Question

Which of the following groups of organisms are included under chrysophytes?
A. Diatoms and desmids (golden algae)
B. Diatoms and dinoflagellates
C. Euglenoids
D. Slime moulds

Answer 1

Hint: Chrysophytes contain chlorophyll a, chlorophyll c, and are often referred to as golden algae owing to the presence of fucoxanthin, a yellowish-brown carotenoid pigment.

Complete Answer:
- Chrysophytes are plant-like protists that can be found in marine and freshwater habitats and are mostly deficient in calcium. This includes diatoms (bacillariophyta) and golden-brown algae (chrysophyceae). This class includes around 200 genera and 1,000 species, most of which are found in fresh waters.
- They are microscopic and actively float in water currents (plankton). The majority of them are photosynthetic. Since Chrysophyta includes so many organisms, there is no typical cell structure.
- Some of the cell walls are primarily made up of cellulose, with significant quantities of silica, while some are amoeboid without cell walls. In the diatoms, the cell walls form two thin alternating shells that blend together. The walls are enclosed with silica and thus the walls are indestructible. If flagella are present, there may be one or two; if there are two, they may or may not be identical.
- Diatoms are capable of sexual reproduction, but chrysophytes typically replicate by cell division. Chrysophyte members tend to be photosynthetic, but some, particularly golden algae, become heterotrophic when there is insufficient light or when the food dissolved is abundant.

Thus the correct answer is option A i.e., Diatoms and desmids (golden algae).

Note: Diatoms and golden-brown algae are of considerable significance as part of the plankton and nanoplankton that form the base of the aquatic food chain. Diatoms are the chief producers of the oceans.