What Moves Through the Community From One Trophic Level to Another as Organisms Feed on One Another?

Chapter 20: Ecosystems and the Biosphere

Free energy Menstruum through Ecosystems

Learning Objectives

By the end of this section, you lot will be able to:

Depict the basic types of ecosystems on World
Differentiate betwixt nutrient chains and food webs and recognize the importance of each
Describe how organisms acquire free energy in a food spider web and in associated nutrient chains
Explicate how the efficiency of energy transfers between trophic levels furnishings ecosystem

An ecosystem is a community of living organisms and their abiotic (non-living) environment. Ecosystems tin be modest, such as the tide pools plant near the rocky shores of many oceans, or large, such as those institute in the tropical rainforest of the Amazon in Brazil ([Effigy i]).

Left photo shows a rocky tide pool with seaweed and snails. Right photo shows the Amazon rain forest.

There are three wide categories of ecosystems based on their general surroundings: freshwater, marine, and terrestrial. Within these three categories are individual ecosystem types based on the environmental habitat and organisms present.

Ecology of Ecosystems

Life in an ecosystem often involves competition for limited resource, which occurs both within a single species and betwixt different species. Organisms compete for food, water, sunlight, space, and mineral nutrients. These resources provide the energy for metabolic processes and the matter to make upward organisms' physical structures. Other disquisitional factors influencing community dynamics are the components of its physical environment: a habitat's climate (seasons, sunlight, and rainfall), peak, and geology. These tin can all exist important ecology variables that make up one's mind which organisms can exist within a item area.

Freshwater ecosystems are the least mutual, occurring on only ane.8 percent of Earth'south surface. These systems comprise lakes, rivers, streams, and springs; they are quite diverse, and support a variety of animals, plants, fungi, protists and prokaryotes.

Marine ecosystems are the nearly mutual, comprising 75 per centum of Globe's surface and consisting of three basic types: shallow ocean, deep ocean water, and deep body of water bottom. Shallow ocean ecosystems include extremely biodiverse coral reef ecosystems, notwithstanding the deep sea water is known for big numbers of plankton and krill (small crustaceans) that support it. These ii environments are especially important to aerobic respirators worldwide, as the phytoplankton perform 40 percent of all photosynthesis on Globe. Although non equally diverse equally the other two, deep ocean lesser ecosystems incorporate a wide variety of marine organisms. Such ecosystems exist even at depths where light is unable to penetrate through the water.

Terrestrial ecosystems, also known for their diversity, are grouped into big categories called biomes. A biome is a large-calibration customs of organisms, primarily divers on land by the ascendant establish types that exist in geographic regions of the planet with similar climatic weather condition. Examples of biomes include tropical rainforests, savannas, deserts, grasslands, temperate forests, and tundras. Grouping these ecosystems into only a few biome categories obscures the bang-up diversity of the individual ecosystems within them. For instance, the saguaro cacti (Carnegiea gigantean) and other plant life in the Sonoran Desert, in the United States, are relatively diverse compared with the desolate rocky desert of Boa Vista, an island off the coast of Western Africa ([Figure 2]).

Photo (a) shows saguaro cacti that look like telephone poles with arms extended from them. Photo (b) shows a barren plain of red soil littered with rocks.

Ecosystems and Disturbance

Ecosystems are complex with many interacting parts. They are routinely exposed to various disturbances: changes in the environment that affect their compositions, such as yearly variations in rainfall and temperature. Many disturbances are a issue of natural processes. For example, when lightning causes a wood fire and destroys part of a forest ecosystem, the ground is eventually populated with grasses, followed by bushes and shrubs, and later mature trees: thus, the forest is restored to its old state. This process is so universal that ecologists have given it a name—succession. The impact of ecology disturbances caused by homo activities is at present as significant as the changes wrought past natural processes. Homo agricultural practices, air pollution, acid rain, global deforestation, overfishing, oil spills, and illegal dumping on state and into the body of water all accept impacts on ecosystems.

Equilibrium is a dynamic country of an ecosystem in which, despite changes in species numbers and occurrence, biodiversity remains somewhat abiding. In ecology, ii parameters are used to mensurate changes in ecosystems: resistance and resilience. The power of an ecosystem to remain at equilibrium in spite of disturbances is chosen resistance. The speed at which an ecosystem recovers equilibrium after being disturbed is chosen resilience. Ecosystem resistance and resilience are peculiarly important when considering homo impact. The nature of an ecosystem may alter to such a caste that it tin can lose its resilience entirely. This process tin pb to the complete destruction or irreversible altering of the ecosystem.

