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Intro to Evolution
Objective 9
• What is Evolution?
• EVOLUTION--
Intro to Evolution
Objective 9
Why Should We Study Evolution?
• Scientists use evolution to ______________
organize
biology.
• It helps us understand relationships between
ecosystems
species in ________________.
• It explains the development of _______________
antibiotic
resistance
and ___________________ resistance.
insecticide
• It explains
how viruses such as
_____________________________ can change.
AIDS and the
Flu
• Understanding
relationships
between organisms
can help us make conclusions in
_______________ ___________.
Medical research
Intro to Evolution
Objective 9
2 Types of Evolution:
Law of Evolution)—
• Microevolution (______
change that occurs within any given
species over time.
Example: A population of bacteria
Antibiotic resistance
develops ______________________.
Theory
• Macroevolution (_____________
of
Evolution) refers to the changes among
species over time.
Example: the replacement of dinosaurs by
Mammals
___________________).
Natural Selection
Objectives 7-9
Charles Darwin proposed his theory of evolution
in 1844.
**Evolution works at the POPULATION level—NOT
individual level**
at the ________________
2 Types of Evolution:
• Microevolution (______
Law of Evolution)—change
that occurs within any given species over time.
Example: A population of bacteria develops
______________________________.
Antibiotic resistance
• Macroevolution
(_____________ of Evolution)
refers to the changes among
species over time.
Theory
Example: the replacement of dinosaurs by
___________________).
Mammals
Natural Selection
Objectives 7-9
How does Natural Selection
(Microevolution) work?
MAIN IDEA: Natural selection changes
the frequency of certain
Genes
______________within
a population
______________________
as the
Gene Pool
Adapts
population ____________________
to
its environment.
Natural Selection
Objectives 7-9
1. All species have natural genetic ____________
asvariation
a result of ____________ mutation.
random
• Variation-Differences in characteristics within a
species
Question: What causes variation within a species?
Mutations and Crossing Over
Natural Selection
Objectives 7-9
2. The environment presents many challenges
(selective pressures) to _________________.
Examples:
predator-prey interactions,
Survival
________________ shortage, changes in
_______________________
conditions)
resource
environmental
Natural Selection
Objectives 7-9
3. There is a struggle for survival. Struggle =
competition
fittest
__________________.
The _________
individuals will be able to survive (those
genes
whose ____________
give them an
advantage).
• Question: Are the fittest individuals the same
in all environments?
No!! – different traits provide an
advantage in different environments
Natural Selection
Objectives 7-9
Traits (Genes) from the survivors are passed
4. _______________
on to their offspring. The frequency of the
survivors’ genes will increase in the population
over time as the population _____________ to
adapts
its environment.
• Adaptation—any variation that allows an
organism to ___________________
successfully.
reproduce
What are the adaptations here?
Natural Selection
Objectives 7-9
5. Individuals (and species) that are not able to
survive and reproduce will die off (become
Extinct Their _____________
________________).
will become
extinct with them.
Traits
(Genes)
Natural Selection
Objectives 7-9
Example of Natural Selection
In 1973 Peter and Rosemary Grant began a study of the
finches on the Galapagos Islands. They noticed that some
finches had large beaks while others had smaller more
slender beaks. Both birds with small beaks and those with
large beaks seemed to feed primarily on small, soft seeds.
While the Grants were on the Islands a drought occurred.
During a drought, plants produce only a few seeds. These
seeds tend to be larger and tougher. Birds with small beaks
are not able to eat these seeds. The Grants found that after
several dry years the average size of the birds’ beaks had
increased.
Natural Selection
Objectives 7-9
• Questions:
1. In this example what variation was present in the
finches?
Size of the beaks in Finches
2. What was the selective pressure?
Drought causing the absence of seeds
3. What change occurred within the population during
the dry years?
The size of the beaks
4. Use the theory of natural selection to explain how this
change occurred.
The Larger beak gene became more popular in the population and
the thin, small beak genes decreased.
Behavior
Objective 11
Behavior –
refers to the actions and mannerisms made
by organisms, systems, or artificial entities in
conjunction with their environment
Behavior
Objective 11
What is the affect of natural selection on
behavior?
