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Earth's History
A Trip Through Earth's History
| Question | Answer |
|---|---|
| A fossil is ______________. | the preserved remains or traces of an organism |
| How do most fossils form? | Living things die and their remains are buried by sediment |
| A fossil is formed when minerals replaced all or part of an organism called a ______________. | petrified fossil |
| ______________ can provide clues about the activities of ancient organisms. | trace fossils |
| The process by which all the different kinds of living things have changed over long periods of time is called ______________. | evolution |
| A type of organism that no longer exists on Earth is said to be ______________. | extinct |
| The relative age of a rock is ______________. | its age compared to the age of other rocks |
| The law of superposition states that, in horizontal layers of sedimentary rock, each layer is ______________. | older than the layer above it and younger than the layer below it |
| The fossils of organisms that were widely distributed but only lived during a short period of time are called ______________. | index fossils |
| Radioactive decay occurs when atoms of an unstable element ______________. | break down to form atoms of another element |
| Radioactive dating enables geologists to determine ______________. | the absolute age of rocks |
| The Paleozoic, Mesozoic, and Cenozoic are divisions in the geologic time scale called ______________. | eras |
| The geologic time scale is a record of ______________. | the life forms and geologic events in Earth's history |
| The earliest life forms were ______________. is di | single-celled organisms |
| The evolution of photosynthetic organisms that lived 2.5 billion years ago led to ______________. | an increase in oxygen in the atmosphere |
| The end of the Paleozoic was marked by the ______________. | Permian extinction |
| The first vertebrates were ______________. | jawless fish |
| Many scientists hypothesize that the dinosaurs became extinct because ______________. | an asteroid hit earth, throwing dust into the atmosphere and cooling the climate so that the dinosaurs could not survive |
| Fossils usually occur in ______________ rock. | sedimentary |
| On the geologic time scale, the ______________ Era is divided into the Triassic, Jurassic, and Cretaceous periods. | Mesozoic |
| A(n) ______________ fossil forms when dissolved minerals replace the remains of an organism then then harden to form rock. | petrified |
| Plant leaves may form a fossil called a(n) ______________, a thin layer of carbon on rock. | carbon film |
| ______________ are scientists who study fossils. | |
| A rock layer's ______________ age is its age compared to the age of other rock layers. | relative |
| A(n) ______________ is a gap in the geologic record where some rock layers have been lost because of erosion. | unconformity |
| Certain ammonites are used as ______________ fossils because they lived in many different areas but for only a brief time. | index |
| The time it takes for one half of the atoms in a sample of a radioactive element to decay is called the element's ______________. | half-life |
| Geologic time begins with the long span of time called ______________ Time. | Precambrian |
| The present day is part of the ______________ Era. | Cenozoic |
| The ______________ Era is sometimes referred to as the "Age of Reptiles." | Mesozoic |
| How is a cast fossil formed? | soft part of animal decays and minerals slowly fill in space |
| How is it possible for an organism to have very little change since its death 10,000 years ago? | it was preserved when it was trapped in tar, ice, or amber |
Created by:
Pacelli
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