schematic representation of food chain

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High school biology

Course: high school biology   >   unit 9.

• Flow of energy and matter through ecosystems

Food chains & food webs

• Example identifying roles in a food web
• Energy flow and primary productivity
• Trophic levels review
• Trophic levels

Key points:

• Producers , or autotrophs, make their own organic molecules. Consumers , or heterotrophs, get organic molecules by eating other organisms.
• A food chain is a linear sequence of organisms through which nutrients and energy pass as one organism eats another.
• In a food chain, each organism occupies a different trophic level , defined by how many energy transfers separate it from the basic input of the chain.
• Food webs consist of many interconnected food chains and are more realistic representation of consumption relationships in ecosystems.
• Energy transfer between trophic levels is inefficient (with a typical efficiency around 10 % ‍   ). This inefficiency limits the length of food chains.

Introduction

Autotrophs vs. heterotrophs.

• Photoautotrophs , such as plants, use energy from sunlight to make organic compounds (sugars) out of carbon dioxide in photosynthesis . Other examples of photoautotrophs include algae and cyanobacteria.
• Chemoautotrophs use energy from chemicals to build organic compounds out of carbon dioxide (or similar molecules). This is called chemosynthesis . For instance, there are hydrogen sulfide-oxidizing chemoautotrophic bacteria found in undersea vent communities (where no light can reach).

Food chains

• At the base of the food chain lie the primary producers . The primary producers are autotrophs, and are most often photosynthetic organisms (such as plants, algae, or cyanobacteria).
• The organisms that eat the primary producers are called primary consumers . Primary consumers are usually herbivores (plant-eaters), though they may be algae or bacteria eaters.
• The organisms that eat the primary consumers are called secondary consumers . Secondary consumers are generally meat-eaters ( carnivores ).
• The organisms that eat the secondary consumers are called tertiary consumers . These are carnivore-eating carnivores, like eagles or big fish.
• Some food chains have additional levels, such as quaternary consumers (carnivores that eat tertiary consumers). Organisms at the very top of a food chain are called the apex consumers .

Decomposers

Grazing vs. detrital food webs, energy transfer efficiency limits food chain lengths.

• In each trophic level, a significant amount of energy is dissipated as heat, as organisms carry out cellular respiration and go about their daily lives.
• Some of the organic molecules an organism eats cannot be digested and leave the body as feces (poop) rather than being used.
• Not all of the individual organisms in a trophic level will get eaten by organisms in the next level up. Some instead die without being eaten.

Attribution

• " Ecology of ecosystems ," by Robert Bear, David Rintoul, Bruce Snyder, Martha Smith-Caldas, Christopher Herren, and Eva Horne, CC BY 4.0 . Download the original article for free at http://cnx.org/contents/[email protected] .
• " Energy flow through ecosystems ," by OpenStax College, Concepts of Biology, CC BY 4.0 . Download the original article for free at http://cnx.org/contents/[email protected] .
• " Energy flow through ecosystems ," by OpenStax College, Biology, CC BY 4.0 . Download the original article for free at http://cnx.org/contents/[email protected] .
• " Flow of energy ," by CK-12 Foundation, CC BY-NC 3.0 .

Works cited

• F. Stuart Chapin III, Pamela A. Matson, and Harold A. Mooney, "Trophic Dynamics," in Principles of Terrestrial Ecosystem Ecology (New York: Springer-Verlag, 2002), 250-251.
• Peter H. Raven, George B. Johnson, Kenneth A. Mason, Jonathan B. Losos, and Susan R. Singer, "The Flow of Energy in Ecosystems," in Biology , 10th ed., AP ed. (New York: McGraw-Hill, 2014), 1216.

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Food Web: Concept and Applications

Introduction

There are two types of food chains: the grazing food chain, beginning with autotrophs, and the detrital food chain, beginning with dead organic matter (Smith & Smith 2009). In a grazing food chain, energy and nutrients move from plants to the herbivores consuming them, and to the carnivores or omnivores preying upon the herbivores. In a detrital food chain, dead organic matter of plants and animals is broken down by decomposers, e.g., bacteria and fungi, and moves to detritivores and then carnivores.

Food web offers an important tool for investigating the ecological interactions that define energy flows and predator-prey relationship (Cain et al. 2008). Figure 1 shows a simplified food web in a desert ecosystem. In this food web, grasshoppers feed on plants; scorpions prey on grasshoppers; kit foxes prey on scorpions. While the food web showed here is a simple one, most feed webs are complex and involve many species with both strong and weak interactions among them (Pimm et al. 1991). For example, the predators of a scorpion in a desert ecosystem might be a golden eagle, an owl, a roadrunner, or a fox.

