Which animal is the MOST common in kingdom?

It's impossible to say definitively which animal is the *most* common in the entire animal kingdom. There are just too many species and the numbers fluctuate wildly.

Here's why it's tricky:

* Vast Diversity: The animal kingdom is incredibly diverse, with millions of species ranging from microscopic organisms to massive whales.

* Difficult to Count: It's extremely challenging to accurately count the populations of every species, especially for insects, nematodes, and other small creatures.

* Habitat Variation: The distribution of species is uneven. Certain animals, like ants, are incredibly abundant in specific habitats, while others are much rarer.

However, some strong contenders for the title of "most common" include:

* Insects: There are more insects than any other animal group, with an estimated 10 quintillion (10,000,000,000,000,000,000) individuals on Earth.

* Nematodes (roundworms): These tiny worms are found in nearly every habitat, and their sheer numbers are staggering.

* Copepods: These microscopic crustaceans are found in vast quantities in oceans and freshwater lakes.

* Bacteria: While not technically animals, bacteria are incredibly abundant and essential to life on Earth.

Ultimately, the "most common" animal depends on how you define "common" and what scale you're looking at.