Which one among the following groups is the most abundant in terms of number of species identified?

Insects represent the most abundant group in terms of identified species. Currently, there are approximately 1 million described insect species, which accounts for roughly half of all known extant species on Earth. This dominance is further highlighted by the fact that a single order of insects, such as beetles, contains between 350,000 to 400,000 described species. In comparison, other groups have significantly lower counts of identified species: fungi have approximately 100,000 known species, and green plants (specifically flowering plants) are estimated at around 45,000 species in megadiverse regions like India [1]. While the total number of bacteria species is theorized to be vast, the number of formally described and identified bacterial species remains much lower than that of insects due to taxonomic challenges. Therefore, insects are the most abundant group among the identified species.

Sources

1. [1] Geography of India ,Majid Husain, (McGrawHill 9th ed.) > Chapter 5: Natural Vegetation and National Parks > WILDLIFE > p. 41