Wednesday: February 22nd

1. Ms. Fisher 2/22/12 Wednesday: February 22nd 1.) Class will divide into four groups. ALL four groups will read BOTH articles. However, Groups 1 & 2 will be responsible for leading the group discussion with the article: “Adaptation: The Case of Penguins” and sharing the answers to this article’s questions. While Groups 3 &4 will be responsible for leading the group discussion with the article: “Darwin and Natural Selection” and sharing the answers to this article’s questions. (Please do not write on the articles, write on loose leaf paper. All responses to questions must be submitted before the end of class. Therefore, please pay close attention when your peers are sharing article responses!) 2.) Continue with Evolution PowerPoint & Packet!

2. Objective for today: Through reading different articles on adaptation and natural selection with your peers, you will further develop your understanding on natural selection and know what factors play a role in this process. Today, you will complete and submit corresponding worksheets that go with these articles. (If time allows, continue with evolution power-point.)

3. 3) Evidence for Evolution I. Geographic Distribution IV. The Fossil Record II. Homologous Anatomy V. Embryology III. Vestigial Structures VI. DNA and Genetics

4. Evidence For Evolution: III. Vestigial Structures Vestigial Structures Physical remnants of organs that once helped a species’ ancestors survive, but are no longer useful. • Vestigial structures tend to be very small, because they are not needed for survival. Hence, they are only “vestiges” of what they once were. • If a species has an anatomical structure that appears to be out of place, many times it is vestigial. • The human appendix is a good example of a “vestige” of an earlier digestive organ that helped our ancestors process plant material.

5. Evidence For Evolution: III. Vestigial Structures Human Examples Other human examples include the tailbone and wisdom teeth. Remnant of earlier primate ancestors with tails Leftover from our ancestors with larger jaws This is why wisdom teeth are so commonly removed. Modern humans’ jaws tend to be too small, so the teeth get impacted. Some people never even develop wisdom teeth.

6. Evidence For Evolution: III. Vestigial Structures Pelvic Bones in Whales Though whales spend their entire lives underwater and have no hind limbs, they still have tiny leg bones and remains of a pelvis, which have shrunken to the point where they’re not even attached to the rest of the skeleton. In other words, whales have leg bones. What possible explanation makes sense unless they gradually evolved from earlier ancestors who had legs and lived on land?

7. Evidence For Evolution: III. Vestigial Structures Flightless Birds The wings on flightless birds are vestigial structures because they have shrunken over thousands of generations to the point where they can no longer be used for flight. Why did the wings “shrink” over time? Often, flightless birds are found on islands where their ancestors landed millions of years before. On an island with no predators, wings are not really needed for survival. In some cases, e.g. penguins, their smaller wings have since become useful in other ways.

8. Evidence For Evolution: III. Vestigial Structures Other Vestigiality Rather than physical structures, some vestigial traits come in the form of reactions or behaviors. When you get goosebumps because you are startled or get a chill, your body is reacting in the same way as this cat. This reaction no longer serves any purpose in human beings but earlier mammal ancestors, as well as those still around, use it to puff up their fur for warmth, or to intimidate would-be predators.

9. Evidence For Evolution: III. Vestigial Structures Other Vestigiality Here are a couple more examples: Similar to whales, pythons and boa constrictors have remnants of pelvic bones and legs. In this case, however, they are actually visible externally. Certain fish species which have lived in caves for thousands of years have evolved to have no eyes, since they are useless in the dark. Blind cave fish Pelvic spurs on a python

10. Evidence For Evolution: III. Vestigial Structures Vestigial DNA • Even more tellingly, most species, including humans have huge sections of so-called “junk DNA” which seem to be completely non-functional. • Much of this “useless” genetic material is vestigial. In other words, it used to code for important traits in our ancestors, but is no longer needed. • This vestigial DNA has essentially become “deactivated” through genetic mutations over the course of millions of years, and is now just taking up space on the genome.

11. Ms. Fisher 02/22/12 Assessment: Objective for Today: Through reading different articles on adaptation and natural selection with your peers, you will further develop your understanding on natural selection and know what factors play a roll in this process. • Availability of Food • Predator-prey relationship • Climate

12. Evidence For Evolution: IV. The Fossil Record • The Fossil Record • A physical history of the life on Earth in the form of fossils buried within chronologically oriented layers of sedimentary rock. • Shows gradual progression, including transitional species. Tiktaalik Discovered in 2004, Tiktaalik is a fossil specimen that shows the transition between ancient fish and the first land-dwelling amphibians, around 380 million years ago.

13. Evidence For Evolution: IV. The Fossil Record Horse Evolution The fossil record of the modern horse is a great example of the continuous progression that shows gradual change over millions of years. Notice how the toes gradually get smaller and smaller, leaving only the middle toe, which becomes the foot and hoof of the modern horse.

14. Evidence For Evolution: IV. The Fossil Record Tetrapod Evolution • The evolution of four-limbed organisms, or tetrapods, shows a similar progression. • There are no giant leaps; only tiny, gradual incremental changes over millions of years. • New transitional fossils, sometimes called “missing links,” are continually being discovered.

