bioluminescence in fungi

INTRODUCTION What is Bioluminescence? The current paper main focus is on bioluminescent Fungi but the basic features of bioluminescence discussed are common to all bioluminescent organisms. Bioluminescence is simply light created by living organisms. Probably the most commonly known example of bioluminescence by North Americans is the firefly, which lights its abdomen during its mating season to communicate with potential mates. This bioluminescent ability occurs in 25 different phyla many of which are totally unrelated and diverse with the phylum Fungi included in this list (an illustration of a bioluminescent fungi is displayed in figure 1). One of the features of biological light that distinguishes it from other forms of light is that it is cold light. Unlike the light of a candle, a lightbulb, bioluminescent light is produced with very little heat radiation. This aspect of bioluminescence especially interested early scientists who explored it. The light is the result of a biochemical reaction in which the oxidation of a compound called "Luci ferin" and the reaction was catalyzed by an enzyme called "Luciferase". The light generated by this biochemical reaction has been utilized by scientists as a bioindicator for Tuberculosis as well as heavy metals. On going research involving bioluminescence is currently underway in the areas of evolution, ecology, histology, physiology, biochemistry, and biomedical applications. History of Bioluminescent Fungi The light of luminous wood was first noted in the early writings of Aristotle which occurred in 382 B.C.(Johnson and Yata 1966 and Newton 1952) The next mention of luminous wood in the literature occurred in 1667 by Robert Boyle who noticed glowing earth and noted that heat was absent from the light. Many early scientists such as Conrad Gesner, Francis Bacon, and Thomas Bartolin all observed and made notation of luminous earth(Johnson and Yata 1966 and Newton 1952 ). These early observers thought that the light was due to small insects or animal interactions. The first mention that the light of luminous wood was due to fungi occurred from a study of luminous timbers used as supports in mines by Bishoff in 1823. This opened the way for further study by many other scientists and by 1855 modern experimental work began by Fabre ( Newton 1952). Fabre established the basic parameters of bioluminescent fungi, those being: • The light without heat • The light ceased in a vacuum, in hydrogen, and carbon dioxide • The light was independent of humidity, temperature, light, and did not burn any brighter in pure oxygen The work by Herring (1978) found that the luminescent parts of the included pileus(cap), hymenium(gills) and the mycelial threads in combination or separately(figure 2) also the individual spores were also seen to be luminescent. Herring also stated that if the fruiting body (mushroom) was bioluminescent then the mycelial threads were always luminescent as well but not vice versa. From the 1850's to the early part of the 20th century the identification of the majority of fungal species exhibiting bioluminescent traits was completed. The research of bioluminescent fungi stagnated from the 1920's till 1950's (Newton 1952 and Herring 1978 ). After which extensive research began involving the mechanisms of bioluminescence and is still carried out to the present. The Process of Bioluminescence Bioluminescence results because of a certain Biochemical reaction. This can be described as a chemiluminescent reaction which involves a direct conversion of chemical energy transformed to light energy( Burr 1985, Patel 1997 and Herring1978). The reaction involves the following elements: • Enzymes (Luciferase) - biological catalysts that accelerate and control the rate of chemical reactions in cells. • Photons - packs of light energy. • ATP - adenosine triphosphate, the energy storing molecule of all living organisms. • Substrate (Luciferin) - a specific molecule that undergoes a chemical charge when affixed by an enzyme. • Oxygen - as a catalyst A simplified formula of the bioluminescent reaction: ATP(energy) + Luciferin (substrate)+ Luciferase(enzyme) + O2(oxidizer) == == light (protons) The bioluminescent reaction occurs in two basic stages: 1) The reaction involves a substrate (D-Luciferin), combining with ATP, and oxygen which is controlled by the enzyme(Luciferase). Luciferins and Luciferase differ chemically in different organisms but they all require molecular energy (ATP) for the reaction. 