DOCSLIB.ORG

The Science of Biology

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
The Science of Biology Chapter 1 The Science of Biology hp://www.bozemanscience.com/biology Section 1: What is Science? • The goal of science is to investigate and understand the natural world, to explain events in the natural world, and to use those explanations to make useful predictions. • Science - is an organized way of using evidence to learn about the natural world. Thinking Like A Scientist • Why won’t the car start? Thinking Like a Scientist • Observation - The process of gathering information about events or processes in a careful, orderly way. (Usually involves the senses, particularly sight and hearing.) • Data - Information gathered from observations. o Quantitative - Expressed as numbers o Qualitative - Expressed as characteristics Thinking Like a Scientist • Inference - A logical interpretation based on prior knowledge or experiences. Explaining and Interpreting the Evidence • After the initial observation, scientists will propose one or more hypothesis. • Hypothesis - A proposed scientific explanation for a set of observations o Often referred to as an educated guess” o Only useful if it can be tested Scientists generate hypotheses using prior knowledge, (what they already know); logical inference; and informed, creative imagination. Explaining and Interpreting the Evidence • Scientists often collaborate in teams to work on complex questions or problems. Science is a way of knowing • Science is a never ending process. • New tools, techniques, and discoveries can lead to new scientific understandings. • Look at the picture below…What might a scientist do with such a discovery? Science and Human Values • Today, scientists contribute information to discussions about health and disease, and about the relationship between human beings and the living and nonliving environment. Notebook #1 1. What does science study? 2. What is the difference between qualitative and quantitative data? 3. What is a hypothesis? 4. When trying to solve complex problems, how do scientists often work? Section 2: How Scientists Work • For thousands of years, people have noticed that living things have magically appeared from non-living things. o Maggots appear on dead animals or rotting meat. o Mice appear on piles of grain. o Beatles appear on cow dung. • Scholars from that era called this phenomenon Spontaneous Generation. Designing an Experiment • The maggot theory lasted until 1668 when an Italian physician, Francesco Redi, designed an experiment to test his hypothesis. • Redi believed that maggots were the larva form of house flies. To test this hypothesis, Redi designed the following experiment. Designing an Experiment A Controlled Experiment • Whenever possible, a hypothesis should be tested by an experiment in which only one variable is changed at a time. All other variables should be kept unchanged, or controlled. • This is called a controlled experiment. • Independent Variable (Manipulated Variable) - the variable that is deliberately changed (Gauze). • Dependent Variable (Responding Variable) - the variable that is observed (Maggots appear). Recording and Analyzing Results • Scientists must keep written records of their observations, or data, that occur during their experiment. • In the past, most results were written in notebooks or journals. They also could have drawn pictures like the following. • Today, records can be kept with computers, tablets, and other electronic devices. Drawing a Conclusion • Scientists use the data from an experiment to evaluate the hypothesis and draw a valid conclusion. • Was the hypothesis supported or not supported by the results? The Scientific MethoD Repeating Investigations • Many times after a scientist publishes their work, other scientist will retest their ideas. • In the mid 1700’s, an English scientist named John Needham tested Redi’s ideas using another organism called “animalcules” (Discovered by Anton van Leeuwenhoek). • Needham believed spontaneous generation could occur under the right conditions. • He sealed a bottle containing gravy and heated to kill any living thing. • Several days later, he examined the bottle and saw it was filled with activity. • He inferred “these little animals can only have come from the gravy.” hp://www.bozemanscience.com/scientific-methoD Spallanzani’s Test • Lazzaro Spallanzani read Redi and Needham’s work. He believed Needham did not heat the gravy enough and decided to do the following experiment. Fige 1-10 Spallanzani’s Experiment Gravy is boiled. Flask is Gravy is teeming open. with microorganisms. Gravy is boiled. Flask is Gravy is free of sealed. microorganisms. Pasteur’s Test • Another scientist named Louis Pasteur wanted to disprove spontaneous generation. He stated that Spallanzani’s experiment wasn’t valid because living things need air to survive. The sealed bottle of gravy prevented that. • Pasteur used a flask that had a curved neck which allowed air in but kept microorganisms out. Figure 1-11 Pasteur’s Experiment Broth is boiled. Broth is free of Curved neck Broth is microorganisms is removed. teeming with for a year. microorganisms. Notebook #2 1. What is spontaneous generation? Is it a scientific explanation that is well supported today? 