Heterotrophs are organisms that cannot produce their own food and must obtain nutrition by consuming organic carbon from other sources, mainly plant or animal matter

. They rely on organic compounds for energy and carbon, unlike autotrophs, which synthesize their own food from inorganic substances like carbon dioxide

. Heterotrophs include all animals, fungi, many protists, some bacteria, and even some parasitic plants

. They occupy the consumer levels in the food chain (primary, secondary, tertiary consumers) rather than the producer level

. Examples include humans, animals, fungi, and many bacteria

. There are different types of heterotrophs based on their energy sources:

• Chemoheterotrophs : Obtain energy from chemical compounds, typically by consuming organic matter (e.g., humans and mushrooms)

• Photoheterotrophs : Use light as a supplemental energy source but still require organic carbon from other organisms (e.g., some bacteria like green non-sulfur bacteria)

Heterotrophs can also be classified by the type of compounds they use as electron sources:

• Organotrophs : Use organic compounds (carbohydrates, fats, proteins) as electron donors.
• Lithotrophs : Use inorganic compounds (ammonium, nitrite, sulfur) as electron donors

In summary, heterotrophs are organisms that depend on consuming other organisms or organic matter to obtain energy and carbon for survival, growth, and reproduction, distinguishing them from autotrophs that produce their own food