Origin & Evolution of Life PDF

Topic 3 The Origin & Evolution of Life Early Earth & Change Over Time (Sections 25.1‐25.5; 21.4, 28.1) What is evolution? Evolution: Biological Context Evolution is Early amphibian how...

Topic 3 The Origin & Evolution of Life Early Earth & Change Over Time (Sections 25.1‐25.5; 21.4, 28.1) What is evolution? Evolution: Biological Context Evolution is Early amphibian how 360 populations of Millions of years ago (mya) LATE DEVONIAN PERIOD organisms change across Tiktaalik roseae generations. 370 Evolution = Descent with Fish Modification 377 380 To understand this … we need to understand to understand how life originated What do we need to learn about to understand how evolution works? T3 What enabled the origination of life? T4 What are the requirements for evolution? T5 What are the mechanisms of evolution? T6 Mechanism: natural selection Topic 3: Learning Objectives After completing this lecture, you should be able to do the following (if you can’t, these are good questions to review during Office Hours). 1. Describe the conditions on early earth and how they changed over earth’s history (including atmospheric) 2. Know the important events leading to the origins of life on earth and the order in which they occurred, beginning from the formation of organic molecules Including the Miller‐Urey Experiment & RNA World to DNA World 3. Explain the “Prokaryotic World”, Endosymbiotic Theory, and Horizontal Transfer and their relevance to early life on earth 4. Apply and calculate the age of fossils and know how both absolute and relative dating can inform when events happened in earth’s history So when did life originate? We can translate Earth’s history to a 24 hr scale Event BYA 24‐Hour Analogy Life began 3.5 ~5:20am Oxygen produced 2.7 ~9:36am Eukaryotes 2.5 ~10:40am Multicellularity 1.2 ~5:36pm Animals 0.635 ~8:37pm Vertebrates 0.52 ~9:14pm Mammals 0.245 ~10:42pm Primates 0.065 ~11:39pm Humans 195,000 yrs ~11:59:56:pm What has changed in the last ~4.5 billion years? L1 1. The position of land masses on earth Earth’s crust formed rigid slabs of rock called plates, located under continents and oceans All the continents were joined together into a single land mass known as Pangea, which started to break apart about 200 million years ago What has changed in the last ~4.5 billion years? L1 2. Earth’s climate Earth has been gradually cooling since its formation, but there have been occasional extreme drops in temperature, resulting in complete ice coverage of the planet All changes in climate can affect the survival of organisms Characterizing the conditions of early earth L1 (4.2‐3.9 bya)  Little free O2  Acidic H2O was present 4 bya  Gases, mainly H2, CO2, N2, H2O  Smaller amounts of NH3, CH4,CO, H2S  Hotter than today  Microbes evolved in these environments and still live in environments like these today. Water vapor Condensed, Rain Puddles, lakes, released rainfall evaporated ponds, oceans Given these changes in the environment, how did life originate? Scientific Premise: All natural phenomena, including life, can be explained by the application of natural laws. The origin of life is explained in terms of chemistry In this topic, we are focusing on proximate explanations for the evolution of life Origination of life: what led to the formation L2 of cells? H H O H H O H H O... N C C N C C N C C... R R R Cell theory: Cells are the basic units of life Origination of life: what led to the formation L2 of cells? We can break down what is needed for cells to form into 4 questions: Where do organic How do cell How is the How does cell relationship molecules come membranes established between metabolism from? form? DNA and Proteins? get started? Where do organic molecules come from? Inorganic to Organic Artificial Synthesis of Organic Molecules L2 It used to be thought Inorganic Reactants Organic Molecules that only living organisms could produce organic compounds O C O N 1828 first artificial H H H O H H O synthesis of “organic” P H N C C OH compound (Urea) -O O- O- H from inorganic starting materials (German chemist Friedrich Wöhler)  Miller‐Urey Experiment – 1952: demonstrates L2 Organic Molecules can form spontaneously Stanley Miller and Harold Urey simulated conditions of early atmosphere o No oxygen o Sparks to simulate