What are the first, second, and third trophic levels?

Question

Please list the names of the first, second, and third trophic levels.

Answer 1

In an ecosystem, organisms are designated to various ‘feeding levels’ or ‘trophic levels’ by ecologists based on their different sources of food or nutrients.

The first trophic level is comprised of producers also known as autotrophs (Auto- means self and troph originating from the Greek word ‘trophe’, meaning “nourishment, food.”). This implies they are self-feeders or capable of producing their food by using the sun’s energy directly. On land plants or algae are the major producers as they can trap 1% of the solar energy that falls on their leaves (containing chlorophyll pigments) convert it into chemical energy and store it as energy-rich organic compounds like glucose by the process of ‘photosynthesis’. This energy derived from glucose molecules becomes fuel for the existence of entire organisms in other/higher trophic levels in an ecosystem. While most earth’s organisms obtain their energy directly from sunlight there are certain specialized bacteria ( found in hydrothermal/geothermal vents) that use hydrogen sulfide(H₂S) as their main source of energy to produce carbohydrates by the process of ‘Chemosynthesis’, thus functioning as producers in their ecosystems. In aquatic ecosystems, phytoplankton plays the role of producers. Therefore, plants form the base of the trophic levels in an ecosystem.

All the other organisms including humans come under the group ‘consumers’ or ‘heterotrophs’ or ‘other-feeders’ as they lack chlorophyll pigments, are not capable of utilizing solar energy directly, and hence cannot synthesize their food through photosynthesis, need to depend either directly or indirectly on producers to obtain food and derive energy.

Consumers can be categorized as:

Primary consumers or herbivores (plant-eaters): They mainly occupy second trophic levels. They include all animals(e.g. deer, rabbits, grasshoppers, etc.) that directly consume plants ( on land) and zooplankton ( ( that feeds on phytoplankton in water).

Secondary consumers or carnivores (meat-eaters): These consumers occupying the third trophic levels depend entirely on the flesh of herbivores to complete their food requirements. Animals like spiders, birds, frogs, etc., and some zooplankton feeding on small fishes fall in this level.

Tertiary consumers: These are also carnivorous animals that feed on secondary consumers, constituting the next trophic level that includes animals like cheetahs, alligators, lions, tigers, and wolves. Other than carnivores, omnivores (e.g. many mammals including humans, and bears) also occupy this level. Omnivores are animals or organisms that can derive their food from both plant and animal sources.

Decomposers: are consumers ( certain bacteria or fungi) that are capable of releasing all the stored minerals or nutrients back into the soil/ environment by secreting certain enzymes onto the body of dead animals or plants that speed up their degrading process, so that the producers can reuse the nutrients and maintain the stability of the ecosystem. ‘Detritivores or detritus feeders’ are animals ( e.g. Vulture) that feed on the dead remains of other organisms.

Hence a trophic level is mainly comprised of producers, consumers, and decomposers.