Simone Lawson
The class of animals that constitutes the largest biomass on Earth is a contentious topic, with various estimates and categories to consider. Some sources suggest that insects, specifically arthropods like copepods, could constitute the largest biomass among animals, with one source stating that insects may even exceed mammals. However, others claim that cows have the largest biomass among animal species, with an estimated biomass of over 650 million tonnes. It's important to note that animals represent less than 0.5% of the total biomass on Earth, with plants and microbes constituting a significant portion of the global biomass.
| Characteristics | Values |
|---|---|
| Class | Arthropods |
| Phylum | Arthropoda |
| Habitat | Aquatic, terrestrial, or parasitic |
| Body | Segmented, with a fused head and thorax region (cephalothorax) |
| Appendages | Jointed, with two pairs of antennae and five pairs of biramous appendages |
| Excretion | Through green glands or antennal glands |
| Respiration | Through gills or the general body surface |
| Eyesight | A pair of compound eyes |
| Development | Indirect, with a larval stage |
| Species | About 1 million described species, with most being insects |
| Subphyla | Chelicerata (arachnids), Crustacea (crustaceans), Hexapoda (insects and springtails), and Myriapoda (millipedes and centipedes) |
| Extinct Subphyla | Trilobitomorpha (trilobites) |
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What You'll Learn
Plants make up the majority of biomass on Earth
Plants are one of the three groups of life that make up the Earth's biomass, the other two being microbes and animals. Microbes can be further broken down into bacteria, archaea, protists, and viruses. Bacteria are the second-largest composition of biomass, as they can be found everywhere, from the human gut to deep in the Earth's crust. Researchers at the University of Georgia estimate there are 5 nonillion bacteria on the planet. Protists are mostly unicellular and are essential components of the food chain. Archaea are single-celled microorganisms that thrive in extreme environments, from high temperatures above 100°C in geysers to highly saline, acidic, or alkaline conditions. Viruses, though not technically living things, have microscopic effects that cannot be understated.
Animal biomass, though visually dominant, makes up only 0.47% of all biomass. Humans, for example, only make up 0.01% of all biomass on the planet. The largest group of invertebrates is arthropods, which include insects, arachnids, and crustaceans. The category of chordates includes wild mammals, wild birds, livestock, humans, and fish. Across 65,000 living species, nearly half are bony fish like piranhas, salmon, or seahorses. Cow biomass, for example, exceeds 650 million tonnes, while humans only average about 80 million tonnes.
Human activities are having a significant impact on Earth's biomass. In the past decades, we have lost significant forest cover to make room for agricultural land use and livestock production, leading to a decline in biodiversity in virtually every region. Anthropogenic mass (human-made material) is expected to exceed all living biomass on Earth.
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Marine biomass outweighs land animal biomass
In contrast, terrestrial primary producers, such as forests, grow and reproduce slowly, so a much larger mass is needed to achieve the same rate of primary production. Marine biomass includes arthropods, such as copepods, which account for about 1 billion tonnes of carbon, and fish, which account for about 0.7 billion tonnes. Marine mammals such as whales and dolphins account for about 0.006 billion tonnes of carbon.
Land animals account for about 500 million tonnes of carbon, or about 20% of the biomass of animals on Earth. Terrestrial arthropods account for about 150 million tonnes, most of which is found in the topsoil. Land mammals account for about 180 million tonnes, most of which are humans (about 80 million tonnes) and domesticated mammals (about 90 million tonnes). Wild terrestrial mammals account for only about 3 million tonnes, less than 2% of the total mammalian biomass on land.
The biomass of consumers in the oceans (about 5 Gt C) is larger than that of producers (about 1 Gt C). Conversely, on land, the biomass of primary producers (about 450 Gt C) is much larger than that of primary and secondary consumers (about 20 Gt C). The mass of humans is an order of magnitude greater than that of all wild mammals combined. Humans have had a significant impact on the overall biomass of most important taxa, including a huge decrease in total biomass of wild animals and a gain in total mammalian biomass due to livestock husbandry.
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Humans contribute a small mass compared to other animals
Plants make up the majority of the Earth's biomass, constituting over 80% of all life biomass on Earth. Bacteria are the second-largest composition of biomass, followed by fungi, which is the third most abundant type of life. Animal biomass, on the other hand, constitutes only a tiny portion of the Earth's living organisms, making up only 0.37% to 0.47% of all biomass.
Within the animal kingdom, humans contribute a relatively small mass compared to other animals. Humans, at 0.06 gigatons, constitute a minuscule fraction of the Earth's biomass, estimated to be just 1/10,000 of the total. In comparison, the biomass of certain Antarctic krill species, such as Euphausia superba, is similar to that of humans, at approximately 0.05 gigatons. A single species of termite can surpass the biomass of all birds, highlighting the relatively small contribution of humans to the overall biomass.
While humans have a small biomass compared to other animal species, their activities have had a significant impact on the Earth's biomass. Human activities, such as deforestation, agricultural land use, and livestock production, have resulted in the loss of significant forest cover and a decline in biodiversity. Human activity has also contributed to the extinction of megafauna, with over 100 genera perishing, including large mammals such as camels, horses, and sabre cats.
