Tuesday : February 21 st Agenda

1. Ms. Fisher 2/21/12 Slide 16 Tuesday: February 21st Agenda 1.) Brief Review from Friday: What do we know about evolution? What is evolution? Evolution  the process by which species gradually change over many generations through natural selection. Natural Selection the driving mechanism behind evolution as explained by Darwin. “Survival of the fittest.” 2.) Continue where we left off on Friday with our PowerPoint and evolution packets! 3.) Show a short clip on Alfred Wallace or Darwin (haven’t decided.) 4.) End with brief recap/ assessment. Do you understand the objective today? Objective for today: Through open discussion and utilization of my PowerPoint, students will begin to understand the process of natural selection and be able to provide evidence for evolution.

2. The Process of Natural Selection Natural selection occurs through the following steps: Overproduction Inherited variation Competition Reproduction

3. The Process of Natural Selection 1) Overproduction 2) Inherited Variation There are genetic differences in any population which result in many combinations of different traits among offspring. These traits are passed genetically from parents to offspring. Parents produce more offspring than will survive. Similarly, plants produce thousands of seeds even though only a few may germinate. 3) Competition 4) Reproduction Those who have a survival advantage are more likely to reproduce and pass on their favorable genes and traits to successive generations, resulting in new adaptations and eventually new species. In any population, organisms must compete for resources to survive. Some individuals have traits which allow them to survive better than others; often referred to as “survival of the fittest”.

4. The Peppered Moth Study The peppered moth study is a perfect case study of natural selection in action. • In the early 1800s, a common moth species in England had light-colored peppered wings, which helped it blend in with the light bark on the trees in the area. • This camouflage trait helped the moth avoid being eaten by birds. • In 1848, a new dark form of the moth began appearing, and by the turn of the century, the dark variety made up the vast majority of the moth population.

5. So what happened? Why did the light moths die off, while the dark ones flourished? • Something must have changed that gave the dark moths a survival advantage. • Scientists recognized that moths were changing in response to a change in their environment. • Extensive air pollution from industrialization was causing the tree bark to darken with coal soot.

6. The Peppered Moth Study 1) Overproduction 2) Inherited Variation Traits for light or dark color are passed on genetically, and moth offspring tend to have traits similar to their parents. However, within a population, some are lighter and some are darker. Peppered moths lay many eggs, and out of those that hatch, the vast majority of them will be eaten and will not survive to lay eggs of their own. 3) Competition 4) Reproduction Since there are so many moths, some will survive, but most will die. The ones that survive tend to be the ones that have traits favorable for survival, in this case, camouflage. The moths that best blend in with their surroundings will be more likely to survive to adulthood and lay eggs, which will yield offspring with those same favorable camouflage traits.

7. Peppered Moth Can you spot the moth? • Keep in mind: • No individual moth ever changed its color. Some moths simply survived better than others, changing the allele frequency, therefore changing the appearance of the color traits among the entire population. • In other words, the light moths didn’t become darker. They just tended to die out, allowing the dark moths to take over!

8. Peppered Moth Can you spot the moth? • Keep in mind: • No individual moth ever changed its color. Some moths simply survived better than others, changing the allele frequency, therefore changing the appearance of the color traits among the entire population. • In other words, the light moths didn’t become darker. They just tended to die out, allowing the dark moths to take over!

9. Carrier Cc Dominant CC Recessive cc When two carriers mate: Ratio of Offspring: Dominant: ¾ 75% Recessive: ¼ 25%

10. Carrier Bb Dominant BB Recessive bb When a recessive & carrier mates: Ratio of Offspring: Dominant: ½ 50% Recessive:½ 50%

11. …And then back again Long after the Industrial Revolution, pollution regulations have helped to clean the soot from England’s trees. And guess what happened to the dark moths… Dark-colored moths started to be eaten more and more as the tree bark lightened, eventually allowing the light moths to repopulate once again.

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

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

14. Evidence For Evolution: I. Geographic Distribution Geographic Distribution  Related native species are found only where they could have migrated on their own. The distribution of ancient fossils, such as Mesosaurus, across the continents is a perfect example of this, although Darwin had no way of explaining how they got there, since plate tectonics had not yet been discovered!

15. Evidence For Evolution: I. Geographic Distribution Madagascar The island of Madagascar is another great example of a set of species that naturally occur nowhere else in the world, for example, about 100 different species of lemur, a group of primates that branched off from earlier monkey-like primates when Madagascar split off from the African mainland about 160 million years ago. AFRICA Madagascar • There are thousands of other species completely unique to this island. • They are all most closely related to the species found along the east coast of Africa, because they share common ancestors.

16. Evidence For Evolution: I. Geographic Distribution Wallace’s Contributions While Darwin was putting together his theory of evolution by natural selection, another British naturalist named Alfred Wallace was doing his own work in the East Indies, where he made some new discoveries about the species there. Pacific Ocean Borneo Java New Guinea Alfred Russel Wallace Australia

17. Evidence For Evolution: I. Geographic Distribution The Wallace Line • Wallace saw that the islands of the East Indies were home to two completely different sets of mammals: monkeys and other placental mammals on the islands to the northwest, and marsupials to the southeast. • It was as if these two groups were divided by some invisible barrier that they could not cross even though the distance was less than 40 km across. • Other species including many birds were clearly cut off by the line as well. Pacific Ocean Borneo Java New Guinea Marsupials Placental mammals Australia

18. Evidence For Evolution: I. Geographic Distribution The Wallace Line The islands on either side of the line made up different geologic formations divided by a deep channel. The two groups, therefore, had never been connected. Even though the climates were almost identical, the flora and fauna were drastically different on either side of the line because the species had evolved in isolation from each other, just as the species on Madagascar had been isolated from the mainland of Africa. Pacific Ocean Borneo Java New Guinea Australia

19. Evidence For Evolution: I. Geographic Distribution Flightless Island Birds Flightless birds are another great example of evidence based on geographic distribution, because in most cases, their ancestry can be traced back to ancient birds who flew to the island from the mainland. • When birds colonize an island with no predators, they often lose the ability to fly over time because they don’t need to fly to survive. • Examples: kiwi, penguin, & the dodo bird.

