Biotic Components of an Ecosystem

Biotic components refer to the different kinds of organism that interact with the environment. There are many ways of grouping these organisms. One way is discussed in connection with the ecological niches in a biotic community: producers, consumers and decomposers.

Another way of grouping organisms is to distinguish between those that can make their own food (the autotrophs) and those that cannot (the heterotrophs). Those that manufacture food  are said to be autotrophic. The terms autotroph and autotrophic came from the Greek words auto (meaning self) and tropikos (meaning nursing or feeding); thus they mean self-nourishing or self-feeding. Autotrophs are the producers of biotic communities.

Most autotrophic organisms manufacture food by utilizing the energy from the sun. The process is known as photosynthesis. Plants, algae and some bacteria have the green pigment called chlorophyll that captures sunlight and thus permits them to perform photosynthesis.

Another group of bacteria has the ability to manufacture food using the energy stored in inorganic molecules. The process is known as chemosynthesis. Compared to photosynthetic autotrophs, chemosynthetic autotrophs have a much more limited distribution in the biosphere. However, they play a very important role in certain habitats such as the deep ocean floor around hydrothermal vents. In such a hot mineral-rich environment, chemosynthetic sulfur bacteria are the sole producers of entire communities of heat-tolerant organisms. The very productive communities thrive near the vents at temperatures of around 40^oC.

The terms heterotroph and heterotrophic came from the Greek words heteros (meaning other) and tropikos (nursing). Heterotrophs are the consumers and decomposers of biotic communities. They may be grouped into two, based on size: The large ones called macroconsumers (the prefix macro-literally means large), while the tiny ones are called microconsumers (micro – means small). Cow, dog and frog are examples of macroconsumers. Microbes such as the malarial parasite, paramecium and nonautotrophic bacteria are examples of microconsumers.

Heterotrophs may also be grouped into four, based on what they feed on: Those that feed on plants (such as carabaos and goats) are called plant-eaters, or herbivores. Those that feed on flesh or meat (such as dogs and cats) are called flesh-eaters, or carnivores. Those that feed on both plants and meat (such as chickens and humans) are called variety-eaters, or omnivores.

Those that feed on small pieces of leaves and other organic matter (collectively called detritus) are known as detritus-feeders, or detritivores. Detritivores are abundant on the forest floor, in soil and in bodies of water.

Still another group of heterotrophs consists of those that absorb dissolved organic materials, usually the product of decomposition. These are called saprotrophs; their mode of feeding is known as saprotrophic nutrition. The most abundant saprotrophs are the saprotrophic bacteria; other examples are mushrooms and other fungi.