There are hundreds of thousands of species of algae. Simply put, what they all have in common is that they are able to produce their food through a process known as photosynthesis. Photosynthesis refers to the ability of plants to extract energy from the sunlight to produce sugar. The sugar is converted into fuel that can be used to feed the plant. The process of photosynthesis applies to algae, allowing them to use accessory pigments and chlorophyll to perform the process.
Decomposers are organisms, also known as saprobes, that consume dead animals and plants.Decomposers, much like consumers and producers, play an important role in the food chain because they break down dead matter that is eventually absorbed by autotrophs and heterotrophs.
Producers are part of the cyclical food chain that occurs in nature. While producers make their own food, they in turn become food for another category that does not produce or scavenge food, known as consumers. For example, consumers such as fish feed off algae.
While most algae are autotrophs, meaning they can produce their own food through inorganic compounds, there are a minority of algae types that are heterotroph, which means they cannot make their own food. An example of a heterotropic plant is the Euglenophyta, a unicellular aguatic algae that sometimes has to ingest food that is already made. Algae, for example, extract microscopic nutrients from the water to feed on.