This has implications for humans as we strive to keep a growing human population adequately nourished. These ideas also introduce the origin of organic matter that later can become fossil fuels. The original source of energy in fossil fuels is sunlight, which fueled photosynthesis. Oil and natural gas come from photosynthetic plankton, which have been preserved in sediments on the ocean floor, heated, and chemically altered into hydrocarbons.
Coal comes from plants that have been buried in sediment, compacted, and preserved. These ideas are further explored in Energy Principle 4. Learn more about where oil comes from.
While many students can readily relate to the idea of the terrestrial food web, the marine food web may be less familiar to them. Students may be surprised to learn that about half the Earth's primary productivity of organic material comes from the oceans.
Provenance: Image from Microsoft image galleries. Compared to Energy Principles 1 and 2 , this principle is more concrete and easier to visualize. We all have direct experiences with different types of foods. Many of these concepts, such as how sunlight drives photosynthesis and food webs, are commonly taught in middle school and high school curricula.
Educators can take these opportunities to tie in an energy theme with these topics. A quantitative approach can be used to examine the energy embodied in different types of foods. Here are some examples of activities that do this. How Much Energy is on my Plate? The Lifestyle Project challenges students to dramatically lower their energy use, and adopting a vegetarian diet is one of the paths that students may elect to take.
For example, there is a deposit of fat on the heart and it was only relatively recently that it was realized that this acts as a temporary storage of buffer for energy. If one thinks of the blood system flowing around a heart, the glucose levels in it can fluctuate depending on a number of factors, such as whether one has recently digested a meal or engaged in strenuous activity.
As with most machines, steady inputs cause less strain on the system than large fluctuations and the aforementioned cardiac fat assists in smoothing out during those lean periods and allows the heart to continue operating without additional strain.
Adenosine triphosphate or ATP is one of the key molecular energy carriers in the biological world. The term chemiosmosis refers to the inter-conversion of chemical energy energy in the form of chemical bonds and energy in the from of a transmembrane electrochemical gradient.
Human agricultural practices, air pollution, acid rain, global deforestation, overfishing, oil spills, and illegal dumping on land and into the ocean all have impacts on ecosystems. Equilibrium is a dynamic state of an ecosystem in which, despite changes in species numbers and occurrence, biodiversity remains somewhat constant. In ecology, two parameters are used to measure changes in ecosystems: resistance and resilience.
The ability of an ecosystem to remain at equilibrium in spite of disturbances is called resistance. The speed at which an ecosystem recovers equilibrium after being disturbed is called resilience. Ecosystem resistance and resilience are especially important when considering human impact. The nature of an ecosystem may change to such a degree that it can lose its resilience entirely.
This process can lead to the complete destruction or irreversible altering of the ecosystem. A food chain is a linear sequence of organisms through which nutrients and energy pass as one organism eats another; the levels in the food chain are producers, primary consumers, higher-level consumers, and finally decomposers. These levels are used to describe ecosystem structure and dynamics.
There is a single path through a food chain. Each organism in a food chain occupies a specific trophic level energy level , its position in the food chain or food web.
In many ecosystems, the base, or foundation, of the food chain consists of photosynthetic organisms plants or phytoplankton , which are called producers.
The organisms that consume the producers are herbivores: the primary consumers. Secondary consumers are usually carnivores that eat the primary consumers.
Tertiary consumers are carnivores that eat other carnivores. Higher-level consumers feed on the next lower trophic levels, and so on, up to the organisms at the top of the food chain: the apex consumers.
In the Lake Ontario food chain, shown in [Figure 3] , the Chinook salmon is the apex consumer at the top of this food chain. One major factor that limits the number of steps in a food chain is energy. Energy is lost at each trophic level and between trophic levels as heat and in the transfer to decomposers [Figure 4]. Thus, after a limited number of trophic energy transfers, the amount of energy remaining in the food chain may not be great enough to support viable populations at yet a higher trophic level.
There is a one problem when using food chains to describe most ecosystems. Even when all organisms are grouped into appropriate trophic levels, some of these organisms can feed on more than one trophic level; likewise, some of these organisms can also be fed on from multiple trophic levels.
In addition, species feed on and are eaten by more than one species. In other words, the linear model of ecosystems, the food chain, is a hypothetical, overly simplistic representation of ecosystem structure. A holistic model—which includes all the interactions between different species and their complex interconnected relationships with each other and with the environment—is a more accurate and descriptive model for ecosystems. A food web is a concept that accounts for the multiple trophic feeding interactions between each species and the many species it may feed on, or that feed on it.
In a food web, the several trophic connections between each species and the other species that interact with it may cross multiple trophic levels. Investigate the trophic levels of a coral reef food web. Demonstrate how energy is transferred and transformed within an ecosystem using this infographic.
Join our community of educators and receive the latest information on National Geographic's resources for you and your students. Skip to content. Image Giant African Land Snail Primary consumers, like the Giant African land snail Achatina fulica , eat primary producers, like the plants the snail eats, taken energy from them.
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Related Resources. Energy Flow Through an Ecosystem. View Collection. Coral Reef Food Web. View Article. Energy Flow in an Ecosystem.
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