A food chain is a linear sequence of organisms through which nutrients and energy pass when one organism eats another. In a food chain, each organism occupies a different trophic level, defined by the amount of energy transfers that separate it from the basic input of the chain. A common metric used to quantify the trophic structure of the food web is the length of the food chain. In its simplest form, the length of a chain is the number of links between a trophic consumer and the base of the web.
The average chain length of an entire network is the arithmetic average of the lengths of all the chains in the food chain. The food chain is a diagram of energy sources. The food chain starts with a producer, who is consumed by a primary consumer. The primary consumer can be consumed by a secondary consumer, who in turn can be consumed by a tertiary consumer.
Tertiary consumers can sometimes become prey to major predators known as quaternary consumers. For example, a food chain could start with a green plant as a producer, which is eaten by a snail, the main consumer. The snail could then fall prey to a secondary consumer, such as a frog, which in turn can be consumed by a tertiary consumer, such as a snake, which in turn can be consumed by an eagle. The food chain describes who eats whom in nature.
All living things, from single-celled algae to giant blue whales, need food to survive. Each food chain is a possible route that energy and nutrients can follow through the ecosystem. For example, grass produces its own food from sunlight. When the fox dies, bacteria break down its body and return it to the soil, where it provides nutrients to plants such as 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 beings can be part of multiple food chains. All the interconnected and overlapping food chains of an ecosystem form a food web.
Trophic levels Organisms in food chains are grouped into categories called trophic levels. Broadly 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 constitute the first level of every food chain.
Autotrophs are usually single-celled plants or 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 types. Algae, whose larger forms are known as seaweed, are autotrophic.
Phytoplankton, small organisms that live in the ocean, are also autotrophic. Some types of bacteria are autotrophic. For example, bacteria that live in active volcanoes use sulfur compounds to produce their own food. This process is called chemosynthesis.
The second trophic level is made up of organisms that feed on producers. These are called primary consumers or herbivores. Deer, turtles, and many types of birds are herbivorous. Tertiary consumers eat secondary consumers.
There may be more levels of consumers before a chain finally reaches its main predator. The main predators, also called supreme predators, feed on other consumers. Consumers can be carnivores (animals that feed on other animals) or omnivores (animals that feed on both plants and animals). Omnivores, like people, consume many types of food.
People eat plants, such as vegetables and fruits. We also eat animals and animal products, such as meat, milk and eggs. We eat mushrooms, like mushrooms. We also eat seaweed in edible seaweed such as 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 feed on the remains of non-living plants and animals. For example, scavengers, such as vultures, eat dead animals. Dung beetles eat animal feces, decomposers such as fungi and bacteria complete the food chain.
They convert organic waste, such as decaying plants, into inorganic materials, such as nutrient-rich soils. Decomposers complete the life cycle and return nutrients to the soil or oceans for use by autotrophs. This starts a whole new food chain. A food chain shows how every living being obtains its food.
Some animals eat plants and some animals eat other animals. For example, a simple food chain links trees and shrubs, giraffes (which feed on trees and shrubs) and lions (which eat giraffes). Each link in this chain is food for the next link. All food chains start with energy from the Sun.
This energy is captured by plants. Therefore, the living part of a food chain always begins with plant life and ends with an animal. A food chain is a linear network of links in a food web that begins with producing organisms (such as grass or algae, which produce their own food through photosynthesis) and ends in a species of supreme predator (such as brown bears or orcas), detritivores (such as worms or mealybugs) or a decomposed species (such as fungi or bacteria). These decomposers accelerate the decomposition process that returns mineral salts to the food chain for plants to absorb as nutrients.
These must then be intertwined and glued together to form a chain of species in which one eats the other. Food chains were first introduced by the Arab scientist and philosopher Al-Jahiz in the tenth century and were later popularized in a book published in 1927 by Charles Elton, who also introduced the concept of a food web. The food chain is a linear sequence of organisms in which nutrients and energy are transferred from one organism to another. There can't be too many links in a single food chain because the animals at the end of the chain wouldn't get enough food (and therefore energy) to stay alive.
Food chains Different habitats and ecosystems provide many possible food chains that form a food web. In the depths of the sea, there are food chains focusing on hydrothermal vents and cold leaks in the absence of sunlight. The trophic level refers to the sequential stages of a food chain, starting with producers at the bottom, followed by primary, secondary and tertiary consumers. Environmentalists have formulated and tested hypotheses about the nature of ecological patterns associated with the length of the food chain, such as the increase in length with the size of the ecosystem, the reduction of energy at each successive level, or the assertion that long food chains are unstable.
Since autotrophs are the basis of all Earth's ecosystems, most environmental ecosystems follow this type of food chain. When only one element is eliminated from the food chain, it can cause the extinction of a species in some cases. The length of a food chain is a continuous variable that provides a measure of the passage of energy and an index of ecological structure that increases through links from the lowest trophic (food) levels to the highest. Chemosynthetic bacteria and archaea use hydrogen sulfide and methane from hydrothermal vents and cold seeps as an energy source (just like plants use sunlight) to produce carbohydrates; they form the basis of the food chain.