Protists: Algae Lecture 5 Spring 2014
Meet the algae
1 Protist Phylogeny Algae - Not monophyletic What unites them as a group? Range from unicellular to multicellular From phytoplankton to kelp forests Fig. 28.3
Primary & Secondary Endosymbiosis 2 Primary Endosymbiosis Fig. 28.2
Secondary Endosymbiosis 3 Fig. 28.2
Endosymbiosis 4 A second case of primary endosymbiosis? Paulinella chromatophora Supergroup Rhizarian Cerozoans Fig. 28.19
Photosynthetic pigments in chloroplasts 5 Chlorophyll a Required for photosynthesis Accessory pigments Broadens the spectrum of light that can be absorbed Chlorophyll b Chlorophyll c Carotenoids (e.g. fucoxanthin, phycoerythrin, others) sunscreen, coloration
Photosynthetic Pigments in Chloroplasts 6 Why would so many different pigments evolve?
Algae: Ecological Roles 7 Primary productivity Productivity amount of biomass produced in a given area during a given period of time Fig. 28.27 20% of world s photosynthesis 30% of world s photosynthesis
Algae: Ecological Roles 8 Carbon cycling carbon sink Various mutualistic relationships Fig. 54,17
Algae: Ecological Roles 9 Algal blooms What limits growth of algae? Factors Warm surface temperatures High nutrients Low salinity Algal blooms Excessive growth of algae red tides, brown tides Toxins
Algae: Ecological Roles 10 Iron fertilization & diatoms Fig 28.28
Supergroup Excavata Clade Euglenozoa Key traits of clade: Euglenids Typically two flagella, one long, one short crystalline rod in flagella 11 Fig. 28.7 Fig. 28.5
Phylum Euglenophyta ~ 900 described species Unicellular Photoautotrophs or mixotroph Light detector and eyespot Most freshwater Important part of food chain Key trait of Phylum Euglenids Flagella (1 or 2) emerge from pocket at one end of cell 12 Fig. 28.7
Dinoflagellates 13 Supergroup Chromalveolata Clade Alveolata Key trait of clade: membrane bound sacs (alveoli) beneath the plasma membrane Fig. 28.8 Phylum Dinophyta ~4000 described species Photosynthetic, mixotrophic & heterotrophic Unicellular Solitary & colonial Fig. 28.8
Dinoflagellates 14 Phylum Dinophyta Key traits: 2 flagella positioning of flagella causes organism to spin Plates of cellulose armored Fig. 28.9
Dinoflagellates: Ecological Roles 15 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
Diatoms, Golden & Brown Algae 16 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
Diatoms 17 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
Diatoms 18 Glass-like wall (shell, test) Hydrated silica in organic matrix Asexual reproduction limits Fig. 28.13
Diatoms 19 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
Diatoms 20 Resting spores (cysts) - resistant stage Metabolically inactive spores Stored photosynthetic products Tough thickened cell walls Sink to the bottom of the sea
Golden Algae 21 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 Fig. 28.14
Golden Algae 22 Lifestyle Many planktonic Most freshwater, some marine Asexual & sexual reproduction Resting spores (cysts) Resistant stage Cyst made of silica
Brown Algae 23 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
Seaweeds Incl. brown, red & green red algae Thallus (algal body that is plantlike) 24 Flotation bladder Holdfast
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 Algae 25 Brown & green algae
Brown Algae 26 Kelp forests Deeper water Primarily temperate zone Generally not free floating
Red algae & green algae 27 Supergroup Archaeplastida Closest living relatives to land plants 475 million years ago green algae and land plants diverged Viridiplantae?
Red Algae 28 Phylum Rhodophyta ~ 6,000 species Most multicellular Many filamentous Key traits Accessory pigment phycoerythrin (red carotenoid) No flagella See Fig 28.20
Red Algae 29 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)
Green Algae 30 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
Green Algae 31 Lifestyle Highly diverse Freshwater and marine Some planktonic Some terrestrial Chlamydomonas nivalis Mutualisms Lichen Sponges, freshwater protozoa
Green Algae 32 Unicellular w/two flagella Unicellular, colonial Multicellular Unicellular, multinucleate, filamentous
Green Algae 33 Is Volvox a colonial species or a multicellular organism?