A Case Study written by Jackson David Reynolds, written in the style of the National Center for Case Study Teaching in Science (NCCSTS): http://sciencecases.lib.buffalo.edu/...
University of North Georgia, Gainesville, GA, USA
Spring 2016
This presentation you will get how the cell theory developed.
Robert Hooke observed cells in cork and coined the term "cells”.
Anton Van Leeuwenhoek observed first living cells under the simple microscope.
Matthias Schleiden (1838) German lawyer turned botanist, concluded that, despite differences in the structure of various tissues, plants were made of cells and that the plant embryo arose from a single cell.
In 1839, Theodor Schwann, a German zoologist and colleague of Schleiden’s, published a comprehensive report on the cellular basis of animal life. Schwann concluded that the cells of plants and animals are similar structures.
By 1855, Rudolf Virchow, a German pathologist concluded that
“Omnis cellula e cellula”- new cells are formed only from pre-existing cells.
All organisms are composed of one or more cells.
2) The cell is the structural unit of life.
3) Cells can arise only by division from a pre-existing cell
This presentation you will get how the cell theory developed.
Robert Hooke observed cells in cork and coined the term "cells”.
Anton Van Leeuwenhoek observed first living cells under the simple microscope.
Matthias Schleiden (1838) German lawyer turned botanist, concluded that, despite differences in the structure of various tissues, plants were made of cells and that the plant embryo arose from a single cell.
In 1839, Theodor Schwann, a German zoologist and colleague of Schleiden’s, published a comprehensive report on the cellular basis of animal life. Schwann concluded that the cells of plants and animals are similar structures.
By 1855, Rudolf Virchow, a German pathologist concluded that
“Omnis cellula e cellula”- new cells are formed only from pre-existing cells.
All organisms are composed of one or more cells.
2) The cell is the structural unit of life.
3) Cells can arise only by division from a pre-existing cell
A presentation by Thatayaone Ezekiel Dinama, Kago Relaeng and Michael Moseneke made to the Cardiff Sixth Form College A-Level BioMedical Society on the amazing discovery of the G-Quadruple structure of DNA. The discovery has many unfathomable potential benefits as far as health is concerned. Being interested in studying Medicine (Clinical or Academic) I found it a really intriguing research topic of recent times.
INTRODUCTION TO CELLS
INTRODUCTION TO CELL THEORY
HISTORY
FORMULATION OF CELL THEORY
CLASSICAL CELL THEORY
DRAWBACKS OF CLASSICAL THEORY
MORDEN CELL THEORY
EXCEPTION OF CELL THEORY
SIGNIFICANCE OF CELL THEORY
HOW HAS THE CELL THEORY BEEN USED
CONCLUSION
A presentation by Thatayaone Ezekiel Dinama, Kago Relaeng and Michael Moseneke made to the Cardiff Sixth Form College A-Level BioMedical Society on the amazing discovery of the G-Quadruple structure of DNA. The discovery has many unfathomable potential benefits as far as health is concerned. Being interested in studying Medicine (Clinical or Academic) I found it a really intriguing research topic of recent times.
INTRODUCTION TO CELLS
INTRODUCTION TO CELL THEORY
HISTORY
FORMULATION OF CELL THEORY
CLASSICAL CELL THEORY
DRAWBACKS OF CLASSICAL THEORY
MORDEN CELL THEORY
EXCEPTION OF CELL THEORY
SIGNIFICANCE OF CELL THEORY
HOW HAS THE CELL THEORY BEEN USED
CONCLUSION
Answer the following questions from the Article belowExercise #1..pdfarjunstores123
Answer the following questions from the Article below:
Exercise #1. Read the following article and then answer the following questions in paragraph
form.
1. How has DNA changed the study of biology over the past 50 years? Explain whether scientists
have shifted to a molecular level in the various subdisciplines of biology. Also, do you believe
any trend to the molecular level will continue far into the future?
2. Explain the role of DNA in the development of an organisms. Does DNA fully provide a
blueprint to create an individual? Can DNA by itself propagate itself or does it require other
molecular machines?
3. In modern biology, which is the role of physics in the study of organisms and their molecules?
Has physics moved to the forefront or does it play an ancillary role? As described in the article,
why are the molecular forces of very low energy in an organism?
Historians have the luxury of look- ing back at human endeavor over long periods of time, but
most scien- tists are too busy working in the present and thinking anxiously about the future and
have no time to view their work in the context of what has gone before. I once remarked that all
graduate students in biology divide history into two epochs: the past 2 years and every- thing else
before that, where Archimedes, Newton, Darwin, Mendel—even Watson and Crick—inhabit a
time-compressed universe as uneasy contemporaries. It seems remark- able that historians once
thought that science progressed by the steady addition of knowl- edge, building the edifice of
scientific truth, brick by brick. In his 1962 book The Struc- ture of Scientific Revolutions,
Thomas Kuhn argued that progress occurs in revolutionary steps by the introduction of new
paradigms, which may be new theories—new ways of looking at the world—or new technical
meth- ods that enhance observation and analysis.
