Lecture 2 OutlineBio 200Those Eras above fall under the Proterozoic Eon.Lecture 2 OutlineBio 200Protoplanentary Disk- Before the formation of the solar system, there existed a large rotating cloud of dust, rocks, and gas. Composed of hydrogen, and helium (produced in the big bang), and also other heavier elements ejected by supernovas. Before Solar system.Formation of the Sun- 4.6 billion years ago, a star close to the protoplanetary disk was destroyed in a super-nova; the explosion sent a shockwave through the disk. As the cloud from the shockwave began to speed up, most of the mass in the disk was concentrated in themiddle and it started to heat up. An enormous amount of heat in the center of the pre-solar system had lead to the nuclear fusion of hydrogen into helium. This eventually led to the formation of the sun.Protoplanet- Perturbations (a disturbance of motion, course, arrangement, or state of equilibrium) caused by matter and other things remained in the disk and it allowed protoplanets to form. As gravity caused matter to condense around the previously perturbed object outside of the new sun’s gravity grasp, the rest of the protoplanetary area began to separate into rings. Successfully larger fragments collided with one another and became larger objects, which then began planets. This included one protoplantet, approx. 150 kilometers from the sun, which is Earth. Earth formed about 4.57 billion years ago. The planet was completed within 10-20 million years. It took several millions years before life could evolve (3.8 billion years ago).Hadean Eon- Lasted almost 800 million years. During the earliest parts of the Hadean= no oceans and no free oxygen in the atmosphere. Earth was filled with planetoids and other material that was left over from the formation of the solar system. This bombarded with residual heat, caused the planet to be fully molten. Earth’s atmosphere would be filled with material from the solar nebular (gaseous cloud), especially light gasses such as hydrogen and helium. The solar wind and earth’s own heat would have driven off the atmosphere. No protective atmosphere. Hadean means hell in Greek. At the end of the Hadean, the earth’s surface cooled quickly, forming a solid crust within 150 years. 4-3.8 billion years ago, Earth underwent heavy astroidal bombardment, causing cracks in the new surface. Steam escapedfrom the cracks, and volcanoes released additional gasses. The steam and gasses combined, allowing formation of a reducing atmosphere(electron adding, molecules formed very readily). The planet continued to cool, clouds formed in the atmosphere= rain gave rise to the oceans. The atmosphere probably contained ammonium, methane, water vapor, carbon dioxide, and nitrogen and smaller amounts of other gasses, but still no free oxygen. Volcanicactivity was still intense and ultra violet radiation without an ozone layer would have flooded the earths surface= bad. That adds a ton of energy to the system. Conditions on earth were getting somewhat better, but still not good for life.Oceans formed once earth cooled at the END of the eon. First life appeared was anaerobic (no oxygen) (3.8 MYA) Since the earth’s crust was molten, we can assume that all early life 3.8 BYA was aquatic. Stamatolites/cyanobacteria were the reason why photosynthesis occurs. Strata- Layers of undisturbed sedimentary rocks. Older layers will lie at the bottom, and the higher strata will be successfully younger.1Radioactive Isotopes- Carbon Dating, the ratio of Carbon 14 to Carbon 12 is not really reliably dated around 50k years, because so little Carbon 14 would be left. Therefore, different isotopes are used to date different rocks. Used in dating of rocks, estimating how much time has passed for rocks.Optical/Luminescence- Sometimes used to determine how long ago minerals would last exposed to daylight.Molecular Data- Used for looking at relationships in time of divergences between organisms. When we combine all of the previous information about physical changes with evidence from the fossil records, we can get an idea of what Earth and its habitants was like at different time periods.Precambrian (Super-eon)- 4.6 Billion years- 543 Million years ago (Lasted about 400 billion years). Occupies much of Earth’s time period. (Longest Eon)Dived into unequal three eons: - Hadean Eon (Beginning of earth), - Archean Eon (origin of life began- stromatolites. Origin of photosynthesis late Archean, early Proterozoic),- Proterozoic Eon (photosynthesis origin, colonial cyanobacteria origin, first eukaryotes, first photosynthetic eukaryotes, first multicellular eukaryotes, first fossils found of multicellular animals). The Cambrian Explosion- The beginning of the Paleozoic was great. This was because the first period, The Cambrian, scientist found ”a lot of fossils of all the major marine animal groups just during a few million years from the early to mid Cambrian. But since we have a lot of information today, we have found many Precambrian animals. The presence of Precambrian animals damages the “bang” of the “Cambrian explosion”. The appearances of 2the animals were only gradual, and the diversification during this “bang” may have been not as rapid as we once thought. Even today, through statistics, we can see that the “explosion” of new marine animals was not any faster than any other diversifications in animal history. This “bang” lasted 60 million years.Paleozoic Era- (Phanerozoic Eon) Lasted about 300 million years from 543-250 million years ago. (Longest Era) Abundance of soft-shelled fossils were found from this era. During this era, large and sophisticated reptiles, also modern plants too were found. One of the first creatures found during this era were trilobites. Also, Archeacyathids (sponge-like animals) were found. About 450 million years ago, the first land plants (450 MYA) (ie: carpet moss) appear. Previous to that point, all life occurred in water. Later in the Paleozoic, about 420 million years ago, fish evolve legs and start to walk on legs. Later in the era, successful amphibians dominate it. First land animals (420 MYA) and land plants. (450 MYA) Make a timline*Permian Extinction- AKA “The great dying”. Up to 96% of marine life and up to 70% of terrestrial (on land) vertebrates went extinct. The only known mass extinction of insects=bad. The worst mass extinction in Earth’s history. With the extinction, it dramatically
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