ANCIENT LIFE AND GEOLOGIC HISTORY

I. California K-6 Standards for Ancient Life and Geologic History

II. Goals of This Module

III. Major Fossil Groups

IV. Geologic Time Scale

V. Mass Extinctions

VI. Cryptozoic Eon

VII. Phanerozoic Eon

VIII. The Magnitude of Geologic Time

IX. Laboratory Exercise

X. Possible Essay Questions

XI. Practice Questions

I. California K-6 standards for ancient life and geologic history -

1. Grade 2
   1. Earth Sciences Topics
      1. Earth is made of materials that have distinct properties and provide resources for human activities. As the basis for understanding this concept, students know:
         1. fossils provide evidence about the plants and animals that lived long ago, and scientists learn about the past history of Earth by studying fossils.

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• To learn how to identify the major fossil groups.

• To learn the major events in the geologic history of the Earth.

• To learn the definitions of and proper spelling for scientific terms that are used commonly in newspapers, magazines, and books, and on television and radio programs in discussions about fossils and geologic history.

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III. Major fossil groups, both extinct and living -

• Microfossils -
  • Forams (Foraminifera) - Sand-grain size one-celled animals with calcite skeletons of many different shapes.

    

    Source for Diagram: http://www.ucmp.berkeley.edu/foram/types/39131.htm

    

    

    Source for Diagrams: http://www.kgs.ukans.edu/Publications/ancient/f06_fusulin.html

  • Diatoms - Sand-grain size one-celled plants with disk-shaped opal (quartz) skeletons.

  

  

  Source for Diagrams: http://www.calacademy.org/research/diatoms/

• Plants -
  • Calcareous algae - Irregular, thinly layered mounds of calcite.

    

    Source for Diagrams: http://rikanoheya.katsurao-jhs.katsurao.fukushima.jp/WISDOM96/hamelin/hamelin.html

  • Other plants - Leaves, seeds, cones, and petrified wood. Coal beds are thick masses of carbonized plant fragments that were preserved in a swamp environment.

  

  Source for Diagram: http://www.peabody.yale.edu/collections/pb/

  

  Source for Diagram: http://is2.dal.ca/~dommelen/gifs/tree1.jpg

• Sponges - Irregular masses of porous material.

  

  Source for Diagram: http://www.kgs.ukans.edu/Publications/ancient/f07_sponges.html

• Corals - Irregular colonial masses of calcite that contain abundant, radially symmetrical, cup-shaped, living platforms that are larger than 1 mm in diameter.

  

  

  Source for Diagrams: http://www.netsync.net/users/hirsch/corals.htm

• Bryozoans - Irregular colonial masses of calcite that contain abundant, tiny holes less than 1 mm in diameter where the colonial animals live.

  

  Source for Diagram: http://www.uky.edu/KGS/coal/webfossl/pages/bryos.htm

• Mollusks -
  • Clams - Paired shells that are mirror images of each other.

    

    Source for Diagram: http://www.netsync.net/users/hirsch/clams.htm

  • Snails - Cone-shaped, spirally coiled shells.

    

    Source for Diagram: http://www.gwsford.com/~witano/fossils/sandiego/epitonium01.htm

  • Cephalopods - All have planispirally coiled shells.
    • Nautiloids - Planispirally coiled shells with plain walls at the back of the living chamber.

      

      Source for Diagram: http://www.gwsford.com/~witano/fossils/pierre/eutre1.htm

      

      Source for Diagram: http://www.dc.peachnet.edu/~janderso/historic/nautil.htm

    • Ammonites - Planispirally coiled shells with convoluted walls at the back of the living chamber.

  

  Source for Diagram: http://www.sierra.cc.ca.us/museum/ammonite.htm

• Brachiopods - Paired shells that are not mirror images of each other.

  

  Source for Diagram: http://www.uky.edu/KGS/coal/webfossl/pages/brachs.htm

  

  Source for Diagram: http://www.uky.edu/KGS/coal/webfossl/pages/brachs.htm

• Arthropods - All have segmented external skeletons made of chiton (calcium phosphate).
  • Insects - A segmented body with six legs.

    

    Source for Diagram: http://www.gplatt.demon.co.uk/fly1.htm

  • Spiders - A segmented body with eight legs.

    

    Source for Diagram: http://www.gplatt.demon.co.uk/spider2l.htm

  • Crabs and Lobsters - A segmented body with ten legs.

  • Barnacles - A segmented body surrounded by a cone-shaped skeletal structure that is attached to rocks or other objects.

  

  Source for Diagram: http://got.net/~dbasye/fossils/barnacle.gif

• Trilobites - A segmented body that is divided into three longitudinal lobes.

  

  Source for Diagram: http://www.ucmp.berkeley.edu/arthropoda/trilobita/trilobitafr.html

• Echinoderms - All have pentagonal symmetry and segmented external skeletons made of calcite.
  • Blastoids - Attached by a stalk to the ground and have no arms.

    

    Source for Diagram: http://www.englib.cornell.edu/pri/collections/echin/blast/pentna.html

    

    Source for Diagram: http://www.cismall.com/fallsoftheohio/brochures/crinoid.html

  • Crinoids - Attached by a stalk to the ground and have arms.

    

    Source for Diagram: http://www.cismall.com/fallsoftheohio/brochures/crinoid.html

    

    Source for Diagram: http://phylogeny.arizona.edu/tree/eukaryotes/animals/echinodermata/crinoidea/crinoidea.html#titlefigcaption

  • Brittle stars - Unattached and have thin arms.

    

    Source for Diagram: http://www.ucmp.berkeley.edu/echinodermata/ophiuroidea.html

  • Starfish - Unattached and have thick arms.

