Final answer:
Thermally dimorphic fungi like Histoplasma capsulatum can exist as molds or yeasts depending on environmental temperatures. When inhaled, they transition to yeast in the warm environment of the lungs and can cause diseases such as histoplasmosis.
Step-by-step explanation:
The term for a dimorphic fungus that is found as a mold in the environment but transitions to a yeast form in the lungs once inhaled is thermally dimorphic.
Some fungi are capable of existing in different physical forms, known as dimorphic fungi, depending on their environment. An example of such a fungus is Histoplasma capsulatum, which is found in soil contaminated with bird or bat feces. At cooler temperatures (around 25°C), these fungi exist as mold with a mycelium structure.
However, when their spores are inhaled and exposed to the higher temperatures of the human body (around 37°C), they alter their form to become yeast. This adaptive capability allows the fungus to thrive and multiply within the lungs, where it can cause respiratory diseases such as histoplasmosis.