Which Types of the Three Protists Are Heterotrophs?

Protista

• The kingdom Protista is extremely varied. Members can be unicellular, having one cell, multicellular, having many cells, and colonial, in which many unicellular organisms of the same species live and act in a coordinated fashion. Essentially, this kingdom is used to categorize any organism that does not fit well into one of the other kingdoms. There are a few characteristics that are found in all protists: they are eukaryotic and aerobic and have a true nucleus and mitochondria.

Heterotrophs

• Because protists are so varied, they are roughly categorized by how they acquire energy and nutrients. There are three general categories: animal-like protists, plantlike protists and funguslike protists. The plantlike protists are autotrophs. Autotrophs are organisms that gain energy from inorganic sources, as plants do through photosynthesis. The fungus and animal-like protists are heterotrophs. Heterotrophs are organisms that obtain their energy from ingesting other organisms.

Protozoa

• Animal-like protists are called protozoa. Protozoa are divided into four categories based upon their method of movement: zooflagellates, which use flagella; sarcodines, which move by extending their cytoplasm; ciliates, which have cilia; and sporozoans, which have no method of movement. All four types absorb or engulf other organisms for nutrients. Some have mouthlike structures for absorbing organisms and others use portions of their cytoplasm to engulf an organism, creating a structure called a food vacuole.

Slime Molds

• Slime molds are funguslike protists. Unlike true fungi, slime molds are mobile and move like an amoeba by extending parts of their bodies. They are unusual in that they typically exist as single-celled organisms but can collect into a large, multicellular organism to reproduce. They often live in soil, decaying wood and other decaying materials and absorb nutrients from the surface of decaying materials, typically bacteria. In this respect they are much like protozoa as well as like fungi, which absorb nutrients from decaying materials.