Jay could hardly wait for dinner to end. His mind was racing with a hundred theories and ideas. It had taken the colonists less then 100 years to dramatically change the planet. Could the colonists' planetary "adjustments" have adjusted more than they intended? How had it affected the native creatures? Could the murky water be hiding new animals? Predators perhaps? And why had the people fled? Once at the computer counsel, Jay logged into his old biology book, and what he found shocked him:
"The Ediacaran Period (also referred to as the Vendian or Late Pre-Cambrian) occurred from approximately 700 million years ago until 543 million years ago Earth time. The period was noted for its simple soft-bodied Ediacaran fauna, mainly autotrophic chemo and photo autotrophs and symbionts as well as filter feeders and passive nutrient absorbers, all inhabiting the deep oceans (see "Burgess Shale"). Oxygen levels were still low (approx. 5%), although cyanobacteria (blue green bacteria) were slowly raising the O2 concentration. Great environmental and biological changes began that would have far-reaching impact. Massive glaciers dumped tons of sediment rich in nitrogen, sulfides, calcium carbonate, and phosphates into the seas, encouraging new life forms that grazed on the bacteria-covered nutrients, and providing the calcium carbonate and phosphates that would later be used to make shells. The oceanic and atmospheric oxygen concentration reached a threshold, wiping out some life forms while allowing others to raise their metabolic rates and thrive (see "Oxygen Revolution"). The appearance of early predators towards the end of the Pre-Cambrian signaled the shift in feeding styles from autotrophs to heterotrophs which is associated with the predator vs. prey "evolutionary arms race." This intensified struggle to survive encouraged faster mobility (possible because of O2 metabolism), shells and claws (i.e. increased mineral content of sea) and neural sophistication (nerve nets to ganglia and eventually brains). Together these environmental and biological factors led to the "Cambrian Explosion," a period of fantastic evolutionary change and diversity lasting over several million years and beginning approx. 543 million years ago. In that short period, all but one of the major phylum and body patterns evolved." --On-line text: Evolutionary Biology: Earth and Beyond, 2660.
Now he was getting somewhere. Jay took the creased sketch paper from his pocket and compared the strange drawings to the text book illustrations. Sure enough, the paper matched almost exactly the ancient fossil illustrations from the screen. Jay looked at the simple drawings in awe. How, he wondered, could creatures from the Earth’s distant past have surfaced on an alien planet millions of years in the future? Although the planet had originally seemed to fit Pre-Cambrian Earth’s calm description, there had been no major glacial events, no undersea volcanos or millenniums of oxygen-building bacteria. Could the colonists have inadvertently tipped a planet on the edge of an alien "Cambrian Explosion."
Jay was getting uneasy. Let us assume, he thought, that the early colonists found conditions here similar to Earth’s Pre-Cambrian, and that this simple planet was indeed slowly changing as Earth had been in the Pre-Cambrian, and let us say that the colonists speeded up the process exponentially by dumping in oxygen and sediments. Assuming that the environment and organisms were able to evolve at an incredible speed--"break neck evolution" was a recognized phenomenon on some alien planets. If the path of evolution on P-L5 had followed that on Earth, seas would have turned murky with sediment, "Ediacaran fauna" given way to a host of shelled, swimming and burrowing creatures clogging the water pipes. Predators like Earth's three-foot-long Anomalocaris would have scared tourists and residents alike. Perhaps a frightened populace decided to get out before it was too late, before the new creatures emerged from the sea to take their first steps on land as Earth's creatures had later done. Tomorrow he and his colleagues would have to make a decision that would affect hundreds of people and an entire planet: Whether to re-colonize P-L5 or leave it for good. What he needed was information--enough to convince an entire team of scientists, investors, judges and colonists of just what they were getting into.
Discussion Questions:
Tomorrow you will be expected to present a full report on the environmental and biological conditions on P-L5 as well as a decision on re-colonization. Each member of your group will represent one interest in this decision such as scientist, colonist, investor, etc., and will have to support your group’s decision before a preliminary court. Be prepared to justify your decision with theories on evolution as well as actual examples from Earth. In addition to other materials, you will need to know: