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  1. 1. Red tide—population explosion of certain types of dinoflagellates. Kills large amounts of fish. Depletes water of oxygen and releases toxins into the water. Apicomplexans • Apicomplexans – Are parasites of animals and some cause serious human diseases – Are so named because one end, the apex, contains a complex of organelles specialized for penetrating host cells and tissues – Have a nonphotosynthetic plastid, the apicoplast Flagellated Alveolates • Apicomplexans Plasmodium spp. Life cycle Malaria merozoites about to rupture a red blood cell 1
  2. 2. Plasmodium sp. life cycle sporozoite It takes two hosts to complete sporozoites merozoite male gametocyte in red blood cell Fig. 22-11, p.359 Stramenopiles • Stramenopiles have “hairy” and smooth flagella • The clade Stramenopila – Includes several groups of heterotrophs as well as certain groups of algae • Most stramenopiles – Have a “hairy” flagellum paired with a “smooth” flagellum during some part of their life cycle Hairy flagellum Smooth flagellum 5 µm 2
  3. 3. Photosynthetic Stramenopiles • Chrysophytes Chrysophytes Golden algae Yellow-green algae coccolithophores diatoms p.351b 3
  4. 4. • Diatoms are unicellular algae – With a unique two-part, glass-like wall of hydrated silica 3 µm • Diatoms are a major component of phytoplankton – And are highly diverse 50 µm Photosynthetic Stramenopiles Brown Algae • Brown algae, or phaeophytes – Are the largest and most complex algae – Are all multicellular, and most are marine 4
  5. 5. Photosynthetic Stramenopiles • Brown Algae bladder blade stipe holdfast Kelp -- Macrocystis Diversity of Kingdom Protista Phylum Phaeophyta: brown algae Underwater forests— habitats Kelp—food, habitats for aquatic organisms Pectin—used to make gelatin Alternation of Generations • A variety of life cycles – Have evolved among the multicellular algae • The most complex life cycles include an alternation of generations – The alternation of multicellular haploid and diploid forms 5
  6. 6. Colorless Stramenopiles • Oomycotes (egg fungi) Oogonium Colorless Stramenopiles •Oomycotes (egg fungi) water molds Phytophtora Saprolegnia Alternation of generations in Saprolegnia 6
  7. 7. Algae Red algae and green algae are the closest relatives of land plants • Over a billion years ago, a heterotrophic protist acquired a cyanobacterial endosymbiont – And the photosynthetic descendants of this ancient protist evolved into red algae and green algae Red Algae • Red algae – Are usually multicellular; the largest are seaweeds – Are the most abundant large algae in coastal waters of the tropics (b) Dulse (Palmaria palmata). This edible species has a “leafy” form. (c) A coralline alga. The cell walls of coralline algae are hardened by calcium carbonate. Some coralline algae are members of the biological communities around coral reefs. (a) Bonnemaisonia hamifera. This red alga has a filamentous form. 7
  8. 8. Red Algae • Red algae are reddish in color – Due to an accessory pigment call phycoerythrin, which masks the green of chlorophyll Green Algae • Two groups – Chlorophytes & Charophytes • All have chlorophylls a & b • Some are symbionts Green Algae • Chlorophytes 8
  9. 9. • Most chlorophytes – Live in fresh water, although many are marine • Other chlorophytes – Live in damp soil, as symbionts in lichens, or in snow Ulva – sea lettuce Fig. 22-19a1, p.364 Volvox colony Fig. 22-19c, p.364 9
  10. 10. Chlamydomonas Environment-resistant zygote Fig. 22-20b, p.365 Green Algae • Life Cycle Model Alteration of generations in Chlamydomonas e A thin-walled resistant zygote f zygote develops. (cross-section) d Diploid Stage meiosis and nuclear germination Haploid Stage fusion haploid cell haploid cell (+ strain) (– strain) g Mitosis occurs. Whether the resulting c cells develop into spores or gametes will depend on environmental conditions. b cytoplasmic fusion SEXUAL ASEXUAL ASEXUAL REPRODUCTION: REPRODUCTION: REPRODUCTION: Mainly when nitrogen levels are low and light is of More spores More spores a certain quality a are produced. are produced. and intensity, the + cells develop into _ gametes. + Gametes of different _ mating types meet. Fig. 22-20a, p.365 10
