Question

According to five kingdom system, blue-green algae belong to:
a) Metaphyta
b) Monera
c) Protista
d) Algae

Answer 1

Hint: The five-kingdom classification of organisms given by Whittaker classifies organisms into: Monera, Protists, Fungi, Plantae and Animalia. Each kingdom has its separate characteristics. Monera includes all the bacteria. They are organisms with prokaryotic cell structure.

Complete answer:
To answer this question, we must understand the features of Blue-green Algae:
Blue-green algae, also called cyanobacteria, are heterogeneous prokaryotic organisms. They belong to the kingdom Monera. They are considered the first organism to release oxygen. They use solar energy and have pigments and use water as raw materials. They are believed to be organisms to convert reducing atmosphere to oxidizing atmosphere. They are slightly different from eubacteria, as they have chlorophyll. Cyanobacteria are believed to be developed by endosymbiosis.
They can be unicellular, filamentous and colonial. Some of the cyanobacteria can fix nitrogen. They require enzyme nitrogenase. This enzyme works in anaerobic condition. The nitrogen fixation takes place in heterocysts (example- Nostoc). These are special thick walled cells.
Around the multilayered cell wall, a gelatinous capsule is present. Inside the cell is cytoplasm which has two zones- outer zone and inner zone. Membranous structures called thylakoids are present in the outer zone. It contains pigments like chlorophyll, carotenoids, xanthophylls. The outer zone looks colored and hence called chromoplasm.
The inner zone is clearly called endoplasm. It contains circular genetic material called nucleoid. Ribosomes (70S) are also present.
No flagella are present in cyanobacteria. They perform photosynthesis. They are found in symbiotic association with certain other organisms.

Thus, the correct answer is option B- Monera.

Note: Scientists believed that the bigger eubacteria had taken in smaller bacteria. These smaller bacteria had pigments, hence cyanobacteria developed with thylakoids containing pigments. This is called endosymbiosis.