Protist Kingdom - Ch. 15 p Droplets of pond water are filled with Protists! Protists are the first eukaryotes to evolve from prokaryote (bacteria) ancestors. They are much more complex than prokaryotes. Protists are the ancestors to all other eukaryotes – plants, fungi, and animals. The fossil record indicates that eukaryotes evolved from prokaryotes (bacteria) more than 1.7 billion years ago. How did eukaryotic cells evolve, and how did their membrane-enclosed organelles evolve? A widely accepted theory is that eukaryotic cells evolved through a combination of two processes: #1: All organelles (except mitochondria and chloroplasts) evolved from inward folds of the plasma membrane of a prokaryotic cell.

# 2: Endosymbiosis The Endosymbiosis Theory was largely developed by Lynn Margulis of the University of Massachusetts: “Chloroplasts and mitochondria evolved from small prokaryotes that established residence within other, larger host prokaryotes.” Ex : mitochondria ancestors may have been aerobic bacteria that were able to use oxygen to release large amounts of energy from organic molecules by cellular respiration. The host cell may have injested these for food; if they remained alive, they continued to perform respiration within the cell. Ex: Similarly, chloroplasts may have come to live inside a larger host cell. Because almost all eukaryotes have mitochondria but only some have chloroplasts, it is likely that mitochondria evolved first. Endosymbiosis eventually became mutually beneficial. How? ____________________

The Diversity of Protists -Vary in structure and function more than any other group or organism. Most are unicellular, but some are colonial or multicellular. Each cell must carry out all the basic functions of an entire organism. Four major categories of protists: (are grouped more by their lifestyle than by their evolutionary relationships) 1. Protozoans 2. Slime molds 3. Unicellular Algae 4. Seaweeds

1. Protozoans Ingest food and thrive in all types of aquatic environments, including wet soil and the watery environment inside animals. Include: 1) Flagellates: move by means of one or more flagella. Most free-living, but some are parasitic: cause diarrhea (infected drinking water) or sleeping sickness from the tsetse fly. 2) Amoebas: move by means of pseudopodia 3) Forams: move with pseudopodia; flexible 4) Apicomplexans: are all parasitic and are named for an apparatus at their apex which is specialized for penetrating host cells. Plasmodium -malaria. 5) Ciliates: use cilia to move and feed. Amoeba Forams Apicomplexan Ciliate: Paramecium Flagellates