The following essay was adapted from an article by Crystal Jeter
One set of alleles is responsible–for determining each trait, and there are only 2 different alleles (dominant and recessive) for each gene. By way of explanation, alleles are different forms of a gene (and usually expressed by, say A & a). After learning about simple Mendelian inheritance, alleles (dominant and recessive) and sex-llnked traits, students often think that it is possible to predict results easily.. In humans at least three different genes are associated with eye color. Coat color in cats is controlled by at least six genes Furthermore, the number of particular alleles inherited masks the expression of some characteristics. For example, the number of alleles that you inherit from each parent that code for production of melanin may partially determine your hair color. Inheritance of more of the alleles may lead to darker hair while inheritance of fewer may lead to lighter hair. For traits that show a Mendelian pattern of inheritance, students often assume that there are only 2 possible alleles for a trait. This is true in some cases. But in many cases, there are more alleles for a trait. Human height, weight, skin color, and intelligence are all polygenic traits (having many genes ).
2. Your genes determine all of your characteristics, and cloned organisms are exact copies of the original. While genes play a huge role in how an organism develops, environmental factors also play a role. Epigenetics is the study of heritable changes that occur without changes in the genome. The gene expression in identical twins has shown changes from factors such as diet and exposure to a different environment. Further studies with identical twins have suggested that these changes can accumulate over the life of the organism. The cloning of Rainbow, a domestic cat demonstrated one striking example of epigenetics. Rainbow’s coat revealed calico coloration while the coat of the clone named Copycat, is a tabby pattern. Because Copycat and Rainbow had identical genomes, the differences must be due to epigenetic factors.
3. All mutations are harmful. A mutation is a change in the genetic code of an organism. Many mutations are harmful and cause organisms not to develop properly. However, many mutations are silent and some prove beneficial. In the case of a silent mutant, change in the genome does not change the production of the amino add sequence and subsequent protein (remember that multiple codons may code for the same amino acid, so a change in one nucleotide does not necessarily change the gene product). If an organism does live with a mutation, then often the environment will determine whether the mutation is beneficial or harmful. Production of one protein vs. another may confer a characteristic such as a difference in coloration or in the ability to digest a resource (e.g. the ability to digest lactose or maltose instead of sucrose). The phenotypic outcome may be selected, for or against depending on environmental factors
4. A dominant trait is the most likely to be found in the population. The term dominant allele.sometimes conveys to students the impression that the dominant form of a trail is the one that exists in the greatest proportion in a population. However, dominant refers only to the allele’s expression over another allele. Human genetics includes examples of dominant traits that do not affect the majority of apopulation. In fact, acnoridroplasia, a type of dwarfism caused by the presence of a dominant allele is found in fewer than 1 in 10,000 live births. Huntington’s disease, a degenerative disease caused by the presence of a dominant allele occurs at a rate of about 3 to 7 cases per 100,000 people of European descent. And polydactyly (having extra fingers and dwarfism) is a dominant trait. But how many of us have six digits ?
5. While the fifth point is not necessarily a misconception Genetics terms are often confused. Many students understand the basic ideas of genetics but need more familiarity with the terms. For example, students often struggle with the difference between a chromosome, a gene and an allele. Chromosomes are structures containing proteins and a single coiled strand of DNA;chromosomes are visible with a microscope only during part of the cell cycle. Genes are units of heredity—specific sequences of DNA or RNA that create proteins with particular functions in an organism. Alleles are variants of a gene. Making sure that students have a strong foundation in the terminology can greatly improve their understanding of genetics and prevent misconceptions.
Dispelling these 5 misconceptions will help students better understand genetics and activities that you plan for both the classroom and the lab. They will also realize there are many influences on the way living things develop genetically over time.
The concepts of surface area and volume are important concepts in both the physical (nonliving) world and the biological (living) world. Now, combine those attributes into a single relationship, the surface area to volume ratio and you have a whole new phenomenon that has enormous ramifications. Let’s look at the relationship in the physical world first.
Let’s say you have a chunk of coal about the size of a large rock that you, want to burn and all you have to light it is a single match. What chance do you think you have to light it? Now you break that chunk of coal into a few smaller chunks. Can you light one? Perhaps with the aid of some fuel such as charcoal lighter fluid and paper “starters” you may succeed. Now pulverize those chunks into fine powder and light the match… You better have a “long reach” or you may take a trip to the ER at a local hospital. Why the difference? Let’s look at the mathematics of what you happens to the SA:V ratio when you break it up into smaller pieces. But first let’s consider what you need to burn– anything. From science we know that three conditions must be met. We need:
• a combustible material (i.e. coal)
• a supply of oxygen.
• enough heat to ignite the substance (bring it to its kindling temperature)
For now let’s focus on the oxygen supple.
The formula for calculating the surface area of a cube, as an example, is length x width × number of sides (6) or SA = 6s2 and let’s compute that for a 1 cm cube:
SA = 1x1x 6 (6 x 12) = 6cm3 and for a 2 cm cube:
SA = 2 x2x6 (6 x 22) = 24 cm3 and for a 3cm3 cube
SA = 3×3×6 (6×32) = 54 cm3
Now let’s figure the volume for each of these. The formula is length x width x height (l3)
V for a 1 cm3 = 1x1x1 (13) = 1cm3
V for a 2cm3 = 2x2x2 (23) = 8 cm3
V for a 3 cm3 = 3x3x3 (33) = 27 cm3
Comparing: SA:V
1cm3 = 6:1
2cm3 = 24: 8 = 3: I
3cm3 = 54: 27 = 2: 1
Now 6:1 vs. 2:1 =3:1 = 3
which means that a l cm3 has three times as much surface are as a 3cm3 which means it has three times as much contact with oxygen in the air which also means that a fine powder’s contact with oxygen compared to a large rock size chunk of coal is enormous, more like humongous when you consider it has 10umteenth pieces.
This principle, of course, applies to all combustible materials and even extends to other scenarios besides burning. It applies to baby powder as well as gunpowder, and to highway salt as well as fine fertilizer pellets.
Now let’s consider the concept of increased surface area in living systems. In our lungs we have tiny microscopic air sacs called alveoli, millions of them that increase the surface area of our lungs for the exchange of both oxygen and carbon dioxide, oxygen into and carbon dioxide out of the lungs. Remember from past essays that CO2 is a product of cellular respiration and is toxic to living cells. The alveoli are richly supplied with capillaries where CO2 from body cells is exchanged for O2 from outside thebody. See the diagram below. Red indicates O2 rich blood and blue represents high CO2 blood. The whole process is called diffusion.