The idea to apply the food chains to ecology and to analyze its consequences was first proposed by Charles Elton (Krebs 2009). In 1927, he recognized that the length of these food chains was mostly limited to 4 or 5 links and the food chains were not isolated, but hooked together into food webs (which he called "food cycles"). The feeding interactions represented by the food web may have profound effects on species richness of community, and ecosystem productivity and stability (Ricklefs 2008).

Types of Food Webs

Applications of food webs, food webs are constructed to describe species interactions (direct relationships)..

The fundamental purpose of food webs is to describe feeding relationship among species in a community. Food webs can be constructed to describe the species interactions. All species in the food webs can be distinguished into basal species (autotrophs, such as plants), intermediate species (herbivores and intermediate level carnivores, such as grasshopper and scorpion) or top predators (high level carnivores such as fox) (Figure 1).

These feeding groups are referred as trophic levels. Basal species occupy the lowest trophic level as primary producer. They convert inorganic chemical and use solar energy to generate chemical energy. The second trophic level consists of herbivores. These are first consumers. The remaining trophic levels include carnivores that consume animals at trophic levels below them. The second consumers (trophic level 3) in the desert food web include birds and scorpions, and tertiary consumers making up the fourth trophic level include bird predators and foxes. Grouping all species into different functional groups or tropic levels helps us simplify and understand the relationships among these species.

Food webs can be used to illustrate indirect interactions among species.

Indirect interaction occurs when two species do not interact with each other directly, but influenced by a third species. Species can influence one another in many different ways. One example is the keystone predation are demonstrated by Robert Paine in an experiment conducted in the rocky intertidal zone (Cain et al. 2008; Smith & Smith 2009; Molles 2010). This study showed that predation can influence the competition among species in a food web. The intertidal zone is home to a variety of mussels, barnacles, limpets, and chitons (Paine 1969). All these invertebrate herbivores are preyed upon by the predator starfish Pisaster (Figure 3). Starfish was relatively uncommon in the intertidal zone, and considered less important in the community. When Paine manually removed the starfish from experimental plots while leaving other areas undisturbed as control plots, he found that the number of prey species in the experimental plots dropped from 15 at the beginning of the experiment to 8 (a loss of 7 species) two years after the starfish removal while the total of prey species remained the same in the control plots. He reasoned that in the absence of the predator starfish, several of the mussel and barnacle species (that were superior competitors) excluded the other species and reduced overall diversity in the community (Smith & Smith 2009). Predation by starfish reduced the abundance of mussel and opened up space for other species to colonize and persist. This type of indirect interaction is called keystone predation.

Food webs can be used to study bottom-up or top-down control of community structure.

Top-down control occurs when the population density of a consumer can control that of its resource, for example, predator populations can control the abundance of prey species (Power 1992). Under top-down control, the abundance or biomass of lower trophic levels depends on effects from consumers at higher trophic levels. A trophic cascade is a type of top-down interaction that describes the indirect effects of predators. In a trophic cascade, predators induce effects that cascade down the food chain and affect biomass of organisms at least two links away (Ricklefs 2008). Nelson Hairston, Frederick Smith and Larry Slobodkin first introduced the concept of top-down control with the frequently quoted "the world is green" proposition (Power 1992; Smith & Smith 2009). They proposed that the world is green because carnivores depress herbivores and keep herbivore populations in check. Otherwise, herbivores would consume most of the vegetation. Indeed, a bird exclusion study demonstrated that there were significantly more insects and leaf damage in plots without birds compared to the control (Marquis & Whelan 1994).

Food webs can be used to reveal different patterns of energy transfer in terrestrial and aquatic ecosystems.

As a diagram tool, food web has been approved to be effective in illustrating species interactions and testing research hypotheses. It will continue to be very helpful for us to understand the associations of species richness/diversity with food web complexity, ecosystem productivity, and stability.

References and Recommended Reading

Cain, M. L., Bowman, W. D. & Hacker, S. D. Ecology . Sunderland MA: Sinauer Associate Inc. 2008.

Cebrian, J. Patterns in the fate of production in plant communities. American Naturalist 154 , 449-468 (1999)

Cebrian, J. Role of first-order consumers in ecosystem carbon flow. Ecology Letters 7 , 232-240 (2004)

Elton, C. S. Animal Ecology . Chicago, MI: University of Chicago Press, 1927, Republished 2001.

