Chapter 27, Problem 39A

Summary Introduction

To write:

About the animal-like, plantlike, and funguslike protists.

Introduction:

Protists are not animals, plants, or fungi because they do not have all of the characteristics necessary to place them in any of these kingdoms. All protists share one important trait i.e., they are eukaryotes. Like all eukaryotes, the DNA of protists is found within the membrane-bound nucleus. Although protists have a cellular structure similar to other eukaryotes, there are remarkable differences in their reproductive methods. Protists are divided into three groups using their method of obtaining nutrition: animal-like protists, plantlike protists, and funguslike protists.

Explanation of Solution

The amoeba is an example of a unicellular, animal-like protist or protozoan. Protozoans are heterotrophs and usually ingest bacteria algae, or other protozoans. One of the characteristics that biologists use to further classify protozoans into different phyla is their method of movement.

The giant kelp is an example of plantlike protist that makes its own food through photosynthesis. Plantlike protists commonly are referred to as algae. Some algae are microscopic. The unicellular algae Micromonas are about 10-⁶m in diameter. Other forms of algae are multicellular and are quite large. The giant kelp, Macrocystis pyrifera, can grow up to 65 m long.

The water mold is an example of a funguslike protist that is absorbing nutrients from a dead salamander. Funguslike protists are similar to fungi because they absorb their nutrients from other organisms. These organisms are not classified as fungi because funguslike protists contain centrioles which involved in mitosis and usually are not found in the cells of fungi. Fungus and funguslike protists are also differ in the cell walls composition.

Conclusion

Grouping protists by how they obtain nutrition is a convenient method of classifying them. However, this method does not consider an organism’s evolutionary history.