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Biology Lecture 5 - Exam 1

by: Devin Mart

Biology Lecture 5 - Exam 1 BIO 121 A

Marketplace > Missouri State University > Biology > BIO 121 A > Biology Lecture 5 Exam 1
Devin Mart
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Phylogeny and Systematics
General Biology
Dr. Durham
Class Notes
Biology 120 - General Biology
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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  ○ Ultimately, historical documents of biology.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 ­ b​inomial.  ■ 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 t​axon 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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