Knight, T. M., et al. Trophic cascades across ecosystems. Nature 437 , 880-883 (2005)

Krebs, C. J. Ecology 6 th ed. San Francisco CA: Pearson Benjamin Cummings, 2009.

Marquis, R. J. & Whelan, C. Insectivorous birds increase growth of white oak through consumption of leaf-chewing insects. Ecology 75 , 2007-2017 (1994)

Molles, M. C. Jr. Ecology: Concepts and Applications 5 th ed. New York, NY: McGraw-Hill Higher Education, 2010.

Paine, R. T. The Pisaster-Tegula interaction: Prey parches, predator food preferences and intertide community structure. Ecology 60 , 950-961 (1969)

Paine, R. T. Food web complexity and species diversity. The American Naturalist 100 , 65-75 (1966)

Paine, R. T. Food webs: Linkage, interaction strength and community infrastructure. Journal of Animal Ecology 49 , 667-685 (1980)

Pimm, S. L., Lawton, J. H. & Cohen, J. E. Food web patterns and their consequences. Nature 350 , 669-674 (1991)

Power, M. E. Top-down and bottom-up forces in food webs: do plants have primacy? Ecology 73 , 733-746 (1992)

Schoender, T. W. Food webs from the small to the large. Ecology 70 , 1559-1589 (1989)

Shurin, J. B., Gruner, D. S. & Hillebrand, H. All wet dried up? Real differences between aquatic and terrestrial food webs. Proc. R. Soc. B 273 , 1-9 (2006) doi:10.1098/rspb.2005.3377

Smith, T. M. & Smith, R. L. Elements of Ecology 7 th ed. San Francisco CA: Pearson Benjamin Cummings, 2009.

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Module 26: Ecology and the Environment

Food chains and food webs, learning outcomes.

• Differentiate between food chains and food webs and recognize the importance of each

The term “food chain” is sometimes used metaphorically to describe human social situations. In this sense, food chains are thought of as a competition for survival, such as “who eats whom?” Someone eats and someone is eaten. Therefore, it is not surprising that in our competitive “dog-eat-dog” society, individuals who are considered successful are seen as being at the top of the food chain, consuming all others for their benefit, whereas the less successful are seen as being at the bottom.

Figure 1. These are the trophic levels of a food chain in Lake Ontario at the United States-Canada border. Energy and nutrients flow from photosynthetic green algae at the bottom to the top of the food chain: the Chinook salmon.

The scientific understanding of a food chain is more precise than in its everyday usage. In ecology, a food chain is a linear sequence of organisms through which nutrients and energy pass: primary producers, primary consumers, and higher-level consumers are used to describe ecosystem structure and dynamics. There is a single path through the chain. Each organism in a food chain occupies what is called a trophic level . Depending on their role as producers or consumers, species or groups of species can be assigned to various trophic levels.

In many ecosystems, the bottom of the food chain consists of photosynthetic organisms (plants and/or phytoplankton), which are called primary producers . The organisms that consume the primary 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 tropic 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 1, the Chinook salmon is the apex consumer at the top of this food chain.

One major factor that limits the length of food chains is energy. Energy is lost as heat between each trophic level due to the second law of thermodynamics. 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.

The loss of energy between trophic levels is illustrated by the pioneering studies of Howard T. Odum in the Silver Springs, Florida, ecosystem in the 1940s (Figure 2). The primary producers generated 20,819 kcal/m 2 /yr (kilocalories per square meter per year), the primary consumers generated 3368 kcal/m 2 /yr, the secondary consumers generated 383 kcal/m 2 /yr, and the tertiary consumers only generated 21 kcal/m 2 /yr. Thus, there is little energy remaining for another level of consumers in this ecosystem.

Figure 2. The relative energy in trophic levels in a Silver Springs, Florida, ecosystem is shown. Each trophic level has less energy available and supports fewer organisms at the next level.

There is a one problem when using food chains to accurately describe most ecosystems. Even when all organisms are grouped into appropriate trophic levels, some of these organisms can feed on species from more than one trophic level; likewise, some of these organisms can be eaten by species from multiple trophic levels. In other words, the linear model of ecosystems, the food chain, is not completely descriptive of ecosystem structure. A holistic model—which accounts for 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 graphic representation of a holistic, non-linear web of primary producers, primary consumers, and higher-level consumers used to describe ecosystem structure and dynamics (Figure 3).

