School of Sciences, Lautoka Campus BIO509 Botany Lecture 7: Other major algal phyla in Kingdom Protista

Other major algal phyla in Kingdom protista apart from green algae Phylum Chromophyta Phylum Rhodophyta Phylum Euglenophyta Phylum Dinophyta Phylum Charophyta

Learning outcomes Know the distinguishing features of Chromophyta, Rhodophyta, Dinophyta and Euglenophyta and Charophyta. Understand why Chromophyta, Rhodophyta, Dinophyta and Euglenophyta and Charophyta are different from Chlorophyta. Know the structure and function of holdfast, stipes, blades, bladders and thalli. Understand and appreciate the importance of these algae.

Phylum Chromophyta Phylum Chromophyta Roughly 7600 species. Mostly unicellular or colonial, few filamentous and tissue like forms. Have chlorophyll a and c, the colour of which is largely masked by abundance of pigment known as fucoxanthin. Food reserves are stored as oils, fats, mannitol and laminarian. Reproduction is asexual (fragmentation and zoospore formation and sexual (alternation of generations).

Phylum Chromophyta has several classes that share the several features Vaucheria Xanthophyceae - yellow green algae Chrysophyceae Golden-brown algae Bacillariophyceae Diatoms Phaeophyceae - Brown algae Dictyocha Diatoms Sargassum

Diatoms Around 5,600 living species Freshwater and marine inhabitants, some are terrestrial. Unicellular Two part cell wall structure known as frustules 95% of cell wall content is silica. May have one, two or many chloroplasts – chlorophyll a, c1 and c2 Lack flagella Have fine groves and pores which aid in movement.

Reproduction Mainly asexual Half of cells become progressively smaller through several generations until the original size is restored through a sexual process. Zygotes are known as auxospores

Human and Ecological relevance Diatoms are important components of phytoplankton. Primary source of food for many aquatic organisms. Diatoms form diatomaceous earth which is widely used in a variety of industrial and domestic uses. When in high concentration can be destructive to fish.

Brown algae More than 1,500 species of seaweeds. Multicellular body, but not organized into leaves and stems. Have holdfast, stipe and blades - thallus. Stipe often hollow structure has food conducting cells. Blades are photosynthetic. Fucoxanthin, chlorophyll a and c. Main food reserve is laminarian. Asexual reproduction by fragmentation Sexual reproduction involves alternation of generations.

Human and Ecological relevance Good iodine source. High in nitrogen and potassium and used as fertilizer. Used as livestock feed. Used as food Kelp produces algin that has the unique ability to regulate water ‘behaviour’ in a number of products: e.g. ice cream, salad dressing, beer, jelly beans, latex paints, penicillin suspension, etc.

Phylum Rhodophyta About 4000-6000 species. Mostly filamentous. Contains chlorophyll a that is masked by a pigment known as phycobillin and give the algae a red colour. Main food reserve is floridean starch and maninitol Complex life cycle, involves alternation of 3 generations – gametophyte, carposporophyte and tetrasporophyte

Human and Ecological relevance Used a food. Porphyra species – nori. Agar – is produced by the red alga Gelidium. It has gelatin-like consistency and is used in laboratories and media laboratories as a culture medium for growth of bacteria. It is also used in tissue culture. Bulking and thickening agent. Contain a number of substances of potential medicinal value.

Gracilaria species

Phylum Euglenophyta – the Euglenoids About 900 species. Unicellular. Mostly occur in freshwater, some are marine. Have chlorophyll a and b. Main food reserve is paramylon. Have single flagellum, contractile vacuole and red eyespot. Reproduction is asexual by binary fission.

Phylum Dinophyta – the Dinoflagellates About 2000- 4000 species. Unicellular biflagellate, bizarre in appearance. Have stiff cellulose plates forming a wall or theca. Contain chlorophylls a and c that is masked by pigment known as peridinin. Store food as starch. Reproduction is by cell divison. Sexual reproduction is very rare.

Human and Ecological relevance Cause toxic red tides that are harmful to fish and humans. Many dinoflagellate species are bioluminescent.

Phylum Charophyta – the Stoneworts Occurs as extensive meadows in freshwater lakes and streams with low phosphate concentrations. Branched filaments differentiated into apex, nodes, basal region. A single apical meristematic cell is responsible for length growth Have chlorophyll a and b and store food as starch.

Sexual reproduction is oogamous, antheridia are multicellular. Reproduction is primarly sexual. Sexual reproduction is oogamous, antheridia are multicellular. haplontic life cycle with anisomorpic gametes gametangia are covered with a protective, non-reproductive cell layers for protection, these cells originate from node cells Oogonium Antheridium

Meiosis in the zygote but probably only a single cell survives Mature antheridia are bright orange due to carotene in an outer layer of cells; biflagellated spermatozoids are produced in long strings Oogonia produce a single egg cell, protected by tube cells and crown cells The zygote forms with a thick, dark-brown wall; the zygote is released when the parent dies Meiosis in the zygote but probably only a single cell survives Attaches to substrate and new adult develops

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