The Precambrian era envelopes the major bulk of the history of the Earth, beginning from the creation of the planet approx 4.5 billion years ago and terminating with the origination of composite, multicelled forms of life approximately 4 billion years after.
The Precambrian refers to the earliest of the geologic ages that are signified by the distinct layers of sedimentary rock. The Earth was about more than six hundred million years old when life started. The planet had cooled down from its native molten state, creating a solid crust and oceans formed by water vapor in the atmosphere.
At about three billion years ago, the atmosphere of the Earth was virtually devoid of oxygen. At approximately 2.4 billion years ago, oxygen was discharged from the seas as a waste product of photosynthesis by cyanobacteria. The levels of the gas slowly raised, attaining about 1 percent around two billion years ago.
Approximately 800 million years ago, the levels of oxygen attained about 21 percent and started to breathe life into more composite species. The oxygen-rich ozone layer was also created, protecting the surface of the Earth from the harmful solar radiation.
The x-axis shows the relative
amount of DNA per cell thought not directly. This can be seen through a
histogram a specific type of a graph. Looking at the bars of the histogram you
can follow peaks and dips which correspond to something like fluorescence which
indirectly shows the relative amount of DNA in cell.
The deep sea vent organisms or benthic organisms normally live in dark conditions because of no penetration of sunlight. These organisms in order to colonize ocean surface must develop photo sensory receptors and should adapt to the light conditions along with variation in temperatures and pressure in ocean currents.
Answer:
Ammonites, , Brachiopod, Grapolithina, Trilobites and Nanofossils are examples of index fossils
Explanation:
Ammonites were common during the Mesozoic Era (245 to 65 mya), but were not found after the Cretaceous period. They went extinct during the K-T extinction (65 mya)
Brachiopods which are mollusk-like marine animals appeared during the Cambrian (540 to 500 mya). Some types of them still survive
Grapolithina which are widespread colonial marine hemichordates that also lived during the Cambrian period.
Nanofossils are microscopic fossils which are remains of calcareous nannoplankton, coccolithophores from various eras
Trilobites were common during the Paleozoic Era (540 to 245 mya); about half of the Paleozoic fossils are Trilobites. Trilobites evolved at the beginning of the Paleozoic Era and went extinct somewhere in the late Permian period which was 248 million years ago
This might be extra information but i hope it helps
