Trophic Levels

In order to survive, organisms need energy. Without energy our bodies would not be able to function and death would be the ultimate result. Up to what we have known, most of the earth’s energy originates from the sun. This energy is divided and distributed among organisms and possesses a perfect function in each ecosystem to maintain the correct balance they require to prevail.

Different organisms carry a unique characteristic that enables them to acquire energy. There are organisms that directly use the sun’s energy to survive and also create other forms of energy, like carbohydrates for other organisms to utilize.  These organisms are denominated autotrophs or primary producers. The most commonly known primary producers are plants. Through photosynthesis, plants get energy and also create new for other organisms to consume. Organisms that consume autotrophs are heterotrophs or primarysecondary, and tertiary consumers. Heterotrophs include all sorts of herbivores, detrivores, and carnivores.

Autotrophs, herbivores, detrivores, and carnivores all consume quantities of energy within an ecosystem leaving less and less energy to consume within each level of the food chain. About 10% of energy is consumed within the levels that belong to primary producers, primary consumers, secondary, and tertiary consumers. These levels of energy consumption are known as trophic levels. The population of a species within each trophic level will determine the population of the next.

Imagine a perfectly balanced community with the trophic levels of plants, crickets, mice, snakes, and hawks. As mentioned, plants absorb the energy form the sun and likewise provide food for the crickets. When the crickets consume the plants, a percentage of the energy the plants provided will be lost within the crickets. To make things simple, let’s suppose the plants contained 100% of energy and now that the crickets have consumed a certain amount of the population of the plants, the crickets have 90% of the energy. This means that the crickets made the community lose 10% of the energy by eating some plants. Then, mice come and eat a number of the crickets consuming another 10% of the energy to leave the mice with 80% of the energy. The trophic levels left are snakes and hawks. These two can compete against each other to consume mice. However, the hawks have an advantage in their ability to also eat snakes.

If the population of snakes and hawks is considerably large, the one of snakes would have to be a bit greater than the one of hawks, because the snakes are potential food for the hawks. Notwithstanding, if the population of snakes is big, the one of mice has to be even vaster to feed both snakes and hawks. In this way, the population of crickets must be larger than the one of snakes, hawks, and mice combined in order to deliver the correct amount of energy for hawks, snakes, mice, and the crickets themselves need to not face extinction. Lastly, the population of plants would be the largest of them all, for they are the base of energy production to sustain a community like this one.

Pretending that a group of hawks immigrated to this community and made the population of hawks larger than the one of snakes, what do you think would happen to the community? I believe there are two possible outcomes, an optimist one and a pessimist one.

The pessimist one says that the hawks would eventually end up wiping out the snakes and the mice. This would lead to an ever growing population of crickets that would wipe out all the plants. In the end, the hawks and the crickets would both die of starvation. I think, though, that this is not a good manner of reasoning.

On the other hand, the optimist one says that hawks distribute the eating of snakes and mice about equally. There are hawks that prefer snakes than mice on the menu and vice versa. The mice population is still larger than the one of hawks, so they have no chance of running out and the density of the snake population is not condensed but dispersed. Therefore, being dispersed, snakes would be harder to find, making the hawks that prefer snakes to migrate to another place, leaving the community to continue to be balanced in the distribution of energy. Perhaps the population of hawks would be larger than before, but it would be good enough to conserve the energy consumption in a way that both the autotroph and heterotroph populations in this community do not die out.

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