Meet the algae Protists: Algae Lecture 5 Spring 2014 Protist Phylogeny 1 Primary & Secondary Endosymbiosis 2 Algae - Not monophyletic What unites them as a group? Range from unicellular to multicellular From phytoplankton to kelp forests Primary Endosymbiosis Fig. 28.3 Fig. 28.2 Secondary Endosymbiosis 3 Endosymbiosis 4 A second case of primary endosymbiosis? Paulinella chromatophora Supergroup Rhizarian Cerozoans Fig. 28.2 Fig. 28.19 1
Photosynthetic pigments in chloroplasts Chlorophyll a Required for photosynthesis 5 Photosynthetic Pigments in Chloroplasts Why would so many different pigments evolve? 6 Accessory pigments Broadens the spectrum of light that can be absorbed Chlorophyll b Chlorophyll c Carotenoids (e.g. fucoxanthin, phycoerythrin, others) sunscreen, coloration 7 8 Primary productivity Productivity amount of biomass produced in a given area during a given period of time Fig. 28.27 Carbon cycling carbon sink Various mutualistic relationships 20% of world s photosynthesis 30% of world s photosynthesis Fig. 54,17 9 10 Algal blooms What limits growth of algae? Iron fertilization & diatoms Factors Warm surface temperatures High nutrients Low salinity Algal blooms Excessive growth of algae red tides, brown tides Toxins Fig 28.28 2
Euglenids Supergroup Excavata Clade Euglenozoa Key traits of clade: Typically two flagella, one long, one short crystalline rod in flagella 11 Fig. 28.7 Euglenids Phylum Euglenophyta ~ 900 described species Unicellular Photoautotrophs or mixotroph Light detector and eyespot Most freshwater Important part of food chain Key trait of Phylum Flagella (1 or 2) emerge from pocket at one end of cell 12 Fig. 28.7 Fig. 28.5 Dinoflagellates 13 Dinoflagellates 14 Supergroup Chromalveolata Clade Alveolata Key trait of clade: membrane bound sacs (alveoli) beneath the plasma membrane Phylum Dinophyta ~4000 described species Photosynthetic, mixotrophic & heterotrophic Unicellular Solitary & colonial Fig. 28.8 Phylum Dinophyta Key traits: 2 flagella positioning of flagella causes organism to spin Plates of cellulose armored Fig. 28.9 Fig. 28.8 Dinoflagellates: Ecological Roles 15, Golden & Brown Algae 16 Marine and freshwater phytoplankton Important primary producer Some mutualistic zooxanthellae - symbiotic dinoflagellate lacks armored plates Corals, sponges, jellyfish, octopuses and squids, snails, etc. Very important in coral reef ecosystems red tides Carotenoid pigments 20% of known dinoflagellates release toxins Cross section of coral polyp w/zooxanthellae Coral Supergroup Chromalveolata Clade Stramenopila Key traits of clade 2 flagellum 1 long with hairy (hollow tubes) projections, one short May be only reproductive cells or lost What non-photosynthetic protist belongs to the Stramenopiles? Fig. 28.12 3
17 18 Phylum Bacillariophyta ~100,000 species Unicellular Solitary or colonial Typically 20-200 microns in diameter or length Up to 2 millimeters long No flagella Secrete intricate shell Glass-like wall (shell, test) Hydrated silica in organic matrix Asexual reproduction limits Fig. 28.13 Lifestyle: Free floating, can sink or adjust depth Oils, amount of silica accumulated, projections no flagella Also grow on whales, turtle shells, aquatic plants, etc few terrestrial Carbon sink 19 Resting spores (cysts) - resistant stage Metabolically inactive spores Stored photosynthetic products Tough thickened cell walls Sink to the bottom of the sea 20 Golden Algae 21 Golden Algae 22 Phylum Chrysophyta ~1,000 described species Unicellular & solitary (most) Colonial (some) Some w/silica covering Cells w/two flagella, attached near one end Some mixotrophic Yellow & brown carotenoids Lifestyle Many planktonic Most freshwater, some marine Asexual & sexual reproduction Resting spores (cysts) Resistant stage Cyst made of silica Fig. 28.14 4
Brown Algae Phylum Phaeophyta ~ 1500 described species Multicellular Mostly marine Brown carotenoids seaweed More complex cellular structure than other algae Specialized tissues, organs From microscopic to huge (kelp forests) Among the largest photosynthetic organisms 23 Seaweeds Incl. brown, red & green red algae Thallus (algal body that is plantlike) Holdfast 24 Flotation bladder Brown Algae 25 Brown Algae 26 Many species live in the marine intertidal zone Cell walls of cellulose and alginic acid Alginic acid = gel-forming polysaccharides Protection from waves & dehydrtion Brown & green algae Kelp forests Deeper water Primarily temperate zone Generally not free floating Red algae & green algae Supergroup Archaeplastida Closest living relatives to land plants 475 million years ago green algae and land plants diverged Viridiplantae? 27 Red Algae Phylum Rhodophyta ~ 6,000 species Most multicellular Many filamentous Key traits Accessory pigment phycoerythrin (red carotenoid) No flagella 28 See Fig 28.20 5
Red Algae 29 30 Lifestyle Mostly marine Abundant in tropical waters Present in deep water Color varies by depth Coralline algae Reef-building algae Calcarous (calcium carbonate cell walls) Phylum Chlorophyta and Charophyceans ~ 17,000 described species Key traits: Chloroplasts similar to those found in plants Chlorophyll a & b Color not masked by carotenoids, so green Lifestyle Highly diverse Freshwater and marine Some planktonic Some terrestrial Chlamydomonas nivalis 31 Unicellular w/two flagella Unicellular, colonial 32 Mutualisms Lichen Sponges, freshwater protozoa Multicellular Unicellular, multinucleate, filamentous 33 Is Volvox a colonial species or a multicellular organism? 6