Learning how is energy lost between trophic levels can help you understand how the whole food web works.
When moving up the food chain, only about 10% of the energy is transferred to the next trophic level. It means the remaining 90% is wasted.
Right, so you know how much energy is lost between trophic levels, but the real question is, “how is it lost?”
The energy lost between trophic levels is wasted in the form of heat, but there are some other ways as well, leading to a loss of energy.
Understanding the Concept of Trophic Levels
In the context of ecological pyramids, food webs, and food chains, the “trophic level” describes a specific location within one of these structures.
Animals living there all have a similar feeding mode. And these levels can be divided into Primary producers, which are the foundation of an ecological pyramid.
They are usually followed by various tiers of consumers (primary, secondary, tertiary, etc.) and then by predators (apex).
Based on their preferred method of nutrition, organisms can be roughly classified into two broad categories.
Autotrophs can create organic matter (food) from inorganic sources. On the other hand, heterotrophs cannot do so and must rely on the consumption of other species for sustenance.
The Loss of Energy Between Trophic Levels
At each stage, or trophic level of a food chain or food web a significant amount of the original energy taken in is lost.
This is why food chains rarely support more than six trophic levels.
Even in an ideal ecosystem supporting a community of organisms that seem to thrive and flourish, it is likely to support three and just occasionally, four trophic levels.
Typically, the trophic levels are represented as a producer to primary consumer to secondary consumer to the tertiary consumer with the producer converting sunlight.
Lost Energy in the Ecosystem
In an ecosystem, the producer is usually a green plant of some kind that has to be available as significant biomass in the area.
It needs to be capable of processing enough sunlight as energy. And it does that through photosynthesis to make it worth eating as an energy source by a consumer on the next trophic level.
When it is, an entire community through the trophic level is able to survive and reproduce within the ecosystem.
Fact: To depict energy flow across ecosystems, food chains may also be portrayed as energy pyramids, with different trophic levels represented by each tier of the pyramid.
The Loss of Energy through Trophic Levels
However, the amount of available energy decreases as it is passed through each trophic level.
Each organism at each trophic level takes the energy it needs to use in its own biological processes and systems. But when it happens, a significant amount is no longer available to be passed on.
Measuring the Loss of Energy between Trophic Levels
Practically speaking, the exact amounts of energy lost at each level is difficult to measure.
The study of ecosystems and interactions between the life forms that live in them often involves hours of intensive fieldwork in less-than-ideal circumstances.
The Law of Thermodynamics
The truth is that there is always some variation in the amount of energy lost depending on such things as the size and habits of the living organisms in it.
However, the fact that there is always a loss is firmly agreed on.
This loss is understood as The Second Law of Thermodynamics. This law states that whenever energy is converted from one form to another, there is a tendency toward disorder and loss in the system.
It is also agreed that the loss can be a significant one.
Net Production Efficiency
NPE or net production efficiency refers to the amount of energy made available to the organisms in the next trophic level.
It provides ecologists with a way to quantify how efficiently the organisms of a specific trophic level incorporate the energy they have gained into their own biomass.
An Important Consideration
How efficiently energy is transferred from the producer to the consumer has worldwide implications for how food production is managed.
Like humans, cattle and other livestock have low NPEs. They are inefficient at transferring energy.
Fact: It is significantly more costly to produce energy content in the form of meat than it is to make energy from crops, such as corn or soybean.
How Much Energy is Lost between Trophic Levels?
It is widely believed that at each level as little as 10 percent of energy is passed on to benefit the next level, the consumer’s consumer.
For example, in a grassland ecosystem, about 10,000 kilocalories (kcal) of energy is provided by the sun held in the plant life. But, only 1,000 kcal will be passed on to benefit its primary consumers.
Only 10 kcal will make it to the tertiary level which is too little to be of any value.
Once ingested by a primary consumer, the energy provided by the producer becomes a finite resource.
It is severely depleted each time it is transferred from one consumer to another moving up through the trophic levels.
The trophic level transfer efficiency or TLTE, is the measure used to describe how much energy is believed to be lost.
How Is Energy Lost Between Trophic Levels?
You already have an idea about how much energy is likely to be wasted between trophic levels. But, it is still important to learn how it is wasted.
Most energy, usually around ninety percent, is never available to the next trophic level. Instead, much is lost forever as heat.
Humans and other warm-blooded organisms, collectively known as endotherms, produce heat as a waste product.
It can be noticed when a room full of people becomes too hot for comfort or when herd animals, such as sheep and horses stand together to stay warm.
Where the Energy is Lost
By far, most of this heat is produced as a waste by-product.
It happens due to the various metabolic processes involved in keeping the consumer, primary, secondary or tertiary, alive and fully functioning.
A huge amount of heat is produced and lost as ingested food particles are chemically pulled apart and broken down into forms the consumer’s body can utilize.
It is this process of metabolism that converts the food we eat into energy.
There are two metabolic pathways.
- The catabolic pathway
- The anabolic pathway
The catabolic pathway breaks down complex compounds to make energy available for cells. Protein and glucose are part of this group.
The anabolic pathway builds complex compounds using simple chemical compounds. This pathway uses the proteins it builds to create muscle.
There are several other biochemical processes with reactions that transform energy this way. But any molecule that is synthesized or utilized in any metabolic process is a form of energy.
Fact: Enzymes are chemical catalysts that oversee and regulate metabolic pathways, and bring chemicals together and speed up the resulting reactions.
Energy Lost in Other Ways
It is true that the most common way energy is lost between trophic levels is through heat, but it may happen due to other reasons as well. For instance:
Under Consumption of the Organism
Some plants have evolved to be inedible with tough skins on their fruit or thorns. Some are simply out of reach of the primary consumer, either too high up or buried underground.
Inability of Carnivores
A carnivore that fails to break a thigh bone because of its smaller size cannot access the bone marrow inside.
Therefore, it cannot take full advantage of the energy it could get from its prey.
Not all of what is eaten is actually digested. Particularly, the cellulose of tougher grasses but also seeds. Instead, this food passes through the gut and is egested as feces.
Other than these, there are some additional ways energy is consumed and wasted.
- Energy is taken for muscle movement, body growth and repair.
- Energy is used in the exchange of oxygen and CO2 during the respiration process.
- Energy is used by the digestive system to process and remove waste and in the production of urea.
Fact: Energy loss is higher in mammals than in reptiles, because mammals need to use more energy to internally regulate their own temperatures.
How is energy lost between trophic levels? It is a common question, and a confusing one too.
Though it is hard to measure, at least 90% of energy is wasted during the transfer from one trophic level to another.
And most of this energy is lost in the form of heat. But, it is worth mentioning that it can be wasted in many other ways too.