1a) Stromatolites dominated most of Earths biological history from >3.5Ga to abo

Question

1a) Stromatolites dominated most of Earths biological history from >3.5Ga to about 600 Ma (the Precambrian). What effect might the apperence of Gastropods at the begining of the Phanerozoic have had on stromatolites?
1b) stromatolites and gastropods still exist today. In what types of environments would you expect to find stromatolites today, given the widespread presence of snails in wet habitat?
1c) Think about the organisms (Cyanobacteria) that form a stromatolites and the nature of the preserved structure. Is a stromatolites
A. Body fossil B. A trace fossil C. Neither body or trace fossil 1a) Stromatolites dominated most of Earths biological history from >3.5Ga to about 600 Ma (the Precambrian). What effect might the apperence of Gastropods at the begining of the Phanerozoic have had on stromatolites?
1b) stromatolites and gastropods still exist today. In what types of environments would you expect to find stromatolites today, given the widespread presence of snails in wet habitat?
1c) Think about the organisms (Cyanobacteria) that form a stromatolites and the nature of the preserved structure. Is a stromatolites
A. Body fossil B. A trace fossil C. Neither body or trace fossil
1b) stromatolites and gastropods still exist today. In what types of environments would you expect to find stromatolites today, given the widespread presence of snails in wet habitat?
1c) Think about the organisms (Cyanobacteria) that form a stromatolites and the nature of the preserved structure. Is a stromatolites
A. Body fossil B. A trace fossil C. Neither body or trace fossil

Explanation / Answer

1a) It is thought that the declination of stromatolites was caused by the appearance of algae-grazing organisms such as gastropods. It is believed the decline may have resulted from the increases in nutrient levels in the oceans with the rise of the Metazoans in the Cambrian explosion ago that ushered in the modern type animals including grazing marine invertebrates about 600 Ma. Grazing metazoan began to use stromatolite-forming microbial mats as a food resource.

1b) The environments suitable for their survival depend upon several factors. Being photosynthetic cyanobacteria require the water to be shallow enough to reach the bottom of the water column and they require water currents that bring the right amount of silt so they cement the silt with the limestone they extract from the water, without being smothered by the silt. They can build a habitat in the place of high salinity or high temperature which is non-suitable for grazing gastropod. They live today in a wide range of environments ranging from the shallow shelf to lakes, rivers, and even soils.

1c) Answer: C. Neither body or trace fossil.

Stromatolite is a sedimentary feature formed by sediment layer deposit on cynobacteria and preservation of those as sedimentary layers. Thus, it is not body fossil. Trace fossil implies activity or behavior of some organism and stromatolite doesn’t relate to any sorts of activity or behavioral characteristic.

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