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“…sparked by just the right combination of physical events & chemical processes…”
Origin of Life – Ch 14
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Focus 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.
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Assessing Prior Knowledge
1. Name the elements common to all organic compounds. Carbon Hydrogen Oxygen
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Name the four types of organic compounds found in living thing and state a major role in each.
Carbohydrates - Proteins Lipids Nucleic acids
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The evolutionary tree of life can be documented with evidence.
Bacteria Archae- bacteria Animalia Fungi Protista Plantae 4500 4000 3500 3000 2500 2000 500 1500 1000 Formation of earth Molten-hot surface of earth becomes cooler Oldest definite fossils of prokaryotes Appearance of oxygen in atmosphere of eukaryotes First multicellular organisms Appearance of animals and land plants Colonization of land by animals Paleozoic Mesozoic Cenozoic Millions of years ago ARCHEAN PRECAMBRIAN PROTEROZOIC The evolutionary tree of life can be documented with evidence. The Origin of Life on Earth is another story…
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Ch 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.
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Terms to know Biogenesis - 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.
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What is Life? First we have to define LIFE… organized as cells
respond to stimuli regulate internal processes homeostasis use energy metabolism Develop and Grow change & mature within lifetime reproduce heredity DNA / RNA adaptation & evolution
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The Origin of Life is a Hypothesis
Extraterrestrial Origin Was the original source of organic (carbon) materials comets & meteorites striking early Earth? Testable Spontaneous Abiotic Origin Did life evolve spontaneously from inorganic molecules? testable
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In 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.
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Redi’s Experiment 1668 Showed that rotting meat kept away from flies would not produce new flies. Maggots appeared only on meat that had been exposed to flies.
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Spallanzani’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.
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Pasteur’s Experiment Used a variation of Spallanzani’s design to prove that mo’s are carried in the air and do not arise by spontaneous generation.
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14-2 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.
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Conditions on early Earth
Reducing atmosphere water vapor (H2O), CO2, N2, NOx, H2, NH3, CH4, H2S lots of available H & its electron no free oxygen Energy source lightning, UV radiation, volcanic low O2 = organic molecules do not breakdown as quickly It 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?
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Lerman Bubble Model
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Origin of Organic Molecules
Water vapor Condensed liquid with complex, organic molecules Condenser Mixture of gases ("primitive atmosphere") Heated water ("ocean") Electrodes discharge sparks (lightning simulation) Water Origin of Organic Molecules Abiotic synthesis 1923 Oparin & Haldane propose reducing atmosphere hypothesis 1953 Miller & Urey test hypothesis formed organic compounds amino acids adenine CH4 H2 NH3
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http://glencoe. mcgraw-hill
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Stanley Miller University of Chicago produced -amino acids
-hydrocarbons -nitrogen bases -other organics It’s ALIVE!
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Origin of Cells (Protobionts)
Bubbles separate inside from outside metabolism & reproduction Microspheres – Primitive cell membranes made of proteins Coacervates – droplets of linked sugars and amino acids Bubbles… 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.
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Key Events in Origin of Life
Key events in evolutionary history of life on Earth Sun Formation 5 bya Earth Formation 4.5 bya Life originated 3.5–4.0 bya
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Radioactive 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.
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Prokaryotes Prokaryotes dominated life on Earth from 3.5–2.0 bya
3.5 billion year old fossil of bacteria modern bacteria Electron Transport Systems The 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
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Oxygen atmosphere Oxygen begins to accumulate 2.7 bya
reducing oxidizing atmosphere evidence in banded iron in rocks = rusting makes aerobic respiration possible Cyanobacteria - photosynthetic algae
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Prokaryotic ancestor of eukaryotic cells
~2 bya First Eukaryotes Development of internal membranes create internal micro-environments advantage: specialization = increase efficiency nuclear envelope endoplasmic reticulum (ER) plasma membrane infolding of the plasma membrane nucleus DNA cell wall plasma membrane Prokaryotic cell Prokaryotic ancestor of eukaryotic cells Eukaryotic cell
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internal membrane system
Endosymbiosis Evolution of eukaryotes origin of mitochondria engulfed aerobic bacteria, but did not digest them mutually beneficial relationship internal membrane system aerobic bacterium mitochondrion Endosymbiosis Ancestral eukaryotic cell Eukaryotic cell with mitochondrion
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photosynthetic bacterium chloroplast & mitochondrion
Eukaryotic cell with mitochondrion Endosymbiosis Evolution of eukaryotes origin of chloroplasts engulfed photosynthetic bacteria, but did not digest them mutually beneficial relationship photosynthetic bacterium chloroplast mitochondrion Endosymbiosis Eukaryotic cell with chloroplast & mitochondrion
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Theory of Endosymbiosis
Lynn Margulis Theory of Endosymbiosis Evidence structural mitochondria & chloroplasts resemble bacterial structure genetic mitochondria & chloroplasts have their own circular DNA, like bacteria functional mitochondria & chloroplasts move freely within the cell mitochondria & chloroplasts reproduce independently from the cell
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