"Food Web" Transcript
By Mark Sundaram
Welcome to the WeCreateEDU back-to-school knowledge swap in which we challenge fellow educational YouTubers to explain a topic outside of their usual areas of speciality! My channel is Alliterative and today I’ll be taking over things here at The Roving Naturalist to answer the question Sheryl posed to me: what is a food web, and why isn’t it a food chain?
This is actually the perfect topic for me because in my series the Endless Knot I usually talk about the origins of words and how they’re interconnected with the complex web of language, history, and culture. I generally take a highly interconnected approach rather than straightforward linear thinking, and that’s exactly what’s going on with food webs.
Most people are probably more familiar with the concept of the food chain, which shows the chain of organisms starting with producers like plants (also called autotrophs, but we’ll get to that later) which draw energy from the sun and nutrients from non-organic sources (such as carbon dioxide in the air), to herbivores that eat the plants, to carnivores that eat the herbivores, and so forth, all the way up to an apex predator. So essentially it shows the flow of energy and nutrients. But a food chain only shows one part of the story of how this works. Any given organism might have multiple consumers, and any given predator might have multiple types of prey. So a food web is the interaction between many different food chains, and that interaction can be enormously complex, which may require complex math like combinatorics and network theory and complex diagrams to understand. The decrease in numbers of one organism in a food web can have multiple effects in other parts of the same web. Now to more fully understand this bare-bones description of the food web and food chain, we need to backtrack a little and explore how scientists developed these ideas over the years and where the various terms and concepts came from.
Let’s start with the basic origins of the terms. The concept of the food web was first formally proposed by the highly influential ecologist Charles Elton in his 1927 book Animal Ecology, though as we’ll see there were forerunners who were thinking along the same lines. But Elton didn’t use the term food web, instead calling it a food cycle, a term that had already been used in the 19th century. A little after Elton’s book in 1932, Warder Clyde Allee, also a pioneering ecologist, used the term food web to describe this concept, and that’s the one that stuck. Both terms are apt in their own way as the word cycle from the Proto-Indo-European root word *kwel- which meant “to revolve, move around” refers to the nutrients being drawn from the soil and air by producer plants, to the consumer animals, and being returned back by the decomposers. But the complexities and interconnectedness of these systems is also well expressed by the word web, which comes from a root that means “to weave, move quickly” and is thus related to the English word weave, metaphorically making clear the difference between a food web and a food chain. The word food, by the way, comes from the root *pa- meaning “to protect, feed” and is related to such words as feed, forage, pasture, and pantry. As for the term food chain, Elton again had a hand in its popularization, though it was first used in print in 1920 by Scottish marine zoologist and oceanographer William Abbott Herdman, secretary of the Challenger Expedition Commission which basically kicked off the modern field of oceanography (and eventually lent its name to the Space Shuttle Challenger) and whose father-in-law botanist David Douglas lent his name to the Douglas fir. The etymology of the word chain, by the way, is uncertain, but it seems to come from the Latin word catena “chain” and may be related to Latin cassis “hunting net”, and ultimately from a root that means “to link, weave” — so, not so far from a web!
Now speaking of chains, the organization of organisms into chain structures goes back a long way, as in the medieval notion of the Great Chain of Being, known in Latin as scala naturae “ladder of nature”, which organized all of creation from God at the top through angels, humans in their social hierarchy, animals, plants, and minerals at the bottom. Conceptually this would lead to the phylogenic tree or tree of life, fundamental to Charles Darwin’s evolutionary theory. As early as the 8th to 9th century, Arabic writer al-Jahiz presaged the ideas of both food chains and the idea of the struggle for existence which is a foundation for evolution through natural selection (in fact that’s the title of a chapter of Darwin’s On the Origin of Species) when he wrote of how each animal is eaten by another in turn. In the 18th century, naturalist Richard Bradley similarly noted how parasitic insects prey upon each other in turn, an observation which was rendered into verse by satirical author Jonathan Swift as a metaphor for lesser writers when he wrote: “So, Nat’ralists observe, a Flea / Hath smaller Fleas that on him prey, / And these have smaller yet to bite ‘em, / And so proceed ad infinitum.” Bradley, by the way, was a pioneer in other ways as well, as he was also an early researcher into the pollination of plants by insects, was the first to publish recipes featuring pineapples in English, and invented an early form of the kaleidoscope for use in designing gardens, later perfected for less practical purposes by optics expert David Brewster, who in his turn was also a photography pioneer. Another 18th century scientist who described food chains was Carl Linnaeus, famous for inventing binomial nomenclature for the categorization different species, giving both a terrestrial and an aquatic example.
