Name ______Class ______Date ______

Evolution Unit: “Deep Time” Answers

Basics

We will explore the PBS website on “Deep Time.”

http://www.pbs.org/wgbh/evolution/change/deeptime/index.html

Go to this web site. Read the introduction. Figure out how to navigate and explore the site. Answer the questions below.

Introduction

1. What is “Deep Time?” Evolution is documented in layers and layers of rocks deposited over 4.6 billion years. The stretch of geologic history is called “deep time.” It is hard to understand, but we must try.

2. How old is the Earth?

The Earth was formed 4.6 billion years ago, bya.

3. What does deep time have to do with evolution? Evolutionary change is slow. We need to understand deep time to understand the history of life on Earth and to understand the rate of evolutionary change.

4. The web site looks at three types of events in Earth history. One of them is “Geology.” Significant geological events are noted by green triangles. What is the type of event indicated by blue circles?

“Transformation” events.

5. What is the type of event indicated by yellow squares.

“Extinction” events.

6. Explore the “Transformation” circles. What does the web site mean by the term “Transformation.” Transformation means changes in the forms and functions of living things. “Life’s Greatest Hits.”

7. What does the web site mean by "Extinction?" Most life that has ever lived on Earth is extinct. Some of this extinction happens as background events, slowly and somewhat uniformly over time. But occasionally in Earth history there are “Mass Extinctions.” Episodes of high levels of extinction in Earth history

Evolution Unit: Deep Time, Page 1, Printed 2/3/12 Precambrian Eon

8. What period of time is the Precambrian Eon?

4550 – 543 million years ago, mya.

9. Name the three eras in the Precambrian Eon.

Hadean, Achaean, and Proterozoic.

10. Explore the geology triangles. Read every one from oldest to youngest. How old are Earth’s oldest rocks and where are they found?

4055 mya, Canada’s Northwest Territories.

11. How are “red beds” formed? 2,000 mya The reaction of oxygen with iron in exposed rocks begins producing “red beds” of rusted rocks.

12. How old is the oldest evidence of life on Earth?

3,850 mya.

13. What is the oldest evidence of life on Earth?

Rocks in Greenland show the earliest evidence of biological activity, carbon isotope ratios that occur only if life has been present.

14. How old is the oldest evidence of eukaryotes?

2700 mya. Traces of oil containing sterols, fatty acids that hold cell membranes together and are only produced by eukaryotes.

15. How old are the oldest metazoan fossils on Earth? 900 mya. Metazoans are multicellular animals.

16. What is the name of the one extinction on this portion of the timeline? Venian.

17. What forms of life were affected by this extinction? Some single-celled algae and soft-bodied animals

18. How severe was this extinction? Severity = 3 on the 1 – 3 scale, less than 20% of families die out.

Evolution Unit: Deep Time, Page 2, Printed 2/3/12 Paleozoic Era

19. When did oxygen get to present day levels?

400 mya. 21% of the atmosphere.

20. What is Pangaea?

Pangaea is a supercontinent. All of the other continents on Earth merged to form one big land mass.

21. When did Pangaea form?

280 mya.

22. What is a chordate? Chordates are animals with a central nervous chord that runs along a stiff yet flexible rod down the middle of the back. This chord is called a notochord. Chordates includes the vertebrates, animals with a backbone.

23. How old is the oldest chordate fossil?

535 mya.

24. When did vertebrates first come on land? What vertebrates were these?

Amphibians came on land at 375 mya.

25. When did conifers begin to dominate the land?

300 mya.

26. What is it about conifers that allowed them to spread so widely? Conifers are a class of plant that produce “naked seeds” that develop outside of the plant and without the need of water. This ability to reproduce on dry land allowed conifers to spread widely.

27. What is the proper name of the “Mother of all Extinctions? When did it occur?

End Permian. Sometimes called the “Permian-Triassic.”

28. What are the hypotheses for the extinction of the previous question? Volcanism, glaciation, sea-level changes, ocean chemistry change, global warming, meteor impact

Evolution Unit: Deep Time, Page 3, Printed 2/3/12 Mesozoic Era

29. What is the name of mammals’ reptilian ancestors?

The cynodonts.

30. How old are the oldest dinosaurs? Specialized teeth (canines and incisors), a hard palate that enabled simultaneous breathing and eating, upright posture, and (perhaps) warm-bloodedness.

31. What did birds evolve from?

Small, bipedal theropod dinosaurs.

32. When did birds evolve?

150 mya.

33. What is an angiosperm?

An angiosperm is a flowering plant.

34. When do angiosperms show up in the fossil record?

130 mya.

35. Name the major geologic event that happened 200 mya?

Pangaea starts to break apart.

36. What happened 65 mya? Name the event and provide at least three relevant details.

The End Cretaceous extinction event. Also called the Cretaceous-Tertiary or K-T event. About 60 – 80 % of all species go extinct, including the dinosaurs. Possibly caused by meteor impact, volcanic activity, or sea-level change. It is the second most severe extinction event in Earth history.

37. What forms of life were affected? Just about everything. Fish and plankton sustain a major hit, but survive. Up to 35 & of land plants do not survive. Dinosaurs are the poster child. Pterosaurs, marine reptiles, and several mollusk groups perish. Groups that suffer heavy losses, but survive, include mammals, amphibians, crocodiles, turtles, and insects on or near land, and diatoms, foraminifera, and dinoflagellates in marine waters.

38. How severe was this event? Severity = 1 on 1 – 3 scale. The second most severe in Earth history.

Evolution Unit: Deep Time, Page 4, Printed 2/3/12 Cenozoic Era

39. What is the age range of the Cenozoic era?

65 – 0 mya.

40. Choose one geologic event and describe it in detail

Answers will vary.

41. Choose one transformation event and describe it in detail.

Answers will vary.

42. Write down the basic details of the Late Pleistocene extinction event.

The late Pleistocene extinction is uncharacteristic of other mass extinction events. Extinction takes place at different times on different continents, but always targeting a specific kind of animal. Climate change alone probably did not cause it. Over about 40,000 years, 200 or more groups of large herbivores are wiped out. With their prey absent form the food chain, many carnivores, and scavengers also die off. Temperature fluctuates throughout the last ice ages, but eh fossil record doesn’t not indicate an unusually concentration of death among smaller plant or animals. The extinctions coincide with the arrival of humans to a continent.

Optional Advanced Work

I. Write several good, clear, multiple choice questions that would be good quiz questions for this activity.

II. Choose any one event: Geologic, Transformation, or Extinction that particularly caught your attention. Do research on it. Prepare a five-minute presentation to give to the class. Have visually aids and/or an activity.

III. How do we know that the Earth is 4.6 billion years old? Do research to find out how scientist determined this number. Discuss with the instructor a way to present this information.

IV. Design a “Deep Time” bulletin board.

Evolution Unit: Deep Time, Page 5, Printed 2/3/12