Final answer:
The correct term for the microorganisms in the gastrointestinal tract is 'gut flora,' which includes a variety of microbes such as bacteria, archaea, and fungi, primarily Bacteroides and Firmicutes bacteria.
Step-by-step explanation:
The term that best defines the microorganisms residing in the gastrointestinal tract is gut flora. These microbes play a crucial role in digestion, immune function, and overall health. Types of microbes that live in the intestines include a diverse species of bacteria, archaea, and fungi. Notably, Bacteroides and Firmicutes bacteria are predominant.
Our digestive system contains normal microbiota consisting of these and other microbes, which is essential for proper functioning. However, alterations to the microbiota by antibiotics or diet changes can have detrimental effects. The microbiome within the digestive system can also be influenced by several factors like diet, age, lifestyle, and host health. It's important to note that no single bacteria species is universally present in all individuals but certain microbial patterns are commonly observed.