All living organisms that inhabit the planet may be divided into two distinct groups based on their feeding habits; autotrophs and heterotrophs. Autotrophs are those organisms that use inorganic molecules to manufacture the organic material they need to survive; these organisms include plants, algae and some bacteria. Heterotrophs, on the other part, must obtain their energy (organic compounds) by feeding on autotrophs and other heterotrophs. Autotrophs are at the base of the food chains in all ecosystems on earth, whereas, heterotrophs rely on autotrophs directly and other heterotrophs, indirectly, to obtain their supply of energetic organic compounds.
Sources of energy
All living organisms on Earth need energy in order to live. Some organisms obtain the energy they need from the Sun. plants, algae and some bacteria, such as cyanobacteria, use CO2, water and sunlight to produce the organic materials they need for their subsistence. They’re called autotrophs because they produce their own food. Other organisms depend on autotrophs for their subsistence; they feed on them to obtain the organic substances they need. The synthesis of these organic substances during digestion produces the sources of energy in the form of carbohydrates, proteins and fats needed by the organism. These organisms are called heterotrophs, and they not only consume autotrophs, but other heterotrophs, as well.
Autotrophs
An autotroph is an organism that produces complex organic molecules, such as proteins, carbohydrates and fats, from simple inorganic compounds. Plants and algae are autotrophic organisms that produce organic compounds from the use of CO2, water and sunlight through the process of photosynthesis. These organisms use the light from the Sun as a source of energy to manufacture the organic compounds they need. Autotrophs are at the base of food chains in most land and marine ecosystems of the world. An autotroph can also produce organic compounds through chemical reactions (chemosynthesis). These types of organisms are known as chemoautotrophs. Chemoautotrophs synthesize organic substances from the oxidation of inorganic chemicals, rather than from using photosynthesis.
Heterotrophs
These organisms must obtain all their energy needs from other organisms. Heterotrophs feed on autotrophs, such as plants and algae, to obtain their supply of energy for their internal metabolic processes. Heterotrophs may be divided into herbivores, which feed on plants; carnivores, which feed on meat; omnivores, which obtain their organic compounds from plants and meat; and saprobics (fungi), which absorb their nutrients from non-living organisms. Predation is carried out by animals that eat other animals. Other animals, including bacteria obtain their energy by forming associations, including mutualism, parasitism and commensalism, with other organisms.
Most ecosystems of the world depend on autotrophs as primary producers in the food chain. Autotrophs take energy from sunlight and use it to generate rich energetic molecules to drive their internal processes. Plants, which are autotrophs, are at the base of all food chains. The energy produced by plants is transferred along the food chain when an organism eats another. The first consumer in the food chain is called primary consumer (herbivore); the secondary consumer, includes meat eaters (carnivores); and a tertiary consumer, includes omnivores (plant and meat eaters). Saprobes are organisms, such as fungi, that eat the decaying matter of other organisms.
While autotrophs synthesize complex organic molecules from simple inorganic compounds by the use of sunlight as a source of energy in a process known as photosynthesis, heterotrophs obtain the needed energy to produce complex organic molecules by feeding on autotrophs and other heterotrophs and breaking down the ingested organic compounds to manufacture other organic compounds needed for metabolism. The overall balance among autotrophs and heterotrophs within habitats are essential in the Earth’s ecosystems. According to etap.org, the flow of energy through living organisms (autotrophs and heterotrophs) begins with the energy from the sun and photosynthesis, then, this energy travels through the food chain (primary producers, primary consumers, secondary consumers, decomposers, etc.), in small quantities.