Obviously, the millions of alveoli inside our lungs increase the surface area and enable an animal our size or larger to carry on life’s activities without an enormous set of lungs. Next, let’s consider a unique group of animals that are adapted for breathing in the water and on land, amphibians. Many of my students were surprised to find such small lungs during dissection—until they learned that frogs breathe subcutaneously, through their blood vessel rich skin. Think of the size of the surface area, basically all of the body exposed to water.
Your small intestine contains mullions of microscopic finger-like projections called villi which allows digested food to be absorbed by their rich supply of blood in, you guessed it, the capillaries This includes active transport, which requires energy (from ATP breakdown) and passive transport which does not require energy (diffusion and facilitated diffusion).
Our brains are convoluted (wrinkled) on the surface to increase the surface area. There are other examples of the extremely important concept of increased area of concentration. Let’s consider cell reproduction next.
DCF 1.0
Why do cells reproduce? Obviously one reason is to replace worn out or dead cells. However, a lesser known reason is to increase cell efficiency. As cells grow their surface area to volume ratios goes down. Once again, compare the SA: ratio of the 3 cm3 to the l cube. Remember all substances enter and leave the cell through the cell membrane (surface area). So as cells grow they become less efficient at bringing in nutrients and getting rid of toxic substances. Cell reproduction (mitosis and cytokinesis) replaces large cells by smaller more efficient cells.
I hope you have a greater understanding of, and appreciation for, the concept of increased surface area in our daily lives.
References
Mader, S. Biology, eighth edition (2004) McGraw-Hill, New York, NY
As you have probably found out from the early essays, I usually introduced a new topic in my biology classes with a question like “what is science?” In this case I asked the question “In its simplest form, what does evolution mean?” Upon hearing no answers I would suggest a three word answer “change through Time”. Then we would progress to a discussion of evolution of, say, music, hair styles, or cars, soliciting different kinds of cars that have appeared over time. If talking about music invariably Rock ‘n roll would enter the discussion and I would ask “what was considered to be the first Rock ‘n roll song”? So I ask the reader now that question. Bonus: Name the performer. (Hint # one; it was a group: hint # 2, it was the theme song of a popular ’80’s (I think) sit com. Still don’t know— . As usual, find the answer at the end.
When most people hear the word evolution, they immediately think of man from ape and “close their ears”. Again I say that’s not true. However, I don’t plan to get into human evolution anyway. Many people say “that’s just a theory”. Well, yes and no-and that depends on what you mean by a theory. I would recommend you review the scientific definition of a theory in essay II. Evolution, at least in some forms and some levels is a fact. Let me show you what I mean. Do you believe that last year’s flu shot won’t work for this year’s flu strain? Do you believe that viruses and bacteria change in form and function? Do you believe that antibiotics that worked well years ago aren’t so effective now? If you answered yes to one or more of these questions, then you acknowledge that evolution occurs. And in each case an organism changed through time (evolved) and is responsible for, say, a new flu shot or new antibiotics all the time. Penicillin was serendipitously discovered in the late 1920’s by Sir Alexander Fleming, but because he had no method of mass producing it, the world had to wait until the early 1940’s during World War II to use it. Fortunately, mass production saved countless numbers of lives in the war. The years following the war witnessed a period of rapid development of antibiotics. I remember as an early primary grade student taking three kinds of antibiotics to fight yearly bouts of pneumonia, bronchitis, or bronchial pneumonia. Penicillin and its derivatives were hailed as “miracle drugs”. But by the late 1950’s those drugs were rendered relatively useless against bacterial infections. Any ideas why? If you said that they evolved and became resistant to the drugs, you are right. And how did they do that? Well, the usual explanation which, by the way, still holds up today, is that some of the bacteria were just naturally resistant to the drug’s effects. By “naturally” I mean that they were genetically immune, that is, they were genetically endowed. Bacteria, like all living organisms have individual differences (different gene pools). To finish the story, these genetically endowed bacteria proliferated in great numbers while their genetically inferior cousins rapidly died from the drugs. Voila, I just took you through the extremely important concepts of survival of the fittest and natural selection, two cornerstones of genetics and evolution.
Let’s back up a little and quote a paragraph from essay II. “Allow me to comment briefly on direct vs. indirect evidence or observations. Most of what we learn about present conditions results from direct observations. Virtually everything we know about past conditions is derived from indirect evidence. The fossil record and (Earth’s crust) core samples are two examples of indirect evidence.”
James Hutton (1726-1797) proposed that the earth had been sculptured by slow, gradual processes, the constructive and destructive processes described in essay III. This idea became known as uniformitarianism which also suggested that the oldest rock layers were at the bottom and subsequent layer formed on top. This set the stage for the idea of determining the “relative” age of rocks.
William Smith, (1769 – 1839) an English surveyor, was one of the first to scientifically study the distribution of fossils. He studied the geological strata (order of rock layers) and noted that each strata contained characteristic kinds of fossils.
Charles Lyell (1797 – 1875) who influenced Darwin the most, furthered the concept that Hutton had established. Since these forces were extrem-m-m-mely (my word for emphasis) slow, the earth must be very old, much older than previously thought.
Charles Darwin was certainly not the first person to suggest that things change over time, which included “living things” The Frenchman Jean Baptiste Lamarck (1744 – 1829) believed in what he called “acquired characteristics”; his classic example was that giraffe’s necks became long because of many generations of stretching higher and higher to reach leaves in trees. Actually some form of evolutionary thought goes back to the Greeks and Romans. And there were many prominent scientists of Darwin’s day that opposed the idea. (Curtis & Barnes)
Darwin was born in 1809 the son of an English gentleman. As a child, he loved collecting living things and rocks and loved horseback riding. He was encouraged to become a doctor but was horrified at the sight of seeing surgery on a child without using anesthetics. He then was a candidate for the clergy but that didn’t satisfy him. He was assigned to be the naturalist on the ship the HMS Beagle which left England on December 27, 1831 and returned home on October 2, 1836. (Robert McNamara)
The map of the journey follows.
Credit to: Sea and Sky
He sketched and collected hundreds of plants and animals along the way, especially from the Galapagos Islands. Upon arriving back in England he spent the next 25 years going over notes and observations and formulating his theories. After returning to England, Darwin read a treatise by Thomas Malthus in which he warned that the human population was increasing so fast that it would soon be impossible to feed everyone. Darwin applied this to all species and that food and other factors hold populations in check. (Curtis & Barnes) I am omitting a lot of important information to summarize nine postulates that Darwin used to explain how organisms evolve.
