Warm Up
With your partner, write a sentence (20
words or less) using two of the following
terms to show your knowledge of
genetic engineering:
* Transgenic Organisms, Recombinant
DNA, Recombinant Bacteria, Selective
Breeding, PCR, Gel Electrophoresis,
Genetically Modified
Changes Over Time
SOL: BIO 8 a-e
Theory of Evolution
• Science is made up of many ideas, theories, and laws. Many of
these ideas have gone through many changes throughout the
years.
• Our job as life-long learners is to examine all the evidence
concerning a particular topic.
• Evolution is part of the Core Knowledge curriculum for Biology.
• The origin of life is a sensitive subject for many people. There
are many theories concerning the change in things over time.
• You may hold a different view than what will be presented as
part of the Core Knowledge curriculum.
• Out goal is to explore the theory of evolution from a scientific
standpoint, not to discount any other theories on the origin of
life.
Charles Darwin
The Father of Evolution
History
•
•
•
During Darwin’s Time(1809 - 1875)
most people believed the Earth was
only a few thousand years old.
They also believed that neither the
planet nor it’s living species had
changed over that thousand years
Darwin’s ideas were shocking and
radical
HISTORY
• Darwin was influenced by many
explorers and great thinkers who were
starting to challenge views about the
world
• Some new ideas that were influential to
Darwin’s discoveries were:
– Taxonomy of Carolus Linnaeus
– Lyell’s “Principles of Geology”
Binomial
System of
Nomenclature
Carolus Linnaeus
(1707 – 1778)
Believed in the “Fixity of Species”
or that all species have remained
unchanged throughout the history
of the Earth.
Charles Lyell
• Father of Geology
• Suggested that layers
of rock form slowly
and are moved up by
the forces beneath
Earth
• His theories
suggested that the
Earth is millions of
years old.
• Suggests that sedimentary rock is
very old – therefore the species that
are represented in this rock must
also be old.
• Most fossils are found in sedimentary
rock.
• Older fossils will be found below
younger fossils.
Charles Lyell
• How did his ideas influence Darwin?
– If the Earth could change over time, might
life change as well?
– The changes (evolution) Darwin would
later suggest would have been possible
only if the Earth were extremely old
Knowledge Check
Who was Linnaeus?
Who was Lyell?
If Lyell looked at fossils in a cross section
of sediment, would the fossils more
towards the surface be older or younger
than those below? Why?
Charles Darwin
At the age of 22,
he joined a 5 year
expedition aboard
the HMS Beagle
to map the coast
of South America
The voyage of the Beagle
Darwin’s Voyage
• Darwin explored and collected specimens
whenever The Beagle landed ashore
• He noticed the diversity of organisms as
he traveled and noticed how animals and
plants seemed remarkably suited for
their environment
• One stop that was important to the
development of Darwin’s theories was the
Galapagos Islands
• These islands are just west of South
America and were particularly interesting
because although they are very close
together, they have dramatically
different climates
• Because they were formed by volcanoes,
they range from barely at sea level to
1500m above sea level
Darwin’s Observations
Land Tortoises
• Shell shape varied from one island to another
• Hood Island Tortoise: Long neck and curved
shell allows this tortoise to reach the high
vegetation
• Isabela Island Tortoise: Dome shaped
shell and short neck as vegetation is
closer to the ground
• Through his observations made in the Galapagos
Islands, Charles Darwin formulated a theory of
how species change over time, called natural
selection.
Knowledge Check
• What was the name of the boat on
which Darwin traveled?
• What unique observation did Darwin
make about the landscape of the
Galapagos Islands?
• What observations did Darwin make
regarding the organisms living on the
island?
Charles Darwin’s
Theory of Evolution
by Natural Selection
1. Heritable
Variation:
Members of a
population have
heritable
variations.
(Inheritance of
traits)
2. Overpopulation: In a population,
more individuals are produced than the
environment can support. They
compete for food and shelter.
(overpopulation- struggle for survival).
3. Survival of the Fittest: Some individuals
have adaptive characteristics that enable them
to survive and reproduce better than other
individuals (survival of the fittest).
Fitness: Ability of an organism to survive and reproduce
4. Adaptation: An increasing number
of individuals in succeeding
generations have these adaptive
characteristics
Darwin described his theory in the form
of a long essay which he called
“On the Origin of Species”.
Concerned about the public’s response
to his ideas
(remember what happened to Galileo)
Arranged to publish his work …
AFTER HIS DEATH !!
He finally decided to publish his essay,
“On The Origin of Species” in 1859
Charles Darwin
At age 50 (1859)
At age 65 (1874)
Charles Darwin
Before publication
After publication
Knowledge Check
What was the name of Darwin’s book?
On what islands did Darwin make
observations that lead him to develop his
ideas about natural selection?
Explain how natural selection can be
observed in a population.
How does Evolution work?
• Evolution is governed by
the principles of genetics
• It is a change in
successive generations of
organisms, due to:
1. random mutation
2. Adaptation
3. Natural selection
4. Extinction
MUTATIONS
• Genetic mutations and variety
produced by sexual reproduction allow
for diversity within a given population.