Figure 3. This food web shows the interactions between organisms across trophic levels in the Lake Ontario ecosystem. Primary producers are outlined in green, primary consumers in orange, secondary consumers in blue, and tertiary (apex) consumers in purple. Arrows point from an organism that is consumed to the organism that consumes it. Notice how some lines point to more than one trophic level. For example, the opossum shrimp eats both primary producers and primary consumers. (credit: NOAA, GLERL)

A comparison of the two types of structural ecosystem models shows strength in both. Food chains are more flexible for analytical modeling, are easier to follow, and are easier to experiment with, whereas food web models more accurately represent ecosystem structure and dynamics, and data can be directly used as input for simulation modeling.

Two general types of food webs are often shown interacting within a single ecosystem. A grazing food web (such as the Lake Ontario food web in Figure 3) has plants or other photosynthetic organisms at its base, followed by herbivores and various carnivores. A detrital food web consists of a base of organisms that feed on decaying organic matter (dead organisms), called decomposers or detritivores. These organisms are usually bacteria or fungi that recycle organic material back into the biotic part of the ecosystem as they themselves are consumed by other organisms. As all ecosystems require a method to recycle material from dead organisms, most grazing food webs have an associated detrital food web. For example, in a meadow ecosystem, plants may support a grazing food web of different organisms, primary and other levels of consumers, while at the same time supporting a detrital food web of bacteria, fungi, and detrivorous invertebrates feeding off dead plants and animals.

Consequences of Food Webs: Biological Magnification

One of the most important environmental consequences of ecosystem dynamics is biomagnification. Biomagnification is the increasing concentration of persistent, toxic substances in organisms at each trophic level, from the primary producers to the apex consumers. Many substances have been shown to bioaccumulate, including classical studies with the pesticide d ichloro d iphenyl t richloroethane (DDT), which was published in the 1960s bestseller, Silent Spring , by Rachel Carson. DDT was a commonly used pesticide before its dangers became known. In some aquatic ecosystems, organisms from each trophic level consumed many organisms of the lower level, which caused DDT to increase in birds (apex consumers) that ate fish. Thus, the birds accumulated sufficient amounts of DDT to cause fragility in their eggshells. This effect increased egg breakage during nesting and was shown to have adverse effects on these bird populations. The use of DDT was banned in the United States in the 1970s.

Figure 4. This chart shows the PCB concentrations found at the various trophic levels in the Saginaw Bay ecosystem of Lake Huron. Numbers on the x -axis reflect enrichment with heavy isotopes of nitrogen (15N), which is a marker for increasing trophic level. Notice that the fish in the higher trophic levels accumulate more PCBs than those in lower trophic levels. (credit: Patricia Van Hoof, NOAA, GLERL)

Other substances that biomagnify are polychlorinated biphenyls (PCBs), which were used in coolant liquids in the United States until their use was banned in 1979, and heavy metals, such as mercury, lead, and cadmium. These substances were best studied in aquatic ecosystems, where fish species at different trophic levels accumulate toxic substances brought through the ecosystem by the primary producers. As illustrated in a study performed by the National Oceanic and Atmospheric Administration (NOAA) in the Saginaw Bay of Lake Huron (Figure 4), PCB concentrations increased from the ecosystem’s primary producers (phytoplankton) through the different trophic levels of fish species. The apex consumer (walleye) has more than four times the amount of PCBs compared to phytoplankton. Also, based on results from other studies, birds that eat these fish may have PCB levels at least one order of magnitude higher than those found in the lake fish.

Other concerns have been raised by the accumulation of heavy metals, such as mercury and cadmium, in certain types of seafood. The United States Environmental Protection Agency (EPA) recommends that pregnant women and young children should not consume any swordfish, shark, king mackerel, or tilefish because of their high mercury content. These individuals are advised to eat fish low in mercury: salmon, tilapia, shrimp, pollock, and catfish. Biomagnification is a good example of how ecosystem dynamics can affect our everyday lives, even influencing the food we eat.

• Biology 2e. Provided by : OpenStax. Located at : http://cnx.org/contents/[email protected] . License : CC BY: Attribution . License Terms : Access for free at https://openstax.org/books/biology-2e/pages/1-introduction

The food chain describes who eats whom in the wild.

