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Protists Classification WS Name Protist Classification Worksheet 16-3 Lesson Objectives Explain what a “protist” is. Describe how protists are related to other eukaryotes. Lesson Summary The First Eukaryotes Protists are eukaryotes that are not members of the plant, animal, or fungi kingdoms. The first eukaryotes were protists. Most protists are unicellular. Protists are a very diverse group of species. Many species of protists are more closely related to plants, fungi, or animals than they are to other protists. Because of this, some scientists think the members of the kingdom Protista should be reclassified. Protists—Ancestors and Descendants All eukaryotes are descended from early protists, but modern protists are very different from their ancestors. Like other eukaryotes, they have been evolving over the last 2.5 billion years. The First Eukaryotes 1. What is a protist? 2. Why are brown algae considered protists even though they are multicellular? 3. Why do scientists no longer use the categories of animal-like, plantlike, and fungus like protists to classify protists? For Questions 4–7, complete each statement by writing the correct word or words. 4. Most single-celled eukaryotes are currently classified as . 5. Genetic analyses of protists indicate that they belong in six different . 6. Protists were the first . 7. Unlike most protists, which are unicellular, kelp has tissues. For Questions 8–11, use the diagram and legend below. Six Major Groups Excavates Chromalveol ates Cercozoa, Foraminifera, and Radiolaria Rhodophyta (red algae) Amoebozo Choanozoaa 8. Plants are most closely related to which of the following groups? A. Amoebozoa B. Cercozoa C. Rhodophyta D. Choanozoa 9. Brown algae is a member of the clade Chromalveolates. Which of the following is its closest relative? A. slime mold, an Amoebozoan C. Giardia, an Excavate B. red algae, a Rhodophytan D. Globigerina, a Foraminiferan 10. Which clade is most primitive? A. Excavates B. Choanozoa C. Cercozoa D. Chromalveolates 11. Which statement is true? A. Plants, fungi, and animals all emerged from a common protist ancestor. B. Only fungi and animals emerged from a common protist ancestor. C. Only animals and plants emerged from a common protist ancestor. D. Plants, fungi, and animals all emerged from different protist ancestors. Protists—Ancestors and Descendants For Questions 12–19, write True or False on the line provided. 12. The first eukaryotes were Archaea. 13. It is possible to find the earliest fungi by looking at modern protists. 14. Modern protists have evolved very little from their ancestral forms. 15. Today, there are as many as 300,000 known species of protists. 16. The oldest known eukaryotic fossils are around 1.5 billion years old. 17. The first protists most likely evolved 3.6 billion years ago. 18. Plants, animals, and fungi most likely evolved from multicellular protists. 19. The protists are more diverse than any other eukaryotic kingdom. 20. Complete the concept map below. Certain ancient species of Archaea evolved into which evolved Into Many different modern groups of protists Apply the Big idea 21. Euglena are photosynthetic protists that live in fresh water. How would their photosynthetic properties help stabilize a pond ecosystem? Suppose they and all the other photosynthetic organisms disappeared from the pond. How might their disappearance affect other organisms that lived in the pond? .
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