1. A population of organisms has the tendency and potential to increase at a geometric rate.
2. In the short run the number of individuals in a population remains fairly constant.
3. The conditions of life are limited. Limiting factors include food, water, living space, etc.) (my words)
4. The environments of most organisms have been in constant change throughout geologic time.
5. Only a fraction of the offspring in a population will live to produce offspring.
6. Individuals in a population are not all the sane. Some have heritable variations (variable traits).
7. Life activities (“struggle for existence”) determine which traits are favorable or unfavorable in determining the reproductive success of the individual who possesses the traits.
8. Individuals having favorable traits (variations) will, on average, produce more offspring and those without favorable traits will produce fewer offspring. Remember the viruses and bacteria from the last essay.
9. Natural selection caused the accumulation of new variations and the loss of unfavorable variations to the extent that a new species may arise. (Gibbs, A., A. Lawson)
I used to demonstrate artificial selection (human caused) by reaching into a jar (usually beaker) and pulling out M & M’s and if I pulled out a brown one (my favorite color), I would put it back and try until I withdrew a different color. I also had a small plastic bag with three candy corn kernels, two with a yellow tip and one with a white tip and asked what process was represented. You can find the answer at the end of the essay (below the references).
Note to readers. This is the end of volume I of Essays on Science for the Common Good. This is January 24, 2019(original date of publication ) and with nearly 10 inches of snow on the ground and more forecast for this weekend I am in ski mode (as much as my body will allow) and spending spare time in my biology/chemistry lab at home. I welcome comments good, bad, or indifferent and suggestions on how to improve my blog. Some possible topics for volume II may include:
· The Great Debate: Was it protein or DNA?
· The structure and physical properties of water that make it so important.
· Volume vs. surface area as they apply to physical and life sciences.
· A short treatise on such topics as the inverse square law, chill factor, heat index, dew point, humidity, relative humidity, (with definitions, energy conversions, and cause & effect relationships)
· Revisiting classification with power point notes (converted to essay format)
· A look into the State of Illinois RiverWatch program that I was a part of for many years. I am also toying with the idea of sharing some of my
· Favorite classroom jokes; I was famous (infamous?) for puns and groaners. On nonscientific subjects, I may offer an
· 11th year anniversary tribute to tragedy at my alma mater and share a
· Bitter-sweet tribute to a past pet as submitted several years ago to the Editors of Chicken Soup for the Soul (as yet unpublished).
References
Curtis, H. N. Sue Barness, (1989). Biology. New York: Worth Publishers Inc.
Gibbs, A. A. Lawson (1992) The Nature of Scientific Thinking As Reflected by the Work of Biologists & by Biology Textbooks, The American Biology Teacher, Vol. 54, NO. 3
McNamara, Robert Charles Darwin and His Voyage aboard H.M.S. Beagle Updated December 28, 2018
Answer: “Rock Around the Clock” by Bill Haley and the Comets
(Mutation)
Published by: Larry Baumer
I graduated from Northern Illinois University in 1966 with a Bachelor of Science degree in Education and earned a Master of Science degree in Education also from NIU in 1973. I taught in the Harlem School District (5 years), a Chicago suburb (1 year), and the Rockford, IL School District for 27 years (26 at East High School). I culminated my teaching career at Kishwaukee College (8 years) Two important events occurred in 1988: I married my wife Angie and I received a summer teacher’s research fellowship through the University of Illinois School of Medicine at Rockford. My primary responsibility was light microscopy and Scanning electron miscroscopy of rabbit renal arteries (effect of high cholesterol diet). For 14 years I was a citizen scientist for the Illinois Department of Natural Resources in their RiverWatch program (monitoring water quality) My hobbies and activities include gardening, golfing, bowling, downhill and cross country skiing, photography, including photomicroscopy and time lapse photography, spending time with my wife and our dog, and in the winter playing around in my small home biology & chemistry lab.
Beyond what I have written in past profiles, in the early 1980’s I was an EMT with the Boone Volunteer Ambulance & Rescue Squad (BVARS) which fit in nicely with my science training and teaching. I also enjoy public speaking and made frequent scholarship presentations to graduating seniors and outstanding middle school students through the former Belvidere Y’ Men’s Club. I also made power point presentations of the RiverWatch program. But I most enjoyed making presentations at my high school reunions. Thanks guys for allowing me to do this.
Part XX Water: What Makes it so Unique and so Important
“Water, water everywhere and all the boards did shrink,
Water, water everywhere, nor any drop to drink”
Those words learned so long ago from “The Rime of the Ancient Mariner” by Samuel Coleridge still ring in my ears like the day I memorized them in Miss Bennett’s 4th hour English IV class. I learned more from her about English grammar and literature than perhaps subject matter in any other high school class.
Water is the subject of this essay. I chose it because it (water) is so important in so many ways. It covers 75 percent of the earth’s surface, comprises 55-75 percent of our body depending on age and gender. It is necessary for life, and thus is one of the first considerations when looking for signs of life on other planets. But what makes it so important, what gives it its unique properties? Very few compounds have such an expansive temperature range in its liquid state. Very few compounds contract as they cool but then expand as they approach their freezing point as water does when it reaches 4 ͦC.
To find out the answers to those questions, we have to look at the structure of the water molecule in a way that some of you may never have done before. And, in the process we will visit chemistry and physics again.
Let’s start with some basic concepts of how chemical compounds are formed but first, a review of the three basic parts of an atom. Atoms have a nucleus in which are found one or more protons (+ charge) and one or more neutrons (except for hydrogen which has none and, therefore, is the lightest element) Neutrons have no net charge and, therefore, for our purpose are insignificant. Surrounding the nucleus are one or more energy levels containing electrons which have a negative charge. In terms of compound formation electros are the star players and everything else plays just a supporting role. The first energy level can hold a maximum of two electrons and the second level a maximum of eight. In some compounds like table salt (NaCl) sodium has 11 electrons (2, 8, 1) and chlorine has 17 electrons (2, 8, 7). Now since the goal is always to have the outer energy level filled it is much easier for the sodium atom to lose its one outer level electron than for chlorine to lose seven and so that is just what happens and sodium chloride (salt) is formed with totally new chemical and physical properties. But if you dissolve that salt in water it will dissociate into Na+ (ions) + Cl– (ions) and because it lost its negatively charged electron, it now still has 11 plus charges (protons) but only 10 negative charges. Chlorine, on the other hand, gained a – charge and now has 18 negative charges. A chemical bond was formed and we call such a bond resulting from a transfer of election(s) an ionic bond. Atoms that have gained or lost one or more electrons are called ions.
Credit to: Spreadshirt.com
Water, on the other hand forms from a sharing of electrons. Written as H2O or H-O-H (the lines indicate chemical bonds). An important word about chemical bonds: they store energy, when bonds are formed energy is stored, when bonds are broken energy is released. Remember from essays VII and VIII, the former is an example of anabolism and the latter is an example of catabolism.