Biology, Ecology

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The food chain describes who eats whom in the wild. Every living thing—from one-celled algae to giant blue whales ( Balaenoptera musculus )—needs food to survive . Each food chain is a possible pathway that energy and nutrients can follow through the ecosystem . For example, grass produces its own food from sunlight. A rabbit eats the grass. A fox eats the rabbit. When the fox dies, bacteria break down its body, returning it to the soil where it provides nutrients for plants like grass. Of course, many different animals eat grass, and rabbits can eat other plants besides grass. Foxes, in turn, can eat many types of animals and plants. Each of these living things can be a part of multiple food chains. All of the interconnected and overlapping food chains in an ecosystem make up a food web . Trophic Levels Organisms in food chains are grouped into categories called trophic levels. Roughly speaking, these levels are divided into producers (first trophic level), consumers (second, third, and fourth trophic levels), and decomposers . Producers, also known as autotrophs , make their own food. They make up the first level of every food chain. Autotrophs are usually plants or one-celled organisms. Nearly all autotrophs use a process called photosynthesis to create “food” (a nutrient called glucose ) from sunlight, carbon dioxide , and water. Plants are the most familiar type of autotroph, but there are many other kinds. Algae, whose larger forms are known as seaweed , are autotrophic. Phytoplankton , tiny organisms that live in the ocean, are also autotrophs. Some types of bacteria are autotrophs. For example, bacteria living in active volcanoes use sulfur compounds to produce their own food. This process is called chemosynthesis . The second trophic level consists of organisms that eat the producers. These are called primary consumers , or herbivores . Deer, turtles, and many types of birds are herbivores. Secondary consumers eat the herbivores. Tertiary consumers eat the secondary consumers. There may be more levels of consumers before a chain finally reaches its top predator . Top predators, also called apex predators , eat other consumers. Higher-level consumers (i.e., secondary, tertiary, and above) can be carnivores (animals that eat other animals) or omnivores (animals that eat both plants and animals). Omnivores, like people, consume many types of foods. People eat plants, such as vegetables and fruits. We also eat animals and animal products, such as meat, milk, and eggs. We eat fungi , such as mushrooms. We also eat algae, in edible seaweeds like nori (used to wrap sushi rolls) and sea lettuce (used in salads). Detritivores and decomposers are the final part of food chains. Detritivores are organisms that eat nonliving plant and animal remains. For example, scavengers such as vultures eat dead animals. Dung beetles eat animal feces . Decomposers like fungi and bacteria complete the food chain. They turn organic wastes, such as decaying plants, into inorganic materials, such as nutrient-rich soil. Decomposers complete the cycle of life, returning nutrients to the soil or oceans for use by autotrophs. This starts a whole new food chain.

Food Chains Different habitats and ecosystems provide many possible food chains that make up a food web.

In one marine food chain , single-celled organisms called phytoplankton provide food for tiny shrimp called krill . Krill provide the main food source for the blue whale , an animal on the third trophic level . In a grassland ecosystem , a grasshopper might eat grass, a producer . The grasshopper might get eaten by a rat, which in turn is consumed by a snake. Finally, a hawk—an apex predator —swoops down and snatches up the snake. In a pond, the autotroph might be algae . A mosquito larva eats the algae , and then perhaps a dragonfly larva eats the young mosquito. The dragonfly larva becomes food for a fish, which provides a tasty meal for a raccoon.

Carnivorous ... Plants? Most plants on Earth take energy from the sun and nutrients from the soil. A few plants, however, get their nutrients from animals. These carnivorous plants include pitcher plants, Venus flytraps ( Dionaea muscipula ), and bladderworts. These plants attract and trap prey, usually insects, and then break them down with digestive enzymes.

Links in the Chain Organisms consume nutrients from a variety of different sources in the food chain.

• Xylophages eat wood. Termites and bark beetles are xylophages.
• Coprophages eat animal feces. Dung beetles and flies are coprophages.
• Geophages eat earth, such as clay or soil. Parrots and cockatoos are geophages.
• Palynivores eat pollen. Honeybees and some butterflies are palynivores.
• Lepidophages are fish that eat the scales (but not the body) of other fish. Some piranha and some catfish are lepidophages.
• Mucophages eat mucus. Usually, these tiny organisms live in the gills of fish.

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Related Resources

• Food Chain and Food Web

Food chain is a linear sequence of organisms which starts from producer organisms and ends with decomposer species . Food web is a connection of multiple food chains. Food chain follows a single path whereas food web follows multiple paths. From the food chain, we get to know how organisms are connected with each other. Food chain and food web form an integral part of this ecosystem. Let us take a look at the food chain and a food web and the difference between them.

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In scientific terms, a food chain is a chronological pathway or an order that shows the flow of energy from one organism to the other. In a community which has producers, consumers , and decomposers, the energy flows in a specific pathway. Energy is not created or destroyed. But it flows from one level to the other, through different organisms.

A food chain shows a single pathway from the producers to the consumers and how the energy flows in this pathway. In the animal kingdom , food travels around different levels. To understand a food chain better, let us take a look at the terrestrial ecosystem.