15. Evidence For Evolution: IV. The Fossil Record Whale Ancestors Ambulocetus (50 million years ago) Fossil evidence has demonstrated how whales have evolved from land mammals who walked on four legs. Rodhocetus (47 million years ago)

16. Evidence For Evolution: IV. The Fossil Record Whale Evolution Ancient land-dwelling ancestors • Once again, there is gradual progression in the fossil record, and new fossils are being discovered all the time. • The gradual change can even be seen in the evolution of the blowhole. Modern baleen whales

17. Evidence For Evolution: IV. The Fossil Record More Transitional Fossils Eupodophis (92 mill.) Archaeopteryx (150 million years ago) Transition between lizards and the earliest snakes Transition between dinosaurs and birds

18. Evidence For Evolution: IV. The Fossil Record More Transitional Fossils Australopithecus afarensis (3.2 mill.) Dimetrodon (265 mill.) Transition between primitive ape-like hominids and more modern humans Transition between reptiles and early mammals

19. Evidence For Evolution: IV. The Fossil Record Hominid Family Tree Thousands of hominid specimens have been discovered in the past century, allowing scientists to piece together the hominid family tree, extending back about 6 million years to our ape-like ancestors. Every newly discovered species is a transition between its ancestors and descendants on the tree of life.

20. Evidence For Evolution: IV. The Fossil Record Living Fossils Some modern species, such as the platypus still retain certain primitive traits, that link them to these early transitional “missing links.” Duck-billed platypus The platypus belongs to a group of primitive mammals called monotremes. This group branched off from reptiles very early, and so these species still lay eggs like their reptile ancestors.

21. Evidence For Evolution: IV. The Fossil Record Living Fossils • Similarly, mudskippers are amphibious fish which are able to gulp air and walk on land using their strong pectoral fins. • Not really a “living fossil” because the species evolved relatively recently • Still represents a modern look at the transition between sea and land, when the earliest amphibians evolved Mudskipper

22. Evidence For Evolution: V. Embryology Embryology Very close similarities in early developmental stages of related species 1 cm Human embryo 5 weeks after conception

23. Evidence For Evolution: V. Embryology Animal Embryology Can you guess what type of animal this is?

24. Evidence For Evolution: V. Embryology Animal Embryology Can you guess what type of animal this is? Turtle embryo See the developing shell?

25. Evidence For Evolution: V. Embryology Animal Embryology Newly forming vertebrate embryos all look very similar so it’s difficult to tell what animal you’re looking at in the early stages of development. All vertebrates start out almost the same because they all share a common ancestor which was much more primitive. Turtle embryo • All vertebrates embryos start out with a tail and tiny neck slits resembling gills. This includes humans! • In land-dwelling groups such as mammals and reptiles, these slits disappear as the embryo develops, eventually becoming parts of the throat and mouth. • In humans, the tail is absorbed into the growing body and remains as the tailbone.

26. Evidence For Evolution: V. Embryology Vertebrate Embryology early development (all very similar) middle stage embryo (starting to differentiate) fetal stage (identifiable as separate species)

27. Evidence For Evolution: V. Embryology Vertebrate Embryology Notice how more closely related species tend to resemble each other further along in development. Click here to play “Which Embryo is Human?”

28. Evidence For Evolution: V. Embryology Side by Side Bottle-nosed dolphin Human Both embryos at about 5 weeks gestation!

29. Evidence For Evolution: V. Embryology Side by Side Bottle-nosed dolphin Notice the beginnings of hind leg buds which form early on and disappear later on in development.

30. Evidence For Evolution: VI. DNA and Genetics • DNA • Genetic code shared by all living things on Earth • Allows us to look at different species at the molecular level and compare their genes. • Shows conclusively that all living things are related; it’s just a matter of degree.

31. Evidence For Evolution: VI. DNA and Genetics Primate DNA • Comparing our DNA allows us to determine which species are our closest relatives. • Humans and chimpanzees’ DNA are roughly 96% identical. chimp gorilla human orangutan gibbon This evidence indicates that both chimps and humans received their identical genetic material from a common ancestor who lived about 6 million years ago.

32. Evidence For Evolution: VI. DNA and Genetics Primate Classification apes “Great Apes” orangutan human chimp gibbon bonobo gorilla hominids These primate groups are determined by how much homologous DNA they have in common.

