Final answer:
Normal microbiota are integral to human health, occupying potential pathogen niches, protecting against infections, and supporting vital bodily functions through competitive exclusion and the production of antimicrobial substances.
Step-by-step explanation:
The normal microbiota are the organisms that typically reside on and in your body. These resident microbiota are crucial for human health as they occupy niches that could potentially be filled by pathogenic microorganisms. The microbiota play a protective role; for example, Lactobacillus spp. in the vagina produce lactic acid that helps maintain an acidic environment, inhibiting the growth of harmful yeasts. Notably, when antibiotics disrupt these microbial populations, the risk of secondary infections can increase. In the gastrointestinal tract, these helpful organisms outcompete potential pathogens for space and nutrients, a phenomenon known as competitive exclusion. Additionally, they produce bacteriocins to fight susceptible bacteria.
Hygiene and diet are factors that can alter the composition of both resident and transient microbiota. The skin's normal microbiota protects against infection by producing antimicrobial substances and preventing colonization by more harmful microbes. These commensal organisms have established a symbiotic relationship with the human body, contributing not only to defense against pathogens but also to digestion and nutrient production.
Therefore, the correct response is that normal microbiota protect against infection by pathogens.