Dinoflagellates are unicellular, motile, photosynthetic protists. They have a well defined nucleus and possess two different flagella one transverse and the other is longitudinal. They belong to kingdom-Protista.

Pearl of ocean : Diatoms have a shinning silicified two valved covering or frustule. Because of their distinctive cell walls these are sometimes called the pearls of ocean.
Diatomaceous earth : It is pile of siliceous skeletons of diatoms which accumulates at the bottom of sea or oceans, being resistant to decay.

Some cyanobacteria or blue-green algae like Nostoc and Oscillatoria can tolerate adverse conditions including pollutants very well, as compared to other aquatic plants. This is due to the presence of mucilage covering, resistant proteins and the absence of sap vacuoles. They  release large quantity of spores, which are dispersed by air.

The two kingdom system is divided into Plantae and Animalia solely on the basis of their gross morphology. On the other hand, the five-kingdom classification is based upon more specific characters like cell structure, body structure, nutrition, evolutionary relationships, etc.

Neurospora (pink bread mould) is often called Drosophila of plant kingdom. It is haploid in nature which helps in immediate expression of every mutation. Beadle and Tatum used it as an experimental tool to find out that genes express their effect through synthesis of specific enzymes.