Cambrian Life Explosion Period (540MYA to 520MYA)

A Cambrian Life Explosion Period (540MYA to 520MYA) is a time period within the Cambrian period during the Paleozoic Era that included the emergence of aquatic multicellular, eukaryotic organisms.

• AKA: Cambrian Radiation, Cambrian Diversification, Biological Big Bang.
• Context:
  • It was (typically) associated with a dramatic increase in Atmospheric Oxygen Gas (Fox, 2016).
  • It can (typically) include the emergence of most Modern Animal Phyla.
  • It can (typically) involve evolutionary innovations such as developing Hard Body Parts, Predation, Complex Ecosystems, Advanced Motility, and Sensory Organs.
  • It can range from being influenced by increased atmospheric oxygen levels to environmental changes and developmental innovations.
  • It can (often) create new ecological niches and selective pressures.
  • …
• Example(s):
  • Furongian Cambrian Series, characterized by several extinction events and significant species diversity shifts, lasted from about 497 million years ago to 485.4 million years ago.
  • Miaolingian Cambrian Series, spanning from approximately 509 million years ago to 497 million years ago, marked by the appearance of the trilobite Oryctocephalus indicus and significant biostratigraphic markers.
  • Cambrian Series 2, also known as the unnamed second series, from about 521 million years ago to 509 million years ago, noted for the first appearance of trilobites and significant diversification of metazoans.
  • Terreneuvian Cambrian Series, the lowermost series of the Cambrian, from approximately 538.8 million years ago to 521 million years ago, characterized by the absence of trilobite fossils in its lower part and small shelly fossils in its upper part.
  • …
• Counter-Example(s):
  • a Devonian Period,
  • a Carboniferous Period,
  • an Ordovician Period,
  • an Ordovician-Silurian Extinction Event,
  • a Silurian Period.
• See: Phytoplankton, Calcimicrobe, Colony (Biology), Bryozoa, Ordovician, Metazoa, Extinction Event.

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References

2024

• Perplexity
  • The Cambrian Explosion, also known as the Cambrian Radiation or Cambrian Diversification, was a pivotal period in the history of life on Earth that occurred approximately 541-515 million years ago during the Cambrian period. During this relatively short span of 20-25 million years, the fossil record shows an astonishing diversification of complex multicellular organisms, with the emergence of most modern animal phyla. This evolutionary burst represents a major innovation and marked the transition from the predominantly microbial life forms of the preceding Ediacaran period to the rise of diverse and complex animals.
  • Key Evolutionary Innovations The Cambrian Explosion was characterized by several key evolutionary innovations that enabled the rapid diversification of life:
    1. Development of Hard Body Parts: Many animals evolved mineralized skeletal structures, shells, and exoskeletons, providing protection, support for larger body sizes, and better preservation potential as fossils . This includes the iconic trilobites with their segmented exoskeletons.
    2. Predation and Complex Ecosystems: The emergence of predators with specialized feeding structures like jaws and claws led to an evolutionary arms race, driving the development of defensive adaptations and complex ecological interactions . Predator-prey relationships became more prevalent.
    3. Motility and Complex Behaviors: Animals evolved advanced locomotion abilities, allowing them to actively hunt, graze, and burrow, facilitated by the development of muscles, appendages, and nervous systems . This enabled the exploration of new ecological niches.
    4. Sensory Organs: The evolution of sensory organs like eyes and antennae allowed animals to better perceive and interact with their environment, aiding in activities like hunting, avoiding predators, and finding mates .
  • Potential Drivers While the exact causes of the Cambrian Explosion are still debated, several factors have been proposed as potential drivers:
    1. Increased Oxygen Levels: A rise in atmospheric oxygen levels, possibly due to the proliferation of photosynthetic organisms, may have facilitated the evolution of larger, more complex organisms with higher metabolic demands .
    2. Environmental Changes: Factors like rising sea levels, changes in ocean chemistry, and the fragmentation of microbial mats on the seafloor could have created new ecological opportunities and selective pressures .
    3. Developmental Innovations: The emergence of new developmental pathways and gene regulatory networks may have enabled the rapid evolution of novel body plans and morphological diversity .
    4. Ecological Opportunities: The extinction of the Ediacaran fauna may have opened up new ecological niches, allowing the diversification of more complex and mobile organisms .
  • Citations:

