10.1: Early Ideas About
Evolution
• Objectives: Examine early ideas about
evolution.
• Identify three geological theories that
influenced scientific debate over evolution.
• Warm Up: Have you ever heard the
expression, “survival of fittest”? What does
it suggest to you? With evolution, what is it
that survives?
• Words to Know: Evolution, Species, Fossil,
Catastrophism, Gradualism,
Uniformitarianism.
Early Scientists Proposed Ideas
about Evolution
• Evolution is the
process of biological
change by which
descendants come to
differ from their
ancestors.
• The concept had
been discussed for
more than 100 years
before Darwin
proposed his theory.
Carolus Linnaeus (1700’s)
• Swedish botanist.
• Developed a
classification system for
all types of organisms
known at the time.
• Did not believe that
organisms were fixed and
did not change.
• He proposed that they
could change through
hybridization.
– A Species is a group of
organisms so similar to one
another that they can
reproduce and have
fertile offspring.
Georges Louis Leclerc de Buffon
(1700’s)
• French naturalist in
the 1700’s.
• He proposed that
species shared
ancestors instead of
arising separately.
• He also suggested
that the Earth was
much older than the
6,000 years though
by most.
Erasmus Darwin (1700’s)
• Charles Darwin’s
grandfather.
• Respected English
doctor and poet.
• Proposed all
organisms evolved
from a common
ancestor and that
more-complex forms
of life arose from
simpler forms of life.
Jean-Baptiste Lamarck (1800’s)
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French Naturalist (1809)
Proposed that all organisms evolved
toward perfection and complexity.
Proposed changes in an environment
caused an organism’s behavior to
change, leading to greater use or disuse
of a structure or organ.
The structure would become larger or
smaller as a result.
The organism could then pass these
changes on to its offspring.
Called the Inheritance of
Acquired characteristics.
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Ex: Giraffes had short necks  They
wanted to reach the leaves in the trees
 they stretched their necks long
enough to reach the leaves  over time
their necks stayed long  they passed
these traits onto their offspring.
HE WAS WRONG!!!
What common ideas about organisms did
these scientists share?
Theories of Geologic Change Set
the Stage for Darwin’s Theory
 The early common view was that the Earth
was about 6000 years old, and that neither
the Earth or the species living on it had
changed in that time.
Georges Cuvier (1800’s)
• Believed species could become
extinct.
• Fossils are traces of organisms
that existed in the past.
• He found that fossils in deeper
layers of rock looked much
different from those in the top
layers.
• He explained is observations
with the theory of Catastrophism.
• Catastrophism states that
natural disasters such as floods
and volcanic eruptions have
happened often during Earth’s
long history.
• These event shape landforms
and caused species to become
extinct.
James Hutton (1700’s)
• Scottish Geologist.
• Proposed the idea of
Gradualism which
states that landforms
resulted from slow
changes over a long
period of time.
• Gradualism is a major
component of
evolutionary theory
today.
Charles Lyell (1800’s)
• Published Principles of
Geography in which he
expanded on Hutton’s theory of
gradualism into a theory of
Uniformitarianism.
• Uniformitarianism states that
the geologic processes that
shape Earth are uniform through
time.
• This soon replaced
catastrophism as the favored
theory of geologic change.
• What important concepts about
Earth did Hutton and Lyell agree
upon?
Mining for Black Opal
in the Desert that
used to be a Forest.
10.2: Darwin’s Observations
• Objectives: Describe how Darwin arrived at
his idea about species variation.
• Recognize how Darwin’s discoveries
supported Lyell’s ancient-Earth theory.
• Warm Up: Thinking in terms of genetics,
what is it about a cluster of islands that
makes it a good laboratory for studying
variation? What is it that the islands keep
separate?
• Words to Know: The Origin of Species,
Variation, Adaptation
Charles Darwin- the “Father of Evolution”
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He went on a voyage from 1831 – 1836 on the H.M.S. Beagle as the ships
naturalist. The voyage went around the world and made a very important
stop on the Galapagos Islands (a group of small islands off the west coast
of South America). It was here that Darwin collected samples and observed
the characteristics of many animals and plants varied noticeably among the
different islands.
