Throughout this period, however, fossils of the cyanobacteria mats are also referred to as the stromatolites that are said to have been instrumental in creating the free oxygen we have today existed. Other than that, this period had biogenic graphite that was found in several metasedimentary rocks in Western Greenland aged 3700 Ma. Apart from this, fossil records show that sandstone was later discovered to have microbial mat fossils in Western Australia dated 3480 million years ago. Other chert beds contain bacterial fossils making this period one that contributed a lot to the evolution of living things from simple organisms to more complex life forms.

Task 2

Climate is one of the many factors that make life on earth possible. Within millions of years, the temperatures of the planet have changed to fit bounds that are life-sustaining. The icehouse interval is characterized by three major glaciations in the Phanerozoic Eon. The first one is the Late Ordovician that occurred about 430 million years ago, the second one is the Permo Carboniferous period, whose period spanned 325-240 million years ago, and lastly, the Late Tertiary, which started about 35 million years ago and up to now (Koeberl 2009). The icehouse is controlled by several factors, rather hypotheses that try to explain what holds the icehouse. One of them focuses on the position of the pole, in which case it argues that there cannot be any ice sheet formed on continents when they are near the equator and that the same can only be formed near poles. The cold temperatures during the three intervals above resulted from low sea levels, less photosynthetic activity, low levels of carbon dioxide in the atmosphere, and less volcanic activity in the oceans (Fischer 1986). There are several essential factors that scientists have agreed on as having been influential during the icehouse period. These controlling factors are secular, which means that they are internal to the earth, or cyclic, external to the planet (astronomical, that is).&nbsp.

Task 3

The Ediacaran period spanned between ca. 635 to 542 Ma. Fossils from this period have been found from all over the world and are mainly of multicellular organisms. However, the microorganisms, which are said to comprise a group of the Late Precambrian fossils, were first found near the Ediacaran Hills of Australia (the place where they got their name from). The Ediacaran organisms resemble the invertebrates such as the arthropods, worms, echinoderms, or the cnidarians.