Food chain in a Terrestrial Ecosystem

The sun is the source of energy, which is the initial energy source. This is used by the producers or plants to create their own food, through photosynthesis and grow. Next in this chain is another organism, which is the consumer that eats this food, taking up that energy.

The primary consumers are the organisms that consume the primary producers.  In a terrestrial ecosystem, it could be a herbivore like a cow or a goat or it could even be a man.  When a goat is consumed by man, he becomes the secondary consumer.

Learn more about Biogeochemical Cycle here in detail.

As the energy goes one level up, the food chain also moves up. Each level in the food chain is called a trophic level. The different trophic levels are Primary producers, primary consumers, secondary consumers, tertiary consumers and quaternary consumers.

Example of food chain

Grass (Producer) —–Goat (Primary Consumer) —– Man (Secondary consumer)

When dead organic matter becomes the starting of a food chain, then it is called the detritus food chain (DFC). The decomposers, which are the fungi and bacteria , feed on the organic matter to meet the energy requirements. The digestive enzymes secreted by the decomposers help in the breakdown of the organic matter into inorganic materials.

Download Ecosystem Cheat Sheet PDF

Browse more topics under ecosystem.

• Components of Ecosystem
• Ecological Pyramid and Ecological Succession
• Biogeochemical Cycle

Many interconnected food chains make up a food web. When you look at the larger picture, a food web shows a realistic representation of the energy flow through different organisms in an ecosystem.

Learn more about Components of Ecosystem here in detail.

Sometimes, a single organism gets eaten by many predators or it eats many other organisms. This is when a food chain doesn’t represent the energy flow in a proper manner because there are many trophic levels that interconnect. This is where a food web comes into place. It shows the interactions between different organisms in an ecosystem.

The following diagram shows the energy flow between various organisms through a food web.

Solved Questions For You

Q: Name the common detritivores in an ecosystem. Do they play a significant role? Support your answer.

Ans:   Earthworms, dung beetles, and sea cucumbers are some of the common detritivores in an ecosystem. They play a crucial role in the ecosystem, by decomposing the dead organic matter.

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• Biology Article
• Overview of Food Chain

An Overview of Food Chain

Table of Contents

• What is a food chain
• Types of food chain
• Frequently Asked Questions

Food Chain: Introduction

A food chain explains which organism eats another organism in the environment. The food chain is a linear sequence of organisms where nutrients and energy is transferred from one organism to the other. This occurs when one organism consumes another organism. It begins with the producer organism, follows the chain and ends with the decomposer organism. After understanding the food chain, we realise how one organism is dependent upon another organism for survival.

Now, let’s look at the other aspects of a food chain, to get a better understanding.

What is a Food Chain?

A food chain refers to the order of events in an ecosystem, where one living organism eats another organism, and later that organism is consumed by another larger organism. The flow of nutrients and energy from one organism to another at different trophic levels forms a food chain.

The food chain also explains the feeding pattern or relationship between living organisms. Trophic level refers to the sequential stages in a food chain, starting with producers at the bottom, followed by primary, secondary and tertiary consumers. Every level in a food chain is known as a trophic level.

The food chain consists of four major parts, namely:

• The Sun: The sun is the initial source of energy, which provides energy for everything on the planet.
• Producers: The producers in a food chain include all autotrophs such as phytoplankton, cyanobacteria, algae, and green plants. This is the first stage in a food chain. The producers make up the first level of a food chain. The producers utilise the energy from the sun to make food. Producers are also known as autotrophs as they make their own food. Producers are any plant or other organisms that produce their own nutrients through photosynthesis.
• Consumers: Consumers are all organisms that are dependent on plants or other organisms for food. This is the largest part of a food web, as it contains almost all living organisms. It includes herbivores which are animals that eat plants, carnivores which are animals that eat other animals, parasites that live on other organisms by harming them and lastly the scavengers, which are animals that eat dead animals’ carcasses.

Here, herbivores are known as primary consumers and carnivores are secondary consumers. The second trophic level includes organisms that eat producers. Therefore, primary consumers or herbivores are organisms in the second trophic level.

• Decomposers: Decomposers are organisms that get energy from dead or waste organic material. This is the last stage in a food chain. Decomposers are an integral part of a food chain, as they convert organic waste materials into inorganic materials, which enriches the soil or land with nutrients.

Decomposers complete a life cycle. They help in recycling the nutrients as they provide nutrients to soil or oceans, that can be utilised by autotrophs or producers. Thus, starting a whole new food chain.

