Protista

1. Protista

2. Brief Introduction • Dutch microscopist Anti van Leewenhoek was the 1st to lay eyes on protists 300 yrs ago • Viewed a droplet of pond water under a light microscope • Van Leewenhoek wrote, “No more pleasant sight has met my eyes than this, of so many thousands of living creatures.” • Some protists propel themselves w/ whipping flagella others creep along by means of blob-like appendages

3. Cont. • All protists were once classified as 1 kingdom, Protista, but recently advances have brought the kingdom down • Some are more closely related to plants, fungi, or animals than other plants • Various protists are now recognizied as kingdomsin their own right Biologists still use the term protist today

5. Structural & Functional Diversity • Unicelluar or can be multicelluar • Unicelluarprotists use organelles such as nucleus, endoplasmic reticulium, golgi apparatus, and lysosomes, and some rely on organelles not found in eukaryotes such as a vacuole • Some are photoautotrophs and contain chlorplasts, others can be heterotrophs (absorbing organic molecules or ingesting larger food prticles)

6. Endosymbiosis in Eukaryotic Evolution • What makes protists so diverse? • Endosymbiosis, the process in which certain unicelluar organisms engulf other cells

8. Excavata • Diplomonads& Parabasalids • Lack plastids and have modified mitochondria • Found in anaerobic environments

9. Diplomonads • Have modified mitchondria called mitosomes • Lack functional electron transport chain so they cannot use oxygen to help extract energy from carbohydrates and other organic molecules • Have 2 equal sized nuclei and multiple flagella

10. Parabasalids • Have reduced mitochondria called hydrogenosomes, generate some energy • Anaerobically release hydrogen gas as a by-product • Most well known parabasalid is Trchomonasvaginalis

11. Chromalveolates • Theory proposed on 2 lines of evidence • 1st : Some (not all) DNA sequence data suggest tht the chromaveolates form a monophyletic group • 2nd: Some data support the hypothesis that the chromalveolates originated more than a billion yrs ago, when a common ancestor of the group engulfed a single-celled photosynthetic red alga (endosymbosis)

12. Cont. • Red algae are thought to have originated by primary endosymbiosis the origin of the chromalveolates is referred to as secondary endosymbosis • Evidence: in many species the plastid structure and DNA indicate that they are of red agal origin

13. Apicompelxans • Parasites of animals and some cause serious human diseases • The parasites spread through their host as sporozoites (tiny infectious cells) • Have their name because the apex of the sporozite cell contains a complex of organells specialized for penetrating host cells and tissues • Not photosynthetic, recent data shows they can retain a modified plastid (apicoplast), most likely of red algal descent

14. Most have intricate life cycles sexual and asexual stages (require 2 or more host species for completion an example is the parasite Plasmadium which causes malaria

16. Brown Algae • Multicelluar & marine organisms • Commonly found along cool water temp. coasts • It’s brown or olive color is due to a carotenoid in plastid • Most commonly known as “seaweed”

17. Cont. • Brown algae: include species that have some of the most complex multi-celluar anatomy of all algae some have specialized organs that resemble those found in plants • Morphological and DNA evidence indicate that the similarites evolved independently in the algal and plant lineages and are thus analogous, not homologous

19. Cont. • Some species of brown algae are eaten, Laminaria (Japanese “kombu”) used in soups • The gel-forming substance in the cell walls (algin) is used to thicken many prcessed foods such as pudding, ice cream, and salad dressings

20. Rhizarians • Proposal based on results from molecular systematics • Members vary morphologically • Referred to as amoebas • Amoebas were once defined as protists that move and feed by means of pseudopdia, extension that may bulge from almost anywhere on the cell surface • Based on molecular systematics it is now clear amoebas do not constitute a monophyletic group but are dispersed across many distantly related eukaryotic taxa

21. Radiolarians • Have intricately symmetrical internal skeletons which are generally made of silica • The pseudopdia radiate from the body and are reinforced by a bundles of microtubules, covered by a layer of cytoplasm which engulf smaller micro-organisms that become attached to the pseudopodia

23. Red & Green Algae • “More than a billion years ago, heterotrophic protistaquired a cyanobacterialendosymbiont, and the photosynthetic descendents of this ancient protist evolved into red and green algae” • 474 million years ago the linage that produced green algae gave rise to land plants

24. Cont. • Red algae, green algae, and land plants make up the 4th eukaryotic supergroup, Archaeplastida • Monophyletic group that descended from ancient protists that engulfed a cyanbacterium

26. Unikonts • Diverse subgroup of eukaryotes (animals, fungi, and some protists) • Concern of the root of the eukaryotic tree • If the root of the tree were known, scientists could infer characteristics of the common ancestor of all eukaryotes

27. Cont. • In 2002, Alexandria Stechman & Thomas Cavalier Smith of Oxford University proposed a new hypothesis about the root of the eukaryotic tree • Hypothesis: the unikants were the 1st eukaryotes to diverge from other eukaryotes • Proposes that animal and fungi belong to an early-diverging group of eukaryotes • Protists that lack typical mitochondria diverged much later in the history of life Controversial and requires more supporting evidence to be widely accepted

28. Plasmdial Slime Molds • Brightly colored (yellow, orange) • Despite its size, the plasmodium is not multicellular it is a single mass of cytoplasm that is undivided by plasma membranes and that contains manay diploid nuclei • Plasmodium extends pseudopodia through moist soil, leaf mulch, or rotting logs engulfing food particles by phagosytosis

29. If habitat begins to dry or there is no food left the plasmodium stops growing and differentiates into friuting bodies which function in sexual reproduction

31. Protists Play a Key Role • These guys are everywhere! • Many have symbiotic relationships with species • Photosynthetic dinoflagellates provide nourishment to their symbiotic partners, the coral polyps that build coral reefs. Corals are highly diverse but also depend on the mutualisticprotistssymbionts that provide corals with an essential source of energy

32. Many protists are important producers, organisms that use energy from light (or inorganic chem.) to convert carbon dioxide to organic compunds • Producers are the base of ecological food webs

34. Key Words • Protist: an informal term applied to any eukaryote that not a plant, animal, or fungus • Mixotroph:combination of photosynthesis and heterotrophic nutrition • Secondary endosymbiosisa process in eukaryotic evolution in which a heterotrophic eukaryotic cell engulfed a photosynthetic eukaryotic cell, which srvived in a symbiotic relationship inside the heterotrophic cell • Exacata: one of the 5 subgraoups • Diplomonads: protists with modified mitochondria called mitsomes • Parabasalids: protists with reduces mitochondria called hydrogenosomes • Euglenozoan: protists that belong to a diverse clade that incledes predatory heterotrophs, photosynthetic autotrophs, and parasites • Kineoplastids: protists that have a single large mitochondrion that contains an organized mass of DNA called kinetoplast • Euglenid:aprotists that has a pocket at one end of the cell from which 1 or 2 flagella emerge • Chromalveolata: one of the 5 subgroups • Alveolates: groups of protistswhosmonophyly is well supported by molecular systematics • Dinoflagellates: portists that are characterized by cells that are reinforced by cellulose plates • Apicomplexans: parasites of animals, and some serious human diseases • Ciliates: a large group of varied protists named for their use of cilia to move and feed • Stramenopiles:a group of marine algae that include some of the most important photosynthetic organisms on the planet, as well as several heterotrophs • Diatoms: unicellular algae that have a unique glass-like wall made ofhydrated silica embedded in an organic matrix • Golden algae: a biflagellated, photosynthetic protist named for its color, which results from itsyellow and brown cartenoids

35. The End! Finally!