1. Evolution
Evidence and Theory

2. The Fossil Record
 Fossil is a trace of a long-dead organism.
 Found in sedimentary rock.
 Over long periods of time, hard minerals
replace the tissue of the organism leaving
rocklike structure behind.
 Robert Hooke (remember him) was one of
the first scientists to study fossils. Published
conclusion that fossils are the remains of
plants and animals (1668)

4. Distribution of fossils
 Law of Superpostion: successive layers of
rock or soil were deposited on top of one
another by wind or water.
 The lowest stratum (layer) in a cross
section of Earth is the oldest.
 The top stratum is the youngest
(deposited most recently).
 Fossils found in the same layer are close to
the same age.

6. Succession of Forms
 Fossil-bearing strata show that species of
organisms appeared, existed for a while,
and then disappeared (became extinct).
 Newer species arose.
 Fossil record indicates several mass
extinctions (evidence indicates we are in
the midst of the 6th mass extinction).
 http://news.discovery.com/videos/why-
tell-me-why-mass-extinction.html

7. Biogeograhy
 Is the study of the geographical
distribution of fossils and of living
organisms.
 Comparison of fossil types with types of
living organisms in the same geographic
area shows that new organisms arise in
areas where similar forms previously lived.

9. Theories of Evolution

10. Lamarck’s Explanation
 1744-1829
 Similar species descended from a common
(same) ancestor.
 Living species were descended from similar
extinct species evident in fossil record.
 Lamarck was the first to clearly state that
types of organisms change over time and
that the new types are modified descendants
of older types.

11. Lamarck: How species
change.
 Acquired traits were passed to offspring.
 Acquired traits are NOT determined by
genes, it arises during an organism’s lifetime
as a result of the organism’s experience or
behavior.
 Observation: Long neck on giraffes.
 Hypothesis: long neck resulted from repeated
stretching to reach food higher and higher in
trees. (acquired trait through habit).

13. Alfred Wallace and
Charles Darwin
 Independently proposed species are
modified by Natural Selection.
 Darwin is now remembered for it and
Wallace forgotten because of Darwin’s
book The Origin of Species published in
1859.

14. Natural Selection
 Organisms best suited to their
environment (high fitness) REPRODUCE
more successfully passing on their
characteristics (through GENES/DNA).
 Over generations, the proportion of
organisms with the favorable traits
increase in a POPULATION.
 Individuals DO NOT evolve, populations
do.

15. Charles Darwin
 Attended medical school then enrolled to
study for the clergy.
 1831 sailed on the H.M.S. Beagle as the
naturalist on a 5-year mapping and
collecting expedition to South America
and the South Pacific.
 Darwin was responsible for collecting
specimens and keeping careful records of
his observations.

16. Voyage of the Beagle
 Darwin collected many types of fossils,
specimens of organisms and observed
thousands of species.
 Galapagos Islands
 http://science.discovery.com/videos/100-
greatest-discoveries-shorts-natural-
selection.html

17. Darwin’s Finches
 Collected 13 similar but separate species.
 Each finch species has a distinctive bill that is
specialized for a particular food source.
 Similarities implied the finches shared a recent
common ancestor.
 Offspring of original finches has been
adapting to different environments and food
sources.
 Over many millions of years, many large
differences could accumulate between
species.

18. Darwin’s Finches

19. Darwin’s Theories
 Descent with modification: the newer forms
appearing in the fossil record are actually the
modified descendants of older species.
 Modification by Natural selection:
environment affects individual organisms in a
population. Those best suited (best fit)
survive, pass on the beneficial traits. Those
with favorable traits have adaptive
advantage. Selection conditions change as
the demands of the environment changes.

20. Evolution in Process
 Evolution is a continuous process.
 Genotypic and phenotypic evidence in
modern organisms indicates that
evolution has occurred.

21. Evidence of Evolution
 Homologous and Analogous structures.
 Vestigial Structures
 Similarities in Embryology
 Similarities in Macromolecules.

22. Homologous Structures
 Similarfeatures that originated in a recent
shared (common) ancestor.
 Same structure, may have different
function.

23. Analogous Structures
 Same function, different structure
 No recent shared (common) ancestor.

24. Similar Structure = Similar
Genes = Evolutionarily related!

25. Vestigial Structures
 Feature in an organisms that serves no
current function (useless).
 Feature was useful to an ancestor.

26. Similarities in Embryology
 Early stages of different vertebrate
embryos are strikingly similar to each
other.
 “Embryological development repeats
evolutionary history.
 Similarities are evidence that vertebrates
share a common ancestry.
 http://www.dnatube.com/video/4207/Wh
at-Can-Embryos-Tell-Us-About-Evolution

28. Similarities in Macromolecules
 What Darwin Didn’t Know: Similar traits
because of similar DNA!
 DNA > transcription> RNA> translation >
proteins (chains of amino acids)
 Similar proteins = similar DNA=shared
ancestor
 The more similar the proteins in different
species, the more closely related the
species are.

29. Patterns of Evolution
 There are several ways that species
(populations) can change to adapt to
their habitats.
 The pattern and speed of evolutionary
change result from the changing
requirements of the environment.
 Changes place new selective pressures
on the population.

30. Coevolution: change in two
species in close association
with each other.

32. video
 http://video.nationalgeographic.com/vid
eo/player/animals/bugs-animals/ants-
and-termites/ant_acaciatree.html

33. Convergent Evolution
 Organisms that appear very similar (sharks
and porpoise) but are not closely related
at all.
 Environment selects similar phenotypes,
even though the ancestral types are very
different.
 Analogous structures (fins) to perform
similar functions in similar environment.

35. Divergent Evolution
2 or more related populations or species
become more dissimilar (different).
 Result of differing habitats (environment).
 Can result in new species.
 Adaptive Radiation - many related
species evolve from a single ancestral
species. (Darwin’s finches)
 Artificial Selection – humans select for
traits (breeding).

37. Fun Stuff
 http://www.pbs.org/wgbh/nova/evolutio
n/guess-embryo.html
 http://www.pbs.org/wgbh/nova/evolutio
n/zoo-you.html