Darwin began assembling his ideas upon his return from the voyage.
However, he waited over twenty years (1859) before publishing his book On
the Origin of Species. Because he was both stunned and disturbed by
what he had observed/discovered as it challenged the fundamental
scientific beliefs of that time (not to mention religious beliefs). Wallace,
another scientist also had similar ideas.
Darwin Observed Differences
Among Island Species
• Darwin was struck by the
variation in traits he observed
on his travels.
• Variation is the difference in
the physical traits of an
individual from those of other
individuals in the group to
which it belong.
• Ex: Different breeds of
dogs.
• Darwin noted that the species
found on one island looked
different from those on nearby
islands and that many of the
species looked different from
those on the mainland.
• The most notable differences
he discovered were on the
Galapagos islands, an island
chain off the coast of Ecuador.
Darwin Observed Differences
Among Island Species
• Some difference seemed well suited to the animals’ environments
and diets.
• Ex: Saddle-back Tortoises, which have long necks and legs, lived
in areas with a lot of tall plants.
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Domed tortoises, with their shorter neck and legs, lived in wet
areas rich with mosses and short plants.
Darwin Observed Differences
Among Island Species
• Ex: He noticed finches with
strong, thick beaks lived in
areas with a lot of large, hardshelled nuts,while those
species of
• finch with more delicate
beaks were found where
insects or fruit were widely
available.
• What he noticed was
adaptations.
• An Adaptation is a feature
that allows an organism to
better survive in its
environment.
• Adaptations can lead to
genetic change in a population
over time.
• What adaptations did Darwin
see in the finches of the
Galapagos islands?
Darwin Observed Fossil and
Geologic Evidence Supporting
an Ancient Earth.
• Darwin found fossil evidence of species changing over
time.
• He found large fossils in Argentina that looked like a
larger version of current animals.
• He concluded that it must have taken a large amount of
time in order for those changes to occur.
• Earth had to be more than 6000 years old.
• He also found marine fossils in the Andes mountains.
• He experienced an earthquake that showed him first
hand how land underwater was forced above sea level.
• What could account for fossils of marine organisms
being found on top of modern-day mountain ranges?
10.3: Theory of Natural Selection
• Objectives: Compare artificial selection to
natural selection.
• Examine the factors Darwin considered in
forming his theory of natural selection.
• Summarize the four principles of natural
selection.
• Warm Up: Why would Darwin turn to animal
and plant breeders as a source of
information in studying variation?
• Words to Know: Artificial Selection,
Heritability, Natural Selection, List 4 Main
Principles to the Theory of Natural Selection,
Fitness
Artificial Selection
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Artificial selection is the process by which humans change a species by breeding it for
certain traits.
Humans then determine which traits are favorable and then breed individuals that show
those traits.
Heritability is the ability of a trait to be passed down from one generation to the next.
Darwin compared what he learned about breeding to his ideas on adaptation.
He concluded that those traits that were not beneficial could be selected out.
Darwin applied his views to the “Theory of Natural Selection”.
Natural Selection is a mechanism by which individuals that have inherited beneficial
adaptations produce more offspring on average than do other individuals.
In nature, the environment is the selecting agent.
Struggle for Survival
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Thomas Malthus proposed that
resources such as food, water,
and shelter were natural limits to
population growth.
That is, human populations would
grow geometrically if resources
were unlimited.
Instead disease and a limited food
supply kept the population
smaller.
Darwin reasoned a similar
situation took place in nature.
Darwin proposed that these
adaptations arose over many
generations and called this
process of evolution “descent
with modification”.
How did Malthus’s economic
theory influence Darwin?
Natural Selection Explains how
Evolution Can Occur
• There are 4 main principles
to the theory of natural
selection:
1. Variation
• The heritable differences that
exist in every population are
the basis for natural selection.
• The differences among
individuals result from
differences in the genetic
material of the organisms,
whether inherited from a
parent or resulting from a
genetic mutation.
