Biology · Plant Kingdom · NEET
They are brown because of a pigment called fucoxanthin. Brown algae still have green chlorophyll a and chlorophyll c inside, but the extra amount of the xanthophyll pigment fucoxanthin hides the green and gives a brown or olive colour. NEET has directly asked this: fucoxanthin belongs to Phaeophyceae. Remember: Fucoxanthin = Phaeophyceae (both have the letter combos to link brown).
Both. Brown algae store food as complex carbohydrates in the form of laminarin OR mannitol. NEET often makes wrong-match traps here, like pairing Ulothrix (a green alga) with mannitol. Only brown algae (Ectocarpus, Laminaria, Fucus, Sargassum) store mannitol/laminarin. Green algae store starch; red algae store floridean starch.
The vegetative cells have a wall of cellulose, usually covered on the outside by a gelatinous coating of algin. Algin is a hydrocolloid (a water-holding substance) taken from brown algae for commercial use. Do not confuse: algin comes from BROWN algae, carrageen comes from RED algae. NEET reverses these to trick you.
Fucoxanthin is the brown pigment of Phaeophyceae (brown algae). Phycoerythrin (r-phycoerythrin) is the red pigment of Rhodophyceae (red algae). A 2023 NEET question asked exactly this pair: fucoxanthin = Phaeophyceae, phycoerythrin = Rhodophyceae. Link them by first letter feel: Fuco = brown class, Phyco-erythrin (erythro = red) = red class.
Vegetative reproduction is usually by fragmentation. Asexual reproduction is by biflagellate zoospores (two flagella that are unequal in length and attached laterally, meaning on the side). Sexual reproduction can be isogamous, anisogamous or oogamous. NEET point: brown algae make biflagellate zoospores, and the two flagella are unequal and lateral.
Yes. Kelps are large brown algae. Phaeophyceae range in size from very small simple filaments like Ectocarpus up to giant kelps that can grow more than 100 metres long. So brown algae include both tiny forms and the biggest algae in the sea.
Ectocarpus, Dictyota, Laminaria, Sargassum and Fucus. Laminaria and Sargassum are also used as food. If you see these genera in a match-the-column question, mark them as Phaeophyceae (brown algae).
Which classes of algae possess pigment fucoxanthin and pigment phycoerythrin, respectively?
Which of the following algae contains mannitol as reserve food material?
Read the following statements about Phaeophyceae and choose the correct set. A. Asexual reproduction usually by biflagellate zoospores. B. Sexual reproduction is oogamous only. C. Stored food is mannitol or laminarin. D. Major pigments are chlorophyll a, c, carotenoids and xanthophyll. E. Vegetative cells have a cellulosic wall covered outside by a gelatinous coating of algin.
Try the real previous-year questions from this chapter — each with the answer and a full solution.
Phaeophyceae is the class of brown algae. The brown colour comes from the pigment fucoxanthin.
Laminarin or mannitol. These are the stored complex carbohydrates of Phaeophyceae.
Algin is a hydrocolloid (water-holding substance) that coats the cell wall of brown algae and is used commercially. It comes only from brown algae, not red algae.
Laminaria and Sargassum are used as food. Other common examples are Ectocarpus, Dictyota and Fucus.
Two flagella (biflagellate) that are unequal in length and attached laterally, meaning on the side of the cell.
