1. Ch. 17 Principles of Evolution (Darwin & Natural Selection)
Faith vs.
TINTORETTO The Creation of the Animals 1550

2. Fossils 

3. Mass Extinctions
6th Mass Extinction?
Life’s Natural History is a record of Successions & Extinctions

4. Mass extinctions

5. Darwin’s Influences
Other people’s ideas paved the path for Darwin’s thinking
competition:
struggle for survival population growth exceeds food supply
land masses change over immeasurable time

6. LaMarck Organisms adapted to their environments by acquiring traits
change in their life time
Disuse organisms lost parts because they did not use them — like the missing eyes & digestive system of the tapeworm
Perfection with Use & Need the constant use of an organ leads that organ to increase in size — like the muscles of a blacksmith or the large ears of a night-flying bat
transmit acquired characteristics to next generation
Lamarck noted how well-adapted organisms were to their environments, and believed that fossils could be understood as less perfect forms which had perished in the struggle for increasing perfection. He explained adaptation as a result of change caused by environmental pressures.

7. Charles Darwin 1809-1882 British naturalist
Proposed the idea of evolution by natural selection
Collected clear evidence to support his ideas
What did Darwin say?
What evidence supports Evolution by Natural Selection?
What impact did Evolution have on biology?

8. Voyage of the HMS Beagle
Invited to travel around the world
(22 years old!)
makes many observations of nature
main mission of the Beagle was to chart South American coastline
After graduation Darwin was recommended to be the conversation companion to Captain Robert FitzRoy, preparing the survey ship Beagle for a voyage around the world.
FitzRoy chose Darwin because of his education, his similar social class, and similar age as the captain.
Darwin noted that the plants and animals of South America were very distinct from those of Europe
Robert Fitzroy

9. Voyage of the HMS Beagle
Stopped in Galapagos Islands
500 miles off coast of Ecuador
The origin of the fauna of the Galapagos, 900 km west of the South American coast, especially puzzled Darwin.
On further study after his voyage, Darwin noted that while most of the animal species on the Galapagos lived nowhere else, they resembled species living on the South American mainland.
It seemed that the islands had been colonized by plants and animals from the mainland that had then diversified on the different islands

10. Succession of Types
Armadillos are native to the Americas, with most species found in South America.
Glyptodont fossils are also unique to South America.
Why should extinct armadillo-like species & living armadillos be found on the same continent?

11. Mylodon (left) Giant ground sloth (extinct)
Modern sloth (right)
“This wonderful relationship in the same continent between the dead and the living will…throw more light on the appearance of organic beings on our earth, and their disappearance from it, than any other class of facts.”

12. Unique Species

13. Darwin Also Found Birds…
He collected many different birds on the Galapagos Islands.
He thought he found very different kinds…
He did—22 of the 29 species of bird on the Galapagos are endemic to the island
But he also found that 14 of his specimens were types of finches
He began to question how 14 species arose when only 1 species of the finch existed on the mainland.

14. Galapagos Finches

15. Galapagos Finches *Only 11 species represented here
*Image taken from

16. Correlation of Species to Food Source
Seed eaters
Flower eaters
Insect eaters
Adaptive radiation

17. Darwin’s Finches Differences in beaks
associated with eating different foods
survival & reproduction of beneficial adaptations to foods available on islands
Warbler finch
Cactus finch
Woodpecker finch
Sharp-beaked finch
Small insectivorous
tree finch
Small ground
finch
Warbler
finch
Large
insectivorous
tree finch
Cactus
eater
Tree finches
Medium ground finch
Ground finches
Insect eaters
Seed eaters
Vegetarian
tree finch
Large ground finch
Bud eater

18. Darwin’s Finches Darwin’s conclusions
small populations of original South American finches landed on islands
variation in beaks enabled individuals to gather food successfully in the different environments
over many generations, the populations of finches changed anatomically & behaviorally
accumulation of advantageous traits in population
emergence of different species (speciation)

19. Darwin’s Finches Differences in beaks allowed some finches to…
successfully compete
successfully feed
successfully reproduce
pass successful traits onto their offspring

20. Correlation of Species to Food Source
More Observations…
Correlation of Species to Food Source

21. Many islands also show distinct local variations in tortoise morphology…
…perhaps these are the first steps in the splitting of one species into several?

22. Artificial Selection This is not just a process of the past…
It is all around us today

23. Selective Breeding
Hidden variation can be exposed through selection!

24. A Reluctant Revolutionary
Returned to England in 1836
wrote papers describing his collections & observations
long treatise on barnacles
draft of his theory of species formation in 1844
instructed his wife to publish this essay upon his death
reluctant to publish but didn’t want ideas to die with him

25. And then came the letter….
In 1858, Darwin received a letter that changed everything…
Alfred Russel Wallace A young naturalist working in the East Indies, had written a short paper with a new idea. He asked Darwin to evaluate his ideas and pass it along for publication.

26. “On the Origin of Species by Means of Natural Selection”
November 24, 1859, Darwin published
“On the Origin of Species by Means of Natural Selection”

27. Essence of Darwin’s Ideas
Natural selection
variation exists in populations
over-production of offspring
more offspring than the environment can support
competition
for food, mates, nesting sites, escape predators
differential survival
successful traits = adaptations
differential reproduction
adaptations become more common in population
KNOW THIS!

28. LaMarckian vs. Darwinian View
in reaching higher vegetation giraffes stretch their necks & transmits the acquired longer neck to offspring
Darwin
giraffes born with longer necks survive better & leave more offspring who inherit their long necks 