In more than 4 Ga of geological evolution, the Earth has twice gone through extreme climatic perturba- tions, when extensive glaciations occurred, together with alternating warm periods which were accom- panied by atm...In more than 4 Ga of geological evolution, the Earth has twice gone through extreme climatic perturba- tions, when extensive glaciations occurred, together with alternating warm periods which were accom- panied by atmospheric oxygenation. The younger of these two episodes of climatic oscillation preceded the Cambrian ＂explosion＂ of metazoan life forms, but similar extreme climatic conditions existed between about 2.4 and 2.2 Ga. Over long time periods, changing solar luminosity and mantle temperatures have played important roles in regulating Earth＇s climate but both periods of climatic upheaval are associated with supercontinents. Enhanced weathering on the orogenically and thermally buoyed supercontinents would have stripped CO2 from the atmosphere, initiating a cooling trend that resulted in continental glaciation. Ice cover prevented weathering so that CO2 built up once more, causing collapse of the ice sheets and ushering in a warm climatic episode. This negative feedback loop provides a plausible explanation for multiple glaciations of the Early and Late Proterozoic, and their intimate association with sedimentary rocks formed in warm climates. Between each glacial cycle nutrients were flushed into world oceans, stimulating photosynthetic activity and causing oxygenation of the atmosphere. Accommodation for many ancient glacial deposits was provided by rifting but escape from the climatic cycle was predicated on break- up of the supercontinent, when flooded continental margins had a moderating influence on weathering. The geochemistry of Neoproterozoic cap carbonates carries a strong hydrothermal signal, suggesting that they precipitated from deep sea waters, overturned and spilled onto continental shelves at the termination of glaciations. Paleoproterozoic （Huronian） carbonates of the Espanola Formation were probably formed as a result of ponding and evaporation in a hydrothermally influenced, restricted rift setting. Why did metazoan evolution not take off after the Great Oxidation Event of the Paleoproterozoic？ The answer may lie in the huge scar left by the -2023 Ma Vredefort impact in South Africa, and in the worldwide organic carbon-rich deposits of the Shunga Event, arresting to the near-extirpation of life and possible radical alteration of the course of Earth history.展开更多
For purifying raw water for tap water treatment, the aquatic vegetable bed （AVB） experiment has been carded out in a hypertrophic waterfront of Taihu Lake, China. The average removal rates of total microcystin-RR an...For purifying raw water for tap water treatment, the aquatic vegetable bed （AVB） experiment has been carded out in a hypertrophic waterfront of Taihu Lake, China. The average removal rates of total microcystin-RR and microcystin-LR are 63.0% and 66. 7%, respectively. Experiments indicate that lpomoea aquatica can absorb microcystin by using enzyme-linked immunosorbent assay （ELISA）, and the roots absorb more toxins than leaves and stems. Fluorescence in situ hybridization （FISH） is used to analyze the density of microcystin degrading bacteria in the AVB sediment. Two species of microcystin degrading bacteria are detected, which indicate that microcystin bio-degradation process happened in the AVB. Protozoa and metazoa are abundant in root spheres. Aspidisca sp., Vorticella sp., Philodina sp., and Lecane sp. are dominant species. The predation functions of protozoa and metazoa have a positive effect on the removal of cyanobacteria and microcystin.展开更多
The Cambrian Explosion is one of the most significant events in the history of life;essentially all easily fossilizable animal body plans first evolved during this event. Although many theories have been proposed to e...The Cambrian Explosion is one of the most significant events in the history of life;essentially all easily fossilizable animal body plans first evolved during this event. Although many theories have been proposed to explain this event, its cause remains unresolved.Here, we propose that the elevated level of oxygen, in combination with the increased mobility and food intake of metazoans, led to increased cellular levels of reactive oxygen species（ROS）, which drove evolution by enhancing mutation rates and providing new regulatory mechanisms. Our hypothesis may provide a unified explanation for the Cambrian Explosion as it incorporates both environmental and developmental factors and is also consistent with ecological explanations for animal radiation. Future studies should focus on testing this hypothesis, and may lead to important insights into evolution.展开更多
The role of embryology in metazoan evolution is rooted deeply in the history of science.Viewing Neoplasia as an evolutionary engine provides a scientific basis for reexamining the disease cancer.Once the embryo is und...The role of embryology in metazoan evolution is rooted deeply in the history of science.Viewing Neoplasia as an evolutionary engine provides a scientific basis for reexamining the disease cancer.Once the embryo is understood as a benign tumor with a pivotal role in the evolution of all animal forms,there will be an immediate paradigm shift in the search for cancer cure,potentially revealing insights that may be buried within the great developmental transitions of metazoans.This article discusses one of the unifying principles between embryology and oncology,namely cancer stem cells.Some considerations are also provided on the central role of physics and biomechanics in the assembly of the first embryo,which can be regarded as a differentiated benign tumor.Mechanical impregnation of the nucleus of a stem cell,culminating in a totipotent/multipotent cell,was a major event safeguarding the success of embryogenesis throughout evolution.Germ cells in the earliest ctenophore embryos underwent delayed differentiation,subsequent to the mechanical assembly of the embryo.Finally,a discussion is presented on the concept that cancer and embryogenesis(cancer and healthy stem cells)are two sides of the same coin,that is,of the same process.The only difference is that cancer stem cells reveal themselves in inappropriate contexts.Neoplasia is a free force,whereas cancer is a force contained by animal organization.展开更多