• Mutations are inheritable changes
because a mutation is a change in the
DNA code
Mutation
• Mutations are
important in how
populations
change over time
because they
result in genetic
changes to the
gene pool.
A mutation may result in change that is:
1. Favorable;
improves a
species’ ability
to exist in its
environment
2. Unfavorable;
does not improve
a species’ ability
to exist in its
environment.
3. Neutral;
neither harms
nor helps the
species.
Adaptation
• Adaptations are structures,
functions, or behaviors that enable a
species to survive.
Adaptation
• Depending on the rate of
adaptation, the rate of
reproduction, and the
environmental factors
present, structural
adaptations may take
millions of years to
develop.
Knowledge Check
• What are the 3 types of changes that
mutations can result in?
• What is an adaptation? (HINT: It is a
NOUN)
Natural Selection
• the survival and reproduction of the
individuals in a population that exhibit
the traits that best enable them to
survive in their environment.
• The Survival of the Fittest
Natural Selection
• Populations produce more offspring
than the environment can support.
Natural Selection
• This leads to
competition for
resources and
individuals with
certain genetic
variations will be
favored to survive
and pass their
variations on to the
next generation.
• These five canine species evolved from a
common ancestor through natural selection
Jackal
African wild
dog
Fox
Thousands to
millions of years
of natural selection
Ancestral
canine
Wolf
Coyote
When humans choose organisms with
specific characteristics as breeding
stock, they are performing the role of
the environment
• This is called “artificial selection”
Example of artificial
selection in plants: five
vegetables derived from
wild mustard
Artificial Selection in Animals: Dog Breeding
German
shepherd
Yorkshire terrier
English springer
spaniel
Hundreds to
thousands of years
of breeding
(artificial selection)
Ancestral dog
Mini-dachshund
Golden retriever
Extinction
• If a species does not
include traits that
enable it to survive
in its environment or
to survive changes in
the environment, then
the species may
become extinct.
Individuals die,
and eventually
the species
becomes extinct.
Knowledge Check
• What is another name for natural
selection?
• What is artificial selection?
• What can lead to extinction in a
population?
WARM UP
• Explain how each process below can
lead to evolutionary change.
– Heritable Variation
– Overpopulation
– Survival of the Fittest
– Adaptation
EVIDENCE
FOR
EVOLUTION
• Darwin argued that living things
have been evolving on earth for
millions of years, and evidence
could be found in:
– the fossil record,
– the geographical distribution of
species
– homologous structures of living
organisms
– Similarities in early development
(embryology)
Fossil Record
• Darwin saw fossils as a record of the
history of life on Earth
• By comparing fossils from older rock
layers with fossils from younger
layers, scientists could document the
fact that life on Earth has
changed over time.
• The study of fossils provides strong
evidence for evolution.
Hominid skulls
Petrified Trees
Scorpion in amber
“Ice Man”
Distribution of species
• On his voyage, Darwin discovered many
species of finches, all similar but
distinctly different from one another
based on where they were found
• He eventually concluded that these
finches had descended with
modification from a common ancestor
as populations adapted to different
environments (adaptive radiation)
Allopatric Speciation
Geographic isolation/separation can lead to
speciation (emergence of a new species)
Homologous Structures
• Structures that have different mature forms but
develop from the same embryonic tissues are
called homologous structures; these structures
provide support to Darwin’s theory of evolution
• Darwin noted striking anatomical similarities
among the body parts of animals with backbones;
the limbs of reptiles, birds and mammals vary in
form and function, yet they are all constructed
from the same basic bones
Homologous Structures
Human
Cat
Whale
Bat
…Not to be confused with
Analagous Structures
• Structures in different species that have the
same appearance, structure, or function but
have evolved separately, thus do not share a
common ancestor.
• For example, birds and some insects have
wings and both species use these for the
same function, to fly. However, birds and
insects evolved separately; they do not share
a common ancestor.
Vestigial Structures
• Homologous structures that apparently
serve no function in an organism and are
allegedly holdovers from an evolutionary
past. Such features, though no longer
useful, are presumed to have been useful in
ancestral species.
• They are vestiges, or traces of homologous
structures in ancestral species
EX.: Wings in
flightless birds
EX.: appendix
in humans,
whale pelvis,
tiny snake
pelvic and limb
bones, and the
eyes in cavedwelling
salamanders
and fish that
are completely
blind.
Why do these structures hang
around ?
• Although they serve no purpose, one
argument states that since these organs
do not affect an organisms ability to
survive and reproduce, natural selection
would not cause their elimination.
Similarities in Embryology
• Many species have very similar
embryonic development.
• The embryo of a chicken, a pig, and a
fish are almost identical at certain
points in their development.
Summary of Darwin’s Theory
• Individual organisms differ, and some of this
variation is heritable
• Organisms produce more offspring than can
survive, which leads to competition for limited
resources
• Organisms best suited to their environment
survive and reproduce most successfully (and
pass their traits on) causing a species to change
over time (natural selection)
• Species alive today are descended with
modification from ancestral species