Protists Chapter 29

2 Protists Protists are the most diverse of the four eukaryotic kingdoms -Unicellular, colonial and multicellular groups The kingdom Protista is paraphyletic and grouped for convenience The 15 major protist phyla are grouped into seven major monophyletic groups

3 Protists

4 Protists (Cont.)

5 Eukaryotic Origins The nucleus and endoplasmic reticulum arose from infoldings of prokaryotic cell membrane

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7 General Biology of the Protists Cell surface -Plasma membrane -Extracellular material (ECM), in some -Diatoms – Silica shells Cysts -Dormant cell with resistant outer covering -Used for disease transmission

8 General Biology of the Protists Locomotion -Flagella -Cilia -Pseudopodia (“false feet”)

9 General Biology of the Protists Nutrition -Phototrophs -Heterotrophs -Mixotrophs are both phototrophic and heterotrophic

10 General Biology of the Protists Asexual reproduction -Binary fission -Budding -Schizogony = Multiple fission Sexual reproduction -Union of haploid gametes which are produced by meiosis

11 Diplomonads and Parabasalids Diplomonads -Have two nuclei -Giardia intestinalis Parabasalids -Have undulating membranes -Trichomonas vaginalis

12 Euglenozoa

13 Euglenozoa Kinetoplastids -Unique, single mitochondrion with DNA maxicircles and minicircles (RNA editing) -Trypanosomes cause human diseases -African sleeping sickness – Tsetse fly -Leishmaniasis – Sand fly -Difficult to control because organisms repeatedly change their protective coat

14 Euglenozoa

15 Alveolata Alveolata have flattened vesicles called alveoli -These function like Golgi bodies below the cell membrane

16 Alveolata Dinoflagellates -Unicellular with two unequal flagella -Live in aquatic environments “Blooms” are responsible for red tide -Most are photosynthetic -Do not appear to be directly related to any other phylum

17 Alveolata Dinoflagellates -Reproduction is primarily asexual -DNA is not complexed with histones -About 20 species produce powerful toxins that harm vertebrates -

18 Alveolata Apicomplexans -Spore-forming animal parasites -Apical complex is a unique arrangement of organelles at one end of the cell -Enables the cell to invade its host

19 Alveolata Plasmodium -An apicomplexan that causes malaria -Eradication of malaria 1. Elimination of mosquito vectors 2. Development of drugs 3. Development of vaccines -Organism has a very complex life cycle

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21 Alveolata Other apicomplexans -Gregarines -Found in the intestines of arthropods, annelids and mollusks -Toxoplasma gondii -Causes infections in humans with immunosuppression

22 Alveolata Ciliates -Feature large numbers of cilia arranged in longtitudinal rows or spirals around the cell -Have two types of vacuoles -Food vacuoles = Digestion of food -Contractile vacuoles = Regulation of water balance

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24 Alveolata Ciliates -Have two types of nuclei -Macronucleus = Divides by mitosis -Responsible for physiological functions -Micronucleus = Divides by meiosis -Involved in conjugation -Fusion of two cells of different mating types

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26 Stramenopila Stramenopiles have very fine hairs on their flagella -A few species have lost their hairs during evolution

27 Stramenopila Brown algae -Kelps -Grow in relatively shallow waters throughout the world -Life cycle involves alternation of generations -Sporophyte = Multicellular and diploid -Gametophyte = Multicellular and haploid

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29 Stramenopila Diatoms (Phylum Chrysophyta) -Unicellular organisms -Have unique double shells made of silica -Some move using raphes -Two long grooves lined with vibrating fibrils

30 Stramenopila

31 Stramenopila Oomycetes (“water molds”) -Were once considered fungi -Motile zoospores with two unequal flagella -Undergo sexual reproduction -Either parasites or saprobes -Phytophthora infestans -Irish potato famine ( )

32 Rhodophyta Rhodophyta, or red algae, range from microscopic to very large sizes -Lack flagella and centrioles -Have accessory photosynthetic pigments within phycobilisomes -Origin has been a source of controversy -Tentatively, treated as a sister clade of Chlorophyta (green algae)

33 Rhodophyta

34 Choanoflagellida Choanoflagellates are most like the common ancestor of all animals -Single emergent flagellum, surrounded by funnel-shaped contractile collar -Use collar to feed on bacteria -Have a surface tyrosine kinase receptor found in sponges

35 Choanoflagellida

36 Protists Without a Clade Amoebas are paraphyletic -Rhizopoda (True amoebas) -Move by means of cytoplasmic projections called pseudopods -Actinopoda (Radiolarians) -Glassy exoskeletons made of silica -Needlelike pseudopods

37 Protists Without a Clade

38 Protists Without a Clade Foraminifera are heterotrophic marine protists -Have pore-studded shells called tests, through which thin podia emerge -Use podia for swimming and feeding -Have complex life cycles with haploid and diploid generations -Limestones are rich in forams -White cliffs of Dover

39 Protists Without a Clade

40 Protists Without a Clade Slime molds -Were once considered fungi -Include two lineages 1. Plasmodial slime molds 2. Cellular slime molds

41 Protists Without a Clade 1. Plasmodial slime molds -Stream along as a plasmodium, a nonwalled, multinucleate mass of cytoplasm -Ingests bacteria and other organic material -When food or moisture is scarce, organism forms sporangia, where spores are produced

42 Protists Without a Clade

43 Protists Without a Clade 2. Cellular slime molds -Individual organisms behave as separate amoebas -Move through soil ingesting bacteria -When food is scarce, organisms aggregate to form a slug -Slug differentiates into a sorocarp

44 Protists Without a Clade