RANK

SPECIES

EST. POPULATION

DESCRIPTION

1

Bacteria (various species)

5 nonillion (5,000,000,000,000,000,000,000,000,000)

Bacteria are single-celled microorganisms that thrive in diverse environments, playing critical roles in ecosystems.

2

Ant (Formicidae)

1 quadrillion (1,000,000,000,000,000)

Ants are social insects found almost everywhere on Earth, forming colonies that can contain millions of individuals.

3

Fruit Fly (Drosophila melanogaster)

100 billion

Widely used in genetic research, fruit flies have high reproductive rates and are found in many habitats worldwide.

4

Domestic Chicken (Gallus gallus domesticus)

25 billion

Chickens are the most populous bird species, raised globally for their meat and eggs.

5

Red Imported Fire Ant (Solenopsis invicta)

20 billion

This invasive species is known for its aggressive behavior and is found in many parts of the southern United States.

6

Human (Homo sapiens)

8 billion

Humans are the most populous primate species, impacting ecosystems and the planet in unprecedented ways.

7

Silverfish (Lepisma saccharina)

1 billion

Silverfish are wingless insects that thrive in humid environments, often found in homes and basements.

8

Pigeon (Columba livia)

300 million

Pigeons are highly adaptable birds that thrive in urban environments, often found in cities worldwide.

9

Domestic Rat (Rattus norvegicus)

200 million (in various habitats)

Common in urban areas, rats thrive alongside humans, adapting to various environments.

10

House Mouse (Mus musculus)

200 million (in various habitats)

Common in urban areas, house mice thrive alongside humans, adapting to various environments.