In “Ecology Stories Episode One: What is Biodiversity?“, Mike and Debby Kaspari write:
Each person’s pursuit of biophilia leads to a discovery: some places are richer in animals and plants and microbes, others less so. This discovery is captured in the word “biodiversity”. In biodiversity, we count and compare the kinds of living things in a place. The resulting number is a measure of a place’s Biodiversity. To get to that number requires careful study. For example, generations of ant scientists on Barro Colorado Island in Panama have, altogether, counted about 400 species of ants living in its rainforests. Both of US have seen 102 species of birds around our house in Norman Oklahoma. Microbiologists estimate there may be 50,000 species of bacteria in a gram of soil. Biodiversity can vary a lot depending on what you are counting, and where.
Taxonomists are scientists whose job it is to recognize and name species, building a catalogue of biodiversity. They do so by becoming so familiar with a group—be it ants, birds, grasses, or microbes—that they recognize consistent differences among them. differences used to tell apart species are called characters.