Big Numbers

Bacteria-July-17-BlogSomething like five billion different species have existed since life began on Earth. Almost all (an estimated 99%) of these are now extinct. However, there are roughly 14 million species alive today. But how many individual lifeforms? Which being is the most successful in terms of population size? Let’s find out…

Mammals. There are 5,488 different species of known mammal. Of these, four species stand out – Pigs, cattle and sheep each have populations of over a billion, and there are 7.5 billion humans. We think that there are approximately 130 billion individual mammals living in the wild which makes the total number of mammals something like 140 billion or so.

Birds. There are more species of bird than mammal, with 9,703 known so far. Just like with mammals, the domesticated species are the most common. It’s estimated that the domestic chicken has a population of 19 billion – that’s two and a half chickens for every person on the planet. The wild bird population is harder to guess because it varies throughout the year. Our best estimate is about 150 billion individuals making a total of around 170 billion birds.

Reptiles and amphibians. There are over 10,000 species of reptile and about 7,000 amphibians. However, as we don’t keep many reptiles for food or as pets, their numbers are much lower than those of birds and mammals. My best guess – approximately 34 billion.

Fish-July-17Fish. More than 33,000 different species of fish exist. They have the advantage of living in water, which covers three quarters of the Earth. Unsurprisingly, they are the most populous vertebrate and we think there are something like 3.5 trillion individuals alive. That’s 20 times the number of birds!

Invertebrates. There are so many different types of invertebrate that estimating their numbers would be nigh on impossible. If we just take insects, possibly the most successful invertebrate, we find that there are 8 million or so different species and about 1.5 quadrillion individuals. Add to this worms, arachnids, molluscs, sponges… My best guess – 5 quadrillion.

Plants. We know that there are 3 trillion or so trees on the planet, but trees are the biggest and most obvious plant. Taking all other 300,000 or so plant species into account, how many individuals would that be? Let’s say each species has a billion members – that would make a total of 300 trillion.

Bacteria. Finally we come to the most basic of life form. These are tiny things so you’d probably expect them to be the most populous – and you’d be right! One gram of soil contains 400 million of them and an average human has 39 trillion of them inside! If you weighed all the bacteria on the planet they would weigh more than all the plants and animals combined. Scientists have worked out that there are 5,000,000,000,000,000,000,000,000,000,000 (that’s 5 nonillion) individual bacteria on Earth. That’s 50 times the number of stars in the observable universe!

So know, courtesy of Education Quizzes, you know roughly how many individuals live on our planet. Seeing such numbers really makes you see how insignificant a life form us humans really are, in the grand scheme of things.

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