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Biology Labs Page 6 smiley


   A narrative on how to process collected invertebrates goes here.

     The combined efforts of the lab sections should yield data
about the number of taxonomic groups (richness), Simpson's index
(heterogeneity), and taxonomic composition of invertebrate
communities in turbulent and calm-water areas.  At this point, you
should work on rephrasing the objectives of your experiment in the
form of a null hypothesis and a number of alternative hypotheses
for each of these parameters.

     Use the data in Table 2 to calculate richness and Simpson's
index for each turbulent- and calm-water site, and also for all of
the turbulent-water sites combined and for all of the calm-water
sites combined.  Enter the results of your calculations in the
spaces provided at the bottom of Table 2.


     To determine whether taxonomic composition is different in the
two locations, you will perform a chi-square test of independence
and record your calculations one form shown on  page 3-6.  What
will this statistical test tell you?

                      Chi-Square Test of Independence
A narrative on how to make the calculations and an example go here.

  Add narrative on how to write a report here.

      Questions to ponder - Do these three communities have the same P/R
            ratio and what does that tell you about them?  How might your
            results differ if the bottom muds were included in calculating
            total metabolism per unit area of pond?  Ideally the bottles
            should have been suspended during incubation in the water column
            from which the samples were taken.  Explain how this might yield
            a better estimate of metabolism considering such factors as
            temperature and transparency of water to light. 

3.3.  Benthic Sampling (need: screen, bucket, Ponar dredge, shovel, sample

      Collect bottom sediments using dip nets and the Ponar dredge.  Examine
            these samples and characterize the substrate (sandy, muddy,
            organic, etc.).  What are the processes that control the grain
            size of the substrate?  Carefully examine benthic samples for
            organisms.  Collect all that you find.  Upon return to the lab,
            examine these under the dissection microscopes and try to
            classify these organisms as completely as possible (use the
            available references).

3.4.  Wetland Aquatic and Semi-aquatic Vegetation (need: sample bags, marking
      pen for labels).

      Collect small representative samples of emergent aquatic vegetation
            from the water's edge and on either side.  Devise a standardized
            sampling scheme of your own design to quantify the relative
            abundance and biodiversity of plants in the water and associated
            with the wetland margin.  Place samples in labelled bags and upon
            your return to the lab identify as many as you can (either to
            species or at least assigning a number such as #1, #2, etc, for
            those you cannot identify). 

3.5.  Wetland Aquatic and Semi-Aquatic Animals (need: sweep nets, sample
      bottles and bags, and marking pens).

      Examine leaves, twigs, and other debris from the habitat and carefully
            look for animals.  Collect all that you find.  Use the sweep nets
            to catch flying animals.  Standardize a sampling scheme for sweep
            nets and for litter/submerged substrate sampling (e.g. 50 sweeps
            of the net, or 5 mins spent crawling around looking for insects).

            Upon return to the lab, examine these under the dissection
            microscopes and try to classify these as completely as possible
            using the available references, (identify all that you can and
            assign a number such as #1, #2, etc, for those you cannot

      What vertebrates are present in these ecosystems?  Look for reptiles,
            amphibians, and birds.  Stop and listen for mating calls (frogs
            and birds).  What species do you see and/or hear?  Given that
            many birds are only seasonal residents, what role do they play in
            these ecosystems?

      Based upon your identification of the animal forms present in your
            samples, and basic aspects of their feeding ecology according to
            the field guides and other materials available in lab, construct
            a simple diagram illustrating who eats whom in each ecosystem. 
            Such a diagram is called an ecological food web, and shows the
            pattern of energy and material flow through an ecosystem.

Results Symposium During the Third Week.

      During the third lab period, your group will present your research
results in an in-class symposium.

Some Hints on Your Results Presentation During Week Three.

 - Clearly present the research question motivating your study.

 - Clearly present the basic sampling methods you used to collect data.

 - Using one or two tables and graphs, and the appropriate statistical
      techniques, present your results in as brief and concise a manner as

 - Briefly describe how these ecosystems differ according to the data you

 - What factors, if any, seem to be positively or negatively correlated? 
What might the causes of these correlations be?

 - Address how these differences might affect the animals and plants that
live there.  What adaptations would you expect for vertebrates, such as
amphibians or fish, living in each of the habitats?

Here are some additional questions that you might consider:

 - Predation by fish often has a profound effect on the abundance of aquatic
      organisms.  What type of effects would you predict?  Is it possible
      that fish had an effect in each of the aquatic environments?

 - In deep lakes, both phytoplankton and zooplankton are the principal biotic
      components of the ecosystem.  How do the habitats that you are sampling
      differ from this pattern?

 - To what extent do you think your measurements were affected by the
      techniques used to collect them?

 - What are the extreme conditions of water level, temperature, flow
      velocity, and dissolved oxygen that you would expect in each ecosystem?

      Which of the three ecosystems is the most extreme and to which taxa?