lightening o Inorganic reactants Spontaneously produced a wide range of organic molecules, including >20 amino acids. Demonstrated possibility of spontaneous origin of organic molecules  Organic Molecule formation has been discovered in deep sea vents in the oceans and in a variety of other experimental conditions. How Do Cell Membranes Form? Life in a bubble Why are cell membranes important? L2 Cells and organelles are Membranes surrounded by membranes Membranes are made of molecules that have Hydrophilic Components Hydrophobic Components Are similar to the molecules that comprise soap Spontaneously form bubbles How did cell membranes originate? L2 Protocells: Early membranes trapped organic molecules inside when they formed spontaneously in the early earth. Protocell with Trapped Organic Molecules Now we can have organic molecules contained within a membrane… How is the relationship established between DNA and Proteins? The Birth of Central Dogma The central dogma: information flows from L2 DNA to RNA to protein How did this originate? DNA RNA Protein 5’ 3’ T A A G C C Transcription Translation A U T A U T T A A C G G 3’ 5’ RNA is between DNA and Protein in the Central Dogma RNA stores information similar to DNA RNA can fold up and have enzymatic activity similar to proteins RNA World Hypothesis: Hypothesis that the first life functions were based on RNA  Prior to having DNA, RNA, and proteins, there L2 was just RNA: the RNA World Hypothesis 1 of trillions of Organic protocells may have contained RNA with Soup with enzymatic ability to trillions of link RNA monomers proto‐cells to duplicate themselves 1 of trillions of Random RNA and assembled RNA Polymers + Duplicate RNA RNA Monomers From the RNA world to the central dogma: L2 Chemical selection Errors during RNA replication would have resulted in new RNAs and new molecules: Faster RNA enzymes becoming more abundant Different types of RNAs RNAs that linked DNA monomers RNAs that linked amino acids, forming proteins From the RNA world to the central dogma: L2 Chemical selection Because proteins have greater enzymatic ability, they would have taken over most enzymatic processes Because DNA is more stable than RNA, it would have taken over the information storage process RNA retained its central role in the forms of tRNA, mRNA, rRNA, and others. Each of the three types of molecules becomes specialized on ~one function How does cell metabolism get started? Birth of Modern Cells  Establishment of metabolism: L2 mutations diversification complexity Mutations to DNA lead to production of novel proteins Protocells with proteins whose shape gave them useful functions became more common Provide a bridge for molecules to enter from the outside Link molecules together to make membrane molecules Break down larger polymers to release energy Alter structure and function due to light absorption Catalyze production of novel molecules Etc. Origination of life: what led to the formation L2 of cells? We can break down what is needed for cells to form into 4 questions: Where do organic How do cell How is the How does cell relationship molecules come membranes established between metabolism from? form? DNA and Proteins? get started? Miller Urey Mutations and Membranes form Chemical selection demonstrates subsequent bubbles results in DNA and spontaneous proliferation of spontaneously, proteins, connected formation from proteins with useful trapping molecules by RNA inorganic functions What is the correct order for the events leading to early life on earth? a) I, II, III, IV b) III, II, I, IV I. Formation of Organic Molecules c) III, IV, I, II II. Formation of Membranes d) IV, I, III, II III. RNA World to DNA transition e) IV, III, I, II IV. Initiation of Metabolic pathways We have now covered the very proximate explanations for how life originated Let’s look at how early life diversified, and what tools enable us to understand the diversification of early life What have been some of the major events in the evolution of life as we know it today? How can we know about what happened in the past? 1) Organic Molecules Last Universal Common Ancestor 2) Membranes Earliest organism whose progeny survived to evolve 3) RNA World ‐> DNA World into all existing life forms 4) Metabolism A prokaryotic cell (before the evolution of a