AQUATIC ORGANISMS

Mary Kostalos


Aquatic organisms are incredibly diverse. The following information is designed to give you a brief overview of some of the major groups of organis ms that you will find as you study various aquatic systems during this class . It is not inclusive and, for the most part, uses common names for these organi sms.

All living things are divided into large groups called Kingdoms. You are probabl y familiar with the plant kingdom and animal kingdom, for example. Each kingdom is further divided into groups called phyla for animals (phylum is the singular) and divisions for plants. Phylum or division is further divided into class, o rder, family, genus and species.

The major kingdoms in most systems of classification are the following:

A. Monera. These are simple, single-celled or colonial forms that do not have a membrane-bounded nucleus (prokaryotic). Important organisms in this group are the bacteria and the blue green bacteria (formerly known as the blue green algae).

B. Protista. Organisms in this kingdom are also single-celled or colonial but they have a distinct nucleus (Eukaryotic). Some of the organisms in this ki ngdom are plant-like (they carry out photosynthesis). We call these organisms al gae. Diatoms are an example of an alga that is important in aquatic systems. Oth er organisms in this kingdom are more animal-like. We call these organisms proto zoans. Different types of protozoans have different forms of locomotion. Some pr otozoans (ciliates) have cilia (small hair-like structures); others (flagellates ) move by pseudopods -- the whole cell flows in the direction of movement.

C. Fungi. Fungi are unique organisms that are parasites or saprophytes (f eed on dead organic matter). They may be single-celled or colonial, but most are multicellular (composed of many cells which have become specialized to carry out different functions within the organism). Most aquatic fungi are small and loo k like a mass of threads. Mushrooms are a type of fungus with which you are familiar.