Presentation on theme: "“…sparked by just the right combination of physical events & chemical processes…” Origin of Life – Ch 14 2011-2012."— Presentation transcript:
1“…sparked by just the right combination of physical events & chemical processes…” Origin of Life – Ch 14
2Focus of Chapter 14 Matter, Energy, and Organization Life on Earth arose from nonliving matter in a process that required the input of energy. New life-forms evolved from the earliest life-forms, requiring energy input and resulting in highly complex organisms.
3Assessing Prior Knowledge 1. Name the elements common to all organic compounds.CarbonHydrogenOxygen
4Name the four types of organic compounds found in living thing and state a major role in each. Carbohydrates -ProteinsLipidsNucleic acids
5The evolutionary tree of life can be documented with evidence. BacteriaArchae-bacteriaAnimaliaFungiProtistaPlantae45004000350030002500200050015001000Formation of earthMolten-hot surface ofearth becomes coolerOldest definite fossilsof prokaryotesAppearance of oxygenin atmosphereof eukaryotesFirst multicellularorganismsAppearance of animalsand land plantsColonization of landby animalsPaleozoicMesozoicCenozoicMillions of years agoARCHEANPRECAMBRIANPROTEROZOICThe evolutionary tree of life can be documented with evidence.The Origin of Life on Earth is another story…
6Ch 14-1 Biogenesis Objectives Define spontaneous generation; list observations that led people to think that life could arise from nonliving things.Summarize Redi’s and Spallanzani’s experiments testing spontaneous generation.Describe Pasteur’s experiment and how it disproved the hypothesis of spontaneous generation.
7Terms to knowBiogenesis - all living things come from other living things.Spontaneous generation – an early and now disproved hypothesis that stated that living organisms develop from nonliving material.
8What is Life? First we have to define LIFE… organized as cells respond to stimuliregulate internal processeshomeostasisuse energymetabolismDevelop and Growchange & mature within lifetimereproduceheredityDNA / RNAadaptation & evolution
9The Origin of Life is a Hypothesis Extraterrestrial OriginWas the original source of organic (carbon) materials comets & meteorites striking early Earth?TestableSpontaneous Abiotic OriginDid life evolve spontaneously from inorganic molecules?testable
10In the 17th century it was widely believed that living things could arise from nonliving things in a process called spontaneous generation.Explained why:Maggots appeared on rotting meat.Fish appeared in ponds that had been dry the previous season.Today we believe in biogenesis, where all living things come from other living things.
11Redi’s Experiment1668Showed that rotting meat kept away from flies would not produce new flies.Maggots appeared only on meat that had been exposed to flies.
12Spallanzani’s Experiment Showed that microorganisms would not grow in broth when its containers was heated and then sealed.Seems to indicate that microorganisms that cause food spoilage do not arise from spontaneous generation but, rather are carried in air.
13Pasteur’s ExperimentUsed a variation of Spallanzani’s design to prove that mo’s are carried in the air and do not arise by spontaneous generation.
1414-2 Earth’s History Objectives Describe the conditions of early Earth.Describe the production of organic compounds in the Miller-Urey apparatus.Summarize the possible importance of cell-like structures produced in the laboratory.
15Conditions on early Earth Reducing atmospherewater vapor (H2O), CO2, N2, NOx, H2, NH3, CH4, H2Slots of available H & its electronno free oxygenEnergy sourcelightning, UV radiation, volcaniclow O2 = organic molecules do not breakdown as quicklyIt is unclear whether young Earth’s atmosphere contained enough methane and ammonia to be reducing. Growing evidence suggests that the early atmosphere was made up primarily of nitrogen and carbon dioxide and was neither reducing nor oxidizing (electron–removing). Miller–Urey–type experiments using such atmospheres have not produced organic molecules. Still, it is likely that small “pockets” of the early atmosphere—perhaps near volcanic openings—were reducing.Instead of forming in the atmosphere, the first organic compounds on Earth may have been synthesized near submerged volcanoes and deep–sea vents—weak points in Earth’s crust where hot water and minerals gush into the ocean.What’s missing from that atmosphere?
17Origin of Organic Molecules Water vaporCondensed liquid with complex, organicmoleculesCondenserMixture of gases("primitiveatmosphere")Heated water("ocean")Electrodes discharge sparks(lightning simulation)WaterOrigin of Organic MoleculesAbiotic synthesis1923 Oparin & Haldane propose reducing atmosphere hypothesis1953 Miller & Urey test hypothesisformed organic compoundsamino acidsadenineCH4H2NH3
19Stanley Miller University of Chicago produced -amino acids -hydrocarbons-nitrogen bases-other organicsIt’s ALIVE!