Hydrogen has one outer energy electron and oxygen has 6 but could hold 8. With two hydrogen atoms, each of which has one electron and the six from the oxygen atom we have the desired eight. But as I used to tell my students, the big bully oxygen atom agrees to share its six electrons but keeps the two hydrogen electrons most of the time thereby creating four areas of charges on the overall water molecule, 2 negatives around itself from the extra hydrogen atom’s electrons, plus the 6 from own atom, Meanwhile having partially lost their electrons the hydrogen atoms have a slightly + charge on their end. This unequal sharing of electrons is a covalent bond. Thus the water molecule is slightly polar which is super important. That is responsible for many of its physical properties. For instance, that creates an attraction to four other water molecules and is responsible for a high surface tension which enables some insects like water striders to walk on the surface, and kids (adults too) to “skip” stones on water. There is even a certain lizard (which I won’t give you the common name of) that can even do the same.
Credit to: Pineterest.com
Credit to: Rutgers
That is also part of the reason water and drinks made from water as the solvean be sucked up in a straw and can rise to the top of very tall trees through microscopic tubes (xylem, the wood). There are, of course, other reasons for this too. But to catch up on terms here, the attraction of water molecules to each other is called cohesion, the attraction of water molecules to the sides of the straw, xylem tubes , or to glass, for that matter, is called adhesion, and the two forces together is called capillarity. If you’ve ever had two wet water glasses one inside the other get stuck, you know what I mean. And finally, the bond between water molecules is called a hydrogen bond (between a hydrogen atom of one molecule and an oxygen atom of another). During a review after we had studied this I would ask for the named of a fourth bond and, of course, no one knew. Then I would say “you mean you’ve never heard of James Bond”?
Water has a high heat of vaporization which means that it has a high boiling point. A calorie is defined as the amount of heat energy needed to raise the temperature of 1 gram of water 1 ֯ C. That’s a lot of energy compared to many other compounds. Why is this? It takes a lot of heat to break all those hydrogen bonds. Thus the saying “a watched pot never boils”. Not true, of course, it just seems that way. Changing 1 gram of liquid water to a gas requires an input of 540 calories. That’s huge and is called the heat of vaporization. So what does this mean and why is it significant? It means that water loses its heat very slowly, gains heat very slowly and freezes very slowly and at a very low temperature. The ramifications for living organisms internally and externally are almost endless. It also means that large bodies of water are the great equalizers of air temperature over solid land. Thus Seattle, Washington even through at a higher latitude than Omaha, Nebraska has more moderate temperatures year round and Chicago lakefront temperatures change less that the suburbs. This also allows animals to cool off by dunking themselves in bodies of water. It is also the reason why we feel cool when we step out of a pool or shower. We lose body heat as evaporation takes place on the surface of the skin. Note that it takes an input of 80 calories of heat to melt 1 gram of water which is also a lot of energy. Incidentally, the freezing and thawing of water has some serious implications for all drivers who have often experienced potholes in the temperate climate zones.
Water is called the universal solvent which means so many substances dissolve in it. That’s good since virtually all of the thousands of chemical reactions that must occur in our bodies need to be in solution. Exceptions include all lipids (fats, oils, etc.) which as you night guess are monopolar compounds. Finally unlike most substances, ice is less dense than liquid water which means that ice floats on water. Otherwise, bodies of water would freeze from the bottom up. Think about the consequences, especially in nature if it weren’t less dense. That happens because water unlike other liquids begins to expand at 4 ͦC. just before it freezes. Ever had to deal with frozen pipes?
Let’s review the important properties of water:
Water expands as it freezes
Ice is less dense than liquid water
Water is the universal solvent
You may think I’m all wet for writing this essay but it is good scientific knowledge based on principles of physics and chemistry.
References
Mader, S. Biology, (2004 eighth edition), McGraw Hill, Boston, MA
I graduated from Northern Illinois University in 1966 with a Bachelor of Science degree in Education and earned a Master of Science degree in Education also from NIU in 1973. I taught in the Harlem School District (5 years), a Chicago suburb (1 year), and the Rockford, IL School District for 27 years (26 at East High School). I culminated my teaching career at Kishwaukee College (8 years) Two important events occurred in 1988: I married my wife Angie and I received a summer teacher’s research fellowship through the University of Illinois School of Medicine at Rockford. My primary responsibility was light microscopy and Scanning electron miscroscopy of rabbit renal arteries (effect of high cholesterol diet). For 14 years I was a citizen scientist for the Illinois Department of Natural Resources in their RiverWatch program (monitoring water quality) My hobbies and activities include gardening, golfing, bowling, downhill and cross country skiing, photography, including photomicroscopy and time lapse photography, spending time with my wife and our dog, and in the winter playing around in my small home biology & chemistry lab.
Beyond what I have written in past profiles, in the early 1980’s I was an EMT with the Boone Volunteer Ambulance & Rescue Squad (BVARS) which fit in nicely with my science training and teaching. I also enjoy public speaking and made frequent scholarship presentations to graduating seniors and outstanding middle school students through the former Belvidere Y’ Men’s Club. I also made power point presentations of the RiverWatch program. But I most enjoyed making presentations at my high school reunions. Thanks guys for allowing me to do this.
The story of the true carrier of genetic information from generation to generation is an interesting tale which followed a winding path from the late 1800’s up to 1953 and even that historic discovery, while one of the most sought after and important discoveries of human kind, was really just a new chapter in the book of life as we know it that continues today and undoubtable will as long as human civilization exists.
The story really begins in 1869 when a German physician Fredrich Miescher discovered a white, sugary, slightly acidic substance that contained phosphorus. He named it “nuclein” based on its presence only in the nucleus of cells. Fast forward to 1914the year that Prince Ferdinand of Austria was assassinated thus beginning “The Great War” (World War I) Robert Fuelgen, another German, found that DNA was strongly attracted to fuchsin, a red dye. Just a small step but helpful one. Later it was discovered that DNA was present in all cells and was associated with the chromosomes which had only recently been discovered. Let’s take a small “aside” now and delve a little further into the world of the chromosome. Oscar Hertwig, yet another German (an embryologist) observed sea urchin fertilization and realized that only one sperm cell was necessary to fertilize an egg and further noted that when the sperm cell penetrated egg the nuclei from the sperm and egg fuse. This established that the nucleus, or something in it, is the carrier of genetic information from generation to generation, another small step. At about the same time, Walther Flemming observed the “dance of the chromosomes” during cell reproduction, “steps” of mitosis (cell division), and the events of each step. Of course, in reality, the process is continuous and people devised the “steps” to understand the process better. To learn more including the phases such as prophase, metaphase, anaphase, telophase, etc., simple Google “mitosis” or “cell division” or consult any high school biology textbook. In one experiment Flemming removed the nucleus of an ameba (amoeba for our British friends) and watched the cell die.
