BIO: Chpt 15 Sec 15-1

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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.

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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.

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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 organisms
  tissue, leaving behind rock-like structures.
• Mold- type of fossil where the shape of an
  organism is imprinted in a rock

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The Fossil Record

• Nature of Fossils (contd)
• 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.

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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 Stenos law allowed the relative age of a
  fossil to be determined (age compared to another
  fossil).
• The fossils absolute age (in years) could be
  identified from radiological evidence.

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The Fossil Record

• Distribution of Fossils (contd)
• 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

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The Fossil Record

• Distribution of Fossils (contd)
• 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.