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Algae

الكلية كلية العلوم     القسم قسم علوم الحياة     المرحلة 2
أستاذ المادة اياد محمد جبر المعموري       08/01/2016 21:01:18


1-Rhodophyta

phylum (division) of the kingdom Protista consisting of the photosynthetic organisms commonly known as red algae. Most of the world s seaweeds belong to this group. Members of the division have a characteristic clear red or purplish color imparted by accessory pigments called phycobilins, unique to the red algae and the cyanobacteria. The chloroplasts of red algae are believed to be derived from cyanobacteria that formed an ancient symbiotic relationship with the algae.

1-2 General characteristics
Red algae have a number of general characteristics that in combination distinguish them from other eukaryotic groups:
1-Absence of flagella and centrioles.
2-Floridean starch as a storage product and the storage of starch in the cytoplasm
3-Phycoerythrin, phycocyanin, and allophycocyanin as accessory pigments
4-Unstacked thylakoids in plastids
5-No chloroplast endoplasmic reticulum





1-3 Structure












1-4 Life cycle and reproduction
They display alternation of generations; in addition to gametophyte generation, many have two sporophyte generations, the carposporophyte-producing carpospores, which germinate into a tetrasporophyte – this produces spore tetrads, which dissociate and germinate into gametophytes. The gametophyte is typically (but not always) identical to the tetrasporophyte.










1-5 Ecology
Rhodophyta are aquatic organisms that exist in both freshwater and marine habitats, although mostly marine. They are found in tropical, temperate, and cold-water environments. Rhodophyta tend to live at greater depths of water than Charophyta and Chlorophyta. This is because Rhodophyta pigments absorb blue light, which penetrates water to a greater depth than other wavelengths. Rhodophyta are primary producers. They provide habitats for other aquatic organisms. In addition, Rhodophyta play an important part in the establishment and maintenance of coral reefs. Those species found in coral reefs are called coralline algae; they secrete a shell of carbonite around themselves.
1-6 Classification
1-6-1 Class Bangiophyceae









Figure 2: Batrachospermum
1-6-2 Class Floridiophyceae







Figure 3: Polysiphonia
1-7 Economic Importance
1-8 Rhodophyta Chemistry
1-9 Important terms
1-carposporophyte (2n): diploid stage that forms from fertilization and produces asexual carpospores
2-tetrasporophyte (2n): diploid stage that forms from carpospores, and produces haploid tetraspores through meiosis
3-gametophyte (1n): haploid stage that forms from tetraspores, and produces gametes
4-spermatia: non-motile sperm
5-trichogyne: female stalk that catches spermatia

1-10 Rhodophyta Biotechnology
Polysaccharides making up their wall, agars and carrageenans are interesting for diverse domains (microbiology, food-processing, cosmetic...)







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