1. Evolution… by Natural Selection

2. Why do we accept this as a Scientific Theory?
What is Evolution?
Evolution
changes in living organisms over time
explains how modern organisms have descended from ancient organisms
Why do we accept this as a Scientific Theory?

3. What we know, so far…. Many different species alive today
All life shares common characteristics
The Earth is very old
Life is very old
Life has changed over time
The changes have been little changes over long periods of time
But how does this work?

4. Evolution explains Unity & Diversity
Only evolution explains both
unity of life
similarities between all living things
diversity of life
wide variety of different creatures on Earth
DNA

5. Charles Darwin Proposed a way how evolution works
How did creatures change over time?
by natural selection
Collected a lot of evidence to support his ideas
British naturalist
What did Darwin say?
What evidence supports Evolution by Natural Selection?
What impact did Evolution have on biology?

6. Voyage of the HMS Beagle
Invited to travel around the world
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

7. 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

8. 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?

9. Darwin found…clues in the fossils
present day Armadillos
Darwin found…clues in the fossils
Darwin found:
Evidence that creatures have changed over time
ancient Armadillo
Darwin asked:
Why should extinct armadillos & modern armadillos be found on same continent?

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

11. Darwin’s finches Darwin’s conclusions Variations in beaks
differences in beaks in the original flock
adaptations to foods available on islands
Natural selection for most fit
over many generations, the finches were selected for specific beaks & behaviors
Offspring inherit successful traits
accumulation of winning traits: both beaks & behaviors
Speciation- process by which new species arise
Separate into different species

12. The finches cinched it for Darwin

13. 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

14. Earlier ideas on Evolution
LaMarck
evolution by acquired traits
creatures developed traits during their lifetime
give those traits to their offspring
example
in reaching higher leaves giraffes stretch their necks & give the acquired longer neck to offspring
not accepted as valid

15. Darwin’s view of Evolution
giraffes that already have long necks survive better
leave more offspring who inherit their long necks
variation
selection & survival
reproduction & inheritance of best fit traits 

16. 5 Principles of Natural Selection
heritable variation variation exists in populations (we are all different!)
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

17. Survival & Reproduction of the fittest
not the biggest…
…the fittest!
not the fastest…
not the bravest…
not the strongest…
Adaptations
the traits that help an organism fit the environment better to
survive & reproduce

18. evolution Darwin concluded:
Each species has descended, with changes, from other species over time.
Darwin called this…
Descent With Modifications or
evolution
(change in species over time)

19. Evidence supporting evolution
Fossil record
shows change over time
Anatomical record
comparing body structures
homology & vestigial structures
embryology & development
Molecular record
comparing protein & DNA sequences
Artificial selection
human caused evolution

20. 1. Fossil record Layers of rock contain fossils
new layers cover older ones
creates a record over time
fossils show a series of organisms have lived on Earth
over a long period of time

21. Law of Superposition
The deeper you dig, the farther back in time you go.
The bottom layer is the oldest.

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

23. We found the fossil — no joke!
Land Mammal ?
Complete series of transitional fossils ?
Where are the intermediate fossils? ? ?
There are innumerable intermediate & transitional forms
Whales as land creatures returning to the water….
Where are the intermediate forms of whale ancestors?
Cartoon making fun of this idea.
The cartoons disappeared years ago when this fossil was found.
Ambilocetic natans = “Walking whale who likes to swim”
4-5 intermediate forms all found in last 2 decades
Indus River valley in between India & Pakistan.
Someone’s idea of a joke!
Ocean Mammal
But the joke’s on them!!

24. Evolution from sea to land
2006 fossil discovery of early tetrapod
4 limbs
Missing link from sea to land animals

25. 3. Anatomical record Animals with different structures on the surface
But when you look under the skin…
It tells an evolutionary story of common ancestors