What is Phanerozoic Eon?
Phanerozoic eon means the eon comprising the Paleozoic, Mesozoic, and Cenozoic eras. The phanerozoic eon is the present geological eon in the geological time scale and the era during which abundant plant and animal life have existed. The phanerozoic period covered 541 million years to the present.
The phanerozoic era begins with the Cambrian period when animals initially developed hard shells preserved in the fossil record. The time before the phanerozoic era is known as the Precambrian and is divided into Haiden, Arches, and Proterozoic eras.
The period of the phanerozoic eon starts with the instant appearance of the fossilized evidence of several animals phyla, the evolution of those phyla into different forms, the development and emergence of complex plants, the evolution of fish, insects, and tetrapods, and also the development of modern fauna. The plant life on land appeared early in the phanerozoic era. During the phanerozoic eon, the tectonic force which moved into the continent had collected them into a single landmass known as the Pangea (the most latest continent) which then further divided into current continental landmasses.
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Phanerozoic Meaning
The term phanerozoic is derived from the Ancient word φανερός (phanerós) meaning visible and ζωή (zōḗ) meaning life, as it was once believed that the life began in Cambrian, the first period of the phanerozoic eon. The term “ phanerozoic” was first introduced by the American geologist George Halcott Chadwick (1876–1953).
The Phanerozoic eon era includes the instant evolution of several animal phyla, the evolution of terrestrial plants, complex plants, fish, and terrestrial animals, and the development of modern faunas and human beings.
Phanerozoic Eon Definition
The phanerozoic eon definition states that it is the interval of geologic time spanning from the appearance of abundant, macroscopic, hard-shelled fossils, approximately 542 million years ago (mya) to the present time.
The phanerozoic timeline given below shows some of the life forms that developed during the phanerozoic era. Life steadily became more diversified and new species developed. Most of the new-age organisms that emerged from species are now extinct.
Phanerozoic Timeline
Phanerozoic Eon Era
The phanerozoic eon is divided into three eras namely the Paleozoic, the Mesozoic, and the Cenozoic. This phanerozoic eon era is further subdivided into 12 periods. The Paleozoic era experienced the evolution of amphibians, reptiles and fish. The Mesozoic era experienced the evolution of snakes, lizards, crocodiles, mammals, and dinosaurs (including birds). The Cenozoic era begins with the extinction of non-avian dinosaurs and also undergoes the evolution of great diversity in birds and mammals. Human beings evolved at the end of the Cenozoic era.
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Biodiversity During the Phanerozoic
It has been observed that changes in biodiversity during the Phanerozoic is much better correlated with the hyperbolic model (immensely used in demography and macro sociology) than with exponential and logistic models (commonly used in biology and also applied extensively to fossil biodiversity).
The logistic models imply that changes in diversity are abided by first-order positive feedback (more ancestors, and more descendants) or negative feedback that arises from the limitation of resources, or both. The hyperbolic model means second-order positive feedback. The hyperbolic pattern of the human population growth emerges from quadratic positive feedback, caused by the interaction of the population size and the rate of technological growth.
The characteristics of the growth of biodiversity during the Phanerozoic Eon can be similarly judged by feedback between the diversity and community structure complexity. It is recommended that the similarity between the biodiversity curves and human population probably comes from the fact that both are derived from the juxtaposition on the hyperbolic trend of cyclical and random dynamics.
Phanerozoic Eon Era Facts and Information
The phanerozoic eon is defined as the current time in geological time scale.
It is the era in which abundant life has existed.
The phanerozoic era covers 541 million years and goes back to the time when hard-shelled animals first appeared.
The time before the phanerozoic era is known as the Precambrian, and is now divided into Hadean, Archean, and proterozoic eon.
FAQs on Phanerozoic Eon
1. What is the Phanerozoic Eon?
The Phanerozoic Eon is the current geological eon in Earth's history, which started approximately 541 million years ago and continues to the present day. Its name means "visible life," because this eon is characterised by the abundance of animal and plant fossils, marking a period of rapid evolution and diversification of complex, multicellular life.
2. What are the three eras of the Phanerozoic Eon?
The Phanerozoic Eon is divided into three major eras, each representing a significant stage in the evolution of life. These are:
- Paleozoic Era ("Ancient Life"): From 541 to 252 million years ago. Known for the Cambrian explosion, the rise of fish, amphibians, and early reptiles.
- Mesozoic Era ("Middle Life"): From 252 to 66 million years ago. Famously known as the "Age of Dinosaurs."
- Cenozoic Era ("New Life"): From 66 million years ago to the present. Known as the "Age of Mammals."
3. What were the major biological events of the Phanerozoic Eon?
The Phanerozoic Eon is marked by several pivotal biological events, including the Cambrian Explosion, where most major animal phyla appeared. Other key events include the colonisation of land by plants and animals, the evolution of vertebrates, the dominance and extinction of dinosaurs, and the subsequent rise of mammals and flowering plants.
4. How did the Earth's climate vary during the Phanerozoic Eon?
The Earth's climate has fluctuated dramatically throughout the Phanerozoic Eon. It has cycled between warm "greenhouse" periods with high sea levels and no polar ice caps, and colder "icehouse" periods, like the one we are currently in, which are characterised by continental glaciation. These climatic shifts were major drivers of both evolution and mass extinctions.
5. Why is the Phanerozoic Eon studied in more detail than the preceding eons?
The Phanerozoic Eon is studied in greater detail primarily due to the abundant fossil record. The evolution of hard parts like shells, skeletons, and teeth at the beginning of this eon led to a dramatic increase in the preservation of fossils. In contrast, life in the preceding Precambrian eons was mostly microbial and soft-bodied, leaving a much sparser and harder-to-interpret fossil record.
6. How did the movement of continents during the Phanerozoic Eon affect life?
Continental drift had a profound impact on life. The formation of the supercontinent Pangaea during the Paleozoic and its later breakup during the Mesozoic led to significant changes. These movements altered ocean currents, changed global climate patterns, and created and destroyed shallow sea habitats. The isolation of continents also led to the evolution of unique and distinct species in different parts of the world.
7. What is the main difference between the life forms of the Paleozoic, Mesozoic, and Cenozoic eras?
The primary difference lies in the dominant life forms. The Paleozoic was dominated by marine invertebrates like trilobites, fish, and the first land plants and animals. The Mesozoic is famously the "Age of Reptiles," dominated by dinosaurs on land, pterosaurs in the air, and marine reptiles in the sea. The Cenozoic, following the extinction of the dinosaurs, is the "Age of Mammals," which diversified to fill ecological niches across the planet.
8. Are we currently living in the Phanerozoic Eon?
Yes, we are currently in the Phanerozoic Eon. Specifically, we are in the Cenozoic Era, the Quaternary Period, and the Holocene Epoch. The Phanerozoic Eon has not ended; it encompasses the entire history of complex life on Earth up to and including the present day.
