PROTOZOAThis group consists of unicellular, eukaryotic organisms belonging to the kingdom Protista. They live in water and soil, and all are chemoheterotrophs. The vegetative stage is known as a trophozoite. Only a few of the 20,000 species cause disease, and some are considered part of the normal inhabitants of other animals. CHARACTERISTICS1. Life cycle—protozoa reproduce asexually by fission, budding, or schizogony (multiple fission). In this process the nucleus undergoes multiple divisions before the cell divides into numerous daughter cells, including a little of the cytoplasm in each. Some protozoa also reproduce sexually. The ciliates such as Paramecium undergo a process called conjugation. Two cells fuse, and a haploid nucleus from each cell migrates to the other cell, thus exchanging genetic material. Some protozoa produce gametes (haploid sex cells) which
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