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Introduction to Cell Biology Course #72108 (2011) 7 weeks (14 meeting) Cell Biology, Molecular Biology Amir Eden Dep. Of Animal & Cell Biology Life Science Institute Room: 3-564 Phone: 6584981 Course website: http://moodle.huji.ac.il Enter course # 72108 http://moodle.huji.ac.il 1 Reference • Life: The Science of Biology, Seventh Edition, by William K. Purves, David Sadava, Gordon H. Orians, and H. Craig Heller. Free website: http://bcs.whfreeman.com/thelifewire/ Animated Tutorials Activities and Flashcards Interactive Quizzes Online Quizzes Suggested Readings Glossary by Chapters Glossary Math for Life Survival Skills 1 Reference Biology, 8th Edition By: Campbell & Reece 1 • Essential Cell Biology, Second Edition Bruce Alberts, Alexander Johnson, Julian Lewis, Martin Raff, Dennis Bray, Karen Hopkin, Keith Roberts, Peter Walter • Garland 2003 Reference 1 Aim • Introduction to basic principles of biology at all levels (Molecular Cellular, Organisms) • The lectures are designed for first year students in biology having heterogeneous previous knowledge • More “in-depth” course in cell biology called: “Advanced Cell Biology” (72373) will be given in second year. 1 How to succeed in this course • Read, Read & Read! Comprehensive knowledge is achieved only by reading the books and listening to the lectures. • Understand what you read. • Lectures can be downloaded from the moodle site, and most material can be read in text-books (Academon / Library). • Important concepts are stated on the slides. Make sure you remember and understand these statements • Do not hesitate to ask questions (raise your hand, ask me after the class or at my office) 1 How to succeed in this course NEW: • Video recording of lectures NEW: • Online exercise Introduction to Biology, The Science of life 1 An Evolutionary Framework for Biology Outline of today’s talk • What is Life? • Biological Evolution: Changes over Billions of Years • The Evolutionary Tree of Life • Major Events in the History of Life on Earth • Levels of Organization of Life • Biology is a Science 1 What is Life? • Life can be defined as an organized (genetic) unit capable of metabolism, reproduction, and evolution. 1 What is Life? Metabolism • An organism’s metabolism is its total chemical activity. • Metabolism involves thousands of individual chemical reactions. • These reactions must be coordinated for an organism to function. • The internal environment of an organism must remain within a given range of physical and chemical conditions for that organism to remain healthy. • Homeostasis is the maintenance of a relatively stable internal condition, such as temperature. 1 What is Life? Reproduction & Evolution • Reproduction can be by duplication or by mating. 1 What is Life? Reproduction & Evolution • Reproduction with variation is a major characteristic of life. 1 What is Life? Reproduction & Evolution • The combination of reproduction and duplication errors (leading to variation) results in biological evolution. • Variations in the physical environment have helped drive the diversification of life. 1 What is Life? Reproduction & Evolution • The differences among living things that enable them to live in different kinds of environments and adopt different lifestyles are called adaptations. 1 Microbial adaptation Hot springs Possible microfossil in Martian meteorite ALH84001 Deep vent 1 Biological Evolution: Changes over Billions of Years • Count George-Louis Leclerc de Buffon (1707– 1788) wrote Natural History of Animals and suggested the possibility of evolution. • Buffon observed the similarity of different mammals’ limbs and suggested that the limbs of mammals were inherited from a common ancestor. 1 Biological Evolution: Changes over Billions of Years • Jean Baptist de Lamarck, a student of Buffon, suggested a mechanism: With continued use, some structures become larger from generation to generation, whereas others become smaller from disuse • Though Lamarck made important contributions, this theory of acquired structures is not accepted by scientists today. 