20Origin of Cells (Protobionts) Bubbles separate inside from outside metabolism & reproductionMicrospheres – Primitive cell membranes made of proteinsCoacervates – droplets of linked sugars and amino acidsBubbles… Tiny bubbles…Life is defined partly by two properties: accurate replication and metabolism. Neither property can exist without the other. Self–replicating molecules and a metabolism–like source of the building blocks must have appeared together. How did that happen?The necessary conditions for life may have been met by protobionts, aggregates of abiotically produced molecules surrounded by a membrane or membrane–like structure. Protobionts exhibit some of the properties associated with life, including simple reproduction and metabolism, as well as the maintenance of an internal chemical environment different from that of their surroundings.Laboratory experiments demonstrate that protobionts could have formed spontaneously from abiotically produced organic compounds. For example, small membrane–bounded droplets called liposomes can form when lipids or other organic molecules are added to water.
21Key Events in Origin of Life Key events in evolutionary history of life on EarthSun Formation 5 byaEarth Formation 4.5 byaLife originated 3.5–4.0 bya
22Radioactive Carbon Dating The process that allows scientists to age objects based on the amount of radioactive material in the object.Radioactive Isotopes are unstable elements that breakdown over time.Radioactive decay is the converting of radioactive material into a stable format through the loss of energy.Half-Life is the amount of time it takes for one half of a given amount of isotope to become stable.
23Prokaryotes Prokaryotes dominated life on Earth from 3.5–2.0 bya 3.5 billion year old fossil of bacteriamodern bacteriaElectron Transport SystemsThe chemiosmotic mechanism of ATP synthesis, in which a complex set of membrane–bound proteins pass electrons to reducible electron acceptors with the generation of ATP from ADP, is common to all three domains of life—Bacteria, Archaea, and Eukarya. There is strong evidence that this electron transport mechanism actually originated in organisms that lived before the last common ancestor of all present–day life. The earliest of these electron transport systems likely evolved before there was any free oxygen in the environment and before the appearance of photosynthesis; the organisms that used it would have required a plentiful supply of energy–rich compounds such as molecular hydrogen, methane, and hydrogen sulfide. A great challenge facing scientists studying the origin of life is to determine the steps by which this electron transport mechanism originated, and how important early versions of it might have been in the emergence of the first cells.So considerable metabolic diversity among prokaryotes living in various environments had already evolved more than 3 billion years ago. Most subsequent evolution has been more structural than metabolic.chains of one-celled cyanobacteria
24Oxygen atmosphere Oxygen begins to accumulate 2.7 bya reducing oxidizing atmosphereevidence in banded iron in rocks = rustingmakes aerobic respiration possibleCyanobacteria - photosyntheticalgae
25Prokaryotic ancestor of eukaryotic cells ~2 byaFirst EukaryotesDevelopment of internal membranescreate internal micro-environmentsadvantage: specialization = increase efficiencynuclear envelopeendoplasmic reticulum (ER)plasmamembraneinfolding of the plasma membranenucleusDNAcell wallplasmamembraneProkaryoticcellProkaryotic ancestor of eukaryotic cellsEukaryoticcell
26internal membrane system EndosymbiosisEvolution of eukaryotesorigin of mitochondriaengulfed aerobic bacteria, but did not digest themmutually beneficial relationshipinternal membrane systemaerobic bacteriummitochondrionEndosymbiosisAncestraleukaryotic cellEukaryotic cellwith mitochondrion
27photosynthetic bacterium chloroplast & mitochondrion Eukaryoticcell withmitochondrionEndosymbiosisEvolution of eukaryotesorigin of chloroplastsengulfed photosynthetic bacteria, but did not digest themmutually beneficial relationshipphotosynthetic bacteriumchloroplastmitochondrionEndosymbiosisEukaryotic cell withchloroplast & mitochondrion
28Theory of Endosymbiosis Lynn MargulisTheory of EndosymbiosisEvidencestructuralmitochondria & chloroplasts resemble bacterial structuregeneticmitochondria & chloroplasts have their own circular DNA, like bacteriafunctionalmitochondria & chloroplasts move freely within the cellmitochondria & chloroplasts reproduce independently from the cell