Outline: Chapter 16.1: Fossils
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Fossils provide evidence about ancient life on Earth. They form when plant or animal remains are rapidly buried and preserved before decay can set in. There are many types of fossils including carbon films, molds, casts, and trace fossils. Paleontologists study fossils to learn about extinct organisms and past environments. Fossils indicate that conditions on Earth have changed dramatically over time, with evidence that seas once covered continents and climates were much warmer or colder in the past.
Outline: Chapter 16.1: Fossils
- 1. Chapter 16 Lesson 1: Fossils p564-572 page 1 Vocabulary Fossil (565) the preserved remains or evidence of ancient living things Catastrophism (565) the idea that conditions and organisms on Earth change in quick, violent events Uniformitarianism (566) a principle that states that geologic processes that occur today are similar to those that have occurred in the past Carbon Film (568) the fossilized carbon outline of an organism or part of an organism Mold (569) the impression in a rock left by an ancient organism Cast (569) a fossil copy of an organism made when a mold of the organism is filled with sediment of mineral deposits Trace Fossil (569) the preserved evidence of the activity of an organism Paleontologist (570) scientists who study fossils Evidence of the Distant Past Just like old photos, fossils provide us with clues about Earths past Fossils are the preserved remain or evidence of ancient living things Catastrophism Many fossils represent plants and animals that are _____________________ In the past many scientists believed that a single, sudden, catastrophic ________________ killed the organisms that become fossil Catastrophism is the idea that conditions and organisms on Earth change in______________, violent events o These include large volcanic eruptions and widespread ____________________. Scientists eventually __________________ with catastrophism because Earths history is full of violent events Most people who supported catastrophism thought that Earth was only a ____________thousand years old Uniformitarianism In the 1700s, James ________________ rejected the idea of catastrophism Hutton thought that the processes responsible for changing the _________________ could also shape Earths surface o For example, he thought that erosion caused by streams could also wear down ____________________________. o He realized that these processes would take a long ______________________, and proposed that Earth was much older than a few thousand years Huttons ideas were eventually included in a principle called _____________________________________.
- 2. Chapter 16 Lesson 1: Fossils p564-572 page 2 o The principle of uniformitarianism states that geological processes that occur ____________are similar to those that have occurred in the past o According to this view, Earths surface is constantly being reshaped in a steady, uniform manner Today, uniformitarianism is the basis for understanding Earths past But scientists also know that catastrophic event do ___________________________ occur o Huge volcanic eruptions and giant meteorite impacts can change Earths surface quickly and can be explained by natural processes Fossil Formation Not all dead organisms become_____________________. More than likely, you will not become a fossil. Fossils form only under _______________________ conditions. Conditions for Fossil Formation Most plants and animals are eaten or ____________when they die, leaving no trace that they ever lived o Consider an apple. More than likely an apple will decay into a _____________lump and be decomposed by bacteria and insects. Some conditions increase the chances that a fossil will form. 1. If the organism has __________parts, such as shells, teeth, or bones 2. If the organism is _______________quickly after it dies. o This way the layers of sand and mud slow or stop decay Fossils Come in All Sizes Many of the fossils we think of are large dinosaur fossils. However, not all fossils are large. Microfossils are tiny fossils each about the size of a speck of ____________. o Details of microfossils can be seen only under a microscope Types of Preservation
- 3. Chapter 16 Lesson 1: Fossils p564-572 page 3 Fossil are preserved in many different ways: o Preserved Remains o ___________________________________________ o Mineral Replacement o ______________________ o Casts o Trace Fossils Preserved Remains Sometimes the _________________________ remains of organisms are preserved as fossils For this to happen, an organism must be completely _________________________ in some material over a long period of time. o This would prevent it from being exposed to _________________ or bacteria o Generally these fossils are less than 10,000 years old. However insects preserved in ____________________ can be millions of years old. Carbon Films Sometimes when an organism is buried, exposure to heat and pressure forces gases and _________________ out of the organisms tissues. This leaves only the ________________________ behind A carbon film is the fossilized carbon outline of an organism or part of an organism Mineral Replacement Replicas, or copies, of organisms can form from _____________________________ in groundwater. They fill in the pore spaces or ______________________________ the tissues of dead organisms Petrified wood is an example
- 4. Chapter 16 Lesson 1: Fossils p564-572 page 4 Molds Sometimes all that remains of an organism is its fossilized ________________ or impression. A mold is the _________________________ in a rock left by an ancient organism o First, sediment must harden around a buried organism o As the organism ______________________ over time an impression of its shape remains in the sediment o Eventually the sediment turns into ___________________________. Casts Sometimes, after a mold forms, it is filled with more __________________________________ A cast is a fossil copy of an organism made when a mold of the organism is filled with sediment or mineral deposits. Trace Fossils Some animals leaves fossilized traces of their _______________________ or activity A trace fossil is the preserved evidence of the activity of an organism These include: o ___________________________ o Footprints o Nest o Droppings These fossils help scientists learn about characteristics and _____________________ of animals They can reveal clues about an organisms _____________, speed, and whether they traveled ______________________ or in groups.
- 5. Chapter 16 Lesson 1: Fossils p564-572 page 5 Ancient Environments Scientists who study _________________________ are called paleontologists Paleontologists use the principle of uniformitarianism to learn about ancient organisms and their _______________________________. They often compare fossils of ancient organisms to organisms living ___________________________ o For example, trilobite fossil and ______________________________ crabs look alike o Horseshoe crabs today live in shallow water on the ocean floor o Partly because trilobite fossils look so much like horseshoe crabs, paleontologists __________________ that trilobites also lived in shallow ocean waters Shallow Seas Today, Earths continents are mostly above ______________________________________. But, sea level has ________________________ , flooding Earths continents, many times in the past For example, a shallow ocean covered much of North America ___________________ million years ago. Fossils of organisms that lived in that shallow ocean help scientists reconstruct what the _________________________ looked like at that time. Past Climates Evidence indicates that Earth's present-day climate is ____________________________. Fossils show that Earth's climate has warmed and ___________________________ many times in the past ______________________ fossils are especially good indicators of climate change For example, fossils of ferns and other tropical plants dating to the time of the dinosaurs reveal that Earth
- 6. Chapter 16 Lesson 1: Fossils p564-572 page 6 was very warm 100 million years ago o Tropical forests and _____________________________ covered much of the land o Millions of year later, the swamps and forests were gone, but coarse _______________________ grew in their place o Huge sheets of ice called __________________________spread over parts of N. America, Europe, and Asia. o Fossils suggest that some species that lived during this time, such as the woolly mammoth were able to survive in the colder climate