Chapter 25: History of Life
Chapter 25: History of Life BYS 120
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This 6 page Class Notes was uploaded by Amelia Notetaker on Tuesday December 1, 2015. The Class Notes belongs to BYS 120 at University of Alabama - Huntsville taught by Dr. Luciano Matzkin in Fall 2015. Since its upload, it has received 18 views. For similar materials see Organismal Biology in Biological Sciences at University of Alabama - Huntsville.
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Date Created: 12/01/15
Chapter 25 Notes Early Earth o Solar system in 4.6 billion years old o Earth was on full about 3.6 billion years ago. Continuously bombarded. o Earth's early atmosphere was very different Water vapor and chemicals, released by volcanic eruptions Molecules from space o Murchison meteorite (4.5 billion years old) o Contained large amount of amino acids o Recently even nucleotides have been found in meteorites Common pathway involved the formation of nucleotides, amino acids, and lipids o Chemistry associated with hydrogen cyanide, associated with UV rays being able to produce chemistry seem in life Abiotic synthesis of macromolecules o RNA monomers can be produced spontaneously from simple molecules o These monomers can then polymerize when they are concentrated on hot sand, clay, or rock Protocells o Membrane structures that can isolate its contents from external environments o AKA vesicles; can be simple produced by mixing lipids and water o Stability of vesicles can be greatly enhanced by volcanically derived clays o Under certain conditions can grow and divide o Not living o Can be selectively permeable o Uptake RNA Self-replicating molecules o RNA was likely the 1st genetic material Can perform catalytic functions Self replicating o Not very stable Early life o Early self-replicating molecules (RNA) that found themselves sheltered inside protocells were more likely to make more copies of itself (higher fitness) o Early-life was RNA based Fossil record o Fossilized remains of earlier life allow history of extinct and extant species o Some organisms are more likely to have fossil remains Abundant Hard bony parts (skeleton armor) o More fossils found daily to help us further understand the historical record Dating fossils o Different sedimentary layers allow us to date fossils, or rock layers using the half-life of isotopes o A half-life is the amount of time it takes for half the isotope to decay o Different isotopes have different half-lives Different "clock speeds" o C14/N14 5,730 HL 100,500,000 years K40/Ar40 1,360,000 100,000-4.5 billion HL years Rb87/Sr87 47 billion HL 10 million-4.5 billion years Ur238/Pb20 4.5 billion 10 million-4.5 billion 6 HL years Ur235/Pb20 710 million 10 million-4.5 billion 7 HL years Why do some believe RNA was the first genetic material and not DNA? o RNA has storage and catalytic properties Brief history of life o Archean: 4.6 million years o Proterozoic: 2.5 million years o Phanerozoic: Cenozoic: 65.5 million years Mesozoic: 251 million years Paleozoic: 542 million years o Earliest fossils date about 3.5 billion years Stromatolites Early prokaryotes o Most atmospheric O2 is of biological origin o O2 produced by oxygenic photosynthesis o By about 2.7 billion years ago, O2 revolution began o Cyanobacteria Photosynthetic o The O2 increase from 2.7-2.3 billion years ago, caused the extinction of many prokaryotes Multicellularity o Allowed for more complex structures and diversification o Evolved 1.5 billion years ago o Extreme galciation confided life to the equatorial region or deep sea vents from 750-580 million years ago o Many formed soft bodies organisms that living from 575-535 million years ago Cambian explosion o 535-525 million years ago o The beginning is marked by sudden appearance of fossils resembling modern animals o Few animal phyla appear even earlier, sponges, crusteanians, and molluscs o Cambian explosion provides the first evidence of predator-prey interactions Evolution of bony teeth and bony structures o DNA analysis suggests before the cambian explosion many animal phyla emerged, perhaps as earlier as 700 million to 1 billion years ago Shifts to terrestrial life o Fungi, plants, and animals began to colonize land about 500 million years ago o Vascular plant tissue transport materials internally and help stand tall o Anthropods and tetrapods are most widespread and diverse land animals Evolved from lobed fish Theory of plate tectonics o Earth's crust is comprised of plates floating on the earth's mantle o Tectonic plates move slowly through the process of continental drift o Oceanic and continental plates can collide, separate, and cut gene flow o Shape and location of continents has dramatically changed Affected species and evolution Mass extinctions o Great majority of all species that have once lived on earth are not alive o Extinction can be caused by changes in a species' environment o Mass extinction: where the rate of extinction increased dramatically o Mass extinction is a result of global disruption 5 major mass extinctions o In each mass extinction, 50% of species become extinct Permian extinction o Largest extinction, 251 million years ago o 90% of all marine life gone o Caused by extremely high volcanic activity that increased the earth's temperature Increased by 6 degrees C Ocean anoxied Cretaceous extinction o 65.2 million years ago o Almost all the dinosaurs died o Likely caused by large ateroid 10 km in diameter Extinctions today o Current rate is higher than background rate o Extinction is positively associated with global temperature Consequences of mass extinctions o Change ecological roles and the niches available to organisms o Long recovery time (50 to 100 million years) o Adaptive radiation: occur when large number of species evolve in relative short period of timee Following mass extinction Colonization events Evolution of key innovators Evolution and development o Examining the mechanisms of developmental change can also shed light onto evolutionary change o Developmental genes control rate, timing, etc o Tremendous increase in diversity during the cambrian explosion o Developmental genes may have played an especially important role o These genes shared among large taxonomic genes Developmental genes o Some genes are expressed in select tissues and regulate the expression of other genes o Control development and placement of body parts o These control genes are called homeotic genes Hox genes o Class of homeotic genes that provide positional info during development o Hox genes are expressed in wrong location, body parts can be produced in wrong location Changes at developmental genes o New morphological forms can come from changes in gene expression/development Gene duplication Coding sequence Changes in expression EX: changes in gene expression o 3 spine stickleback Have fewer spines than relatives Evolution of Pitx1 o The 238 amino acids of Pitx1 protein are identical o Pitx1 is differently expressed o Changes in where genes get turned on or off Evolutionary novelties o How do complex traits arise? One step at a time Evolutionary trends o Evolutionary change isn't directed, although sometimes, appears that way o Traits are more complicated and many offspring go extinct until favored hybrids become favored
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