19. Use the geological time scale on page 1 to answer the following questions. How many periods make up the Mesozoic era? __ #10. What era do humans live in? How many periods make up the era that we (humans) live in 7 __ #11. WHat proportion of all species that have ever lived has become extinct? __ #12. What is the purpose of the fossil record? __ #13. How long did the Jurassic Period last? __ 14. Explain how Giraffes evolved to have longer necks by using the concept of natural selection. __ #15. Two organisms evolving in response to each other are called? A. Convergent evolution B. Coevolution C.Adaptive radiation D. Genetic drift

3 periods make up the Mesozoic era. ### Humans live in the Cenozoic era, which has 3 periods. ### Approximately 99% of species have become extinct. ### The fossil record shows evidence of past life and evolution. ### The Jurassic Period lasted about 56 million years. ### Giraffes evolved longer necks through natural selection. ### B. Coevolution. Explanation 1. Determine the number of periods in the Mesozoic era The Mesozoic era consists of three periods: Triassic, Jurassic, and Cretaceous. 2. Identify the era humans live in and count its periods Humans live in the Cenozoic era, which includes three periods: Paleogene, Neogene, and Quaternary. 3. Calculate the proportion of extinct species Approximately 99% of all species that have ever lived are now extinct. 4. Define the purpose of the fossil record The fossil record provides evidence of past life forms and evolutionary changes over time. 5. Determine the duration of the Jurassic Period The Jurassic Period lasted approximately 56 million years. 6. Explain giraffe neck evolution using natural selection Giraffes with longer necks could reach more food sources, increasing their survival and reproduction chances. Over time, this trait became more common. 7. Identify the term for organisms evolving in response to each other The correct term is B. Coevolution.