Such places support unique biomes where many new microbes and other lifeforms have been discovered. Ironically it is microscopic Earth lifeforms that finally prove deadly to the Martian invasion force. Most such planets would nevertheless allow development of both simple and more complex lifeforms. Headcrabs are depicted as parasitic lifeforms roughly long. Among the oldest remnants of oxygen-producing lifeforms are fossil stromatolites. Prokaryotes were the dominant lifeforms throughout the Boring Billion. Insects are mostly soft bodied, fragile and almost defenseless compared to other, larger lifeforms. The area beneath these floating mats is exceptionally rich in aquatic lifeforms. Upon arriving, he found the dominant lifeforms to be only simple amphibians. Jennings and Nicolai discover a strange parasite in all of the lifeforms they find. Scientists debate whether submarine power cables are safe for underwater lifeforms. Both must slip into and possess the bodies of Earth lifeforms. The theme revolved around the concept of the lifeforms that could possibly exist on Mars. Promethium-147 can emit gamma rays during its beta decay, which are dangerous for all lifeforms. Predator culture revolves around the hunting and stalking of dangerous lifeforms.