An enormous atmospheric containment unit designed to preserve any inside organisms from hazardous elements beyond the radius of the dome. SG-1 has encountered at least four designs from distinct species that could be considered bio-domes. SG-1 found a planet where the local inhabitants lived under the threat of deadly ultraviolet rays from their sun. But the team helped to find and activate a Goa'uld device that erected an energy dome over the village, protecting the people.
Visiting P7J-989, SG-1 encountered a dome that was maintained after the population destroyed the surface of the planet. The people within the dome were hard-wired into virtual reality units to maintain their neurological activity and wait out the destruction beyond the dome as the world revitalized itself over hundreds of years.
A protective dome also protected an advanced alien city from an ice age on their world. But while touring the city, SG-1 discovered that the city's power was provided by an underground slave labor force -- people who did not know that the surface above was livable.
SG-1 encountered a unique, energy-based bio-dome on P3X-289, roughly 2.2 kilometers wide and 500 meters high. The planet's atmosphere had been filled with sulfur dioxide, carbon monoxide, methane and ammonia, so an energy dome was erected to prevent the toxic atmosphere from reaching the last survivors of the civilization. This dome generated a static charge and a heavy resistance field to let people know when they were about to step beyond it.
This field was permeable to solid objects, but wouldn't let the atmosphere in, and was capable of "scrubbing" any object that entered the barrier -- protecting the inside from the hazardous external atmosphere. Even radio waves were blocked from permeating this dome.
In this dome everything was self-sufficient. A super-computer that maintained the dome drew energy from geothermal vents beneath the surface. The dome was at least 400 years old. Two hundred years ago it lost containment and started to shrink. The computer began to systematically kill the local townspeople as the dome shrank, in order to accommodate the smaller dome, and altered their memories via a network called "The Link" to prevent them from learning the truth.
The First Commandment - SG-1 journeys to a world where the population is deprived of a sun shield dome capable of protecting the entire people from deadly ultraviolet rays.
The Gamekeeper - SG-1 encounters a civilization entirely maintained within a bio-dome while their subconscious minds are kept alive in a virtual reality world.
Beneath the Surface - The team discovers that a civilization living with a protective dome in order to survive an ice age is using a slave labor force beneath their city.
Frozen - SG-1 returns to Antarctica to a bio-dome maintained for several scientists who have just made a startling discovery -- an Ancient female encased in ice.
Revisions - SG-1 arrives on a planet plagued by toxic gasses but discovers a thriving populace within a shrinking bio-dome.