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Lecture 11: Algae, Bryophytes and FernsALGAEGeneral features of AlgaeDiversity of Algae1. DiatomsDiatomsSlide 73. Red AlgaeWhy are Red algae red?Red algae4. Kelps or Brown Algae5. Green AlgaeGreen algaeSlide 14Benefits of AlgaeHarmful algaeCommercial uses of algaeKingdom PlantaePlants evolved from algaeAncestor of plants: Green AlgaeSlide 21Living on landB. PREVENTING WATER LOSSC. GETTING ENOUGH ENERGYD. Photosynthesis/water dilemmaE. MULTICELLULARITYF. SEXUAL REPRODUCTIONG. LIFE CYCLELife cycles: animals vs. plantsPlant life cycle: alternation of generationsSlide 31BRYOPHYTESBryophyte life cycleBryophytesBryophyte reproductionSlide 36Slide 37Bryophyte significanceFERNSFern life cycle: dominant sporophyteFern sporophyte morphologyFrondsFern Gametophyte generation (1n)Fern gametophyteSignificance of fernsLecture 11: Algae, Bryophytes and Ferns•Kingdom Protista: Algae•Red algae, diatoms, kelps, dinoflagellates, green algae•Significance of algae to humans•Kingdom Plantae: moving onto land•Features and challenges for living on land•Bryophytes•FernsALGAE•Algae belong to the Kingdom Protista•Algae are eukaryotes (cells have organelles)•Algae are mostly photosynthetic, like plants:–Have 4 kinds of photosynthetic pigments–Many accessory pigments – blue, red, brown, gold•Require moist environments because they lack a waxy cuticle (remember: cuticle prevents water loss in terrestrial plants)General features of Algae•Can be microscopic or macroscopic: size ranges from bacteria size to 50 meters long!•Lack vascular (conducting) tissues – No xylem or phloem–No true roots, stems or leaves•Modes of sexual reproduction:–Both sexual and asexual•Algae illustrate the importance of photosynthesis to the Earth’s ecology!Diversity of Algae•There are millions of algal species, but we’ll focus in these five groups:•Diatoms•Dinoflagellates•Red Algae•Kelps or Brown Algae•Green algae1. Diatoms1. Diatoms•Diatoms: Division Bacillariophyta•Large group of algae (many unidentified). Relatively recently evolved group•Habitat: Diatoms live in cool oceans•Structure: mostly unicellular, have silica in their cell wallsDiatoms•Very important for aquatic food chains: they provide phytoplanktonsunPhytoplankton  Zooplankton  small fish  larger fish mollusks whales•Can reproduce asexually for many generations, then sexually3. Red Algae3. Red Algae•Red algae: Division Rhodophyta (4000 species)•Are some of the oldest eukaryotic organisms on earth (2 billion year old fossils)•Abound in tropical, warm waters•Act as food and habitat for many marine species•Structure: from thin films to complex filamentous membranesWhy are Red algae red?•Accessory pigments! Phycobilins mask the Chlorophyll a – thus they look red.•Due to these accessory pigments, red algae can photosynthesize in deeper waters (at different light wavelengths).Red algae•Commercial uses: Carrageenan used for making ice cream, jellies, syrups, breads.•Also for lotions, toothpaste, pharmaceutical jellies.•Agar for growing bacteria and fungi for research purposes.•As food.4. Kelps or Brown Algae4. Kelps or Brown Algae•Kelps: Division Phaeophyta•Closely related to diatoms, also a recent group… but look very different from diatoms!•Habitat: rocky coasts in temperate zones or open seas (cold waters)•Structure: multicellular only•Holdfast, stipe, blade, air bladder•Up to 50 meters long5. Green Algae5. Green Algae•Division: Chlorophyta•Largest and most diverse group of algae•Habitat: found mostly in fresh waters and on land.•Float in rivers, lakes, reservoirs, creeks.•Can also live on rocks, trees, soilGreen algaeGreen algae•Sea lettuce (Ulva) lives in salt waters along the coast. •Structure of green algae: from •Single cells (Micrasterias)•Filaments•Colonies (Volvox)•Thalli (leaf-like shape)Green algaeGreen algae•Terrestrial plants arose from a green algal ancestor•Both have the same photosynthetic pigments (Chlorophyll a and b).•Some green algae have a cell wall made of cellulose•Cells divide similarlyBenefits of Algae•Beneficial algae:•They are the base of the aquatic food chain – photosynthetic organisms•Lichens: algae and fungi symbiosis•Also serve as shelters: Kelps form underwater forests; red alga form reefsHarmful algae•Excessive growth of algae causes:•Clogging of water ways, streams, filters… makes the water taste bad.•Can be toxic to animals•“Red tides” caused by dinoflagellatesCommercial uses of algae•Algin – a thickening agent for food processing (brown algae)•Carrageenan – foods, puddings, ice cream, toothpaste (red algae)•Iodine (brown algae)•Agar – for growth media used in research (red algae)•As food – red and brown algae •As plant fertilizers•Diatomaceous earth: used for filtering water, insulating, soundproofingKingdom Plantae•When moving from water to land, both plants and animals faced the same challenges, but evolved different ways to deal with themPlants evolved from algae•Algae cannot survive on land (only in moist environments)•Plants had to adapt (evolve) characteristics that would allow them to survive and live on dry land•Cooksonia is the earliestknown land plant (fossil)•It’s non-vascular andsimilar to today’s bryophytesAncestor of plants: Green Algae•The ancestor of land plants was probably a green alga: something like modern Coleochaete•1. They both have same photosyntheticpigments (Chlorophyll a & b, carotenes, etc.)•2. Both use starch to store photosynthetic products•3. Both have cellulose in their wall•4. Both have ‘alternation of generations’… •5. Both form a cell plate during cell divisionKingdom Plantae•Evolutionary tree of plants•From primitive advanced traitsBryophytesGreenalgaancestorFernsGymnospermsAngiospermsVascular Seeds Terrestrial FlowersLiving on land•Several environmental challenges had to be met by early plants in order to live on land…A. OBTAINING ENOUGH WATER•Plants evolved roots to anchor the plant•Roots to absorb water and dissolved mineralsB. PREVENTING WATER LOSS•Plants evolved a cuticle – waxy layer•Evolution of multicellular gametangia (sex organs) – helped protect gametes from drying out. • Evolution of a resistant coaton spores that prevents drying outC. GETTING ENOUGH ENERGY•In land, plants obtained enough sunlight for


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UMD BSCI 124 - Lecture 11: Algae, Bryophytes and Ferns

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