Chapter 15 note - schallesbiology

Chapter 15: Theory of Evolution
• Who was Charles Darwin?
• How did he come up with the theory
of Natural Selection & evolution?
How did Darwin’s visit to the
Galapagos Islands (off the coast of
South America) affect his thinking?
How are unique organisms, like this
Galapagos Island Tortoise, adapted
to their environment?
Harriet the Tortoise, carried to the
Australian Zoo by Charles Darwin?
• When Darwin’s ship, the Beagle, visited the
Galapagos Islands in 1835, the crew collected
dozens of the huge land tortoises. The adults were
eaten but some small tortoises were taken on the
ship around the world.
• Harriet, mistakenly named “Harry” and thought to
be male for over a century, was 330 lbs & a star at
the Australian zoo. Many people believe she was
one of Charles Darwin’s tortoises.
• Harriet was at least 175 years old and recently
Harriet with the “Crocodile Hunter”,
who was one of many zoo keepers
that cared for her over the years.
Why are there so many kinds of
finches on the Galapagos Islands?
Why are their beaks different?
Why are there so many kinds of beetles?
What is Evolution?
• Simply put:
It is changes that occur in a population over time.
Evolution: a process by which organisms
become more sophisticated over time and in
response to its environment. (especially to a
more advanced or mature stage)
What Evolution is not:
• Evolution does not &
never did mean that
man “descended from
an ape”.
• It means we are
related to them.
• Both man & apes had
a common ancestor.
• Individuals do not evolve
-populations do
- over timein response to the
• Is how scientists explain how all
organisms, both living and extinct, are
• Is considered a “cornerstone” theory
of biology.
• Consists of natural selection,
microevolution & macroevolution.
There exists some controversy- we
will address that issue in this
chapter too.
Chapter 15
Definition 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.
• Ideas of Darwin’s Time
– Most people of the time believed species
were permanent & unchanging.
– Scientific understanding of evolution
began to develop in the 17 and 1800s
– geologists and naturalists compared
geologic processes & living & fossil
organisms around the world.
Scientists began to study Rock layers
& fossils
“strata”- the layers of rock
• Inferred that
oldest rock
were made
first & would
be found on
the bottom
• Oldest rock
would have
oldest fossils
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.
• Catastrophism
• sudden
events caused
• The same
that shaped
surface in the
past continue
to work today.
Jean Baptista Lamarck -Theory of Evolution
that individuals could develop traits
during their lifetime, from 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
Darwin was not the first
naturalist to propose that
species changed over time into
new species—that life evolves.
Even his own grandfather had
discussed the concept of
Chapter 15
Darwin’s Voyage on the
ship: HMS Beagle
•Studied many things on the islands passed by boat.
•he was so
seasick he wanted to get off the boat.
•The things he saw were the basis for his life work.
Descent with
• BOOK: 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.
Darwin’s Evolutionary Theory
(which he called “natural selection” not “evolution”)
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.
Natural Selection
• The process by which individuals that are
better adapted to their environment
survive & reproduce more successfully
than less well adapted individuals do.
• A theory to explain the mechanism of
• Individuals do not evolve
-populations do
- over timein response to the
Note the differences in evolution
theory, Lamark vs Darwin.
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?
Ugly dog with lots of puppies =
more successful than a beautiful
dog with no offspring
Chapter 15
Natural Selection
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 ReproductionOrganisms with the best adaptations to
environment more likely to survive & reproduce.
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.
Chapter 15
A. The Fossil Record
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.
Evidence of Whale
Skeletons show sequence
of transitional species
that support the hypothesis
that whales evolved from 4
legged land-dwelling
Note: tiny, non-functioning
hip bones in modern
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.
Biogeography Marsupials in Australia
• current findings support a
simple paleobiogeographic
hypothesis, that indicates
only a single migration from
South America to Australia
gave rise to all the
Australian marsupials.
• (South America, Antarctica,
and Australia were connected
in the South Gondwanan
Marsupials, a class of mammals with
undeveloped young (live in mom’s pouch)
• Of the 260 known marsupial species, just a couple live in
the Americas, and the rest live in Australia and the
Australasian islands that surround it.
• There are no living
marsupial species native
to Europe, Asia, or Africa.
Placental mammals
out-competed with them
millions of years ago.
The only one in North America is the opossum!
