In this article, the first in a series aimed at explaining the desert food chain to young people, we invite you to explore with us the pathway that energy, beginning with sunlight, follows as it flows through communities of plants and animals that make up food chains.
In principal, the food chains of our Southwestern deserts function just like the food chains of forests, grassy plains, swamplands or any other biologically distinctive region.
“Food chain,” as you may know, is the term biological scientists use to describe the sequence of living organisms through which energy passes as it fuels the life of a community of plants and animals. A food chain always begins with the plants, called “producers.” It always ends with the animals, called “consumers.”
Energy
Energy – the capacity for causing something to happen – is used by plants to grow and reproduce. It is used by animals to grow, reproduce and move. It is used by you to grow, run, swim or study.
You can think of energy as existing in two basic states. One is “potential” energy, or energy that is stored, like a savings account, available for spending. Potential energy is stored, for example, in a battery, an apple or an automobile gasoline. The second state is “kinetic” energy, or energy that is being spent to cause something to happen, like growth, reproduction or movement.
You can also think of energy as existing in various forms. For instance, you use chemical energy when you employ a battery to operate your camera, cell phone or electronic game. You use mechanical energy when you peddle your bike. You use electrical energy when you turn on your desk lamp. You use heat energy when you toast your bagel. Your body uses solar energy, or sunlight, to make Vitamin D, a nutrient essential for good health.
Energy and the Food Chain
Energy – essential for the growth of all organisms, the processes of life and the actions of the animals – enters the food chain through the plants, in the form of light from the sun.
Almost magically, it seems, the solar energy is combined, by the plants, with water and carbon dioxide to create “glucose,” a form of sugar used in reproduction and growth. The process, performed by all plants from the smallest to the largest, is called “photosynthesis,” a word that means “gathering of light.” Plants, the producers, are the first link in the food chain.
Energy begins to flow through the food chain when plant tissue is consumed by animals, for instance, insects such as weevils, reptiles such as turtles, birds such as pigeons, or mammals such as rabbits and deer. Animals that eat only plants are called “herbivores.” They are, obviously, the second link in the food chain.
Energy moves another link through the food chain when herbivores’ flesh is consumed by animals such as spiders, snakes, goshawks or shrews. Animals that eat only other animals’ flesh are called “carnivores.” They are the third link in the food chain.
Energy moves still another link with carnivores that eat other carnivores. These include, for instance, spider wasps, which may hunt tarantulas; snakes, which may eat other snakes; eagles, which may eat goshawks; and gray foxes, which may eat shrews. These carnivores are a fourth link in the food chain.
Energy moves in more diverse ways with animals that eat both plants and other animals. These include, for example, earwigs, which eat flowers and flies; collard lizards, which eat various fruits and insects; Gila Woodpeckers, which eat fruits and insects; and coyotes, which eat fruits and small animals. These animals, called “omnivores,” can be a second, third or fourth link in the food chain!
Energy moves in yet another direction with animals that feed on dead and decaying organisms. These animals, called “scavengers,” include a variety of species, ranging from earthworms, which feed on dead and decaying plant tissue, to Turkey Vultures, which eat dead and decaying animal carcasses.
Energy moves through the final link in the food chain with microscopic animals called “decomposers,” which feed on any remaining dead plant and animal tissue and animal waste. With time, these tiny organisms – fungi and bacteria – break down decaying organic matter, converting it into carbon dioxide and water—making them available for plants to use in the process of photosynthesis, making it possible for the cycle of energy to move through a living community all over again.
As you might imagine, energy follows very complex and constantly changing routes through the food chains because communities of plants and animals may consist of tens of thousands of species that change constantly with the seasons and the years. Indeed, you can visualize the process as an interlocking web of food chains.
Our Fragile Deserts
You may think that our Southwestern deserts, with their heat, spiny plants, venomous animals and rocky soils seem hostile and indestructible, but in fact, they rank among the most fragile of all the environments on earth. They produce only a small fraction of the total plant and animal tissue produced by a dense rainy warm forest of comparable size. They support perhaps tens of thousands of species of plants and animals, including the microscopic-sized species. That compares with the hundreds of thousands or perhaps millions of species supported by the dense forest. In a hard world with limited resources, the plants and animals of the desert often find it difficult to rebuild their communities after a major change.
Desert Food Chain Video.