20. Evidence For Evolution: II. Homologous Anatomy Homologous Anatomy Traits that are similar between species becausethey originate with a common ancestor who had the same trait. • The example above compares the internal structure of a human arm with the forelimb of a whale. • Although the shape of each bone is different, each bone in the human arm has a corresponding match in the whale.

21. Evidence For Evolution: II. Homologous Anatomy Homologous Forelimbs • In fact, every one of these animals has the same basic forelimb structure: a shoulder blade bone, a single humerus, two forearm bones, followed by many wrist bones and digits. • They all trace back to a common ancestor, the earliest tetrapods, which had this basic layout, almost as a template. It’s just been gradually modified for different uses over millions of years.

22. Evidence For Evolution: II. Homologous Anatomy Homologous Feet Looking at these feet up close gives you an idea of how similar they really are, bone for bone. Human (hand) Dog Pig Cow Tapir Horse r — Radius, u — Ulna, a — Scaphoid, b — Lunare, c — Triquetrum, d — Trapezium, e — Trapezoid, f — Capitatum, g — Hamatum, p — Pisiforme

23. Evidence For Evolution: II. Homologous Anatomy Homologous Feet In the case of the horse, the entire middle digit which has been modified into the lower part of the leg, while the other digits became smaller and smaller until they are completely gone. A horse’s hoof corresponds to our middle fingernail while the knee actually matches up to our wrist bones. Horse Tapir Human

24. Evidence For Evolution: II. Homologous Anatomy Other Examples Remember, homologous traits are adaptations that are similar between species because both species share an ancestor with the adaptation. For example, the following species all have wings, because they evolved from an earlier bird ancestor with wings. In this case, the three species have diverged from each other for long enough that their wings have gradually taken on different uses.

25. Evidence For Evolution: II. Homologous Anatomy Convergent Evolution Bird wing • Not all similarities between species are homologous, however, because not all traits are inherited from a shared ancestor. • Although both birds and bats use wings to fly, when you look at their anatomy, it’s obvious that their wings are completely different. • The similarity is not due to common ancestry. Rather, birds and bats have undergone convergent evolution. Bat wing

26. Evidence For Evolution: II. Homologous Anatomy Convergent Evolution Convergent Evolution  Bird wing • When two species evolve a similar adaptation not because of common ancestry but because they have become adapted to a similar environment, or use the trait for a similar function. • In other words, they have both “converged” on the same adaptation in their own way. Bat wing Birds and bats have both evolved wings because they both use them to fly. Rather than “homology”, this is called an “analogous trait” or simply, an analogy.

27. Evidence For Evolution: II. Homologous Anatomy Homology vs. Analogy Diagram 1 below illustrates how the eagle and the penguin evolved their wings from earlier birds. Diagram 2 shows how birds and bats evolved their wings separately. species A species B species A species B adaptation adaptation Homologous traits Analogous traits adaptation Diagram 1 Diagram 2

28. Evidence For Evolution: II. Homologous Anatomy More Examples Four legs: Homology or Analogy? Homology: This is a homologous trait because all of these species evolved from the earliest tetrapod, which also had four legs.

29. Evidence For Evolution: II. Homologous Anatomy More Examples Two eyes: Homology or Analogy? Homology: This is a homologous trait because all vertebrates have two eyes. This allows some animals to see almost 360°, and it allows humans to see in 3D.

30. Evidence For Evolution: II. Homologous Anatomy More Examples Protruding eyes: Homology or Analogy? Analogy: This is an example of convergent evolution because not all reptiles and amphibians have this trait. Frogs and alligators have evolved the same adaptation independently, but for similar use: to see above the water’s surface.

31. Evidence For Evolution: II. Homologous Anatomy More Examples Analogy: Many placental mammal species have corresponding marsupial species, which occupy the same ecological niche on other continents. They are not related, however, and their similarities are due to similar environments and ways of life. This is, once again, convergent evolution at work. Placentals Marsupials All of the placental mammals are more closely related to each other than to any marsupial, and vice versa.

32. Evidence For Evolution: II. Homologous Anatomy What does it mean? Evidence for evolution: Both homologous and analogous traits are excellent evidence for evolution, because they show how different species are related and how they evolved their adaptations for survival. Homologous traits Analogous traits

33. Alfred Wallace http://www.youtube.com/watch?v=9xiGfpokTvI 2nd known man who agrees with the theory of evolution! Darwin http://www.youtube.com/watch?v=n3265bno2X0

34. Ms. Fisher 02/21/12 Assessment: Objective for today: Through open discussion and utilization of my PowerPoint, students will begin to understand the process of natural selection and be able to provide evidence for evolution. What are the four steps of natural selection? • Overproduction • Inherited Variation • Competition • Reproduction What type of evidence do we have that supports the theory of evolution? • Fossils – Migration Patterns • Homologous Anatomy