What is EVOLUTION?
What do you already know?
Vimeo evolution videos
What questions do you have about evolution?
Questions that needed answered
1. Why do so many different animals have the
same structures, the arm bones in a
human are the same bones as a flipper in a
whale?
2. Why is the sequence of DNA very similar in
some groups of organisms but not in
others?
3. Why do the embryos of animals look very
similar at an early stage?
Photo courtesy of Swamibu, Flickr Creative Commons
Charles Darwin developed
the Theory of Evolution by
NATURAL SELECTION
... which explained how
organisms changed over
time (ADAPTED)
Alfred Russel Wallace, speculating on evolution
by natural selection, based on his studies of the
distribution of plants and animals. He prompted
Darwin to publish his findings On The Origin of
Species.
Ideas that Helped Shape Darwin’s Thinking
Geologists Hutton and Lyell - concluded that
processes that shaped the earth in the past are the
same as those at work in the present. Also, the earth
would have to be old enough for these processes to
occur over a very long time. This is called
uniformitarianism.
Ideas that Helped Shape Darwin’s Thinking
Lamark's Theory of
Acquired Characteristics
Thought that you would
gain traits if you used them
OR lose them if you didn't
use them (use/ disuse)
!! INCORRECT !!
Photo courtesy of ucumari,
creative commons, flickr
Ideas that Helped to Shape Darwin’s Thinking
Malthus - said that if the human population grew
unchecked there would not be enough resources to
support everyone
●Darwin was a naturalist (what we today call biologists)
●He traveled the world and made observations and
sketches
●Aboard the H.M.S. Beagle, he traveled to the
Galapagos Islands
Marine Iguana
Blue-footed booby
Finch
Giant tortoise
Checkpoint
1. Darwin was traveling to which islands?
2. What was the name of his ship?
3. Name 4 species he observed on the islands.
4. He developed what theory?
5. This theory explained how organisms
_______________ over _________
Checkpoint Answers
1. Darwin was traveling to which islands?
The Galapagos Islands
2. What was the name of his ship?
The Beagle
3. Name 4 species he observed on the islands.
marine iguana, blue footed boobie, tortoise,
and finch
4. He developed what theory?
The theory of evolution by natural
selection
5. This theory explained how organisms
___change____ over ___time______
Watch the video and be ready to take a quiz after!
The Origin of Species: The Making of a
Theory
Student Worksheet
What did Darwin learn from the finches?
Each was adapted to eating a
particular type of island food
He concluded that all finches
came from one ancestral
species
Activity at HHMI - Sorting Finch
Species
●Student Worksheet
alternate Phet simulation with rabbits
Cactus finch, photo courtesy of zrim,
flickr creative commons
1859, Darwin published a
book called:
“The Origin of Species”
Darwin concluded that
evolution occurred
through the process of
natural selection.
Key Points to the Theory of Evolution by Natural Selection
1. Variation exists among individuals in a
species.
2. Individuals will compete for resources
3. Competition would lead to the death of some,
while others would survive
4. Individuals that had advantageous variations
are more likely to survive and reproduce.
5. Selective pressures contribute by increasing
or decreasing reproductive success in a
species.
This process came to be known as Natural
Selection
The favorable variations are called Adaptations
What adaptations do tigers have?
Humans?
Snakes?
Video - evolution stated clearly
Photo courtesy of digitalART2, flickr creative commons
Example of Natural Selection
Say in a species of blob….there exists blobs
of all shapes and sizes (variation)
Blobs eat the little purple organisms that live
underground and on the surface.
During a particularly hot year, food became less
abundant (competition), blobs that had the ability
to dig into the soil to get food had a better chance
of thriving (survival).
Many blobs died that year…….
The ones that survived mated and passed their
genes to the next generation. (reproduction)
The next generation had move blobs with the pointed
noses. That is NATURAL SELECTION.