33. Evidence For Evolution: VI. DNA and Genetics DNA Evidence • DNA evidence is some of the strongest evidence for evolution and the common ancestry of all living things on Earth. • It allows us to confirm at the molecular level the extent to which species are related AND estimate how long ago two species probably diverged from their common ancestor. • Molecular DNA evidence shows that humans and chimpanzees diverged from one another between 5 and 7 million years ago. • That common ancestor diverged from the gorilla family line even earlier, and so on down the family tree. Primatologist, Jane Goodall and one of her chimp friends

34. Evidence For Evolution: VI. DNA and Genetics Chromosomal Evidence • All of the Great Apes have their DNA organized into 24 chromosome pairs, whereas humans have only have 23 pairs. • If humans share a common ancestor with all the other Great Apes, we should all have the same number of chromosome pairs because no one could survive if a whole section of DNA just disappeared! How is this possible? (24 pairs) (23 pairs)

35. Evidence For Evolution: VI. DNA and Genetics Chromosomal Evidence If one chromosome pair wasn’t just lost, then what could have happened to it? What if two of the earlier ape chromosomes somehow got “stuck”, or fused, together during cell division at some point in the distant past? Is there any way to verify this? (24 pairs) (23 pairs)

36. Evidence For Evolution: VI. DNA and Genetics Chromosomal Evidence Actually, it has been verified. • By examining the genes found on the ape chromosomes, scientists have found two ape chromosomes that contain the same genes that appear on ONE of our human chromosomes. • So it’s been conclusively demonstrated that they did get “stuck” together, and all modern humans have inherited that fused chromosome. (24 pairs) (23 pairs)

37. Evidence For Evolution: VI. DNA and Genetics Chromosomal Evidence • This image shows the genes that match up between human and chimp DNA. • Note the two chimp chromosomes that match up to our own chromosome #2. This chart also shows how different sections of DNA have inverted themselves at multiples times in the past. This is one type of mutation.

38. Evidence For Evolution: VI. DNA and Genetics Chromosomal Evidence Orangutan Human This is extremely conclusive evidence of our common ancestry with all the other apes. Gorilla Chimp Click the image above to see biology professor Kenneth Miller explain the “Case of the Missing Chromosome”.

39. 1) What is Evolution? 2) Natural Selection 3) Evidence for Evolution 4) Evolution in Action Section 4 of 4: Evolution in Action

40. 4) Evolution in Action Usually, the process of evolution takes place so slowly that we can’t see it happening. In selective breeding of livestock and hybridization of crops, humans have sped up and exaggerated this basic process so that we can actually observe the allele frequencies changing over shorter times.

41. Evolution in Action There are numerous examples, however, in which a species evolves rapidly enough on their own that we can see evolution in action. This usually happens because of one or both of the following: A species reproduces very quickly so that numerous generations pass in a short time. Selection pressure is very great.

42. Antibiotic Resistance Bacteria reproduce extremely quickly, and many can double their population in under an hour. Bacteria can quickly evolve to be resistant to antibiotics if the drugs are not administered properly or for the entire duration of the infection. If any bacteria are not fully wiped out by the antibiotics, the more resistant ones that remain will continue to reproduce.

43. Tuskless Elephants An example of rapid evolution due to very high selection pressure is taking place among African elephants. As prized sources of ivory, they are being hunted closer and closer to extinction mainly for their tusks. • Since the elephants with the largest tusks are being hunted most, there is a heightened selection pressure (in this case, humans) that is wiping out large-tusked elephants. • The remaining population has higher frequency of smaller-tusked elephants, and some with no tusks at all! • So overall, it appears that elephant tusks are shrinking.

44. Sickle-Cell Anemia Human evolution in action • Sickle-cell anemia is a genetic disorder in which the blood cells take on a shriveled sickle shape. • The disease can be life-threatening and generally tends to reduce life expectancy significantly. • The disease is treatable. In America, it affects about 90,000 people, while there are over 2 million genetic carriers who have one recessive sickle-cell allele, but do not have the actual disease.

45. A Sickle-Cell Safari It has long been known that the frequency of the disease widely varies between certain ethnicities, and occurs at a much higher ratio among those of African descent. Incidence of the sickle-cell trait in Africa It appears that the frequency tends to correspond to people originating in more tropical climates. What might explain this curious connection?

46. A Sickle-Cell Safari Incidence of the sickle-cell trait in Africa Distribution of Malaria In 1954, a scientist named Tony Allison found the clue when he realized how closely the frequency of sickle-cell anemia matched the distribution of malaria in Africa.

47. A Sickle-Cell Safari • To explain the extremely high frequencies of the sickle-cell allele, Dr. Allison figured that the genotypes leading to the disease must be giving some sort of survival advantage to those who have the allele (including carriers of the disease). • Since the sickle-cell allele seemed to be geographically linked to the distribution of malaria, he hypothesized that the sickle-cell gene must somehow increase the carrier’s resistance to malaria. With Watson and Crick’s recent discovery of the structure of DNA, new molecular evidence soon confirmed Dr. Allison’s hypothesis.

48. Evolution in Action • Since malaria is a much bigger threat to survival than sickle-cell anemia, the sickle-cell trait had become prevalent in the areas where its benefits outweighed the negative effects. • Dr. Allison was able to show that the same mutation that led to the sickle-cell trait had occurred at several points in the past in different locations. But it only became prevalent in areas where malaria was widespread. This was an excellent confirmation of the process of evolution occurring in real-time in ways that directly affect humans.

49. Table of Contents 1) What is Evolution? 2) Natural Selection 3) Evidence for Evolution 4) Evolution in Action