Chapter 15

1. Chapter 15 Tracing Evolutionary History 0

2. 0 0 Concept Check • The timeline at the bottom of the screen represents the history of life on earth. Which of the marked periods represent the oldest fossil eukaryotes? • A. • B. • C. • D. A B C D Earliest evidence of life Pre-Cambrian Period Paleozoic Mesozoic Cenozoic Present

3. 0 0 Answer • The timeline at the bottom of the screen represents the history of life on earth. Which of the marked periods represent the oldest fossil eukaryotes? • B. A B C D Earliest evidence of life Pre-Cambrian Period Paleozoic Mesozoic Cenozoic Present

4. 0 0 Concept Check • The timeline at the bottom of the screen represents the history of life on earth. Which of the marked periods represent the Cambrian explosion? • A. • B. • C. • D. A B C D Earliest evidence of life Pre-Cambrian Period Paleozoic Mesozoic Cenozoic Present

5. 0 0 Answer • The timeline at the bottom of the screen represents the history of life on earth. Which of the marked periods represent the Cambrian explosion? • C. A B C D Earliest evidence of life Pre-Cambrian Period Paleozoic Mesozoic Cenozoic Present

6. 0 0 Concept Check • The timeline at the bottom of the screen represents the history of life on earth. Which of the marked periods represent the beginning of photosynthesis and the accumulation of oxygen in the atmosphere? • A . • B. • C. • D. A B C D Earliest evidence of life Pre-Cambrian Period Paleozoic Mesozoic Cenozoic Present

7. 0 0 Answer • The timeline at the bottom of the screen represents the history of life on earth. Which of the marked periods represent the beginning of photosynthesis and the accumulation of oxygen in the atmosphere? • A. A B C D Earliest evidence of life Pre-Cambrian Period Paleozoic Mesozoic Cenozoic Present

8. 0 0 Concept Check • The timeline at the bottom of the screen represents the history of life on earth. Which of the marked periods represent the extinction of the dinosaurs? • A. • B. • C. • D. A B C D Earliest evidence of life Pre-Cambrian Period Paleozoic Mesozoic Cenozoic Present

9. 0 0 Answer • The timeline at the bottom of the screen represents the history of life on earth. Which of the marked periods represent the extinction of the dinosaurs? • D. A B C D Earliest evidence of life Pre-Cambrian Period Paleozoic Mesozoic Cenozoic Present

10. Thinking like a scientist • Carbon-14 has a half-life of about 5730 years. Approximately, how old of sample can you reliably date using C-14 methods? • 11,000 years • 25,000 years • 35,000 years • 40-50,000 years

11. Answer • Carbon-14 has a half-life of about 5730 years. Approximately, how old of sample can you reliably date using C-14 methods? • 40-50,000 years

12. Thinking like a scientist • Which of the following specimens could you best date using Carbon-14 radiometric techniques? • Giant ground sloth dung from the last ice age. • Early Cenozoic mammal fossils. • Dinosaur bones from Colorado • Early hominid fossils from East Africa

13. Answer • Which of the following specimens could you best date using Carbon-14 radiometric techniques? • Giant ground sloth dung from the last ice age.

14. Thinking like a scientist • You’ve sent your pile of ground sloth dung off to the lab for analysis. The report that you receive from the lab indicates that your sample has only about 10% of the carbon-14 you’d expect in a modern sample. About how old is your dung sample? • 6,000 years old. • 12,000 years old. • 18,000 years old • 24,000 years old

15. Answer • You’ve sent your pile of ground sloth dung off to the lab for analysis. The report that you receive from the lab indicates that your sample has only about 10% of the carbon-14 you’d expect in a modern sample. About how old is your dung sample? • 18,000 years old

16. StronglyA B C D E Strongly DisagreeAgree 0 Science and Society • The science of cladistics is reshaping phylogenetic trees. Along with this analysis cladists are also proposing new taxonomic terminology to reflect the new understandings of systematics. This terminology at this time is rather challenging and not at all like the terminology that the general public is familiar with. For instance, most people think that vertebrates fall into the classes of fish, amphibians, reptiles, birds and mammals. These categories are inconsistent with cladistic analysis. Should classical terms be kept despite their inaccuracies?

17. StronglyA B C D E Strongly DisagreeAgree 0 Science and Society • Some estimate the extinction of species (mostly due to habitat loss) to be on the order of hundreds of species a year. Analysis of the fossil record indicates that normal background extinction rates are on the order of a few species a year. For this reason, some scientists have suggested that the earth is currently experiencing a major extinction event much like the great extinctions of the past—only this one is primarily human caused. Do you agree that the current extinction rates are cause for alarm?

18. StronglyA B C D E Strongly DisagreeAgree 0 Science and Society • Some people rationalize species loss as organisms that can not adapt go extinct—it’s part of natural selection. Do you agree that species extinction due to human causes are natural events?