Between Kuhn’s revolutions, scientif ic knowledge does advance by accretion, as there is much
to do to consolidate the new sci- ence. But then, inevitably, unsolved problems accumulate and,
in many cases, the inconsis- tencies have been put to one side and every- body hopes that they
will quietly go away. The edifice becomes rickety; some of its founda- tions are insecure and
many of the bricks have not been well-baked. This is when a new rev- olutionary wave in the
form of new ideas or new techniques appears, which allows us to condemn and demolish the
unsafe or corrupt parts of the edifice and rebuild truth. Often there is great resistance to the new
wave, but as Max Planck pointed out, it succeeds because the opponents grow old and die. The
process is then repeated: The radicals become liberals, the liberals become conservatives, the
conservatives become reactionaries, and the reactionaries disappear. Students of evolu- tion will
recognize this process in the theory of punctuated equilibrium: Organisms stay much the same
for very long periods of time; this is interrupted by bursts of change when novelty appears,
f.
One line of escape from the maze of blind alleys is of particular relevance to our theme: a phenomenon which goes under the name of 'paedomorphosis'. It was described by Garstang in the 1920s, and taken up by several biologists; but although the existence of the phenomenon is generally accepted, it made little impact on the orthodox theory and is rarely mentioned in the textbooks. It indicates that at certain critical stages evolution can retrace its steps, as it were, along the path which led to the dead end and make a fresh start in a new, more promising direction. The crucial event in this process is the appearance at the foetal, larval or juvenile stage of some useful evolutionary novelty which is carried over into the adult stage of the organism's progeny.
Now this lowering of the age of sexual maturity is a well-known evolutionary phenomenon called neoteny. It has two aspects: the animal starts to breed while still in a larval or juvenile stage; and it never reaches the fully adult stage, which is dropped off - eliminated from its life cycle ('terminal abbreviation').
Sir Gavin de Beer compared the process to the re-winding of a biological clock when evolution is in danger of running down and coming to a standstill: 'A race may become rejuvenated by pushing the adult stage of its individuals off from the end of their ontogenies, and such a race may then radiate out in all directions.'
Paedomorphosis - or juvenilization - thus appears to play an important part in the grand strategy of evolution. It involves a retreat from specialized adult forms to earlier, less committed and more plastic stages in the development of organisms - followed by a sudden advance in a new direction. It is as if the stream of life had momentarily reversed its course, flowing uphill for a while towards its original source; then opened up a new stream-bed - leaving the koala bear stranded on his tree like a discarded hypothesis. In other words, we are faced here with the same pattern of reculer pour mieux sauter, 'step back to leap', which we have encountered at the critical turning points in the evolution of science and art. Biological evolution is to a large extent a history of escapes from the blind alleys of over-specialization, the evolution of ideas a series of escapes from the tyranny of mental habits and stagnant routines. In biological evolution the escape is brought about by a retreat from the adult to a juvenile stage as the starting-point for the new line; in mental evolution by a temporary regression to more primitive and uninhibited modes of ideation, followed by the creative forward leap (the equivalent of a sudden burst of 'adaptive radiation'). Thus these two types of progress - the emergence of evolutionary novelties and the creation of cultural novelties reflect the same undoing-redoing pattern and appear as analogous processes on different levels.
―Janus: A Summing Up by Arthur Koestler
1. TEN MYTHS OF SCIENCE REEXAMINING WHAT WE THINK WE KNOW...W. .docxambersalomon88660
1. TEN MYTHS OF SCIENCE: REEXAMINING WHAT WE THINK WE KNOW...
W. McComas 1996
This article addresses and attempts to refute several of the most widespread and enduring misconceptions held by students regarding the enterprise of science. The ten myths discussed include the common notions that theories become laws, that hypotheses are best characterized as educated guesses, and that there is a commonly-applied scientific method. In addition, the article includes discussion of other incorrect ideas such as the view that evidence leads to sure knowledge, that science and its methods provide absolute proof, and that science is not a creative endeavor. Finally, the myths that scientists are objective, that experiments are the sole route to scientific knowledge and that scientific conclusions are continually reviewed conclude this presentation. The paper ends with a plea that instruction in and opportunities to experience the nature of science are vital in preservice and inservice teacher education programs to help unseat the myths of science.
Myths are typically defined as traditional views, fables, legends or stories. As such, myths can be entertaining and even educational since they help people make sense of the world. In fact, the explanatory role of myths most likely accounts for their development, spread and persistence. However, when fact and fiction blur, myths lose their entertainment value and serve only to block full understanding. Such is the case with the myths of science.
Scholar Joseph Campbell (1968) has proposed that the similarity among many folk myths worldwide is due to a subconscious link between all peoples, but no such link can explain the myths of science. Misconceptions about science are most likely due to the lack of philosophy of science content in teacher education programs, the failure of such programs to provide and require authentic science experiences for preservice teachers and the generally shallow treatment of the nature of science in the precollege textbooks to which teachers might turn for guidance.
As Steven Jay Gould points out in The Case of the Creeping Fox Terrier Clone (1988), science textbook writers are among the most egregious purveyors of myth and inaccuracy. The fox terrier mentioned in the title refers to the classic comparison used to express the size of the dawn horse, the tiny precursor to the modem horse. This comparison is unfortunate for two reasons. Not only was this horse ancestor much bigger than a fox terrier, but the fox terrier breed of dog is virtually unknown to American students. The major criticism leveled by Gould is that once this comparison took hold, no one bothered to check its validity or utility. Through time, one author after another simply repeated the inept comparison and continued a tradition that has made many science texts virtual clones of each other on this and countless other points.
