Chapter 19, Problem 38A

Summary Introduction

To analyze : 

The similarities and dissimilarities between a water mold and acellular slime mold.

Introduction :

Both a water mold and acellular slime mold belongs to the fungus-like protists as they resemble fungus to some extent. However, acellular slime mold and a water mold are different from each other and are placed in separate phylum myxomycota and oomycote respectively, under the kingdom protists. 

Explanation of Solution

A water mold and a slime mold are fungus-like organisms based on their mode of nutrition. They acquire their food by the saprophytic mode of nutrition. Neither of the two belongs to the kingdom fungi. Both of them are flourish on dead and decaying organic matter. They prefer to grow in damp places rich in decaying organic matter. 

The acellular slime molds are phagocytic saprobes. They do not possess a cell wall. The somatic phase is characterized by a diploid multinucleate unicellular plasmodial stage. The locomotion is through the pseudopodia. The ameboid cells produced after the germination of spores may bear flagella (swarm cells). On the other hand, the water mold is also a saprobe as it does not carry out photosynthesis. They have cell walls made up of cellulose. The plant body is multinucleate, aseptate, and multicellular (coenocytic). They cannot locomote as they attach themselves to the substratum through hyphae. However, the zoospores or reproductive cells are generally biflagellate with two different types of flagella. One of the flagella is smooth and the other one is tinsel type. Some of them are plant pathogens. for example,  Phytophthora infestans  which causes late blight of potato.

Conclusion

Water mold and acellular slime mold are fungus-like organisms as they share some similar characteristics with fungus. However, they are not placed under the kingdom fungi. They are fungus-like protists that are saprobes. They belong to two different phyla because of some contrasting characters such as water molds that are multicellular but acellular slime molds that are unicellular.