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Chapter 15
Chapter 15: Theory of Evolution
Section I History of
Evolutionary
Thought
Section II Evidence
of Evolution
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Section III Evolution
in Action
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Chapter
15History of Evolutionary Thought
I. Section
15-1
A. The Idea of Evolution
• Evolution is the process of
change in the inherited
characteristics within populations
over generations such that new
types of organisms develop from
preexisting types.
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Chapter 15Relationships Between Whales
Evolutionary
and Hoofed Mammals
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Chapter of
15 Darwin’s Time
• Ideas
– Most people of the time believed species
were permanent & unchanging.
– Scientific understanding of evolution began
to develop in the 17th and 18th centuries as
geologists and naturalists compared
geologic processes and living and fossil
organisms around the world.
–Study of “strata”- the layers of rock
• Inferred that oldest rock were made first &
would be found on the bottom
• Oldest rock would have oldest fossils
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Ideas about Geology
• Georges Cuvier –catastrophismsudden catastrophic events caused
mass extinction
• Charles Lyell –uniformitarianismsame mechanisms that shaped Earth’s
surface in the past continue to work
today.
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Darwin was not the first naturalist to propose that species
changed over time into new species—that life evolves.
Jean Baptista Lamarck -Theory of Evolution
-proposed that individuals could develop traits during their
lifetime, as a result of experience or behavior
-idea was: inheritance of acquired characteristics as a
mechanism for evolution.
Lamarck believed that the long
necks of giraffes evolved as
generations of giraffes reached
for ever higher leaves.
Lamarck also believed more
simple life forms evolved into
more complex life forms
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15 Ideas
B.Chapter
Darwin’s
Darwin’s Voyage- ship: HMS Beagle
•Studied many things on the islands passed by boat.
•In part because he was so seasick he wanted to get off
the boat.
•Basis for his life work.
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Darwin’s
Ideas
Chapter
15
• Descent with Modification
– Darwin wrote On the Origin of Species by
Means of Natural Selection.
– argued that descent with modification occurs
– all species descended from common ancestors
– natural selection is the mechanism for evolution.
• Natural Selection
– Organisms in a population adapt to their
environment as the proportion of individuals with
genes for favorable traits increases.
– Those individuals that pass on more genes are
considered to have greater fitness.
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Chapter 15
Natural Selection
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Darwin’s Evolutionary Theory
(which he liked to call “natural selection”
not “evolution”)
-over
many generations,
natural selection causes
characteristics of
populations to change.
-natural selection is responsible for evolution.
-organisms with the best adaptations are more likely
to survive & reproduce.
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What is survival of the fittest?
• It is NOT- “King of the Jungle”with the meanest, biggest, most muscular
animal killing all the smaller ones.
• Example- 2 dogs- One is the perfect specimenshiny fur, wins shows, smart, etc. & the other is
small, ugly, mangy, living in the alley.
The ugly dog visits every female dog in the
county and reproduces many times, but the
perfect dog never has puppies-
• which dog will pass on his traits?
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Summary: 4 Main Parts of Darwin’s Reasoning
• 1. Overproduction- more offspring are
produced than can survive
• 2. Genetic Variation- within a population,
individuals have different traits
• 3. Struggle to Survive- individuals must
compete with each other to exist.
• 4. Differential Reproduction- Organisms
with the best adaptations to environment more
likely to survive & reproduce.
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Chapter 15
II. Section 9-2 Evidence of Evolution
• Evolutionary theories are supported when
several kinds of evidence support similar
conclusions.
Evidence of evolution can be found by
comparing several kinds of data:
A. The fossil record
B. Biogeography
C. Anatomy and Development
D. Biological molecules.
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15 Record
A. Chapter
The Fossil
1. The Age of Fossils
– Geologic evidence supports theories about
the age and development of Earth.
– Superposition- if rock layers have not been disturbed,
lower strata is oldest.
– Relative Age - compare to other fossils
– Absolute Age - use radiometric dating
2. The Distribution of Fossils
– Fossil record shows the types & distribution
of organisms on Earth have changed over
time.
3. Transitional Species
– Fossils of transitional species show evidence
of descent with modification.
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Chapter 15
Evidence of Whale Evolution
Skeletons show sequence
of transitional species
that support the hypothesis
that whales evolved from 4
legged land-dwelling
mammals.
Note: tiny, non-functioning
hip bones in modern
whales.
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Chapter 15
B. Biogeography
• Biogeography - the study of the
locations of organisms around the world,
provides evidence of descent with
modification.
• Example: Australia- The Marsupials there
resemble rodents, wolves, cats, anteaters
of other continents. May be evidence that
these species evolved in isolation.
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C.
Chapter 15
Anatomy and Physiology
• Analogous structures -are similar in
function but have different evolutionary
origins.