Chapter 15
C. 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
• Vestigial structure-
structures that are
reduced in size & function- but may have been
complete & functional in an organism’s ancestor.
(shows evidence of evolution)
Chapter 15
Forelimbs of Vertebrates
The organisms show
Homologous partsAnatomical structures
that have related
structure, even if the
function Is different.
Shows a relatednessused to show a
common ancestor.
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.
Analogous structures
• We must look at
structures that look
& function the
same but are not
derived from the
same embryonic
• Analogous
features do not
show recent,
related ancestry.
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
Organism may become more
similar or more different over time.
• Divergent Evolution- 2 species
become more and more dissimilar.
• Convergent Evolution- Species
which have different ancestors, but have
become more similar
Divergent evolution:
• example
Sharks that
had a
have become
different than
each other
over time.
• Especially
rays &
D. Biological Molecules
-Chromosomes & Macromolecules
• Provide the most precise information
about the evolution of life
• (This is now the most important evidence! DNA!)
• DNA, RNA & Proteins are Macromolecules
that are compared between organisms.
• Can indicate a common evolutionary history.
• Example- the number of differences in amino
acids is a clue to how long ago 2 species “Diverged”
Hemoglobin Comparison
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
# of amino acids different
compared to humans
Self (Family Hominidae, Order Primates)
Different family (Pongidae), same order (Primates)
Pig, bovine, sheep
Chicken, Turkey
Different class (Ostheichthys), same phylum (Chordata) poikilothermic
Different phylum (Arthropoda), same Kingdom (Animalia)
Candida fungus
Different Kingdom (Fungi)
Different order (Carnivora), same class (Mammalia)
Different class (Aves), same phylum (Chordata) homeothermic
Different class (Reptilia), same phylum (Chordata) poikilothermic
What is a Phylogenic Tree ?
• A family tree that shows
evolutionary relationships
thought to exist among
• Is a hypothesis about the
relationships & is subject to
change as more is learned.
• A phylogenic tree of mammals:
Branches show they are related to each other.
Closer branches show closer cousins.
Farther apart on the branches indicate more
distant relationships.
A Phylogenic Tree- shows how organisms are related!
What is the common ancestor for all these animals?
How are different animals related?
Example: Evolutionary Relationships
Between Whales & Hoofed Mammals
In this
phylogenic tree
- which animals
are most distantly
-which animal
here is most
closely related to
the horse?
Still a Developing Theory
(the theory of evolution is still evolving)
• Modern scientists integrate Darwin’s
theory with other advances in biological
• Theories and hypotheses about evolution
continue to be proposed and investigated.
Types of evolution:
• Convergent evolution - organisms that
are not closely related resemble each other
– become more similar
– because they have responded to similar environments.
• Divergence and Radiation
– In Divergent evolution, related populations
become less similar as they respond to different
– Adaptive radiation is the divergent evolution of
a single group of organisms in a new environment.
How do Darwin’s Finches show
“divergent evolution”
More vocabulary:
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
An example of coevolution
(Explanation of the photo previous page)
The Madagascar star orchid produces nectar at the bottom part
of its slim, foot-long throat.
After observing a specimen, Charles Darwin predicted the
existence of a moth with a proboscis long enough to reach that
Sure enough, decades later the giant hawk moth of Madagascar
was discovered and named Xanthopan morganii praedicta in
honor of Darwin's prescience.
As the moth sucks up the nutrient-rich nectar from the orchid,
packets of pollen stick to its body. When the moth visits other
star orchids to feed again, the pollen rubs off and pollinates
those orchids. The moth gets exclusive access to food and the
orchids get a reliable pollinator
Read more:
• The increasing occurrence of antibiotic
resistance among bacteria is an example
of coevolution in progress.
Case Study:
• Caribbean Anole Lizards
• (p 308) text
Natural Selection of Anole Lizard Species
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
1. In wet years, the finches that survive
are mostly those that can eat larger
2. In dry years, the finches that survive
are mostly those that can eat larger
3. In all years, the finches that survive
are mostly those that can eat larger
4. In all years, the finches that survive
are mostly those that can eat smaller
Answer- In dry years, the finches that survive are mostly those that can eat larger seeds.
The diagram below shows
possible evolutionary
relationships between
some organisms. Use the
diagram to answer the
question that follows.
What does the
diagram imply
about warbler
finches and
Answer: They share a common ancestor.
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.

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