1 Biological Evolution: Changes over Billions of Years • In 1858, both Charles Darwin and Alfred Russel Wallace independently developed and proposed the theory of evolution by natural selection: • The world is ancient • Living things evolve - ancestral forms were different from organisms we find today • Differences or variations among individuals influence how well those individuals survive and reproduce in changing environments. • Traits that increase the probability that their bearers will survive and reproduce are passed on to the next generation. According to survival and reproductive success • Two major forces: Variation + Selection 1 What is Life? Reproduction & Evolution • The differences among living things that enable them to live in different kinds of environments and adopt different lifestyles are called adaptations. If variation happens to produce a useful change, Selection will fix it in the right environment 1 The Evolutionary Tree of Life • All organisms on Earth today descended from an original unicellular organism that lived around 4 billion years ago. • Major evolutionary events have led to more complex organisms with larger quantities of information and more complex mechanisms for using it. • Genetically independent groups, called species, have evolved. (~30 million sp.) • All organisms alive today have survived because of appropriate adaptations to their environments. A Provisional Tree of Life Prokaryotic cells Eukaryotic cells Autotrophs = self-feeders Protists mostly unicellular Heterotrophs= other feeders Molds, mushrooms, yeasts Heterotrophs= other feeders Kingdom Kingdom Kingdom Figure 1.3 Life’s Calendar Life’s Calendar Earth Chemical evolution Origin of Life Forms 3.8 Billion (Cells) 4.5 Billion years ago years ago Oldest (microbial) fossils Photosynthesis Evolves 2.5 Billion years ago Biological evolution Oxygen, Ozone Eukaryotic cells evolve Multicellular Organisms 1 Billion Years ago Abundant life 1 day = 150 million years 1 week = 1 billion years 1 Life’s Calendar Earth forms Origin of Life Oldest fossils Photosynthesis evolves Eukaryotic cells Multicellular Abundant life Cell specialization Sexual reproduction Aquatic life Abundant fossils First land plants First land animals Forests Insects Dinosaurs dominant First mammals Birds Flowering plants Rise of Mammals First hominids Homo sapiens 1 Life’s Calendar Earth forms Origin of Life Oldest fossils Photosynthesis evolves Eukaryotic cells Recorded history fills the last 5 seconds Modern humans of day 30. appeared in the last 10 minutes of day 30. Multicellular Abundant life Aquatic life Abundant fossils First land plants First land animals Forests Insects First mammals Dinosaurs dominant Birds Flowering plants Rise of Mammals 1 Major Events in the History of Life on Earth • Life arose from nonlife. • Chemical evolution led to the appearance of life about 4 billion years ago. • Random inorganic chemical interactions eventually produced molecules that had the property of acting as templates to form similar molecules. • Around 3.8 billion years ago certain molecules became enclosed in compartments, or cells. • Cells capture energy and replicate themselves, two fundamental characteristics of life. • For 2 billion years, all organisms were unicellular (prokaryotes), confined to the oceans. • About 2.5 billion years ago some prokaryotes acquired the ability to photosynthesize. • The energy of sunlight was captured, and oxygen was generated as a waste product. • Oxygen increased in concentration in the atmosphere, making aerobic metabolism possible. • Another effect of oxygen was O3 (ozone) accumulation in the upper atmosphere. • Ozone has the property of preventing excess ultraviolet light from the sun from reaching Earth. • Around 800 million years ago, ozone accumulation shielded the landmass from radiation enough to allow the movement of organisms to land. • Some prokaryotic cells became large enough to attach, engulf, and digest smaller cells. • About 1.5 billion years ago, some cells had surviving smaller cells within them: These were early eukaryotic cells. 1 Major Events in the History of Life on Earth • Two developments made the evolution of multicellular organisms possible: The ability of a cell to change its structure and function to meet the challenges of a changing environment The ability of cells to stick together after they have divided and to act in a coordinated manner • Once organisms became multicellular, it became possible for certain cells to specialize. • Sexual recombination, the combining of genes from two cells, appeared early in the evolution of life. • Sex increased the rate of evolution: Organisms that exchange genetic information produce offspring that are genetically variable. Because environments are constantly changing, organisms that produce variable offspring have an advantage over those that produce genetically identical clones. 1 Levels of Organization of Life • Biology can be visualized as a hierarchy of units that include molecules, cells, tissues, organs, organisms, populations, communities, and the biosphere. • To understand organisms, biologists must study them at all levels of organization, from low to high. 1 From Molecules to the Biosphere: The Hierarchy of Life Atoms are the basic building blocks of all matter. Atoms Molecule Molecules are made up of atoms. Molecules in turn can be organized into cells. 