Autotroph

An autotroph is a type of organism that is able to produce its own nutrient supply through the conversion of basic inorganic materials readily available in the environment. Autotrophs are the only living things that produce their own food rather than consuming other things; indeed, the name autotroph comes from the Greek for "self-feeding." The group consists mostly of land and sea plants.

Autotrophs play a critical, although often unacknowledged, role in the maintenance of all ecosystems. All living things need energy, energy that is created by taking in food and converting that into work, which is nothing more than energy applied. Although it may not occur to most people, plants get hungry. When most plants, from a backyard weed to a sequoia tree, get hungry, they cannot hunt, trap, or prepare food (carnivorous plants being an exception). Rather, plants use what is available—sunlight, carbon dioxide from the air, and water either from the ground or from rain—to produce sufficient nutrition to maintain life.

Autotrophs, in turn, become the primary food source for many examples of heterotrophs; that is, all the other living creatures who eat other organisms for food, including all animal species from insects to birds to rabbits to humans. Thus, the chemical process through which autotrophs feed themselves, which is known as photosynthesis, is actually responsible for sustaining nature’s entire food chain—99 percent of living things directly or indirectly rely on autotrophs for food. As nature’s only pure food producers, then, autotrophs assume a significant place in any discussion of maintaining an ecosystem, a fundamental concern for botanists, climatologists, and environmentalists.

Background

Autotrophs feed directly from their environment—they produce sustenance from the materials at hand. Most self-feeding organisms are plants such as grass, bushes, and trees; colorful and exotic sea plants, such as kelp and all varieties of seaweed; and a relatively small classification of bacteria that grows in difficult, even hostile environments, such as deep underwater, around the base of a volcano, in the middle of the desert, or in the forbidding cold of polar regions. Bacterial autotrophs typically cannot rely on sunlight for their food source due to their extreme habitats—instead, they convert readily available chemicals, such as methane or sulfur, to produce their energy in a process known as chemosynthesis.

The most familiar autotrophs, however, rely on the sun to produce nutrients through photosynthesis, which is the chemical process through which plants convert sunlight to energy. The plants take in direct sunlight and, in a reaction with the carbon dioxide in the air and water, produce glucose, a basic elemental sugar that plants use to create and sustain cell life. Glucose in turn is converted into cellulose, which provides plant life with its distinctive shape and structure and provides the plants themselves with a controlled and directed system of growth. As long as the basic elements remain readily available, plant life flourishes and, in turn, maintains the health and vitality of its larger ecosystem.

The food chain is a complex ranking of living things organized around the basic question of what eats what. There are three classifications of heterotrophs: herbivores (species that eat only plants and grains); carnivores (species that eat meat); and omnivores (species capable of eating both, a category that includes humans). Carnivores and omnivores feed mainly on herbivorous species; in this way almost all life ultimately depends on grasses, trees, bushes, and plants. Should something interrupt the availability of autotrophic food species, the impact will be felt throughout the ecosystem. For instance, a long-term drought from climate change or loss of lands through unchecked development can affect the health of the autotrophic support system for an ecosystem, and that ecosystem in turn will be affected, as other species higher in the food chain will suffer dramatic consequences such as malnutrition and ultimately starvation.

Even more important is the fact that the process of photosynthesis produces oxygen as a waste byproduct that plants themselves cannot use. Autotrophs are the only source for the planet’s supply of oxygen—which most living things rely on. If the autotrophs are jeopardized, then the rest of the planet’s ecosystem will also be in jeopardy.

Impact

The food chain is more than a classroom schematic for nature’s eating habits. It represents the interrelatedness and codependency of different species. Because grass, trees, and other plants seem so much an element of the immediate environment and because development of the environment seems so essential and so routine for an ever-expanding human population, few environmental activist groups target autotrophs in their much-publicized and well-intentioned green campaigns to save the planet. Save for global crusades to stop the destruction of rainforest ecosystems, efforts to save endangered animal species routinely receive far more attention and far more funding than plant protection programs. But climatologists find that nearly 10 percent of available grasslands, shrub lands, rangelands, and prairies are lost every year due to climate conditions such as drought and to urban development, and that in turn the species that rely on grasslands for nutrition have declined steeply. Given that humans rely on grains themselves as well as on animals that eat plants and grains, any disruption of grain production has a dramatic effect on the availability of food for humans as well.

That sort of linked reliance, climatologists as well as environmental botanists agree, promotes concern over long-term autotroph sustainability; that is, the survivability and health of the widest possible variety of autotrophs. Because autotrophs are the only species classification able to convert inorganic materials into food, they represent essentially the most important life process conducted within the environment.

Bibliography

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