Heterotrophs are not able to produce food, unlike the producers. Since they consume other organisms, heterotrophs are the consumers in a food web. In any ecosystem, they are found at all levels of the food chain. Every level has a critical role to play in the ecosystem.

Heterotrophic organisms that are primary consumers eat autotrophic plants. They are known as herbivores as well. They can also feed on other organisms that can synthesize their own food i.e., phytoplankton and photosynthesis bacteria. E.g., A deer in a forest, a sea snail on a coral reef, an elephant in an African savannah, etc.

Heterotrophs that are secondary consumers eat herbivores. They are meat-eaters and also known as carnivores. E.g., Wolf in a forest feeding on deer, a salamander in a forest eating snails, a Giant Triton (a giant marine snail) on a coral reef eating other smaller sea snails, lions eating the elephant in an African savannah. These are secondary consumers because they feed on primary consumers.

Some heterotrophs can eat primary as well as secondary consumers. These are known as tertiary consumers or top predators. E.g., Wolves eating fox (a carnivore), Sharks eating fish, Lions in African Savannah feeding on a crocodile.

In the ocean, Orcas are top predators because they can eat sharks as well. In birds, eagles or hawks are considered top predators. On a coral reef, a Crown of Thorn Seastar is a top predator. Humans are also considered top predators. Some heterotrophs can feed on primary producers as well as consumers. They are known as omnivores.

All the animals are heterotrophs but they are classified based on what they eat. Most herbivores only feed on plants and other autotrophs. Others can be both primary and secondary consumers. E.g., Bear, Human – they can eat plant products as well as other animals.

Humans are heterotrophs. Those who eat both plants and animals are omnivores. Heterotrophs recycle organic chemicals by eating other organisms. They use these organic chemicals in their body for nutrition and then defecate, therefore helping seeds to germinate and spread to other areas of the environment.

Some plant seeds with a thick coat, have to pass through the digestive system of a consumer to germinate. This process wakens the seed coat thus helping the plant embryo to emerge. This process is known as scarification. Heterotrophs also increase land fertility with their feces.

Consumers or predators keep the population of their prey in control. Hence, have high ecological importance. For example, a review of studies by Ballard et al. (2001) suggests in the United States, the size of deer populations depends on the population size of coyotes, mountain lions, and wolves in that area.

A thirty-year study in Isle Royale, Michigan clearly shows how wolves and moose interact. The size of the moose population in an area determines the size of the wolf pack. The size of the wolf pack increases when the moose population increases and vice versa. Predators help in keeping the population of their prey healthier.

Because they tend to eat weaker individuals or the ones that are less likely to survive. Places, where predators have been hunted or eliminated, tend to have unhealthy ecosystems. For example, many areas in the United States, have shown a considerable decrease in the population of wolves, coyotes, and other predators.

This has lead to the overpopulation of deer, which results in overgrazing which in turn has caused erosion and barren landscapes. Along with this, the spread of diseases increases in a population because unhealthy individuals are not eliminated.