Act. 99: A Whale of a Tale Challenge How are modern and fossil skeletons used to investigate evolution? KeyVocabulary: Fossil Record Natural Selection

Read the Introduction on page 48 Getting Started… Are whales mammals or fish? How do you think whales evolved: do you think some mammals evolved from land to sea or that a type of fish evolved to have mammalian traits? What type of evidence could help you answer this question?

Doing the Activity: Read “The Fossil Exhibit” on page 49 Follow the procedure on pages 49-50. Make sure you copy the data table into your notebooks in step #1

Comparing Skeletons Similarities Differences Group 1 Skeletons: __A, M____________ Group 2 Skeletons : __B, D, O________ Group 1 skeletons compared with Group 2 skeletons.

What can be inferred about the evolution of whales based on the physical characteristics? How can we decide which was the ancestor of modern whales, Skeleton D or Skeleton B?

Evolution of whales has involved the extinction of some groups and the formation of others by branching - speciation The evolution of aquatic traits in this lineage of mammals took about 20 million years How are whales and cows related then?? Whales and cows share a common ancestor known as paraxonions. It is similar to a cousin relationship!

Is there a trend in this evolutionary tree toward evolving to live in water? Not only whales evolved from the common ancestors on this evolutionary tree, but also cows, sheep, pigs, and hippopotamuses

Analysis #1a Skeletal changes in the evolution of whales” External hind limbs are lost and the bones either greatly reduced or lost entirely; The skull changes size and shape Forelimbs turn into fins Tail elongates due to loss of the pelvis and external hind limbs The tail vertebrae become thicker and larger The enlarged neck vertebrae shrink (indicating reduced need)

Analysis #1b Inferences about changes in habitat because of skeletal changes: These skeletal changes indicate a transition from predominantly land-dwelling animals to ones that lived partly in shallow water, and eventually to animals with an exclusively aquatic habitat.

Analysis #3 Comparing skeletons can show similarities and differences among species. The numbers of these similarities and differences allow scientists to infer relationships among different animals/groups of organisms If you have enough fossils, an evolutionary tree can be made.

Analysis #5 Student answers will vary with their opinions

Great Transformations

Homework Analysis Question # 2 Use Natural Selection to describe how/why ONE of these changes occurred. Changes: Teeth, Rib Cage, Length, Limbs, Vertebrate, Skull shape/size etc.