Teacher’s Guide by: Jessica DelMonte (Idaho State University)
Lesson Overview: Students are introduced to the Phylum Molluska and explore the effects of an exotic snail on local mollusk populations.
National Science Education Standards Addressed:
1.
2.
652.02. Understand the interdependence of organisms.
656.03. Understand the importance of natural resources and the need to manage and conserve them.
Resources:
1.
Molluska powerpoint presentation
2.
Frest and Johannes, 2000. A comprehensive checklist of Idaho Mollusks,
Journal of the Idaho Academy of Science. (call # in ISU library is Q11.I2)
3.
http://www.manandmollusc.net/
4.
http://www.esg.montana.edu/aim/mollusca/nzms/
Subject area(s): Biology, Zoology,
Ecology
Topic: Phylum Molluska, exotic species
Audience: Grades 7-12
Suggested time: 55 minutes
Materials:
 A variety of mollusk shells
 New Zealand mudsnail samples
 Petri dishes
 Hand lenses
 Dissecting microscopes
 Forceps
Learning Objectives:
Students will:
1.
Describe the features of animals in the Phylum Molluska
2.
Explain how the exotic New Zealand mudsnail threatens local mollusk populations
Background:
1.
The Phylum Molluska contains 100,000 living species, making it the second largest (after the
Phylum Arthropoda) in terms of species richness.
2.
Idaho has over 266 taxa of mollusks, 34% of which are endemic (meaning that they are found nowhere else in the world!).
3.
A growing problem in the western United States is the invasion of an exotic snail, called the
New Zealand mudsnail.
4.
Idaho’s mollusk diversity is threatened by development, pollutants, and exotic species like the
New Zealand mudsnail.
Assessment Strategy:
1.
describe here ways to assess if students are meeting your learning objectives
Teaching Tips:
Obtaining Materials and Experiment prep: The Idaho Museum of Natural History has several different types of shells available for checkout on a weekly basis. Most of these are marine, but there are a few shells of a local terrestrial snail called the mountain snail. Many students have seen these while hiking etc., so I use them as an engagement strategy. These shells can also be collected from the Mink Creek area. New Zealand Mudsnails
Idaho State University’s GK-12 Project http://www.isu.edu/%7Esanghann/Index.html
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can be obtained from at least 4 places along the Portneuf River as well as Mink Creek and Goodenough Creek
(see the maps at http://www.esg.montana.edu/aim/mollusca/nzms/ for exact locations and site descriptions).
Live mudsnails can be used for experiments and preserved specimens can be used to estimate abundances at a particular site. Live snails can be kept in a bucket with stream water and an aerator for several days. Snails can also be preserved in 70% ethanol. If you will have students make density estimates, be sure to sample a known area (e.g. 1 m
2
).
Engage – Put terrestrial snail on each table.
Who has seen this before? Where? What is it? What is it called?
Just an empty shell, the animal that lived inside looked like this (show first slide on powerpoint presentation).
These can be found in most of the Rocky Mountain states on vegetated hillslopes.
Type of mollusk (on board – Phylum Molluska)
What other mollusks do you know / have seen?
Explore – Have students examine other shells while providing more information about mollusks, like the points listed below.
Mollusks live in all types of habitats, land (terrestrial) and water (aquatic) and marine. Some even live on the tops of trees. Some snails are very strong climbers and can lift ten times their own weight up a vertical surface. If you were this strong, you could carry about 700 pounds straight up a wall.
There are 7 classes of mollusks. You will study 4 in this class, but today we’ll just look at 2 classes:
Gastropoda (snails) and Bivalva (clams and mussels).
The majority of molluscs have a shell of some kind. It is secreted by the mantle and protects the body. The shell is made mostly of calcium, which comes from the water. The first shell appears during the larval stages and grows throughout life.
Shells are very important because the shape, size, and color are used to identify mollusks. Shells also decay slowly and fossilize well, and the fossil record of molluscs is excellent and ancient.
Introduce students to the New Zealand mudsnail, and exotic species. Ask if anyone is familiar with other exotic species and discuss why they are a problem in general and why the New Zealand mudsnail has been so successful.
Show slides of mudsnail and give facts about its life cycle, etc.
Give each student some specimens (either live or preserved) from the sample
Have students observe, make sketches, and count the number of snails in their sub-sample
Each student writes the number of snails in their sample on the board
Add the number of snails in each sub-sample and have the students determine the density of snails at your site (# per m 2 )
Explain – Lead a discussion in which students compare the density of New Zealand mudsnails with the density of some native snail species.
Extension(s):
Students can investigate the effects of several other exotic species. A good source for more information on exotics in the United States is www.invasivespecies.gov
This material was developed with support from the National Science Foundation’s Graduate Teaching Fellows in K-12 Education (GK-12) program ( DGE-0338184 ) and Idaho State University. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the NSF.
Idaho State University’s GK-12 Project http://www.isu.edu/%7Esanghann/Index.html
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