1. Evolution by Natural Selection

2. Charles Darwin 1809-1882 British naturalist
Proposed the idea of evolution by natural selection
Collected clear evidence to support his ideas

3. Voyage of the HMS Beagle
Travels around the world
Makes many observations of natural world
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

4. Voyage of the HMS Beagle
Stopped in Galapagos Islands
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’s finches 13 species of finches in the Galápagos Islands
Was puzzling since only 1 species of this bird on the mainland of South America, 600 miles to the east, where they had all presumably originated
Darwin noted that the plants and animals of South America were very distinct from those of Europe.
Organisms from temperate regions of South America were more similar to those from the tropics of South America than to those from temperate regions of Europe.
Further, South American fossils more closely resembled modern species from that continent than those from Europe.

6. Darwin’s finches Differences in beaks
associated with eating different foods
adaptations to the foods available on their home islands
Darwin concluded that when the original South American finches reached the islands, they adapted to available food in different environments

7. Darwin’s finches Finches with beak differences that allowed them to…
successfully feed
successfully compete
successfully reproduce
pass the successful traits onto their offspring

8. Darwin’s finches
Over many generations, the finches changed anatomically and separated into different species
adaptive radiation

9. Origin of Species
On November 24, 1859, Charles Darwin published On the Origin of Species by Means of Natural Selection

10. In historical context

11. What did Darwin say? Every population of organisms includes variation
differences between individuals

12. What did Darwin say?
Organisms reproduce more than the environment can support
some offspring survive
some offspring don’t survive
competition
for food
for mates
for nesting spots
to get away from predators

13. Natural selection
Put together variation and competition and you get natural selection
survival of the fittest
fittest are the ones that survive to reproduce
The dodo is probably the world's most famous extinct bird. Dodos lived on the island of Mauritius, where over many years they became flightless. Unfortunately, when humans arrived on Mauritius -- off coast of east Africa in Indian Ocean -- bringing pigs and monkeys, the dodo was rapidly exterminated.
Dodo bird

14. Survival of the fittest
Who is the fittest?
traits fit the environment
the environment can change, so who is fit can change
Peppered moth

15. Peppered moth Year % dark % light 1848 5 95 1895 98 2 1995 19 81

16. Support for Darwin’s ideas
Fossil record
layers of sedimentary rock contain fossils
new layers cover older ones, creating a record over time
fossils within layers show that a succession of organisms have populated Earth throughout a long period of time

18. Archaeopteryx
A fossil of Archaeopteryx (Smithsonian Museum, Washington, DC), a reptilian bird ancestor that lived about 150 million years ago.

19. Fossil record Today’s organisms descended from ancestral species

20. Descent with modification
The history of life is like a tree with multiple branches from a common trunk
Closely related species — the twigs of the tree — shared the same line of descent until they branched off from a common ancestor

21. Support for Darwin’s ideas
Homology
similarities in characteristics resulting from common ancestry

22. Homologous structures
The forelimbs of human, cats, whales, and bats share the same skeletal structures
but different functions
branched off from common 4-limbed ancestor
homologous structures

23. Support for Darwin’s ideas
Artificial selection
Artificial breeding can take advantage of differences between individuals
“descendants” of the wolf

24. Support for Darwin’s ideas
Artificial selection
Artificial breeding can take advantage of differences between individuals
“descendants” of the wild mustard

25. Support for Darwin’s ideas
Natural selection in action
Insecticide & drug resistance
insecticide didn’t kill all individuals
resistant survivors reproduce
resistance is inherited
insecticide becomes less & less effective
The evolution of resistance to insecticides in hundreds of insect species is a classic example of natural selection in action.
The results of application of new insecticide are typically encouraging, killing 99% of the insects.
However, the effectiveness of the insecticide becomes less effective in subsequent applications. The few survivors from the early applications of the insecticide are those insects with genes that enable them to resist the chemical attack. Only these resistant individuals reproduce, passing on their resistance to their offspring. In each generation the % of insecticide-resistant individuals increases.

26. Theory of Evolution Theory of evolution by natural selection
well-supported idea
not “just a theory”!
Natural selection is widely accepted in science because its predictions have withstood thorough, continual testing by experiments & observations

27. Unity & diversity
Only evolution explains both the unity & diversity of life
By attributing the diversity of life to natural causes rather than to supernatural creation, Darwin gave biology a strong, scientific, testable foundation