Protists = All Single-celled Eukaryotes Help (page 2)

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By — McGraw-Hill Professional
Updated on Aug 30, 2011

Debate About The Kingdom

In recent years, there has been much debate among biologists about just whether the protists make up a particular kingdom, or whether the group should be split up into many separate kingdoms. The reason for this debate is the great differences among the 60,000 or so known species that make up the protist group. But there is one essential fact that all of the unicellular protists have in common. Although each of them contains a nucleus, the single cell of each protist is an entire organism! This makes the protists stand out distinctly from the nucleated cells of multicellular organisms, like humans, most plants, and animals. Human cells, for instance, typically have a nucleus, but they are also highly specialized members of particular body tissues, so they don’t have to “do it all.” Like the bacteria and other prokaryotes, however, the primitive protists were among the “very first” to appear on this planet, so that each cell must “do it all”!

The body structures and functions required for such cells to “do it all” will differ, of course, according to the habitat where they live, their main mode of nutrition, and the specific behaviors needed for their survival. The huge and varied group of protists, therefore, can be basically subdivided into three main subgroups. These are the protozoa ( pro -toe- ZOH -ah), algae, and slime molds.


Practice problems for these concepts can be found at:  The Protists: "First of All" Test

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