Monobiontic life cycle: only one generation can grow and divide mitotically.

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1 Monobiontic life cycle: only one generation can grow and divide mitotically. Example in the green algae Ulothrix the only diploid phase is limited to the single-celled zygote. It can undergo meiosis to produce gamete. Dibiontic life cycle: both haploid and diploid generations can grow and divide mitotically. The generations can be heteromorphic or isomorphic. An example is the green algae Ulva which is dibiontic and heteromorphic.

2 Algae - usefulness to humans, harmful blooms, lifecycles Phytoplankton - phyto (plant) plankter (wanderer) microscopic floating algae. Important as first tier of the food chain because they are photosynthetic. Productivity is 3.26 quintillion (3.26 x ) kcal of photosynthate /year or 4x crop land total Important for many unique chemicals they produce that we use for food, industrial uses, pharmaceuticals, etc. Negative impact: harmful algal blooms and toxins produced

3 Algae general features. All are protists They require moist environments because they lack a cuticle They lack vascular tissues Algae are photosynthetic and reproduce both sexually and asexually

4 Beneficial Aspects of Algae Food for humans, food for fish in aquaculture, animal feed Soil fertilizers and conditioners in agriculture Treatment of waste water Diatomaceous earth (= diatoms) Chalk deposits Phycocolloids (agar, carrageenan from red algae; alginates from brown algae) Drugs Model system for research Phycobiliproteins for fluorescence microscopy

5 Seaweeds are an important part of the human diet in several parts of the world. It is a good source of iodine. One million metric tons of the brown algla Laminaria is harvested per year in China for iodine. It is used to treat goiter in humans. Nori - The red alga Porphyra is used in Japanese cuisine. Limu - the Polynesians in Hawaii used more than 75 species of seaweed in their diet.

6 Dulce - The red alga Palmaria palmate has been eaten in the British Isles for more than 1200 years. Irish moss, a red alga, Chondrus crispus, when boiled with milk produces a jelly dessert that the French call blancmange

7 Nevertheless, algae do not have much direct nutritional value for humans - they are mostly indigestible. Industrial uses: Diatomaceous earth (diatomite) is a great filter material. It is used in cement, grout, paper, paint, pesticides, etc. and it is also an abrasive. The original formulation of dynamite is diatomaceous earth and nitroglycerin

8 Agar - polysaccharide from red algae (agarose is purified from agar). It is used in baking to make icing. It is not digestible and is also used as a laxative. Carrageenan - polysaccharide from red algae (Irish moss). Named after the town of Carragheen, Co. Cork. It is added to most foods including ice cream, bread, toothpaste etc. Harvested off the coast of Maine. Algin - polymer from brown algae is a major component of the cell wall. One tablespoon added to 1 liter of water gives the consistency of honey. Several species of brown algae are harvested for algin including Laminaria, Macrocyctis, Fucus, and Ascophyllum. Laminaria Fucus

9 Harmful algal blooms Red tide in Maine

10 Red tide in La Jolla, CA

11 Amnesic shellfish poisoning Pseudonitzschia a diatom produces domoic acid Domoic acid - the neurotoxin associated with amnesic shellfish poisoning. It bioaccumulates in plankton feeders such as shellfish and fish. It causes permanent short-term memory loss, brain damage and death. It can kill marine birds and mammals. It activates AMPA kainate receptors allowing Ca 2+ influx. First discovered in Nova Scotia, where it killed 3 people in Has been implicated in sea bird and mammal deaths in California. Sea lion affected by domoic acid

12 Ciguatera fish poisoning Gambierdiscus toxicus a dinoflagellate Ciguatoxin accumulates in reef fishes (that eat herbivorous fish). Occurs in tropical waters. Symptoms include nausea, diarrhea, neurologial symptoms such as paresthesia ( pins and needles sensation), muscle aches, ataxia (loss of control of body movements), and allodynia (pain from non-painful stimulation). Symptoms can last from days to years. Sometimes misdiagnosed as multiple sclerosis. There is no effective treatment, the toxin(s) affects ion channels in the nervous system.