Several interconnected food chains form a food web. A food web is similar to a food chain but the food web is comparatively larger than a food chain. Occasionally, a single organism is consumed by many predators or it consumes several other organisms. Due to this, many trophic levels get interconnected. The food chain fails to showcase the flow of energy in the right way. But, the food web is able to show the proper representation of energy flow, as it displays the interactions between different organisms.

When there are more cross-interactions between different food chains, the food web gets more complex. This complexity in a food web leads to a more sustainable ecosystem.

Types of Food Chain

There are two types of food chains, namely the detritus food chain and the grazing food chain. Let’s look at them more closely:

• Detritus food chain: The detritus food chain includes different species of organisms and plants like algae, bacteria, fungi, protozoa, mites, insects, worms and so on. The detritus food chain begins with dead organic material. The food energy passes into decomposers and detritivores, which are further eaten by smaller organisms like carnivores. Carnivores, like maggots, become a meal for bigger carnivores like frogs, snakes and so on. Primary consumers like fungi, bacteria, protozoans, and so on are detritivores which feed on detritus.
• Grazing food chain: The grazing food chain is a type of food chain that starts with green plants, passes through herbivores and then to carnivores. In a grazing food chain, energy in the lowest trophic level is acquired from photosynthesis.

In this type of food chain, the first energy transfer is from plants to herbivores. This type of food chain depends on the flow of energy from autotrophs to herbivores. As autotrophs are the base for all ecosystems on Earth, the majority of ecosystems in the environment follow this kind of food chain.

Understanding food chains is vital, as they explain the intimate relationships in an ecosystem. A food chain shows us how every living organism is dependent on other organisms for survival. The food chain explains the path of energy flow inside an ecosystem.

Frequently Asked Questions on Food Chain

What are the first organisms in a food chain, what is the difference between the food chain and the food web.

A food chain follows a single path, where animals discover food. But a food web shows different paths, where plants and animals are connected. A food web comprises several food chains.

In a food chain, an organism eats a single item, whereas in a food web an organism consumes multiple items. In a food chain, there is a singular path for energy flow and in a food web, there are different paths for energy flow.

What role do humans play in a food chain?

What are animals called in a food chain, what do food chains end with.

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Diagram of Food Chain

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What is Food Chain?

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The diagram of food chain shows the flow of energy and nutrients through various organisms in an ecosystem in a linear fashion. The food chain starts with producers and ends with decomposers. A food chain diagram shows how energy passes within an ecosystem through organisms eating and being eaten. The diagram of the food chain class 6 and 7 is an important topic in the biology syllabus and is often asked in the examinations.

The food chain diagram with labels is given below:

Table of Content

Food Chain Levels in Ecosystem

Conclusion- diagram of food chain.

• FAQs- Diagram of Food chain

A food chain is a chronological pathway that depicts the transfer of energy from one organism to another organism. In an ecosystem comprising of producers, consumers, and decomposers, the energy flows in a defined and specific path. Energy can neither be created nor be destroyed but it flows from one level to the other, through different organisms.

Main components of food chain are:

• Producers: Organisms that produce their own food by the process of photosynthesis or chemosynthesis.
• Consumers: Feed on other organisms for energy.
• Decomposers: Organisms that break down dead and waste matter.

When one organism is eaten by another, majority of the energy is wasted and only a small amount of energy is transferred to the consumer. The levels of food chain are mentioned below:

• The food chain starts with the producers or autotrophs. They use energy from sunlight to synthesize their own food through the process of photosynthesis.
• The second link in the food chain are the consumers. They get their energy from the food they eat. The primary consumers or herbivores such as rabbits or insects, eat plants.
• The next layer in the food chain comprise of animals that eat other animals. The first group consists of carnivores , such as snakes, who eat herbivores. The other group comprises of omnivores , who eat both plants and other animals. Usually, there are several levels, such as secondary consumers, tertiary consumers, and quaternary consumers, that all occupy this sector. Apex predators are the consumers at the top of the food chain.
• The last step of a chain are the decomposers , such as fungi, that use the remains of organisms to grow.

In conclusion, diagram of food chain is a simple and basic way to show the flow of energy in an ecosystem. It depicts the sequential transfer of energy from producers to consumers and eventually to decomposers, highlighting the interconnectedness of all organisms in sustaining life. A food chain is a continuous chain that shows who eats whom in a simple way. The food chain diagram with labels makes the understanding this process easier.

