Final answer:
A teratogen is an environmental agent that causes abnormal development in a fetus or embryo, with examples including alcohol and certain drugs, leading to conditions such as fetal alcohol spectrum disorders (FASD).
Step-by-step explanation:
An environmental agent that causes abnormal development in a fetus or embryo is referred to as a teratogen. Teratogens can include substances such as alcohol, drugs, and certain chemicals that, when a mother is exposed during pregnancy, can cross the placenta and affect the developing fetus. The effects of a teratogen on a fetus can range from minor to major and include physical malformations, cognitive impairments, and developmental delays. For instance, alcohol use during pregnancy is the leading preventable cause of intellectual disabilities in children in the United States and can result in fetal alcohol spectrum disorders (FASD), which are a collection of birth defects that can affect a child for their entire life.
It is important to differentiate teratogens from other types of agents such as mutagens, which cause genetic mutations; carcinogens, which are any agents that directly increase the incidence of cancer; and fetotoxic agents, which are harmful to the fetus but may not necessarily cause structural or functional defects from birth. Teratogens can have a variable impact depending on several factors, including the potency of the teratogen, the stage of fetal development during exposure, and the duration of exposure.