1. Chapter 22 Descent with Modification
A Darwinian View of Life

2. How did the diversity of life originate?
Through the process of Evolution

3. Evolution
The processes that have transformed life on earth from its beginnings to today's diversity.
Evolution is the most pervasive principle in biology.

4. Theory vs theory Theory theory
Hypothesis supported repeatedly by data.
Makes testable predictions
Layperson’s definition.
Confused with hypothesis in Science

5. Examples of Theory Cell Theory Big Bang Theory Atomic Theory
Theory of Gravity
Theory of Evolution

6. Evolution Has itself "evolved" or changed over time.
Illustrates “Science as a Process”

7. Overview: Endless Forms Most Beautiful
A new era of biology began in 1859 when Charles Darwin published The Origin of Species
The Origin of Species focused biologists’ attention on the great diversity of organisms
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

8. Darwin noted that current species are descendants of ancestral species
Evolution can be defined by Darwin’s phrase descent with modification
Evolution can be viewed as both a pattern and a process
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

9. Charles Darwin
The Darwinian revolution challenged traditional views of a young Earth inhabited by unchanging species
To understand why Darwin’s ideas were revolutionary, we must examine them in relation to other Western ideas about Earth and its life
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

10. Pre-Darwinian Views 1. Greeks 2. Fixed Species 3. Catastophism
4. Hutton and Lyell
5. Lamarck

11. Pre-Darwinian Views 1. Greeks 2. Fixed Species 3. Catastophism
4. Hutton and Lyell
5. Lamarck

12. Greek Philosophers
1. Plato - Organisms are already perfectly adapted to their environments.
2. Aristotle - Organisms arranged on a “scale of life” from simple to complex.

13. Result
No evolution.
Life is already perfect and doesn’t need to change.
All the rungs on life's "ladder" are already occupied.

14. Pre-Darwinian Views 2. Fixed Species 3. Catastophism
1. Greeks
2. Fixed Species
3. Catastophism
4. Hutton and Lyell
5. Lamarck

15. Fixed Species Concept
The creator had designed each and every species for a particular purpose.
Carolus Linnaeus interpreted organismal adaptations as evidence that the Creator had designed each species for a specific purpose
Linnaeus was the founder of taxonomy, the branch of biology concerned with classifying organisms

16. Result
No evolution.
Created the viewpoint that all species could be identified and named (Taxonomy).
A major factor in the Linnaeus classification system.

17. Pre-Darwinian Views 3. Catastophism 4. Hutton and Lyell 5. Lamarck
1. Greeks
2. Fixed Species
3. Catastophism
4. Hutton and Lyell
5. Lamarck

18. Catastrophism Georges Cuvier (1769-1832).
Attempted to relate fossils to current life.

19. Paleontology, the study of fossils, was largely developed by French scientist Georges Cuvier
Cuvier advocated catastrophism, speculating that each boundary between strata represents a catastrophe
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

20. Catastrophism
Fossils were the remains of species lost due to catastrophe.
No new species originated; species could only be lost over time.
Result - No evolution.

21. Pre-Darwinian Views 4. Hutton and Lyell 5. Lamarck 1. Greeks
2. Fixed Species
3. Catastophism
4. Hutton and Lyell
5. Lamarck

22. This view strongly influenced Darwin’s thinking
Geologists James Hutton and Charles Lyell perceived that changes in Earth’s surface can result from slow continuous actions still operating today
Lyell’s principle of uniformitarianism states that the mechanisms of change are constant over time
This view strongly influenced Darwin’s thinking
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

23. James Hutton 1795 - Gradualism
Profound change is the cumulative product of slow, but continuous processes.

24. Result
Changes on the earth were gradual, not catastrophic.

26. The study of fossils helped to lay the groundwork for Darwin’s ideas
Fossils are remains or traces of organisms from the past, usually found in sedimentary rock, which appears in layers or strata

27. Layers of deposited sediment Younger stratum with more recent fossils
Fig. 22-3
Layers of deposited
sediment
Younger stratum
with more recent
fossils
Figure 22.3 Formation of sedimentary strata with fossils
Older stratum
with older fossils

28. Charles Lyell
Incorporated Hutton’s gradualism into a theory called Uniformitarianism.

29. Uniformitarianism
Geological processes have operated at the same rate over the Earth’s history.
Result - The Earth must be VERY old. (much older than 6000 years of the fixed species concept).
Idea that slow and subtle processes can cause substantial change.

31. Pre-Darwinian Views 5. Lamarck 1. Greeks 2. Fixed Species
3. Catastophism
4. Hutton and Lyell
5. Lamarck

32. Jean Baptiste Lamarck Published theory in 1809.
Theory - Life changed from simple to complex over time.

33. Lamark Fossils were the remains of past life forms.
Evolution did occur.

34. Lamarck’s Hypothesis of Evolution
Lamarck hypothesized that species evolve through use and disuse of body parts and the inheritance of acquired characteristics
The mechanisms he proposed are unsupported by evidence
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

35. Lamark Mechanisms 1. Use and Disuse - 2. Acquired Characteristics
Body parts used to survive become larger and stronger.
Body parts not used to survive deteriorate.
2. Acquired Characteristics
Modifications acquired by use/disuse were passed on to offspring.

36. Problem No knowledge of genetics.
Acquired traits are not transmitted offspring.

37. Lamarck’s Credits
Did suggest correctly the role of fossils in evolution.
Did suggest that adaptation to the environment is a primary product of evolution.

38. Another important figure

39. Thomas Malthus Essay on human population growth in 1798.
Disease, famine, homelessness, and war are inescapable because human populations grow faster than food supplies.
Darwin read Malthus.

40. Charles Darwin and Natural Selection
Next time….
Charles Darwin and Natural Selection