基金supported by funds from the Natural Science and Engineering Council of Canada
文摘In more than 4 Ga of geological evolution, the Earth has twice gone through extreme climatic perturba- tions, when extensive glaciations occurred, together with alternating warm periods which were accom- panied by atmospheric oxygenation. The younger of these two episodes of climatic oscillation preceded the Cambrian ＂explosion＂ of metazoan life forms, but similar extreme climatic conditions existed between about 2.4 and 2.2 Ga. Over long time periods, changing solar luminosity and mantle temperatures have played important roles in regulating Earth＇s climate but both periods of climatic upheaval are associated with supercontinents. Enhanced weathering on the orogenically and thermally buoyed supercontinents would have stripped CO2 from the atmosphere, initiating a cooling trend that resulted in continental glaciation. Ice cover prevented weathering so that CO2 built up once more, causing collapse of the ice sheets and ushering in a warm climatic episode. This negative feedback loop provides a plausible explanation for multiple glaciations of the Early and Late Proterozoic, and their intimate association with sedimentary rocks formed in warm climates. Between each glacial cycle nutrients were flushed into world oceans, stimulating photosynthetic activity and causing oxygenation of the atmosphere. Accommodation for many ancient glacial deposits was provided by rifting but escape from the climatic cycle was predicated on break- up of the supercontinent, when flooded continental margins had a moderating influence on weathering. The geochemistry of Neoproterozoic cap carbonates carries a strong hydrothermal signal, suggesting that they precipitated from deep sea waters, overturned and spilled onto continental shelves at the termination of glaciations. Paleoproterozoic （Huronian） carbonates of the Espanola Formation were probably formed as a result of ponding and evaporation in a hydrothermally influenced, restricted rift setting. Why did metazoan evolution not take off after the Great Oxidation Event of the Paleoproterozoic？ The answer may lie in the huge scar left by the -2023 Ma Vredefort impact in South Africa, and in the worldwide organic carbon-rich deposits of the Shunga Event, arresting to the near-extirpation of life and possible radical alteration of the course of Earth history.
基金The National Natural Science Foundation of China(No50378014),the National High Technology Research and Develop-ment Program of China (863Program) (No2002AA601011)
文摘For purifying raw water for tap water treatment, the aquatic vegetable bed （AVB） experiment has been carded out in a hypertrophic waterfront of Taihu Lake, China. The average removal rates of total microcystin-RR and microcystin-LR are 63.0% and 66. 7%, respectively. Experiments indicate that lpomoea aquatica can absorb microcystin by using enzyme-linked immunosorbent assay （ELISA）, and the roots absorb more toxins than leaves and stems. Fluorescence in situ hybridization （FISH） is used to analyze the density of microcystin degrading bacteria in the AVB sediment. Two species of microcystin degrading bacteria are detected, which indicate that microcystin bio-degradation process happened in the AVB. Protozoa and metazoa are abundant in root spheres. Aspidisca sp., Vorticella sp., Philodina sp., and Lecane sp. are dominant species. The predation functions of protozoa and metazoa have a positive effect on the removal of cyanobacteria and microcystin.
基金supported by the Program of Co-Construction with the Beijing Municipal Commission of Education of ChinaFundamental Research Funds for the Central Universities (No. 2015KJJCB19)
文摘The Cambrian Explosion is one of the most significant events in the history of life;essentially all easily fossilizable animal body plans first evolved during this event. Although many theories have been proposed to explain this event, its cause remains unresolved.Here, we propose that the elevated level of oxygen, in combination with the increased mobility and food intake of metazoans, led to increased cellular levels of reactive oxygen species（ROS）, which drove evolution by enhancing mutation rates and providing new regulatory mechanisms. Our hypothesis may provide a unified explanation for the Cambrian Explosion as it incorporates both environmental and developmental factors and is also consistent with ecological explanations for animal radiation. Future studies should focus on testing this hypothesis, and may lead to important insights into evolution.
文摘The role of embryology in metazoan evolution is rooted deeply in the history of science.Viewing Neoplasia as an evolutionary engine provides a scientific basis for reexamining the disease cancer.Once the embryo is understood as a benign tumor with a pivotal role in the evolution of all animal forms,there will be an immediate paradigm shift in the search for cancer cure,potentially revealing insights that may be buried within the great developmental transitions of metazoans.This article discusses one of the unifying principles between embryology and oncology,namely cancer stem cells.Some considerations are also provided on the central role of physics and biomechanics in the assembly of the first embryo,which can be regarded as a differentiated benign tumor.Mechanical impregnation of the nucleus of a stem cell,culminating in a totipotent/multipotent cell,was a major event safeguarding the success of embryogenesis throughout evolution.Germ cells in the earliest ctenophore embryos underwent delayed differentiation,subsequent to the mechanical assembly of the embryo.Finally,a discussion is presented on the concept that cancer and embryogenesis(cancer and healthy stem cells)are two sides of the same coin,that is,of the same process.The only difference is that cancer stem cells reveal themselves in inappropriate contexts.Neoplasia is a free force,whereas cancer is a force contained by animal organization.