In an attempt to provide a more realistic view of science and point out issues o.
El tequila es un destilado originario del municipio de Tequila en el estado de Jalisco, México. Se elabora a partir de la fermentación y destilado al igual que el mezcal, jugo extraído del agave, en particular el llamado agave azul (Agave tequilana), con denominación de origen en cinco estados de la República Mexicana (Guanajuato, Michoacán, Nayarit, Tamaulipas y por supuesto en todo el estado de Jalisco ya que en los tres primeros solo se puede producir en algunos municipios, los fronterizos a Jalisco). Es quizás la bebida más conocida y representativa de México en el mundo.
Essay about Sci-fI Films
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1
CHAPTER 1 Microbiology: Then and Now
CHAPTER 2 The Chemical Building Blocks of Life
CHAPTER 3 Concepts and Tools for Studying Microorganisms
CHAPTER 4 Cell Structure and Function in the Bacteria and Archaea
CHAPTER 5 Microbial Growth and Nutrition
CHAPTER 6 Metabolism of Microorganisms
CHAPTER 7 Control of Microorganisms: Physical and Chemical Methods
1 Foundations of Microbiology
P A R T
n 1676, a century before the Declaration of Independence, a Dutch
merchant named Antony van Leeuwenhoek sent a noteworthy let-
ter to the Royal Society of London. Writing in the vernacular of his
home in the United Netherlands, Leeuwenhoek described how he used a simple
microscope to observe vast populations of minute, living creatures. His reports
opened a chapter of science that would evolve into the study of microscopic
organisms and the discipline of microbiology. At that time, few people, including
Leeuwenhoek, attached any practical significance to the microorganisms, but
during the next three centuries, scientists would discover how profoundly these
organisms influence the quality of our lives and the environment around us.
We begin our study of the microorganisms by exploring the grassroot devel-
opments that led to the establishment of microbiology as a science. These devel-
opments are surveyed in Chapter 1, where we focus on some of the individuals
who stood at the forefront of discovery. Today we are in the midst of a third Golden Age of microbiology and our
understanding of microorganisms continues to grow even as you read this book. Chapter 1, therefore, is an important
introduction to microbiology then and now.
Part 1 also contains a chapter on basic chemistry, inasmuch as microbial growth, metabolism, and diversity
are grounded in the molecules and macromolecules these organisms contain and in the biological processes they
undergo. The third chapter in Part 1 sets down some basic concepts and describes one of the major tools for study-
ing microorganisms. Much as the alphabet applies to word development, in succeeding chapters we will formulate
words into sentences and sentences into ideas as we survey the different groups of microorganisms and concentrate
on their importance to public health and human welfare.
Although most microorganisms are harmless—or even beneficial, some cause infectious disease. We will concentrate
on the bacterial organisms in Chapter 4, where we survey their structural frameworks. In Chapter 5, we build on these
frameworks by examining microbial growth patterns and nutritional requirements. Chapter 6 describes the metabolism
of microbial cells, including those chemical reactions that produce energy and use energy. Part 1 concludes by consider-
ing the physical and chemical methods used to control microbial growth and metabolism (Chapter 7).
I
Cells of Vibrio cholerae, transmitted to
humans in contaminated water and food, are
the cause of cholera.
62582_CH01_001_034.pdf 162582.
-----GROVER MAXWELL------The Ontological Status of TheoretRayleneAndre399
-----GROVER MAXWELL------
The Ontological Status of Theoretical Entities
That anyone today should seriously contend that the entities referred
to by scientific theories are only convenient fictions, or that talk about
such entities is translatable without remainder into talk about sense con-
tents or everyday physical objects, or that such talk should be regarded
as belonging to a mere calculating device and, thus, without cognitive
con tent-such contentions strike me as so incongruous with the scientific
and rational attitude and practice that I feel this paper should turn out
to be a demolition of straw men. But the instrumentalist views of out-
standing physicists such as Bohr and Heisenberg are too well known to
be cited, and in a recent book of great competence, Professor Ernest
Nagel concludes that "the opposition between [the realist and the in-
slrumentalist] views [of theories] is a conflict over preferred modes of
sp cch" and "the question as to which of them is the 'correct position'
ha s only terminological interest." 1 The phoenix, it seems, will not be
laid to rest.
The literature on the subject is, of course, voluminous, and a compre-
lt nsive treatment of the problem is far beyond the scope of one essay.
I sl1all limit myself to a small number of constructive arguments (for a
r lically realistic interpretation of theories) and to a critical examination
of s me of the more crucial assumptions (sometimes tacit, sometimes
· pli it) that seem to have generated most of the problems in this area.2
' fo: . Nngcl, TJ1c Structure of Science (New York: Harcourt, Brace, and World,
l ') il), h . 6.
