Usually when people think of aquatic animals, they think of fish, but there’s so much more than just fish living in your closest river or lake! Read this lesson to learn who eats who in a freshwater food chain.
What Is a Food Chain?
A food chain is a linear progression of energy (food) as it flows from one organism to another along a single path in an ecosystem. Food chains are great at understanding the general idea about who eats who in a system, but in reality, this flow of energy is more of a food web. Food webs show both direct and indirect ways that energy flows throughout a system. To understand, let’s take a closer look at how a freshwater ecosystem might look.Freshwater ecosystems are made up of aquatic organisms in a body of freshwater like a river, stream, or lake.
Most people immediately think of fish, but there is a more diverse set of organisms living in these systems.
Freshwater Food Chain
If we simplify who’s eating who, we get a direct pathway. At the starting point, we have organisms that make energy from the sun, like plants. These form the base of the food chain and are called primary producers because they produce their own food from sunlight through photosynthesis.
If we move along the chain, we have herbivores, which are animals that eat only plants. In the food chain, we would call them primary consumers. Unlike plants, they cannot make their own food so they have to eat other things to survive.Next, we have carnivores which are animals that eat other animals. In the food chain, we call them secondary consumers.
Finally, there are tertiary consumers, which are additional carnivores that eat other carnivores. Many sport fish species are tertiary consumers. Technically, the food chain can continue when humans catch and remove fish from a system, but this goes slightly outside of the bounds of our aquatic system. Just be aware that it happens.It seems pretty simple, right?
If we look at this image, we see plants at the bottom (the primary producers). Insects eat the plants (our primary consumers), and larger insects eat these herbivores (our secondary consumers).
Frogs eat these secondary consumers (making them tertiary consumers), and then energy continues up the food chain with snakes and predatory birds.
Freshwater Food Web
Creating a food chain allows a tidy way for our minds to think about an ecosystem; however, in reality, there isn’t a single path of energy flow. Instead, if we look at all the connections in an ecosystem, we end up with a figure that looks more like a spider web, which is why we refer to it as a food web.We still have primary producers, primary consumers, secondary consumers, and tertiary consumers, just like in the food chain; but the relationships connecting these groups are a little different. We also break each group up into specialized groups based on how and what they eat.
It can be helpful to think of a food web like a pyramid instead of a chain. At the base of the pyramid, we have primary producers like plants. Plants can make their own energy, so there is often a lot of plant matter in a freshwater ecosystem.
As we move up the pyramid, the collection of species filling that tier gradually decreases. In other words, there are more species that eat plants than those that eat other animals.If we break down the different types of animals in each tier of the pyramid, we start to get more specific. In freshwater systems, there are species that play different roles in keeping the system functioning properly.
For example, there are animals, like crayfish, called detritivores that eat living organic matter. There are organisms, like bacteria and fungi, that are decomposers: they feed on non-living organic matter and are a necessary step to cycle energy. We also have parasites, like leeches, that feed on an animal, harming it in the process.
Finally, we have omnivores, which are animals that eat both plants and animals. So, you see, it’s not a clear single food chain; we have a multitude of connections, showing how interconnected each ecosystem is!
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