1. EVIDENCE OF EVOLUTION

2. I. THE FOSSIL RECORD

3. I. THE FOSSIL RECORD Importance
Provides the best proof of the history of life showing how extinct species have lead to today’s species
“Lucy”, 3.2 MY
Archaeopteryx, 150 MY

4. Becoming a Fossil (Part 1) (excerpts from Bill Bryson’s book)
In order to become a fossil, several things must happen. First, you must die in the right place. Only about 15% of rocks can preserve fossils, most being sedimentary rocks. So the deceased usually needs to become buried in sediment, the best chance is being buried underwater and decomposing without exposure to oxygen, allowing the bones and hard parts, and sometimes soft tissue, to be replaced by dissolved minerals, creating a petrified stone version of itself. Then as the sediments in which the fossil lies are pressed, folded and pushed about by Earth’s processes, the fossil must somehow maintain an identifiable shape. Finally, after tens of millions to hundreds of millions of years of being hidden away, it must be found and recognized as something worth keeping.
Why do you think the fossil record (almost 95% of it ) is mostly marine life?
Formation of Fossils (Summary)
Organism is buried in sediment under water (sometimes: ice, amber or tar)
Hard parts (bone& shell) are slowly replaced by minerals dissolved in water

5. The Story Fossils Tell What type of rock is it?
Provide an observation & an inference about this fossilized animal.
If this fossil was found in central Cumberland County, PA, how old is it? (Use the Geologic Map on next slide)

6. What type of rocks are most common in Bucks County?
What age fossils might you find in Bucks County?

7. Transitional Species (Common Ancestors)
Location where two species evolutionary path connect on the “tree of life”
Scientists search for common ancestors in the fossil record to show the evolutionary connection between species & how they change over time.

10. Transitional Species Example – Whale Evolution
* Read more on Whale Evolution in the textbook (pgs )
* Whale Evolution video clips

11. Becoming a Fossil (Part 2) (excerpt from Bill Bryson’s book)
It isn’t easy to become part of the fossil record. The fate of nearly all living things (over 99.9% of them) is to decompose to nothing. Even if you make it into the small pool of organisms, that don’t breakdown to nothing, the chances of being fossilized are very small. Only about one bone in a billion, it is thought, ever becomes fossilized. If that is so, it means that the complete fossil legacy of all the Americans alive today (that’s about 300 million people with 206 bones each) will only be about 50 bones, one quarter of a complete skeleton. That’s not to say that any of these bones will actually be found. Fossils are in every sense extremely rare. Most of what has lived on Earth has left behind no record at all. It has been estimated that less than 1 species in 10,000 has made it into the fossil record. What we have in the fossil record is the smallest of samplings of all the life that has existed on Earth.

12. Completeness of the Fossil Record?

13. How do we know how old a fossil is? TWO Ways to Date Fossils
Relative age dating
approximation of dating by comparing rock layers
Absolute age dating
Precision of dating by measuring radioactive decay of elements in rock

14. Relative Age Dating
Relative age dating follows the Law of Superposition (older rocks are found under younger rocks)
Exception to the rule – unconformities (break in the rock record)
Index Fossil – an organism that lived during a specific period of time and is abundant.

15. Absolute Age Dating
Radioactive Elements: unstable atoms giving off radiation (protons & neutrons) to become stable.
Ex: Uranium-238 & Carbon-14
Radioactive dating: Radioactive decay (going from unstable to stable) occurs at a constant rate called a half life. Each radioactive element has its own half life.
Half life: the amount of time it takes for half the radioactive atoms in a substance to become stable.
Examples:
Uranium-238 has a half-life of 4.5 billion yrs (becomes Lead)
Carbon-14 has a half-life of 5730 yrs (becomes Nitrogen)
*****PUT ANOTHER EXAMPLE ON THE BOARD
Example of Absolute Age Dating
Red Dots are radioactive elements
Green Dots are stable elements

16. II. Comparative Anatomy
Homologous Structures
Vestigial Structures

17. Homologous Structures
body parts from different organisms that have the same structures, but different functions, supporting the idea of a shared common ancestor
EX: vertebrate forelimb bones

20. Homologous Structures
Analogous Structures
Similar in anatomy
Dissimilar in anatomy
Doing dissimilar functions
Doing similar functions
Develop in related animals
Develop in unrelated animals
Inherited from a common ancestor
Not inherited from recent common ancestor
Similar developmental pattern
Developmental pattern is not similar
Similar structure and Origin
Dissimilar in structure and origin

21. Homologous OR Not?
Cephlopod
Cnidarian
Arthopod
Mammals

24. Homologous OR Not
As already discussed Homologous Structures between species provide evidence that the species shared a common ancestor, as shown in the mammal forelimb examples, displaying the same structure but adapting different functions for their forelimbs. Some times in nature, unrelated species will evolve similar functions through different evolutionary paths using unrelated structures. These types of structures are called Analogous Structures and they do not show evidence of evolution from a common ancestor.

