Biology Macroevolution Notes
Biology Macroevolution Notes Bio 141
U of S
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This 3 page Class Notes was uploaded by Heather Glovach on Tuesday September 13, 2016. The Class Notes belongs to Bio 141 at University of Scranton taught by Dr. Marc Seid in Fall 2016. Since its upload, it has received 2 views. For similar materials see General Biology in Biology at University of Scranton.
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Date Created: 09/13/16
Macroevolution Chapter 25 Macroevolutionary The fossil record shows major changes over large time scales: o Oxygen o The emergence of terrestrial vertebrates o The impact of mass extinctions o The origin of flight in birds Conditions on Early Earth Made the Origin of Life Possible Chemical and physical processed may produce very simple cells through the sequence of stages: o Abiotic synthesis of small organic molecules o Joining of these small molecules into macromolecules o Packaging of molecules into protocells o Origin of selfreplicating molecules Organic Compounds on Early Earth Earth Formed about 4.6 billion years ago, along with the rest of the solar system Bombardment of Earth by rocks and ice likely vaporized water and prevented seas from forming before 4.2 to 3.9 billion years ago Earth’s early atmosphere likely contained water vapor and chemicals released by volcanic eruptions (nitrogen. Nitrogen oxides, carbon dioxide, methane, ammonia, hydrogen, hydrogen sulfide) Abiotic Synthesis of Small Organic Molecules In the 1920s, A. I. Oparin and J. B. S. Haldane hypothesized that the early atmosphere was a reducing environment In 1953, Stanley Millerand Harold Urey conducted lab experiments that showed that the abiotic synthesis of organic molecules in a reducing atmosphere is possible MillerUrey type experiments demonstrate that organic molecules could have formed with various possible atmospheres o the first organic compounds may have been synthesized near volcanoes or deep sea vents Amino acids have also been found in meteorites o Lisomers vs Disomers o Lipids, simple sugars, nitrogenous bases Abiotic Synthesis of Macromolecules RNA and amino acid monomers have been produced spontaneously o Hot sand, clay, rock These simple molecular could have acted as weak catalyst Protocells Replication and metabolism are key properties of life Protocells – are fluid filled vesicles with a membrane like o Lipids/other organic molecules can spontaneously form vesicles with a lipid bilayer Adding clay can increase the rate of vesicle formation Vesicles exhibit simple reproduction and metabolism and maintain an internal chemical environment SelfReplicating RNA and the Dawn of Natural Selection The first genetic material was probably RNA, not DNA RNA molecules called ribozymes have been found to catalyze many different reactions o For example, ribozymes can make complementary copies of short stretches of RNA Natural selection has produced selfreplicating RNA o RNA molecules that were more stable or replicated more quickly would have left the most descendent RNA molecules First Protocells Vesicles with RNA capable of replication Major boundaries between geological divisions correspond to extinction events in the fossil record The First SingleCelled Organisms Oldest known fossils are stromatolites o Sedimentary layers on bacterial mats Stromatolites date back 3.5 billion years ago Prokaryotes were Earth’s sole inhabitants from 3.5 to about 2.1 billion years ago Cells More prokaryote cells than eukaryote cells in the human body Photosynthesis and the Oxygen Revolution Most atmospheric oxygen (O2) is of biological origin O2produced by oxygenic photosynthesis reacted with dissolved iron and precipitated out to form banded iron formations Poisoning the Atmosphere By about 2.7 billion years ago, o O2 began accumulating in the atmosphere o rusting ironrich terrestrial rocks This “oxygen revolution” from 2.7 to 2.3 billion years ago caused the extinction of many prokaryotic groups Cyanobacteria –Likely cause O2 A later increase in the rise of O2might have been caused by the evolution of eukaryotic cells containing chloroplasts The First Eukaryotes Date back 2.1 billion years Prokaryotes have a circular membrane shape Eukaryotes have an elongated shape Eukaryotic cells have a nuclear envelope, mitochondria, endoplasmic reticulum, and a cytoskeleton Endosymbiont theory o Proposes that mitochondria and plastids (chloroplasts and related organelles) were formerly small prokaryotes living within larger host cells An endosymbiont is a cell that lives within a host cell Key evidence supporting an endosymbiotic origin of mitochondria and plastids: o Inner membranes are similar to plasma membranes of prokaryotes o Division is similar in these organelles and some prokaryotes o These organelles transcribe and translate their own DNA o Their ribosomes are more similar to prokaryotic than eukaryotic ribosomes The Origin Multicellularity The evolution of eukaryotic cells allowed for a greater range of unicellular forms A second wave of diversification occurred when multicellularity evolved and gave rise to algae, plants, fungi, and animals The Earliest Multicellular Eukaryotes Comparisons of DNA sequences date the common ancestor of multicellular eukaryotes to 1.5 billion years ago The oldest known fossils of multicellular eukaryotes are of small algae that lived about 1.2 billion years ago The Cambrian Explosion The Cambrian explosion refers to the sudden appearance of fossils resembling modern animal phyla in the Cambrian period (535 to 525 million years ago) A few animal phyla appear even earlier: sponges, cnidarians, and mollusks The Cambrian explosion provides the first evidence of predatorprey interactions
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