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52 53 aPPendix ii Protists protists are either unicellular or multicellular organisms and are divided into two morphologically and ecologically distinct groups, protozoa, which include animallike protists, from which derive fungi and protophta, which are plantlike protists, mostly algae. Protists are evolutions first attempts at complex organisms, for they all have cells with nuclei, making them the basic building blocks for all animals, plants and fungi. The kingdom Fungi comprises many species within various subkingdoms. A familiar subkingdom is Dikarya, which is divided into two phyla, Basidiomycota and Ascomycota. The former phylum contains all toadstools, mushrooms, brackets, puffballs and stinkhorns. The latter contains morels, truffles, baking and brewing yeast, and many lichens. The parts of fungi most evident are actually the fruiting bodies, while the living and growing parts of fungi are networks of threading hyphae called mycelia, which can be vast and ancient organisms hidden from view. Many are symbiotic with other organisms. Sexual reproduction occurs in many fungi, which means that meiosis and fertilization provide the genetic variety for natural selection to evolve them more effectively in changing conditions. Simpler organisms generally dont require this genetic variety to survive because their chosen living environments have remained relatively more constant over the history of life. Mutations and prolific rates of nonsexual reproduction have been sufficient for them to cope with subtle changes that do occur.
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