The Nature of Life (Chap. 3 - Bennett et al.) Lecture 4 HNRS Astrobiology Prof. Geller (with slides adapted from Prof. Taylor)

Overview of Chapter 3 zWhat is Life yIts properties, evolution and definition zCells: The basic units of life yStructure, composition, prokaryotes, eukaryotes zMetabolism: The chemistry of life yEnergy needs and sources; water zDNA and Heredity yStructure, replication, genetic code zLife at the Extremes yExtremophiles and their implications

Properties of Living Systems zNot laws zFrom Bennett et al.: yOrder (hierarchy) yReproduction yGrowth and development yEnergy use yResponse to the environment (open systems) yEvolution and adaptation

Properties of Living Systems zFrom Taylor (HNRS 227): yHierarchical organization and emergent properties yRegulatory capacity leading to homeostasis yDiversity and similarity yMedium for life: water (H 2 O) as a solvent yInformation Processing

Properties of Living Systems: Order zDefine “random” zDefine “order” in an abiotic system zWhy is “order” and important property” zExamples of “order” in living systems yLevel of a biomolecule yLevel of the cell yLevel of the organelle yLevel of an ecosystem zRelate to hierarchical

Properties of Living Systems: Reproduction zDefine “reproduction” in abiotic terms yE.g., fire, crystals zDefine “reproduction” in biotic terms yWhy is it important property of living systems? zExamples in living systems yMicrobes (fission) yCells (mitosis) yWhole organisms xDonkey

Properties of Living Systems: Growth and Development zDefine “growth” zDefine “development” zWhy are “growth and development” important properties of living systems zExamples in living systems yOrganisms grow yOrganisms develop zExamples in abiotic systems yIce crystals yFire

Properties of Living Systems: Energy Use zDefinitions yEnergy capture xAutotrophs (photoautotrophs, chemoautotrophs) xHeterotrophs (saprovores, carnivores, omnivores, etc.) yEnergy utilization (1 st and 2 nd Laws of Thermodynamics) yEnergy storage xChemical bonds (covalent C-C bonds) and exothermic reactions xATP (adenosine triphosphate) and ADP (adenosine diphosphate) yEnergy dissipation (2 nd Law of Thermodynamics) zWhy is “energy use” and important property of living systems?

Metabolic “Class”

Properties of Living Systems: Response to the Environment zDefine an “open” versus “closed” system yInteraction with the environment yStimulus followed by a response zWhy is “response to the environment” an important property? zExamples in living systems yLeaf orientation to the sun yEyes yEars

Properties of Living Systems: Evolution and Adaptation zDefine “evolution” zDefine “adaptation” zWhy is “evolution and adaptation” an important property in living systems? zExamples of evolution in living systems yMacroscale: origin of species and taxa yMicroscale: xmicrobes resistant to antibiotics xmoths resistant to air pollution zExamples of adaptation yArticulation of the joints in animals yPlanar structure of leaves

Properties of Living Systems: Hierarchical Organization zDefine “hierarchical organization” ydiagram of atoms to biomolecules to organelles to cells to tissues, etc. zDefine “emergent properties” yEmergence of “novel and unanticipated” properties with each step of hierarchy zExamples in living systems yHierarchy yEmergent properties

Properties of Living Systems: Regulatory Capacity zDefine “regulatory capacity” yRelate to open systems zDefine “homeostasis” yRole of feedbacks (positive and negative) and cybernetics zWhy is “regulatory capacity and homeostasis” and important property of living systems? zExamples yMolecular biology: gene regulation yBiochemistry: enzymes yOrganisms: temperature yGlobe: “Parable of the Daisyworld”

Properties of Living Systems: Diversity and Similarity zDefine “diversity” yHallmark of all life (1.5 M known species; 100 M expected) zDefine “similarity” yHallmark of all life zWhy are “diversity and similarity” important properties of living systems? z Examples of similarity xBiochemistry xStructure and Morphology xDNA and RNA

Properties of Living Systems: Medium for Metabolism zDefine a “medium for metabolism” and why an important property of living systems? zRole of “water” as medium yPhysical properties xAbundance in universe, state as a f unction of temperature, freezing properties yChemical properties xBonding, polarity, diffusion, osmosis

Properties of Living Systems: Information zDefine “information” and relate to order zWhy is “information” an important property of living systems” zNecessary states of “information” yStorage yTranslation yTemplate/Copying yCorrecting (spell check) zExamples yDNA yRNA

Evolution as a Unifying Theme zDarwin’s Origin of Species (1850) yObservations while on the HMS Beagle yModel: Evolution xIndividuals vary in their fitness in the environment xStruggle for existence and survival of the most fit xOrigin of species via incremental changes in form and function (relate back to observation while on the Beagle) zLink to Mendel and the Particulate Model of Inheritance (1860’s) zLink to Watson and Crick (1956) and the discovery of DNA zExamples of evolution in action zSignificance of evolution as a theory in Biology

Structural Features of Living Systems zUbiquitous nature of “cells” and its hierarchy yPhysical, chemical and biological basis for a cell (adaptation) ySuggestion of a common progenitor/ancestor yPhysical dimensions of a cell (maximum size) zUbiquitous nature of “organelle” yEfficacy of metabolism (random) yDiversity of function yDiversity of structure ySimilarity of structure

Structural Features of Living Systems (continued) zEvolution of cell types yProkaryotes xCell, membranes but no nucleus xExamples: bacteria yEukaryotes xCell, membrane, and nucleus xAll higher plants and animals

Biochemical Features of Living Systems zCarbon-based economy yAbundance in the universe yAtomic structure (electrons, protons, etc.) yChemical properties (bonding) zMetabolism yCatabolism and biosynthesis yEnergy capture and utilization xATP and ADP

Biochemical Features of Living Systems (continued) zBiochemicals or Bio-macromolecules yDefine polymer again zCarbohydrates zLipids zProteins zNucleic Acids

Biochemical Pathways

Homework Assignment zDefine living systems y1 sentence description (clean, concise) y2 pages supporting statement of why you selected the key properties that you did and why others were ignored yDue next Tuesday yFair game: discussion with classmates but not communal writing