1 l•'or th e ge nes is and part of the content of some of the ideas expressed herein,
I 11n ind ·bled to a number of sources; some of the more influential are H. Feig!,
" 11: IN! ·11t inl llypotheses," PI1ilosophy of Science, 17 : 35-62 ( 1950); P . K. Feyerabend ,
'' 11 Alt · 111pt nt n Rcnlistic Interpretation of Experience," Proceedings of the Aristo-
1 / 1111 Soi ty, 58 :144- 170 (1958); N . R . Hanson, Patterns of Discovery (Cam-
111 ii 1: ,n111hridgc University Press, 1958); E. Nagel, Joe . cit.; Karl Popper, The
I 11 c• of S ·i 11tilic Dis ovcry (London : Hutchinson, 19 59); M. Scriven, "Definitions,
f1,ph11111 t i11 11 s 1 :ind Th ·ori ·s," in Miuneso ta Studies in tlie Philosophy of Science,
3
Grover MaxweII
The Problem
Although this essay is not comprehensive, it aspires to be fairly self-
contained. Let me, therefore, give a pseudohistorical introduction to the
problem with a piece of science fiction (or fictional science).
In the days before the advent of microscopes, there lived a Pas teur-
like scien tist whom, following the usual custom, I shall call Jon es. Re-
fl ecting on the fact that certain diseases seemed to be transmitted from
one person to another by means of bodily contact or b y contact with
articles handled previously by an afHicted person, Jones began to specu-
late about ...
-----GROVER MAXWELL------The Ontological Status of TheoretSilvaGraf83
-----GROVER MAXWELL------
The Ontological Status of Theoretical Entities
That anyone today should seriously contend that the entities referred
to by scientific theories are only convenient fictions, or that talk about
such entities is translatable without remainder into talk about sense con-
tents or everyday physical objects, or that such talk should be regarded
as belonging to a mere calculating device and, thus, without cognitive
con tent-such contentions strike me as so incongruous with the scientific
and rational attitude and practice that I feel this paper should turn out
to be a demolition of straw men. But the instrumentalist views of out-
standing physicists such as Bohr and Heisenberg are too well known to
be cited, and in a recent book of great competence, Professor Ernest
Nagel concludes that "the opposition between [the realist and the in-
slrumentalist] views [of theories] is a conflict over preferred modes of
sp cch" and "the question as to which of them is the 'correct position'
ha s only terminological interest." 1 The phoenix, it seems, will not be
laid to rest.
The literature on the subject is, of course, voluminous, and a compre-
lt nsive treatment of the problem is far beyond the scope of one essay.
I sl1all limit myself to a small number of constructive arguments (for a
r lically realistic interpretation of theories) and to a critical examination
of s me of the more crucial assumptions (sometimes tacit, sometimes
· pli it) that seem to have generated most of the problems in this area.2
' fo: . Nngcl, TJ1c Structure of Science (New York: Harcourt, Brace, and World,
l ') il), h . 6.
1 l•'or th e ge nes is and part of the content of some of the ideas expressed herein,
I 11n ind ·bled to a number of sources; some of the more influential are H. Feig!,
" 11: IN! ·11t inl llypotheses," PI1ilosophy of Science, 17 : 35-62 ( 1950); P . K. Feyerabend ,
'' 11 Alt · 111pt nt n Rcnlistic Interpretation of Experience," Proceedings of the Aristo-
1 / 1111 Soi ty, 58 :144- 170 (1958); N . R . Hanson, Patterns of Discovery (Cam-
111 ii 1: ,n111hridgc University Press, 1958); E. Nagel, Joe . cit.; Karl Popper, The
I 11 c• of S ·i 11tilic Dis ovcry (London : Hutchinson, 19 59); M. Scriven, "Definitions,
f1,ph11111 t i11 11 s 1 :ind Th ·ori ·s," in Miuneso ta Studies in tlie Philosophy of Science,
3
Grover MaxweII
The Problem
Although this essay is not comprehensive, it aspires to be fairly self-
contained. Let me, therefore, give a pseudohistorical introduction to the
problem with a piece of science fiction (or fictional science).
In the days before the advent of microscopes, there lived a Pas teur-
like scien tist whom, following the usual custom, I shall call Jon es. Re-
fl ecting on the fact that certain diseases seemed to be transmitted from
one person to another by means of bodily contact or b y contact with
articles handled previously by an afHicted person, Jones began to specu-
late about ...
Literature review sheet covering recent developments in the understanding of the psychoneuroimmunologic aspects of schizophrenia pathogenesis, diagnostic approach, and antibody-specific iatrologic tailoring. I created this sheet as a handout for a brief talk given to a group of psychiatrists, psychiatry residents, and medical students at East Central Regional Hospital in Augusta, GA, USA on Wednesday, September 18, 2019.
Slides from a Microsoft PowerPoint® presentation I delivered covering the basic clinical presentation, diagnosis, pathogenesis/pathophysiology, treatment, and prognosis of small cell cancer of the lung. This presentation was given on February 8, 2019 at the Medical College of Georgia, Augusta Campus to an audience of second-year MD candidates and a clinical pathologist.
Paroxysmal Nocturnal Hemoglobinuria (PNH) - A Pathologic SurveyJackson Reynolds
Slides from a Microsoft PowerPoint® presentation I delivered covering the basic clinical presentation, diagnosis, pathogenesis/pathophysiology, treatment, and prognosis of paroxysmal nocturnal hemoglobinuria (PNH). This presentation was given on October 3, 2018 at the Medical College of Georgia, Augusta Campus to an audience of clinical pathologists and second-year MD candidates.