1.Variation
2.Competition
3.Survival
4.Reproduction
Artificial Selection - humans selected
variations they found useful and bred animals
and plants for those traits.
Much of our agriculture (food,
animals, clothing) is a result of
artificial selection that has
occurred over many generations.
We can influence the EVOLUTION
of a species
Checkpoint
1. What was the name of Darwin’s book?
2. The theory states that
a) individuals of a species have differences, called_________
b) these individuals ________________ for resources
c) some will die, others will ____________________
d) survivors will _________________________ and pass traits to
offspring
3. Any trait that helps an organism survive is called an
_______________________________
4. When humans influence evolution be breeding for desired traits,
it is called _______________________________
Checkpoint
1. What was the name of Darwin’s book?
On the Origin of Species
2. The theory states that
a) individuals of a species have differences, called___variations_
b) these individuals ____compete____________ for resources
c) some will die, others will ____survive________________
d) survivors will ________reproduce_________________ and
pass traits to offspring
3. Any trait that helps an organism survive is called an
_____________adaptation__________________
4. When humans influence evolution by breeding for desired traits,
it is called _____artificial selection____________
In 1-2 sentences, explain this image.
Evidence of Evolution
1. Fossils
2. Homologous structures
3. Analogous structures
4. Vestigial structures
5. Biochemistry & DNA
6. Embryologic Development
7. Direct Observation
video Evidence of Evolution Stated Clearly
Fossil Evidence
shows…..
● similarities between extinct animals and animals that are
alive
● earth’s layers, and species that lived at each time
●Homologous structures – these are parts of the body
that are similar, but have different functions, example of
divergent evolution
Divergent evolution - pattern of evolution in which related
species evolve to become more dissimilar.
ex. The flippers of whales, and the wings of birds
All forelimbs of vertebrates have the same pattern of bones.
•This is evidence of common ancestry.
•Common Descent - describes how a group of organisms share
Homologous Structures
●Analogous Structures - have the same function,
but different structures. DO NOT indicate
common descent, rather, they represent
convergent evolution.
●Convergent evolution - When 2 unrelated species
evolve to have similar features.
Ex. Bird wings and
butterfly wings
●Vestigial Structures – these are structures that
seem to have no function
Whales have pelvic bones that do not attach to legs
Watch a short video clip on whale evolution at PBS
Biochemistry and DNA
When comparing the DNA of one species to another, more
similarities are found in species that are more closely
related.
Lion photo credit: ucumari Tiger photo credit: digitalART2
Evidence of Evolution Paper Lab Activity
Complete the paper lab by analyzing amino acid
sequences of various organisms to identify
differences and similarities.
Embryological Development
Embryos of different species develop in almost identical
ways.
Human fetus at 8 weeks
Direct observation of species change
1.Bacteria become resistant to antibiotics
2.Wolves were bred over many generations to
become dogs (artificial selection) • and then bred
further to create a variety of breeds
Checkpoint
1. ____________ evidence shows when organisms lived on the earth
2. Species that are closely related will have similar _______
3. A _______________ organ is one that has no function.
4. _________________ structures look the same but have different
functions, like the arm of a human and the flipper of a whale.
5. ____________ of different animals develop in the same way.
Checkpoint
1. ____Fossil____ evidence shows when organisms lived on the earth
2. Species that are closely related will have similar __DNA_____
3. A _____Vestigial_______ organ is one that has no function.
4. ____Homologous________ structures look the same but have
different functions, like the arm of a human and the flipper of a whale.
5. ____Embryos_______ of different animals develop in the same way.
Evolution of Populations
Guiding Questions:
● How can populations evolve to form new species?
● How is evolution defined in genetic terms?
● What are the sources of genetic variation?
● What determines the number of phenotypes for a given trait?
● How does natural selection affect single-gene and polygenic
traits?
● What is genetic drift?
● What conditions are required to maintain genetic equilibrium?
● What types of isolation lead to the formation of new species?
