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BIO: Chpt 15 Sec 15-1 “The Fossil Record”. WARM-UP : Describe the significance of fossils with the study of evolution. Section 15-1 Objectives. (1) The student will be able to define fossil, and tell how the examination of fossils led to the development of evolutionary theories.
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BIO: Chpt 15 Sec 15-1 “The Fossil Record” WARM-UP: Describe the significance of fossils with the study of evolution.
Section 15-1 Objectives • (1) The student will be able to define fossil, and tell how the examination of fossils led to the development of evolutionary theories. • (2) The student will be able to explain the law of superposition and its significance to evolutionary theory. • (3) The student will be able to describe how early scientists inferred a succession of life-forms from the fossil record. • (4) The student will be able to tell how biogeographic observations suggest descent with modification.
The Fossil Record • Nature of Fossils • Fossil- the remains or imprint of a once living organism. • Usually found in sedimentary rock layers. • Formed when sediment, dust, sand, or mud were deposited by wind or water. • Over time hard minerals replace the organism’s tissue, leaving behind rock-like structures. • Mold- type of fossil where the shape of an organism is imprinted in a rock
The Fossil Record • Nature of Fossils (cont’d) • Robert Hooke, an Englishmen, in 1668 published his conclusion that fossils are the remains of plants and animals. • He was once of the 1st scientists to study fossils- petrified wood with the aid of a microscope. • He hypothesized that living organisms somehow turned into rock.
The Fossil Record • Distribution of Fossils • Nicolaus Steno, a Danish scientists, in 1669 proposed the law of superposition which states that successive layers of rock or soil were deposited on top of one another by wind or water. • The lowest layer, called stratum, is the oldest and the top layer is the youngest. • Using Steno’s law allowed the relative age of a fossil to be determined (age compared to another fossil). • The fossil’s absolute age (in years) could be identified from radiological evidence.
The Fossil Record • Distribution of Fossils (cont’d) • Succession of Forms (Table 15-1, pg 280) • The 1st organisms were thought to be prokaryotes during the Precambrian era 540 million years ago. • The fossil record indicated that there were several mass extinctions (brief periods where large numbers of species disappeared). • Figure 15-1, pg 279- fossil of a trilobite (an arthropod; 2nd famous fossil after the dinosaurs) that lived during the Paleozoic era. Trilobites disappeared during the Permian extinction, 245 million years ago. • Kingdom: AnimaliaPhylum: ArthropodaClass: Trilobita
The Fossil Record • Distribution of Fossils (cont’d) • Biogeography • The study of the geographical distribution of fossils and living organisms. • (Figure 15-2, pg 281) Armadillos appeared in North & South America, where glyptodonts (type of herbivore mammal) lived in the past Pleistocene epoch.