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Protists- The Simplest Eukaryotes

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1 Protists- The Simplest Eukaryotes
Chapter 22 Protists- The Simplest Eukaryotes AP Biology Spring 2011

2 Objectives Describe the criteria for the Kingdom Protista
Describe the origin of the various protistans Tell how protists differ from bacteria Be able to compare protists with other eukaryotes Distinguish each of the major groups within the Protista

3 An Evolutionary Road Map
Chapter 22.1 An Evolutionary Road Map

4 Protists Characteristics
Protists: are the most like the first Eukaryotic cells Have a nucleus Most have mitochondria, ER, and Golgi bodies Ribosomes are larger than bacteria’s Have more than one chromosome, consisting of DNA with many proteins attached Have cytoskeleton (microtubules) Many have chloroplasts Divide by mitosis, meiosis, or both Eukaryotes

5 Protists A diverse group

6 Protists Characteristics
Most single celled There are colonial and multicelled species Some: Photoautotrophs Preditors Parasites Decomposers Many can form spores

7 Protists- A Hodgepodge
A kingdom that represents an evolutionary crossroads between prokaryotes and “higher” forms of life Recently the polyphyletic kingdom is being split into monophyletic groups Fig. 22.2

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9 Protists- A Hodgepodge
The 7 monophyletic groups: Diplomonads and Parabasalids Kinetoplastids and Euglenoids Foraminiferans and Radiolarians Stramenopiles and Alveolates Amoebozoans Red Algae Chlorophytes (green algae)

10 Chapter 22.2-22.4 Basal Groups 22.2: Parabasalids and Diplomonads
22.3: Euglenoids and Kinetoplastids 22.4: Forams and Radiolarians

11 22.2 Parabasalids and Diplomonads
Most evolutionary distant groups Consist of heterotrophic flagellates Are sac like or elongated and live in many oxygen poor or anaerobic habitats Have few mitochondria or none at all

12 22.2 Parabasalids and Diplomonads
Have equivalent of backbone Bundled microtubules extending the length of the cell Have flagella

13 22.2 Parabasalids and Diplomonads
Have 3 flagella at their anterior and and one at the trailing end Girardia lamblia: No lysosomes, mitochondria, or golgi bodies, does not form bipolar spindle at mitosis This lineage may have started more than a billion years ago Common intestinal parasite in humans and cattle Anaerobic but can survive as cysts outside bodies Cyst: resting stage with a covering of cell secretions

14 Chapter 22.3 Euglenoids and Kinetoplastids
Flagellated Single celled Thickened flagellum reinforced along nearly all lengths by a crystalline rod-shaped structure

15 Chapter 22.3 Euglenoids and Kinetoplastids
Free living cells of fresh water 1/3 of modern species are heterotrophs, other 2/3 are photoautotrophs that acquired chloroplasts Have a long and short flagellum Long flagellum is thicker and stiffened by an adjoining rod

16 Chapter 22.3 Euglenoids and Kinetoplastids
Eyespot: guides them toward light Pellicle: flexible, translucent cover, made of protein rich material Responsible for movement Contractile Vacuole: Euglenoid has a higher internal solute concentration Counteracts water’s tendency to diffuse in Reproduce by binary fission

17 Chapter 22.3 Euglenoids and Kinetoplastids
Heterotrophic, colourless flagellates Nearly all are parasites that can survive anaerobic and aerobic conditions Large mass of mitochondrial DNA, used for adjusting mode of ATP formation under different conditions Parasites Trypsanosoma, Leishmania (tropics), T. brucei (African sleeping sickness, tsetse fly is vector), T. cruzi (Chagas disease)

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19 22.4 Forams and Radiolarians
Faraminiferans: Start out in a one-chambered shell As single celled heterotrophs increase in size, most add more chambers and occupy them Psudopods interconnect Probe water and spaces between sand grains for bacteria and other prey Some harbor photosynthetic symbionts (dinoflagellates, golden alga, diatoms)

