Chapter 12 Science Skills Worksheet.pdf
Chapter 12 Science Skills Worksheet.pdf
Chapter 12 Science Skills Worksheet.pdf
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Name Class Date<strong>Skills</strong> <strong>Worksheet</strong>History of LifeINTERPRETING TIMELINESThe timeline below shows some of the physical events that have helped to shapelife on Earth. Some major advances in the evolution of life are also shown. Usethe timeline and the “Life Events” (a–d) listed below the timeline to completeitems 1–4.In each numbered space in the timeline, write the letter of the most appropriateevent from the “Life Events” below the timeline.Timeline of Life on EarthApproximatenumber ofyears ago Life events Physical events4.6 billion Earth forms and surface cools.2.5 billion Oxygen gas is released into seas,1. then enters atmosphere.1.5 billion The first eukaryotes evolve.700 million The first multicellular organisms evolve.444 million Protective ozone shield in place2. in upper atmosphere416 million Amphibians are the first vertebrateson land.318 million Widespread drought3.299 million Mass extinction251 million Dinosaurs appear.146 million Mass extinction65 million Earth’s climate becomes moist.4.1.8 million The first humans appear.PresentMore than half of tropical rain forestsand many species destroyedLife Eventsa. Reptiles appear.b. Mammals become dominant on land.c. Plants appear on land.d. Cyanobacteria first begin to carry out photosynthesis.Copyright © by Holt, Rinehart and Winston. All rights reserved.Holt <strong>Science</strong>: Biology 23 <strong>Science</strong> <strong>Skills</strong> <strong>Worksheet</strong>s
Name Class DateHistory of Life continuedUse the timeline on the previous page to answer questions 5–9.Read each question, and write your answer in the space provided.5. Name an organism that is seriously damaging Earth’s ecosystems, anddescribe some of the damage being caused by this organism.6. What are some factors that have caused the dominant life-forms on Earth tochange over time?7. Is another major mass extinction likely? Explain.8. What environmental changes affected the evolution of reptiles?9. What effect did photosynthetic cyanobacteria have on Earth’s environment?Copyright © by Holt, Rinehart and Winston. All rights reserved.Holt <strong>Science</strong>: Biology 24 <strong>Science</strong> <strong>Skills</strong> <strong>Worksheet</strong>s
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