Behaviors will be maintained or removed based on
their overall contribution to the _____________
offitness
an individual. The behavior must be
____________________genetic
because natural
selection changes the frequency of that
_____________ (alleles)gene
in the gene pool.
Behavior
Objective 11
Example: Read the passage below and answer the questions that follow.
Animals display various behaviors for many reasons. Generally, behaviors can
be linked to a goal of survival or reproduction. One famous biologist, Niko
Tinbergen, noticed that Common Black-headed Gulls would meticulously
remove the eggshell fragments from their nests after their offspring
hatched. In an attempt to understand this behavior, he painted chicken
eggs so that they were camouflaged into the backgrounds where the gulls
lived and nested. He then placed some broken eggshells near them. He
then noted how many eggs were discovered and eaten by Carrion crows.
He observed that crows were able to easily notice the white interiors of the
broken shells and consumed many more of the camouflaged eggs near the
broken shells than camouflaged eggs with no broken shells near them.
(Taken from Holt Biology Skills Worksheet p13)
Behavior
Objective 11
1. What question was Tinbergen attempting to
answer with his experiment?
Why do gulls remove the shells?
2. Why did Tinbergen set up one area with
camouflaged eggs and no shell fragments?
Experimental control
Behavior
Objective 11
3. Explain how you would interpret the behavior of
the gulls based on this experiment.
Gulls remove shells to keep predators from
eating the other eggs
4. How is the behavior of the gulls linked to natural
selection?
Gulls who remove shells have more
offspring live so the gene that makes them
remove shells is passed on.
The Genetics of Natural Selection
Objective 10, 15-18
Natural selection changes the frequency of
certain _________within
a population
Genes
_______________
as the population
Gene pool
____________________
to its environment.
adapts
**Evolution works at the POPULATION level—
NOT the _________________ level**
Gene Pool—The individual
entire collection of genes
among a _______________.
population
The Genetics of Natural Selection
Objective 10, 15-18
Remember that there can be different versions
of a gene. Each version of a gene is called an
allele. You inherit one allele for each gene
from each parent.
The Genetics of Natural Selection
Objective 10, 15-18
Allelic Frequency—the % of a particular allele
Gene pool
(choice) within a _______ ______.
The Genetics of Natural Selection
Objective 10, 15-18
Example: Sickle Cell Anemia—a recessive
genetic disease that affects red blood cells.
A-dominant allele S-recessive allele
30 people AA 15 people AS 5 people SS
What are the allelic frequencies of A and S?
A = 75/100 or 75%
S= 25/100 or 25%
The Genetics of Natural Selection
Objective 10, 15-18
• If allelic frequencies remain the same from
generation to generation, the population is
Static ???___________ and
said to be in ___________
the population is NOT evolving.
• If the allelic frequencies are changing from
generation to generation then we can
conclude that
Frequencies are changing???
________________________________.
The Genetics of Natural Selection
Objective 10, 15-18
• Natural selection is the MAJOR mechanism for
changing allelic frequencies. However, there
are other mechanisms of evolutionary change.
These include genetic drift, gene flow,
mutation and recombination.
• Genetic Drift—Random change of allelic
frequencies in a small population due to
chance.
The Genetics of Natural Selection
Objective 10, 15-18
The Genetics of Natural Selection
Objective 10, 15-18
Gene Flow—transfer of genes from one
population to another due to immigration or
emigration.
***Explain how gene flow can lead to
evolutionary change.
Gene flow can show how genes move
into or out of a population, thus
changing the frequencies.
The Genetics of Natural Selection
Objective 10, 15-18
Mutation—any change in a sequence of DNA.
***Explain how mutation can lead to
evolutionary change.
Mutations can introduce “new” genes
into a population and thus changing the
Gene Frequencies.
The Genetics of Natural Selection
Objective 10, 15-18
Recombination—exchange of genetic material
that occurs due to crossing over.
***Explain how recombination can lead to
evolutionary change.
Recombination can make new gene
combinations and this can change the
gene frequencies in a population.
Speciation
Objective 13
How can you tell members of 2 different species
apart?
Physical characteristics, DNA,
Behavior
What is a species?
A group of organisms that
can mate and produce
fertile offspring
Speciation
Objective 13
How can natural selection produce a new
species?
1. Natural selection causes changes in
_____________
_______________ of a
Allelic Frequencies
population.
2. Different parts of a population might
Change
_________________
in different ways.
Speciation
Objective 13
3. Due to these changes, the 2 parts of the
mate
population are now unable to __________
Any factor that keeps
Reproductive Barrier—
fertile offspring from being produced.
mate this
4. If the 2 parts can no longer _____________
species
means a new ___________
has evolved.
The evolution of a new species from old ones is
called ______________
speciation or macroevolution.
Speciation
Objective 13
An Example of Speciation:
About 50,000 years ago, the region now known as Death
Valley had a rainy climate and many lakes and rivers that were
interconnected. About 10,000 years ago, the climate began
to get much drier and by 4000 years ago the area had become
a desert. Lakes and rivers that were once connected were
reduced to isolated springs, mostly found in deep clefts
between rocky walls, separated by vast expanses of desert.
The water in each spring varies in temperature and salinity.
Today, many of the springs are inhabited by a tiny fish called a
pupfish. Each spring is home to a different species of pupfish
that is adapted to that particular pool and found nowhere
else in the world.
Speciation
Objective 13
• Describe the reproductive barrier that has
separated the various species of pupfish.
They are too far apart to mate with each other
• Use natural selection to explain how these
various species of pupfish could have evolved
from a single species.
Phylogeny
Objectives 4, 14
Phylogeny—
An organism’s evolutionary history
An organism’s phylogeny can be diagramed using a
phylogenetic tree. A phylogenetic tree is a
branching diagram that shows evolutionary
relationships.
Phylogeny
Objectives 4, 14
Phylogeny
Objectives 4, 14
How is the phylogeny of an organism
determined?
Scientists classify organisms based on their
DNA ______________,
similarities in ________,
Anatomy
and
_______________. Behavior
Phylogeny
Objectives 4, 14
Common Ancestor--
A species from which 2 or more species
separated
Diversity—
The number of different species in an
ecosystem
Phylogeny
Objectives 4, 14
Why is a more diverse ecosystem more stable?
There is more than 1 organism to fill a role, so if one dies
there is a “back up”.
Example- an ecosystem with only one producer will fall
apart
thatnatural
speciesselection
goes extinct
How ifcan
increase diversity?
Natural selection provides a way for new
species to evolve which can raise diversity.
Evidence of Evolution
Objectives 1-3, 5-6
1. Fossils- any evidence of an
organism
__________________
that lived long ago.
sedimentary
Most fossils form in __________________
rock.
This type of rock is formed when sediments (
) form layers and
areand
compressed
Dirt
sand together.
Organic matter trapped between the layers
decays slowly and a fossil is left behind.
Evidence of Evolution
Objectives 1-3, 5-6
Examples:
Whole bodies,shells, bones, waste
How do fossils show evidence of evolution?
They show us what species used to
look like in the past.
Evidence of Evolution
Objectives 1-3, 5-6
2. Biochemistry-- Nearly all organisms share
_________,
ATP, and many enzymes among
DNA
their biochemical molecules
The more closely related organisms are, the
more similar their ________ (and therefore,
DNA
___________ __________)
will be.
Their Traits
Evidence of Evolution
Objectives 1-3, 5-6
Example:
The enzyme, cytochrome c, occurs in
bacteria and
organisms as diverse as ______________
bison. Biologists compared the differences
that exist among species in the
Amino acid
_____________
__________ sequence of
cytochrome c. Organisms that are
biochemically similar have fewer differences in
Amino
Acid
their_________ ________
sequences.
Evidence of Evolution
Objectives 1-3, 5-6
3. Homologous Structures-
Are similar structure in different species
Examples:
Arms, wings, fins
• How do homologous structures show
evidence of evolution?
Organisms that posses the same Homologous
structures have common ancestors.
Evidence of Evolution
Objectives 1-3, 5-6
4. Vestigial StructuresStructures that had a use in ancestors but that
have no use in present day organisms.
Examples:
Pelvic bones in whales and snakes
Tailbones in humans
• How do vestigial structures evidence of
evolution?
They show past ancestral traits
Evidence of Evolution
Objectives 1-3, 5-6
5. Embryology-
The study of characteristics of embryos
• How does embryology show evidence of
evolution?
Organisms with similar embryonic traits
have a common ancestor.