● What is a current hypothesis about Galapagos finch speciation?
Populations and Gene Pools
Population – a group of individuals of the same species that
mate and produce offspring
Gene pool – all genes and the alleles for those genes present
in a population
Allele frequency – the number of times an allele occurs in a
gene pool compared to the total number of alleles in that
pool for the same gene.
Populations and Gene Pools
Take home message: Evolution, in genetic terms, involves a
change in the frequency of alleles in a population over time.
Note: Although natural selection acts on individuals it is the
population that evolves, not individuals
Single-Gene and Polygenic Traits
Single-Gene Trait
– Controlled by one gene
that has two alleles
– Two distinct
phenotypes
– Ex: bands or no bands
on snails
Polygenic Trait
– Controlled by more
than one gene
– Many possible
genotypes and
phenotypes
– Ex: Human Height
Checkpoint Questions
Evolution as Genetic Change in Populations
Natural selection on single gene traits
Evolution does not act on genes. Instead it acts on
phenotype frequencies by changing allele frequencies!
Evolution = any change in the relative frequencies of alleles
in a population’s gene pool
Initial Population
Generation 10
Generation 20
Generation 30
90%
80%
70%
40%
10%
20%
30%
60%
Natural selection on polygenic traits
• Natural selection can affect the relative fitness of phenotypes
involving polygenic traits in any of 3 ways:
1. Stabilizing Selection -average form of a trait is favored.
* Graph shifts to the middle*
2. Directional Selection -one extreme form of a trait is favored.
* Graph shifts to the left or right*
3. Disruptive Selection - either/both extremes of a trait are
favored over an average form of a trait.
* graph shifts to the left and right*
Stabilizing selection
Directional selection
Disruptive selection
Genetic Drift
• Genetic Drift = random change in allele frequency
• Acts on small populations
• These chance occurrences can cause an allele to
become more or less frequent in a population
Genetic Bottlenecks
• Genetic Bottleneck = a change in allele frequency
following a dramatic reduction in the size of a
population
• Could result from disease, rapid climate or
environmental change
• Can reduce a population’s genetic diversity
Founder Effect
• Founder Effect = when allele frequencies changes as
a result of the migration of a small subgroup of a
population
• Creates a new gene pool that could be different from
the parent population
Mechanisms that evolution takes place by:
- Natural Selection
- Genetic Drift
- Genetic Bottleneck
- Founder Effect
Evolution vs. Genetic Equilibrium
Hardy Weinberg states that for a population to remain in equilibrium, 5
conditions must be met:
1. large population size
2. random mating
3. no immigration or emigration
4. no mutations
5. no natural selection
equilibrium = RARE
The Process of Speciation
• Species - group that can interbreed and produce fertile
offspring.
• Speciation – the formation of new species, occurs
whenever reproductive isolation develops
The Process of Speciation
Reproductive isolation develops by:
• Behavioral Isolation
• Geographic Isolation
• Temporal Isolation
The Process of Speciation
Reproductive isolation develops by:
• Behavioral Isolation
• Geographic Isolation
• Temporal Isolation
Behavioral Isolation
• Two populations are capable of interbreeding
• Differences in mating rituals prevent interbreeding
• Ex: Similar birds will not interbreed b/c of
different mating songs
Geographic Isolation
• 2 populations are physically separated by
barriers
– Rivers
– Mountains
– Bodies of water
Temporal Isolation
• Two or more species reproduce at different
times
• Ex: One form of cicada emerges every 17
years, the other emerges every 13 years.
Speciation
H-W Analysis
• How to identify evolution in a population
Cladograms
Dichotomous Keys
EVOLUTION
• Mechanisms
• Natural selection
• Mutation
• Genetic drift
• Gene flow (immigration,
emigration)
• Sexual selection
• History of life on Earth
• Diversity of Life
• Speciation and biological
classification based on molecular
evidence
• Variation of org