Question

Which of the following groups of algae, belongs to class rhodophyceae?
A. Laminaria, Fucus, Porphyra, Volvox
B. Gelidium, Porphyra, Dictyota, Fucus
C. Gracilaria, Gelidium, Porphyra, Polysiphonia
D. Volvox, Spirogyra, Ulothrix, Sargassum
E. Sargassum, Laminaria, Fucus, Dictyota

Answer 1

Hint: Rhodophyceae are a group of algae also called Red algae. They have a water soluble pigment phycoerythrin which gives red colour to their thallus.

Complete answer:
- Rhodophyceae are a eukaryotic algae which live in freshwater and marine environments.
- The red pigment phycoerythrin gives a red colour to the pigment chlorophyll a. Other pigments are beta carotene, fucoxanthin, etc.
- They show an oogamous type of reproduction where male gametes are non flagellate and female gametes have a long and receptive neck.
- Their life cycle shows alternation of generations. Their main food source is floridean starch.

Let us analyse the options to find the correct answer
Option A: Laminaria and Fucus belong to the class Brown Algae whereas Porphyra belongs to red algae and Volvox belongs to chlorophyceae green algae. Therefore, this is the incorrect option.
Option B: Gelidium and Porphyra belong to class rhodophyceae but Dictyota and fucus belong to Brown Algae. Therefore, this is the incorrect option.
Option C: Gracilaria, Gelidium, Porphyra and Polysiphonia all belong to class rhodophyceae. Hence, this is the correct answer.
Option D: Volvox belongs to chlorophyceae green algae, Spirogyra belongs to zygnematophyceae, Ulothrix belongs to chlorophyceae green algae and Sargassum belongs to brown algae. Therefore, this is the incorrect option.
Option E: Sargassum belongs to brown algae, Laminaria, Fucus, and Dictyota belong to the class Brown Algae. Therefore, this is the incorrect option.

Thus, the correct option is C) Gracilaria, Gelidium, Porphyra, Polysiphonia.

Additional Information:
- Currently, 7000 species of Red algae have been described.
- Double cell walls are present in red algae.
- Red algae do not have flagella or centriole their whole life.
- Spore formation takes place in their reproduction.

Note: Importance of Rhodophyceae:
- They produce polyphenols and phycobiliproteins which are antioxidants.
- Used and eaten in salads and soups.
- Gracilaria, Gelidium, Porphyra are used as water binding agents, anticoagulants and as thickening agents.