P.A. Levene, a biochemist proved in the 1920’s that DNA was composed of a 5- carbon sugar (a pentose); a phosphate group, and four nitrogenous bases, adenine and guanine (purines) and thymine and cytosine (pyrimidines). He concluded that each nitrogenous base is connected to a sugar molecule which is attached to a phosphate group which makes up a nucleotide. (See essay IX Majors)
In 1928, Frederich Griffith, an English bacteriologist public health official was trying to develop a vaccine against Streptococcus pneumonia which causes a form of pneumonia. This bacterium comes in two forms, one a virulent (disease causing) form with a polysaccharide (simple sugar capsule and a nonvirulent (harmless) none capsulated form. Griffith wanted to know if injections of heat killed virulent pneumoiae could be used to immunize against pneumonia. At one point he injected mice simultaneously with heat kicked virulent bacteria and living non-virulent bacteria expecting the ice to live but all the mice died—a complete surprise. Autopsies on the mice revealed that their bodies were filled with living encapsulated virulent bacteria. Years later it was shown that extracts from heat killed virulent bacteria when added to harmless bacteria could transform them into harmful bacteria complete with protective capsules. Thus an extremely important phenomenon called transformation was discovered and the yet unknown substance responsible for this transformation was called a transforming factor. (“Factor” is still used to refer to an unknown substance). Later this transforming factor was identified as—you guessed it—DNA. When I presented this in class I usually describe the heat killed bacteria as never-say-die KILLER BACTERIA for dramatic effect. It was an American scientist, O. T. Avery that identified DNA as the transforming factor.
At this point it must seem like DNA was the overwhelming candidate for carrying the genetic information from generation to generation—but, hold on, don’t count the other contender out yet. Max Delbruck and Salvador Luria two scientists who emigrated from Europe during the intellectual mass exodus of the 1930’s along with Albert Einstein,
And other mathematicians and physicists prior to the Third Reich takeover of 1939performed some Nobel Prize experiments in 1940 with a special group of viruses called bacteriophages or simply phages because they infect bacteria. Yes, even bacteria have enemies. The particular viruses of interest in their research ae called coliphage and they attach Escherichia coli. They were numbered T1 through t7 (“T” means “type”). In a personal note here I very recently inoculated E. coli bacteria with T4 coliphage in my home lab attempting to do a T4 assay, See the photo below.
Skipping the details of the experiments, chemical analysis of fragments of phages after infection revealed what we all know now – that viruses are composed of just two organic compounds, a DNA core and a protein coat. Later RNA was also discovered in the core but if so DNA is absent (see essay IX). So now the great debate ha had been brewing for years suddenly intensified. What carried the all-important genetic code, DNA or protein? Scientists were divided into two camps. The protein backers had a very simple philosophy: DNA is composed of just 4 nucleotides but proteins are composed of 20 amino acids (see essay IX). They reasoned that like an alphabet composed of 20 letters could spell more words than one with 4 letters, so proteins could account for greater genetic variability (diversity).
The stage was now set for the most compelling evidence yet. In 1952 two researchers Alfred Hershey and Martha Chase performed a brilliant set of experiments based on two simple differences in DNA and proteins. But first I always made a point of emphasizing that like Rosiland Franklin, Martha Chase was a pioneer in that here was a woman that rose to prominence in a field dominated by men and they could do the same much to their delight. OK, another personal aside here.
A few years ago (2013), I ran into a former student in a local Kohl’s Department Store. She also became a lab assistant and a very good one who earned her degree at the University of Iowa and now was doing scientific research at Marquette University. She told me that she got her start after being my student and lab assistant. Talk about delight! I was on cloud 9 at a time I was going through a long, tough, tough time medically. Then she topped it off by saying that I looked the same as I did when I was her teacher in the mid ‘80’s. This was at a time when I looked terrible and felt much worse.
Back to Hershey and Chase: DNA as we know, contain phosphorus but proteins don’t. Proteins contain sulfur but DNA doesn’t. They prepared two groups of viruses, one which was labeled with radioactive phosphorus (32P)and one labeled with radioactive sulfur (35S) and inoculated then into an E. coli host with the appropriate radioactive isotope. Again skipping some of the details one culture of bacteria was infected with 32P and another infected with 35Sphage and later were tested for radioactivity. Their brilliantly conceived experiments revealed that the 35S phages had remained outside the bacterial cells but the 32P (DNA) had entered the cells, infected the bacteria and produced new viruses. The great debate was essentially over; DNA was proclaimed the winner.
Conclusion
Aftermath
Erwin Chargaff of Columbia University analyzed the purine and pyrimidines content from many different species of organisms. Here is a sample of his results showing percentages of the four bases.
Human 30.4% 19.6% 19.9% 30.1% Ox 29.0 21.2 21.1 28.7
Wheat germ 28.1 21.8 22.7 27.4
after examining the data what can you conclude? Answer as usual at the end of the essay.
It is almost anticlimactic to now talk about James Watson and Francis Crick’s famous discovery in 1953. Watson, a former Whiz Kid from Chicago was going to become an ornithologist but thankfully changed careers. Francis Crick, a trained physicist were an unlikely fil for one of the most important discoveries in the history of science. Rather than swell on their work which would extend this very long essay much longer I would recommend reading a form of Watson’s famous book “The Double Helix” and again read the last p [art of essay IX (majors). I have read his book at least three times and learned more each time. It’s written so that most ordinary people can understand it with just a little science background. If you can/t or don’t want to read the book (a short one in terms of book length, I would suggest Googling “The Double Helix”.
