DE (W9)

• Microorganisms or microbes are single-celled organisms that need water to live and reproduce
• Microorganisms can live at least 5km beneath Earth’s surface and 10km into the atmosphere
• biofilms are dense concentrations of microorganisms that coat surfaces
• the genetic differences between the three branches of microorganisms is greater than the differences between plants and animals as we all came from the same universal ancestor
• a single root of the universal tree is called the universal ancestor. there are three major domains including: Bacteria, Archaea and Eukarya
• Bacteria and Archaea evolved first and all their descendants remain single-celled microorganisms
• Eukarya have more complex cellular structures which include a cell nucleus containing genes
• microfossils are traces of individual microorganisms perserved in rocks
• Extremophiles are microorganisms that live in extreme environments that would kill most life
• Acidophiles thrive in acidic environments by eating sulfide
• Thermophiles live and grow in extremely hot environments (best between 50-70 degrees) with Archaea being the most tolerant
• Halophiles live and grow in highly saline environments
• Anaerobes live in environments devoid of oxygen
• the aerobic zone is the upper oxygen-rich sediment layer above the oxygen free anaerobic zone below
• Microorganisms precipitate minerals indirectly through the composition of water surrounding them and directly in their cells as a result of metabolism
• during Indirect precipitation minerals in an oversaturated solution precipitate on the surfaces of individual microorganisms, often encasing/ burying them alive
• all organisms need oxygen however in oxygen devoid environments some have adapted to obtain it from other sources such from sulfate (SO4)
• chemoautotrophs are microorganisms that derive their energy from chemicals produced when minerals dissolve and not from sunlight
• stromatolites are rocks with distinctive thin layers and are believed to have been formed from ancient microbial mats
• microfossils can be found in rocks 3.5 billion years old, but multicellular organisms only appear in rocks younger than 1 billion years
• the theory of evolution predicts that the first organisms and all life that came after evolved from a universal ancestor
• the universal ancestor would likely have had to have genetic information and composed of carbon-rich compounds
• well-preserved fossils are only found in sedimentary rocks that have not been significantly affected by metamorphism or deformation
• amino acids were also discovered on a meteorite showing that they can form on a planet without oxygen
• early experiments designed to recreate earth’s early composition yielded compounds called amino acids that are fundamental building blocks of life
• the earliest form of life is believed to have likely been chemoautotrophic and hyperthermophilic meaning it could have originated in very hot water where sunlight was unavailable as an energy source but chemicals weren’t
• chemofossils are chemical remains of organic compounds made by ancient microorganisms while they were alive
• mass extinctions are intervals where many groups of organisms become extinct at the same time
• evolutionary radiation is the rapid development of new types of organisms from a common ancestor
• The Cambrian explosion (biology’s big bang) was an evolutionary radiation that occurred extremely extremely fast.
• Evolution by natural selection states that over generations, individuals with the most favourable traits are most likely to survive and reproduce. If environmental conditions change over time, the traits that are favoured change as well.
• Shell and skeleton development was likely critical in allowing diversification
• The Cretaceous-tertiary extinction and the end of the Mesozoic era 65 million years ago eliminated 75% of all species on Earth.
• The Cretaceous-tertiary extinction is now almost certainly believed to have been caused by an asteroid, due to the presence of iridium-bearing dust found world over at the Cretaceous-Tertiary boundary.
• The Paleocene-Eocene boundary mass extinction 55 million years ago paved the way for the rise of mammals and was caused by abrupt global warming due to the methane being suddenly released from the ocean in enormous quanities.
• The largest mass extinction marked the end of the Permian and the start of the Paleozoic era where 95% of all species became extinct exactly 251 million years ago.
• the cause of the largest mass extinction is unknown but potentially the result of volcanic eruptions