Bio 181 Final Study Guide

Lecture #1: 1. How did the four macromolecules appear on early earth? Components of “Primitive Soup”  Carbohydrates, Lipids, Nucleic Acids, Proteins (four macromolecules of life) We don’t have a clear answer but there are numerous hypotheses. 2. List and explain the basis/background for the four main theories of how life originated on early earth. Are there any challenges these theories have to overcome? a) Oparin-Haldane Hypothesis (tested by Miller-Urey) a. Mimicked atmosphere of primitive Earth i. Reducing atmosphere w/ oceans and lightening (1924  thought that atmosphere was reducing but in 1980 found out that atmosphere is neutral) b. Demonstrated abiotic synthesis of organic compounds c. Results: found 17-20 of amino acids b) Meteorite Hypothesis a. Meteorites that fall to Earth today will often contain amino acids, carbohydrates, and nucleotide bases b. Results: found L and D bases, which are often produced by animals c) Iron-Sulfur World Theory a. Simulated hydrothermal vents using CO (carbon monoxide) and KCN (potassium cyanide) produced amino acids b. Theory: life originated at hydrothermal vents c. Challenges: it is very hot, possibly too hot for cells d. The fourth theory (RNA World) derived from this theory  we are still missing lipids i. Potential explanation: lipids formed from minerals underneath vents d) RNA World a. RNA was the precursor to DNA (both enzyme and genetic storage material) b. RNA monomers have been produced spontaneously from simple molecules 3. What does organismal evolution look like across time? (list major evolutionary events and when they happened) Adaptation to the environment over billions years. Coming to deal successfully with changes in: oxygen levels, carbon dioxide levels, temperature extremes (hot and cold), ocean chemistry (pH, salinity, toxic chemicals), water availability, light intensity and spectral qualities, UV radiation. Characteristics of the First Cell: Prokaryotes Anaerobic as there was no oxygen in the atmosphere First came the common ancestor, then 3.8 billion years ago the prokaryotes evolved into two groups: Bacteria and Archaea Common ancestor of all species living today speciated into bacteria then further speciated into archaea and eukarya EXTINCTIONS: There have been five mass extinctions, but diversity has increased End-Permian-Triassic Mass Extinction: 252 million years ago 1. Drop in Sea Level (changed habitat of fauna) 2. Several Volcanic Eruptions (released CO2 which was toxic, trapped heat, decreased O) 3. Floods, Sea Levels increased i. Who survived? Only bottom-dwellers who could tolerate low O, “suffocation” when there is high CO2 and low O End-Triassic Mass Extinctions – 200 million years ago Rising CO2, falling pH, falling O2 (which is same story as above!) 4. Describe the main characteristics of prokaryotic cells. Simple, single celled organism Lacks a nucleus and membrane-bound organelles Not divided up on inside by membrane walls, instead consist of single open space Majority of its DNA is found in the nucleoid (central region of cell) and typically consists of a single large loop called a circular chromosome 0.1-5.0 micrometers and much smaller than eukaryotic cells “The life force” by Service (2013) questions: 1. In 1967, Colin Pittendrigh predicted that functional protocells would be created within a decade. Why hasn’t this happened? 2. In the early 1990’s Szostak moved away from research on telomeres into the world of RNA catalysts, why was his discoveries in this field so important to our understanding about how primitive life on earth started? 3. What are some challenges the Szortak lab still has to overcome to explain early life on earth? Need Mg2+ to copy template, without it too slow, but it was ripping it apart Kurihara et al. (2015) questions: This is a challenging paper with a lot of field-specific jargon, so let’s try to focus on the big-picture findings of this paper! 1. What was the general goal of this study? To examine/study/prove that the primitive soup “protocell” was a DNA-based cell, not RNA like previously thought. 2. What are the four phases in the self-proliferative cycle of a lab-generated giant vesicle? Ingestion Phase, Replication Phase, Maturity Phase, Division Phase 3. What kinds of environmental parameters are needed to stimulate these protocells to divide? “The mother of mass extinctions” by Erwin (1996) questions: 1. How much diversity was destroyed after the “mother of all extinctions”? What may be some advantages for plant and animal diversity after an extinction event? 2. How long did this extinction last? Was it fast or slow? 3. What percentage of invertebrates disappeared? How did this percentage compare to other extinctions? Which animal groups were hit the hardest? Why? 4. How was plant diversity affected during this time? 5. What do we think caused this mass extinction? What is the order of events that the author thinks brought on this mass extinction? Lecture #2: 1. Please describe the process of endosymbiosis. What is the evidence to support this evolutionary change? Earliest evidence of eukaryotic cells: 2.7 billion years ago How we got mitochondria and chloroplasts, which produce energy for the cell. (Dictionary definition: symbiosis in which one of the symbiotic organisms lives inside the other). It has to do with the evolution of a eukaryotic cell, as does compartmentalization (how we gained endoplasmic reticulum and nuclear envelope). Cyanobacteria started producing Oxygen, which was not a good thing for many organisms Process: Essentially a protobacteria was engulfed by a eukaryotic cell FIRST ENDOSYMBIOTIC EVENT  Mitochondria 1) A symbiotic relationship developed between an ancestral aerobic heterotrophic bacterial prokaryote (not an Archaea) and a eukaryotic cell. a. The bacteria could deal with Oxygen and provide ATP for the cell 2) The energy-producing aerobic prokaryote took up residence inside the engulfing eukaryotic cell but was not destroyed 3) The energy-producing aerobic prokaryote eventually became the mitochondrion. 4) Eventually, some of the genes from the mitochondrion were transferred to the nucleus. However, other genes remained becoming the mitochondrial DNA (Humans inherit only their mother’s mitochondrial DNA since only the nucleus of a sperm fertilizes the human egg. SECOND ENDOSYMBIOTIC EVENT  Chloroplast 1) Developed between ancestral autotrophic prokaryote (not an archaea) and a eukaryotic cell 2) The autotrophic prokaryote eventually became the chloroplast 3) Eventually some of the genes from the chloroplast were relocated to the nucleus but other genes remained in the chloroplast 4) Occurred after the endosymbiotic event of the mitochondrion as all photosynthetic eukaryotic cell have mitochondria Evidence: the fact that Eukaryotic cells are more closely related to Bacteria than Archaea m