I briefly described protein synthasis in essay IX but now direct you to a “code of life chart”. One of the main mysteries to be delved was “breaking the code”, that is, to learn how
DNA directs:
its own replication
protein synthesis
Now that we know DNA directs protein synthesis let’s look in more detail at the overall process. According to “central dogma”, a term that Crick himself coined, during protein synthesis the double stranded DNA molecule splits down the middle (hydrogen bonds break releasing emery) and each side serves as a template for a strand of messenger RNA (mRNA with the cytocine of DNA coding for a guanine of mRNA and adenine of DNA coding for uracil of mRNA. Remember that thymine in DNA is replaced by uracil in RNA. However, thymine of DNA still codes for adenine of RNA. This whole process is called transcription, a process that occurs in the nucleus. The single stranded mRNA leaves the nucleus and pairs with a transfer RNA (tRNA) which contains an amino acid (the building block of proteins) on one end and an attachment on the other end to enter a ribosome (ribosomal RNA or rRNA). As stated in an earlier essay, it’s as if the mRNA molecule says to the tRNA, “let’ meet at the ribosome (more correctly let’s go to the ribosome) and make a protein”, a process called translation. The long strand of mRNA can be thought of as individual units of codons (three nitrogenous bases per codon) that like transcription from DNA, pairs with the corresponding anticodon on the tRNA molecule. That is, a u from mRNA pairs with an a of tRNA, c with g, g with c, etc. Remember though an a pairs with a u of tRNA. Why? The individual tRNA subunits join together inside the ribosome (rRNA) and exit out in long polypeptide chains which when long enough and exhibit secondary structures and perhaps tertiary and quaternary structures are called proteins. But remember, and this is huge, it all began with DNA.
Let’s pause for a moment and reflect on some important principles.
DNA is composed of 4 nucleotides, a four letter alphabet (the four nitrogenous bases)
There are 20 amino acids commonly found in living organisms
Codons (and, therefore, anticodons) occur in triplets
Now the question arises of why groups of 3 bases in a codon? Why not 1 or 2?
Answer:
Individual codons could code for only 4 amino acids. (41) 4 bases raised to fist power if just one individual base
Pairs of codons could produce only 16 amino acids (42)
Triplets could produce 64 amino acids (43) 4x4x4= 64 which is more than enough for the 20 amino acids In fact, this means that there must be more than one codon that can code for each amino acid, right? Right.
Now we are ready for the ultimate task and the climax of this entire essay and perhaps all of my essays except for perhaps those on climate change. Identifying the correct structure of the DNA molecule is one thing but to apply it to genetics and understand how I works in specifying the production of the thousands of chemical compounds and chemical reaction each with its own enzyme in our bodies is a totally different set of circumstances. But let’ proceed. Here is the “code of life” chart that summarizes (I didn’t say explains) all of the previous sentences.
chemguide.co uk
The letters along the left side, top, and right side represent the 4 bases. You know their names by now. The letters (in triplet) represent the codons and the abbreviation of individual amino acids. To select amino acids:
choose a letter on the left side
choose a letter on top
choose a letter on the right side
write them down and identify the amino acid using the listing below using the abbreviations.
As promised in Essay XII. I am now ready to offer my opinion concerning climate change, commonly called global warming and the effects of the human imprint on the environment. The first part of this essay consists of another letter to the Rockford Register Star now called “My View”
A few years ago I wrote a “Letter to the Editor” in response to a letter by a skeptic. That letter inspired a series of essays which this year became a blog. My website is called lessonsonscience.com but a better way to access it is simply to Google Essays on Science for the Common Good. I encourage you to read all of the first eleven essays plus the preface and outline but a few of them do go into some detail on some of the topics which now are aimed primarily at high school or college biology students.
I have converted my major points to bold print. Concerning the human imprint on the environment, let us turn to essay XIII. I would ask any doubter, ”Do you believe that temperatures on a world-wide basis are increasing and if so what are the factors (causes) if not from anthropogenic (human) effects of increased greenhouse gases?” To this I suggest reading essay XIV, especially paragraphs 1 and 4. A basic premise is that photosynthesis removes CO2 from the atmosphere and any process that returns CO2 to the air such as cellular respiration, decay, and burning fossil fuels at a faster rate than what photosynthesis removes is a bad thing since it offsets the normal ecological balance of the two processes. See essays VII and VIII.
It is essential that we understand some terms before proceeding further.
Greenhouse effect: light and heat from the sun enters the atmosphere striking the earth’s surface where some is absorbed by surface features and converted into other forms of energy such as chemical energy of food. Some is radiated back into space, and some is trapped in the atmosphere by clouds and various pollutants thereby raising the temperature similar to a hothouse or greenhouse, thus the term “greenhouse effect”.
· Global warming: the cumulative result of the greenhouse effect on a worldwide basis
· “The transfer rate of carbon from the atmosphere by photosynthesis just about equals the rate at which respiration and decay return carbon to the atmosphere. However, when fossil fuel burning is added to the equation, the rate of CO2 returned to the atmosphere is greatly favored.”
In 1991 the National Association of Biology Teachers (NABT) adopted the following position.
Causes of Climate Change
1. Increased use of fossil fuels
2. Increased rate of deforestation, resulting in less carbon “locked up” in the forest
3. Increased amount of “greenhouse gases” (CO2,CH4 (methane), N2O (nitrous oxide), CFCs (chlorofluorocarbons)) causing the atmosphere to absorb radiant heat
4. Growth of the human population as it affects all of the above
Consequences of Global Warming .
1. Shifting of agriculture zones
2. Desertification and local mass extinction
3. Changes in animal migration patterns
4. Sea levels rise as a result of melting polar ice and thermal expansion in the oceans, which can cause destruction of human structures and natural habitats along sea coasts
And finally: This experiment (global warming) essentially began at the beginning of the Industrial Revolution. Since then we have increased the atmospheric content of carbon dioxide by about 25 percent by burning oil, coal, and other fossil fuels
The October 19, 2008 issue of the Rockford Register Star article “On thin ice” says “the Arctic Ocean is recording record temperatures as the ocean is getting warmer and less salty as ice melts”. Also from essay XIV: The graph below shows ice core data charting average temperature from the past thousand years in the Northern Hemisphere. The line at 0.0 represents average temperature from 1961 to1990. Any year with an average temperature below the 0.0 line was colder than average and is shown in blue; any year with an average temperature above the 0.0 line was warmer than average and is shown in red”. I’ll let the reader draw your own conclusions.
Remember, more people on the planet means more greenhouse gases and more tipping of the photosynthesis / carbon dioxide returned balance.
If the past six essays haven’t opened your eyes to the reality of global warming and the role humans play, nothing that I write here will change your mind. You certainly can’t claim ignorance, only stubbornness to accept the truth. Years and years of tough honest research have produced the undeniable evidence that we now have. Science isn’t political; it doesn’t exist to serve political ambitions of some power hungry individuals. It seeks truth wherever that leads. It doesn’t seek to make headlines. Re-read essay II if necessary
Another cornerstone of physics, chemistry and biology comes to mind, the second law of thermodynamics which states that in all energy conversions, if no energy enters or leaves a system, the potential energy of the final state (products) will always be less than the identical energy of the initial state (reactants). Specifically I am referring to entropy which is a measurement of the disorder or randomness of a system.
Thus, molecules move from an area of high pressure to an area of low pressure and your desk, closet, or room go from order to disorder (organized to messy]. The universe and our world slowly wind down. The photosynthesis /respiration / decay balance favors the reverse direction-and disorder ensues.
