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THE FOSSIL RECORD OBJECTIVES: 17.1 Describe the fossil record. State the information that relative dating and radioactive dating provide about fossils Identify the divisions of the geologic time scale. 1 ________ are scientist who study fossils. They infer what past life forms were like. They also classify ______ organisms. Nest of dinosaur eggs. They group similar organisms and arrange them in ____ in which they lived. 2 The ______ ______ provides evidence about the history of life on Earth. It also shows how different groups of organism, including species, have changed over time. ______ occur in particular order. Some fossils only appear in ____ rock and others appear in more _______ rock. 3 The fossil record shows that ____of all species that have ever lived on Earth are _______. _______ means the species die out. Fossils can be large, _______ preserved animals or they can be as tiny as a _______ of a jaw bone. Most fossils are formed in __________ rock. ________ rock is formed when exposure to rain, _____, wind, and ____ breaks down rock into smaller particles of sand, _____, and clay. 4 As these particles sink to the bottom of a body of _____, dead organism also sink to the bottom and get _______ up. _______ dating: the age of the fossil is determined by comparing its _________ with that of fossils in other layers of rock. An _____ fossil is used to compare relative age. To be an index fossil it must have had a wide _________ _____ and existed only for a short period of time. 5 Relative dating allows paleontologists to ________ a fossil’s age compared with that of other fossils. ___________ dating is the use of half-lives to determine the age of a sample. A __________ is the length of time required for half of the radioactive ______ in a sample to ______. _______-14 is useful for dating fossils younger than _________ years old. 6 To date older rocks, researchers use elements with longer half-lives. _____ decays to the inert gas ______ and has a half-life of 1.26 billion years. 7 Paleontologist use divisions of the _______ time scale to represent evolutionary time. Geologic time begins with the __________ Time. After the Precambrian Time, the basic divisions of the geologic time scale are ____ and _________. 8 Geologists divide the time between the Precambrian and present into ______ eras. In the ________ many vertebrates and invertebrates lived during this time. In the ______ is the Age of the ________, mammals also started evolving. The most recent era is the Cenozoic called the Age of _________ because mammals were common at this time. 9 Eras are subdivide into ________. Look back to slide 8 10 EARTH’S EARLY HISTORY OBJECTIVES: 17.2 Describe how conditions on early Earth were different form conditions today. Explain what Miller an Urey’s experiments showed. State the hypotheses that have been proposed fo how life first arose on Earth. Identify some of the main evolutionary steps in the early evolution of life. 11 Geologic evidence shows that Earth is about __ billion years old. When the Earth was struck by objects as big as _____, it melted. When the Earth melted, its _______ rearranged themselves according to density. These element ultimately cooled to form a solid ______. The less dense elements (H,N) formed the first _________. 12 Earth’s early atmosphere probably contained ________ _________, carbon ______, carbon monoxide, nitrogen, _______ sulfide, and water. 13 ______ and _____ experiments suggested how mixtures of the organic compounds necessary for life could have arisen from simpler compounds present on a primitive Earth. 14 Under certain conditions, large organic molecules can for tiny bubbles called ________ ___________. Microspheres are not cells, but they have some characteristics of _____ systems. They have selectively ________ membranes and can store and ______ energy 15 _________ are single-celled prokaryotic organism that resemble modern bacteria have been found in rocks more than _______. Photosynthetic ______ became common in the shallow seas of the Precambrian. The rise of ________ in the atmosphere drove some life forms to extinction, while other life forms evolved new, more efficient metabolic pathways that used 16 oxygen for respiration. According to the ______________ theory, eukaryotic cells formed a symbiosis among several different prokaryotic organisms. Some time after eukaryotic cells arose, those cells began to reproduce _______. This enabled evolution to take place at a far greater speeds than ever before. A few hundred million years after the evolution of sexual reproduction, evolving life forms crossed over another great threshold: the development of ___________ organisms. 