Transcript Evidence for Evolution

Evolution
Diversity of Life
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Why did you pick the candy you did?
What are some reasons you didn’t
pick certain candy?
What candy “survived”
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Natural Selection
Process by which populations change
in response to their environment as
individuals better adapted to the
environment leave more offspring
than those individuals not suited to
the environment
 Adaptations are the changes that
occur in a species that results in
organisms being better suited to its
environment
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Natural Selection
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All species have genetic variation.
The environment presents many
different challenges to an individuals
ability to reproduce.
Organisms tend to produce more
offspring than their enviornment can
support
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Natural Selection
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Individuals within a population that
are better able to cope with the
challenges of their environment tend
to leave more offspring than those
less suited to the environment.
The traits of individuals best suited
to a particular environment tend to
increase in a population over time.
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Evolution
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Change in the genetic makeup of a
population or species over time
Four major points that support the
theory of Evolution
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Theory of Evolution
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Variation exists within the genes of
every population or species (result of
random mutation)
In particular environment, some
individuals of a population or species
are better suited to survive (as a
result of variation) and have more
offspring
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Evolution
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Over time, the traits that make
certain individuals of a population
able to survive and reproduce tend to
spread in the population.
There is clear proof from fossils and
many other sources that living species
evolved from organisms that are
extinct.
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Evolution
“Nothing in
biology makes
sense EXCEPT
in the light of
evolution.”
Theodosius
Dobzhansky
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Charles Darwin in later years
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History of
Evolutionary
Thought
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Charles Darwin the
Naturalist
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Voyage of the Beagle
Charles Darwin
 Born Feb. 12, 1809
 Joined Crew of
HMS Beagle, 1831
 Naturalist
 5 Year Voyage
around world
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HMS Beagle’s Voyage
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Evidence for Evolution – The Fossil Record
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The Galapagos Islands
Finches on the islands resembled a
mainland finch from South American
 More types of finches appeared on
the islands where the available food
was different (seeds, nuts, berries,
insects…)
 Finches had different types of beaks
adapted to their type of food
gathering
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Lamarck’s Theory of
Evolution
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Jean-Baptiste Lamarck,
1809
One Of First Scientists
To Understand That
Change Occurs Over Time
Stated that Changes Are
Adaptations To
Environment acquired in
an organism’s lifetime
Said acquired changes
were passed to offspring
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Lamarck’s Theory of
Evolution
Idea called Law
of Use and
Disuse
 If a body part
were used, it
got stronger
 If body part
NOT used, it
deteriorated
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Lamarck’s Theory of
Evolution
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Inheritance Of Acquired Traits
– Traits Acquired During Ones Lifetime
Would Be Passed To Offspring
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Clipped ears of dogs could be passed to offspring!
Darwin’s Conclusion
• Production of more
individuals than can be
supported by the
environment leads to a
struggle for existence
among individuals
• Only a fraction of
offspring survive each
generation
• Survival of the Fittest
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The Struggle for Existence
 Malthus’
Influence and Key
Associations-
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Darwin’s key association was that
individuals that have physical or
behavioral traits that better suit their
environment are more likely to survive
and reproduce than those that do not
have such traits.
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Darwin’s Conclusion
• Individuals who
inherit
characteristics most
fit for their
environment are
likely to leave more
offspring than less
fit individuals
• Called Natural
Selection
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Publication of “On The Origin
of Species”
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He Refused To Publish Until
He Received An Essay From
Alfred Wallace
– Fellow Naturalist
– Independently Developed
The Same Theory
– After 25 Years, Someone
Else Had Come To The
Same Conclusions From
Their Observations Of
Nature
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Survival of the Fittest
Key Concept
Over Time, Natural Selection
Results In Changes In The
Inherited Characteristics Of
A Population. These Changes
Increase A Species Fitness In
Its Environment
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Natural Selection
 Cannot
Be Seen Directly
 It Can Only Be Observed As
Changes In A Population Over
Many Successive Generations
– Radiation
– Fossil Record
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Major Problem in Darwin’s
Theory
• No mechanism to explain
natural selection
• How could favorable
variations be transmitted to
later generations?
• With the rediscovery of
Mendel’s work in the first
half of the 20th century,
the missing link in
evolutionary theory was
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found
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Opposition to Evolution
• The upheaval
surrounding evolution
began with Darwin’s
publication of On the
Origin of Species By
Means of Natural
Selection
• The debate continues
nearly 150 years later
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Isolation
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Process by which two
populations of the same
species cannot breed
with one another.
Geographically species
populations become
separated, and change
independently over
time.
At some point they are
so different they can
no longer breed and are
two distinct species.
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Theory of Evolution
Today
Supporting Evidence
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Evidence of Evolution
Key Concept
Darwin Argued That Living Things
Have Been Evolving On Earth For
Millions of Years. Evidence For This
Process Could Be Found In:
– The Fossil Record
– Homologous Structures of Living
Organisms
– Protein and DNA similarities
– Similarities In Early Development
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Fossil Record
Provide the most direct evidence
that evolution has taken place
 Fossils In Different Layers of Rock
(sedimentary Rock Strata) Showed
Evidence Of Gradual Change Over
Time
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Homologous Body
Structures
 Scientists
Noticed Animals With
Backbones (Vertebrates) Had
Similar Bone Structure
 Similar structures in different
organisms are from a
 Common ancestor
»Arms, Wings, Legs, Flippers
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Homologous Structures
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Similarities in DNA Sequence
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Cytochrome c is a protein that is involved in
cellular respiration in all eukaryotic organisms.
Human cytochrome c contains 104 amino acids.
The following table compares human cytochrome
c with cytochrome c from a number of other
organisms.
Organism
Number of cytochrome c
amino acids that differ
from human cytochrome c
amino acids
Chickens
18
Chimpanzees
0
Dogs
13
Rattlesnakes
20
Rhesus Monkey
1
Yeasts
56
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Similarities In Early
Development
Embryonic Structures Of Different
Species Show Significant
Similarities
 Embryo – 3 structures
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– Tail
– Buds that become limbs
– Pharyngeal pouches
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Human Fetus – 5 weeks
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Chicken
Turtle
Rat
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Gradualism vs punctuated
equilibrium
Gradualism – gradual change over a
long period of time lead to species
formation
 Punctuated equilibrium- periods of
rapid change in species are separated
by periods of little or no change
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Industrial Melanism
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Industrial melanism
http://www.youtube.com/watch?v=Ly
RA807djLc
 Hypothesis- dark peppered moths are
camouflaged on the soot-darkened
bark and so are not eaten by the
birds. Light moths, on the other hand
would stand out against the dark
background and would be preyed upon.
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