Earth History
GEOL 2110
Lecture 5
EVOLUTION
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 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
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 Evolution
Jean Baptiste de Monet –
Chevalier de LAMARCK
(1744–1829)
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 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.
Inheritance of Acquired Characteristics
Lamarck’s Giraffes
But again, how are these acquired characteristics passed on?
Darwinian Evolution
Charles Darwin
(1809-1882)
•
•
•
Born in the year that Lamarck published
his ideas about evolution
Embarked on a 5-year voyage (18321835) 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
Darwin’s Epiphany
HMS Beagle
Captain Fitzroy
Ship-side Reading
Malthus (1798) Principles of
Population
Lyell (1830) Principles of
Geology
Darwin
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 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
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 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
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
Evidence of Evolution
Vestigal Structures and Imperfections
Unnecessary body parts
Why would such things
be “created”?
Humans
Tail bones
Appendicies
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)
Evidence of Evolution
Paleogeography
On unconnected continents,
unrelated animals have evolve to
occupy similar environmental
niches
For example – Marsupials of
Australia
“Ecological Convergence”
Next Lecture
EVOLUTION II
Genetics and the Origin of Species
Quiz #2
Chapter 3