Food chains & food webs (article) | Ecology | Khan Academy
The food chain is the sequence in a food web, starting from aspecies called producers and ending in a species calleddecomposers. Trophic level is the position. Ecology: The study of the interrelationships between living organisms and the living and in general characteristics and in their relationships to the physical environment. A food chain or food web comprises a sequence of organisms through which to consumers and the major feeding levels are called Trophic Levels. Food chains and trophic levels both look at what an organism does for energy. As you move up a food chain, you are typically moving into a higher tropic level.
Autotrophs form the base of food chains and food webs, and the energy they capture from light or chemicals sustains all the other organisms in the community.
When we're talking about their role in food chains, we can call autotrophs producers. Heterotrophs, also known as other-feeders, can't capture light or chemical energy to make their own food out of carbon dioxide. Instead, heterotrophs get organic molecules by eating other organisms or their byproducts.
Animals, fungi, and many bacteria are heterotrophs.
THE ECOSYSTEM: INTERRELATIONSHIPS BETWEEN
When we talk about heterotrophs' role in food chains, we can call them consumers. As we'll see shortly, there are many different kinds of consumers with different ecological roles, from plant-eating insects to meat-eating animals to fungi that feed on debris and wastes. Food chains Now, we can take a look at how energy and nutrients move through a ecological community.
Let's start by considering just a few who-eats-who relationships by looking at a food chain.
Food chains & food webs
A food chain is a linear sequence of organisms through which nutrients and energy pass as one organism eats another. Let's look at the parts of a typical food chain, starting from the bottom—the producers—and moving upward.
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 eaters 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 apex consumers. We can see examples of these levels in the diagram below.
The green algae are primary producers that get eaten by mollusks—the primary consumers. The mollusks then become lunch for the slimy sculpin fish, a secondary consumer, which is itself eaten by a larger fish, the Chinook salmon—a tertiary consumer.
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.
For instance, humans are omnivores that can eat both plants and animals. Decomposers One other group of consumers deserves mention, although it does not always appear in drawings of food chains. This group consists of decomposers, organisms that break down dead organic material and wastes.
Decomposers are sometimes considered their own trophic level. As a group, they eat dead matter and waste products that come from organisms at various other trophic levels; for instance, they would happily consume decaying plant matter, the body of a half-eaten squirrel, or the remains of a deceased eagle. In a sense, the decomposer level runs parallel to the standard hierarchy of primary, secondary, and tertiary consumers.
Fungi and bacteria are the key decomposers in many ecosystems; they use the chemical energy in dead matter and wastes to fuel their metabolic processes. Other decomposers are detritivores—detritus eaters or debris eaters. Species that feed on primary consumers. Secondary and higher order consumers are called Carnivores. Tertiary and higher level Consumers: Species that obtain their nourishment by eating other meat-eating species.
Species that obtain their nourishment from eating both plants and animal species. Also called Omnivores 3. They are the final link in the food chain. Comprise of organisms that feed on dead matter and break it down to release chemical energy back into the soil for plants to re-use them. A food chain or food web comprises a sequence of organisms through which energy and nutrients are taken in and used up.Ecosystem Ecology: Links in the Chain - Crash Course Ecology #7
A food chain in a wet meadow could be: Food chains begin from producers to consumers and the major feeding levels are called Trophic Levels. Producers belong to the First Trophic Level. Primary consumers, whether feeding on living or dead producers feed from the Second Trophic Level. Organisms that feed on other consumers belong to the Third Tropic Level.
Examples include ticks, fleas, mosquitoes, mistletoe plants and fungi. Plant and animal species compete over food, water, territorial space and mating with the opposite sex. The Principle of Competitive Exclusion: