Download Evolution

What is Evolution?
Evolution- the genetic change of
populations over time
Population- group of organisms of the
SAME species that occupies certain area
Species- organisms that can interbreed
and produce FERTILE offspring
– Ex:
-whitetail rabbits
-sparrows
-deer
-squirrels
Liger (lion and tiger)-infertile
Cama (camel and llama)-infertile
How Do We Know Populations
Evolve?
Population Sampling- technique uses part
of population to represent whole
population
Capture 100 random rabbits
– These rabbits are a representation of all the
rabbits in the area.
– We can study many things within this group…
Genetics of the Population…
Gene Pool- all of the
genes of every individual
in population sample
Frequency- how often
something occurs
Population genetics
involves studying the
frequency with which
certain alleles occur in a
population’s gene pool
In 50 years, will the 
allele frequencies be the
same?
Hardy-Weinberg
• Hardy-Weinberg Equilibrium Principle – frequencies
of the dominant and recessive alleles in a population
change in time due to 5 things:
• Mutations
• Migration
• Natural selection (survival of fittest)
• Small population
• Non-random mutation
• If these things occur, then the frequencies change
and a population evolves
History of Evolutionary Thought
Before 1850, most people believed…
– Earth formed by supernatural events and never
changed
– Earth only a few thousand years old
– Each species was made to fit its environment
– Species never changed and did not go extinct
Early Scientists’ Ideas
Darwin deserves credit for the Theory of
Evolution as we know it today
He was not the first to come up with the idea:
– Carl Linnaeus proposed a new system of
organization for plants and animals based on their
similarities (noticed relationships)
– Erasmus Darwin considered how organisms could
evolve through mechanisms such as competition
– Jean-Baptiste Lamarck presented evolution as
occurring due to environmental change over long
periods of time
Carl Linnaeus
Developed a classification
system for the huge variety of
living things he found
– Wrote book Systema Naturae
in 1735 to reveal his
classification system
– There are currently 1.9 million
species that have been
identified using his method
– Linnaeus’s system of classification
reflects evolutionary relationships
Jean Baptiste Lamarck
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A French naturalist who proposed that
populations of species evolve
His idea proposed:
Changes in an environment cause an
organism’s behavior to change, leading to
greater use or disuse of a structure or organ
The organism would pass on these acquired
changes to its offspring, so a species would
change in time
Idea called “Evolution by inheritance of
acquired characteristics”
Wrong on several accounts
Charles Darwin
At 22, was invited to sail on the
“HMS Beagle”
– Was going to school to be a
minister-believed God created
each species to match its habitat
and they never changed
– Thought Earth was about 6,000
years old and didn’t change, just
like everyone else
Darwin’s Observations
One place of note that
he visited was the
Galapagos Islands
During journey, he made
observations and
recorded them in a
journal
Darwin observed fossil
and geologic evidence
supporting an ancient
Earth
Darwin’s Finches
When Darwin traveled to the Galapagos he
took interest in the finches
He noticed the finch species on the islands
were different, but all resembled one from S.
America
Darwin thought some migrated and new
species evolved
Darwin’s Finches
This is what Darwin
proposed:
– Finches migrated from
South America to the
islands
– Populations on different
islands adapted to
different environments and
food sources they found
– Those that could survive
passed on their genes
– Those that couldn’t survive
perished
Darwin’s Finches
Over time different
mutations accumulated
in the different finch
populations on the
different islands
The populations
diverged, or became
more and more
different from each
other
Darwin’s Finches
The populations on the islands became so different
they no longer mated if they met
Several new finch species evolved from a common
ancestor from S. America
This is an example of macroevolution
Recent finch
research
Speciation
Geographical isolation- members of a population
are separated geographically
– Major step that leads to speciation
– Due to volcanoes, earthquakes, flooding, etc.
