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Evolution
Intro to Evolution and
Darwin’s Theory
Peppered Moths of
Industrial England
Peppered Moths of
Industrial England
Peppered Moths of
Industrial England
Peppered Moths of
Industrial England
Peppered Moths of
Industrial England
Evolution: Change over time
Why should we study evolution?
-Scientist use evolution to study biology.
-It helps us understand relationships
between species in ecosystems.
-It explains the development of antibiotics
resistance and insecticide resistance.
-Understanding relationships between
organisms can help us make conclusions in
medical research. It explains how HIV and
influenza can change (mutate).
Darwin’s Theory: Darwin combines
his evidence and develops his theory
of evolution.
Change via Natural Selection.
1. All species have natural genetic variation as a result of random
mutation.
Variation: Genetic diversity, changes within a species
What causes variation within a species?
a. Mutation: DNA change during replication
b. Crossing Over:
Summary
Two moths that belong to the same species but are different
colors is an example of what? Variation
The difference in color was caused by a change in the DNA
of the moth species. What do we call a change in DNA?
A Mutation
Darwin’s Theory: Darwin combines his
evidence and develops his theory of
evolution.
2. Organisms produce more offspring than can survive, and
the environment presents many challenges (selective
pressures) to survival.
Example: Predator-prey interactions, resource shortage,
changes in environmental conditions.
3. There is a struggle for survival. Struggle= Competition.
The fittest individuals will be able to survive (those whose
genes give them an advantage.)
Question: Are the fittest individuals the same in all
environments? No, in different environments, different
traits will be advantageous.
Darwin’s Theory: Darwin combines his
evidence and develops his theory of
evolution.
4. Traits from the survivors are passed on to the
offspring. The frequency of the survivors’ traits
increase in the population over time as the
population adapts to its environment.
Adaptation: Any variation that allows an
organism to survive and reproduce successfully.
Examples: Resistance to toxins, camouflage, ability
to conserve water, antibiotic resistance.
Darwin’s Theory: Darwin combines his
evidence and develops his theory of
evolution.
5. Individuals (and Species) that are not
able to survive and reproduce will
become more susceptible to die off
(become extinct). Their traits/genes will
become extinct with them.
Susceptible= Likely to be affected
Summary
What were the variations in the “organisms” in the moth
slides? Light versus dark moths
What
was the selective pressure?
Birds
Predator
Was the
selective pressure from a predator or prey?
Could little variation in a species cause an organism to die
off (become extinct)? Why or why not?
Yes, if there is a little variation within a species; they may not
be able to adapt well to any changes in their environment.
Genetics and Natural
Selection
Natural selection changes the frequency of certain genes
within a population over time as the population adapts
to its environment.
**Evolution works at the POPULATION level- NOT the
individual level**
Gene Pool- The entire collection of genes among a
population.
Genetics and Natural
Selection
Remember that there can be different versions of a
gene. Each version of a gene is called an allele. You
inherit one allele from each gene from each parent.
Allelic Frequency: The % of a particular allele within a
gene pool can increase or decrease.
If an organism survives in their environment they are
able to reproduce and pass on their genes to their
offspring. This will increase their alleles in the
population.
Summary
In certain cattle, red hair (R) is dominant to white
hair (r). Heterozygous (Rr) cattle are roan in color
and have both red and white hair. What would
happen to the (r) allele if the white calves were more
easily noticed by coyotes?
The percentage of the r allele would decrease in the
population. Therefore, the frequency of white or
roan calves being born would decrease.
Behavior
Behavior
Behavior: How an organism reacts to changes in its internal
and external environment.
What is the affect of natural selection on behavior?
Behaviors will be maintained or removed based on their
overall contribution to the Fitness of an individual. The
behavior must be genetic because selection changes the
frequency of that gene (alleles) in the gene pool.
Example: Read the passage below and answer the
questions that follow.
1. What question was Tinbergen attempting to answer with
his experiment? Was the removal of shell fragments
advantageous to the Black-headed Gulls?
2. Why did Tinbergen set up one area with camouflaged eggs and no
shell fragments?
To have a control group
3. Explain how you would interpret the behavior of the gulls based on
this experiment. The Gulls remove the fragments to protect
the whole eggs from being eaten by the
Carrion crows.
4. How is the behavior of the gulls linked to natural selection?
The gulls that removed the egg fragments had a
greater probability that their offspring would
survive, and, therefore, this behavior was selected
for.
Speciation
Speciation
Speciation: The evolution of a new species from old
species.
How can you tell members of 2 different species apart?
By physical characteristics, DNA, and behavior.
What is a species? A group of organisms that can mate
and produce fertile offspring.
Speciation
How can natural selection produce a new
species?
