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The book includes the three major domains which are in turn subdivided into numerous branches (clades). The smallest microscopic organisms are termed protists, consequently some biologists prefer to call this kingdom the Protoctista rather than Protista. Members of the kingdom Protoctista are not animals, which develop from an embryo called a blastula; they are not plants, which develop from an embryo that is not a blastula but is retained in the mother's tissue; they are not fungi which develop from spores and lack cilia and flagella (called undulipodia) at all stages of development; they are not monerans, which have prokaryotic cells. In California, many species of rare and endangered plants are endemic to serpentine outcrops.
An oversimplified 3-domain system of classification is shown in the following table. All members of this vast phylum have nucleated cells and live in aquatic habitats (freshwater and marine). Fossil protoctists, with thick-walled resting stages or cysts, can be extracted from shale treated with hydroflouric acid. Genetic drift has undoubtedly occured in isolated cypress groves such as this one, which are often referred to as "arboreal islands." Podocarpus gracilior, a member of the Podocarpaceae native to eastern Africa.
The basic characteristics of each kingdom and approximate number of species are summarized in the following table:1.
The five-kingdom system of classification for living organisms, including the prokaryotic Monera and the eukaryotic Protista, Fungi, Plantae and Animalia is complicated by the discovery of archaebacteria.
They also place the macroscopic, multicellular brown algae (Division Phaeophyta) and red algae (Division Rhodophyta) in the Kingdom Plantae. In the latter species, the naked seed sits partially exposed in a red, cup-shaped aril.
In fact, some authors place all of the algae divisions in the Kingdom Plantae. Podocarpus seeds are often referred to as fleshy fruits called drupes, but this is incorrect because drupes develop from the ovaries of flowering plants.
Each kingdom is further subdivided into separate phyla or divisions.Systematists have devised a classification level higher than a kingdom, called a domain or "superkingdom," to accomodate the archaebacteria. The scalelike leaves of Tecate cypress are green and without dorsal resin glands.