1. EVOLUTION Objectives: 1. Explain how natural selection works.
2. What observations helped Darwin develop the theory of evolution?
3. What does adaptation mean? Give an example of an organism adapting to its environment.

2. Early theories (pre-1700’s)
Before Darwin, nature was seen as not changing (i.e., immutable) but as having originated through spontaneous generation.

3. An understanding of the age of the Earth develops through geology.
The Earth has been and is still gradually changing.
Inheritance of acquired traits (use and disuse).
e.g., baby giraffes are born with long necks because their parents stretched their necks to reach leaves (Jean-Baptiste Lamarck, 1801)
The Earth as we see it today is the result of millions of years of gradual change. It is still changing. Mountains are being built up and ground is eroding away. Coast lines are constantly changing. Plates are moving the shape and arrangement of the continents is different then it was millions of years ago.

4. Misconception
Lamark had thought that giraffe’s had lived in areas where their food source was dwindling due to competition with other organisms. They had to reach up to reach the leaves higher up in the trees. As a result of this stretching, their necks grew (stretched) and they passed this on to their offspring.

5. Genetics and the Passing on of Traits
Living organisms pass on their traits to their offspring.
Today’s species came about through gradual change.
What drove that change?
SURVIVAL/SEX/!!!!

6. Darwin and the Voyage of the Beagle
December, 1831, Charles Darwin, a naturalist in his 20’s began a 5-year journey around the world on a ship called HMS Beagle
Darwin’s role was to
observe, record, and
collect specimens of
rocks, minerals, plants, and animals
from a well- educated family, ,
in part to find evidence to support biblical creation (Darwin left England believing in the immutable nature of species)
- when they got to Galapagos, a chain of volcanic islands off the coast of Ecuador, Darwin saw that although a lot of the species were similar to those of the S. America’s mainland, they had some unique traits

9. Darwin collected 1000’s of specimens and shipped them to England, mainly from South America and a chain of volcanic islands called Galapagos
He did not realize what he was seeing until years later (e.g., didn’t catalogue the finches very well, ate turtles that would later support his theories, etc.)
Darwin spent the next 20 years analyzing his findings in light of artificial selection (e.g., breeding of pigeons, breeding of dogs, etc.)

10. Darwin’s Finches Arrival Success Competition Diversity & Opportunity
Radiation

11. Adaptive Radiation
Perhaps a single ancestral species transported from nearby land might have given rise to a number of similar but distinct new species.

12. Hawaiian honeycreeper

13. What Darwin Observed
1) Homologous Features:
different functions, but similar structure (flippers, hands, wings)
All forelimbs of vertebrates have the same pattern of bones

14. The flippers of whales, and the wings of birds are homologous.

15. 2) Analogous features: similar functions, but different structure (wings of birds and bees)
Darwin’s conclusion: organisms with homologous features likely shared a more recent ancestor, while those with analogous features do not!

16. Example: whales have pelvic bones that do not attach to legs
3) Vestigial Features: non-functional structures that are homologous to fully functioning structures in closely related species.
Example: whales have pelvic bones that do not attach to legs

18. 4) Similarities in early development; e.g., tailbones, gill slits.
Darwin’s conclusion: these homologous features are from a shared common ancestor.

19. Other Evidence for Evolution…
Stuff that we have seen in our time…

20. When comparing
the DNA of one
species to another,
more similarities are
found in species
that are more
closely related.

21. Evidence for Evolution
The Fossil Record-Layer shows change
Shows numbers extinct animals
Shows similarities between extinct animals and animals that are alive today
The earth’s layers show a time scale of species and when they appeared on earth (and when they died out)

24. Transitional fossils are fossils that show intermediary links between groups of organisms
They can provide a link between the past and present

25. Direct observation of species change
Bacteria become resistant to antibiotics
Wolves were bred over many generations to become dogs (artificial selection) and then bred further to create a variety of breeds

26. What did Darwin think drove Evolution???
Artificial Selection
Selecting offspring with desirable traits as breeding stock for succeeding generations
Example: corn with higher oil content
Darwin’s conclusion: if people could alter the appearance and behaviour of species through artificial selection, then the environment could have a similar selective effect on wild species!

27. Artificial Selection

28. But how does evolution really work???
Show the PBS video “Evolving Ideas: How does evolution really work?” – it’s on Youtube

29. Natural Selection as the Cause of Evolution
called “natural selection” because it happens on its own
1. Genetic Variation
- there are many varieties of alleles
- caused by random mutations
can be passed onto offspring (inherited variation)
2. Overproduction of Offspring
- organisms produce too many offspring

30. 3. Struggle for existence
- competition for limited resources
4. Differential survival and reproduction
- only organisms that have certain characteristics will survive to reproduce
- non-random, caused by the environment: amount of food, competition (e.g., Darwin’s finches)

31. Other Mechanisms that Drive Evolution
Sexual Selection: the process by which a trait that enables an organism to acquire more mates becomes more common.
Males compete for females (combat)
Females chose males (desirable traits)

32. Your Task