Food Webs | How Energy Flows Through an Ecosystem | edZOOcating

Because of their superpower, plants are a very important part of their environment as they are commonly the foundation of food chains. A food chain represents how energy moves through an ecosystem. In other words, it shows who eats who to get the energy. Each organism in a food chain occupies a trophic level. A low trophic level means you are near the start of a food chain, like a plant or an animal that eats plants. A high trophic level means you are near the end of the food chain, like a large predator. The lowest trophic level is always occupied by plants, which we sometimes call autotrophs! 

Because autotrophs can produce their own energy from the sun, they are also known as primary producers on the food chain. Primary producers are eaten by herbivores (plant-eaters). Animals that directly eat plants are called primary consumers. A flower being eaten by a little mouse is a classic example of a primary consumer eating a primary producer. Then you have carnivores that feed on herbivores, like a snake eating the mouse. Even though they occupy the third trophic level, we call them secondary consumers. The even stronger predators that feed on the secondary consumers are called tertiary consumers. This would be like a hawk swooping down and eating that snake! While trophic levels do continue past tertiary consumers, these four trophic levels commonly make up food chains. 

While food chains give us a good idea of how energy moves throughout an ecosystem, it is not always accurate because there are a lot of complexities in the animal kingdom. Some animals are omnivores and play the role of both primary consumer and secondary consumer, like a bear that eats small animals and berries! Many animals also eat more than one type of food and have more than one type of predator. A snake may eat a mouse and a bird and may be preyed on by a hawk or a coyote! Sometimes we have to combine many different food chains to get a better understanding of how energy moves around, making a food web. 

Food webs are very helpful in showing us these different energy pathways through the living environment, but what happens to the non-living stuff? Dead plants or animals that end up on the ecosystem floor have their energy recycled back into the environment through the help of decomposers. Dead leaves that end up in the soil may be eaten by decomposers like worms or millipedes who then excrete waste filled with recycled nutrients back into the soil, which then helps new plants grow! 

So, with all of the complexities of food webs, what happens if one of the organisms is removed? Well, it depends. Some species play a very important role in their ecosystem and, without them, the food web and the ecosystem would likely collapse. We call these organisms keystone species. Wolves are an example of a keystone species. When we remove wolves from an ecosystem, there are not enough predators to keep the populations of deer and elk in check. As the herbivore population grows, they need more vegetation and can overgraze huge amounts of land! When we change the presences of wolves in an ecosystem, the whole ecosystem changes with it. 

Food webs allow us to better understand ecosystems and how they function. By understanding ecosystems better, we can learn what parts are important for the ecosystem to function properly and therefore, what the best way to protect them is.