  11. 11. Amoebozoa • Amoebozoans have lobe-shaped pseudopodia • Amoebozoans – Are amoeba that have lobe-shaped, rather than threadlike, pseudopodia – Include gymnamoebas, entamoebas, and slime molds A. proteus Fig. 22-21, p.366 Heterotroph pseudopod 11
  12. 12. Amoebic dysentary Entamoeba histolytica Amoebozoa • Slime Molds • plasmodial (Myxomycetes) Plasmodia --- multinucleated cytoplasmic mass Fig. 22-22a, p.366 12
  13. 13. Hard times produce fruiting bodies Good times, spores germinate Produce ‘gametes’ – fusion of two Fruiting bodies produce haploid spores = new plasmodium Fig. 22-22b, p.366 • At one point in the life cycle – They form a mass called a plasmodium 3 The plasmodium erects 2 The plasmodium 1 The feeding stage stalked fruiting bodies (sporangia) takes a weblike form. is a multinucleate when conditions become harsh. plasmodium that lives on organic refuse. Mature Feeding plasmodium plasmodium (preparing to fruit) Zygote (2n) Young sporangium SYNGAMY 1 mm Mature Amoeboid cells sporangium (n) Key MEIOSIS Spores Germinating Haploid (n) (n) spore Diploid (2n) Flagellated cells Stalk (n) 7 The cells unite 6 These cells are in pairs (flagellated 5 The resistant spores disperse 4 with flagellated through the air to new locations either amoeboid or Within the bulbous and amoeboid with and germinate, becoming active flagellated; the two tips of the sporangia, amoeboid), forming haploid cells when conditions forms readily convert meiosis produces haploid diploid zygotes. are favorable. from one to the other. spores. Amoebozoa • Slime Molds • cellular slime molds (Amoeba-like) 13
  14. 14. clip Fig. 22-23f, p.367 • The life cycle of Dictyostelium, a cellular slime mold 9 In a favorable 1 In the feeding 2 During sexual repro- environment, amoebas stage of the life duction, two haploid emerge from the spore cycle, solitary haploid amoebas fuse and coats and begin feeding. amoebas engulf bacteria. form a zygote. 3 The zygote 8 Spores becomes a giant SYNGAMY are released. cell (not shown) by consuming 7 Other Emerging haploid amoebas. cells crawl Zygote Spores amoeba After developing a up the stalk (2n) (n) resistant wall, the SEXUAL and develop giant cell undergoes REPRODUCTION into spores. Solitary amoebas meiosis followed by 600 µm MEIOSIS (feeding stage) several mitotic Amoebas divisions. ASEXUAL REPRODUCTION Fruiting 4 The resistant bodies wall ruptures, releasing new Aggregated haploid amoebas. amoebas 5 When food is depleted, Migrating hundreds of amoebas aggregate congregate in response to a chemical attractant and form a sluglike aggregate (photo below left). Aggregate 6 The aggregate migrates for a formation is the beginning while and then stops. Some of the of asexual reproduction. cells dry up after forming a stalk that supports an asexual fruiting body. Key Haploid (n) Figure 28.27 200 µm Diploid (2n) 14
  15. 15. 1 Stalked, spore-producing structure releases spores. MITOTIC CELL DIVISION 2 Spores give rise to free-living MATURE amoeboid cells FRUITING that feed, grow, BODY and reproduce AGGREGATION by mitotic cell division. CULMINATION 3 When food gets scarce, the cells will stream together to form an aggregate that crawls like a slug. 4 The slug may either start developing or at once into a MIGRATING spore-bearing SLUG STAGE structure, or it may migrate elsewhere first. Fig. 22-23a, p.367 a Life cycle of Dictyostelium discoideum. midwife amoeba attracted to two stuck-together daughter cells p.367 LE 16-25 The evolution of multicellular organisms Gamete Locomotor cells Somatic cells Food- synthesizing cells Colony Early multicellular organism Later organism that Unicellular protist with specialized, interdepen- produces gametes dent cells 15