Oct 4, 2024 11:48 PM
(This post was last modified: Oct 4, 2024 11:51 PM by C C.)
Life on Earth was more diverse than classical theory suggests 800 million years ago, a Brazilian study shows
https://www.eurekalert.org/news-releases/1060345
INTRO: About 800 million years ago (mya), before the supercontinent Pangea formed, the Earth was more diverse than classical theory suggests. By reconstructing the tree of life from the evolutionary history of amoebas and the ancestors of algae, fungi, plants and animals, Brazilian researchers have created a scenario in which several different lineages of many species inhabited the planet during the period. An article reporting their findings is published in Proceedings of the National Academy of Sciences of the United States of America (PNAS).
According to the literature, several lineages of eukaryotes that first emerged 1.5 billion years ago diversified and established themselves during the Neoproterozoic oxygenation event (850-540 mya), when oxygen levels in the atmosphere and oceans rose significantly owing to changes in the planet’s geochemistry.
Eukaryotes are organisms consisting of one or more cells in which the DNA is contained within a distinct nucleus (all life on Earth except bacteria and archaea).
The study conducted by the researchers focused on the origin and divergence times of amoebozoans, showing that many of these organisms, as well as ancestors of plants, algae, fungi and animals, survived even the two glaciations of the Cryogenian period (790-635 mya, the middle Neoproterozoic Era, preceded by the Tonian and followed by the Ediacaran). According to the snowball earth hypothesis, polar ice extended to cover the entire planet for some 100 million years during this period.
“The classical paradigm for the Neoproterozoic was that there was practically no life on the planet apart from one or two species of bacteria and protists. In the last 15 years, however, fossils of unicellular, eukaryotic and heterotrophic organisms have been identified at various different locations around the world. These fossils date from about 800 mya [and are termed Tonian]. All this joined our study, which reconstituted the tree of life and used maximum likelihood estimation to identify several well-established Tonian lineages of ancestors of amoebae, animals, fungi and plants. This radically changes the paradigm for the manner in which the diversification of life occurred on our planet,” Daniel Lahr, last author of the article and a professor at the University of São Paulo’s Institute of Biosciences (IB-USP), told Agência FAPESP.
In other words, the study dates the mass diversification of life on Earth to some 260 million years earlier than the paradigm, well before the Cambrian explosion (the emergence of new multicellular organisms at the beginning of the Cambrian period between 541 and 530 mya). During this period, the Earth was inhabited mostly by marine invertebrates such as trilobites, brachiopods and graptolites, and had a warm and humid climate with no evidence of glaciers.
“The eukaryotes remained highly diverse despite all the climate changes that occurred during the Neoproterozoic, displaying greater adaptability than expected. This is important because our reconstitution of the phylogenetic tree also serves as a basis for paleoclimate reconstruction research,” Lahr explained.
“A curious aspect is that Arcellinid amoebae then lived in saltwater, whereas now they all live in freshwater. This kind of change is frequently observed in the course of evolution since time began, but it happened to all lineages in the case of these amoebae, showing once again how adaptable these organisms were.” (MORE - details, no ads)
https://www.eurekalert.org/news-releases/1060345
INTRO: About 800 million years ago (mya), before the supercontinent Pangea formed, the Earth was more diverse than classical theory suggests. By reconstructing the tree of life from the evolutionary history of amoebas and the ancestors of algae, fungi, plants and animals, Brazilian researchers have created a scenario in which several different lineages of many species inhabited the planet during the period. An article reporting their findings is published in Proceedings of the National Academy of Sciences of the United States of America (PNAS).
According to the literature, several lineages of eukaryotes that first emerged 1.5 billion years ago diversified and established themselves during the Neoproterozoic oxygenation event (850-540 mya), when oxygen levels in the atmosphere and oceans rose significantly owing to changes in the planet’s geochemistry.
Eukaryotes are organisms consisting of one or more cells in which the DNA is contained within a distinct nucleus (all life on Earth except bacteria and archaea).
The study conducted by the researchers focused on the origin and divergence times of amoebozoans, showing that many of these organisms, as well as ancestors of plants, algae, fungi and animals, survived even the two glaciations of the Cryogenian period (790-635 mya, the middle Neoproterozoic Era, preceded by the Tonian and followed by the Ediacaran). According to the snowball earth hypothesis, polar ice extended to cover the entire planet for some 100 million years during this period.
“The classical paradigm for the Neoproterozoic was that there was practically no life on the planet apart from one or two species of bacteria and protists. In the last 15 years, however, fossils of unicellular, eukaryotic and heterotrophic organisms have been identified at various different locations around the world. These fossils date from about 800 mya [and are termed Tonian]. All this joined our study, which reconstituted the tree of life and used maximum likelihood estimation to identify several well-established Tonian lineages of ancestors of amoebae, animals, fungi and plants. This radically changes the paradigm for the manner in which the diversification of life occurred on our planet,” Daniel Lahr, last author of the article and a professor at the University of São Paulo’s Institute of Biosciences (IB-USP), told Agência FAPESP.
In other words, the study dates the mass diversification of life on Earth to some 260 million years earlier than the paradigm, well before the Cambrian explosion (the emergence of new multicellular organisms at the beginning of the Cambrian period between 541 and 530 mya). During this period, the Earth was inhabited mostly by marine invertebrates such as trilobites, brachiopods and graptolites, and had a warm and humid climate with no evidence of glaciers.
“The eukaryotes remained highly diverse despite all the climate changes that occurred during the Neoproterozoic, displaying greater adaptability than expected. This is important because our reconstitution of the phylogenetic tree also serves as a basis for paleoclimate reconstruction research,” Lahr explained.
“A curious aspect is that Arcellinid amoebae then lived in saltwater, whereas now they all live in freshwater. This kind of change is frequently observed in the course of evolution since time began, but it happened to all lineages in the case of these amoebae, showing once again how adaptable these organisms were.” (MORE - details, no ads)