STEM Sims Logo

Trophic Tower

Trophic Tower Thumbnail
NASA estimates that there are currently about 400,000,000,000 trees on Earth. Only around 25,000 polar bears now inhabit Earth. Did you ever wonder why the earth has so many plants and many fewer animals? The answer has to do with energy conversions. And believe it or not, you can use a simple electrical circuit to model these transfers of energy in a typical ecosystem. Are you ready to discover the “shocking truth” about biological energy conversions? Let’s get started.

Trophic Tower Brochure

Trophic Tower Brochure

What does the phrase "trophic levels” mean?

The phrase "trophic levels" means food levels. The term trophic comes from a Greek term and is defined as food or feeding. The trophic level of an organism is its feeding position in a food chain. A food chain is a sequence of food and energy transfers from one organism feeding upon another. The three classifications of the food chain are producers, consumers, and decomposers. Producers are organisms that use the nutrients from the environment as an energy source to produce their own food. Producers, also known as autotrophs, are typically plants or algae which use the sun as an energy source to create nutrients during photosynthesis. Animals are consumers, also known as heterotrophs. Consumers cannot produce their own food and therefore must eat other organisms to get energy. There are three different types of consumers: herbivores, carnivores, and omnivores. Herbivores are animals that only eat primary producers like plants, such as deer. Carnivores are animals that eat other animals, such as tigers. Omnivores are animals that eat both plants and animals, like humans or bears. Decomposers such as bacteria and fungi like mushrooms feed on dead matter and waste. Decomposers convert their food into energy and nutrients for the environment, which feed the producers needed to start the food chain again.

What are the different trophic levels?

There are five different trophic levels. At level one there are primary producers, which are usually plants and algae that use photosynthesis to make their own food from the environment. At level two, the primary consumers are herbivores that consume these primary producers from level one. At level three, the secondary consumers are the carnivore animals that eat the herbivores at level two. At level four, the tertiary consumers are carnivores that eat other carnivores from level three. And finally, at level five, apex predators are at the top of the food chain because they have no predators. Level 1: Plants are primary producers creating food by photosynthesis. Level 2: Insects like grasshoppers are the primary consumers and eat the plants. Level 3: A toad, the secondary consumer, eats the grasshoppers. Level 4: A snake, the tertiary consumer, eats the toad. Level 5: A hawk, the apex predator, then eats the snake. After the hawk dies, the decomposers, like bacteria, will turn the dead matter into nutrients, which the primary producers will use to make food.

What does the term "biomass” mean?

Biomass is the total mass of organisms in a given area at a given time. Biomass is measured by weight or dry weight depending on what needs to be measured. For example, for measuring tuna, the weight would be if the tuna were weighed straight from the water. The dry weight would be a fraction of the normal weight, as they wouldn't count the water weight.

Can energy be lost?

Energy can never be lost. According to the law of conservation of energy, energy cannot be created nor destroyed. The energy is just converted into other forms of energy. When an organism eats, only the stored energy gets transferred to the consumer. Much of the energy is used to maintain the organism's life processes and some energy is converted into heat. When moving up to the next trophic level, a lot of energy is "lost" in the fact that the stored energy from the producer gets used up to maintain the life of the consumer. By the secondary consumer, there is only 10% of the energy from the original plant producer.

What are resistors in an electrical circuit?

Resistors are components of electrical circuits that resist the flow of current. The purpose of resistors is to create and maintain a safe current. Electricity passes between the two terminals of a resistor and the voltage of the current drops between the flow from one terminal to the other.

How does energy move through an electrical circuit?

In order for energy to move through an electrical circuit, there must be a power supply, which gives energy to the electric current (a flow of electrons). A common electrical source is a battery, which has a positive and negative terminal. The wire, which is a conductive material, allows electrons to pass through it and it connects the negative terminal to the positive terminal. There also needs to be a force that pushes the electrons along the circuit. This electromotive force (EMF), also known as voltage, is needed for movement. With a power supply, electrons move from the negative terminal through the conductor to a machine or resistor and then back to the positive terminal.

What does the phrase "energy dissipation” mean?

In resistors, energy dissipation is the conversion of potential energy into heat. When an electron moves through a resistor, it loses potential energy. This potential energy gets transferred into heat and energy is dissipated.

What is a model?

A model is a diagram that helps humans understand real word systems. Humans try to represent these complex systems with visualizations and illustrations to better grasp the concepts. An example of this would be a model of a circuit pictured below. This diagram helps students visualize a circuit and how it works.
Supplemental Background Figure

Image from

You need to log in to access this simulation.