ESCI 102 Homework 3
Handed out Monday March 28, 2005
Due Monday April 4, 2005
This assignment must be typed and is worth 15 points.

  1. This portion of the assignment is about the evolution of the 'genetic toolkit' for the Cambrian animal life explosion. It uses two web resources:
    a short movie from the PBS evolution web site:
    http://www.pbs.org/wgbh/evolution/library/03/4/l_034_04.html

    and some text from the UC Berkeley Museum of Paleontology at:
    http://evolution.berkeley.edu/evosite/evo101/IIIC6cComplexity2.shtml

    Watch the PBS video, read the Berkeley text, and then answer the following questions.

    1. The PBS video describes a surprising experiment that Gehring at U Chicago did in 1994. What gene did he switch between a mouse and an eyeless fruit fly? (1 point)

    2. Why did the eyeless fruit fly make a compound insect eye and not a mouse eye? (2 points)

    3. When does the narrator in the video estimate that the last common ancestor to mice and fruitflies lived (you may have to go back and watch the movie twice to catch this.) (1 point)

    4. In geologic time, when did this common ancestor live? (1 point)

  2. This portion of the assignment is about the evolution of limbs and fingers in tetrapods. Watch this video: http://www.pbs.org/wgbh/evolution/library/03/4/l_034_03.html and read the text associated with it on the web. Then read http://www.devoniantimes.org/Order/re-acanthostega.html, and answer the following questions.

    1. Did fish leave the water first, or did they develop limbs and fingers first? (1 point)

    2. What is a tetrapod? (1 point)

    3. Where were the critical tetrapod fossils found? (1 point)

    4. How did Clack know that Acanthostega was an aquatic organism? (2 points)

      This portion of the assignment focuses on plant evolution and uses the 'Devonian Times' web site.

  3. Plant evolution in the Devonian has had profound effects on our fossil fuel resources today. Read the "Devonian Times" article titled 'Opportunity Knocked' at http://www.devoniantimes.org/opportunity/opportunity.html. Why are there no coal deposits before the Devonian? (1 point)

  4. Soil is the foundation of terrestrial life on the Earth right now, but we didn’Äôt really get soils as we know them until the Devonian. Read the "Devonian Times" article on soil development (pedogenesis) at http://www.devoniantimes.org/opportunity/soils.html.

    1. How do plants speed up the process of pedogenesis (soil formation)? (2 points

    2. How did the development of soils change Devonian streams and lakes? (1 points)

  5. Read the "Devonian Times" article on the Devonian mass extinction event at http://www.devoniantimes.org/opportunity/massExtinction.html. What is the 'Plant Hypothesis?' (1 point)