Ecology/Energy in ecosystems - Wikibooks, open books for an open world
In ecology, energy flow, also called the calorific flow, refers to the flow of energy through a food chain, and is the focus of study in ecological energetics. In an ecosystem, ecologists seek to quantify the relative importance of different component species and feeding relationships. Food webs · Biomagnification · Ecological efficiency · Ecological pyramid · Energy flow · Food chain; Trophic level. Example webs. Energy transfer between trophic levels is inefficient. To illustrate the difference, let's consider primary productivity (the productivity of the primary producers Net primary productivity varies among ecosystems and depends on many factors.
Decomposers process large amounts of organic material and return nutrients to the ecosystem in inorganic form, which are then taken up again by primary producers.
Energy is not recycled during decomposition, but rather is released, mostly as heat this is what makes compost piles and fresh garden mulch warm. Figure 6 shows the flow of energy dark arrows and nutrients light arrows through ecosystems. Energy and nutrient transfer through ecosystems See larger image Source: An ecosystem's gross primary productivity GPP is the total amount of organic matter that it produces through photosynthesis.
Net primary productivity NPP describes the amount of energy that remains available for plant growth after subtracting the fraction that plants use for respiration. On land primary productivity thus is highest in warm, wet zones in the tropics where tropical forest biomes are located. In contrast, desert scrub ecosystems have the lowest productivity because their climates are extremely hot and dry Fig.
How are trophic levels related to the flow of energy through an ecosystem?
Terrestrial net primary productivity See larger image Source: In the oceans, light and nutrients are important controlling factors for productivity. As noted in Unit 3, "Oceans," light penetrates only into the uppermost level of the oceans, so photosynthesis occurs in surface and near-surface waters. Marine primary productivity is high near coastlines and other areas where upwelling brings nutrients to the surface, promoting plankton blooms.
Runoff from land is also a source of nutrients in estuaries and along the continental shelves. Among aquatic ecosystems, algal beds and coral reefs have the highest net primary production, while the lowest rates occur in the open due to a lack of nutrients in the illuminated surface layers Fig. Ocean net primary productivity, See larger image Source: How many trophic levels can an ecosystem support?
BBC Bitesize - GCSE Biology (Single Science) - Food chains - Revision 6
Photoautotrophs like plants use light energy to build sugars out of carbon dioxide. The energy is stored in the chemical bonds of the molecules, which are used as fuel and building material by the plant. The energy stored in organic molecules can be passed to other organisms in the ecosystem when those organisms eat plants or eat other organisms that have previously eaten plants. In this way, all the consumers, or heterotrophs "other-feeding" organisms of an ecosystem, including herbivores, carnivores, and decomposers, rely on the ecosystem's producers for energy.
Unit 4: Ecosystems // Section 3: Energy Flow Through Ecosystems
If the plants or other producers of an ecosystem were removed, there would be no way for energy to enter the food web, and the ecological community would collapse. That's because energy isn't recycled: Image based on similar image by J.Energy Transfer in Trophic Levels
Because producers support all the other organisms in an ecosystem, producer abundance, biomass dry weightand rate of energy capture are key in understanding how energy moves through an ecosystem and what types and numbers of other organisms it can sustain. Primary productivity In ecology, productivity is the rate at which energy is added to the bodies of organisms in the form of biomass. Since decomposers recycle nutrients, leaving them so they can be reused by primary producers, they are sometimes regarded as occupying their own trophic level.
Virtually all plants and phytoplankton are purely phototrophic and are at exactly level 1. Many worms are at around 2. For example, a traditional Eskimo living on a diet consisting primarily of seals would have a trophic level of nearly 5. In general, each trophic level relates to the one below it by absorbing some of the energy it consumes, and in this way can be regarded as resting on, or supported by, the next lower trophic level.
Food chains can be diagrammed to illustrate the amount of energy that moves from one feeding level to the next in a food chain.
This is called an energy pyramid. The energy transferred between levels can also be thought of as approximating to a transfer in biomassso energy pyramids can also be viewed as biomass pyramids, picturing the amount of biomass that results at higher levels from biomass consumed at lower levels.
However, when primary producers grow rapidly and are consumed rapidly, the biomass at any one moment may be low; for example, phytoplankton producer biomass can be low compared to the zooplankton consumer biomass in the same area of ocean. For this reason, food chains rarely extend for more than 5 or 6 levels.
It follows from this that the total energy originally present in the incident sunlight that is finally embodied in a tertiary consumer is about 0.
Food webs largely define ecosystems, and the trophic levels define the position of organisms within the webs. But these trophic levels are not always simple integers, because organisms often feed at more than one trophic level.