1. More Historical Evidence The study of Homologies

2. Homology ► What does the word Homologous mean? ► Homology is the study of similarity between organisms ► There are three major branches of homology:  Anatomical Homology  Embryological Homology  Molecular Homology

3. Anatomical Homology ► Outwardly, these look like very different structures.

4. Beneath The Surface…

5. Strange Coincidence? ► At a structural level, the wing of a bat, a human arm and a whale’s flipper all share the same number, type and location of bones, suggesting that THEY MAY SHARE COMMON ANCESTRY ► 'What can be more curious than that the hand of a man, formed for grasping, that of a mole for digging, the leg of the horse, the paddle of the porpoise, and the wing of the bat should all be constructed on the same pattern and should include similar bones in the same relative position?' (Charles Darwin)

6. Vestigial Structures ► Some organisms have structures that appear to be useless relics of the past ► Suggests that these organisms may be descended from ancestral organisms in which the structure IS still useful!

7. Evidence of Evoluton ► Analogous Structures: structures similar in function, but not inherited from a common ancestor. ► Same function, different structure

8. Embryological Homology ► The diagram below shows embryos of five different species: pig, chicken, fish, turtle, and human. Can you tell which is which?

9. Figured it out yet?

10. How about now?

11. Did you guess correctly?

13. Embryological Homology ► Did you know that when you were inside your mother’s womb, for a while you looked almost exactly like a fish? ► Vertebrate embryos all share a similar pattern of development, suggesting that they may share common ancestry

14. Human – 31 days Chicken – 2 ½ days Pig – 21 days

15. Molecular Homology ► All living things contain DNA and RNA. ► Changes in Proteins, DNA and RNA can be traced from ancestors to their descendents. ► The fewer Amino Acid differences between organisms, the closer their inferred evolutionary relationship.  Hemoglobin and Cytochrome C are a group of proteins that are commonly found in many different organisms

16. Proteins & Amino Acids ► Proteins (eg. Hemoglobin, Cytochrome c) can exist in subtly different forms, depending on their specific Amino Acid configuration Apple Protein Celery Protein

17. Our Chimpanzee “Cousins”? ► Comparison of chimp and human chromosomes reveals many similarities ► Could we be related by common descent?...

18. Example: the Evolutionary Hypothesis of Common Ancestry Chromosome Numbers in the great apes: 46 human (Homo)46 chimpanzee (Pan)48 gorilla (Gorilla)48 orangutan (Pogo)48 Testable prediction: Testable prediction: If these organisms share common ancestry, the human genome must contain a fused chromosome.

19. Comparing Chromosomes ► The banding patterns on stained chromosomes show regions of tightly condensed (dark) and loosely condensed (pale) Histone proteins ► Protein location is dependent on gene loci, and the bands can therefore be used to infer genetic similarity ► How similar would you expect our banding pattern to be, compared to Chimpanzees?

20. Human vs. Chimp Chromosomes Human chrom. are on the left Chimp’s are on the right Notice that Human Chromosome #2 appears to be a combination of Chimp Chromosomes #2 & 3

21. Chromosome Numbers in the great apes (Hominidae): human (Homo)46 chimpanzee (Pan)48 gorilla (Gorilla)48 orangutan (Pogo)48 Testable prediction: Testable prediction: The marks of that fusion must appear in one of the human chromosomes. Centromere Telomere Ancestral Chromosomes Fusion Homo sapiens Centromere #1 Telomere sequences Centromere #2

22. “Chromosome 2 is unique to the human lineage of evolution, having emerged as a result of head-to- head fusion of two acrocentric chromosomes that remained separate in other primates. The precise fusion site has been located in 2q13–2q14.1 (ref. 2; hg 16:114455823 – 114455838), where our analysis confirmed the presence of multiple subtelomeric duplications to chromosomes 1, 5, 8, 9, 10, 12, 19, 21 and 22 (Fig. 3; Supplementary Fig. 3a, region A). During the formation of human chromosome 2, one of the two centromeres became inactivated (2q21, which corresponds to the centromere from chimp chromosome 13) and the centromeric structure quickly deterioriated (42).” Hillier et al (2005) “Generation and Annotation of the DNA sequences of human chromosomes 2 and 4,” Nature 434: 724 – 731. “Chromosome 2 is unique to the human lineage of evolution, having emerged as a result of head-to- head fusion of two acrocentric chromosomes that remained separate in other primates. The precise fusion site has been located in 2q13–2q14.1 (ref. 2; hg 16:114455823 – 114455838), where our analysis confirmed the presence of multiple subtelomeric duplications to chromosomes 1, 5, 8, 9, 10, 12, 19, 21 and 22 (Fig. 3; Supplementary Fig. 3a, region A). During the formation of human chromosome 2, one of the two centromeres became inactivated (2q21, which corresponds to the centromere from chimp chromosome 13) and the centromeric structure quickly deterioriated (42).” Hillier et al (2005) “Generation and Annotation of the DNA sequences of human chromosomes 2 and 4,” Nature 434: 724 – 731. Homo sapiens Inactivated centromere Telomere sequences What do YOU think about this information…? Human Chromosome #2 shows the exact point at which this fusion appears to have taken place

23. What do you think…? Darwin had NO IDEA about Chromosomes – does this new information SUPPORT his evolutionary hypothesis, or NOT…?

24. Present-Day Evidence For Evolution “Observing Evolution In Action”

25. Natural Selection ► Is there any evidence of Natural Selection taking place in real populations? ► One study, performed during the industrial revolution in England, demonstrated that populations of organisms ARE greatly affected by environmental changes

26. The Peppered Moth ► Two different forms of the moth existed ► One Dark form, one Light ► Both forms were common

27. Antibiotic Resistance ► Because Bacteria reproduce so quickly, they represent excellent specimens for testing Natural Selection ► Watch how quickly they can “evolve” because of Natural Selection… Watch how quickly they can “evolve” because of Natural Selection… Watch how quickly they can “evolve” because of Natural Selection…

28. Examples of Evolution at Work Speciation (formation of a new species) ► results from reproductive isolation - when members of two ancestral populations can no longer interbreed to produce fertile offspring ► How do populations get isolated?....

29. Behavioral Isolation Two populations are capable of interbreeding but have differences in courtship rituals. Eastern Meadowlark Western Meadowlark Both birds are in the same geographic range but they have a different mating song Isolating Mechanisms

30. Geographic Isolation Two populations separated by geographic barriers like rivers, and mountains Abert squirrel Kaibab squirrel Colorado river separated this species into two separate populations. A new subspecies formed – the Kaibab squirrel

31. Isolating Mechanisms Temporal Isolation Individual varieties of an organism may breed at different times of day/year Ex. Orchids in a rainforest