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THEORY OF EVOLUTION
Chapter 15
15-1 History of Evolutionary Thought
I. Charles Darwin (1809 – 1882)
A. Studied to be a doctor, then a minister, but
was also a naturalist
B. In 1830’s traveled around world for five
years on the HMS Beagle
C. Went to Galapagos Islands and South
America
D. Noticed that Galapagos tortoises looked
slightly different on each island
E. Also noted that plant/animal species
resembled those on South American mainland
but were not the same
F. Gathered & recorded lots of data (plants,
animals, fossils)
G. Formulated idea of natural selection to
explain how species evolve, or change over time
1. Used his data and the ideas of other
scientists
H. Alfred Wallace – Darwin’s contemporary also
had same ideas, but Darwin published his
manuscript first, On the Origin of Species by
Means of Natural selection(1859)
II. Ideas of Darwin’s Time
A. In 1700’s, most scientists thought species
were fixed and unchanging and that Earth was
1000’s of years old, not billions. Not to
mention that it was considered heresy to go
against the teachings of the church (religion).
B. Nicolaus Steno identified rock strata
(layers) and that lower
layers were older “Law
of Superposition”
1. layers had fossils of
different types of
organisms
C. Georges Cuvier – reconstructed fossils and
proposed that some species were extinct
1. deeper strata had fossils that were
really different from modern orgs
2. found “sudden” changes in kinds of
organisms found in rock strata
3. proposed catastrophism – sudden
geologic catastrophes caused
extinction of species
4. Not all of Cuvier’s ideas are accepted,
but geologic change & extinction are!
D. Charles Lyell – proposed uniformitarianism –
same geological processes that shaped Earth
in the past are still at work now
E. Jean Baptiste Lamarck
1. simple organisms could come from nonliving
things (not true)
2. simpler organisms develop into more complex
ones (not true)
3. inheritance of acquired characteristics – traits
acquired during one’s life are passed down (not
true)
Lamarck was important even though his ideas were
wrong, he was the first to propose evolution but
his proposed mechanisms for evolution in
organisms were wrong
15-2 Evidence of Evolution
I. Fossil Record
• Provides evidence of Evolution
• Fossil Record – fossils found in various layers
of strata. Some fossils have a wide geographic
distribution within a specific time. These
fossils are used to estimate the time of other
less common fossils found in the same strata
(relative age)
• Fossils are remains of once living organisms
and are found only in sedimentary rock
Cast Fossil
Remineralized fossil
Amber Fossil
A. Age of Fossils
• Nicolaus Steno
(1669) – Principle of
Superposition –
lower strata have
fossils of older
organisms than
higher strata .
• Oldest layers on
bottom, youngest
layers on top.
Relative dating v. Absolute dating
– relative dating estimates the age of a fossil based
on the layer of the stata that the fossil is found in
and other fossils found in that strata
– Absolute dating – is done by radiometric dating,
this provides a much more accurate age of the
fossil or material.
C. Transitional Species
• Fossils show that there
were species that were
intermediate between
those of their ancestors
and descendants
• Can show the sequence
of evolution of different
characteristics
• Example – evolution of
whales from four-legged,
land mammals (p. 304)
II. Biogeography
• Biogeography is the study of the location and
distribution of organisms on Earth.
• Closely related
species tend to live
near each other on
Earth & distantly
related species
tend to live far
apart
Example:
• Australian sugar-glider
looks like a North
American flying squirrel,
but is more closely
related to other
marsupials on Australia
• they have similar
adaptations to their similar
environments (convergent
evolution )
• Sugar-glider is a marsupial
because it’s ancestors were
marsupials
• Convergent evolution – two unrelated
species have similar adaptations because
they are exposed to same type of
environment.
III. Comparative Anatomy and
Embryology
• Comparitive Anatomy:
• Homologous
structures - show
common ancestry
(similar form, not
necessarily same
function). So the
underlying
morphology is the
same (look at the
bones and structure)
• Example: forelimb
bones of human, bat,
whale
Analogous structures
• - DO NOT
show
common
ancestry,
but have
similar
function
Vestigial structures
• Have no function in a species, but resemble
structures that do have function in related
species or that did have a function in
ancestors
Example: some snakes and whales have
vestigial remains of pelvis & leg bones that
were present in their walking ancestors
Example: human tailbone resembles those
bones in animals with tails
B. Comparative Embryology
• Embryology – the
study of how an
organism develops
• Similar species
resemble each other
as they develop and
decrease their
resemblance as
development
proceeds
IV. Molecular Evidence
• Species with more similar DNA, RNA, and/or
proteins are more closely related than species
with fewer DNA sequences, and proteins in
common.
15-3 Evolution in Action
I. Divergence and Radiation
• Divergent evolution –
many species evolve
from a common ancestor
as they spread (radiate)
out and occupy different
environments or
ecological niches (niche
– everything about an
organisms life, what it
eats, where it lives, and
how it finds a mate)
Example: adaptive radiation – finches
or tortoises on Galapagos .
• Contrast convergent evolution with adaptive
radiation –
• Convergent evolution - – unrelated species
evolve similar traits because they live in
similar environments
• Adaptive radiation – one species spreading
out to occupy different ecological niches to
deal with competition within the species.
II. Evolution in Action
• Co-evolution – two species
evolve adaptations as a result of each other’s
influence. Think two species that rely on one
another.
Predator and prey
Flowers and polinators
• Artificial Selection – this is a process done by
human control over which individuals breed
and produce offspring based on desired traits.
• Sexual Selection – some individuals have
better success at obtaining a mate. So
they also have better reproductive success.
• Usually the female of the species drives
sexual selection.