13 Diarrhetic shellfish poisoning, gastrointestinal symptoms caused by eating shellfish that have fed on Dinophysis sp., an alveolate. Problem in Spain, Ireland and around Mediteranean. The toxin is okadaic acid. okadaic acid Dinophysis acuminata A Dinophysis bloom in Norway

14 Brevitoxin and Neurotoxic shellfish poisoning. Restricted to the Gulf of Mexico and Caribbean. Exposure can occur through eating shellfish or breathing sea spray. Has affected fisheries of Florida and Texas, has killed off manatees and has affected human health. Toxins open voltage gated Na + channels and cause depolarization. The toxins are heat and acid stable. Causes respiratory irritation, cough, bronchoconstriction, and skin rashes or acute gastroenteritis if exposure is through shellfish. Symptoms subside after a few days. Karenia brevis (formerly Gymnodinium breve) is a dinoflagellate and causes Florida red tides.

15 Saxitoxin and Paralytic Shellfish Poisoning. Occurs over a wide range, on both east and west coasts of US. In Alaska, the butterclam bioaccumulates saxitoxin. STX has been implicated in the deaths of humpback whales and Mediterranean monk seals. Saxitoxins block Na + channels. Alexandrium tamarense is a dinoflagellate

16 Fusion of isogametes (plasmogamy and karyogamy) zygote resting stage Fertilization Diploid (2 n) Haploid ( n) Meiosis Life cycle of green algae Ulothrix is Monobiontic. The filaments are haploid. The zygote is only capable of meiosis. gametangium with isogametes vegetative cell filament chloroplast meiospores mitospores escape from parent cell escaping isogametes meiospores escape ASEXUAL CYCLE mitospore settles + filament new filament arises through mitosis holdfast cell meiospore settles; new filament arises through mitosis

17 Life cycle of green algae Ulva is dibiontic and isomorphic. The gametophyte (haploid generation produces anisogametes (the two types differ in size).

18 Life cycle of green algae (chlorophyte) Derbesia: it is dibiontic and heteromorphic. The sporophyte (diploid) appears different then the gametophyte. The gametophytes produce anisogametes.

19 Diatoms are different they are monobiontic but the dominant generation is the sporophyte. Repeated mitotic divisions of the sporophyte result in smaller cells. These go through meiosis to produce gametes (isogametes) that fuse and produce a new sporophyte generation that makes a new wall.

20 asexual reproduction by mitosis; all cells are 2n Meiosis forms cell wall zygote fusion of isogametes to produce a diploid zygote isogametes sexual reproduction by meiosis, leading to isogametes

21 Red Algae Large group with 3900 species They are red because they have phycobilisomes, their red color is due to phycoerythrin. Red algae store fixed carbon as floridean starch (a branched glucose polymer). They lack plasmodesmata but have cellular connections called pit connections. They have complex life cycles than completely lack swimming cells. Polysiphonia

22 General life cycle of red alga, it is dibiontic and heteromorphic.

23 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.

24 Brown algae, closely related to diatoms. They are all multicellular and almost all marine algae. They have holdfast, stipe, blade and air bladder, are up to 50 meters long. The brown alga Fucus.

25 The brown alga Ectocarpus Is dibiontic and isomorphic. The gametes are isogametes. n Meiosis meiospores meiotic sporangia The life cycle is not too complicated. mitotic sporangia 2n gametangia Sporophyte Haploid (n) Diploid (2n) mitospores 2n n n isogametes n Gamete fusion 2n zygote asexual mitospores in sporangia n Gametophytes Sporophyte

26 Life cycle of the brown alga Fucus. This is dibiontic, heteromorphic and the gametes are not similar, it is oogamous. Antheridia - male gametangia (structure of the gametophyte that makes gametes) Oogonia - female gametangia

27 Next time - Bryophytes (the mosses)