Humans are just one of the estimated 8.7 million species on Earth.
The diversity of life is one of the most striking aspects of our planet; hence knowing how many species inhabit Earth is among the most fundamental questions in science. Yet the answer to this question remains enigmatic, as efforts to sample the world's biodiversity to date have been limited and thus have precluded direct quantification of global species richness, and because indirect estimates rely on assumptions that have proven highly controversial.
Human beings may dominate the planet with our sprawling cities and far-reaching technology, but we are, in fact, just one species among some 8.7 million that live together on planet Earth.
One 2011 study published in the journal PLoS Biology estimated that "the various forms of life on the planet included 7.8 million species of animals, 298,000 species of plants, 611,000 species of mushrooms, mold and other fungi, 36,400 species of protozoa, and 27,500 species of algae or chromists." And it's worth noting that the researchers did not venture to put an estimate on the number of bacteria.