nucleus)  /8 &$ Bacteria Archaea Eukarya Back to the 24 hr scale: Event BYA 24‐Hour Analogy Life began 3.5 ~5:20am Oxygen produced 2.7 ~9:36am Eukaryotes 2.5 ~10:40am Multicellularity 1.2 ~5:36pm Animals 0.635 ~8:37pm Vertebrates 0.52 ~9:14pm Mammals 0.245 ~10:42pm Primates 0.065 ~11:39pm Humans 195,000 yrs ~11:59:56:pm First life: Prokaryotes ~3.5 bya (5:20 am) L3 Prokaryote: Unicellular microorganism that lacks a nucleus and has almost no internal membranes Metabolically extremely diverse First life: Prokaryotes ~3.5 bya (5:20 am) L3 Stromatolites: Mats formed by prokaryotic fossils and sediment Develop in layers in marshes and lagoons Modern Stromatolite Fossil Stromatolite Prokaryotic World: Event BYA 24‐Hour Analogy Prokaryotes dominated for L3 Life began Oxygen produced 3.5 2.7 ~5:20am ~9:36am Eukaryotes 2.5 ~10:40am at least 2 billion years Multicellularity 1.2 ~5:36pm Animals 0.635 ~8:37pm First Prokaryotes were probably Vertebrates 0.52 ~9:14pm heterotrophs (feeding on the Mammals Primates 0.245 0.065 ~10:42pm ~11:39pm organic soup) or chemoautotrophs Humans 195,000 yrs ~11:59:56:pm Oxygenic photosynthesis bacteria O2 from photosynthesis evolved ~2.7 bya (photoautotrophs Dissolved in water – e.g. cyanobacteria) Precipitation as iron oxide initially prevented Banded Iron – evidence of accumulation oxygenic Additional O2 photosynthesis accumulated in atmosphere Atmospheric Oxygen Availability Led to L3 Increasing Diversity ~ 2.7 bya O2 levels rose rapidly Earth’s atmosphere changed from reducing to oxidizing O2 began to be used for metabolism (aerobic cellular respiration) O2‐based cellular respiration releases energy more efficiently for metabolic processes. Origin of Eukaryotic Cells (2.5 bya; 10:40am) L3 Prokaryotic DNA is not bound by Plasma membrane a membrane Cytoplasm DNA Eukaryotes evolved with the Ancestral formation of a membrane prokaryote Nucleus Endoplasmic around the nucleus (~2.5 bya) reticulum Allowed transcription to be separated from translation for Nuclear envelope Ancestral greater regulation. Eukaryote One defining feature of eukaryotic cells: L3 mitochondria How did mitochondria and chloroplasts originate? Endosymbiotic Theory: Mitochondria and Chloroplasts originated as Mutualistic Endosymbiotes Endosymbiotes lost ability to survive independently becoming organelles Plasma membrane Cytoplasm DNA Ancestral prokaryote Nucleus Endoplasmic Photosynthetic reticulum prokaryote Mitochondrion Nuclear envelope Aerobic heterotrophic prokaryote Mitochondrion Plastid Ancestral Ancestral photosynthetic heterotrophic eukaryote eukaryote KE0 Slide 55 KE0 IF we know where this video came from, we can remove it here and put a link to it instead. Katherine Elizabeth Eisen, 2024-12-17T18:11:57.254 Evidence for endosymbiotic origin of L3 mitochondria and chloroplasts 1. Size and structure is similar to prokaryotes 2. Double membrane as would result from endocytosis. 3. Inner membrane is folded similarly to many bacteria 4. M and C have their own circular chromosomes 5. DNA sequence more similar to prokaryotes. 6. M and C have their own prokaryote‐like ribosomes. 7. M and C reproduce independently within cells by binary fission. Origin of multicellularity (1.2 bya; 5:36 pm) L3 Multicellular Organisms evolved when daughter cells developed cell adhesion molecules and/or extracellular matrix Multicellularity allowed specialization: cells can have different fates, ↑ in complexity Origin of multicellularity (1.2 bya; 5:36 pm) L3 Chlamydomonas Gonium Pleodorina Volvox aureux reinhardtii pectorale californica (1000‐2000 (unicellular alga) (8 identical (64‐28 cells; cells; Homo sapiens cells) 2 types: 2 types: (50‐75 trillion cells; somatic and somatic and >400 types) reproductive) reproductive) Event BYA 24‐Hour Analogy Life began 3.5 ~5:20am Oxygen produced 2.7 ~9:36am Eukaryotes 2.5 ~10:40am Multicellularity 1.2 ~5:36pm Animals 0.635 ~8:37pm Vertebrates 0.52 ~9:14pm Mammals 0.245 ~10:42pm Primates 0.065 ~11:39pm Humans 195,000 yrs ~11:59:56:pm How do we know when these key events L4 happened in the past? We use the fossil record in two ways: 1. Relative Dating Placing fossils in relative age order (older to younger) without actual dates Often possible when fossils form in sedimentary rocks How do we know when these key events L4 happened in the past? 2. Absolute dating Applying numbered dates to fossil ages (e.g. 65mya) Accumulating Accomplished through “daughter” isotope radiometric dating using 1 2 the different ½ lives of Surviving parent Isotope 1 4 radioactive isotopes. 