Despite their small biomass, humans and livestock dominate mammalian biomass. Humans and their livestock outweigh all other wild mammals by 20-fold and account for 59.9% of all mammal biomass on Earth. This dominance is a result of human activities, such as the development of fire technologies, weapons, and agriculture, which began approximately 50,000 years ago.
In conclusion, while humans contribute a small mass compared to other animals in terms of biomass, their activities have had a disproportionate impact on the Earth's biomass. Human actions have altered the distribution of biomass, leading to the decline of certain species and the dominance of others. Understanding this dynamic is crucial for preserving the diversity of all the biomass on Earth and ensuring the sustainability of our planet's ecosystems.
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Bacteria and Archaea are the most common prokaryotes
Plants make up the majority of biomass on Earth, with 320,000 species contributing to ecosystems through their vital photosynthetic processes. Fungi are the third most abundant form of life, with an estimated millions of species yet to be discovered. Animals make up only 0.47% of all biomass.
Among the animals, humans, cows, and Antarctic Krill are some of the most widespread. However, when it comes to the broader classification of life, Bacteria and Archaea, which are prokaryotes, are the most common. They are single-celled microorganisms with no nucleus, and they are found everywhere, from our guts to deep in the Earth's crust. Bacteria were one of the first life forms to appear on Earth, and researchers estimate there are five nonillion bacteria on the planet.
Archaea, similar to bacteria, are also single-celled microorganisms. They have unique properties that separate them from bacteria and eukaryotes. For instance, archaea have an abundant use of ether-linked lipids in their cell membranes, which are more chemically stable than the lipids found in bacteria. Archaea are further classified into multiple recognised phyla, but classification is challenging as most have not been studied in a laboratory and have only been detected through gene sequences in environmental samples.
Both Bacteria and Archaea play an important role in human health and environmental processes. They are known as decomposers, breaking down plants, animals, and their organic compounds. Additionally, in aqueous environments, prokaryotes, mainly Archaea, produce methane. Some prokaryotic species, however, can be harmful to human health, acting as pathogens that cause diseases such as brucellosis and necrotizing fasciitis.
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Antarctic Krill is the only wild species in the running for the largest biomass
Plants make up the majority of the Earth's biomass, with 320,000 species contributing to ecosystems worldwide. Fungi are the third most abundant form of life, with an estimated millions of species yet to be discovered. Animals make up only 0.47% of all biomass.
Among the animal kingdom, humans contribute a relatively small mass. A global population of 6.9 billion people averaging 50kg each amounts to roughly 350 million tonnes. The biomass of cows, however, far exceeds that of humans, with a total of over 650 million tonnes.
The only wild species that comes close to these figures is Antarctic Krill. A 2009 estimate placed their biomass at 379 million tonnes, though aspects of this shrimp-like creature's ecology are still unknown. More recent estimates place their biomass at between 300 and 500 million tonnes, making them the largest biomass of any multicellular wild animal species on the planet.
Antarctic Krill (Euphausia superba) is a keystone species in Southern Ocean ecosystems, preyed upon by larger animals like whales, seals, seabirds, and fish. They live in large schools, sometimes reaching densities of 10,000–30,000 animals per cubic metre. They feed on minute phytoplankton, using the primary production energy derived from the sun to sustain their pelagic life cycle.
Antarctic Krill is an important grazer of plankton and plays a key role in biogeochemical cycles, such as carbon export and iron recycling. However, their biomass may be declining due to the effects of global warming. Krill, especially in the early stages of development, seem to require pack ice structures to survive. The pack ice provides natural cave-like features that the krill uses to evade predators. Warmer temperatures are also causing ocean acidification, which impacts the krill's exoskeleton and prevents the hatching of juvenile krill.
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Frequently asked questions
While there is no clear consensus on which class of animals constitutes the largest biomass on Earth, the following information can be considered:
- Cows constitute the largest biomass among all species.
- Insects may exceed mammals when considered collectively.
- Arthropods, a large group of invertebrates, may constitute the largest biomass.
- Marine animals have a greater biomass than marine autotrophs.
- Prokaryotes, including bacteria and archaea, dominate the global biomass.
Biomass is the mass of a group of organisms, typically expressed as the average mass per unit area or the total mass in a community. It can include microorganisms, plants, or animals.
Some examples of animal biomass include:
- Marine arthropods like copepods account for about 1 billion tonnes of animal biomass.
- Fish constitute about 0.7 billion tonnes of animal biomass.
- Marine mammals such as whales and dolphins make up about 0.006 billion tonnes.
- Land animals, including humans and domesticated mammals, account for approximately 500 million tonnes.
Animals represent less than 0.5% of the total biomass on Earth, with about 2 billion tonnes of carbon (C) in total.
Human activities, such as deforestation for agriculture and livestock production, have significantly impacted Earth's biomass. Biodiversity is declining in virtually every region, and human-made materials (technomass) now outweigh all living biomass on Earth, with plastic alone exceeding the mass of all land and marine animals combined.