2. What is a controlled experiment? 3. What is the difference between the independent variable and the dependent variable in an experiment? 4. Why is it important to repeat experiments? Section 3: Studying Life Interest Grabber Shells and Snowflakes How can we distinguish between living and nonliving things, such as a radiolarian (left) and a snowflake (right)? A radiolarian is a tiny living thing that is covered with a glasslike shell and lives in the ocean. A snowflake is a crystal made of frozen water. Interest Grabber (continued) Work with a partner to answer the following questions. 1. What are some similarities between the snowflake and the glass shell of the radiolarian? 2. What are some differences between the snowflake and the glass shell? 3. Would you classify the shell as a living thing or a nonliving thing? Explain your answer. Characteristics of Living Things • Living things… 1. Are made up of units called cells 2. Reproduce 3. Are based on a universal genetic code 4. Grow and develop 5. Obtain and use materials and energy 6. Respond to their environment 7. Maintain a stable internal environment (homeostasis) 8. Change over time Characteristics of Living Things Characteristic Examples Living things are made up of units called Many microorganisms consist of only a single cell. cells. Animals and trees are multicellular. Living things reproduce. Maple trees reproduce sexually. A hydra can reproduce asexually by budding. Living things are based on a universal Flies produce flies. Dogs produce dogs. Seeds from genetic code. maple trees produce maple trees. Living things grow and develop. Flies begin life as eggs, then become maggots, and then become adult flies. Living things obtain and use materials and Plants obtain their energy from sunlight. Animals energy. obtain their energy from the food they eat. Living things respond to their environment. Leaves and stems of plants grow toward light. Living things maintain a stable internal Despite changes in the temperature of the environment. environment, a robin maintains a constant body temperature. Taken as a group, living things change Plants that live in the desert survive because they have over time. become adapted to the conditions of the desert. Characteristics of Living Things • Cell – collection of living matter enclosed by a barrier that separates the cell from its surroundings • Sexual reproduction – cells from two parents unite to produce the first cell of the new organism • Asexual reproduction – process by which a single parent reproduces by itself • Metabolism – combination of chemical reactions through which an organism builds up or breaks down materials • Stimulus – signal to which an organism responds • Homeostasis – process by which organisms maintain a relatively stable internal environment • Evolution – change in a kind of organism over time Figure 1-21 Levels of Organization Levels of Organization Biosphere The part of Earth that contains all ecosystems Biosphere Ecosystem Community and its nonliving surroundings Hawk, snake, bison, prairie dog, grass, stream, rocks, air Community Populations that live together in a defined area Hawk, snake, bison, prairie dog, grass Population Group of organisms of one type that live in the same area Bison herd Figure 1-21 Levels of Organization continued Organism Individual living thing Bison Tissues, organs, Groups of and organ systems Cells Nervous tissue Brain Nervous system Smallest functional Cells unit of life Nerve cell Groups of atoms; smallest unit of Molecules most chemical compounds Water DNA Notebook #3 1. What are the 8 characteristics of living things? 2. What is a cell? 3. What is the difference between sexual and asexual reproduction? 4. What is metabolism? 5. What is homeostasis? Section 4: Tools and Procedures A Common Measurement System • Most scientists use the metric system when collecting data and performing experiments. • Metric system – decimal system of measurement based on certain physical standards and on multiples of 10 Metric System Microscopes • Light microscopes – produce magnified images by focusing visible light rays o Compound light microscope – uses two lenses to form an image • Electron microscopes – produce magnified images by focusing beams of electrons o Transmission electron microscope (TEM) – shines a beam of electrons through a soecimen o Scanning electron microscope (SEM) – scan a narrow beam of electrons back and forth across the surface of the specimen Laboratory Techniques • Cell culture – group of cells grown in a nutrient solution from a single, original cell • Cell fractionation – technique in which cells are broken into pieces and the different cell parts are separated Notebook #4 1. What is the metric system and why have scientists around the world agreed to use it? 2. What is the difference between a light microscope and an electron microscope? 3. What is a cell culture? 4. What is cell fractionation? .