1 8 1 16 1 2 3 4 Time (half‐lives) Over time, the parent isotope (P) is converted to the daughter isotope (D) Time = 1 HL Time = 2 HL Time = 3 HL Parent = 50% Parent = 25% Parent = 12.5% Daughter = 50% Daughter = 75% Daughter = 87.5% Time = 4 HL Time = 0 Parent = 6.25% Parent = 100% Daughter = 93.75% Accumulating “daughter” isotope 1 2 Surviving parent Isotope 1 4 1 8 1 16 1 2 3 4 Time (half‐lives) Absolute dating L4 Over time, the parent isotope (P) is converted to the daughter isotope (D) At start After 1 half life After 2 HLs After 3 HLs After 4 HLs 100% parent 1/2 parent 1/4 parent 1/8 parent 1/16 parent Multiply by ½ Multiply by ½ Multiply by ½ Multiply by ½ every time every time every time every time Whatever fraction isn’t left in the parent is in the form of the daughter At start After 1 half life After 2 HLs After 3 HLs After 4 HLs 0% daughter 1/2 daughter 3/4 daughter 7/8 daughter 15/16 daughter Absolute dating L4 Types of radiometric dating questions L4 Determine the age of a fossil (either in years or numbers or half lives) based on the mass of the parent and the mass of the daughter isotopes Requires information about total mass, mass of one (or both) isotope(s) and length of half life Using percentages of an isotope remaining or accumulated to determine how many half‐lives have passed Requires information about percentages only If a fossil is a certain age, what percentage parent/daughter will there be? Requires information about length of half life and estimated age Two questions on HW 1A K40 decays to Ar40 with a half life of 1.3 billion years. If you find a 500g fossil that contains ~80g of K40, how old would you expect the fossil to be? a) 1.3 billion years b) 3.9 billion years c) 2.6 billion years d) Between 2.6 and 3.9 billion years You find a fossil that you believe to be 18,000 years old. You know that C14 decays to C12 with a half life of 6,000 years. If your dating is correct, what percentage of the fossil is composed of C14? What do we need to learn about to understand how evolution works? T3 What enabled the origination of life? T4 What are the requirements for evolution? T5 What are the mechanisms of evolution? T6 Mechanism: natural selection  Where do organic How do cell How is the How does cell relationship molecules come membranes established between metabolism from? form? DNA and Proteins? get started? Event BYA 24‐Hour Analogy Life began 3.5 ~5:20am Oxygen produced 2.7 ~9:36am Eukaryotes 2.5 ~10:40am Multicellularity 1.2 ~5:36pm Animals 0.635 ~8:37pm Vertebrates 0.52 ~9:14pm Accumulating 12 “daughter” Mammals 0.245 ~10:42pm isotope Surviving 14 Primates 0.065 ~11:39pm parent 1 8 1 16 Humans 195,000 yrs ~11:59:56:pm Isotope 1 2 3 4 Time (half‐lives) Topic 3: Learning Objectives After completing this lecture, you should be able to do the following (if you can’t, these are good questions to review during Office Hours). 1. Describe the conditions on early earth and how they changed over earth’s history (including atmospheric) 2. Know the important events leading to the origins of life on earth and the order in which they occurred, beginning from the formation of organic molecules Including the Miller‐Urey Experiment & RNA World to DNA World 3. Explain the “Prokaryotic World”, Endosymbiotic Theory, and Horizontal Transfer and their relevance to early life on earth 4. Apply and calculate the age of fossils and know how both absolute and relative dating can inform when events happened in earth’s history Two questions on HW 1A This newly identified species, called Sanfordiacaulis densifolia, was found near the bottom of an active rock quarry in Valley Waters, New Brunswick It is 350 million years old and provides clues as to what life was like during a mysterious period paleontologists refer to as Romer’s Gap: a relatively short span of time when not much is known about the trajectory of life between 345 million and 360 million years ago, after fish began to take to land. https://www.smithsonianmag.com/smart‐news/rare‐ fossil‐shows‐trees‐looked‐very‐different‐350‐million‐ years‐ago‐180983733/