Food Bondage and Nutrient Webs

A food chain is a linear sequence of organisms through which nutrients and energy pass as ane organism eats another; the levels in the food chain are producers, principal consumers, higher-level consumers, and finally decomposers. These levels are used to draw 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 nutrient chain or food spider web.

In many ecosystems, the base of operations, or foundation, of the nutrient concatenation consists of photosynthetic organisms (plants or phytoplankton), which are called producers. The organisms that eat the producers are herbivores: the main consumers. Secondary consumers are usually carnivores that consume the primary consumers. 3rd consumers are carnivores that eat other carnivores. Higher-level consumers feed on the side by side lower trophic levels, and and so on, up to the organisms at the summit 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.

In this illustration, the bottom trophic level is green algae, which is the primary producer. The primary consumers are mollusks, or snails. The secondary consumers are small fish called slimy sculpin. The tertiary and apex consumer is Chinook salmon.

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 free energy remaining in the food chain may non be great enough to support viable populations at yet a college trophic level.

Graph shows energy content in different trophic levels. The energy content of producers is over 20,000 kilocalories per meter squared per year. The energy content of primary consumers is much smaller, about 4,000 kcal/m 2/year. The energy content of secondary consumers is 100 kcal/m2/year, and the energy content of tertiary consumers is only 1 kcal/m2/year

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 tin feed on more than one trophic level; also, some of these organisms can besides exist fed on from multiple trophic levels. In addition, species feed on and are eaten by more than than one species. In other words, the linear model of ecosystems, the nutrient concatenation, is a hypothetical, overly simplistic representation of ecosystem structure. A holistic model—which includes all the interactions between unlike 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 betwixt each species and the many species information technology may feed on, or that feed on it. In a food spider web, the several trophic connections betwixt each species and the other species that interact with it may cross multiple trophic levels. The matter and energy movements of virtually all ecosystems are more accurately described by food webs ([Figure 5]).

The bottom level of the illustration shows decomposers, which include fungi, mold, earthworms, and bacteria in the soil. The next level above decomposers shows the producers: plants. The level above the producers shows the primary consumers that eat the producers. Some examples are squirrels, mice, seed-eating birds, and beetles. Primary consumers are in turn eaten by secondary consumers, such as robins, centipedes, spiders, and toads. The tertiary consumers such as foxes, owls, and snakes eat secondary and primary consumers. All of the consumers and producers eventually become nourishment for the decomposers.

Head to this online interactive simulator to investigate food web function. In the Interactive Labs box, under Nutrient Spider web, click Step 1. Read the instructions get-go, and then click Step 2 for additional instructions. When y'all are ready to create a simulation, in the upper-correct corner of the Interactive Labs box, click Open SIMULATOR.

2 general types of food webs are ofttimes shown interacting within a single ecosystem. A grazing food web has plants or other photosynthetic organisms at its base, followed by herbivores and diverse carnivores. A detrital food spider web consists of a base of organisms that feed on decaying organic thing (dead organisms), including decomposers (which suspension downward dead and decaying organisms) and detritivores (which consume organic detritus). These organisms are commonly bacteria, fungi, and invertebrate animals that recycle organic material back into the biotic function of the ecosystem as they themselves are consumed by other organisms. Equally ecosystems require a method to recycle textile from expressionless organisms, grazing food webs have an associated detrital nutrient web. For case, in a meadow ecosystem, plants may support a grazing nutrient web of different organisms, primary and other levels of consumers, while at the same fourth dimension supporting a detrital nutrient web of bacteria and fungi feeding off dead plants and animals. Simultaneously, a detrital food web can contribute energy to a grazing food web, as when a robin eats an earthworm.

How Organisms Acquire Energy in a Food Spider web

All living things require energy in one form or another. Energy is used by most complex metabolic pathways (ordinarily in the form of ATP), specially those responsible for building large molecules from smaller compounds. Living organisms would non be able to assemble macromolecules (proteins, lipids, nucleic acids, and complex carbohydrates) from their monomers without a constant energy input.

Food-web diagrams illustrate how energy flows directionally through ecosystems. They can also bespeak how efficiently organisms acquire energy, use information technology, and how much remains for employ by other organisms of the food spider web. Energy is caused by living things in two ways: autotrophs harness low-cal or chemical energy and heterotrophs acquire energy through the consumption and digestion of other living or previously living organisms.