    

    Source for Diagram: http://www.ucmp.berkeley.edu/echinodermata/asteroidea.html

  • Sea urchins - Unattached, no arms, and spherical to ellipsoidal in appearance.

    

    Source for Diagram: http://www.stanford.edu/group/Urchin/nathistory.html

  • Sand dollars - Unattached, no arms, and flat in appearance.

  

  Source for Diagram: http://www.ucmp.berkeley.edu/echinodermata/echinodermata.html

• Graptolites - Thin, carbonized films that look like little saw blades; found in shale deposits.

  

  Source for Diagram: http://iago.stfx.ca/people/mmelchin/

• Vertebrates -
  • Fish - Internal skeletons with fins.

    

    Source for Diagram: http://www.nps.gov/fobu/expanded/fos.htm

  • Sharks - Cartilaginous internal skeletons that are not preserved; only the triangular-shaped teeth occur as fossils.

    

    Source for Diagram: http://www.nps.gov/fobu/expanded/fos.htm

    

    Source for Diagram: http://got.net/~dbasye/fossils/mackerel.gif

  • Amphibians and Reptiles - Internal skeletons, commonly with short legs and abundant, sharp-pointed teeth in the skull.

    

    Source for Diagram: http://www.emporia.edu/earthsci/museum/mos.htm

    

    Source for Diagram: http://www.dallasdino.org/permanent/prehistoric_texas/mososaur.cfm

    • Dinosaurs - A group of reptiles that lived during the Mesozoic Era.

  • Birds - Internal skeletons with wings, beaks, and feathers.

  • Mammals - Internal skeletons, generally with longer legs than the amphibians and reptiles and with different types of teeth in the skull.

Source for Diagram: http://www.dinodiscovery.com/mstadn.html

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IV. Geologic time scale for the Earth -

• By using absolute dates in conjunction with relative dating procedures (superposition, unconformities, igneous intrusive events, other cross-cutting relationships, and fossils) the chronology of the Earth's history has been determined, and from this chronology, geologists and paleontologists have constructed the Geologic Time Scale for the Earth.

Source for Diagrams: http://www.cadvantage.com/~leiszler/timescal.htm

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V. Mass extinctions -

• The worldwide rock record shows geologists and paleontologists that at various times in the geologic past large numbers of families and even orders of animal and plant groups have become extinct almost simultaneously. This phenomenon is known as mass extinction.

• Such an event requires a worldwide cause -
  • Climatic change - Could worldwide changes in atmospheric circulation, continental geography, or volcanic activity occur quickly enough to cause mass extinction?

  • Meteorite impact - Could a large meteorite impact result in sufficient worldwide changes to cause mass extinction?

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VI. Cryptozoic Eon - The time before life with hard skeletal parts.

• Occurred from 4.6 billion to 570 million years ago.

• Earth probably began with only oceanic crustal rocks.

• Subduction of oceanic crust began when the crust became thick and heavy enough to sink into the mantle. Subduction produced granitic magmas, and as time passed, continents formed and grew from the granitic rocks being produced.

• Bacteria and algae appeared in the ocean as early as 3.1 billion years ago.

• More complex soft-bodied animals and plants appeared in the ocean near the end of the Cryptozoic.

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VII. Phanerozoic Eon - The time during life with hard skeletal parts.

• Paleozoic Era - Occurred from 570 to 245 million years ago (Ma).
  • Life developed hard skeletal parts at the beginning of the Paleozoic. The Age of Marine Invertebrates lasted from 570 to 440 Ma.

    

    Source for Diagrams: http://www.cismall.com/fallsoftheohio/photo.html

  • All life on earth lived in the ocean until 400 Ma; the continents were barren and lifeless.

  • Land plants developed about 400 Ma and spread quickly over the continents because there was little competition.

  • The Age of Fishes lasted from 440 to 360 Ma.

  • The first land animals, amphibians, developed about 360 Ma, and the Age of Amphibians lasted from 360 to 245 Ma.

  • Dense forests of ferns and scale trees filled the continents by about 300 Ma.

  • From about 250 to 245 Ma, climatic change brought aridity to the equatorial part of the world and glaciation to the south polar region. The vast forests were greatly reduced and many forms of life became extinct during a major mass extinction event.

• Mesozoic Era - The Age of Dinosaurs lasted from 245 to 65 Ma.
  • Reptiles developed hard-shelled eggs at the beginning of the Mesozoic and became the first truly terrestrial animals.

  • Coniferous trees became the dominant land plants near the beginning of the Mesozoic.

  • Flying and aquatic reptiles, birds, and mammals developed, but birds and mammals were not yet able to flourish because of the dinosaurs and other reptiles.

  • The end of the Mesozoic (65 Ma) brought another period of mass extinction. The reason for this extinction period is not known, but it is known that a large meteorite or asteroid collided with the earth at 65 Ma.

• Cenozoic Era - The Age of Mammals lasted from 65 to 0 Ma.
  • Flowering plants became the dominant land plants and mammals became the dominant land animals soon after the beginning of the Cenozoic.

    

    Source for Diagram: http://www.nps.gov/fobu/expanded/fos.htm

  • Man-like primates appeared only a few million years ago.

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VIII. The magnitude of geologic time -

• The oldest rocks on the earth are 4.2 billion years old. Meteorite ages indicate that the Earth probably is about 4.6 billion years old. It is important to comprehend that, even though geological movements are not fast enough to recognize in a lifetime, there is sufficient geologic time available for seemingly improbable events to become probable.

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IX. Laboratory exercise -

• IDENTIFY FOSSIL SPECIMENS -

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X. Possible essay questions -

• Describe the important events that occurred during the Cryptozoic Eon.

• Describe the important events that occurred during the Paleozoic Era.

• Describe the important events that occurred during the Mesozoic and Cenozoic Eras.

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XI. Practice questions -

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