Typical Slime Mold The Germinated Spores example essay topic

slime mold slime mold or slime fungus, a heterotrophic organism once regarded as a fungus but later classified with the Protist a. In a recent system of classification based on analysis of nucleic acid (genetic material) sequences, slime molds have been classified in a major group called the (or eukaryotes), which includes plants and animals. There are two groups of slime molds, the slime molds of the phylum (division) Myxomycota and the cellular slime molds of Acrasiomycota. Slime molds have complex life cycles that may be divided into an animal like motile phase, in which growth and feeding occur, and a plantlike, immotile, reproductive phase. The motile phase is commonly found under rotting logs and damp leaves, where cellulose is abundant.

It consists in the cellular slime molds of solitary, ameba like cells, and in the Myxomycota of a (multi nucleate) mass of protoplasm called a plasmodium, which creeps about by ameboid movement. Plasmodia often grow to a diameter of several inches and are frequently brightly colored. Both types ingest solid food particles using a process called phagocytosis (see). They feed on living microorganisms, such as bacteria and yeasts, as well as decaying vegetation.

Before entering the reproductive stage, a plasmodium moves to a drier, better-lit place, such as the top of a log. In the ameba like, or cellular, slime molds, up to 125,000 individual cells aggregate and flow together, forming a multicellular mass called a pseudo plasmodium that resembles a slug and crawls about before settling in a location with acceptable warmth and brightness. In the reproductive stage the plasmodium or pseudo plasmodium is transformed into one or more reproductive structures called fruiting bodies, each consisting of a stalk topped by a spore-producing capsule that resembles the reproductive structures of many fungi. Eventually the cellulose-walled spores are released and dispersed; they germinate in wet places, releasing naked cells. In a typical slime mold the germinated spores go through an ameboid or flagellated swimming stage, followed by sexual fusions and cell divisions. The diploid ameboid cell (i. e., the zygote) grows and its nucleus divides repeatedly, resulting in the formation of a new plasmodium.

Under adverse conditions a plasmodium may be transformed into a hard, dry, inactive mass called a. Resistant to desiccation, it becomes a plasmodium again when favorable conditions return. In the case of the cellular slime molds, each spore released becomes a single ameba, which feeds individually until starving cells release a chemical signal that causes them to aggregate into a new pseudo plasmodium, and the process is repeated. In sexual reproduction two haploid amebas fuse, then engulf surrounding amebas, forming a single organism called a macro cyst. The macro cyst then undergoes meiosis and mitosis and releases haploid individuals. There are about 65 cellular and 500 known slime mold species, found in forests and sometimes lawns throughout the world.

In a few species the plasmodium, under favorable conditions, may cover an area of several square feet. A slime mold is the cause of club root, a disease of cabbage and related plants.