Load more

Recommended publications
  • La Logica Del Vivente in Maupertuis: Dall’Attrazione Newtoniana Al Determinismo Psicobiologico
    La logica del vivente in Maupertuis: dall’attrazione newtoniana al determinismo psicobiologico Federico Focher (Istituto di Genetica Molecolare “Luigi Luca Cavalli Sforza”, CNR, Pavia) Dopo aver rilanciato con successo la teoria epigenetica della generazione, reinterpretata alla luce dell’attrazione newtoniana e delle affinità chimiche (Vénus physique, 1745), Pierre-Louis Moreau de Maupertuis (1698-1759) approfondì le proprie indagini teoretiche nel campo della genesi degli organismi e delle specie nel Système de la Nature (1754). In quest’opera, al fine di conciliare il postulato di oggettività della scienza - che respinge il ricorso alle cause finali - con le evidenti proprietà teleonomiche degli esseri viventi, e riconoscendo nel contempo inadeguati a tale scopo i pur originali principii meccanicistici avanzati nella Vénus physique, Maupertuis propose un’ardita teoria panpsichista del vivente, di ispirazione spinoziana. Postulando quindi la materia viva, dotata di istinto e di sentimento, Maupertuis immaginò che una qualche forma di intelligenza o di memoria psichica, associata alla materia, dirigesse lo sviluppo dei viventi. Alla luce delle recenti scoperte della biologia, l’originale determinismo psicobiologico avanzato da Maupertuis nel Système de la Nature appare una geniale intuizione della logica dei processi genetici ed evolutivi. Keywords: Maupertuis, teleonomia, scienze della vita, storia della biologia, informazione genetica, panpsichismo, Buffon. Introduzione Mezzo secolo dopo la scoperta della legge della gravitazione universale
    [Show full text]
  • The Spontaneous Generation Controversy (340 BCE–1870 CE)
    270 4. Abstraction and Unification ∗ ∗ ∗ “O`uen ˆetes-vous? Que faites-vous? Il faut travailler” (on his death-bed, to his devoted pupils, watching over him). The Spontaneous Generation Controversy (340 BCE–1870 CE) “Omne vivium ex Vivo.” (Latin proverb) Although the theory of spontaneous generation (abiogenesis) can be traced back at least to the Ionian school (600 B.C.), it was Aristotle (384-322 B.C.) who presented the most complete arguments for and the clearest statement of this theory. In his “On the Origin of Animals”, Aristotle states not only that animals originate from other similar animals, but also that living things do arise and always have arisen from lifeless matter. Aristotle’s theory of sponta- neous generation was adopted by the Romans and Neo-Platonic philosophers and, through them, by the early fathers of the Christian Church. With only minor modifications, these philosophers’ ideas on the origin of life, supported by the full force of Christian dogma, dominated the mind of mankind for more that 2000 years. According to this theory, a great variety of organisms could arise from lifeless matter. For example, worms, fireflies, and other insects arose from morning dew or from decaying slime and manure, and earthworms originated from soil, rainwater, and humus. Even higher forms of life could originate spontaneously according to Aristotle. Eels and other kinds of fish came from the wet ooze, sand, slime, and rotting seaweed; frogs and salamanders came from slime. 1846 CE 271 Rather than examining the claims of spontaneous generation more closely, Aristotle’s followers concerned themselves with the production of even more remarkable recipes.