Kaposi Sarcoma in Immune Reconstitution Inflammatory SyndromeJackson Reynolds
Slides from a Microsoft PowerPoint presentation delivered by Jackson David Reynolds on March 30, 2017 for the Immunology (BIOL 4100) course of Dr. Chuck Fink, PhD at Dalton State College in Dalton, GA, USA.
A Critical Analysis of Mark Buchan’s “"Too Difficult for a Single Man to Understand:" Medea's Out-Jutting Foot” written for Kent Harrelson, PhD's World Literature I course at Dalton State College during the Fall 2013 semester.
Kaposin B Interacts with c-myc to Engender Angiogenesis in Kaposi Sarcoma Neo...Jackson Reynolds
Slides from a PowerPoint presentation given by Jackson David Reynolds on Monday, March 28, 2016 at the University of North Georgia, Dahlonega campus for Senior Seminar in Biology (professor: Dr. Ryan Shanks, PhD).
Phylum Nematoda (and Four Phyla of Likely Nematode Relatives)Jackson Reynolds
Slides from Apple Keynote presentation given by Jackson David Reynolds on Thursday, November 12, 2015 at the University of North Georgia, Dahlonega campus for Dr. Michael Bodri, MS, VMD, PhD’s Invertebrate Zoology course.
Slides from an Apple Keynote presentation given by Jackson David Reynolds on December 1, 2015 at the University of North Georgia, Gainesville campus for Dr. Jeanelle Morgan, PhD’s Genetics course.
Richard's aventures in two entangled wonderlandsRichard Gill
Since the loophole-free Bell experiments of 2020 and the Nobel prizes in physics of 2022, critics of Bell's work have retreated to the fortress of super-determinism. Now, super-determinism is a derogatory word - it just means "determinism". Palmer, Hance and Hossenfelder argue that quantum mechanics and determinism are not incompatible, using a sophisticated mathematical construction based on a subtle thinning of allowed states and measurements in quantum mechanics, such that what is left appears to make Bell's argument fail, without altering the empirical predictions of quantum mechanics. I think however that it is a smoke screen, and the slogan "lost in math" comes to my mind. I will discuss some other recent disproofs of Bell's theorem using the language of causality based on causal graphs. Causal thinking is also central to law and justice. I will mention surprising connections to my work on serial killer nurse cases, in particular the Dutch case of Lucia de Berk and the current UK case of Lucy Letby.
Multi-source connectivity as the driver of solar wind variability in the heli...Sérgio Sacani
The ambient solar wind that flls the heliosphere originates from multiple
sources in the solar corona and is highly structured. It is often described
as high-speed, relatively homogeneous, plasma streams from coronal
holes and slow-speed, highly variable, streams whose source regions are
under debate. A key goal of ESA/NASA’s Solar Orbiter mission is to identify
solar wind sources and understand what drives the complexity seen in the
heliosphere. By combining magnetic feld modelling and spectroscopic
techniques with high-resolution observations and measurements, we show
that the solar wind variability detected in situ by Solar Orbiter in March
2022 is driven by spatio-temporal changes in the magnetic connectivity to
multiple sources in the solar atmosphere. The magnetic feld footpoints
connected to the spacecraft moved from the boundaries of a coronal hole
to one active region (12961) and then across to another region (12957). This
is refected in the in situ measurements, which show the transition from fast
to highly Alfvénic then to slow solar wind that is disrupted by the arrival of
a coronal mass ejection. Our results describe solar wind variability at 0.5 au
but are applicable to near-Earth observatories.
Professional air quality monitoring systems provide immediate, on-site data for analysis, compliance, and decision-making.
Monitor common gases, weather parameters, particulates.
What is greenhouse gasses and how many gasses are there to affect the Earth.moosaasad1975
What are greenhouse gasses how they affect the earth and its environment what is the future of the environment and earth how the weather and the climate effects.
Richard's entangled aventures in wonderlandRichard Gill
Since the loophole-free Bell experiments of 2020 and the Nobel prizes in physics of 2022, critics of Bell's work have retreated to the fortress of super-determinism. Now, super-determinism is a derogatory word - it just means "determinism". Palmer, Hance and Hossenfelder argue that quantum mechanics and determinism are not incompatible, using a sophisticated mathematical construction based on a subtle thinning of allowed states and measurements in quantum mechanics, such that what is left appears to make Bell's argument fail, without altering the empirical predictions of quantum mechanics. I think however that it is a smoke screen, and the slogan "lost in math" comes to my mind. I will discuss some other recent disproofs of Bell's theorem using the language of causality based on causal graphs. Causal thinking is also central to law and justice. I will mention surprising connections to my work on serial killer nurse cases, in particular the Dutch case of Lucia de Berk and the current UK case of Lucy Letby.
Observation of Io’s Resurfacing via Plume Deposition Using Ground-based Adapt...Sérgio Sacani
Since volcanic activity was first discovered on Io from Voyager images in 1979, changes
on Io’s surface have been monitored from both spacecraft and ground-based telescopes.