1.Natural selection causes changes in allelic
frequency of a population.
2.Different parts of a population might change
in different ways.
3.Due to these changes, the 2 parts of the
population are now unable to mate.
Speciation
Reproductive Barrier: Any factor that keeps
fertile offspring from being produced.
4. If the 2 parts can no longer mate, this
means a new species has evolved.
The evolution of a new species from old
ones is called speciation.
Speciation
Examples of Reproductive Barriers:
Geographical Barriers: Rivers, Mountains,
canyons
Temporal (Time) Barriers: Species do not
mate at the same time.
Summary
Consider the species shown in graphs above. If the population of
small (1cm) mosquitoes experiences a mutation that causes them
to become unable to mate with those that are larger (2.5cm),
which of the following would most likely occur over time?
a. The small mosquitoes could become a separate species from the
larger mosquitoes.
b. The small mosquitoes could mate with the larger mosquitoes
forming more mid-sized mosquitoes.
c. The population would return to one more like that found
during 1990.
Evidence of Evolution
Evidence of Evolution
1. Physiological Adaptations: Changes in organism’s
metabolic processes.
Examples: Bacteria developing antibiotic resistance.
2. Fossils: Any evidence of an organism that lived long
ago.
Most fossils form in sedimentary rock. This type of
rock is formed when sediments(sand, pieces of rock)
form layers and is compressed together. Organic
matter trapped between layers decays slowly and a
fossil is left behind.
Examples
Footprints
Pieces of bone
Evidence of Evolution
How do fossils show evidence of evolution? They
can show us what organisms looked like in the
past, and we can trace how they change over
time.
3. Biochemistry: Nearly all organisms share
DNA, ATP, and many enzymes among their
biochemical molecules. The more closely related
organisms are, the more similar their DNA (and
therefore, amino acids) will be.
Evidence of Evolution
The enzyme cytochrome c, occurs in
organisms as diverse as bacteria and bison.
Biologist compared the differences that
exist among species in the amino acid
sequence of cytochrome c. Organisms that
are biochemically similar have fewer
differences in their amino acid sequence.
Summary
The diagram to the right
represents different layers of
soil. The letters represent
fossils of three different
species of organisms.
Which species is most likely
oldest? C
Which species most likely
existed at the same time?
A&B and A&C
Evidence of Evolution
Homologous Structures: Structures found in
organisms with a common evolutionary history.
Examples: Bat wings, whale fins, and human arms all
have similar bone structure and are all mammals.
How do homologous structures show evidence of
evolution? If two organisms have homologous
structures they are related and have come from a
common ancestor.
Evidence of Evolution
5. Vestigial Structures: Structures that have a reduced (or
no) use in an organism, but might have had a larger
use in an ancestral species.
Examples: Human tail bone, whale pelvis bone, snake
“leg” bones.
How do vestigial structures show evidence of evolution?
They indicate a structural history.
Evidence of Evolution
Embryology: The study of an organism’s
early development.
How does embryology show evidence of
evolution? Organisms who share
embryological similarities are probably
related (Share a common ancestor).
Summary
Name six types of evidence used to determine evolution
in organisms.
1. Physiological Adaptations
2. Fossils
3. Biochemistry
4. Homologous Structures
5. Vestigial Structures
6. Embryology
Evidence of Evolution
Diversity: The number of different species in an ecosystem.
Why is a more diverse ecosystem more stable? There is more than
one organism to fill a role, so if one dies, there is a “back up.”
Example: An ecosystem with one producer will fall apart, if that
species goes extinct.
How can natural selection increase diversity? Natural selection
provided a way for new species to evolve, which can increase
diversity.
Evidence of Evolution
Phylogeny: an organism’s evolutionary history
An organism’s phylogeny can be diagram using a
phylogenetic tree. A phylogenetic tree is a branching
diagram that shows evolutionary relationships.
How is the phylogeny of an organism determined?
Scientist classify organisms based on their
similarities in DNA, anatomy, and behavior.
Common Ancestor: A species from which two or
more species separated from.
Summary
Many species are threatened with
extinction. How will this affect biological
diversity?
Phylogenetic Tree
Example #1
Example #2
Questions
1. Which organism is most closely related to a
flowering plant? FERN
1. Which organism is the most primitive?
Protista
1. What kingdom is the common ancestor of all
these plants?
Protista
Example #3
Summary
1. What animal is most closely related to a bird?
Crocodile
1. What animal is most closely related to a lizard?
Snake
1. Is a mammal more closely related to a turtle or a
shark? Turtle
amphibian
1. Is a shark more
closely related to an amphibian or
a turtle?
2. Is a crocodile
Lizardmore closely related to a lizard or a
turtle?