1 From Molecules to the Biosphere: The Hierarchy of Life Cells of many types are the working components of living organisms. Cell (Neuron) 1 From Molecules to the Biosphere: The Hierarchy of Life A tissue is a group of many cells with similar and coordinated functions. Tissue (ganglion) 1 From Molecules to the Biosphere: The Hierarchy of Life Organs combine several tissues that function together. Organs form systems, such as the nervous system. Organ (brain) 1 From Molecules to the Biosphere: The Hierarchy of Life An organism is a recognizable, self-contained individual made up of organs and organ systems. Organism (fish) 1 From Molecules to the Biosphere: The Hierarchy of Life A population is a group of many organisms of the same species. Population (school of fish) 1 From Molecules to the Biosphere: The Hierarchy of Life Communities consist of populations of many different species. Community (coral reef) 1 From Molecules to the Biosphere: The Hierarchy of Life Biological communities exchange energy with one another, combining to create the biosphere of Earth. Biosphere From Molecules to the Biosphere Full understanding crosses levels (Pesticides, Herbicides, Prozac ) • Requires: Engineering Computing Mathematics Statistics Chemistry Physics 1 Biology is a Science • The hypothesis-prediction (H–P) system - a conceptual tool for scientific research: Making observations Asking questions Forming hypotheses, or tentative answers to the questions Making predictions based on these hypotheses Testing the predictions by making additional observations or conducting experiments 1 The scientific method • Gastritis (Ulcer) Using the comparative & experimental methods to Test a Hypothesis The Nobel Prize in Physiology or Medicine 2005 Barry J. Marshall J. Robin Warren "for their discovery of the bacterium Helicobacter pylori and its role in gastritis and peptic ulcer disease" 1 The scientific method • Step 1: Making observations: Scientists observed bacteria in the stomach Scientists isolated and grew a bacterium that lives in the acidic environment of the human stomach Helicobacter pylori 1 The scientific method • Step 2: Asking questions: Are these good or bad bacteria? Are they important in Gastritis (Ulcer)? 1 The scientific method • Steps 3 and 4: Formulating hypotheses and making predictions: • Hypothesis: Helicobacter pylori is causing Ulcer • Predictions: • Prediction I: Patients with ulcer should have the bacterium • Prediction II: Infection with the bacterium should cause ulcer • Prediction III: Killing the bacterium should cure ulcer 1 Comparative method for testing a hypothesis • Most tests of hypotheses are of two types: Controlled experiments The comparative method • Step 5: Testing hypotheses: Prediction I: Patients with ulcer should have the bacterium comparative study Screen healthy people and people with Ulcer for Helicobacter pylori 1 Controlled experiment for testing a hypothesis • Prediction II: Infection with the bacterium should cause ulcer • Prediction III: Killing the bacterium should cure ulcer Controlled experiment: Infect a person with the bacterium and see if he develops Gastritis or Ulcer Give the person antibiotics to kill the bacteria and see if he is cured 1 Biology is a Science The H-P method is self correcting: • If the results of continued testing support the hypothesis, it may come to be considered a theory. • If the results do not support the hypothesis, it may be modified or abandoned. • Reproducibility is important Using controlled experiments to Test a Hypothesis • Jean Baptist de Lamarck suggested: With continued use, some structures become larger from generation to generation, whereas others become smaller from disuse Using controlled experiments to Test a Hypothesis • The case of the midwife toad by Arthur Koestler • 1920s an Austrian scientist named Paul Kammerer reported that midwife toads forced to mate in the water developed pads within a few generations 1 Biology is a Science • It is important to distinguish science from nonscience. • Science begins with observations and the formulation of hypotheses that can be tested and that will be rejected if significant contrary evidence is found. 1 Biology is a Science The study of biology has major implications for human life. • Currently, biological science is positioned at the forefront of many ethical, ecological, social, and medical challenges and dilemmas. In-Vitro Fertilization Viagra Global warming Cloning Forensics 1 Please recall or learn from book • Atom, Atom structure, Proton, Neutron, Electron • Elements, Periodic table, Isotopes, Orbitals • Molecules,Chemical bonds & interactions • Isomers, Optical isomers • Chemical reactions, Reactants, Products, Bond energy • Mole, Molar • pH, Buffers Chapter 2 in “Life” or in “Biology” or in “Cell Biology”