Biology Lecture 5 - Exam 1
Biology Lecture 5 - Exam 1 BIO 121 A
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This 4 page Class Notes was uploaded by Devin Mart on Tuesday March 29, 2016. The Class Notes belongs to BIO 121 A at Missouri State University taught by Dr. Durham in Spring 2016. Since its upload, it has received 14 views. For similar materials see General Biology in Biology at Missouri State University.
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Date Created: 03/29/16
Mart 1 Lecture 5: Phylogeny and Systematics ● Evolutionary biology is about natural selection, speciation and history the goal is to reconstruct history of life on Earth. ● Systematics is the study of biological diversity in evolutionary context. ○ The development of phylogeny, the evolutionary history of a species or group of related species. ● Fossils are preserved remnants or impressions left by organisms that lived in the past. ○ Ultimately, historical documents of biology. ○ The fossil record is an ordered array in which fossils appear within sedimentary rocks, record passing of geological time. ■ Trace fossils are footprints, burrows, or other impressions left by activities of animals fossilized behavior. ○ The most common fossilized material is pollen because of it’s hard organic case. ○ By comparing different sites, geologists established ageological time scale. ■ Periods are grouped into four eras: Precambrian, Paleozoic, Mesozoic, and Cenozoic areas. ■ Boundaries correspond to times of great change, especially mass extinctions, not to periods of similar length. ○ Radiometric dating is a method often used to determine the absolute ages of fossils. ● The four overlapping stages of life. ○ Nucleotides and amino acids produced prior to the existence of cells. ○ Nucleotides and amino acids became polymerized to form DNA , RNA , and proteins. ○ Polymers became enclosed in membranes . ○ Polymers enclosed in membranes acquired cellular properties. ● Stage 1: The origin of organic molecules. ○ Conditions on primitive Earth may have been more conducive to spontaneous formation of organic molecules. ○ Prebiotic or abiotic synthesi (making compounds using nonliving molecules). ■ Little free oxygen gas. ■ Formed prebiotic soup. ○ Several hypotheses on where and how organic molecules originated. ■ Reducing atmosphere hypothesis based on geological dataStanley Miller showed organisms evolving from prehistoric weather conditions. ■ Extraterrestrial hypothesis meteorites brought organic carbon to Earth. Mart 2 ■ Deepsea vent hypothesis Biologically important molecules may have been formed in the temperature gradient between extremely hot vent water and cold ocean water. ● Stage 2: Organic polymers. ○ Experimentally, prebiotic synthesis of polymers not possible in aqueous solutions. ■ Hydrolysis competes with polymerization ○ Experiments have shown formation of nucleic acid polymers and polypeptides on clay surface. ● Stage 3: Formation of boundaries. ○ Protobiont (protocells). ■ An aggregate of prebiotically producing molecules and macromolecules. ■ Have acquired a boundary, such as a lipid bilayer, that allow it to maintain an internal chemical environment district from that of its surroundings. ■ Four characteristics of a protobiont: ● Boundary separated external environment from internal contents. ● Polymers inside the protobiont containing information. ● Polymers inside the protobiont had enzymatic function. ● Protobionts capable of self replication. ○ Coacervates droplets that form spontaneously from the association of charged polymers (enzymes trapped inside can perform primitive metabolic functions). ○ Liposomes vesicles surrounded by a lipid layer, clay can catalyze formation of liposomes that grow and divide. ● Stage 4: RNA world. ○ The majority of scientists favor RNA as the first macromolecule of protobionts. ○ Three key RNA functions: ■ The ability to store information. ■ Capacity for selfreplication. ■ Enzymatic function (ribozymes). ○ DNA and proteins cannot do all three functions. ● Chemical selection. ○ A chemical within a mixture has special properties that cause it to increase in number compared to other chemicals in the mixture. ○ Hypothetical scenario with two steps: ■ One of the RNA molecules mutates and has enzymatic ability to attach nucleotides together. ■ Second mutation produces enzymatic ability to synthesize nucleotides. ● Advantages of DNA / RNA / protein world. ○ Information stage DNA would have relieved RNA of informational role and allowed RNA to do other functions. Mart 3 ○ Metabolism and other cellular functions proteins have greater catalytic potential and efficiency, and have the ability to perform other tasks. ● Fossil record is a substantial, but incomplete, chronicle of evolutionary history. ○ The discovery of a fossil depends on a sequence of improbable events. ○ Large fraction of species that have lived left no fossils and only fraction of existing fossils have been discovered. ● History of Earth helps explain the current geographical distribution of species. ○ Continental drift is the major geographical factor correlated with distribution of life. ○ Continents drift about Earth’s surface on plates of crust floating on hot mantle. ● 250 million years ago all land masses joined into one supercontinPangaea . ○ Each continent was a separate evolutionary arena and organisms in different biogeographic realms diverged. ● Brief periods of mass extinction were followed by extensive diversification. ○ A species may become extinct because: ■ Habitat destroyed, environment changed in an unfavorable direction, evolutionary changes by some other species. ○ Extinction is inevitable in a changing world, there have been 5 to 7 mass extinctions. ■ Permian mass extinction by far the greatest extinction of all time, 90% of all marine species were killed. ■ Cretaceous mass extinction half of marine species, many families of plants and animals including nearly all dinosaur lineages were killed. ○ Adaptive radiation is the rapid evolution of diversely adapted species from a common ancestor. ● Tracing phylogeny (evolutionary history of life) is one of the main goasystematics is the study of biological diversity in an evolutionary context. ○ Binomial system binomial. ■ 1st part,enus, closest group to which a species belongs. ■ 2nd part, specific epithe, refers to ospecieswithin each genus. ○ Hierarchical classification is the grouping of species into broader taxonomic categories. ■ Genera grouped into progressively broader categoriesspecie,genus, family,order,class phylum,ingdom. ■ A taxon is a named taxonomic unit at any level. ○ Systematics use cladistic analysis, a phylogenetic diagramcladogram constructed from a series of differences. ■ Each branch or clade consists of an ancestral species and all its descendents. Mart 4 ■ A cladogram presents chronological sequence of branching during evolutionary history of a set of organisms. ○ Molecular clocks ● There are five kingdoms: ○ Monera, Protista, Plantae, Fungi and Animalia.
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