(Does not show evidence for evolution)
• Homologous structures have a common
evolutionary origin. (shows evidence of evolution)
• Vestigial structure-
structures that are reduced
in size & function- but may have been complete &
functional in an organism’s ancestor.
(shows evidence of evolution)
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Chapter 15
Forelimbs of
Vertebrates
The organisms show
Homologous partsAnatomical structures
that have related
structure,even if the function
is different.
Shows a relatedness- used
to show a common
ancestor.
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Homologous structures
Comparing the structural features found in different
organisms reveals a basic similarity.
example is the forelimb of mammals - Although function
is quite different, they are similar structurally.
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Analogous structures
• We must look at
structures that look &
function the same but
are not derived from
the same embryonic
tissue.
• These features do not
show recent, related
ancestry.
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Vestigial structures
• Features which serve no useful function any longer
in the organism.
• Examples: the pelvis bone in the whale, tailbone &
appendix in humans, pelvis & leg bones in some
snakes, etc
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D. Biological Molecules
-Chromosomes & Macromolecules
• Compare Macromolecules like DNA, RNA & Proteins.
• Can indicate a common evolutionary history.
• Example- the number of differences in amino acids is a
clue to how long ago 2 species “Diverged”
• Divergent Evolution- 2 species become more
and more dissimilar.
• Convergent Evolution- Species which have
different ancestors, but have become more similar
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Chapter 15
Section 2 Evidence of Evolution
Hemoglobin
Comparison
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Proteins indicate degree of relatedness. Differences - Amino Acids in Protein Cytochrome C
Number of different amino acids found in human cytochrome C as opposed to selected organisms
Organism
# of amino acids different
compared to humans
Human
0
Self (Family Hominidae, Order Primates)
Monkey
1
Different family (Pongidae), same order (Primates)
Pig, bovine, sheep
10
Horse
12
Dog
11
Rabbit
9
Chicken, Turkey
13
Duck
11
Rattlesnake
14
Turtle
15
Tuna
21
Different order (Carnivora), same class (Mammalia)
Moth •
Different class (Aves), same phylum (Chordata) - homeothermic
Different class (Reptilia), same phylum (Chordata) - poikilothermic
Different class (Ostheichthys), same phylum (Chordata) - poikilothermic
31 and Structure, 1967-68
Different by
phylum
(Arthropoda),
same Kingdom (Animalia)
(From Atlas of Protein Sequence
Margaret
O. Dayhoff
Candida fungus
51
Different Kingdom (Fungi)
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What is a Phylogenic Tree ?
• A family tree that shows evolutionary
relationships thought to exist among
organisms.
• Is a hypothesis about the relationships.
• Is subject to change - as more evidence is
learned.
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Chapter 15
Developing Theory
• Modern scientists integrate Darwin’s theory with other
advances in biological knowledge.
• Theories and hypotheses about evolution continue to
be proposed and investigated.
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Chapter 15
Section 3 Evolution in Action
Case Study: Caribbean Anole Lizards (p 308) text
• Convergent evolution - organisms that are not closely
related resemble each other because they have
responded to similar environments.
• Divergence and Radiation
– In divergent evolution, related populations become
less similar as they respond to different environments.
– Adaptive radiation is the divergent evolution of a
single group of organisms in a new environment.
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Chapter 15
Natural Selection of Anole Lizard Species
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Chapter 15
Artificial selection.- when a human
breeder chooses individuals that will
parent the next generation.
(ex- dogs)
Co-evolution – When 2 or more
species have adapted to each other’s
influence.
(ex- flowering plants & pollen carrying
insects
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Chapter 15
Section 3 Evolution in Action
Coevolution
• The increasing occurrence of antibiotic resistance
among bacteria is an example of coevolution in
progress.
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Chapter 15
Question:
The graph below shows
the variation in average
beak size in a group of
finches in the Galápagos
Islands over time. These
finches eat mostly seeds.
Use the graph to answer
the question that follows.
Beak size in these finches is
correlated to the size of
seeds they can eat. What can
be inferred from the graph?
1. In wet years, the finches that survive
are mostly those that can eat larger
seeds.
2. In dry years, the finches that survive
are mostly those that can eat larger
seeds.
3. In all years, the finches that survive are
mostly those that can eat larger seeds.
4. In all years, the finches that survive are
mostly those that can eat smaller seeds.
Answer- In dry years, the finches that survive are mostly those that can eat larger seeds.
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Chapter 15
Question:
What does the diagram
The diagram below shows
imply about warbler
possible evolutionary
finches and
relationships between
armadillos?
some organisms. Use the
diagram to answer the
question that follows.
1. They are unrelated.
2. They are equally related to
glyptodonts.
3. They share a common
ancestor.
4. They did not evolve from
older forms of life.
Answer: They share a common ancestor.
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