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Introduction to Protists: Diversity, Classification, and Ecological Importance

This chapter delves into the fascinating world of protists, the first eukaryotes on Earth. Exploring their origins through the endosymbiosis theory, it explains how protists evolved complex organelles like mitochondria and chloroplasts. The chapter classifies protists into three main groups: animal-like (heterotrophs), plant-like (autotrophs), and fungus-like (saprotrophs), detailing their nutritional methods, reproduction, and examples. It also highlights the ecological roles of protists and their impact on human health, illustrating their significance with diseases such as malaria and amoebic dysentery.

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Introduction to Protists: Diversity, Classification, and Ecological Importance

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  1. Kingdom Protista

  2. Protists Chapter 19 19.1 Introduction to Protists Endosymbiosis • Theory believed to explain origin of eukaryotes and complex organelles like mitochondria & chloroplast • Large prokaryotes engulfed a smaller prokaryote and lived symbiotically • Eventually evolved into a single organism

  3. Protists Chapter 19 19.1 Introduction to Protists Protists • All protists are eukaryotes. • Some reproduce asexually by mitosis while others exchange genetic material. • Most are single celled • First Eukaryotes on Earth • Must have moisture

  4. Protists Chapter 19 19.1 Introduction to Protists Classifying Protists • Some scientists classify protists by their methods of obtaining nutrition. • Animal-like protists- Heterotroph • Plantlike protists- Autotroph • Funguslikeprotists-Saprotroph

  5. Animal-like protists • Heterotrophs • Single-celled • Eat algea, bacteria or other protists • “protozoans” = “pre” animals • 4 phyla (groups) based on mode of movement

  6. Phylum Zoomastigina - flagellates Trypanasoma: Giardia: Causes African sleeping sickness Causes intestinal infections

  7. More Zoomastigina – Trichonympha – digests cellulose in termites

  8. Phylum Sarcodina • Move and feed through use of pseudopods • Pseudopod – temporary projection of the cytoplasm • i.e. Amoebas • When feeding, they surround food and bring into cell in the form of a food vacuole by endocytosis

  9. Phylum Ciliophora • Use cilia for feeding and movement • Cilia: hair-like projections that flow back and forth like ores • Example: Paramecium • Contain macro (working copy) and micronucleus (reserve copy of genetic info) • Contactile vacuole removes excess water • Reproduce by conjugation or binary fission

  10. Ciliophora • Stentor • Largest known protozoan

  11. Phylum Apicomplexa • Parasites • Move through blood of host organisms • Reproduce through spores • Ex: Plasmodium causes malaria. Malaria sporozoite

  12. Protozoa Structures • Pellicle – A rigid, but flexible structure of microtubules that underlies the plasma membrane of many protozoans.

  13. Trichocysts – Some pellicular structures are used for protection. These “threads” cover the body of the protozoan.

  14. Protists and Disease • Malaria – effects 300-500 million people • Caused by the sporozoan Plasmodium carried by mosquitoe • African sleeping sickness • Caused by zooflagellateTrypanosoma • Spread by the bite of the Tsetse fly • Amoebic dysentery • Caused by amoeba in contaminated water • Giardia • Intestinal infection; ingested from infected waters

  15. Plant-like ProtistsAKA: Algae • Autotrophs • phytoplankton • Contain chlorophyll and other pigments • Produce 70% of earth’s oxygen • 6 phyla • Classified by pigment and structure

  16. Algae • Green • Brown • Red • Dinoflagellates • Diatom • Euglenoid

  17. Phylum Chlorophyta – Green Algae • Contain chlorophyll as main pigment

  18. Phylum Phaeophyta – Brown algae • Contain brown photosynthetic pigment • Include Kelp

  19. Phylum Rodophyta – red algae • Contain red photosynthetic pigments • Carrageenan used in ice cream and other yummy foods

  20. Phylum Pyrrophyta - Dinoflagellates • Two flagella around “equator” to spin • One flagellum on end to propel forward

  21. dinoflagellate Cause red tides

  22. Phylum Bacillariophyta - Diatoms • Pill-box shape • Hard outer sheel • You brush your teeth with these

  23. Diatoms • You brush your teeth with these

  24. Phylum Euglenozoa (Euglenoids) • Swim with flagella • Live in lakes and streams • Can also be heterotrophs! • Use eye-spot to detect light • Can reproduce asexually through binary fission • Example: euglena

  25. Fungus-like Protists • Feed on decaying matter and absorb nutrients- saprophyte • Cell wall with cellulose • Slime molds and Water molds

  26. Phylum Acrasiomycota – cellular slime molds

  27. Water Molds - causes “ich”

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