Natural Selection Explains how
Evolution Can Occur
2. Over-reproduction
• While having many offspring raises the chance
that some will survive, it also result in
competition between offspring for resources.
Natural Selection Explains how
Evolution Can Occur
3. Adaptation
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Certain variations allow some individuals to survive better than
others.
More successful individuals are “naturally selected” to live longer
and to produce more offspring that share those adaptations for
the environment.
Natural Selection Explains how
Evolution Can Occur
4. Descent with
Modification
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Over time, natural selection will result in
species with adaptations that re well suited
for survival and reproduction in an
environment.
More individuals will have the trait in every
following generation, as long as the
environmental conditions stay the same.
Examples: Jaguars
11,000 years ago, many species faced
extinction.
Jaguars faced a shortage of food due to
climate change. Mammals were less
available, but reptiles were numerous.
Jaguars with larger jaws and teeth were
better able to survive and thus pass those
traits onto their offspring.
In Biology, the term Fitness is a measure
of the ability to survive and produce more
offspring relative to together member of the
population in a given environment.
What are the similarities and differences
between natural selection and artificial
selection?
Changing Environments
• Ecologists observed an example of
natural selection acting on existing
traits within a population of
medium ground finches on one of
the Galapagos Islands.
• A drought in 1977 suddenly
reduced the amount of small, soft
seeds that the finches preferred.
• However there were still plenty of
large, tough-shelled seeds.
• Because the large-beaked finches
in the population were able to
crack the large, tough seeds, they
did not starve.
• The next year, they noticed a big
increase in they number of largebeak hatchlings and most of the
smaller beaked birds died.
Adaptations as Compromises
• Not all adaptations result
in individuals that are
perfectly suited to their
surroundings.
• Ex: Pandas have a
structure in their wrist that
acts like a thumb. The
thumb is actually an
enlarged wrist bone that
they use to help hold
bamboo. It is not
considered a true thumb
though.
• Why is the panda’s
“thumb” considered an
adaptive compromise?
10.4: Evidence of Evolution
• Objectives: Recognize the major
sources of evidence for evolution.
• Examine the pattern of features that
reveal the history of a species.
• Warm Up: Why are the larger fossil
organisms so different from the
animals on Earth today?
• Words to Know: List all 9 Evidence of
Evolution with definitions.
Evidence of Evolution:
1. Fossils
• In the late 1700’s
geologists wondered why
certain types of fossils
were found in some
layers of rock and not
others.
• Later studies suggested
that the fossil organisms
in the bottom, or older,
layers were more
primitive than those in the
upper or newer layers.
Evidence of Evolution:
2. Biogeography
• Recall that Darwin saw that island plants and animals looked like,
but were not identical to, species on the South American continent...
• He hypothesized that at some point in the past, some individuals
from the South American mainland had migrated to the islands.
• Different ecosystems favored different traits and there speciation
occurred.
• Biogeography is the study of the distribution of organisms around
the world.
Evidence of Evolution:
3. Comparative Embryology
• A study proposing a
relationship between crabs,
which can walk, and
barnacles, which are fixed in
one place as adults, fascinated
Darwin.
• He noticed that immature
crabs and barnacles looked
similar, but the adults were
different.
• Comparative embryology
now studies those similarities
between organisms.
• Another example:
pharyngeal pouches and
“tails” as embryos in a
variety of chordates.
Evidence of Evolution:
4. Homologous Structures
• Homologous structures are features that are similar in
structure but appear in different organisms and have
different functions.
• Ex: forelimbs of tetrapod vertebrates (human hand, bat
wing and mole foot).
• The limbs look very similar even though they have
different functions.
Evidence of Evolution:
5. Analogous Structures
• Analagous Structures are
structures that perform a
similar function but are not
similar in origin.
• Ex: Bat wings and insect
wings are both used for
flight, but are NOT similar
in structure.
• Using the terms
homologous and
analogous, identify which
group of structures
provides evidence for a
common ancestor?
Explain.