A lso Read: Food Chains and Food Webs Food Web – Definition, Diagram, Food Chain and Examples Food Chain: Definition, Types, Examples, FAQs

FAQs – Diagram of Food chain

What is food chain with diagram.

The food chain is a simple energy source diagram. It consists of producer, primary consumer secondary consumer, tertiary consumer and a decomposer.

What is called Food Chain?

A food chain is a linear sequence of organisms which shows how nutrients and energy pass when an organism eats other organism.

Why is the Food Chain Important?

Food chain is very important because it shows the intricate relationships in ecosystems and it also reveals how each organism depends on other for survival.

Is a Food Chain a Chart?

A food chain is a descriptive diagram having a series of arrows, each pointing from one species to another, depicting the flow of energy from one organisms to another.

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26.2: Food Chains and Food Webs

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• Page ID 124051

• Teresa Friedrich Finnern
• Norco College

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Learning Objectives

• Compare and contrast betrween a food chain and a food webs
• Describe energy transfer efficiency as it relates to trophic levels

Food Chains

A food chain is a linear sequence of organisms through which nutrients and energy pass as one organism eats another. Each organism in a food chain occupies a specific trophic level (energy level), its position in the food chain. The first trophic level in the food chain is the producers. The primary consumers (the herbivores the eat producers) are the second trophic level. Next are higher-level consumers. Higher-level consumers include secondary consumers (third trophic level), which are usually carnivores that eat the primary consumers, and tertiary consumers (fourth trophic level), which are carnivores that eat other carnivores. Higher-level consumers feed on the next lower tropic 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 \(\PageIndex{1}\), 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. Much of the energy from one tropic level to the next is lost as heat, due to the second law of thermodynamics. Only about 10% of the energy transfers from one trophic level to the next trophic level. Thus, after several 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.

While food chains are simple and easy to analyze, there is a one problem when using food chains to describe most communities. Even when all organisms are grouped into appropriate trophic levels, some of these organisms can feed at more than one trophic level. In addition, species feed on and are eaten by more than one species. In other words, the linear model of trophic interactions, the food chain, is a hypothetical and overly simplistic representation of community 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. A food web is a concept that accounts for the multiple trophic interactions between each species (Figure \(\PageIndex{2}\)).

Community Productivity and Transfer Efficiency

The rate at which photosynthetic producers incorporate energy from the sun is called gross primary productivity . In a cattail marsh, plants only trap 2.2% of the energy from the sun that reaches them. Three percent of the energy is reflected, and another 94.8% is used to heat and evaporate water within and surrounding the plant. However, not all of the energy incorporated by producers is available to the other organisms in the food web because producers must also grow and reproduce, which consumes energy. At least half of the 2.2% trapped by cattail marsh plants is used to meet the plants own energy needs.

Net primary productivity is the energy that remains in the producers after accounting for the metabolic needs of the producers and heat loss. The net productivity is then available to the primary consumers at the next trophic level. One way to measure net primary productivity is to collect and weigh the plant material produced on a m 2 (about 10.7 ft 2 ) of land over a given interval. One gram of plant material (e.g., stems and leaves), which is largely carbohydrate, yields about 4.25 kcal of energy when burned. Net primary productivity can range from 500 kcal/m 2 /yr in the desert to 15,000 kcal/m 2 /yr in a tropical rain forest.

In an aquatic community in Silver Springs, Florida, the gross primary productivity (total energy accumulated by the primary producers) was 20,810 kcal/m 2 /yr (Figure \(\PageIndex{3}\)). The net primary productivity (energy available to consumers) was only 7,632 kcal/m 2 /yr after accounting for energy lost as heat and energy require to meet the producer's metabolic needs.

Only a fraction of the energy captured by one trophic level is assimilated into biomass, which makes it available to the next trophic level. Assimilation is the biomass of the present trophic level after accounting for the energy lost due to incomplete ingestion of food, energy used to conduct work by that trophic level, and energy lost as waste. Incomplete ingestion refers to the fact that some consumers eat only a part of their food. For example, when a lion kills an antelope, it will eat everything except the hide and bones. The lion is missing the energy-rich bone marrow inside the bone, so the lion does not make use of all the calories its prey could provide. In Silver Springs, only 1103 kcal/m 2 /yr from the 7618 kcal/m 2 /yr of energy available to primary consumers was assimilated into their biomass. (The trophic level transfer efficiency between the first two trophic levels was approximately 14.8 percent.)

Attributions

Modified by Kammy Algiers from the following sources:

2.2.1.1.4: Food Chains and Food Webs - from Biology by OpenStax (licensed CC-BY )