1. The Theory of Evolution
Chapter 16
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2. What is Evolution? Change over time
Fossil evidence shows that living things have not always been the same as today

3. History of the theory… James Hutton (1785)
Earth formed very slowly, earth is old
Forces beneath the earth’s surface act to form mountains, rocks, and valleys

4. History of the theory… Thomas Malthus (1798)
Predicted that the human population would grow faster and larger than the space and food supplies will allow
Predicted there would be a great struggle for survival, leading to wars and famine

5. History of the theory… Jean-Baptiste de Lamarck (1809)
Was the first to propose a mechanism for evolution
Hypothesized that the environment influenced the development of traits
Inheritance of acquired traits

6. Lamarck’s Theory Acquired traits are developed as needed Example:
long neck of giraffe
Fins and tail of a dolphin

7. Lamarck’s Theory-problems…
Acquired traits are passed on to offspring
We know that only traits that are controlled by genes can be passed down to future generations
A trait that is not needed will be lost
We know that an organism cannot “lose” a trait it had at the start of its life, because traits are controlled by its genes

8. History of the theory… Charles Lyell
His book, Principles of Geology, explained that earth continues to change just as it has for millions of years
And processes that have shaped (and continue to shape) the earth are very slow

9. History of the theory… Charles Darwin (1832)
Set sail as ship’s naturalist on the HMS Beagle
Read the works of Malthus, Hutton, and Lyell while sailing around the world
Collected evidence that would be used to support his developing theory

10. History of the theory… Alfred Wallace (1858)
Wrote to Darwin speculating on evolution by natural selection

11. Darwin’s Theory On the Origin of Species (1859)
Individuals differ and some of the variation is inheritable
Many more offspring are born than can survive
There is competition for resources
Each individual has advantages and disadvantages in the struggle to survive
Those most adapted to the environment will survive and pass their traits on

12. Evidence to support Darwin’s Theory
1. Fossil record

13. Evidence to support Darwin’s Theory
2. Natural Selection Changes Populations
Darwin collected a closely related group of 13 finch species in the Galapagos Islands.
All similar except for beak characteristics.
Beak correspondence suggested to Darwin that they were shaped by evolution.
Nature of available food supply.
Example:
Beaks of Darwin’s Finches

14. Evidence to support Darwin’s Theory
3. Homology in the Anatomical Record
Structures with different appearances and functions that all derived from a common ancestor.

15. Evidence to support Darwin’s Theory
3. Emryological Development
Different organisms exhibit similar embryological forms.

16. Evidence to support Darwin’s Theory
4. The Molecular Record (DNA, RNA, proteins) Distantly related organisms are expected to accumulate a greater number of evolutionary differences than closely related species.

17. Natural selection Peppered Moths and Industrialized Melanism
Until the mid-nineteenth century, Peppered Moths, Biston betularia, had predominately light-colored wings.
Industrial smog helped turn lichens on tree trunks dark.
Subsequently, dark individuals became predominant.
Predators see them!
Second half of the twentieth century saw widespread implementation of pollution controls, thus trends reversed and light colored moths again dominated.
But, caution must be taken, as the selective agent could be some factor other than wing coloration.

18. When two groups of the same species are separated, changes may occur in each population that eventually causes them to be so different that speciation occurs
Geographic Isolation
separated by land formations such as rivers, mountains, valleys, etc
Reproductive Isolation
separated due to inability to mate with each other
Structural, mating time is different, etc
Temporal Isolation
Separated by time factors such as circadian rhythms
Behavioral Isolation
Separated by behavioral differences such as courtship dances or sounds

19. Artificial Selection
Agriculture
Kernel characteristics of corn.

20. Artificial Selection
Domestication
Breeds and characteristics of dogs.

21. The Anatomical Record
Vestigal Structures
Organs with no apparent modern function, but resemble ancestral structures.

23. The Evolution of Horses
Modern members of Equidae (horses, zebras, donkeys) are descendents of lineage originating in the Eocene Period 55 mya.
Earliest known members were species in genus Hyracotherium.
Small size
Multiple toes
Small, simple teeth.
Evolutionary change has not occurred at a constant rate.

24. Types of Evolution
Convergent Evolution - Selection that favors changes making two or more groups more similar.
Similar solutions to similar problems.
Marsupial-Placental Convergence
Divergent Evolution - Selection that favors changes making two or more groups less similar.
Exposure to different selective pressures.

25. Weaknesses of the theory…
Cannot explain how the first life began
First single cell
First multi-cellular organism

26. Weaknesses of the theory…
Relies on random mutation as the explanation for change
Most mutations are harmful

27. Weaknesses of the theory…
A “missing link” is not known for any two species
All species seem to have come into being independently of any other

28. More like a lizard or a bird?
Theory changes as more evidence is found
Dinosaur theory

29. Darwin’s Critics
Evolution is not solidly demonstrated.
There are no fossil intermediates.
Intelligent Design.
Evolution violates Second Law of Thermodynamics.
Proteins are too improbable.
Natural Selection does not imply evolution.
The irreducible complexity argument.

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