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The algae contain chloroplasts that are similar in structure to cyanobacteria. Chloroplasts contain circular DNA like that in cyanobacteria and are interpreted as representing reduced endosymbiotic cyanobacteria. However, the exact origin of the chloroplasts is different among separate lineages of algae, reflecting their acquisition during ...
Haploid algal cells (containing only one copy of their DNA) can fuse with other haploid cells to form diploid zygotes. When filamentous algae do this, they form bridges between cells, and leave empty cell walls behind that can be easily distinguished under the light microscope. This process is called conjugation and occurs for example in Spirogyra.
Valonia ventricosa, also known as bubble algae, sea grape, [2] or sailor's eyeballs, [3] is a species of algae found in oceans throughout the world in tropical and subtropical regions, within the phylum Chlorophyta. It is one of the largest known unicellular organisms. [3] [4] Valonia ventricosa in the Red Sea
Micrasterias displays a bilateral symmetry, with two mirror image semi-cells joined by a narrow isthmus containing the nucleus of the organism. This dual semi-cell structure is unique to the group of green algae to which Micrasterias belongs. Each semi-cell contains a single large chloroplast, the site of photosynthesis for Micrasterias.
In some brown algae, the pith region includes a core of elongated cells that resemble the phloem of vascular plants both in structure and function. In others (such as Nereocystis ), the center of the stipe is hollow and filled with gas that serves to keep that part of the alga buoyant.
The female organ, called an oogonium is a large oval structure with an envelope of spirally arranged, bright green filaments of cells. The male organ or is also large, bright yellow or red in colour, spherical in shape, and is usually termed an antheridium, though some workers regard it as a multiple structure rather than a single organ. The ...
Chlorella is a genus of about thirteen species of single-celled green algae of the division Chlorophyta. The cells are spherical in shape, about 2 to 10 μm in diameter, and are without flagella. Their chloroplasts contain the green photosynthetic pigments chlorophyll-a and -b.
The superficially similar Rhizochromulina was once included here, but is now given its own order based on differences in the structure of the flagellate stage. Other members are non-motile. Cells may be naked and embedded in mucilage, such as Chrysosaccus, or coccoid and surrounded by a cell wall, as in Chrysosphaera.