Paleozoic Era

Anomalocaris canadensis, The largest marine predator during the Cambrian Explosion. (Click to Expand)

Layout of the continents during the Paleozoic Era (Click to Expand)

Silurian Period

443-416 MA

Paleozoic Era

542-251 million years ago

The Paleozoic Era saw an increase in the oxygen levels in the atmosphere. The Cambrian Explosion occured during this era and was a boom in the variety of life.

Climate Conditions

Cambrian Explosion

Variety of Life

Interesting Facts

542-488 MA

Cambrian Period

488-443 MA

Ordovician Period

443-359 MA

Devonian Period

359-299 MA

Carboniferous Period

299-251 MA

Permian Period

References

• The first asymmetrically dividing cells evolved during this era. This allowed for specialized cells in more advanced metazoan species.
• Early Paleozoic Era saw a large increase in calcium concentration and caused tissue hardening amongst early metazoan species.
• This period was the emergence of animals on Earth.
• During the Cambrian explosion, the sea level was at a constant rise and stayed above present day levels until the end of the paleozoic era.

Interesting Facts

References

Scholarly referencesSaul, J. M. (2022). The Cambrian explosion as a Black Box: a qualitative appreciation. International Geology Review., 64(15–16), 2378–2384. https://doi.org/10.1080/00206814.2021.2015631 Zhuravlev, A. Y., & Wood, R. A. (2018). The two phases of the Cambrian explosion. Scientific Reports, 8(16656)https://doi.org/10.1038/s41598-018-34962-y Zhang, X., & Shu, D. (2014). Causes and consequences of the Cambrian explosion. Science China.Earth Sciences, 57(5), 930-942. https://doi.org/10.1007/s11430-013-4751-x Came, R. E., Eiler, J. M., Veizer, J., Azmy, K., Brand, U., & Weidman, C. R. (2007). Coupling of surface temperatures and atmospheric CO2 concentrations during the Palaeozoic era. Nature, 449(7159), 198-201. https://doi.org/10.1038/nature06085 Haq, B. U., & Schutter, S. R. (2008). A chronology of Paleozoic sea-level changes. Science, 322(5898), 64-68. https://doi.org/10.1126/science.1161648 Images from: Crick, R. E. , Johnson, . Markes E. and Robison, . Richard A. (2024, January 9). Cambrian Period. Encyclopedia Britannica. https://www.britannica.com/science/Cambrian-Period Flannery, T. Fridtjof (2024, January 9). Cambrian explosion. Encyclopedia Britannica. https://www.britannica.com/science/Cambrian-explosion Zhuravlev, A. Y., & Wood, R. A. (2018). The two phases of the Cambrian explosion. Scientific Reports, 8(16656)https://doi.org/10.1038/s41598-018-34962-y

During the start of the Paleozoic era there was a high level of CO2 in the atmopshere which led to the Earth having a high temperature. Eventually, weathering effects between continental collisions in this period brought phosphorus to the ocean which allowed phytoplanktons to flourish and produce more oxygen. This led to oxygen levels in the atmopshere being increased and CO2 levels being decreased. These conditions both lowered the temperature and allowed life to flourish.

Climate Conditions

Khetatheca cotuiensis, fossil from the Paleeozoic era. This is one of the early lophophorates.

Aldanella attleborensis, fossil from Paleozoic era. This is one of the early molluscs.

Early variety of lophophorates also appeared during this period. Lophophorates are animals that have tentacles around their mouth that help them eat. Eventually evolved into modern lophopohorates including phoronid worms.

Variety of Life

Early variety of molluscs, which are marine animals with shells, appeared in this period. These eventually evolved into the modern molluscs inlcuding snails and mussels.

The Cambrian Explosion was an increase in the variety of life forms on Earth. The explosion could not start until enough oxygen had appeared in the atmosphere. Earth needed at least 25% of current atmosphere oxygen levels in order for life to diversify. Some point after this threshold was reached, aerobic organsisms started to appear. The most noteable type of life to come from this period was metazoan life forms. This classifcation includes many multicellular organisms that first appeared during the Cambrian Explosion.

Cambrian Explosion