20 22.4 Forams and Radiolarians
Cell body has distinct outer zone with vacuoles that impart buoyancy and assist in prey capture and digestion Outer perforated shell made of short silica rods Most live in deep ocean water Some part of marine plankton

21 Chapter 22.5-22.7 The Alveolates 22.5:Ciliated Alveolates
22.6: Flagellated Alveolates 22.7: Malaria

22 The Alveolates Monophyletic group consisting of ciliates, dinoflagellates, apicomplexans Have small membrane bound sacs beneath the plasma membrane (alveoli)

23 22.5 Ciliated Alveolates Ciliates: Live in seas and fresh water
Most free-living heterotrophs 1/3 parasites or endosymbionts of animals Few are colonial

24 22.5 Ciliated Alveolates Cilia
Cover the surface of some species but are confined to specific regions on others Beat in synchronized patterns Moves body, directs food toward oral cavity

25 22.5 Ciliated Alveolates Paramecium: Cilia all over body surface
Gullet: starts at an oral depression Cilia sweep food-laden water inside Contractile vacuole: expel excess water from body Pellicle: array of flattened sacs under plasma membrane Store calcium ions which dictate ciliary beating Trichocysts: bottle shaped capsules hold a long shaft with a barb at the tip Defends against predetors

26 22.5 Ciliated Alveolates Ciliates:
Reproduce both sexually and asexually Micronucleus and macronucleus, both have to divide (not that efficient or effective) Conjugation occurs between ciliates

27 22.6 Flagellated Alveolates
Dinoflagellates: Live in freshwater and marine habitats Half are heterotrophs, half are photoautotrophs All deposit cellulose in their alveoli Often thick enough to form armor plates in pellicle Species that have thin deposits considered unarmored Most have 2 flagella Part of plankton Can undergo algal blooms when abundant nutrients Red tide: tint water red

28 22.6 Flagellated Alveolates
Apicomplexans: Parasitic alveolates Microtubular device that attaches to and pierces a host cell Adults have no flagella or cilia but their gametes are flagellated Ex. Plasmodium

29 22.7 Malaria Malaria symptoms:
Start when liver cells rupture and release meroziotes, cellular debris, and metabolic wastes into blood Shaking, chills, burning fever, sweats After one episode will relapse weeks to months later Later outcomes: jaundice, kidney failure, convulsions, coma

30 22.7 Malaria Bite of female Anopheles mosquitos can transmit a motile infective stage to human hosts Life cycle: Sporozoite travels from mosquito to blood vessels to liver cells Reproduces asexually by fission Some offspring (meroziotes) reproduce asexually in RBC, which they rupture and kill Other meroziotes develop into make and female gametocytes Gametocytes do not mature into gametes until they enter the gut of another mosquito

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32 22.7 Malaria Plasmodium is the protist responsible
As of 2007, every 30 seconds one African child dies of malaria

33 Chapter 22.8-22.9 The Stramenopiles
22.8: The (Mostly) Photosynthetic Stramenopliles 22.9: The Colourless Stramenopiles

34 Stramenopiles Have flagella that bristle with tinsel-like filaments
Single celled and multicelled Most photosynthetic

35 22.8 The (Mostly) Photosynthetic Stramenopliles
Chrysophytes: Free living photosynthetic cell with chloroplasts Includes golden algae, yellow-green algae, coccolithophores, and diatoms

36 22.8 The (Mostly) Photosynthetic Stramenopliles
Golden algae: Have covering of silica scales or other hard parts Producers in many fresh water habitats Yellow-brown because produce carotenoid fucoxanthin (masks chlorophylls)

37 22.8 The (Mostly) Photosynthetic Stramenopliles
Yellow-green algae: Do not make fucoxanthin Chlorophylls c gives yellowish-green colour Common in salt marshes and freshwater habitats Most immotile, gametes bear flagellum

