1. Understanding the Diversity of Life – Part 1
Evolution
Understanding the
Diversity of Life – Part 1

2. Evolution
“Nothing in biology makes sense EXCEPT in the light of evolution.” Theodosius Dobzhansky
Charles Darwin in later years

3. History of Evolutionary Theory

4. Early Ideas about Earth’s Organisms
Aristotle believed species were fixed creations arranged by their complexity

5. Early Ideas about Earth’s Organisms
Carolus Linnaeus
1st to group similar organisms and assign them Latin names
Two word name (Genus species)
Known as Binomial nomenclature

6. Early Ideas about Earth’s Organisms
Georges Cuvier
Some species’ fossil records disappeared in more recent layers
Stated that species disappear due to a catastrophic event of the earth’s crust

7. Early Ideas about Earth’s Organisms
James Hutton & Charles Lyell
Stated that various geological forces constantly changed the planet
Changes in Earth’s crust were due to slow continuous processes
Idea Known as Gradualism or Uniformitarianism

8. Early Ideas about Earth’s Organisms
Hutton & Lyell, cont.
Geological processes moved at uniform rates; building & wearing down Earth’s crust
Proposed that the Earth was millions of years instead of a few thousand years old

9. Early Ideas about Earth’s Organisms
Reverend Thomas Malthus
Studied macroeconomics
Stated that populations could not grow indefinitely
This growth would be stopped by:
Disease
Famine
War

10. Lamarck’s Theory of Evolution
Jean-Baptiste Lamarck
One of first scientists to understand that organisms change over time
Put forth an idea called Inheritance of Acquired Characteristics through Law of Use and Disuse

11. Lamarck’s Theory of Evolution
Proposed that by selective use or disuse of organs, organisms acquired or lost certain traits during their lifetime
Examples:
blacksmiths & their sons (muscular arms)
giraffe’s necks longer (from stretching)
These traits could then be passed on to their offspring
Over time this would lead to new species

13. Lamarck’s Mistakes Inheritance Of Acquired Traits
Traits Acquired During Ones Lifetime Would Be Passed To Offspring
If true, clipped ears would pass to offspring!

14. Lamarck’s Mistakes
Lamarck did NOT know how traits were inherited (traits are passed through genes)
Genes are NOT changed by activities in the life of an organism
Change occurs through mutations of genes
These mutations occur before the organism is born

15. Charles Darwin the Naturalist

16. Charles Darwin
Born Feb. 12, 1809
A naturalist
Collector/identifier of plant and animal specimens
Formed his ideas about evolution sailing on the HMS Beagle for the Galapagos Island in 1831

17. The Galapagos Islands Small group of islands 1000 km west of Ecuador
Very different climates and geography on each island
Animals on each of the islands similar but unique

18. The Galapagos Islands Islands all formed by action of volcanoes
Island species varied from mainland species & from island-to-island species
Each island had long or short neck tortoises

19. The Galapagos Islands
Finches on the islands resembled a mainland finch
Different types of finches appeared on the islands where the available food was different (seeds, nuts, berries, insects…)
Finches had beaks adapted to their type of food gathering

21. The Struggle for Existence
Darwin’s Observations and Conclusions

22. Darwin’s Observations
Patterns of Diversity
Unique adaptations in organisms
Species not evenly distributed
Examples:
Australia: kangaroos
South America: llamas
Africa: elephants

23. Darwin’s Observations
Darwin collected living organisms and fossils on his voyage
Took these back to England to study
This species NO longer existed. What had happened to them?

24. Giant
Ground
Sloth

25. Glyptodon – Ancestor of Modern Armadillo

26. Darwin’s Observations
Unlimited resources will allow organisms increase exponentially, generation to generation
In nature, populations tend to remain stable in size
Environmental resources are what limits population size

27. Darwin’s Observations
Individuals of a population vary in their characteristics with no two individuals being exactly alike.
Much of this variation between individuals is inheritable.

28. Darwin’s Conclusions
Production of more individuals than can be supported by the environment leads to a struggle for existence
Only a fraction of offspring survive each generation
He called this “Survival of the Fittest”

29. Darwin’s Conclusions
Individuals who inherit characteristics most fit for their environment are likely to leave more offspring than less fit individuals
He called this “Natural Selection”

30. Ideas that Shaped Darwin’s Thinking

31. Ideas that Shaped Darwin’s Thinking
Hutton & Lyell
Expanded Earth’s age from 6000 to billions of years
Explained geological processes that shaped the earth
Helped Darwin understand the presence of sea shells in the Andes mountains at 12,000+ feet

32. Ideas that Shaped Darwin’s Thinking
Malthus’ Influence
Babies are born faster than people die
Total population size limited by resources such as the food supply
High birth rates & limited resources would force life & death competition
Each Species Struggles For:
Food
Living Space
Mates

33. Darwin’s Theory of Evolution
Organisms Change Over Time

34. Evolution: Defined
Evolution is the slow , gradual change in the alleles of a population over time

35. Darwin’s Theory of Evolution
The unequal ability of individuals to survive and reproduce leads to a gradual change in a population, with favorable characteristics accumulating over generations (Natural Selection)
This creates new species

36. Darwin’s Theory of Evolution
Descent with Modification:
Organisms descended from common ancestors
Organisms change with time, diverging from a common form

37. Darwin’s Theory of Evolution
Natural Selection:
Driving force for evolution
During the struggle for resources, strongest survive & reproduce
Idea that at least some of the beneficial differences between individuals are inheritable .

38. Publication of: “On The Origin of Species”
Upon his return To England, Darwin spent 25 years developing his observations into the Theory of Evolution
He hesitated to publish because:
1. He knew that his theory would be extremely controversial and would be attacked
2. His theory challenged established religious & scientific beliefs; particularly about the Creation of Man

39. “O’ no you didn’t! This was my Idea!” - Darwin
Alfred Russel Wallace
Fellow naturalist
Sent an essay of his work to Darwin to review
Had independently come to the conclusion that species changed over time because of their struggle for existence
When Darwin read Wallace’s essay, he knew he had to publish his findings

40. Publication of: “On The Origin of Species”
Darwin presented Wallace’s essay & some of his work at a conference in July of 1858
Then he started work on his book “Origin of Species” which was published in 1859
Spent the rest of his life refining his ideas about evolution
Darwin died in 1882, the father of 10 children; 7 survived to adulthood