– Can lead to divergence and then speciation
Artificial Selection
Artificial selection- human intervention in animal or
plant reproduction to ensure that certain desirable
traits are passed on
Instead of NATURE selecting which traits are
favorable, HUMANS selectively breed those animals
with favorable traits
Ex. dogs or racehorses
Darwin bred pigeons to
explore this idea
Darwin’s Results
In 1859, Darwin published The
Origin of Species
His book stirred up controversy
Idea called “Evolution by natural
selection”
Darwin Video
Darwin’s Book Explained Natural
Selection
Natural selection- organisms best suited to
their environment survive and reproduce
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Darwin’s proposed mechanism of evolution
Survival depends on the particular environmental
conditions a species finds itself in—nature!
If the environment changes, so do the populations
that live there
Adaptation- using inherited genetic
characteristics to increase chance of survival
in new environment
Natural Selection and Salamanders
Natural Selection
Three conditions necessary for natural
selection to occur:
– Genetic variation: Individuals within a population
must be genetically different
****Random mutations are the raw material for
evolution to occur!!!!!!!
– Overproduction of offspring: More organisms are
born than can survive
– Differential reproduction: Certain traits enable
individuals to survive and have more offspring
than others
Result of Natural Selection
- Genes that help a population survive in their
conditions stay in their gene pool, while
“unfavorable” genes gradually decrease in
frequency
- This causes changes in the genetics of
populations EVOLUTION!!!!!
- As new mutations accumulate over a long time,
the new populations no longer can mate with the
original they started as. New species have
formed!
- Natural Selection –Crash Course
Whose idea for
evolution is this?
Evolution: How does
is really work ?
Review
Most important concepts ?
Inherited Variation
• Every species has variation in the traits that
it expresses.
• These traits are inherited.
• Mutations can occur.
• Ex: Peppered Moth
Artificial Selection
• When humans select for the traits that they
consider the most important.
• They will breed for these traits.
• Ex: Cats, dogs, crops etc.
Struggle for
Existence
Survival of the
fittest
Descent with
Modification
Evolution
through Sexual
Selection
• Each member of a species competes against the other for food, living space and
other life necessities
• Creates: faster predators, camouflage, better protection adaptations (quills)
• How well an organism is suited for their environment.
• It’s about survival and reproduction.
• Adaptations that increase survival get passed on.
• Adaptation can be anatomical/ structural or physiological process or behavior.
• All in terms of fitness in the environment.
• Natural selection over a long period of time.
• Speciation.
• Common ancestor that evolved.
• Certain characteristics were modified over a long period of time until new species were formed.
• Ex: California Salamanders and Finches on Galapagos Island
• Some characteristics or behaviours evolved purely as a means of finding a mate.
• Ex: Peacock tail or displays of dominance
What We Know Now
Evolution is a Scientific Theory
Not a hypothesis, or an
educated guess, or a
“theory” in layman’s terms
Unending amount of
evidence to support it and
NONE to reject it
Evolution is called “the unifying
principle of Biology”
Isn't Evolution JUST a Theory?
Types of Evolution
Evolution - genetic change of a population of
organisms over time descent with modification
Microevolution:
Small genetic changes of a population
Shorter amount of time
Bengal tiger simulation was
microevolution
Types of Evolution
MACROevolution-When
new species are formed
over long periods of time
– Due to tremendous
amounts of
accumulated genetic
changes in a
population
– Speciation- formation
of new species due to
accumulated
microevolution and
mutations
How does macroevolution work?
dibosirdsaur
GEOGRAPHIC ISOLATION
dibosirdsaur
dibosirdsaur
10 million years of accumulated mutations
diosirdsaur
ibosirdsaur
10 million years of accumulated mutations
diosirdsaur
iboirdsaur
10 million years of accumulated mutations
dinoirdsaur
boirdsaur
10 million years of accumulated mutations
dinordsaur
boirdsur
10 million years of accumulated mutations
dinodsaur
boirdsu
10 million years of accumulated mutations
dinodsaurs
boirds
10 million years of accumulated mutations
DINOSAURS
BIRDS
EVOLUTION
by natural selection
Microevolution
Changes
in gene frequencies
in a population
Shorter times
Examples:
Peppered moth
And Californian
Salamanders
Why is Evolution Controversial ?