25. Which limb is NOT homologous in each set? Why?
Human
Lizard
Octopus B
Bird
Whale
Grasshopper
Lizard
Human

26. Common Ancestors
Homologous structures are inherited from common ancestors. The octopus limb could only be homologous to the lizard limb if they both inherited the limb from a common ancestor. This family tree shows how the octopus is related to vertebrate limbs. Vertebrate limbs and octopus limbs evolved independently after their point of common ancestry, so they were not inherited from a common ancestor. Therefore, they are not homologous, they are considered analogous. The same is true of the grasshopper leg.

27. Homologous OR Not GAME
Helpful Hint: For each set of pictures, ask yourself if the structure or adaptation evolved between the species from a shared common ancestor OR did the structure evolve independently between the two species showing no common ancestor linking the structure or adaptation together.
DIRECTIONS: Keep Score of how many you and your group get correct.

28. 1. Are the wings of a bat (mammal) and the wings of a robin (bird) homologous?

29. 2. Fins of a shark (fish) and the fins of a dolphin mammal?

30. 3. The limbs of an eagle and the limbs of a penguin?

31. 4. Wings of a dragon fly and the wings of a butterfly?

32. 5. Are all of these different leaves Homologous?

33. 6. No limbs on a water snake (reptile) and no limbs on an eel (fish)?

34. 7. Opposable thumbs of the primitive primate, bush baby, and our opposable thumbs?

35. 8. The front teeth on a beaver and the tusks on an elephant?

36. 9. The scales on a brown trout (fish) and the scales on a lizard (reptile)?

37. 10. Gliding adaptation of the marsupial sugar glider from Australia and the placental gliding squirrel of the Americas?

38. Answers No (they do not share a common ancestor with wings)
No (they do not share a common ancestor with fins)
Yes (both are birds that have adapted different uses for their wings)
Yes (both are insects that evolved from insects with wings)
Yes (all are types of modified leaves from different plants)
No (they do not share a common ancestor without limbs)
Yes (both are in the primate family which all have opposable thumbs)
Yes (both are mammals with modified front teeth)
No (they are not closely related, fish and reptile, scales evolved independently)
No (they are different groups of mammals, placental and marsupial, that do not share gliding ancestors)

39. Vestigial Structures
structures that are found in an organism but appear to serve no function (reduced in size)
they are remnants of an organism’s evolutionary past
Ex: Whales and snakes have pelvic bones; manatees “sea cows” have finger nails on their fins
Humans?
ear muscles
canine teeth
Goose bumps
appendix
Tail bone
Wisdom teeth

41. The same muscles (arectores pilorum) that enable a cat to do this:
also enable us to do this:

42. III. Comparative Embryology
similarities in the developmental pattern of organisms exist because of a common ancestor
vestigial gill slits/pouches
bony tail
covered in a fine hair
Two chambered hearts
Human embryo Pig embryo Chicken embryo

43. Comparative Embryology in Vertebrates
All vertebrates are similar in early stages of development.
Differences accumulate as development continues.
New development instructions are added to old instructions inherited from ancestors.

44. Comparative Embryology in Vertebrates
All vertebrates are similar in early stages of development.
Differences accumulate as development continues.
New development instructions are added to old instructions inherited from ancestors.

45. Human Embryology

46. IV. Comparing Genetics
An organism’s evolutionary history is held in their DNA sequence (genetic code)
If a species changes, their DNA changes
Genetic testing compares the similarity of DNA between organisms
The more closely related the species are to each other the more similarities they share in their DNA
Ex. Chimpanzees & Humans have over 98% the same DNA

47. What is DNA?

48. Cytochrome c
Cytochrome c is a protein organisms need for respiration. Proteins are made of an amino acid sequence that is determined from our DNA sequence. So if the amino acids in the cytochrome c protein is slightly different between species it also means their DNA is slightly different. Virtually every organism uses cytochrome c; however, each species’ cytochrome c differs slightly from other species. The differences among cytochhrome c exist in the amino acid sequence which were produced by mutations in the species DNA. These mutations occurred after the ancestors of the living species diverged. Therefore, if two species shared common ancestors until fairly recently, their DNA and proteins are likely to be more similar.