1. Unit 8 Evolution

2. What is Evolution?
A well-supported scientific theory stating that
organisms change over time

3. Evidence in stone
Preserved remains of a
once living organism is
called a FOSSIL
Fossil evidence supported
that organisms changed
gradually

4. Anatomical Evidence
Comparative Anatomy: study of
similarities and differences between
organisms
Homologous Structures
Analogous Structures
Vestigial Organs

5. Homologous Structures
As similar organisms adapted to different
environments, the function of their appendages
changed. Result of descent with modification from
a common ancestor.
 A bird’s arms became
wings to flap
 A human’s arm is used
to pick-up, carry, grasp,
etc…
 A horse’s arm became
a fore-leg to run on

6. Analogous Structures
Different organisms began living in similar
environments - their appendages evolved to perform
the same function, although structurally different.
 A butterfly has wings to fly that
are made from an exoskeleton
 A sparrow has wings to fly that
have an endoskeleton
Butterfly Bird

7. Vestigial Structures
Structures which remain in organisms but have
no obvious function
Leg bones in snakes and whales
Appendix in humans **
Ear muscles in humans

8. Comparative Embryology
Examining the
embryos of
organisms
Organisms with
similar embryos are
thought to be more
closely related

9. Biochemical Evidence
(Molecular Biology)
Comparison of the amino acid sequences
 Chimp and human hemoglobin are VERY similar

10. Genetic Evidence
DNA passes on traits
When mutations occur the genes and
chromosomes can change
Humans have imposed change through
selective breeding
The higher the percentage of similarities
the closer the relationship between two
organisms

11. Jean Baptiste de Lamark
First to recognize that
organisms change
Published his hypotheses
in 1809
Theory was disproved!

12. Jean Baptiste de Lamark
3 Key Assumptions:
Desire to Change: organisms have an
inborn urge to better themselves
Law of Use and Disuse: body parts that are
used will develop; those not used will
become smaller/disappear
Inheritance of Acquired Characteristics:
organisms pass on traits acquired during
their lifetime

13. Lamark’s Giraffes

14. Charles Darwin
Credited for the theory of evolution
HMS Beagle sailed in 1831 – Galapagos Islands
Published Origin of Species in 1858

15. Darwin’s Observations
Observed tortoises, iguanas, and
finches
The islands had different climates
and vegetation
The animals were similar… but
had noticeable differences…
why?
Species vary globally
Species vary locally
Species vary over time

16. Darwin’s Theory of Natural Selection
Variations help
members of a species to
survive in a given
environment
The environment selects
the beneficial adaptation
and over time this trait
will become more
prevelant

17. Darwin’s Assumptions
Variations
 Differences among members of the same species
Overproduction
 More offspring are produced than will survive
Struggle for Existence
 Predation and competition
Survival of the Fittest (Natural Selection)
 Individuals best suited for the environment will survive,
reproduce, and pass on traits to their offspring
Descent with Modification
 Principle that species change but descend from common
ancestors

18. Darwin’s Finches

19. Fossil Formation
Water carries small Dead organisms are buried The preserved remains
rock particles to lakes by layers of sediment, may later be discovered
and seas which forms new rock and studied.

20. Fossil Record
Preserved remains of a once living
organism is called a FOSSIL
IE: amber, sedimentary rock, tar, and ice
Fossil record is incomplete

21. Relative Dating
Used to ESTIMATE
the age of fossils
Older fossils are in
deeper layers of rock

22. Patterns and Processes of Evolution
Macroevolutionary Patterns
Large-scale (more than a single species)
Occurs over long periods of time
Microevolution
Small-scale (within a single species)
Forms variations in populations
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23. Speciation – Isolating Mechanism
Species – group of organisms that interbreed to
produce fertile offspring under normal conditions –
share a common gene pool
Speciation – formation of a new species
Requires reproductive isolation – organisms
do not interbreed; gene pools become separate
Behavioral
Geographic
Temporal
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24. Patterns of Extinction
Background Extinction – “business as
usual” extinction – slow and steady
Mass Extinction – many species become
extinct over a short period of time
Causes:
Asteroid
Volcanic eruptions
Moving continents
Changing sea levels 24

25. Rates of Evolution
Gradualism – change in species is slow and
steady
Punctuated Equilibrium – long periods of
stability followed by short periods of rapid change
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26. Patterns of Macroevolution:
Adaptive Radiation
A single species evolves into many species
Often occurs when a niche opens up
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27. Patterns of Macroevolution:
Convergent
Evolution
Organisms come to
resemble one another
but evolved
differently
Source of analogous
structures!
Examples:
Dolphins and sharks
Marsupials and mammals
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28. Coevolution
Organisms with close ecological relationships
evolve together
Pollinators and flowers
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29. The Role of Genes in Evolution
In terms of genetics, evolution is the change in
the frequency of alleles in a population’s
gene pool
Natural selection leads to that change
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30. Genetic Drift
Random change in allele frequency – changes in
the gene pool of a small population due to chance
Types of Genetic Drift:
Bottleneck Effect – change in allele
frequency following dramatic reduction in
population size
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31. Genetic Drift
Founder Effect – small group colonizes a
new habitat
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32. Molecular Evolution
Molecular Clocks – use mutation rates
in DNA to estimate time two species have
been evolving independently
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33. Molecular Evolution: Hox Genes
Genes which control an organism’s basic body plan
Anterior/posterior ends
Limbs, wings
small sequence changes during embryological
development can cause large changes in adults
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34. Ancient Earth
Atmosphere was composed of gases:
CO2, N2, water vapor, CH4, H2S
No O2
Earth formed ~4.6 billion years ago

35. First Organic Molecules
1950’s Miller & Urey
reproduced
conditions of ancient
Earth
Electric sparks
simulated lightning
Amino acids began to
form

36. First Cell

37. Oxygen Accumulation in
Atmosphere

38. What is a Primate?
Binocular Vision
Developed brain
Long fingers & toes
Rotating shoulders

39. What makes us Human?
Characteristics of
the Hominine Family
Bipedal
Opposable Thumbs
Larger Brains

40. Did we evolve from chimps?

41. Hominine Evolution
Ardipithecus ramedus “Ardi”, 4.4 mya
Australopithecus afarensis “Lucy”, 3.2 mya
Homo habilis “handy man”, ≈ 2 mya
Used tools, first of the genus Homo
Homo erectus, “Java Man”, ≈ 1.6 mya
1st to use fire
Homo neanderthalensis ≈ 200,000 years ago
Homo sapien
Modern Human ≈ 100,000 years ago

42. Family Tree or Bush?