Consumers are organisms of an ecological food chain

Food chain

A food web depicts feeding connections in an ecological community. Ecologists can broadly lump all life forms into one of two categories called trophic levels: 1) the autotrophs, and 2) the heterotrophs...

that receive their energy by consuming other organisms. These organisms are formally referred to as heterotroph

Heterotroph

A heterotroph is an organism that cannot fix carbon and uses organic carbon for growth. This contrasts with autotrophs, such as plants and algae, which can use energy from sunlight or inorganic compounds to produce organic compounds such as carbohydrates, fats, and proteins from inorganic carbon...

s, which includes animal

Animal

Animals are a major group of multicellular, eukaryotic organisms of the kingdom Animalia or Metazoa. Their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later on in their life. Most animals are motile, meaning they can move spontaneously and...

s, bacteria

Bacteria

Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...

 and fungus

Fungus

A fungus is a member of a large group of eukaryotic organisms that includes microorganisms such as yeasts and molds , as well as the more familiar mushrooms. These organisms are classified as a kingdom, Fungi, which is separate from plants, animals, and bacteria...

.

Classification

Consumers are typically viewed as predatory animals such as the wolf and hyena. However, herbivorous animals and parasitic fungus can also be consumers. Some carnivorous plants, like the Venus flytrap

Venus Flytrap

The Venus Flytrap , Dionaea muscipula, is a carnivorous plant that catches and digests animal prey—mostly insects and arachnids. Its trapping structure is formed by the terminal portion of each of the plant's leaves and is triggered by tiny hairs on their inner surfaces...

, exhibit both characteristics of a consumer and producer and therefore can be classified as both.

Levels

Within an ecological food chain, consumers are categorized into three groups: primary consumers, secondary consumers, and the tertiary consumers. Primary consumers are usually herbivores, feeding on plants and fungus. Secondary consumers, on the other hand, are mainly carnivorous

Carnivore

A carnivore meaning 'meat eater' is an organism that derives its energy and nutrient requirements from a diet consisting mainly or exclusively of animal tissue, whether through predation or scavenging...

 and prey other animals. Omnivores, who feed on both plants and animals, can also be considered as a secondary consumer. Tertiary consumers, sometimes also known as an apex predator

Apex predator

Apex predators are predators that have no predators of their own, residing at the top of their food chain. Zoologists define predation as the killing and consumption of another organism...

, are usually on top of a food chain, capable of feeding on secondary consumers and primary consumers. Tertiary consumers can be either fully carnivorous or omnivorous. Human

Human

Humans are the only living species in the Homo genus...

s are one such example of a tertiary consumer.

Importance to the ecosystem

Consumers dominate most of a food chain

Food chain

A food web depicts feeding connections in an ecological community. Ecologists can broadly lump all life forms into one of two categories called trophic levels: 1) the autotrophs, and 2) the heterotrophs...

. Consumers have important roles to play within an ecosystem

Ecosystem

An ecosystem is a biological environment consisting of all the organisms living in a particular area, as well as all the nonliving , physical components of the environment with which the organisms interact, such as air, soil, water and sunlight....

such as balancing the food chain by keeping animal populations at a reasonable number. Without proper balance, an ecosystem can collapse and cause the decline of all affected species.