MACROevolution
Accumulated
microevolution and
mutations to form
whole new species
Longer times
Examples:
Darwin’s finches
and
Geographical
isolation
Evidence for Evolution
Three types of evidence:
– Fossils
– Anatomical
– Molecular
Fossil Evidence
•
Fossils- any traces of dead organisms
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dinosaur bones
insects trapped in tree sap
leaf impressions
footprints
Fossil Evidence
•
Transitional species- species that have
been found in the fossil record that are
intermediates between two other species
in the evolutionary process
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Radiometric dating- a dating technique that
measures amount of radioactive material in a rock
or fossil
Relative dating- a dating technique that estimates
the date of a fossil by relating it to the age of the
layers of rock around it
Fossil Evidence
• To fossilize an
organism must be
buried by sediment
– In swamps, mud, tar
pits, or the ocean
bottom
– Hard stuff fossilizes
(bones, nails)
– Radiometric and
relative dating are
used to find out how
old the fossil is
Relative
Dating
Radiometric
Dating
Fossil Evidence
•
Fossils show:
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Life has been around for millions of years
Transitional species link older to newer species
– Darwin proposed the idea of transitional species,
though he had no evidence
– Today we have evidence:
• Archaeopteryx
• Tiktaalik Fossil, etc.
• Whales
Fossil Evidence-Archaeopteryx
WINGS
BEAK
Ted Talk- Dino Chicken
Fossil Evidence
• Whales--60 million years of
evolution
– Descended from 4-legged wolflike animals that were also
ancestors to cows and horses
– Fossil evidence shows slow loss
of legs
– Pelvis still remains with no rear
legs
Anatomical Evidence
• Anatomical evidence- evidence for evolution
which is based on similarities and differences
between the physical structures of different
species.
• What can we tell about the relatedness of the
three species below?
Anatomical Evidence
• Homologous structures-Bone structure the
same (homo) but not function
–Bird wing, dolphin fin, and a human arm
– The function these structures is not the
same!
–Shows that these species shared a common
ancestor
–Similar structures with different functions
resulted from accumulated mutations and
modifications
Homologous Structures
Anatomical Evidence
• Analogous structures- Bone structure different but
serve the same function
–Function = flight
–Butterfly wing, bat wing, fly wing
–These structures, although they have the
same function, are not built the same!
–Show different species evolved structures
with similar function through different
evolutionary pathways
–EVOLUTION IS NOT RANDOM!
Anatomical Evidence
Anatomical Evidence
•
Vestigial structuresstructures that no
longer serve a function
• These structures are
the remnants of an
evolutionary past and
show common anatomy
with other species
Molecular Evidence
•
Molecular evidenceevidence concerning the
comparison of DNA and
protein molecules between
species
• Ultimate tools for
scientists studying
evolution
• Same genetic basis
for all organisms: A,
C, T, and G shows we
are all related
Molecular Evidence
• Mutations and sexual
reproduction are a cause of
variation in a species’ DNA
• DNAmRNAprotein
– Transcription- copying the DNA
code into mRNA
– Translation- converting the code
of mRNA into a long chain of
amino acidsprotein
– Differences in DNA are seen in
differences in protein and
therefore, traits
Molecular Evidence
• Species with more similar DNA
are more closely related on the
evolutionary tree
– Less time since they
split to accumulate
mutations (and,
therefore, differences)
– Common ancestorany species in the
past from which two
or more related
species has evolved
– Evidence for Evolution
= speciation event
= mutation
Doc Zone
• The Disappearing Male
• What does this say about the next step in
our evolution ?