Here, we present the highest spatial resolution images of Io ever obtained from a groundbased telescope. These images, acquired by the SHARK-VIS instrument on the Large
Binocular Telescope, show evidence of a major resurfacing event on Io’s trailing hemisphere. When compared to the most recent spacecraft images, the SHARK-VIS images
show that a plume deposit from a powerful eruption at Pillan Patera has covered part
of the long-lived Pele plume deposit. Although this type of resurfacing event may be common on Io, few have been detected due to the rarity of spacecraft visits and the previously low spatial resolution available from Earth-based telescopes. The SHARK-VIS instrument ushers in a new era of high resolution imaging of Io’s surface using adaptive
optics at visible wavelengths.
A brief information about the SCOP protein database used in bioinformatics.
The Structural Classification of Proteins (SCOP) database is a comprehensive and authoritative resource for the structural and evolutionary relationships of proteins. It provides a detailed and curated classification of protein structures, grouping them into families, superfamilies, and folds based on their structural and sequence similarities.
Nutraceutical market, scope and growth: Herbal drug technologyLokesh Patil
As consumer awareness of health and wellness rises, the nutraceutical market—which includes goods like functional meals, drinks, and dietary supplements that provide health advantages beyond basic nutrition—is growing significantly. As healthcare expenses rise, the population ages, and people want natural and preventative health solutions more and more, this industry is increasing quickly. Further driving market expansion are product formulation innovations and the use of cutting-edge technology for customized nutrition. With its worldwide reach, the nutraceutical industry is expected to keep growing and provide significant chances for research and investment in a number of categories, including vitamins, minerals, probiotics, and herbal supplements.
A Brief History of Mitochondria: The Elegant Origins of a Magnificent Organelle
1. University of North Georgia A Brief History of Mitochondria
Jackson David Reynolds Page 1 of 11
A Brief History of Mitochondria
The Elegant Origins of a Magnificent Organelle
A Case Study by Jackson David Reynolds
University of North Georgia, Gainesville, GA, USA
Spring 2016
JACKSON DAVID REYNOLDS
Image modified from: Interesting Facts, 2014.
2. University of North Georgia A Brief History of Mitochondria
Jackson David Reynolds Page 2 of 11
Part I – Insights and Hypotheses
In the first decade of the 20th century, the Russian botanist Konstantin Mereschcowsky,1,2
while studying plastids3 in lichen, hypothesized that complex, eukaryotic cells were evolutionarily
derived from early cells which had symbiotically incorporated other, less complex cells into their cytosol
– a phenomenon now known as endosymbiosis. In 1905, and again in 1910, he published work in
defense of this idea (Bock & Knoop, eds., 2012).
In the following decade, an American anatomist, Ivan Wallin, working at the University of
Colorado Medical School, noticed that mitochondria could be stained with staining techniques
identical to those used for some bacterial cells. This led him to conclude that mitochondria were once
independent bacteria which had been taken up by and subsequently co-evolved with “proto-
eukaryotic” cells into their modern incarnation (Wallin, 1922). His scientific contemporaries, however,
rejected his ideas, as he had carried out his staining experiments on cultured mitochondria (isolated
from fetal rabbit hepatocytes) in a shed behind the university’s anatomy lab, and thus contamination
with environmental bacteria yielding false positive staining results was strongly suspected (Cold Spring
Harbor Laboratory, 2011). Whether or not Wallin’s experiments were contaminated, his ideas – as well
as those of Mereschcowsky – were ultimately vindicated by the discovery of overwhelming evidence
amassed in the latter half of the 20th century for the endosymbiotic origin of the modern mitochondrion,
chiefly through the work of American cell biologist and evolutionary theorist Lynn Margulis – a name
now synonymous with the focus of this case study, endosymbiotic theory.
Dr. Margulis, in a now famous 1967 paper4, put forth a detailed theoretical framework of the
evidence she believed provided strong support for the endosymbiotic origin of the Eukarya – an idea
still so radical at the time that her paper was rejected by no less than fifteen academic publications before
finally being accepted by the Journal of Theoretical Biology (Sagan, 1967; Margulis, 1995). Her paper, On
the Origin of Mitosing Cells, brought to bear several main observations and hypotheses – which have
since been rigorously tested and substantiated – which now leave virtually no doubt that mitochondria
did in fact originate from free-living, primitive prokaryotes which were incorporated into – and
1 “Mereschcowsky” also sometimes transliterated into English as “Mereschkowski.”
2 Russian: Константи́н Серге́евич Мережко́вский.
3 “[P]lastid: [A]ny of several types of plant cytoplasmic organelles derived from protoplastids, including chloroplasts, amyloplasts, chromoplasts,
proteinoplasts, and elaioplasts” (Hardin, Bertoni, Kleinsmith, & Becker, 2012, G-18).
4 Dr. Margulis published On the Origin of Mitosing Cells as “Lynn Sagan,” her married name at the time of the paper’s publication.
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subsequently co-evolved along with – primitive “proto-eukaryotes” remarkably rapidly after abiogenesis
on Earth.
While, in the clear light of retrospection, it may be tempting to scoff at the initial resistance to
early endosymbiotic hypotheses, it is important to always keep in mind the nature of the scientific
process. The engine of scientific progress is fueled by an unwavering commitment to skepticism and
critical thinking on the part of scientists, and no idea – regardless of how “obvious” or well-reasoned it
may seem to be – should ever be accepted without first being subjected to a rigorous gauntlet of
meticulous testing. Scientific knowledge – which is always tentative – therefore exists at different degrees
of certainty, each of which has an associated term to indicate the level and context of its surety based
on the best available evidence. The terms “hypothesis,” “theory,” and “law,” thus, denote these
contextual distinctions of confidence.
