History of the Earth Ch 14
Chapter 14 Vocabulary: • 1. Fossil • 2. Law of superposition • 3. Radiometric dating • 4. Spontaneous generation • 5. Biogenesis • 6. endosymbiont theory
SC.912.L.15.1Ch 14 Explain how the scientific theory of evolution is supported by the fossil record, comparative anatomy, comparative embryology, biogeography, molecular biology, and observed evolutionary change.
How Did Life Begin? The Earth formed about 4.6 billion years ago according to evidence obtained by radiometric dating.
The age of the rocks and the fossils in them can be determined by the position and the amount of radioactive material in the rocks. • Law of superposition
½ life • Compare it to the amount of time it takes for ½ of the carbonation in this bottle to leave… if we know how much time it takes, we could calculate the age of the bottle of soda based on how much carbonation was left in the container.
Radiometric dating • Gives a numerical age • Places rocks and fossils in a time period • Uses isotopes that decay at a constant rate • Uses isotopes that decay very slowly/ have a long ½ life.
fossil • A fossil is any preserved evidence of an organism. • They form best in sedimentary rocks • They can be evidence or an organism, like foot prints or actual remains.
What do fossils tell us and how do we know how old they are? The fossils in the bottom layer of rock are older
Fossils show evidence of change in organisms, what types of organisms lived in each time period and that the complexity has increased over time. • We know how old they are by relative positions and radiometric dating.
Law of superposition! • Youngest are on the top • Oldest are on the bottom • unless they have been disturbed!
The geologic time scale • is a model of the history of Earth showing the major events that occurred along the way.
The longest units of time are eons and include the Precambrian time and Phanerozoic. • The second largest unit of time is called an era and includes the Precambrian, Paleozoic, Mesozoic and Cenozoic. • Each era can be divided into parts called periods and periods may be divided into the smallest parts called epochs.
The history of the earth is broken up into a set of divisions for describing geologic time. • the generally accepted divisions are • eon • era • period • epoch • age
PRECAMBRIAN • SO LONG AGO… • We know little due to deformation of rock layers. • Large areas of Precambrian rock exposed are called shields. North America’s is called the Canadian shield.
Precambrian life • Fossils are rare • Simple organisms with soft bodies • Volcanic activity heat and pressure “erased” the fossil evidence. • Stromatolites blue-green algae were common.
14. Sum up what events occurred in Precambrian time. Makes up almost 90% of Earth’s history, earth formed, first life appeared, autotrophs released oxygen into the atmosphere, Eukaryotes developed. At the end the first animals developed. Simple animals lived in the oceans
Paleozoic Era: Life • trilobites Brachiopods are marine animals that, upon first glance, look like clams
Paleozoic • Lots of fossils • Trilobites index fossil • Invertebrates, worms, jellyfish, snails vertebrates appear • Fish, amphibians • Insects • Reptiles • .
15. Sum up the Paleozoic Era. Explosion of life! Fish, land plants and insects appeared. First tetrapods or land vertebrates appeared reptiles arrived at the end of the Paleozoic
Dinosaurs and other archosaurs, such as the pterosaurs, dominated the land biota. . .
17. Sum up the Mesozoic era. Mammals and dinosaurs appeared. Flowering plants, birds evolved from dinosaurs. The age of the reptiles
Impact theory • No dinosaurs found after the cretaceous- tertiary • What happened? • Possible impact hypothesis
18. What makes scientists think a meteor hit the earth during the cretaceous time period? There is iridium found in the rock layers called the KT boundary. Iridium is found mostly in objects from space, like a meteor.
19. How might a meteor impact cause a mass extinction? The debris could cause global climate changes
20. What other major geological event occurred during the Mesozoic era? Pangaea the single land mass moved so that the continents were roughly in their current position by the end of the Mesozoic era.
Cenozoic • The continents moved to their current positions. • Alps Himalayas formed • Small rodents, early horse, and bats • Ice cap formed • Land bridges formed Ice age • Early ancestors to humans fossils found
21. What is the most recent era? The Cenozoic era • 22. What are the most dominant organisms in the Cenozoic era? Mammals • 23. When did humans arrive on earth? at the very end of the time scale
What life do we associate as occurring during the Mesozoic era? • Dinosaurs
How do we think the extinction of the dinosaurs happened? • giant asteroid hit earth
Section 2 The Origin Of Life • 4. Spontaneous generation • 5. Biogenesis • 6. endosymbiont theory
Hot, meteorites, volcanoes .Minerals in the oldest known rocks suggest that the earth’s atmosphere had little or no oxygen
The primordial soup model and the bubble model propose explanations of the origin of the chemicals of life. Scientists think RNA formed before DNA or proteins formed.