Final answer:
Option (1), Insects, specifically the class Hexapoda, are the most numerous organisms on Earth, outnumbering all other classes of animals such as mammals, birds, and reptiles.
Step-by-step explanation:
The class of organisms that outnumbers all other animals on Earth is insects. Insects are arthropods that belong to the class Hexapoda and are incredibly diverse, with over a million described species. They can be found in almost all environments across the globe. From terrestrial habitats to aerial ecosystems, insects are the most numerous organisms in the world.
According to the Linnaean System of Classification, which has been in use for over two thousand years, organisms like mammals, insects, and reptiles are distinctly categorized based on their characteristics. Insects, which make up the subphylum Hexapoda, are so prolific that more than half of all known organisms are insects.
It's estimated that there may be more than 10 million insect species, most of them yet to be identified, showcasing the sheer dominance of insects on our planet.
While mammals like bats, primates, and various other species have unique qualities, they are significantly outnumbered by insects. Invertebrates, especially insects, are the reigning champions in terms of their population.