Ask A Scientist

How many animals are in the world? 

Asked by: Leah Elizabeth Bailey
School: Tioughnioga Riverside Academy, Whitney Point
Grade: 5
Teacher: Molly Babcock
Hobbies/Interests: Field hockey, softball
Career Interest: Masseuse, professional field hockey player, zoo worker

 

Answer from Dylan Horvath

Steward of Natural Areas, Binghamton University

Research Area: Wildlife biology/ecology
Interests/hobbies: Drawing, photography, singing, hiking

One of the wonderful things about living on planet Earth is that there is other life, and lots of it. How boring would it be if we never saw a bird flying or a squirrel scampering? The number and variety of species of life in an area is called biodiversity. Biodiversity is one of the most important characteristics of our planet. Throughout human history, animals have helped humans by serving as food and clothing, as well as inspiration for culture and technology. Most importantly, all animals are connected in some way to the natural processes, such as nutrient/water/energy cycles, that allow life to exist in the first place. One of the most basic questions of life is, "How many species are on our planet?" And we don't know!

Scientists are working to answer this question and are close (probably) with some types of animals. So far, taxonomists (scientists who classify species) have catalogued over one million animal species. Almost 60,000 of those are vertebrates, which include fish, birds, reptiles, amphibians and mammals. Invertebrates are much more numerous, as they include insects, of which there are almost one million species! If we include non-animal species, plants and microscopic life, scientists estimate there to be anywhere from two million to tens of millions of species. In Binghamton University’s Nature Preserve alone, you can find everything from salamanders to moles to butterflies to woodchucks!

As simple as it seems it should be, figuring out how many species live on our planet gets very complicated. From defining the word "species" to deciding how to classify species, the closer we look, the more we find exceptions to our definitions. Scientists used to look at species and try to define them, but it turns out some different species look exactly the same. Individuals of the same species can look very different. Domestic dog breeds vary from tiny Chihuahuas to Great Danes, yet all dogs are the same species. Molecular genetics, the study of genes in DNA, has greatly improved the way we classify species.

Of course, we can't label animals if we don't find them. Many animals live in places where it is difficult to find them, and most animals don't want to be found. Finding all the species on Earth is further complicated by the loss of species. Animals can go extinct naturally, but, especially in the last two hundred years, many animal species have become extinct soon after they are discovered and classified. Unfortunately, through habitat loss and other human influences, both intentional and unintentional, the planet is losing species before we can even discover them.

We may never know the exact number of species of animals or even all life on this planet. But that is the fun and importance of science -- to come as close as we can to figuring it out. As a scientist, diversity is the most fascinating thing about life, and I wish I could see every species on Earth.

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Last Updated: 9/25/14