Question and Answer - Trophic Levels

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a.) Choosing organisms from four different trophic levels of this four web as examples, explain how energy is obtained at each trophic level.

Since energy is a necessary part of how an organism survives, how it obtains it’s energy is crucial. When you look at an ecosystem, and all the organisms living within that ecosystem, you can link many of the species together by their dependence on each other. Scientists will look at these links to see how they depend on each other, or in other words, where their main source of energy and nutrition is. Once that step is determined, scientists will assign that group of species to a trophic level; to either the primary producers, primary consumers, secondary consumers, or the tertiary consumers.

The bottom of the chain and the trophic level that depends upon by all others is the primary producers. These primary producers consist of autotrophs, which are capable of deriving their food and energy source without consuming organisms or substances taken from other organisms. In the Arctic lake of Alaska, one of it’s primary producers consists of aquatic plants and algae. These aquatic and algae contain chlorophyll, which means that they can use light energy from the sun to synthesize glucose and other organic compounds, that they can use for cellular respiration and building material for growth. In other words, called photosynthesis. Photosynthesis requires light energy, but some autotrophs use chemosynthesis, which means they can convert nutrients to organic compounds without light in the presence.

While the trophic level of primary producers is of autotrophs, the next remaining levels all represent heterotrophs. Heterotrophs can only obtain their energy by consuming of other organisms. In the tropic level of the primary consumers, these herbivores depend on these primary producers and other plants for their food. An example of a primary consumer is the larvae of chironomids, or a type of aquatic insect.

The next trophic level is made up of secondary consumers. These secondary consumers are also heterotrophs, and these organisms are carnivores that obtain their energy from consuming other herbivores. An organism that belongs to this category is the sculpin, a small fish, that uses organisms

such as the larvae of the chironomids to obtain their energy necessary for survival.

The fourth and last trophic level that remains is the tertiary consumers.

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