Photosynthetic and chemosynthetic organisms are autotrophs, which are organisms capable of synthesizing their ain food (more than specifically, capable of using inorganic carbon as a carbon source). Photosynthetic autotrophs (photoautotrophs) use sunlight as an energy source, and chemosynthetic autotrophs (chemoautotrophs) use inorganic molecules as an free energy source. Autotrophs are critical for nearly ecosystems: they are the producer trophic level. Without these organisms, free energy would non be available to other living organisms, and life itself would non be possible.

Photoautotrophs, such as plants, algae, and photosynthetic leaner, are the free energy source for a majority of the world'southward ecosystems. These ecosystems are often described by grazing and detrital food webs. Photoautotrophs harness the Dominicus'due south solar free energy past converting information technology to chemical energy in the form of ATP (and NADP). The energy stored in ATP is used to synthesize circuitous organic molecules, such as glucose. The rate at which photosynthetic producers comprise energy from the Sun is called gross chief productivity. However, not all of the energy incorporated by producers is bachelor to the other organisms in the food web considering producers must also grow and reproduce, which consumes energy. Net primary productivity is the energy that remains in the producers after bookkeeping for these organisms' respiration and heat loss. The internet productivity is then available to the primary consumers at the side by side trophic level.

Chemoautotrophs are primarily bacteria and archaea that are found in rare ecosystems where sunlight is not available, such as those associated with dark caves or hydrothermal vents at the bottom of the bounding main ([Figure 6 ]). Many chemoautotrophs in hydrothermal vents utilize hydrogen sulfide (H₂S), which is released from the vents every bit a source of chemic free energy; this allows them to synthesize complex organic molecules, such equally glucose, for their own energy and, in plough, supplies energy to the residuum of the ecosystem.

Photo shows shrimp, lobster, and crabs crawling on a rocky ocean floor littered with mussels.

Consequences of Food Webs: Biological Magnification

One of the about important consequences of ecosystem dynamics in terms of human impact is biomagnification. Biomagnification is the increasing concentration of persistent, toxic substances in organisms at each successive trophic level. These are substances that are fatty soluble, not water soluble, and are stored in the fat reserves of each organism. Many substances take been shown to biomagnify, including classical studies with the pesticide dichlorodiphenyltrichloroethane (Dichloro-diphenyl-trichloroethane), which were described in the 1960s bestseller, Silent Leap by Rachel Carson. Ddt was a unremarkably used pesticide before its dangers to noon consumers, such every bit the bald eagle, became known. In aquatic ecosystems, organisms from each trophic level consumed many organisms in the lower level, which caused Dichloro-diphenyl-trichloroethane to increase in birds (apex consumers) that ate fish. Thus, the birds accumulated sufficient amounts of Dichloro-diphenyl-trichloroethane to cause fragility in their eggshells. This event increased egg breakage during nesting and was shown to have devastating effects on these bird populations. The apply of DDT was banned in the United states in the 1970s.

Other substances that biomagnify are polychlorinated biphenyls (PCB), which were used equally coolant liquids in the Us until their use was banned in 1979, and heavy metals, such as mercury, atomic number 82, and cadmium. These substances are best studied in aquatic ecosystems, where predatory fish species accumulate very high concentrations of toxic substances that are at quite depression concentrations in the environment and in producers. Every bit illustrated in a study performed past the NOAA in the Saginaw Bay of Lake Huron of the North American Great Lakes ([Figure 7]), PCB concentrations increased from the producers of the ecosystem (phytoplankton) through the different trophic levels of fish species. The apex consumer, the walleye, has more than iv times the amount of PCBs compared to phytoplankton. As well, based on results from other studies, birds that eat these fish may have PCB levels at least one lodge of magnitude higher than those found in the lake fish.

The illustration is a graph that plots total PCBs in micrograms per gram of dry weight versus nitrogen-15 enrichment, shows that PCBs become increasingly concentrated at higher trophic levels. The slope of the graph becomes increasingly steep as consumer levels increase, from phytoplankton to walleye.

Other concerns accept been raised by the biomagnification of heavy metals, such equally mercury and cadmium, in certain types of seafood. The United States Environmental Protection Agency recommends that pregnant women and young children should not swallow any swordfish, shark, king mackerel, or tilefish considering of their high mercury content. These individuals are advised to eat fish depression in mercury: salmon, shrimp, pollock, and catfish. Biomagnification is a good example of how ecosystem dynamics tin touch on our everyday lives, fifty-fifty influencing the nutrient nosotros eat.

