BIOL 215 Lecture Notes - Lecture 1: Developmental Biology, Polychaete, Cambrian Explosion
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BIOL 215 Assignment #1
Due Friday, Oct. 6, 2017 @ 12 pm
All assignment must be submitted electronically through MyCourses
Based on: “Sperling EA, Frieder CA, Raman AV, Girguis PR, Levin LA, Knoll AH (2013) Oxygen,
ecology, and the Cambrian radiation of animals. PNAS 110: 13446-13451”
Questions (*please keep your answers concise and to the point*):
1. The scientific method (discussed in lecture 1) involves observing some element or
process in the natural world and formulating a question about why it exists. A
researcher can then use this question to generate a testable hypothesis. In the paper by
Sperling at al. 2013, on polychaete worm communities in low oxygen regions of the
a. The observation and subsequent question they are interested in (1 mark).
b. The hypothesis the authors are testing (1 mark).
2. What is the difference between external and internal controls that the authors propose
could account for the Cambrian explosion? (0.5 mark). Give an example of each (0.5
mark). Why is an accounting of internal controls insufficient to address the authors’
question about the Cambrian explosion? (1 mark).
3. Examine Figure 1. What information forms the basis of the authors’ maximum and
minimum estimates for the evolution of carnivory in Nemertea and Priapulida? (1 mark)
Why do the authors think that the last common ancestors of the superclades of
Deuterostomia, Ecdysozoa, and Lophotrochozoa lacked carnivory? (1 mark). Why is the
timing of the evolution of carnivory important? (1 mark).
4. What about polychaete worms makes them ideal study organisms to address the
authors’ hypothesis? (1 mark).
5. Explain how habitats with carnivores differ from habitats without carnivores? (1 mark).
How do the different oxygen regimes differ in terms of the number of carnivores
present (1 mark), and the percentage of the community these carnivores represent? (1
6. What two different explanations do the authors offer for the importance of oxygen in
maintaining a carnivorous lifestyle, and why do they suggest one explanation is more
likely than the other? (1 mark).
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