1. What Best Explains Diversity?
I. Special Creation
II. Evolution
Aristotle to Darwin
~350 BC to 1800s
Darwin to Present
(A) Each organism originated independently.
(B) Since the time of creation, each organism
has remained the same.
(C) All organisms were created recently.
(A) All organisms originated from common ancestors.
(B) Organisms have and continue to change over time.
(C) Evolution of organisms began 3.7 billion years ago

2. For a more details concerning the History of Evolutionary Thought:
For information about the Evolution/Creationist Controversy:
National Center for Science Education:

3. The Important Players that Influenced Charles Darwin
John Ray ( ) : Practiced “Natural Theology”; he thought that god’s creation can best be understood and appreciated through study of nature.
Carl Linnaeus ( ): Father of taxonomy; authored Systeme Naturae.
Also practiced natural theology.
Georges-Louis Leclerc, Comte de Buffon ( ) :
1) Questioned the idea of Special Creation. Wrote about the similarity
of man and apes in Historie Naturelle.
2) Questioned the idea of a young earth in Les Epoques of Nature.
Erasmus Darwin ( ): Great intellectual of 18th century
Organic life beneath the shoreless waves
Was born and nurs'd in ocean's pearly caves;
First forms minute, unseen by spheric glass,
Move on the mud, or pierce the watery mass;
These, as successive generations bloom,
New powers acquire and larger limbs assume;
Whence countless groups of vegetation spring,
And breathing realms of fin and feet and wing.
The Temple of Nature

4. Thought that only an Intelligent Designer could have made life.
William Paley ( ): wrote: Natural Theology: or, Evidences of the
Existence and Attributes of the Deity, Collected from the
Appearances of Nature.
. . . when we come to inspect the watch, we perceive. . . that its several parts are framed and put together for a purpose, e.g. that they are so formed and adjusted as to produce motion, and that motion so regulated as to point out the hour of the day; that if the different parts had been differently shaped from what they are, or placed after any other manner or in any other order than that in which they are placed, either no motion at all would have been carried on in the machine, or none which would have answered the use that is now served by it the inference we think is inevitable, that the watch must have had a maker -- that there must have existed, at some time and at some place or other, an artificer or artificers who formed it for the purpose which we find it actually to answer, who comprehended its construction and designed its use.
Thought that only an Intelligent Designer could have made life.

5. Age of Comparative Anatomy
Georges Cuvier ( ): Founded vertebrate paleontology and developed
the comparative method of organismal biology. Established extinction as fact.
Geoffroy St. Hilaire ( ): Geoffroy spent much time drawing up
rules for deciding when structures in two different organisms were
variants of the same type.
One of his more infamous theories was that the segmented external skeleton
and jointed legs of insects were equivalent to the internal vertebrae and ribs of
vertebrates; insects literally live inside their own vertebrae and walk on their
ribs. He is said to have stated, "There is, philosophically speaking, only
a single animal."
Richard Owen ( ): Defined homology in 1843 as "the same organ
in different animals under every variety of form and function."

6. Jean-Baptiste de Lamarck (1744-1829) First Theory of Evolution
Transformational Evolution
Humans
Mammals
Scale Of
Nature
Amphibians
Fish
Insects
Jellyfish
Zooplankton
Pond Scum
Time

7. Lamarck :
Believed in inheritance of acquired characteristics (acquired during life)
Change
Inherited by
Offspring
Change
Inherited by
Offspring
Parents
Parents
Change
During
Lifetime
Parents
Change
During
Lifetime
Parents
Change
During
Lifetime

8. Inheritance of Acquired
Grows up
Among Short
Trees
Inheritance of Acquired
Characteristics
Two Sibling
Giraffe’s
Grows up
Among Tall
Trees:
Longer neck

9. Importance of Lamarck’s Theory
Recognized that life forms were connected
Recognized that there is variation in traits
Recognized that evolution requires time (Earth is Old).
Recognized that inheritance is an important aspect of adaptation

10. Darwin (1809-1882) Two Major Ideas:
“On the Origins by Means of Natural Selection, or the
Preservation of Favoured Races in the Struggle of Life”
Two Major Ideas:
Common Descent
All living and extinct species descended from one or a few common ancestors.
aka: Macroevolution
Adaptation occurs by Natural Selection
The characteristics of organisms change through time as a result of natural selection.
aka: Microevolution

11. The only figure in “On the Origins….”

12. Darwin’s Idea of Common Decent Implies:
(1) Branching evolution
(2) That species accumulate differences over time
Genus 1
Genus 2
Species 1
Species 2
Species 5
Species 1
Species 2
Species 3
Species 4
Extinction
Differences
Accumulate
Over Time

13. Systematists Study Differences Among Species to Reconstruct Phylogeny
(i.e. Phylogeny = Genealogy of Species)

14. Evolution by Natural Selection

15. What is adaptation?
Process of genetic change whereby individuals of a population become better suited to their environment

17. Evolution of developmental timing: metamorphosis vs paedomorphosis
ephemeral pond
Metamorphosis
Although some species are constrained to undergo a metamorphosis, variation in metamorphic timing is often observed at the population and species levels. This suggests that selection for metamorphic timing may be important in adapting populations to local environmental conditions. Generally speaking, the length of the larval period is correlated with the relative permanence and predictability of the aquatic larval habitat. More permanent bodies of water can support longer larval periods. The point we want to make is that there is potential for developmental timing evolution within the constraint of a biphasic life cycle, and this represents a process whereby tiger salamanders adapt to habitat variability. In comparison to continuous variation in metamorphic timing, tiger salamanders also adapt to habitat variability by expressing an alternate paedomorphic life cycle mode. Paedomorphic salamanders fail to undergo a metamorphosis and therefore retain the larval features of the ancestral condition. Paedomorphosis is an adaptation to relatively permanent aquatic habitats. In terms of developmental timing, there is a major change, a permanent delay in the onset timing of metamorphosis, and this results in a discrete form of adaptive phenotypic variation.
4:30
Time

18. Adaptation to Permanent Pond
Hatching
no metamorphosis
Paedomorphosis

19. Evolution After Darwin
Most folks accepted idea of common descent, but not natural selection.
Competing theories were proposed:
Orthogenesis: variation in the characteristics of organisms
is channeled in pre-determined directions.
Macromutation: downplayed the importance of continuous
variation and stressed discrete variation. Thought evolution
only depended upon mutation rate.

20. The Modern Synthesis (1930’s - 40’s)
Synthesis of ideas/concepts among geneticists, natural
historians, and evolutionary biologists that modern
evolutionary biology is built upon.
Emphasized the co-action of random mutation, selection,
genetic drift, and gene flow in microevolution.
Emphasized that these evolutionary processes were sufficient
to account for macroevolutionary trends.