What is the definition of a strict heterotroph?

Answer 1

A heterotroph is any organism that requires organic substrates in order to survive. It is a consumer which must eat other plants and animals, and cannot produce its own food.

Answer 2

A strict heterotroph is an organism that cannot produce its own food and relies entirely on external sources of organic carbon to meet its nutritional requirements. This means they must consume other organisms or their byproducts in order to obtain energy for growth and survival.