17 EVOLUTION OF MULTICELLULAR LIFE OBJECTIVE: 17.3 Describe the key forms of life in the Paleozoic, Mesozoic, and Cenozoic eras. 18 ______ percent of the Earth’s history occurred in the Precambrian. Rich fossil evidence shows that early in the Paleozoic Era, there was a diversity of _____ life. The _________ Explosion occurred during the early Cambrian period. The first known representatives of most animal ______ evolved. Invertebrates, _________, and trilobites were common 19 Jellyfish Trilobite (arthropods) 20 During the _________ and _______ periods, the ancestors of the modern octopi, squid, and jawless fish appeared. Jawless fish 21 Forerunner of squid and octopi By the ________ Period, some plants like ferns, had adapted to drier areas, allowing them to invade more habitats. ___________ (insects) appeared on land. The Devonian Period is often called the Age of ______, even though the invertebrates were more numerous. Most of the fish of this time had ____, a ____ skeleton, and ______ on their body. ________ appeared in the late Devonian. 22 Devonian fishes 23 During the Devonian, ________ began to invade the land. The first fishes to develop the ability to ______ awkwardly on leglike fins were fully aquatic organisms. Some evolved into the first _____________ (lives part of its life on land and part of its life in water). 24 Throughout the rest of the _______ Era, life expanded over Earth’s continents (reptiles, huge dragonflies, cockroaches, giant ferns). The remains of those ancient plants formed thick deposits of sediment that changed into _____. This is one artist depiction of the __________ Period. 25 At the end of the Paleozoic, many ________ died out. This was a _____ extinction, in which many types of living thing became extinct at the same time. The mass extinction at the end of Paleozoic affected both _____ and ______ on land and in the seas. As much as ____of the complex life in the ocean disappeared (trilobites). 26 Events during the _______ include the increasing dominance of dinosaurs. The Mesozoic is marked by the appearance of _________ plants. Those organism that survived the extinction in the _______, became the main forms of life early in the _______ Period. Mesozoic is often called the Age of _______. 27 __________, was a meat eater that light hollow bones and ran swiftly on its hind legs. _______ also appeared during the Triassic Period. Mammal were very ______. 28 During the ______ Period dinosaurs became the dominant animals on land. __________, was one of the larger dinosaurs of the that period. 29 _____________, was one of the first birds. 30 Reptiles were still the dominant vertebrates throughout the ________ Period. Dinosaurs such as the meat eating _____dominated land ecosystems while flying reptiles and birds soar in the air. 31 32 The Cretaceous also brought new forms of life, including _____ trees, shrubs and small flowering plants that produce ______ in fruit. At the close of the Cretaceous, another ____ extinction occurred. More than ____ of all plant and animal groups were wiped out including the _________. During the Cenozoic Era, mammals evolved __________ that allowed them to live in various environments – on land, in water, and in the air. 33 The Cenozoic is often called the age of ________. During the _______ Period the climate was warm and mild. _____ and dolphins evolved. On land flowering plants and ______ flourished. ______ evolved which encouraged grazing animals 34 During the _______ Period the land masses have reach to about where they are today. The climate was cool, causing a series of ___ ____. 35 The fossil record suggests that the early ______ of our species appeared about ___ mya. According to one _______, members of our species began a series of migrations from Africa that ultimately colonized the world. The first fossils assigned to our own species ,___ ______, appeared 200,000 ya. 36 PATTERNS OF EVOLUTION OBJECTIVE: 17.4 Identify important patterns of macroevolution. 37 Biologists use the term __________ to refer to large-scale evolutionary patterns and processes that occur over long periods of time. More than 99% of all species that have ever lived are now extinct. Several times in Earth’s history, mass extinctions wiped out entire ecosystems. Two reasons for extinction: ______ impact, or ____ activity at the end of the Cretaceous Period. 38 Each disappearance left _________ open and provided ecological opportunities for those organisms that survived. The extinction cleared the way for modern _______ and birds. _______ _______ is when a single species or a small group of species has evolved, through natural selection and other processes, into diverse forms that live in different ways (Darwin’s _______). 39 Darwin’s finches 40 ________ evolution is the process by which unrelated organisms resemble each other. dolphins Great white shark 41 __________ is the process by which two species evolve in response to changes in each other. ________ equilibrium is when there is rapid evolution after long periods of equilibrium. 42