I could write more, especially a synopsis of past agreements such as the 1997 Kyoto Protocol, the Paris Agreement of 2015 and the recent talks in Katowice, Poland, but most of the agreements that rely less on fossil fuels, although well intended, have been a dismal failure.. Let’s face it, a world that has seen countless wars including two World Wars and can’t solve other problems will be hard pressed to resolve this one, especially if left to governments such as our own (we are one of the two largest contributors of greenhouse gases) and to leaders who also refuse to “see the truth” (also our own). Controlling global warming has to be a grassroots effort. We all leave a carbon “footprint” every day of our lives. Changes must come from a cooperative effort of the scientific community, inventors, businessman, governments, and, most of all a will to leave a better world for future generations. As I said in an earlier essay “God gave us a mind to ask the right questions.” In closing I leave you with a collage of newspaper article titles
Coal question looms large as climate talks begin in Poland
Nations reach deal on gases
UN chief says climate change is the most important issue we face
Coal question looms large as climate talks begin in Poland
GOP victory: Game over for the climate?
Obama to plead U. S. case at global war summit
Historic conference opens with 197 nations: big news
Climate change is here and getting worse
U. S. China reach landmark climate dealReport this
As promised in Essay XII. I am now ready to offer my opinion concerning climate change, commonly called global warming and the effects of the human imprint on the environment. The first part of this essay consists of another letter to the Rockford Register Star now called “My View”
A few years ago I wrote a “Letter to the Editor” in response to a letter by a skeptic. That letter inspired a series of essays which this year became a blog. My website is called lessonsonscience.com but a better way to access it is simply to Google Essays on Science for the Common Good. I encourage you to read all of the first eleven essays plus the preface and outline but a few of them do go into some detail on some of the topics which now are aimed primarily at high school or college biology students.
I have converted my major points to bold print. Concerning the human imprint on the environment, let us turn to essay XIII. I would ask any doubter, ”Do you believe that temperatures on a world-wide basis are increasing and if so what are the factors (causes) if not from anthropogenic (human) effects of increased greenhouse gases?” To this I suggest reading essay XIV, especially paragraphs 1 and 4. A basic premise is that photosynthesis removes CO2 from the atmosphere and any process that returns CO2 to the air such as cellular respiration, decay, and burning fossil fuels at a faster rate than what photosynthesis removes is a bad thing since it offsets the normal ecological balance of the two processes. See essays VII and VIII.
It is essential that we understand some terms before proceeding further.
Greenhouse effect: light and heat from the sun enters the atmosphere striking the earth’s surface where some is absorbed by surface features and converted into other forms of energy such as chemical energy of food. Some is radiated back into space, and some is trapped in the atmosphere by clouds and various pollutants thereby raising the temperature similar to a hothouse or greenhouse, thus the term “greenhouse effect”.
Global warming: the cumulative result of the greenhouse effect on a worldwide basis
“The transfer rate of carbon from the atmosphere by photosynthesis just about equals the rate at which respiration and decay return carbon to the atmosphere. However, when fossil fuel burning is added to the equation, the rate of CO2 returned to the atmosphere is greatly favored.”
In 1991 the National Association of Biology Teachers (NABT) adopted the following position.
Causes of Climate Change
Increased use of fossil fuels
Increased rate of deforestation, resulting in less carbon “locked up” in the forest
Increased amount of “greenhouse gases” (CO2,CH4 (methane), N2O (nitrous oxide), CFCs (chlorofluorocarbons)) causing the atmosphere to absorb radiant heat
Growth of the human population as it affects all of the above
Consequences of Global Warming .
Shifting of agriculture zones
Desertification and local mass extinction
Changes in animal migration patterns
Sea levels rise as a result of melting polar ice and thermal expansion in the oceans, which can cause destruction of human structures and natural habitats along sea coasts
And finally: This experiment (global warming) essentially began at the beginning of the Industrial Revolution. Since then we have increased the atmospheric content of carbon dioxide by about 25 percent by burning oil, coal, and other fossil fuels
The October 19, 2008 issue of the Rockford Register Star article “On thin ice” says “the Arctic Ocean is recording record temperatures as the ocean is getting warmer and less salty as ice melts”. Also from essay XIV: The graph below shows ice core data charting average temperature from the past thousand years in the Northern Hemisphere. The line at 0.0 represents average temperature from 1961 to1990. Any year with an average temperature below the 0.0 line was colder than average and is shown in blue; any year with an average temperature above the 0.0 line was warmer than average and is shown in red”. I’ll let the reader draw your own conclusions.
Remember, more people on the planet means more greenhouse gases and more tipping of the photosynthesis / carbon dioxide returned balance.
If the past six essays haven’t opened your eyes to the reality of global warming and the role humans play, nothing that I write here will change your mind. You certainly can’t claim ignorance, only stubbornness to accept the truth. Years and years of tough honest research have produced the undeniable evidence that we now have. Science isn’t political; it doesn’t exist to serve political ambitions of some power hungry individuals. It seeks truth wherever that leads. It doesn’t seek to make headlines. Re-read essay II if necessary
Another cornerstone of physics, chemistry and biology comes to mind, the second law of thermodynamics which states that in all energy conversions, if no energy enters or leaves a system, the potential energy of the final state (products) will always be less than the identical energy of the initial state (reactants). Specifically I am referring to entropy which is a measurement of the disorder or randomness of a system.
Thus, molecules move from an area of high pressure to an area of low pressure and your desk, closet, or room go from order to disorder (organized to messy]. The universe and our world slowly wind down. The photosynthesis /respiration / decay balance favors the reverse direction-and disorder ensues.
I could write more, especially a synopsis of past agreements such as the 1997 Kyoto Protocol, the Paris Agreement of 2015 and the recent talks in Katowice, Poland, but most of the agreements that rely less on fossil fuels, although well intended, have been a dismal failure.. Let’s face it, a world that has seen countless wars including two World Wars and can’t solve other problems will be hard pressed to resolve this one, especially if left to governments such as our own (we are one of the two largest contributors of greenhouse gases) and to leaders who also refuse to “see the truth” (also our own). Controlling global warming has to be a grassroots effort. We all leave a carbon “footprint” every day of our lives. Changes must come from a cooperative effort of the scientific community, inventors, businessman, governments, and, most of all a will to leave a better world for future generations. As I said in an earlier essay “God gave us a mind to ask the right questions.” In closing I leave you with a collage of newspaper article titles
Coal question looms large as climate talks begin in Poland
Nations reach deal on gases
UN chief says climate change is the most important issue we face
Coal question looms large as climate talks begin in Poland
GOP victory: Game over for the climate?
