Copyright Pearson Prentice Hall 20-1 The Kingdom Protista Photo Credit: Andrew Syred/Science Photo Library/Photo Researchers, Inc. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall What Is a Protist? What Is a Protist? Protists are eukaryotes that are not members of the Plant, Animal, or Fungi kingdoms. The kingdom Protista may include more than 200,000 species. Most, but not all, protists are unicellular. Some consist of hundreds or thousands of cells but are still protists. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Evolution of Protists Evolution of Protists The first eukaryotic organisms on Earth were protists, and appeared 1.5 billion years ago. They belong to the kingdom Protista, which come from Greek meaning “the very first.” Mitochondria and chloroplasts in eukaryotic cells may have descended from aerobic and photosynthetic prokaryotes that lived inside larger cells. Copyright Pearson Prentice Hall

Classification of Protists It is suggested that protists be divided into multiple kingdoms because DNA evidence indicates that different groups of protists evolved independently from archaebacteria. Scientists cannot agree on how to divide them currently. Copyright Pearson Prentice Hall

Classification of Protists One way protists can be classified is by how they obtain nutrition: Heterotrophs are called animal-like protists. Photosynthesizers are called plantlike protists. Decomposers and parasites are called funguslike protists. These are an artificial way to organize an extremely diverese group. They do NOT reflect the evolutionary history of the protists in each group. Copyright Pearson Prentice Hall