FACULTY NOTES

      The timing of both the individual (read alone) and paired work (discuss together) depends on the sophistication of your students. Tell them how long they have for each and signal the times with a bell, switching off and on the lights, etc. if you have a large class. Make sure the students understand what ballast water is and how fresh water from Russia could have ended up in the Great Lakes.

      Important characteristics include: a relatively long lifespan for an invertebrate, fairly early sexual maturity, huge release of eggs, spawning events several times a year, eggs and sperm viable for several or more hours, tremendous dispersal by free swimming veliger, firm attachment onto surfaces with byssal threads, dispersal of all life stages, tolerance of some salinity, ability to filter plankton from large volumes of water. You may need to make the point that these characteristics are not inherently "bad" (e.g. many aquatic organisms colonize submerged hard surfaces).

      Write the qualities listed by your students on an overhead or the board and ask them to explain how each one contributes to the success of this invader. Help them imagine some of the fascinating traits of this mussel - what nearly a million mussels/m² looks like or a million eggs, veligers carried long distances by currents, adults moving around via the hulls of ships and small boats, the volume of a lake moving through the mussels as they filter feed. You can use photos from books and the web to illustrate some of these points.



Discussion questions:

• Introduced species in general are successful at invading some habitats more than others. What types of habitats would you predict these to be?
  
  
• After zebra mussels were introduced to the Hudson River in the early 1990's the water became much clearer and phytoplankton concentrations decreased about fivefold. Why did this happen and what might the consequences be?
  
  
• Marine organisms are transported all over the world via ballast water in ships, and this is an important dispersal mechanism for species introductions to estuaries. Imagine that you were going to study this phenomenon. How might you go about collecting samples and what factors in particular would you look at that determine success of potential invaders (e.g. length of a voyage)?
  
  
• Zebra mussels are not pest species in their native waters in Russia. Why are they such a nuisance elsewhere but not in Russia?
  
  
• Do scientists "know" that these sets of life history characteristics are what lead to the success of zebra mussels as an invasive species? What information would help you feel more confident about that assertion (comparison with non-invasive species)?
  
  

Student Assessment: Essay Quiz

      Select 3 life history traits of the zebra mussel and explain why these characteristics contribute to its success as an introduced species. Write paragraphs (can be more than one per trait) of 100-200 words for each characteristic.



EVALUATING AN ISSUE: How do you know whether it is working?

      On-going (also called formative) evaluation of the approaches your are using is critical to the success of student-active teaching. Why try out new ideas if you don't know whether or not they are working? This is a brief overview of formative evaluation. For more information, go to the Formative Evaluation essay in the Teaching Section.

Course Goals:

      Formative evaluation only works if you have clearly described your course goals - because the purpose of the evaluation is to assess whether a particular technique is helping students reach these goals. For instance, most of us have "learn important ecological concepts and information" as a course goal. If I reviewed the nitrogen cycle in a class, for evaluation I might ask students to sketch out a nitrogen cycle for a particular habitat or system. Each student could work alone in class. Alternatively, I might ask students to work in groups of 3 and give each group a different situation (e.g. a pond receiving nitrate from septic systems, an organic agricultural field, an agricultural field receiving synthetic fertilizer). The students could draw their flows on a large sheet of paper (or an overhead transparency) and present this to the rest of the class.

The Minute Paper:

      Minute papers are very useful evaluative tools. If done well they give you good feedback quickly. Minute papers are done at the end of a class. The students are asked to respond anonymously to a short question that you ask. They take a minute or so to write their response in a 3x5 card or a piece of paper. You collect these and learn from common themes. In the next class it is important that you refer to one or two of these points so that students recognize that their input matters to you. The UW - FLAG site (www.wcer.wisc.edu/nise/cl1/flag/) gives a good deal of information about using minute papers including their limitations, how to phrase your question, step-by-step instructions, modifications, and the theory and research behind their use.