Select all of the responses that correctly complete the sentence and describe the Cambrian fuse. The Cambrian fuse that caused the Cambrian explosion __. Group of answer choices Can’t ever be known because of lack of evidence May have been related to the changing biotic composition of the oceans May have been related to catastrophic impact of asteroids May have related to increasing levels of ocean oxygen
The correct answer and explanation is:
The correct responses that complete the sentence and describe the Cambrian fuse are:
- May have been related to the changing biotic composition of the oceans
- May have been related to increasing levels of ocean oxygen
Explanation (300 words):
The “Cambrian fuse” is a term used to describe the set of environmental and biological conditions that triggered the Cambrian explosion, a major evolutionary event approximately 541 million years ago when most major animal phyla rapidly appeared in the fossil record.
1. Changing Biotic Composition of the Oceans:
Before the Cambrian explosion, the oceans experienced significant shifts in the types and interactions of organisms. The development of new ecological relationships such as predation, competition, and symbiosis likely created evolutionary pressures that promoted rapid diversification and complexity in life forms. The emergence of new body plans and behaviors can be seen as a biological “fuse” that ignited an evolutionary burst.
2. Increasing Levels of Ocean Oxygen:
Oxygen levels in Earth’s oceans and atmosphere gradually increased before the Cambrian period. Higher oxygen concentrations made it possible for more complex and metabolically demanding organisms to evolve, supporting bigger bodies and more active lifestyles. This oxygen boost is widely considered a critical environmental trigger for the Cambrian explosion because oxygen availability strongly influences animal physiology and the potential for complex multicellularity.
What the Cambrian fuse is NOT likely related to:
- The idea that it “can’t ever be known because of lack of evidence” is overly pessimistic. While the fossil record from that time is incomplete, ongoing research combining geology, paleontology, and geochemistry is shedding light on the causes behind the Cambrian explosion.
- The role of catastrophic asteroid impacts is not supported by strong evidence in this context. Unlike mass extinction events, there is no clear asteroid impact linked to the Cambrian explosion, so this is unlikely to be a direct cause.
In summary, the Cambrian fuse likely involved a combination of rising oxygen levels and shifts in oceanic ecosystems, which together provided the conditions necessary for the rapid diversification of complex animal life.