    [Show full text]
  • New Yorkers Had Been Anticipating His Visit for Months. at Columbia
    INTRODUCTION ew Yorkers had been anticipating his visit for months. At Columbia University, where French intellectual Henri Bergson (1859–1941) Nwas to give twelve lectures in February 1913, expectations were es- pecially high. When first approached by officials at Columbia, he had asked for a small seminar room where he could directly interact with students and faculty—something that fit both his personality and his speaking style. But Columbia sensed a potential spectacle. They instead put him in the three- hundred-plus-seat lecture theater in Havemeyer Hall. That much attention, Bergson insisted, would make him too nervous to speak in English without notes. Columbia persisted. So, because rhetorical presentation was as impor- tant to him as the words themselves, Bergson delivered his first American lec- ture entirely in French.1 Among the standing-room-only throng of professors and editors were New York journalists and “well-dressed” and “overdressed” women, all fumbling to make sense of Bergson’s “Spiritualité et Liberté” that slushy evening. Between their otherwise dry lines of copy, the reporters’ in- credulity was nearly audible as they recorded how hundreds of New Yorkers strained to hear this “frail, thin, small sized man with sunken cheeks” practi- cally whisper an entire lecture on metaphysics in French.2 That was only a prelude. Bergson’s “Free Will versus Determinism” lec- ture on Tuesday, February 4th—once again delivered in his barely audible French—caused the academic equivalent of a riot. Two thousand people attempted to cram themselves into Havemeyer. Hundreds of hopeful New Yorkers were denied access; long queues of the disappointed snaked around the building and lingered in the slush.
    [Show full text]
  • On the Trail of Digestion
    Middle School Science Eating to Live and Living to Eat Movement of Energy Through Living and Non-living Systems; Student Resource Matter, Its Structure and Changes; From Atoms to the Universe Name On the Trail of Digestion Read the following section on the history of medical science and answer the questions: January 17, 2002 SCoPE SC070104 Page 1 of 6 Middle School Science Eating to Live and Living to Eat Movement of Energy Through Living and Non-living Systems; Student Resource Matter, Its Structure and Changes; From Atoms to the Universe Spallanzani Lazzaro Spallanzani lived in the second half of the 18th Century. You may remember Spallanzani’s experiments on spontaneous generation. His work on digestion is also famous. In Spallanzani’s time, people knew that the stomach was a strong muscle that could grind and mash food. Investigations of bodies told scientists that. But Spallanzani believed that the stomach also held a chemical process. He began his studies using his own falcons. He would feed the falcons small pieces of meat attached firmly to a string, and when the meat had been in the birds stomachs for some time, he would remove it. (You might remember that birds regurgitate quite easily, and some birds feed their babies this way.) Spallanzani believed that digestion was a chemical process. Another noted scientist, Rene Reaumur disagreed. He wrote: "the gastric juice has no more effect out of the living body in dissolving or digesting the food than water, mucilage, milk, or any other bland fluid." Reaumur claimed to have done experiments to see if digestion could take place outside the body as well as in it.
    [Show full text]
  • Key Answers) 1
    II PUC BIOLOGY ASSIGNMENT – 11 (KEY ANSWERS) 1. With a schematic representation, explain the life cycle of HIV. (5) The HIV (retro virus) gains entry into the body through sexual contact with an infected person. The virus then enters macrophages. In macrophages RNA genome of the virus replicates to form viral DNA with the help of reverse transcriptase enzyme. The viral DNA is incorporated into the host DNA and direct infected host cells (macrophages to produce viral particle. Therefore macrophages act as HIV factory. Simultaneously HIVB enters into T-lymphocytes (TH – Helper T-cells) where it replicates and produces progeny viruses. The progeny viruses released into the blood, attack the other helper T-lymphocytes. This is repeated leading to progressive decrease in the number of helper T – lymphocytes in the body. Due to decrease in the number of T – lymphocytes, the person suffers from infections such as Mycobacterium, viruses, fungi and even parasites like Toxoplasma. The person becomes immune deficient. This lead to his death. 2. The cells of malignant tumors are considered as dangerous. – Give reason. (1) Malignant tumors grow very rapidly, damage surrounding normal tissues and spread to other parts through blood stream where they get lodged and transform the normal cells into cancer cells. ASC INDEPENDENT P. U. COLLEGE Page 1 of 6 3. Explain the salient features of double helix model of DNA. (5) WATSON AND CRICK MODEL OF DNA (Double helix model) * Rosalind Franklin is best known for her work on the X-ray diffraction images (1952) of DNA, which led to the discovery of the DNA double helix model (1953) for which Francis Crick, James Watson, and Maurice Wilkins shared the Nobel Prize in Physiology or Medicine in 1962.