[1] https://en.wikipedia.org/wiki/Cambrian_explosion
[2] https://davidson.weizmann.ac.il/en/online/sciencepanorama/explosion-life
[3] https://www.nationalgeographic.com/science/article/cambrian
[4] https://biologos.org/common-questions/does-the-cambrian-explosion-pose-a-challenge-to-evolution
[5] https://www.reddit.com/r/evolution/comments/i3mv2z/cambrian_explosion/
[6] https://evolution.berkeley.edu/the-cambrian-explosion/
[7] https://www.nps.gov/articles/000/cambrian-period.htm
[8] https://ucmp.berkeley.edu/cambrian/cambrian.php
[9] https://www.scientificamerican.com/article/what-sparked-the-cambrian-explosion1/

2022

• (Wikipedia, 2022) ⇒ https://en.wikipedia.org/wiki/Cambrian_explosion Retrieved:2022-8-21.
  • The Cambrian explosion, Cambrian radiation, Cambrian diversification, or the Biological Big Bang refers to an interval of time approximately in the Cambrian Period when practically all major animal phyla started appearing in the fossil record. It lasted for about 13  – 25 million years and resulted in the divergence of most modern metazoan phyla. The event was accompanied by major diversification in other groups of organisms as well. Before early Cambrian diversification,most organisms were relatively simple, composed of individual cells, or small multicellular organisms, occasionally organized into colonies. As the rate of diversification subsequently accelerated, the variety of life became much more complex, and began to resemble that of today. Almost all present-day animal phyla appeared during this period. A 2019 paper suggests that the timing should be expanded back to include the late Ediacaran, rather than just the narrower timeframe of the "Cambrian Explosion" event visible in the fossil record, based on analysis of chemicals that would have laid the building blocks for a progression of transitional radiations starting with the Ediacaran period and continuing at a similar rate into the Cambrian.

2018

• (PBS Eons, 2018) ⇒ PBS Eons. (2018). "From the Cambrian Explosion to the Great Dying." In: YouTube video. [1]
  • NOTE:
    • It provides a comprehensive overview of the Cambrian Explosion, highlighting key evolutionary innovations and potential drivers of this significant period in Earth's history.
    • The Cambrian Explosion was a period of rapid evolutionary diversification approximately 541 million years ago, marking the start of the Paleozoic Era.
    • This event led to the emergence of most modern animal phyla within a relatively short span of 20-25 million years.
    • Environmental triggers such as increased oxygen levels and changes in ocean chemistry played a crucial role in facilitating the diversification of life.
    • Many animals developed mineralized skeletal structures, shells, and exoskeletons, enhancing their preservation potential in the fossil record.
    • The evolution of sensory organs like eyes and antennae allowed animals to better interact with their environment.
    • Advanced locomotion abilities emerged, enabling animals to actively hunt, graze, and burrow, leading to more complex ecological interactions.
    • The first large predatory organisms, such as Anomalocaris, appeared during this period, hunting soft-bodied creatures.
    • Some animals, like Pikaia and Haikouella, developed the ability to swim with a flexible rod of cartilage, becoming the ancestors of vertebrates.
    • This evolutionary burst created new ecosystems with complex food webs that had not existed before.
    • The Cambrian period ended around 488 million years ago with a mass extinction event, possibly due to a sudden drop in oxygen levels.
    • Following the Cambrian, the Ordovician period experienced another burst of diversification, known as the Great Ordovician Biodiversification Event (GOBE).

2016

• (Fox, 2016) ⇒ Douglas Fox. (2016) "What sparked the Cambrian explosion?.” In: Nature, 530(268–270) doi:10.1038/530268a
  • QUOTE: The emerging evidence about oxygen thresholds and ecology could also shed light on another major evolutionary question: when did animals originate? The first undisputed fossils of animals appear only 580 million years ago, but genetic evidence indicates that basic animal groups originated as far back as 700 million to 800 million years ago. According to Lyons, the solution may be that oxygen levels rose to perhaps 2% or 3% of modern levels around 800 million years ago. These concentrations could have sustained small, simple animals, just as they do today in the ocean's oxygen-poor zones. But animals with large bodies could not have evolved until oxygen levels climbed higher in the Ediacaran.

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