1. Darwin, Evolution and Natural Selection
Insect eaters
Bud eater
Seed eaters
Cactus
eater
Warbler
finch
Tree finches
Ground finches

2. Who was Charles Darwin? British naturalist
Proposed a way how evolution works
Called the method natural selection
Collected a lot of evidence to support his ideas
What did Darwin say?
What evidence supports Evolution by Natural Selection?
What impact did Evolution have on biology?

3. How did Darwin figure out his idea?
Was hired to work on the HMS Beagle as a naturalist
(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
Captain Robert Fitzroy

4. 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

5. Darwin found… many unique species
Many of Darwin’s observations made him wonder… Why?
Darwin asked:
Why were these creatures found only on the Galapagos Islands?

6. Darwin found: Different shells on tortoises on different islands
Darwin asked:
Is there a relationship between the environment & what an animal looks like?

7. Darwin found… birds Darwin found:
Many different birds on the Galapagos Islands.
He thought he found very different kinds…
Finch?
Sparrow?
Woodpecker?
Warbler?

8. But Darwin found… a lot of finches
Darwin was amazed to find out:
All 14 species of birds were different species of finches…
Large ground finch
Small ground finch
But there is only one species of finch on the mainland!
Finch?
Sparrow?
Darwin asked:
If the Galapagos finches came from the mainland, why are they so different now?
Warbler finch
Tree finch
Woodpecker?
Warbler?

9. The finches cinched it! different beaks are inherited variations
serve as adaptations that help birds compete for food
these birds survive & reproduce
pass on the genes for those more fit beaks
over time nature selected for different species with different beaks
Darwin found:
The differences between species of finches were associated with the different food they ate.
Darwin said:
Ahaaaa! A flock of South American finches were stranded on the Galapagos…
Large ground finch
Big seed eater
Small ground finch
Small seed eater
Insect eater
Warbler finch
Leaf & bud eater
Tree finch

10. From 1 species to 14 species…
Warbler finch
Woodpecker finch
Small insectivorous
tree finch
Large
insectivorous
Vegetarian
Cactus finch
Sharp-beaked finch
Small ground
finch
Medium
ground finch
Large ground
Insect eaters
Bud eater
Seed eaters
Cactus
eater
Warbler
Tree finches
Ground finches
natural selection for best survival & reproduction
variation

11. What is Natural Selection?
Process in which a trait becomes more or less common in a population.
Natural selection acted on peppered moth color… light moths survived when there was less pollution and dark moths survived when coal blackened the trees.

12. What evidence supports evolution
What evidence supports evolution? (don’t write these down yet, we will look in more detail as we continue)
Fossil record
shows change over time
Anatomical record
comparing body structures
Molecular record
comparing protein & DNA sequences
Artificial selection
human caused evolution

13. 1. Fossil record (fossil = “dug up”)
Layers of rock contain fossils
Bones, shells, tracks, impressions, etc.
New layers cover older ones
Show a series of organisms have lived on Earth

14. Dating Fossils Absolute dating Relative dating
Use radioactive isotopes to determine age
Relative dating
Use other objects around a fossil to approximate age

15. Life on Earth has changed
Fossils tell a story…
the Earth is old
Life is old
Life on Earth has changed

16. Analogous structures Dolphins: aquatic mammal
Sharks: aquatic cartilaginous fish
both adapted to life in the sea
not closely related

17. Vestigial structures Evolutionary “leftovers”
Hind leg bones on whale fossils
Vestigial pelvis bones on modern whales

18. Bottlenose dolphin mutation
Dolphin caught in 2006 had two hind limbs
Possible re-emergence (through mutation) of a vestigial trait

19. Vestigial traits in humans
Humans have vestigial traits too!
The appendix
vestigial form of the cecum
Still have a cecum, but it is smaller
herbivores use the cecum to digest plant fiber (cellulose)

20. Human vestigial traits cont.
All humans have a tailbone (coccyx)
rarely someone is born with a vestigial tail

21. Human vestigial traits cont.
The goose-bump response
Remains from a time when we had thicker fur
Could stand hair on end to frighten predators or insulate from the cold

22. Comparative embryology
Development of embryo tells an evolutionary story
similar structures during development
all vertebrate embryos have a “gill pouch” at one stage of development

23. 3. Molecular record Comparing nucleic acid & protein structure
everyone uses the same code!
DNA & RNA (nucleotides)
Proteins (amino acids)
compare common genes
compare common proteins
number of amino acids different from human hemoglobin

24. Building “family” trees
Closely related species are branches on the tree (called a cladogram) — coming from a common ancestor
Common ancestor is now extinct

25. “descendants” of the wolf
4. Artificial selection
How do we know selection can change a population?
we do it all the time!
“evolution by human selection”
“descendants” of the wolf

26. More examples of artificial selection
Agricultural crops
Farm animals