1. Earth History: Organic Evolution

2. Ideas Around the Time of Darwin
Natural Theology: Philosophy that saw adaptations in organisms as evidence that God designed each species for a special purpose.

3. Ideas Around the Time of Darwin
Catastrophism: idea that boundaries in rock strata correspond to catastrophic events in Earth’s history.
Purposed by Georges Cuvier

4. Ideas Around the Time of Darwin:
A Shift in thinking
Paradigm Shift  a change from one way of thinking to another.
In the 18th century there was a shift from catastrophism to gradualism

5. Ideas Around the Time of Darwin
Gradualism: idea that profound change is the cumulative product of a slow continuous process
Proposed by James Hutton

6. Ideas Around the Time of Darwin
Uniformitarianism: The idea that the same laws of nature and the same Earth processes that affect the planet now, are the same ones that have always affected the planet.

7. Ideas Around the Time of Darwin
Today most geologists combine catastrophist, gradualist and uniformitarianist standpoints,
They take the view that Earth’s history is a slow, gradual story punctuated by occasional natural catastrophic events that have affected Earth and its inhabitants

8. Ideas Around the Time of Darwin
Taxonomy: branch of Biology that deals with naming and classifying organisms
Proposed by Carolus Linnaeus
For Linnaeus, grouping organisms into these taxons implied no evolutionary relationship between them. He was simply trying to reveal God's plan. Ironically, Linnaeus's scheme does indeed reflect the evolutionary kinships of a great many plants and animals.

9. Ideas Around the Time of Darwin
Lamarck’s Evolutionary Theory: During their lifetimes, organisms arquire new characteristics as a results of their interactions with the environment.
Looked at evolution as an accumulation traits that were passed to offspring
Ex: Giraffes’ necks

10. Ideas Around the Time of Darwin
It was these ideas that facilitated Darwin’s evolutionary theory
Gradualism / Catastrophism
Unifomaitrianism
Taxonomy
Lamarckian Evolution

11. Ideas Around the Time of Darwin
Darwin made two points in his book, “The Origin of Species”
Present forms of species evolved from ancestral species
The mechanism for evolution was natural selection
Over time Darwin’s theory has been modified / updated / etc.

12. Evolutionary Theory Evolution: change in a gene pool over time
Two Types
Microevolution
Macroevolution

13. Evolutionary Theory: Microevolution
Microevolution: generation to generation change in a population’s gene pool
Causes
Small population size
Isolation
Mutation
Nonrandom mating
Natural Selection

14. Evolutionary Theory: Microevolution
Small population size – in small populations big changes can result by random chance
The loss or gain of one individual has a big impact on the gene pool
Founder effect
Bottleneck effect

15. Evolutionary Theory: Microevolution
Isolation – no migration; no gene flow
Behavioral, temporal, mechanical, etc

16. Evolutionary Theory: Microevolution
Mutation – genes are altered
Most mutations are lethal
Beneficial mutations will proliferate

17. Evolutionary Theory: Microevolution

18. Evolutionary Theory: Microevolution
Nonrandom mating – certain traits are picked above others
Sexual selection
Male-male contests
Deer
Mate choice

19. Evolutionary Theory: Microevolution
Natural Selection – the environment selects certain organism for survival

20. Evolutionary Theory: Macroevolution
Macroevolution: the accumulation of small changes that eventually lead to new species
What is a species?
Classified by physical appearance
Classified by ability to interbreed and produce viable fertile offspring
Classified by DNA
Other

21. Evolutionary Theory: Macroevolution
Speciation: origin of species due to evolutionary process
Causes:
Geographical barriers
Reproductive barriers
Adaptive radiation

22. Evolutionary Theory: Macroevolution
Geographical barriers
the most common form of speciation, occurs when populations of a species become geographically isolated.
When populations become separated, gene flow between them ceases. Over time, the populations may become genetically different in response to the natural selection imposed by their different environments.

23. Evolutionary Theory: Macroevolution
Reproductive barriers
Speciation occurs when populations of a species that share the same habitat become reproductively isolated from each other.
                                                       
Different species of bowerbird construct elaborate bowers and decorate them with different colors in order to woo females. The Satin bowerbird (left) builds a channel between upright sticks, and decorates with bright blue objects, while the MacGregor’s Bowerbird (right) builds a tall tower of sticks and decorates with bits of charcoal. Evolutionary changes in mating rituals, such as bower construction, can contribute to speciation.

24. Evolutionary Theory: Macroevolution
Adaptive radiation - Adaptive radiation describes closely related species that look very different, as a result of having adapted to widely different ecological niches

25. Evolutionary Theory: Macro v. Micro
Microevolution – little debate
Actually observed
Ex: Antibiotic resistance

26. Evolutionary Theory: Macroevolution
Macroevolution – much debate
Inferred from evidence
Ex: Finches

27. Branching v. Linear Evolution
Linear Evolution  one species evolves into a new species
Branching Evolution  all present day species sharing a common ancestor
Populations of species at some point are isolated, experience different pressures from the environment , and “branch off” from the ancestral lineage

28. Branching Evolution

29. Branching v. Linear Evolution

30. Branching Evolution
It is generally thought the reason few transition fossils are found is because evolution takes place in “short” spurts
Many years of no change followed by relatively few years of rapid change.

31. Summary Vocabulary (handout) Ideas around the time of Darwin Evolution
Population / natural selection / adaptation / isolation / extinction
Ideas around the time of Darwin
Shift in thinking
Evolution
Micro
Causes
Macro
Speciation
Branching vs. Linear Evolution
Punctuated Equilibrium