Why is finding evidence of life during the Hadean eon so difficult?Group of answer choicesRocks that old are difficult to find as they tend to be destroyed over billions of yearsLife that old is difficult to find because organisms do not live billions of yearsRocks that old are difficult to find without digging much deeper undergroundLife that old is difficult to find because most organisms during that eon lived in the ocean

What name is given to the remains of organisms that lived many years ago, found in rocks?

1 In 1970 geologists Kenneth J. Hsu and William B. F. Ryan were collectingresearch data while aboard the oceanographic research vessel Glomar Challenger. Anobjective of this particular cruise was to investigate the floor of the Mediterranean andto resolve questions about its geologic history. One question was related to evidencethat the invertebrate fauna (animals without spines) of the Mediterranean had changedabruptly about 6 million years ago. Most of the older organisms were nearly wipedout, although a few hardy species survived. A few managed to migrate into theAtlantic. Somewhat later, the migrants returned, bringing new species with them. Whydid the near extinction and migrations occur?2 Another task for the Glomar Challenger’s scientists was to try to determine theorigin of the domelike masses buried deep beneath the Mediterranean seafloor. Thesestructures had been detected years earlier by echo-sounding instruments, but they hadnever been penetrated in the course of drilling. Were they salt domes such as arecommon along the United States Gulf Coast, and if so, why should there have been somuch solid crystalline salt beneath the floor of the Mediterranean?3 With questions such as these clearly before them, the scientists aboard the GlomarChallenger proceeded to the Mediterranean to search for the answers. On August 23,1970, they recovered a sample. The sample consisted of pebbles of hardened sedimentthat had once been soft, deep-sea mud, as well as granules of gypsum1 and fragmentsof volcanic rock. Not a single pebble was found that might have indicated that thepebbles came from the nearby continent. In the days following, samples of solidgypsum were repeatedly brought on deck as drilling operations penetrated theseafloor. Furthermore, the gypsum was found to possess peculiarities of compositionand structure that suggested it had formed on desert flats. Sediment above and belowthe gypsum layer contained tiny marine fossils, indicating open ocean conditions. Asthey drilled into the central and deepest part of the Mediterranean basin, the scientiststook solid, shiny, crystalline salt from the core barrel. Interbedded with the salt werethin layers of what appeared to be windblown silt.4 The time had come to formulate a hypothesis. The investigators theorized thatabout 20 million years ago, the Mediterranean was a broad seaway linked to theAtlantic by two narrow straits. Crustal movements closed the straits, and thelandlocked Mediterranean began to evaporate. Increasing salinity caused by theevaporation resulted in the extermination of scores of invertebrate species. Only a fewEnglish DepartmentModel English TOC Exam- 2023English Time: 3 hours.5organisms especially tolerant of very salty conditions remained. As evaporationcontinued, the remaining brine (salt water) became so dense that the calcium sulfate ofthe hard layer was precipitated. In the central deeper part of the basin, the last of thebrine evaporated to precipitate more soluble sodium chloride (salt). Later, under theweight of overlying sediments, this salt flowed plastically upward to form salt domes.Before this happened, however, the Mediterranean was a vast desert 3,000 metersdeep. Then, about 5.5 million years ago came the deluge. As a result of crustaladjustments and faulting, the Strait of Gibraltar, where the Mediterranean nowconnects to the Atlantic, opened, and water cascaded spectacularly back into theMediterranean. Turbulent waters tore into the hardened salt flats, broke them up, andground them into the pebbles observed in the first sample taken by the Challenger. Asthe basin was refilled, normal marine organisms returned. Soon layers of oceanic oozebegan to accumulate above the old hard layer.5 The salt and gypsum, the faunal changes, and the unusual gravel providedabundant evidence that the Mediterranean was once a desert.Questions: -1- Which of the following is NOT mentioned in paragraph 1 as a change thatoccurred in the fauna of the Mediterranean?A. Most invertebrate species disappeared during a wave of extinctions.B. A few hardy species wiped out many of the Mediterranean’s invertebrates.C. Some invertebrates migrated to the Atlantic Ocean.D. New species of fauna populated the Mediterranean when the old migrantsreturned.

Palaeontologists have a very hard time classifying the Ediacaran fossils. Propose why it is such a challenge. They didn't have hard body parts.1They look like nothing alive today.2They are just impressions in the rock.3They are very small, no require microscopes to be studied.

Why is it challenging to study bacterial fossils and determine if the fossils are members of the domain Archaea rather than Bacteria?

By examining fossils, paleontologists cannot tell how long ago organisms lived.TrueFalse