1The Nature of Life on Earth(Chap. 5 - Bennett & Shostak)Notes for Chapter 5HNRS 228 - AstrobiologyDr. H. Geller (with some slides from Dr. G. Taylor and HNRS 227)Overview of Chapter 5Defining Life (5.1)Its properties, evolution and definitionCells: The basic units of life (5.2)Structure, composition, prokaryotes, eukaryotesMetabolism: The chemistry of life (5.3)Energy needs and sources; waterDNA and Heredity (5.4)Structure, replication, genetic codeOverview of Chapter 5Life at the Extremes (5.5)Extremophiles and their implicationsEvolution as Science (5.6)Properties of Living SystemsNot lawsFrom Bennett & Shostak:Order (hierarchy)ReproductionGrowth and developmentEnergy useResponse to the environment (open systems)Evolution and adaptationProperties of Living SystemsFrom Taylor (HNRS 227):Hierarchical organization and emergent propertiesRegulatory capacity leading to homeostasisDiversity and similarityMedium for life: water (H2O) as a solventInformation ProcessingProperties of Living Systems: OrderDefine “random”Define “order” in an abiotic systemWhy is “order” an important property”Examples of “order” in living systemsLevel of a biomoleculeLevel of the cellLevel of the organelleLevel of an ecosystemRelate to hierarchical2Properties of Living Systems: ReproductionDefine “reproduction” in abiotic termsE.g., fire, crystalsDefine “reproduction” in biotic termsWhy is it important property of living systems?Examples in living systemsMicrobes (fission)Cells (mitosis)Whole organisms ⌧DonkeyProperties of Living Systems: Growth and DevelopmentDefine “growth”Define “development”Why are “growth and development” important properties of living systemsExamples in living systemsOrganisms growOrganisms developExamples in abiotic systemsIce crystalsFireProperties of Living Systems: Energy UseDefinitionsEnergy capture⌧Autotrophs (photoautotrophs, chemoautotrophs)⌧Heterotrophs (saprovores, carnivores, omnivores, etc.)Energy utilization (1stand 2ndLaws of Thermodynamics)Energy storage⌧Chemical bonds (covalent C-C bonds) and exothermic reactions⌧ATP (adenosine triphosphate) and ADP (adenosine diphosphate)Energy dissipation (2ndLaw of Thermodynamics)Why is “energy use” and important property of living systems?Properties of Living Systems: Energy UseCatabolism BiosynthesisATPADPMetabolic “Class”Properties of Living Systems: Response to the EnvironmentDefine an “open” versus “closed” systemInteraction with the environmentStimulus followed by a responseWhy is “response to the environment” an important property?Examples in living systemsLeaf orientation to the sunEyesEars3Properties of Living Systems: Evolution and AdaptationDefine “evolution”Define “adaptation”Why is “evolution and adaptation” an important property in living systems?Examples of evolution in living systemsMacroscale: origin of species and taxaMicroscale: ⌧microbes resistant to antibiotics⌧moths resistant to air pollutionExamples of adaptationArticulation of the joints in animalsPlanar structure of leavesProperties of Living Systems: Hierarchical OrganizationDefine “hierarchical organization”diagram of atoms to biomolecules to organelles to cells to tissues, etc.Define “emergent properties”Emergence of “novel and unanticipated” properties with each step of hierarchyExamples in living systemsHierarchyEmergent propertiesProperties of Living Systems: Regulatory CapacityDefine “regulatory capacity”Relate to open systemsDefine “homeostasis”Role of feedbacks (positive and negative) and cyberneticsWhy is “regulatory capacity and homeostasis” and important property of living systems?ExamplesMolecular biology: gene regulationBiochemistry: enzymesOrganisms: temperatureGlobe: “Parable of the Daisyworld”Properties of Living Systems: Regulatory Capacity (Continued)StateVariableState VariableSensorSetPointPositive FeedbackNegative FeedbackProperties of Living Systems: Diversity and SimilarityDefine “diversity”Hallmark of all life (1.5 M known species; 100 M expected)Define “similarity”Hallmark of all lifeWhy are “diversity and similarity” important properties of living systems? Examples of similarity⌧Biochemistry⌧Structure and Morphology⌧DNA and RNAProperties of Living Systems: Medium for MetabolismDefine a “medium for metabolism” and why an important property of living systems?Role of “water” as mediumPhysical properties⌧Abundance in universe, state as a f unction of temperature, freezing propertiesChemical properties⌧Bonding, polarity, diffusion, osmosis4Properties of Living Systems: Information Define “information” and relate to orderWhy is “information” an important property of living systems”Necessary states of “information”StorageTranslationTemplate/CopyingCorrecting (spell check)ExamplesDNARNAProperties of Living Systems: RecapitulationDiversity and similarity of structure and functionWhat does above suggest?Recurrent theme of similar properties ⌧High fitness value⌧Common ancestorRecurrent theme of diverse properties⌧High fitness value⌧Diversity of habitats⌧Creativity and spontaneity of evolutionWhat mechanism can account for both similarity and diversity? Evolution as a Unifying ThemeDarwin’s Origin of Species (1850)Observations while on the HMS BeagleModel: Evolution⌧Individuals vary in their fitness in the environment⌧Struggle for existence and survival of the most fit⌧Origin of species viaincremental changes in form and function (relate back to observation while on the Beagle)Link to Mendel and the Particulate Model of Inheritance (1860’s)Link to Watson and Crick (1956) and the discovery of DNAExamples of evolution in actionSignificance of evolution as a theory in BiologyStructural Features of Living Systems Ubiquitous nature of “cells” and its hierarchyPhysical, chemical and biological basis for a cell (adaptation)Suggestion of a common progenitor/ancestorPhysical dimensions of a cell (maximum size)Ubiquitous nature of “organelle”Efficacy of metabolism (random)Diversity of