|
|
|
|
What Is a Food Web? A food web is a detailed interconnecting diagram that shows the overall food relationships between organisms in a particular environment. The simplest explanation is that food webs are "who eats whom" diagrams showing the complex feeding relationships for a specific ecosystem. The study of food webs is important, as such webs can show how energy flows through an ecosystem. It also helps us understand how toxins and pollutants become concentrated within a particular ecosystem. Examples include mercury bioaccumulation in the Florida Everglades and mercury accumulation in the San Francisco Bay. Food webs can also help us study and explain how species diversity is related to how they fit within the overall food dynamic. They may also reveal critical information about the relationships between invasive species and those native to a particular ecosystem. Key Takeaways: What Is a Food Web? Think of a food web as a "who eats whom" diagram showing an ecosystem's complex feeding relationships.
Knowing the interconnectedness of organisms in energy transfer within an ecosystem is vital to understanding food webs and how they apply to real-world science. An increase in toxic substances, like man-made persistent organic pollutants (POPs), can profoundly impact ecosystem species. By analyzing food webs, scientists can study and predict how substances move through the ecosystem to help prevent the bioaccumulation and biomagnification of harmful substances. The concept of a food web, previously known as a food cycle, is typically credited to Charles Elton, who first introduced it in his book Animal Ecology, published in 1927. He is considered one of the founders of modern ecology and his book is a seminal work. In this book, he also introduced other important ecological concepts like niche and succession. In a food web, organisms are arranged according to their trophic level. An organism's trophic level refers to how it fits within the food web and is based on how it feeds. There are two main designations: autotrophs and heterotrophs.
Autotrophs make their food, while heterotrophs do not. Within this broad designation are five main trophic levels: primary producers, primary consumers, secondary consumers, tertiary consumers, and apex predators. A food web shows how the different trophic levels within various food chains interconnect and how energy flows through them within an ecosystem. Primary producers make their food via photosynthesis, which uses the sun's energy to make food by converting its light energy into chemical energy. Examples of primary producers include plants and algae. These organisms are also known as autotrophs. Primary consumers are animals that eat the primary producers. They are named as such because they are the first organisms to eat the primary producers who make their own food. Primary consumers are also known as herbivores. Examples of animals in this designation are rabbits, beavers, elephants, and moose. Secondary consumers consist of organisms that eat primary consumers. Since secondary consumers are animals that eat the animals that eat the plants, they are called carnivorous or omnivorous.
Carnivores eat animals, while omnivores consume both other animals and plants. Bears are an example of a secondary consumer. Similar to secondary consumers, tertiary consumers can be carnivorous or omnivorous. The difference is that secondary consumers eat other carnivores. An example is an eagle. Lastly, the final level is composed of apex predators. Apex predators are at the top because they do not have natural predators. Lions are an example. Additionally, organisms known as decomposers consume dead plants and animals and break them down. Fungi are examples of decomposers. Other organisms known as detritivores consume dead organic material. A vulture is an example of a detrivore. Energy flows through the different trophic levels. It begins with the sun's energy, which autotrophs use to produce food. This energy is transferred up the levels as the different organisms are consumed by members of the levels above them. Approximately 10% of the energy transferred from one trophic level to the next is converted to biomass-the overall mass of an organism or the mass of all the organisms that exist in a given trophic level.
Since organisms expend energy to move around and go about their daily activities, only a part of the energy consumed is stored as biomass. While a food web contains all constituent food chains in an ecosystem, food chains are a different construct. A food web can be composed of multiple food chains, some very short and others much longer. Food chains follow the flow of energy as it moves through the chain. The starting point is the energy from the sun, and this energy is traced as it moves through the food chain. This movement is typically linear, from one organism to another. For example, a short food chain may consist of plants that use the sun's energy to produce their food through photosynthesis and the herbivore that consumes these plants. This herbivore may be eaten by two different carnivores, which are a part of this food chain. When these carnivores are killed or die, the decomposers in the chain break down the carnivores, returning nutrients to the soil that can be used by plants.
|
|
