More past questions Flashcards
Ediacaran vs Cambrian
Ediacaran animals were sessile (slow moving) and soft-bodied while Cambrian animals had hard exoskeletons or hard parts and were moving.
Explain how the biosphere has influenced Earth’s atmosphere and hydrosphere over time
Photosynthetic organisms = water = dissolved in water = no oxygen in atmosphere
oxygen in water + dissolved iron = iron oxides which precipitated to form layers
too much oxygen, excess oxygen escaped into atmosphere = ozone layer
evolution of terrestrial plants and plants in hydrosphere = more oxygen
decrease in co2 because terrestrial plants consume it as a reactant in psynthsis
The average abundance of iridium in meteorites is 0.5 ppm and the average abundance of iridium in general crustal rocks is less than 0.001ppm. How can the iridium content of BOTH meteorites and Earth’s crust be used to support the theory that the end-Cretaceous mass extinction was caused by a meteorite impact?
The end Cretaceous mass extinction occurred at the boundary between the Cretaceous and the Paleogene. It resulted in the disappearance of numerous organisms including all the dinosaurs. To support the theory that a meteor caused the extinction, the following criteria must be met:
The impact resulted in the disintegration of the meteor causing widespread distribution of the dust and particles from the meteor
The dust and particles of the meteor had to become part of the sediments at the time of impact.
Since meteors have much higher iridium content, 0.05ppm in this case, than normal terrestrial rocks, in this case <0.001ppm, the sedimentary rocks deposited at the boundary should have a higher iridium content, that is, greater than 0.001ppm due to the contamination of iridium from the meteor.
Describe the use of index fossils in the development of a Geologic time scale.
Wide geological distribution and appear for a short period of time in the fossil record. For this reason, they are useful in assisting geologists to generate the divisions of the geologic time scale as they indicate widespread environmental changes at their appearance in the fossil record.
Explain 2 factors which allowed animals to move from an aquatic environment onto land.
Increasing oxygen levels in the atmosphere led to the formation of the ozone layer that in turn reduced UV radiation levels making it possible for life forms, including animals, to conquer the terrestrial environment.
The development of a hard outer shell retained water, enabling animals to spend time on land without drying out.
Question 30: Using an example, explain a change in the geosphere that resulted from a development of the biosphere.
Fossil evidence suggests that ~3.8bya, stromatolites were abundant in many shallow seas. These stromatolites contain cyanobacteria, which has the capacity to use CO2 in a photosynthetic process to release oxygen gas into the water.
The oxygen released into the water initially reacted with the dissolved iron in Earth’s ancient oceans, precipitating to form iron oxides which settled on the bottom of the ocean floor, producing an iron oxide band in the strata. This continued through the Archean and early Proterozic, and alternating layers of iron oxide rich and silica rich sediments produced what is known as Banded Iron Formations.
Hence, the release of oxygen from cyanobacteria in the biosphere resulted in the production of millions of tons of BIFs in the geosphere.
Impact of PTSC convergence on evolution
Prior to the continents joining, the organisms on either continent would have evolved separately, as they would have been physically separated. However, once the landmasses joined, species from one continent could now migrate to the other continent, resulting in predation competition or interbreeding, which would impact the evolution of life on earth.
Explain how 2 conditions present at ‘Black Smokers’ may have resulted in the origin of organic molecules.
Chemicals are leached from the rocks around the ‘Black Smokers’ as water percolates through the hot rocks. These chemicals could have been used to form the basic organic molecules, such as amino acids.
The superheated water from ‘Black Smokers’ (400deg) could have provided the energy required for organic-molecule-forming chemical reactions to occur in early Earth.