Evidence of Evolution:
6. Vestigial Structures
Structural Patterns are Clues to the History of a Species
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Some organisms have structures
or organs that seem to lack any
useful function, or at least are no
longer used for their original
purpose.
Vestigial Structures are
remnants of organs or structures
that had a function in an early
ancestor.
Ex: Snakes share a common
ancestor with lizards and dogs.
The tiny pelvic bones and hind
limbs in many snakes are vestigial
structures.
Ex: The appendix in humans. It is
a remnant of part of the large
intestine and was used to help
digest cellulose.
What are vestigial structures, and
how do they demonstrate common
ancestry?
Evidence of Evolution:
7. Comparative Biochemistry
• Comparative
Biochemistry: Study
of an organism on a
biochemical level –
for example: the
similarities of amino
acids in hemoglobin
of the blood of various
vertebrates.
Evidence of Evolution:
8. Genetic Evidence and 9. Direct Observations
• Genetic Evidence: for
example: DNA similarities
between people in certain
parts of the world
compared to people in
other parts of the world.
• Direct Observations:
observations of
evolutionary changes that
occur rapidly – for
example: penicillinresistant bacteria
10.5: Evolutionary Biology
Today
• Objectives: Summarize different types
of evidence that support evolution.
• Recognize the importance of evolution I
unifying all branches of biological
study.
• Warm Up: What was Darwin’s
mechanism for explaining the diversity
of life? Mendel’s mechanism?
• Words to Know: Paleontology
Fossils Provide a Record of
Evolution
• Paleontology is the study of
fossils or extinct organisms.
• The fossil record is not
complete because most living
things do not become fossils
after they die.
• NO fossil evidence has ever
contradicted evolution.
• Many transitional fossils
have been discovered since
Darwin’s work to help
support his theories.
• Why are fossils such as
Basilosaurus isis considered
transitional fossils?
Transitional Fossil Evidence
http://www.nature.com/nature/vide
oarchive/ancientwhale/
Transitional Fossil Evidence
• What has the head of a crocodile and the gills of a fish?
• Tiktaalik of course, this 375 million year old fossil splashed across
headlines as soon as its discovery was announced in April of 2006.
• It is technically a fish, complete with scales and gills — but it has the
flattened head of a crocodile and unusual fins.
• It has a combination of features that show the evolutionary transition
between swimming fish and their descendents, the four-legged vertebrates
— a clade which includes amphibians, dinosaurs, birds, mammals, and of
course, humans.
Molecular and Genetic Evidence
• Because all living things
have DNA, they share the
same genetic code and
make most of the same
proteins from the same
20 amino acids.
• DNA or protein sequence
comparisons can be used
to show probable
evolutionary relationships
between species.
DNA Sequence Analysis
• The sequences of nucleotides in a gene change over
time due to mutations.
• DNA sequence analysis depends on the fact that the
more related two organisms are, the more similar their
DNA will be.
• Pseudogenes
• Sequences of DNA nucleotides known as pseudogenes
also provide evidence of evolution.
• Pseudogenes are like vestigial structures.
• They no longer function but still are carried with
functional DNA.
Homeobox Genes
• Homeobox genes control the development of specific
structures.
• These sequences are found in everything from fruit flies
to humans.
• Protein Comparisons
• Similarities among cell types across organisms can be
revealed by comparing their proteins, a technique called
molecular fingerprinting.
• Cells from different species that have the same proteins
most likely come from a common ancestor.
• Ex: light-sensitive cells from an ancient marine worm
were found to closely resemble those of cells in the
vertebrate eye.
• How have protein comparisons helped determine
ancestral relationships between organisms?
Evolution Unites ALL Fields of
Biology
• Scientists are still actively
studying evolution.
• The theory of evolution
combined with genetics is
sometimes called the Modern
Synthesis of Evolutionary
Theory.
• The field of evolutionary
biology is growing fast.
• The basic principles of
evolution are used in fields
such as medicine, geology,
geography, chemistry, and
ecology.
• How can the idea of a common
ancestor help us understand
new diseases?