Food webs too had their early precursors, with 18th century Lutheran minister and writer John Bruckner even describing nature as “one continued web of life” and pointing out the necessity of a wide variety of plants, animals to eat those plants, and predators and scavengers to eat those animals in order to keep everything in balance. Bruckner also wrote about populations in ways that would later lay the groundwork for the likes of Thomas Malthus and even Karl Marx. Interestingly, Marx was a big fan of Charles Darwin, whose evolutionary writing influenced his own writing, and even wanted to dedicate a book to him (Darwin refused as he was worried Marx’s stance on religion would be detrimental to members of his family). And Darwin in his turn was a close reader of Malthus, and so since we’re talking about Darwin again, it may come as little surprise that he too wrote about the food web idea using such phrases as “web of life” and “web of complex relations” and describing a simple food web he observed during his voyage on the Beagle. Darwin also famously described a food chain in his On the Origin of Species in which bumblebees that pollinated red clover were preyed on by field mice, who were in turn kept in check by domestic cats, so that if it weren’t for the cats, the field mice would decimate the bumblebees, leaving the clover unpollinated. Except he didn’t actually write bumblebee but humblebee, which in fact is the older form of the name, with humble probably connected to the onomatopoeic word hum, before becoming bumblebee, bumble also being imitative in sound and perhaps related to the word boom which originally referred to a buzzing sound. Based on Darwin’s chain of connections, a later commentator reasoned with tongue firmly in cheek that if it weren’t for old maids the British Empire would fall, since old maids had many pet cats, who kept the field mice in check, who preyed on the bees, who pollinated the clover, which fed the cattle, which supplied the beef that fed the British sailors who protected the British Empire. And if you can figure out how to fit women and resisting patriarchy and colonialism and the British Empire into a joke to go here, you’re doing better than me!
Of course these kinds of complex interconnected relationships call out for graphical representations to illustrate them, so the terms food web and food chain are sometimes used to refer to these graphical representations. The first to produce such a diagram seems to have been Italian herpetologist and entomologist Lorenzo Camerano who published a generalized food web diagram in 1880, though no one seems to have picked up immediately on the idea. It wasn’t until the early 20th century when a number of other scientists independently hit upon the idea, that such diagrams began to appear with more regularity, such as a 1912 illustratiuon depicting the boll weevil complex, which seems to have been the first specific food web diagrammed, perhaps appropriate given that the word weevil comes from the same root as web (in the “move quickly” sense). This diagram was a proposal to eradicate the boll weevil, which attacked cotton crops, by encouraging its predators and parasites. The next year Victor Shelford, a foundational influence on the modern field of ecology as well as a teacher of Allee and major influence on Elton, published a book containing two food web diagrams which showed how communities tend toward equilibrium, and later Elton’s own book made such diagrams commonplace in the field. Another type of diagram that depicts this idea is the ecological pyramid, which can be used to show the number of organisms or biomass or energy at different levels of a food chain. The idea behind the pyramid comes from the work of 19th century German zoologist Carl Semper, who pointed out that as herbivores convert vegetation into flesh, and carnivores do likewise with the flesh of the herbivores, there is a loss of mass at each stage due to the oxidization of organic material. Similarly there is a loss of energy as it flows along the chain since some is lost to heat and so forth. The slope of the pyramid may be an indicator of the stability of a food web: the squatter the pyramid the more stable and the taller and thinner the less stable. And these different levels in the pyramid are called trophic levels, which is the next concept we need to turn to in order to understand food webs and food chains.
So up till now I’ve been using the term producer to refer to organisms like plants, which grow and metabolize by using energy from the sun and non-organic elements from their surroundings like the carbon dioxide in the air, and consumer to refer to herbivores and carnivores which get their food by eating other organisms. Those terms come from the work of August Thienemann, a German limnologist, limnology being the study of inland aquatic ecosystems, and by the way he also produced one of those early food web diagrams in 1926. In addition to producer and consumer, he also used the term reducer to refer to organisms that decompose dead organic matter as their food source. American ecologist Raymond Lindeman picked up on these terms, replacing reducer with decomposer, further developing the idea of trophic levels or levels in a food chain. The word trophic comes ultimately from Greek trophe meaning “food”, with the phrase trophic level being first used in Lindeman’s 1942 paper “The trophic-dynamic aspect of ecology”. Already in use for some time since the 19th century had been the terms autotroph, basically equivalent to producer, from Greek autos meaning “same, self”, heterotroph, equivalent to consumers, from Greek heteros meaning “other”, and mixotroph, which refers to things such as carnivorous plants which derive their food from both photosynthesis and consuming other organisms, from Greek mixis “mixing, mingling”. Now though these terms ultimately come from Greek, they were actually coined in German by German scientists, such as botanist Albert Bernhard Frank, who, in addition to introducing the term autotroph, also coined the term mycorrhiza, the symbiotic relationship between a fungus and the roots of a plant, and attempted to find a way to cultivate truffles for the king of Prussia. As for heterotroph and mixotroph, they may come from the work of one Wilhelm Pfeffer. In addition to, and I suppose in aid of, his biological work, Pfeffer was also something of a cinematography pioneer. He had been inspired by the chronophotography work of French physiologist Étienne-Jules Marey. Basically chronophotography is taking a series of photographs in quick succession in order to study movement. Marey famously used this technique to study the cat righting reflex, in other words why cats always land on their feet. Well, Pfeffer extended this idea, inventing time-lapse photography, so films could be produced showing things like plant growth so it could be studied. Time-lapse photography came to public attention when naturalist and nature documentary pioneer Percy Smith along with his producer Charles Urban, who made a career out of making documentaries and educational film, began using the technique, which is now a mainstay of nature documentaries. And these early educational films are the forerunners of educational YouTube videos like the one you’re watching right now.
