The Food Chain

A food chain is a one way sequence of energy transformations in a food web. The length of a food chain is determined by the amount of species involved starting from the producers and ending with the last consumer. The energy that is passed along a food chain is reduced within each successive level. Food chains may vary in length from three and above levels. Producers in a food chain are usually plants and algae. Producers use the energy from the Sun and transform it into organic compounds. Consumers are organisms that obtain the organic compounds needed for metabolism from primary producers.

The food chain

A food chain starts from primary producers and continues linearly with successive consumers. Primary consumers are usually the producers of energy in the form of food and they form the base of the food chains in a given ecosystem. The energy is passed along the consumers until it reaches the last consumers in a food chain which are usually the species that are not eaten by any other consumer. Food webs are complex relations of feeding habits among different animal species, while a food chain is a linear nourishing pathway in which one species in a level consumes the next lower level. In a food web, species can consume two or more species with no linear or level arrangement.

Energy pyramid

A food chain provides a measure of the amount of energy passed along a number of consumers. In a food pyramid, the different levels represent the groups of organisms representing the food chain, starting from the bottom which is where the primary producers (plants and algae) are. The producers provide the energy from inorganic sources to the community of organisms. Primary consumers, usually animals (herbivores), eat the producers. Secondary consumers (carnivores) eat the primary consumers. Tertiary consumers (carnivores) eat the secondary consumers. Within each level in a food chain, significant quantities of energy produced by the primary producers is consumed.

How is energy consumed through cellular respiration?

Chemical energy stored in the form of food decreases as it is consumed by the organisms in each level in a food chain. During cellular respiration, glucose is broken down into carbon dioxide, which is exhaled as a gas. During this reaction, hydrogen combines with oxygen to produce water. The energy released is stored in a molecule called ATP (adenosine triphosphate), which supplies the energy for all cellular reactions. All living organisms, including photosynthetic organisms, burn glucose as a source of energy. While primary producers use photosynthesis to convert and store energy, consumers release it during cellular respiration.

Food as a source of energy

Food is the main source of energy along the food chain. In each level of the food chain, some of the energy that is passed along, is lost during the body’s metabolic processes. The loss of energy increases as the energy travels to the next trophic level. The consumers at the very top of the food chain end up with less amounts of energy available than those at the base of the food chain. It has been estimated that an average of 90% of energy distributed in each step of the food chain is lost, and the remaining is passed along to the next trophic level.

All food chains in a given ecosystem start with the primary producers, typically algae and plants. Plants and algae use sunlight as a source of energy to convert and store chemical energy. This energy is distributed along trophic levels, usually consisting of three to five levels. The energy is transferred within these trophic levels as one organism eats another; however, in each level some of the energy is lost as heat. According to, toxic materials, including DDT and Mercury, among others, may accumulate in food, causing damage to organisms in the food chain, especially the predators at the top.