In the common parlance, the words “hypothesis” and “theory” are casually employed as virtual
synonyms, doing a damaging disservice to the large distinction between the actual definitions of these
words in a scientific context. Similarly, people often confuse laws with theories, such as in the frequent
misstatement of gravitational theory by non-scientists as “the law of gravity.5”
To expound upon this problem, as well as to provide clarification as to the actual scientific
meanings of these words, watch the short video Theory vs. Hypothesis vs. Law… Explained! from the PBS®6
series It's Okay To Be Smart at https://youtu.be/lqk3TKuGNBA (Nicolosi, dir., 2015).
ASSESSMENT ITEMS
A working familiarity with the technical connotations of these three terms is of the utmost
importance in one’s understanding of any scientific writing. To further cement your grasp of the
similarities and differences between hypotheses, theories, and laws, construct a tripartite Venn diagram
of the three terms in which you provide levels of evidence which apply to each.
After constructing the diagram, briefly write a short paragraph as to why you believe that theories
are far more common in the biological sciences than are laws.
5 There are individual gravitational laws, to be sure (e.g., Newton’s famous Universal Law of Gravitation: {Fg ∝ (m1m2/r2)}), but the sum of these laws and
their associated experimentally verified observations together comprise gravitational theory.
6 Public Broadcasting Service.
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Part II – Discoveries and Evidence
Endosymbiotic theory now provides the most plausible and well-supported explanation for
mitochondrial origins, but how did this once heretical idea become widely embraced by the scientific
community? While On the Origin of Mitosing Cells was a largely speculative work, Dr. Margulis followed
up her ideas with a more experimentally substantiated paper nine years later in the journal Experimental
Parasitology entitled Genetic and evolutionary consequences of symbiosis (Margulis, 1976). This publication, which
was less speculative in nature, served to dismantle the doubts held by many in the scientific community
at the time with regard to the validity of endosymbiotic theory as a legitimate avenue of study.
Several observations similar to those made by Mereschcowsky and Wallin led Lynn Margulis to
strongly suspect prokaryotic origins for mitochondria and other modern organelles, such as plastids.
When, as an undergraduate, she learned that one of her professors had observed DNA in chloroplasts
(a type of plastid), this only served to further pique her curiosity and embolden her to more deeply
investigate eukaryotic evolution (Zimmer & University of California Museum of Paleontology, n.d.).
Margulis observed that mitochondria contained their own DNA which was contained in a circular
chromosome like that of bacteria, that some mitochondria were evidently similar in size to certain
modern prokaryotes, and that, like bacteria, mitochondria have two separate plasma membranes
(Sagan, 1967).
Throughout the following decades, it was further uncovered that mitochondria possess their own
ribosomes – ribosomes which, interestingly, are comprised of subunits equivalent in size to those of
extant prokaryotes – and that they replicate independently (by binary fission, no less!) in a manner
chronologically independent from the mitotic activity of their host cell. Perhaps even more intriguingly,
like bacterial DNA, mitochondrial DNA (mtDNA) is devoid of introns (Cummings, Spencer, &
Paladino, 2012, pp. 225-228; Gillen, 2009, A-37-A-39)! Most astounding to some, however, was the
discovery that while nuclear DNA does encode some mitochondrial proteins, the specific sequences
responsible for these gene products have been shown to be of ancestral bacterial origin (Gillen, 2009,
A-37-A-39)!
To acquire a deeper grasp of the multiple lines of evidence which seamlessly converge in strong
support of the endosymbiotic theory’s explanatory model for mitochondrial origin, read the abstract
and the sections entitled “1. Introduction” and “4. The origin of mitochondria (and chloroplasts)” from
the review article Endosymbiotic theories for eukaryote origin by Martin, et al., paying careful attention to the
authors’ focus on the natural history of mitochondria and the experiments which shed light on this
organelle’s remarkable beginnings.
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ASSESSMENT ITEM
Imagine that you are a graduate student tasked with assisting in writing the cell biology textbook
on which your doctoral advisor is currently working. This hypothetical text, The Eukaryotic Cell: A
Molecular Perspective by Reynolds, et al., is aimed at undergraduate students and will contain a chapter
entitled “Endosymbionts: A Natural History of Mitochondria and Plastids” for which you and your
fellow doctoral candidates must write a subsection from the chapter section “Evidences for
Endosymbiotic Mitochondrial Origins”. Choosing one from the following list of hypothetical
subsections, write a mock text of no more than 450 words for this subsection, using what you have
learned thus far to inform your writing. Focus on conciseness, readability, and clarity of thought.
