Objectives for Lecture 20 Protista green algae Understand the difference between primary and secondary endosymbiosis and be able to state which of the algal groups have chloroplasts that arose by primary or by secondary endosymbiosis Green Alga Plant Other algae Green The bulk of evidence indicates that all chloroplasts resulted from a single primary endosymbiotic event Inherit chloroplast from cyano bacteria Other algae At least three separate secondary endosymbiotic events led to plastids in different groups of algae Get chloroplast from eating another photosynthetic cell Understand the differences between the three basic life cycle types zygotic meiosis gametic meiosis and sporic meiosis or alternation of generations Know which life cycle is characteristic of animals and angiosperms 1 Zygotic occurs in zygote the diploid cell from the fusion of male and female gametes gametes a haploid reproductive cell gametes fuse in pairs forming diploid zygotes occurs in fungi and some algae Diploid cells 2 Gametic meiosis the life cycle most familiar to us Occur mainly in animals mammals Occurs in animals some protists and algae Look at picture in notes Haploi d Cells Diplo id cells 3 Sporic meiosis or alteration of generations with independent sporophyte and gametophytes Gametophyte the haploid gamete producing generation Spore a reproductive cell usually unicellular capable of developing into an adult without fusion with another cell Sporophyte the diploid spore producing generation occurs in plaint and many algae Haploi d cells Diploid cells Know the features that green algae share with land plants the evidence that land plants evolved from green algae 1 green algae use chlorophyll a and b in photosynthesis 2 the chloroplasts of green algae are enclosed in a double membrane This second characteristic indicates that the chloroplasts evolved from endosymbiosis of a prokaryote as is the case with higher plants Also analysis of genetic material indicates a high degree of relatedness between green algae and terrestrial plants 2 The resemblance of green algae to the bryophytes and vas cular plants which are adapted for life on land has long been recognized The green algae bryophytes and vascular plants are the only groups of organisms that contain chlorophylls a and b and store starch their food reserve inside plastids Some but not all green algae are like bryophytes and vascular plants in having firm cell walls composed of cellulose hemicelluloses and pectic substances In addition the microscopic structure of the flagellated reproductive cells in some green algae resem bles that of plant sperm cells These features in conjunction with molecular data strongly indicate that green algae and land plants bryophytes and vascular plants form a monophyletic group known as the Viridiplantae viridophytes or green plants 3 Be able to name the five evolutionary trends within the green algae 1 Chlorophyll Chl a b and carotenoids 2 Pigments 3 Cell wall composition cellulose 4 Morphological features ex such as flagella Mobile to immotile flagellum 5 DNA sequence Know the life cycle of the unicellular green alga Chlamydomonas zygotic meiosis look at picture in notes Understand the meaning of the terms isogamy and oogamy and what the benefits of oogamy are Isogamy both gametes same size and small Oogamy Egg large and nonmotile sperm small and motile Parent can invest more resource Evolutionarily more advanced Sperm is small but has flagella Egg stores food a lot of nutrients are needed to make sure offspring are strong healthy Know that Ulva sea lettuce has alternation of generations with independent gametophytes and sporophytes Gametangium structure in which gametes are formed Sporangium structure in which spore are formed Know the approximate date at which plants colonized the land Objectives for Lecture 21 Protista Other algae Know what phytoplankton are and what the biological and ecological importance is they are mostly aquatic planktonic algae plankton tiny photosynthetic cells and animals suspended in the water compose 50 of photosynthetic activity on earth major food for other bigger animals base of the food chain in open seas Know what rides tides are what organisms cause them and what their environmental and health effects are When phytoplankton populations aren t held in check there can be red tides toxic blooms Not all red tides are red Dinoflagellates cause them They are toxic red tide organisms Red tides are due to blooms of dinoflagellates some of which produce neurotoxins cause fish kills and paralytic shellfish poisoning in people Be able to name the polysaccharides from red and brown algae that are economically important as emulsifying agents colloidal stabilizers and thickening agents Brown algae The kelps are a source of alginates Used as thickening agents colloid stabilizers in food textile cosmetic pharmaceutical paper and welding industries Red algae Agar capsules cosmetics culture medium gel electrophoresis Carrageenan stabilizes paints cosmetics and dairy products a clarifying agent in beer Some red algae the coralline algae deposit calcium carbonate in their cell walls Can grow at 200m depth For each of the groups of algae Euglenoids Cryptomonads dinoflagellates diatoms brown algae and red algae know what their distinguishing characteristics are in terms of whether they are unicellular or multicellular what their mode of nutrition is and what photosynthetic pigments they have what their cell wall is composed of where they are found fresh vs salt water whether they have flagella and what mode of sexual reproduction they use Unicellula r or multi Single cellular mostly unicellular Tiny Unicellula r Mostly unicellular Mostly unicellular Euglenoids Have a flagellum and stigma eye spots Cryptomona ds have two flagellates Dinoflagellat es Mobile have two flagella different direction Mode of nutritio n Fresh or salt water Photosynt hetic pigment Chlorophy ll a b and carotenoid s Cell wall composed of No cell wall can take up particles Sexual repro Reproduce by division Some are particle eaters Chl a c and phycobilli n Four layers membrane bound chlorpolast Photosy nthetic ingest food too 50 Chl a c and carotenoid s Most have a cell wall cellulose plates SECONDARY ENDOSYMBIOSIS Nucleomorph residue of endosymbiont nuclei Sexual reproduction is rare Examples of endosymbionts zooxanthellae have lost their wall and occur as endosymbionts in sponges jellyfish sea anemones corals and other
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