Those Little Critters in the Water

Introduction:

Protists are one-celled eukaryotic organisms that have existed for over 2 billion years.  Protists have a nucleus bound by nuclear membranes and contain more highly differentiated cell organelles than bacteria.  They can be free-living, but many are parasitic and live inside hosts.   Protists show features that parallel processes found in higher organisms.  Some are photosynthetic, ingestive, absorptive, nonmotile, motile, and some have cell walls while others do not.  There are spore producing protists that resemble fungus, photosynthetic protists that led to the evolution of plants, and mobile flagellated protists that preceded animals.  Protists play three different functional roles.  Some are producers while others are consumers or even decomposers.

 

National Standard Addressed:

This lab addresses unifying Concepts and Processes with the subtitle of evolution and equilibrium.  This lesson meets this standard by showing students exactly what features are present that unify the protists as individual organisms.  Using these different feature students can begin to see how the protists have evolved.

The standard of Life Science, Diversity and Adaptations of Organisms is also covered in this lab.  There are many animals that are protists and this helps to show how protists can look different but still be considered protists.  Though they may have many adaptations students will be able to understand that they are all still protists.

 

Objectives and Benchmarks:

This activity allows students to observe the characteristics of various different live Protists.  At the completion of this lab students will be able to accurately use a microscope and be able to identify several protists.

 

Materials:

Compound microscope            Slides               Cover Slips     Pipets  

Identification Guide   Water Samples                       Various Protists

 

Advanced Preparation:

Obtain water samples and identification guide.  The water samples should be collected from the hazy layer of water just above the mud on the bottom.  This is where the most organisms will be found.

Copy student observation sheets from appendix.

 

Procedure:

There will be several containers of water samples that have been collected from various lakes or streams.  Help students make wet mounts of different ones and observe the organisms.  Students can describe how they are different and draw several representations in their lab notes.  Students should be asked to determine how they propel themselves.

Using the lab manual, have students try to identify the organisms that they have found in the water samples.

 

Things to Consider:

Which Protists are most like plants?  Which are more like animals?  Why do you say this?

What structures did the different Protists use for movement?

 

Possible Integration:

Aquaculture can be integrated into this lesson because the students are learning about water environments and what organisms live together.

Art could also be integrated in by having the students draw the organisms that they see under the microscopes.

 

Critical Concepts:

Protist                       Spirogira           Cyanobacteria            Bosmina            Daphnia

Paramecium            Planaria             Diatoms                       Rotifers              Dinoflagellates