)
(i.e. embryonic development repeats evolutionary history)
Evidence of EvolutionPaleogeography
On unconnected continents, unrelated animals have evolve to occupy similar environmental niches
For example – Marsupials of Australia
“Ecological Convergence”
Next Lecture
EVOLUTION IIGenetics and the Origin of Species
Quiz #2Chapter 3