Chapter #21 : Protists I. The Kingdom Protista A. What is a Protist? Protist – any eukaryote that is not a plant, animal, or fungus. -Protists are very diverse – may be more than 200,000 species.

B. Evolution of Protists *The name Protista comes from Greek words for “the very first”. -Protists are believed to be the first eukaryotic organisms on Earth (1.5 billion years ago). -Biologist Lynn Margulis hypothesized that the first eukaryotes evolved from a symbiosis of several cells, ex : mitochondria & chloroplasts living in eukaryotic cells. Symbiosis – relationship in which two species live closely together.

C. Classification of Protists Protists are classified by : 1. The way that they obtain nutrition. Animal-like protists – heterotrophic protists that can’t make own food. Plant-like protists – autotrophic protists that make their food through photosynthesis. Fungus-like protists – protists that obtain their food by external digestion as decomposers or parasites.

D. Characteristics of Protists 1. Live everywhere in water : oceans, ponds, puddles, surface of snow, inside other organisms. 2. Size range is large : from microscopic algae to giant seaweeds. 3. May be shaped like : bells, stars, snowflakes, or pincushions (round). 4. All are Eukaryotic. 5. Can be unicellular or multicellular.