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Chapter 15 --Darwin and Evolution

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1 Chapter 15 --Darwin and Evolution
“The Origin of Species” Question: How did the giraffe get its long neck? Why are there 9 subspecies of giraffes?

2 Pre-Darwinian world-view was determined by theological beliefs.
1) The earth is young; ~10,000 years old 2) Each species was specially created and did not change 3) Observations are to substantiate the prevailing worldview. 4) Variations are imperfections Rothchilds Giraffe How would this worldview explain the giraffe’s neck? How would it explain the 9 subspecies?

3 History of Evolutionary Thought
In 1831, Charles Darwin, a 22-year-old naturalist, accepted a position aboard the ship HMS Beagle that began a voyage around the world. Darwin made observations of animals that inhabited the island - a study of BIOGEOGRAPHY tortoises iguanas finches

4 The Voyage of the Beagle

5 Homo sapiens Canis lupus Giraffa camelopardalis
Taxonomy is the science of classifying organisms. Carolus Linnaeus developed a binomial system of nomenclature - two-part names for each species GENUS SPECIES Giraffe camelopardalis angolensis (Angolan giraffe) Giraffe camelopardalis camelopardalis (Nubian giraffe) Giraffe camelopardalis reticulata (Reticuated giraffe) Homo sapiens Canis lupus Giraffa camelopardalis

6 Masai Giraffe (Giraffa camelopardalis tippelskirchi)
Thornicroft Giraffe Giraffa camelopardalis thornicrofti

7 Biogeography study of the distribution of species and ecosystems in geographic space and through geological time A cladogram shows how these giraffes are related. Why are there so many different subspecies and why in distinct locations?

8 Darwin had a similar question about the finches on the Galapagos
Darwin’s Theory of Evolution by Natural Selection Darwin had a similar question about the finches on the Galapagos Finches on the Galápagos Islands resembled a mainland finch but there were more types. Galápagos finch species varied by nesting site, beak size, and eating habits. Darwin proposed that each bird was descended from the mainland species. this idea is known as COMMON DESCENT

9 Are all of these giraffes also descended from one common ancestor?

10 Lamarck had an idea Lamarck mistakenly saw "a desire for perfection" as inherent in all living things. His view of giraffe evolution would have looked like this: He called this model: The Inheritance of Acquired Characteristics

11 Experiments fail to uphold Lamarck's idea
Experiments fail to uphold Lamarck's idea. Would this couple have children with long necks?          

12 Natural Selection and Adaptation
Natural selection was proposed by both Alfred Russel Wallace and Darwin. It is the MECHANISM by which evolution occurs. It would explain how giraffes got their long necks, why finches have different beaks, and why there are two different varieties of tortoises on the island.

13 4 Steps of Natural Selection
1. Members of a population have variations that are heritable 2. More individuals are produced than can survive 3. Those with the best variations are more likely to survive and reproduce - the term FITNESS is used to describe these traits. 4. Traits are passed to the offspring

14 There are two consequences of natural selection.
1. An increasing proportion of individuals in succeeding generations will have the adaptive characteristics. 2. The result of natural selection is a population adapted to its local environment.

15 3. Extinction occurs when previous adaptations are no longer suitable to a changed  environment.

16 How does natural selection explain the finches on the Galapagos?

17 How does it explain the giraffes?
Procamelus (ancestor)

18 The Definition of Evolution
Evolution is the change in allele frequencies, or a change in the gene pool, of a population. Mythbuster: “No one has ever seen one animal change into another, therefore evolution isn’t true.” How would you respond to this statement?

19 IMPORTANT!!! Individuals do not evolve. (they either live or die)
Fully armored stickleback (ocean) Individuals do not evolve. (they either live or die) *POPULATIONS EVOLVE* 2. Evolution does not have a direction. Organisms aren’t “trying” to be anything. 3. Fitness refers to an organism's ability to survive in their environment - it doesn’t necessarily mean “stronger” Fully armored stickleback (ocean)

20 3. Individuals differ in FITNESS
a) fitness measures an organism’s reproductive success b) it does not necessarily mean stronger. Fully armored stickleback (ocean) Low armor (freshwater)

21 Dogs breeds were developed by years of breeding wolves
ARTIFICIAL SELECTION Dogs breeds were developed by years of breeding wolves We chose the traits most desirable, then bred the dogs with those traits. Nature does the same with “natural selection”

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