38 22.8 The (Mostly) Photosynthetic Stramenopliles
Coccolithophores: Parts of calcium carbonate form under plasma membrane of coccolithophores Each year these cells die and sink to seafloor Form calcium carbonate deposits Deposits become part of limestone formations

39 22.8 The (Mostly) Photosynthetic Stramenopliles
Diatoms: Have silica “shell” which has two perforated parts that overlap Important primary producers, among fastest reproducers Release free oxygen Can convert bicarbonate back into carbon dioxide, makes them best at fixing carbon dioxide

40 22.8 The (Mostly) Photosynthetic Stramenopliles
Brown Algae: Olive-green and brown seaweeds Live in cool or temperate waters Range from microscopic species to giant kelp Diverse life cycles: sexual and asexual phases

41 22.9 The Colourless Stramenopiles
Oomycotes: (egg-fungi) Once classified as fungi because have similar growth pattern and feed the same way Spores give rise to a mesh of thin filaments that absorb nutrients from host tissues or decaying organic matter Nuclei are diploid, not haploid as fungi Cell wall has cellulose not chitin (fungi)

42 22.9 The Colourless Stramenopiles
Water molds: Decomposers of aquatic habitats Some parasites Some aquatic, others ruin plants on land Water mold on dead larval mayfly

43 22.10-22.11 The Closest Relatives of Land Plants 22.10: Red Algae
22.11 Green Algae

44 22.10 Red Algae Red Algae: Most live in warm marine currents and clear tropical seas Photoautotrophic algae: live in the deepest water Hold phycobilins and chlorphyll a Phycobilins are red accessory pigments Endosymbiosis: chloroplasts of red algae may have evolved from ancient cyanobacteria

45 22.10 Red Algae Most red algae show branching or sheet like patterns of multicellular growth True tissues do not form Life cycles diverse: asexual and sexual phases Gametes are not flagellated

46 22.11 Green Algae Green Algae: Closest relative of land plants
Most green algae now classified as chlorophytes, other group called charophytes (more closely related to land plants, discussed in that section)

47 22.11 Green Algae Green Algae (chlorophytes):
Chloroplasts contain chlorophylls a and b, store sugars as starch Cellulose fibers strengthen the cell walls Most aquatic Sheetlike, filamentous, cuplike, and colonial types Fig p. 364

48 Amoeboid Cells at the Crossroads
22.12 Amoeboid Cells at the Crossroads

49 Amoebozoa Shape shifters Use cytoplasmic extensions to move
Werewolves? NOOOOOOOOOOO Use cytoplasmic extensions to move Most solitary cells, some display communal behavior and cell differentiation that relate to fungi and animals Vast majority do not have cell walls, shell, or pellicle Most form pseudopods

50 Amoebas Soft-bodied, free living cells that move on pseudopods
Often prey on bacteria, other protists, or tiny multicelled animals Some parasitic: E.histolytica causes amoeba dysentery

51 Slime Molds “Social amoebas” Common in leaf litter and forest soil
Important in nutrient cycling Plasmodium: stage of life cycle Multinucleated mass arises from single diploid cell that undergoes repeated rounds of mitosis without cytoplasmic division Fans out in what appears to be a network of veins; mass digests and absorbs microbes and decaying organic matter in its path

52 Slime Molds Plasmodium:
When stressed, gives rise to many spore-bearing fruiting bodies Fruiting bodies consist of haploid spores on a cellular stalk When conditions improve spores germinate Amoeba like cells form that may bear flagella Fusion of 2 haploid cells results in diploid cell, which may give rise to new plasmodium

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54 On The Road to Multicellularity
Hallmark of multicellularity is the capacity of body to behave in a coordinated way, to respond to external stimuli as a unit Requires cell-to-cell communication May have originated with common amoeba like ancestor

55 Are you protisted out yet??

56 Summary Remember the 7 monophyletic groups
Characteristics of the different groups How is this kingdom unique? What does this kingdom seem to be leading up to?


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