Precambrian to Cambrian
The Precambrian-Cambrian Boundary
In the history of the Earth geologists study events in the geologic time scale and fossil record to gain an understanding of the structural and biological history of our planet. One of the debated and studied areas of Earth’s history is the sudden occurrence of multicellular hard-shelled organisms from soft bodied and single celled organisms in the Precambrian-Cambrian boundary.
The debut of hard parts in the fossil record is believed to have occurred 570 million years ago with common species in the fossil record like the Trilobite. The controversy that comes from the rise of hard parts in the fossil record is how abrupt the change is. In the Precambrian fossil record it is dominated by Stromatolites which contain prokaryotic microbiotas which are important for placing single-celled organisms in the Precambrian to mark out when they become less common(Morris 1987). It is difficult to find evidence in the fossil record for the transition from Prokaryote cells to Eukaryote cells but it is thought to have occurred 1.3billion years ago(Morris 1987). Single celled organisms debut 3.5billion years ago(Kerr 1993). Soft bodied fossils like the Ediacaran faunas (620-700million years ago) had a wide distribution which is believed to be resulting from a lack of scavengers in this time period(Morris 1987). Another belief for the appearance of hard-parts is that the changing seawater chemistry had diverse affects on the inhabiting organisms of the area. Another theory is that organisms had to be small and simple as not enough oxygen for multicellular organisms. Whereas others say animals simplicity of not having physiological and anatomical complexity meant they couldn’t expand into empty ecological niches(Kerr 1993). Trace fossils are also found in both stratigraphical areas. Trace fossils found show the behaviour of feeding, excavation of living space and movement. The pattern of diversification mirrors the adaptive radiations of the
In the history of the Earth geologists study events in the geologic time scale and fossil record to gain an understanding of the structural and biological history of our planet. One of the debated and studied areas of Earth’s history is the sudden occurrence of multicellular hard-shelled organisms from soft bodied and single celled organisms in the Precambrian-Cambrian boundary.
The debut of hard parts in the fossil record is believed to have occurred 570 million years ago with common species in the fossil record like the Trilobite. The controversy that comes from the rise of hard parts in the fossil record is how abrupt the change is. In the Precambrian fossil record it is dominated by Stromatolites which contain prokaryotic microbiotas which are important for placing single-celled organisms in the Precambrian to mark out when they become less common(Morris 1987). It is difficult to find evidence in the fossil record for the transition from Prokaryote cells to Eukaryote cells but it is thought to have occurred 1.3billion years ago(Morris 1987). Single celled organisms debut 3.5billion years ago(Kerr 1993). Soft bodied fossils like the Ediacaran faunas (620-700million years ago) had a wide distribution which is believed to be resulting from a lack of scavengers in this time period(Morris 1987). Another belief for the appearance of hard-parts is that the changing seawater chemistry had diverse affects on the inhabiting organisms of the area. Another theory is that organisms had to be small and simple as not enough oxygen for multicellular organisms. Whereas others say animals simplicity of not having physiological and anatomical complexity meant they couldn’t expand into empty ecological niches(Kerr 1993). Trace fossils are also found in both stratigraphical areas. Trace fossils found show the behaviour of feeding, excavation of living space and movement. The pattern of diversification mirrors the adaptive radiations of the