Earth History GEOL 2110 Lecture 5 EVOLUTION Part I
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Major Concepts In the late 1700/early 1800s, 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. Darwins 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 1900s 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.
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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
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Early Ideas about Evolution Georges 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
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Early Ideas about Evolution Erasmus Darwin (17311802) Charless
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?
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Early Ideas about Evolution Defined 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
Buffons 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 its changing into or
replacement by another simpler form. Jean Baptiste de Monet
Chevalier de LAMARCK (17441829)
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Inheritance of Acquired Characteristics Lamarcks Giraffes But
again, how are these acquired characteristics passed on?
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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)
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Darwins Epiphany Darwin Captain Fitzroy HMS Beagle Ship-side
Reading Malthus (1798) Principles of Population Lyell (1830)
Principles of Geology
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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
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Radiation into Environmental Niches The 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
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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)
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Evidence of Evolution Branching 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
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Evidence of Evolution Homologous Elements Diverse organisms
share similar organs and features For example, the bones of
appendages in a variety of vertebrates Green humerus Red radius
Blue ulna Tan wrist and phalanges
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Evidence of Evolution Vestigal Structures and Imperfections
Unnecessary body parts Why would such things be created? Humans
Tail bones Appendicies
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Evidence of Evolution Embryonic History All vertebrate embryos
go through similar early stages of development Ontogeny
recapitulates Phylogeny Hackel (1866) (i.e. embryonic development
repeats evolutionary history)
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Evidence of Evolution Paleogeography On unconnected continents,
unrelated animals have evolve to occupy similar environmental
niches For example Marsupials of Australia Ecological
Convergence
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Next Lecture EVOLUTION II Genetics and the Origin of Species
Quiz #2 Chapter 3