    [Show full text]
  • History of Microbiology: Spontaneous Generation Theory
    HISTORY OF MICROBIOLOGY: SPONTANEOUS GENERATION THEORY Microbiology often has been defined as the study of organisms and agents too small to be seen clearly by the unaided eye—that is, the study of microorganisms. Because objects less than about one millimeter in diameter cannot be seen clearly and must be examined with a microscope, microbiology is concerned primarily with organisms and agents this small and smaller. Microbial World Microorganisms are everywhere. Almost every natural surface is colonized by microbes (including our skin). Some microorganisms can live quite happily in boiling hot springs, whereas others form complex microbial communities in frozen sea ice. Most microorganisms are harmless to humans. You swallow millions of microbes every day with no ill effects. In fact, we are dependent on microbes to help us digest our food and to protect our bodies from pathogens. Microbes also keep the biosphere running by carrying out essential functions such as decomposition of dead animals and plants. Microbes are the dominant form of life on planet Earth. More than half the biomass on Earth consists of microorganisms, whereas animals constitute only 15% of the mass of living organisms on Earth. This Microbiology course deals with • How and where they live • Their structure • How they derive food and energy • Functions of soil micro flora • Role in nutrient transformation • Relation with plant • Importance in Industries The microorganisms can be divided into two distinct groups based on the nucleus structure: Prokaryotes – The organism lacking true nucleus (membrane enclosed chromosome and nucleolus) and other organelles like mitochondria, golgi body, entoplasmic reticulum etc. are referred as Prokaryotes.
    [Show full text]
  • Regeneration According to Spallanzani
    DEVELOPMENTAL DYNAMICS 238:2357–2363, 2009 REVIEWS–A PEER REVIEWED FORUM Regeneration According to Spallanzani Panagiotis A. Tsonis* and Timothy P. Fox In this report, we elaborate on a letter that Spallanzani wrote to Bonnet reporting his findings on regeneration in worms, snails, tadpoles, and salamanders. The letter (original in French and translated in English; see Supplementary Material, which is available online) was written to discuss whether or not regeneration in these animals supports Bonnet’s theory on germs. The letter includes several drawings by Spallanzani, which were not published in the Prodromo, his book on Animal Reproduction. Spallanzani made important observations, which he described with considerable detail, but overall he was unable to confidently support Bonnet’s theory. This letter reflects the way of thinking in the 18th century that shaped the important scientific fields of regeneration and reproduction. Developmental Dynamics 238:2357–2363, 2009. © 2009 Wiley-Liss, Inc. Key words: Spallanzani; regeneration; animal reproduction Accepted 4 June 2009 INTRODUCTION of Creation. On the contrary, epigene- 1740 and on worm regeneration in sis allowed space for questioning the 1744 (Savioz, 1948; Dinsmore, 1991) Rooted in Aristotelian philosophy, the role of God. As expected when the first shocked the scientific world. Re´aumur belief that lower animals were gener- experiments in the 18th century re- and Bonnet were preformationists ated spontaneously from decay pre- vealed the regenerative power of ani- and, in fact, Re´aumur believed that vailed until the 17th century when mals, these two competing theories germs were contained within parts re- Redi in 1668 carried out well-con- trolled experiments that provided the were called upon to explain this new sponsible for regeneration.
    [Show full text]
  • Oddly Enough, Vallisnieri's Positionat Padua Was Later to Be
    THE SHADOWED SIDE OF SPALLANZANI JAMES B. HAMILTON An historical study of a man tends to emphasize certain char- acteristics to the exclusion of others. This, of course, enables the reader to gain more readily a mental picture, but the question arises as to whether or not a well-rounded conception can be obtained from consideration of a limited number of traits. Lazaro Spal- lanzani has been indelibly traced as a religious scientist whose force of character dominated the scientific world of his time. That is true enough, but fails in the presentation of a balanced perspective. It may be worth while, then, to dispel part of the shadows that dim his character, to portray a tricky, clever man, every bit as prone to fault as other men, one who gained his ends by craftiness when "strong- handed" means failed-a sly, greedy, yet likeable scientist who placed his work foremost. As a boy, Spallanzani exhibited the wiliness that he was to fall back on in later years at times when straight-forward domineering met with obstacles. His father, a lawyer, set the carefree son to follow in paternal footsteps, but the young lad had other indinations, slipping outside to while away the day in skipping stones over nearby waters. The story is told that while wondering what caused the stones to skip, he pondered how he could escape an approaching life of jurisprudence. An idea occurred. He left off skipping stones to study Logic, Greek, and French. After acquiring somewhat of a background, he artfully laid his plight before the great teacher, Vallisnieri, a native of Spallanzani's birthplace, Scandiano, Italy.
    [Show full text]
  • De Felici1371.Pm4
    Int. J. Dev. Biol. 44: 515-521 (2000) The rise of Italian embryology 515 The rise of embryology in Italy: from the Renaissance to the early 20th century MASSIMO DE FELICI* and GREGORIO SIRACUSA Department of Public Health and Cell Biology, University of Rome “Tor Vergata”, Rome, Italy. In the present paper, the Italian embryologists and their main the history of developmental biology were performed (see contributions to this science before 1900 will be shortly reviewed. "Molecularising embryology: Alberto Monroy and the origins of During the twentieth century, embryology became progressively Developmental Biology in Italy" by B. Fantini, in the present issue). integrated with cytology and histology and the new sciences of genetics and molecular biology, so that the new discipline of Embryology in the XV and XVI centuries developmental biology arose. The number of investigators directly or indirectly involved in problems concerning developmental biol- After the first embryological observations and theories by the ogy, the variety of problems and experimental models investi- great ancient Greeks Hippocrates, Aristotle and Galen, embryol- gated, became too extensive to be conveniently handled in the ogy remained asleep for almost two thousand years. In Italy at the present short review (see "Molecularising embryology: Alberto beginning of Renaissance, the embryology of Aristotle and Galen Monroy and the origins of Developmental Biology in Italy" by B. was largely accepted and quoted in books like De Generatione Fantini, in the present issue). Animalium and De Animalibus by Alberto Magno (1206-1280), in There is no doubt that from the Renaissance to the early 20th one of the books of the Summa Theologica (De propagatione century, Italian scientists made important contributions to estab- hominis quantum ad corpus) by Tommaso d’Aquino (1227-1274) lishing the morphological bases of human and comparative embry- and even in the Divina Commedia (in canto XXV of Purgatorio) by ology and to the rise of experimental embryology.
    [Show full text]
  • Galileo's Microscope Test
    Galileo's microscope Test This is the Test material for verifying the contents of the History and Explore sections of the web application. Texts prepared by the Institute and Museum of the History of Science in Florence. Why a test? The structured test consists of 40 multiple-choice questions designed to verify the main content of the application. Galileo's microscope was created for the purpose of furnishing, in an attractive but strictly scientific way, a great body of information on microscopy in the 17 th and 18 th centuries. To reinforce the educational effect, it has been deemed useful to provide a tool of evaluation to be used by teachers, or of self-evaluation for others. For each question, reference is made to the section in which the answer can be found, allowing users the chance to verify the content. Standard timing for the answers is generally 1 minute for each multiple-choice question (34) and 30 seconds for each true/false question (6). The whole test should thus be completed within 37 minutes. 2 1. During what period was the microscope invented? a) □ In the late 15 th – early 16 th century. b) □ Around the middle of the 16 th century. c) □ In the late 16 th – early 17 th century . d) □ Around the middle of the 17 th century. Reference: HISTORY section – The compound microscope. 2. During what period was the “Galilean” microscope constructed (IMSS inv. 3429)? a) □ First half of the 17 th century. b) □ Second half of the 17 th century . c) □ First half of the 18 th century.
