1. Charles Darwin and His Big Idea: Influences and Evidence

2. Tuesday February 1, 2011 Warmup:
Natural selection is sometimes described as “survival of the fittest”.
Lilly says that “fit” means “bigger, faster, stronger” like an Olympic athlete.
Do you agree or disagree? Why? Give an example.

3. Today we will explore: What influenced Darwin?
What evidence did Darwin use to support his idea of evolution by natural selection?

4. Studied medicine and theology Joined HMS Beagle crew in 1831
Born 1809 in England
Studied medicine and theology
Joined HMS Beagle crew in 1831
Ship naturalist
Collected specimens
Made observations
Recorded thoughts
Darwin Movie- PBS “Evolution”

6. Fossils – preserved remains of ancient organisms
Patterns of Diversity
Plants & animals well suited to environments
Similar ecosystems had different animals present
Fossils – preserved remains of ancient organisms
Some resembled living organisms
Some had no living counterpart

7. Small group of islands west of South America
Observed many different organisms on the islands
Tortoises
Finches
Islands had different climates and different species

8. Darwin observed that the characteristics of many animals and plants varied noticeably among the different islands of the Galapagos
What would cause such variation to occur?

9. Common ideas at Darwin’s time:
Earth was only a few thousand years old
Neither the Earth nor its species had changed (Earth and living things are fixed)
Geological features had been produced by SUDDEN catastrophic events that humans rarely witnessed
Robin always looked and behaved as robins in the past

10. Ideas that shaped Darwin’s Thinking
James Hutton (1795)
Geologic forces shape Earth
Layers of rock form very slowly
Estimates Earth is millions of years old

11. Ideas That Shaped Darwin’s Thinking
Thomas Malthus (1798):
Growing human population will overwhelm resources
Darwin realized this applies even more to plants and animals that have tons of offspring!

12. Ideas That Shaped Darwin’s Thinking
Charles Lyell (1833):
Geological processes occurring now have shaped earth’s features throughout history
Scientists must explain past events using processes they can observe

13. Ideas That Shaped Darwin’s Thinking
Jean-Baptiste Lamarck (1809)
Recognized living things have changed over time
These traits can be passed on
“inheritance of acquired characteristics”
Organisms can alter the size/shape of their organs by using bodies in new ways
(slight problem with this idea)

14. Concept Map: Evidence for Natural Selection
Evidence of Evolution
includes
The fossil record
Geographic distribution of living species
Homologous body structures
Similarities in early development
which is composed of
which indicates
which implies
which implies
Physical remains of organisms
Common ancestral species
Similar genes

15. =Descent with Modification
What is Evolution?
Process by which today’s organisms have descended from ancient organisms (ancestry) +
Change over time
=Descent with Modification

16. Evidence for Evolution
How do we know evolution happens?

17. Fossil Record
Provides a peek at the past shows how living things have changed over the past 3.5 billion years.
May have bits missing, but fossil evidence clearly shows that life is old and has changed over time.

18. Transitional Fossils Gray Whale: lives today.
Early whale ancestor. Land mammal, but clearly related to whales and dolphins based on specializations of ear.
The position of nostrils has changed over time.
We would expect to see fossils that show intermediate forms.

19. Geographic Distribution
Some species are only found in certain parts of the world, likely because they evolved there
Alligators in United States
Marsupials on the islands of Australia and New Zealand

20. Geographic Distribution
Organisms show more similarity to species nearby than in similar climates but far apart.
Implies ancestry
Example: species on Galapagos Islands share more similarities with species on mainland South America than they do with species that live on other islands with similar climates across the world

21. Homologous Structures
Similar characteristics due to relatedness

22. Homologous Structures
The leaves look and function differently from each other, but are all derived from a common ancestral form.

23. Homologous Structures
Frogs, birds, rabbits, and lizards have different forelimbs, but they all share the same set of bones.
Extinct, but shows common ancestry

24. Homologous Structures
Each species has a different function for their limb. Does it seem possible that they all developed the same bone structure independent of each other?
“What could be more curious…?”

25. Vestigial Organs
Traits that are not useful to an organism, but remain from a useful ancestral trait
Ear-wiggling muscles
Tail in human and all vertebrate embryos.
Appendix
Wisdom teeth
Hip bone of a whale

26. Embryology/Development
Which of these is a pig embryo?
Different vertebrates show striking similarities in early stages of development.

27. Embryology/Development
Snakes have legged ancestors
Hind limb buds as embryos, but lose them before adulthood
Fossil evidence also shows snakes with hind limbs

28. Cellular/ Molecular Evidence
All organisms are made of cells
Produce proteins as building blocks and messengers
Membranes filled with water, proteins, lipids, carbohydrates, genetic material
Most use sugar for fuel

29. Molecular Evidence
DNA: simple four-base code that provides instructions for all living things
All life is linked to a common ancestor
Different species share some of the same genes
Worms share 25% of their genes with humans!

30. Molecular Evidence
The more similar the DNA of two living organisms, the more closely they may be to one another
Note: many other factors play a role as well
Activity:
study the amino acid sequence in the hemoglobin of humans, gorillas, and horses
use the data to show the similarities in DNA of these organisms