Now before we wrap this up, let’s zoom out a bit and consider the field of ecology as a whole, since food webs and trophic levels are key concepts to this field, and because as with food webs it’s important to understand all the complex interrelations. And let’s start with some concepts related to the food web. So, an ecological niche is the position of an organism within an ecosystem, with reference to things like its food sources, predators, competition, and other environmental conditions. Of course different ecologists have understood this concept in different ways, but unsurprisingly food web pioneer Elton stressed the ways in which an organism impacts its interconnected environment. English gets the word niche, originally meaning a “shallow recess in a wall”, from French, but its ultimate origins are debated. It might come from Italian nicchio “seashell” from Latin mitulus “mussel”, or it might come from Old French nichier “to nestle, nest, build a nest” from Latin nidus “nest”, in which case it is related to the English word nest. Latin nidus from the root *ni-zdo- literally means “sit down” from the Proto-Indo-European roots *ni- “down” and *sed- “sit”. By the way, that root *ni-, in another compound form *ni-mno-, may come into Greek as limne “lake, pool”, the root of the word limnology, which you’ll remember Thienemann was studying when he produced one of those early food web diagrams and coined the terms producer and consumer. We get the word limnology, and really the field itself, from Swiss scientist François-Alphonse Forel, whose other claim to fame was, along with Italian scientist Michele Stefano de Rossi, developing the Rossi-Forel seismic scale for describing earthquake intensities, one of the first such scales, now superseded by the Richter scale devised by American seismologist and physicist Charles Richter.
The terms ecology and ecosystem are also Greek-derived. Greek oikos meaning “house, household” from a root that means “clan” is the first element of not only ecology and ecosystem but also economy when combined with the Greek word nomos meaning “custom, law”. In ancient Greece an oikonomos was the manager of a household and oikonomia meant “household management”, which was the original sense of English economy too, until it broadened to mean the management of a nation’s resources in the 17th century. So the word ecology, with the second element coming from Greek logos meaning “word, speech, story” but often used as the English ending -logy to mean “the study of”, is the study of the metaphorical house of living organisms, and ecosystem with the second element Greek systema “a whole compounded of parts” literally meaning “stand together” emphasises how all component parts in a natural environment are interconnected and work as a whole. The concept of the ecosystem was developed by British botanist and ecologist Arthur Tansley, and the name was coined at Tansley’s request by British botanist Arthur Roy Clapham. Tansley, by the way, put his botanical work on hold for a while to study psychology under Sigmund Freud and wrote a bestselling book aimed at a popular audience bringing the work of Freud and Jung to a general audience. The first pop psychologist?
As for the term ecology, it was coined by the German zoologist Ernst Haekel, of dubious legacy. Haekel was the first person to use the term “first world war” which believe it or not he used in 1914. He was also responsible for the now discredited recapitulation theory, which argues that stages of embryonic development recapitulate the evolutionary history of an organism so that earlier stages of an embryo resemble more “primitive” organisms, with the famous phrase “ontogeny recapitulates phylogeny”. And though Haekel was a big supporter and popularizer in Germany of Charles Darwin, he actually subscribed to Lamarckism, the theory of Darwin’s rival Jean-Baptiste Lamarck, which proposed that an organism can pass on characteristics it gained during its lifetime to its offspring, even stating that the social sciences were instances of “applied biology”, an idea that was later influential on Nazism. Furthermore, Haekel expressed his scientific racism in his theories of polygenism, that the different human races evolved independently, unsurprisingly judging that white Europeans were the most advanced. Again these ideas would later become influential on Nazism. Haekel’s idea of polygenism also had a linguistic component, influenced by the idea of the polygenesis of language put forward by August Schleicher who believed that the world’s languages could not be traced back to one original language. For Haekel, who believed in Lamarckism remember, that meant that the “best” languages conferred superior qualities to the “best” races, and I’m sure you can guess which languages he favoured. For his part, Schleicher claimed that he came to his ideas of the evolution of languages before he had even heard of Darwin’s ideas, but in any case began to arrange languages into genealogical trees inspired by the phylogenic trees used to show the evolutionary process. Schleicher, who was the first to attempt to compose a text in the reconstructed Proto-Indo-European language, now known as Schleicher’s fable, was also one of the first to use this tree model for language. Of course it turns out that this tree model doesn’t tell the whole story of language development as it doesn’t account for things like lateral transmission due to borrowing or language contact and the fact that languages don’t always develop from single isolated dialects but a from a range of dialects present at the same time. Nevertheless, the language tree still works fairly well to represent a simple model of language development.
So it’s interesting that we began this investigation into food webs by considering the impulse to arrange things into chains, and have kind of ended up in the same place with languages. Along the way we’ve used the etymology of words to help us understand concepts central to ecology, and their historical development, and how like food webs, all of these elements are arranged in interconnected webs. And I hope that, like the process of moving from a food chain to a much more complex, but more accurate, food web, this video has helped you gain a better understanding of the marvellous complexity of ecosystems and the ways we study them.