• “Morphological parallels between mitochondria and modern prokaryotes”
• “Mereschcowsky and Wallin: early perspectives”
• “Margulis and Goksøyr: an idea develops”
• “Primitive phagocytes engulfed H2-producing α-proteobacteria”
• “‘Proto-eukaryotic’ metabolism as a selective advantage”
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Part III – Implausibility of the Autogenous Model
While we now know that the wealth of evidence for the endosymbiotic origins of mitochondria
makes this theory virtually undeniable, such has obviously not always been the case. Recall that
Margulis’ publication of On the Origin of Mitosing Cells – which, we should again take note, was largely
hypothetical – was met with marked intransigence – and this in 1967 (Lake, 2011)! At the time, the
prevailing hypothesis was that all of the Eukarya arose from a single, ancestral prokaryote and that all
membrane-bound organelles arose from the infolding of existing cytosolic elements and plasmid-
mediated compartmentalization events which ultimately led to the intricately connected organellular
systems we today observe in all modern eukaryotes. This idea is referred to as the autogenous
hypothesis (The George Washington University, n.d.; Keeling, 2014). Initially, observational evidence
did seem to suggest that mitochondria may have evolved autogenously. For instance, not all
mitochondrial DNA is in fact circular; the mitochondrial chromosome of members of the protozoan
genus Paramecium is linear (Pritchard & Cummings, 1981). Furthermore, most mitochondria exhibit a
reticular morphology far removed from that of the prokaryote-like, bacillus-shaped drawings of
mitochondria commonly found in textbooks (Davison & Garland, 1977, p. 233s; Hardin, et al., 2012,
pp. 254-257). This school of thought, of course, has fallen greatly out of favor in view of the many
evidentiary indications of the validity of the endosymbiotic model, as detailed in Part II of this case
study. To quote evolutionary biochemist Nick Lane’s superb paper Energetics and genetics across the
prokaryote-eukaryote divide on the issue, “There is little doubt that all known eukaryotic cells share a
common ancestor that arose only once in four billion years of evolution. Common traits range from the
conserved position of many introns, to the structure of nuclear pore complexes, to complex traits such
as syngamy7 and two-step meiosis. It is implausible that all of these shared properties arose [largely] by
lateral gene transfer (which is inherently asymmetric in mechanism) or convergent evolution (which
implies that traits like intron position are dictated by selective constraints, rather than historical
contingency). Common ancestry is [...] the most parsimonious explanation”8 (2011). Common ancestry
(and therefore endosymbiosis) is the most parsimonious explanation for the evolution of the modern
mitochondrion, indeed.
Interestingly however, over the past several years, evidence is beginning to be brought to light
that some eukaryotic cellular elements, namely the Golgi complex and endoplasmic reticulum (among
other members of the endomembrane trafficking system), may have indeed originated in an autogenous
7 “Syngamy[:] The fusion of two cells, or of their nuclei, in reproduction” (Oxford University Press, 2016).
8 (Underlining added.)
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manner! Read (in its entirety) the 2008 paper Phylogeny of endocytic components yields insights into the process of
nonendosymbiotic organelle evolution by Dacks, et al. for a solid overview of some of this recent work.
ASSESSMENT ITEM
Now that you have had the opportunity to survey the emerging evidence for the likely
autogenous evolutionary origin of some organelles such as the Golgi complex, compare the strength of
the evidences detailed in the paper by Dacks, et al. for this likely scenario to those historically proposed
in defense of an autogenous mitochondrial genesis by writing a brief, informal paper of no more than
700 words, laying out what specific evidence you think would need to be uncovered in order for the
autogenous hypothesis to regain support as a valid explanation for the natural history of mitochondria.
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Conclusion
Thanks to the tireless work of Mereschcowsky, Wallin, and their many scientific successors such
as Lynn Margulis and the previously quoted Dr. Lane (amongst many others), we now know that
mitochondria almost certainly evolved from the symbiotic metabolic relationship of an early prokaryote
and a larger, “proto-eukaryote” which had engulfed it.
To now bring the fascinating issue of mitochondrial evolution into a broader context, re-read
the review article Endosymbiotic theories for eukaryote origin, this time in its entirety, focusing principally on
thinking about what connections you can make between the authors’ discussions of mitochondrial
evolution and those pertaining to the evolution of plastids (especially the chloroplast).
ASSESSMENT ITEM
In order to better interpret the review article you just read in the broader context of scientific
review literature in general, construct a bulleted outline of a hypothetical review article on the biological
topic of your choice. This outline should be generally representative of extant review literature in both
format and contents. You may wish to view other published review papers in order to gain a better feel
of their usual layout. An excellent resource for this is the National Center for Biotechnology
Information’s 9 (NCBI) PubMed 10 literature database which can be accessed by anyone at:
http://www.ncbi.nlm.nih.gov/pubmed. (To access only review articles, enter your search term(s) into
the search bar, click ‘Search,’ then click “Review” under “Article Types” in the left-hand pane, then
click “Free full text” under “Text Availability” in the same options pane.)
9 Part of the United States National Library of Medicine (NLM) (a branch of the National Institutes of Health {NIH}) (https://www.nlm.nih.gov).
10 Part of the United States NLM and NIH (http://www.nih.gov).
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References
Cold Spring Harbor Laboratory. (2011). Higher cells incorporate an ancient chromosome.
Retrieved March 14, 2016, from http://www.dnaftb.org/30/bio.html
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(Eds.), Concepts of Genetics (10th ed., pp. 225-228). San Francisco, CA: Pearson Education,
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Dacks, J. B., Poon, P. P., & Field, M. C. (2008). Phylogeny of endocytic components yields
insight into the process of nonendosymbiotic organelle evolution. Proceedings of the
National Academy of Sciences, 105(2), 588-593. doi:10.1073/pnas.0707318105
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