Chapter 25 Homework

Fossil Record The fossil record provides a glimpse into the evolution of life on Earth. It shows that there have been remarkable changes in the kinds of organisms that have been abundant at different times during the past 3.5 billion years. Part A - The history of life according to the fossil record Classify each event in the history of life into the appropriate eon or era. Drag each phrase to the appropriate bin.

Part B - Radiometric dating The age of fossils can sometimes be determined by radiometric dating, which is based on the constant rate of decay of radioactive isotopes. The time required for half of a radioactive isotope to decay is called the half-life of that isotope. For example, the isotope carbon-14 has a half-life of 5,730 years. Suppose it is determined that a fossilized leaf contains 12.5% of the carbon-14 that was present when the fossil formed. How old is the fossil? Express your answer numerically.

Likelihood of finding a fossil Only a very small percentage of organisms actually fossilize. Based on the information in the table below, rank the likely abundance of fossils of organisms A-E. Description Organism A Organism B Organism C Organism D Organism E soft body with no skeleton × × × × soft body covered by hard shell × lives where sediment is not being deposited × × lives near the shore of a river or ocean × × × large population and long existence × × × small population and short existence × × lives where oxygen content is low × × × lives where oxygen content is high × × Rank the fossils of organisms A-E from most common to least common. If two fossils have the same commonness, overlap them.

Part A The oldest fossils usually _____.

Part A Radiometric dating _____.

Part A If a fossil is encased in a stratum of sedimentary rock without any strata of volcanic rock (for example, lava or ash) nearby, then it should be _____.

Part A The atmosphere of early Earth probably contained no O2 until the emergence of organisms that _____.

Part A Evolution works by _____.

Part A Many species of snakes lay eggs. However, in the forests of northern Minnesota, where growing seasons are short, only live-bearing snake species are present. This trend toward species that have live birth in a particular environment is an example of _____.

Part A The planet is currently facing its _____ mass extinction event.

Part B Why didn't the dinosaurs go extinct during the Permian extinction?

Part C You are a researcher studying a group of organisms that all disappeared during the Permian extinction. What do you study?

Part D As more carbon dioxide is added to the atmosphere, which of the following is most likely to happen?

Part E Which group of animals is currently facing the greatest threat from climate change?

Part A Fossilized stromatolites

Part A A paleontologist finds a new tyrannosaur in a site she is excavating, and wishes to date the fossil. What is the most likely method she will use?

Part A It is most strongly believed that the descendants of American Indians arrived in North America by doing which of the following?

You are an archaeologist and you find human remains with a mitochondrial DNA lineage of X. Which of the following is true?

Part C You are a geneticist studying the random changes in burrowing owl DNA from one generation to the next. What are you researching?

Part D Ancient American Indian skulls provide evidence that which of the following is true?

Part E Which of the following is true regarding your mitochondrial DNA?

Part A The questions below refer to the following description and figure. The figure below represents a cross section of the sea floor through a mid-ocean rift valley, with alternating patches of black and white indicating sea floor with reversed magnetic polarities. At the arrow labeled "I" (the rift valley), the igneous rock of the sea floor is so young that it can be accurately dated using carbon-14 dating. At the arrow labeled "III," however, the igneous rock is about one million years old, and potassium-40 dating is typically used to date such rocks. Note: The horizontal arrows indicate the direction of sea-floor spreading, away from the rift valley. Which section of sea-floor crust should have the thickest layer of overlying sediment, assuming a continuous rate of sediment deposition?

Part A The questions below refer to the following description and figure. The figure below represents a cross section of the sea floor through a mid-ocean rift valley, with alternating patches of black and white indicating sea floor with reversed magnetic polarities. At the arrow labeled "I" (the rift valley), the igneous rock of the sea floor is so young that it can be accurately dated using carbon-14 dating. At the arrow labeled "III," however, the igneous rock is about one million years old, and potassium-40 dating is typically used to date such rocks. Note: The horizontal arrows indicate the direction of sea-floor spreading, away from the rift valley. If a particular marine organism is fossilized in the sediments immediately overlying the igneous rock at the arrow labeled "II," at which other location, labeled A-E, would a search be most likely to find more fossils of this organism?

Part A Which of the following organisms would be most likely to fossilize?

Part A Which of the following would be LEAST likely in the fossil record?

Part A What is true of the fossil record of mammalian origins?

Part A How does continental drift affect living organisms?

Part A According to the theory of sea-floor spreading, oceanic islands, such as the Hawaiian Islands depicted in the figure above, form as oceanic crustal plates move over a stationary "hot spot" in the mantle. Currently, the big island of Hawaii is thought to be over a hot spot, which is why it is the only one of the seven large islands that has active volcanoes. What should be true of the island of Hawaii? 1. Scientists in search of ongoing speciation events are more likely to find them here than on the other six large islands. 2. Its species should be more closely related to those of nearer islands than to those of farther islands. 3. It should have a rich fossil record of terrestrial organisms. 4. It should have species that are not found anywhere else on Earth. 5. On average, it should have fewer species per unit surface area than the other six islands.

Part A Hawaii is the most southeastern of the seven largest islands and is also closest to the sea-floor spreading center from which the Pacific plate originates, which lies about 5600 km further to the southeast. Assuming equal sedimentation rates, what should be the location of the thickest sediment layer and, thus, the area with the greatest diversity of fossils above the oceanic crust?

Part A On the basis of their morphologies, how might Linnaeus have classified the Hawaiian silverswords? Linnaeus would have _____.

Part A A hypothetical island lies far from any other landmasses. There are many different types of plants, but only one animal, a beetle, that can fly or walk from plant to plant and feeds by chewing leaves. Given that the beetle is not exploiting all of the resources on the island, which morphological change would be most likely to trigger an adaptive radiation of the beetles?

Part A Upon being formed, oceanic islands, such as the Hawaiian Islands, should feature what characteristic, leading to which phenomenon?

Part A What was the "oxygen revolution," which took place 2.3 billion years ago?