Phylum Chlorophyta

    Green algae of phylum Chlorophyta have the same photo-synthetic pigments and the same cell wall structure as plants. In fact, they are believed to be the ancestors of modern plants. Some are unicellular, and some are multicellular; however, none have specialized tissues like plants, and therefore they remain classified with the simpler organisms in kingdom Protista.

    The funguslike protists are called slime molds, which belong to the phyla Myxomycota and Acrasiomycota. All slime molds are heterotrophs.

 

    Phylum Myxomycota

    This phylum includes the plasmodial (acellular) slime molds. A plasmodium consists of a single cell with multiple nuclei. Plasmodial slime molds creep slowly along the decaying vegetation they digest; when food or water is scarce, they produce small tough spores that germinate when environmental conditions improve.

 

    Phylum Acrasiomycota

    The cellular slime molds belong to. The mold is really a large collection of individual amoebalike protists which congregate into a “pseudo-plasmodium” or “slug” only when food is scarce. In this cooperative form, they produce a single stalk that releases spores.

 

    Kingdom Fungi

    Fungi are typically nonmotile and, like plants, have cell walls. Unlike plants, fungi are heterotrophic and have cell walls made of chitin rather than cellulose. Fungi secrete enzymes to digest their food externally and then absorb the nutrients. They usually live as decomposers, living off dead and decaying organisms, or as parasites, growing on or in other living organisms. With the exception of yeast, most fungi are multicellular. Structurally, multicellular fungi are composed of filaments called hyphae; some have hyphae that are segmented by divisions called septa, while others have a continuous cytoplasm with many nuclei in each hyphae. Many fungi exist as a tangle of hyphae, called a mycelium. Examples of fungi are yeast and mushrooms.

 

    Most fungi can also exist in the form of a spore, a microscopic reproductive structure that is much more resistant to lack of food or water. Unlike most plants and animals, which exist predominantly in a diploid state, fungi spend most of their time in a haploid state, with only a brief diploid phase during the reproductive cycle.

 

    Some fungi grow in a mutually beneficial relationship with a photosynthetic algae or plant. Lichen is an example of such a partnership between a fungus and an algae. The benefits of the merger are apparent: lichen can grow in a wider range of temperatures than any individual plant or fungus, and lichen can often colonize rocks that will not support any other multicellular life forms.

 

    Kingdom Plantae

    Plants are complex multicellular photosynthetic autotrophs, with cellulose in their cell walls and a waxy cuticle covering their aboveground parts. They are easily distinguishable from members of all other kingdoms, with the possible exception of their simpler ancestors in the Protista kingdom, the green algae. Over evolutionary time, plants improved their ability to live on land by developing a variety of important features. Plants can be divided into four major groups, displaying a progressively greater degree of adaptation to the terrestrial environment.