Section Summary

Ecosystems exist underground, on land, at sea, and in the air. Organisms in an ecosystem acquire energy in a variety of ways, which is transferred between trophic levels equally the free energy flows from the base of operations to the superlative of the food web, with energy being lost at each transfer. At that place is energy lost at each trophic level, and then the lengths of food bondage are limited because there is a point where not enough energy remains to back up a population of consumers. Fatty soluble compounds biomagnify upward a food chain causing impairment to acme consumers. even when environmental concentrations of a toxin are low.

Multiple Choice

Decomposers are associated with which class of food web?

grazing
detrital
inverted
aquatic

[reveal-answer q="276629″]Show Reply[/reveal-answer]
[subconscious-answer a="276629″]2[/subconscious-answer]

The producer in an sea grazing food web is usually a ________.

establish
animal
fungi
plankton

[reveal-answer q="330783″]Show Answer[/reveal-respond]
[hidden-answer a="330783″]iv[/hidden-answer]

Which term describes the procedure whereby toxic substances increase along trophic levels of an ecosystem?

biomassification
biomagnification
bioentropy
heterotrophy

[reveal-reply q="100762″]Show Answer[/reveal-reply]
[hidden-answer a="100762″]2[/hidden-reply]

Free Response

Compare grazing and detrital food webs. Why would they both exist present in the aforementioned ecosystem?

Grazing food webs have a producer at their base of operations, which is either a institute for terrestrial ecosystems or a phytoplankton for aquatic ecosystems. The producers pass their energy to the various trophic levels of consumers. At the base of detrital nutrient webs are the decomposers, which laissez passer their energy to a variety of other consumers. Detrital food webs are important for the health of many grazing food webs because they eliminate dead and decomposable organic cloth, thus clearing space for new organisms and removing potential causes of illness.

Glossary

autotroph: an organism capable of synthesizing its own food molecules from smaller inorganic molecules

apex consumer: an organism at the meridian of the food chain

biomagnification: an increasing concentration of persistent, toxic substances in organisms at each trophic level, from the producers to the noon consumers

biome: a large-scale customs of organisms, primarily defined on land by the dominant plant types that exist in geographic regions of the planet with similar climatic weather condition

chemoautotroph: an organism capable of synthesizing its own food using free energy from inorganic molecules

detrital food web: a type of food web that is supported by dead or decaying organisms rather than by living autotrophs; these are oftentimes associated with grazing food webs within the same ecosystem

ecosystem: a community of living organisms and their interactions with their abiotic environment

equilibrium: the steady state of a organization in which the relationships betwixt elements of the organization do not modify

food chain: a linear sequence of trophic (feeding) relationships of producers, primary consumers, and higher level consumers

food web: a web of trophic (feeding) relationships among producers, main consumers, and higher level consumers in an ecosystem

grazing food spider web: a type of food web in which the producers are either plants on land or phytoplankton in the water; often associated with a detrital food web within the same ecosystem

gross primary productivity: the rate at which photosynthetic producers incorporate energy from the Sun

cyberspace primary productivity: the free energy that remains in the producers after accounting for the organisms' respiration and heat loss

photoautotroph: an organism that uses sunlight as an energy source to synthesize its own food molecules

principal consumer: the trophic level that obtains its energy from the producers of an ecosystem

producer: the trophic level that obtains its free energy from sunlight, inorganic chemicals, or dead or decaying organic cloth

resilience (ecological): the speed at which an ecosystem recovers equilibrium afterwards existence disturbed

resistance (ecological): the power of an ecosystem to remain at equilibrium in spite of disturbances

secondary consumer: a trophic level in an ecosystem, commonly a carnivore that eats a primary consumer

tertiary consumer: a trophic level in an ecosystem, usually carnivores that eat other carnivores

trophic level: the position of a species or group of species in a food chain or a food web

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Source: https://opentextbc.ca/conceptsofbiologyopenstax/chapter/energy-flow-through-ecosystems/

What Moves Through the Community From One Trophic Level to Another as Organisms Feed on One Another?

Free energy Menstruum through Ecosystems

Learning Objectives

Ecology of Ecosystems

Ecosystems and Disturbance

Food Bondage and Nutrient Webs

How Organisms Acquire Energy in a Food Spider web

Consequences of Food Webs: Biological Magnification

Section Summary

Multiple Choice

Free Response

Glossary

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