    [Show full text]
  • A. Antonie Van Leeuwenhoek B. Edward Jenner C. Francesco Redi
    Exam 1, Micr-22, C. Briggs, ver 9.14 (scaled to 100pts) Name: ___________________________ Tip: Answer the questions you know first. At least guess on everything before you turn this in. Words, drawings, charts – all are welcome. 1. Please write a properly-formatted species name. 1pt 2. Please match the following individuals to their major microbiological contribution. 6pts ____ Challenged idea of spontaneous generation by showing that maggots A. Antonie van Leeuwenhoek B. Edward Jenner from fly eggs. C. Francesco Redi ____ Helped popularize smallpox variolation. D. Lazzaro Spallanzani E. Louis Pasteur ____ Improved microscopes, one of first to observe microorganisms. F. Robert Koch ____ Challenged idea of spontaneous generation by showing that boiled and G. Lady Mary Wortley Montague long-necked containers did not grow microbes. ____ Challenged idea of spontaneous generation by showing that boiled and sealed containers did not grow microbes. ____ Helped develop the smallpox vaccine. ____ Developed rules to determine the causes of particular infectious diseases. 3. Name two emerging diseases. 2pts 4. What are two reasons that diseases are still emerging? 2pts 5. Please identify a major benefit and a major drawback / cost of using the following types of microscope or stain. 4pts Benefit Drawback / Cost (a) Fluorescence (b) Gram stain (c) Brightfield (d) Scanning electron 6. What is a difference between a simple stain and a differential stain? 1pt 7. For the following structures, please indicate whether this can be found in a prokaryotic cell (“pro”), in a eukaryotic cell (“euk”), or in both (“both”). 5pts _____ DNA _____ Rotating flagella _____ Rough endoplasmic reticulum _____ RNA _____ Enzymes _____ Plasma membrane _____ Ribosomes _____ Peptidoglycan _____ Cell wall _____ Nucleus 8.
    [Show full text]
  • Lazzaro Spallanzani Y La Inseminación Artificial
    EDITORIALES ISSN 0025-7680483 EDITORIAL MEDICINA (Buenos Aires) 2009; 69: 483-486 Lazzaro Spallanzani y la inseminación artificial Hace 30 años nació el primer bebé de probeta y el aniversario indujo la reflexión sobre sus conse- cuencias sobre la biología y la ética humanas1. Esta vez recordaremos el primer experimento exitoso de inseminación artificial en un mamífero, ocu- rrido hace más de 200 años. El experimentador fue el abate Lazzaro Spallanzani. Spallanzani había tenido éxito en sus experimentos de inseminación artificial realizados en anfibios: ovíparos de fecundación externa)2a. El impensado suceso en la fecundación artificial del gusano de seda (ovíparo de fecundación interna) le dio el coraje necesario para intentar la fecundación en mamíferos: vivíparos fecundados en el seno materno, gato, oveja, perro. La idea bullía en su cabeza y la hizo conocer en un artículo titulado Fecondazione artificiale publicado en el Prodromo della nuova Enciclope- dia Italiana en 1779. El éxito, real o supuesto, con el gusano de seda lo indujo a probar en una perra. En el relato del experimento seguiremos casi textualmente a Spallanzani2b. La perra era una perra de aguas (Canis aquaticus, pile crespo longo, instar. ovis. LINNÉ, Sist. Nat.) [¿Una spaniel lombarda?] que ya había tenido una parición. Spallazani la encerró en una pieza con llave apenas sospechó que llegaba al estro. El mismo le daba de beber y comer, y guardaba la llave. A los 13 días del encierro la perra dio señales inequívocas del estro (“tumefacción de las partes externas de la generación, un derrame tenue de sangre que de ellas goteaba”).
    [Show full text]