Obama to plead U. S. case at global war summit
Historic conference opens with 197 nations: big news
• Biodiversity – usually defined as the variety of living organisms in a given area or in a particular habitat ecosystem. That area can be as small as a drop of water or as larger as the world.
• Habitat – the place where an organism lives. It can be described generally such as a forest or specifically such as a certain kind of a host cell or cell part such as the fatty coating of a nerve cell (myelin sheath).
•. Ecosystem – a biological community of organisms interacting with each other and their physical environment; again it can be very small such as a rotting log or leaf pack or large, for example, a lake.
Loss of biodiversity can be devastating. For example, in 2016 up to 50 percent of the northern portion of the Great Barrier Reef off the coast of Australia was killed by a heat wave, triggered by global warming. This, the world’s largest reef, is home to a myriad of species of plants and animals, many of them unique; a popular diving and tourist area which generates over $3 billion annually was threatened.
It is not unusual for organisms to become extinct. It happens all the time; check the geologic table in essay VI for examples of past extinctions. In fact, it is estimated that perhaps 99 percent of all species that have ever existed are now extinct. However, the current rate extinction is perhaps 1,000 times that of pre-human rates.
As suggested in earlier essays, the Earth depends upon a delicate balance of forces to remain a healthy place to live. We humans consume more resources than what the Earth can supply by a ratio of about 1.7:1.
How does climate change affect our health?
June of 2018 was the hottest month ever recorded throughout much of the Northern Hemisphere. According to J. Maichle Bacon a former Winnebago County (IL.) Health Department Administrator, “the evidence connecting greenhouse gas emissions with increasing extremes in global climate is overwhelming, threatening both current and future ecological systems’ sustainability upon which health and well-being depend.” According to Bacon, health consequences are classified into three categories by the Intergovernmental Panel on Climate Change (IPCC). They are primary, secondary, and tertiary. Primary considerations include injuries, physical and psychological disabilities and loss of life from temperature extremes, increasing ultraviolet radiation, floods, (frequency and severity) high winds, hurricanes (again frequency of and severity), and increased wildfires. Consequences result from the trauma of separation from loved ones, disruption of health services, disease, dehydration, lack of proper nutrition, post-traumatic stress, depression, and adjustment disorders.
Secondary health consequences result from changing biological systems in a negative way upon which our health and wellbeing depend. Climate change influences the interaction of plant, animal, and microbial viability and geographic range. This in turn affects human activities such as commerce, land use, agricultural yields, air and water quality, etc.
In this country alone 40 percent of the counties report periods of poor air quality which adds up to 55,000 premature deaths, heart disease, cancer, and chronic respiratory diseases.
Tertiary health effects result from current climate trends affecting the sustainability of water systems, agricultural production, and biodiversity which all lead to famine, social disruption, displacement, increased violence, and increased global stability.
The good news is most or all of the consequences can be reduced if we (all human inhabitants) work to:
· Reduce greenhouse gas emissions by decreasing our reliance on gas, oil, and coal
· Increase energy conservation
· Decrease energy waste
· Increase renewable energy resources such as wind solar, and nuclear (Bacon, M. Rockford Register Star, 7/15/2018)
Eugene Johnson writes in a column recently that Hurricane Florence dumped more than 30 inches of rain, an all-time record on North Carolina. Last year Hurricane Harvey drenched Houston with more than 60 inches of rain. Climate scientists predict that global warming should make such storms wetter, slower and more intense. We know from direct evidence that:
· The concentration of carbon dioxide, {CO2} has increased by 40 percent since the beginning of the Industrial Revolution
· Carbon dioxide and other greenhouse gases trap heat
· Warmer water takes up more space than cooler water which is the main reason why ocean levels are rising
· Warmer water evaporates faster than cooler water thereby adding more moisture available to fuel storms The current administration has already proposed weakening restrictions on carbon emissions from automobiles and coal-fired power plants.
As a final anecdote, recently a cargo ship is currently making the journey from Vladivostok, Russia to Bremerhaven, Germany via the Arctic Ocean instead of the usual southern route through the Suez Canal and the Strait of Gibraltar. Until now the northern route has been impassible, a great savings, no doubt for the ship company but at what a price!
In the last essay I wrote about the death of algae during the bleaching of coral reefs. On the flip side of the coin, warmer waters can lead to bloom that results in so called “dead zones” which is caused by an explosion of algae and aided by pollution from human activities on land.
As I write this essay a friend who just returned from Florida told us that the “red tide “ is back with vengeance The Florida red tide is caused by Karenia brevis (division Dinoflagellata), a single celled alga with two flagella (long whip-like “hairs”, one of which encircles the cell horizontally and the other perpendicular to the first). They function like a gyroscope to spin the cell like a top (Curtis, Barnes 1989). Another division is Rhodophyta, (rhodo- meaning red and –phyta meaning plant) which is a throwback to an earlier time when algae were classified as plants (see essay XI)). The red color is due to the predominance of the pigment phycerythrin which absorbs blue light. This gets into the physics of light that my students never seemed to understand. For example, a blue wall appears blue because the paint absorbs all the other color frequencies of the visible spectrum and reflects blue back to your eyes. Sunlight (white light) is composed of all seven colors (now apparently divided into eight colors of the rainbow). And, of course, the absence of light results in black. Back to the red tide; the toxins they produce are ingested by algae eaters and pass through the food chain eventually reaching humans. Thus a severe red tide invasion can have serious economic consequences,
As the climate gets warmer, disease carrying species move into new places. Living organisms that carry infectious diseases include:
• Algae
• Mosquitoes
•. Tsetse flies
• Ticks
• Lice
• Fleas
• Snails
• Bats
• Rodents
This is certainly not an all-inclusive list.
Most people would agree that colder winter days and nights help to check the spread of disease. For example mosquitoes breed in warmer moist climates. Malaria, encephalitis, West Nile virus, and yellow fever are common diseases in which various species of mosquitoes are the vector. West Nile virus entered the United States in 1999 and within four years had covered the entire North American Continental (Gore, A. 2006).
Here is another consideration. Colder winters in western states previously slowed down the spread of pine beetles which bore into tree trunks to lay their eggs. With fewer days of frost, they are ramping up their destruction of pine trees. Other species are being threatened with extinction due to environmental change which may favor other new species that can adapt. This is a classic example of natural selection and survival of the fittest. Rain forest destruction, as one example destroys habitats and is a major player in species extinction. Even building roads, dams, bridges, etc. can separate species and cause geographic isolation. More on that and related phenomena will come in the next major topic. Stay tuned.