2) The chemical energy in stage one excites a specific molecule (The Luminescent Molecule: the combining of Luciferase and Luciferin). The excitement is caused by the increased energy level of the luminescent molecule. The result of this excitement is decay which is manifested in the form of photon emissions, which produces the light. The light given off does not depend on light or other energy taken in by the organism and is just the byproduct of the chemical reaction and is therefore cold light. The bioluminescence in fungi occurs intracellulary and has been noted at the spore level(Burr 1985, Newton 1952 and Herring 1978). This may at times be mistaken for a extracellular source of light but this is due to the diffusion of the light through the cells of the fungus. In examining the photograph in figure 1, it appear that the cap of the fungus is glowing but after study, it was observed that just the gill structures that emits the light and the cap (which is thin) emits the light of the gills by diffusion(Herring 1978). The energy in photons can vary with the frequency (color) of the light. Different types of substrates(Luciferins) in organisms produce different colors. Marine organisms emit blue light, jellyfish emit green, fireflies emit greenish yellow, railroad worms emit red and fungi emit greeny bluish light (Patel 1997). Fungal Families Exhibiting Bioluminescence The phylum Fungi is composed of the following 5 divisions (Newton 1952): • Myxomycetes (slime molds) • Schizomycestes (bacteria) • Phycomycetes (moulds) • Ascomycetes ( yeasts, sac fungi and some molds) • Basidiomycetes (smuts, rusts, and mushrooms) Of the above divisions the majority of bioluminescence occurs in the Basidiomycetes and only one observation has been made involving the Ascomycetes; specifically in the Ascomycete genus Xylaria (Harvey 1952). At present there are 42 confirmed bioluminescent Basidiomycetes that occur world wide and share no resemblance to each other visually, other than the ability to be bioluminescent. Of these 42 species that have been confirmed 24 of these have been identified just in the past 20 years and as such many more species may exhibit this trait but are yet to be found. The two main genus that display bioluminescence are the genus Pleurotus which have at present 12 species which occur in continental Europe and Asia. The genus Mycena have 19 species identified to date with a world wide distribution range. In North America only 5 species of bioluminescent basiodiomycetes have been reported. These include the Honey mushroom -Armillaria mellea (illustrated in figure 3), the common Mycena -Mycena galericulata (illustrated in figure 1), the Jack O'Latern - Ophalalotus olearius (pictured in figure 4), Panus styticus and Clitocybe illudens. The question of whether bioluminescent mushrooms were all poisonous was raised in the discussions between my laboratory partner and myself. After examining the literature and a mushroom field guide book it was evident that there was no correlation between the edibility of the mushroom and its bioluminescence. Some mushrooms such as Armillaria mellea the Honey mushroom was listed as being excellent to eat. While the Jack O'Latern - Omphalalotus olearius was listed as poisonous and caused sever gastrointestinal cramps. The edible merits of the common Mycea were unknown and while Panus stypticus was listed as poisonous it was found to contain a clotting agent and useful in stopping bleeding (Lincoff 1981, Newton 1952 and Herring 1978). As it only a field guide to North American mushrooms was available, only the North American varieties were examined. If all 42 species of bioluminescent basidiomycetes were included in the search, a possible correlation may have been found. Bioluminescence Research Applications Luminescence has a unique advantages for scientific studies as it is the only biochemical process that has a visible indicator than can be measured. The light given off in the bioluminescent reaction is now able to be accurately measured with the use of a luminometer. This ability to easily and accurately detect small amounts of light has led to the use of the bioluminescent reaction in scientific research involving biological process applications. The following are just a few applications, some of which have been developed in only the last few years (Johnson and Yata 1966, and Patel 1997). The following are two examples of which have been recently developed. The Tuberculosis Test Testing for tuberculosis has long been a problem because of the long time it takes for the species to grow to a size that is detectable by modern medicine. Typically growing a culture of Mycobacterium tuberculosis large enough to determine the strain that a particular patient has can take up to three months. Of course, this poses a problem because the patient often can not wait for the diagnosis and must be given drugs that his strain may be resistant to. This is further complicated because there are 11 drugs used to combat TB, picking the right one before determining the strain has a 1/11 chance of success. Recently a way of incorporating bioluminescence into the TB tests has been found and can sharply reduce the diagnosis time to as little as 2 days. The technique involves inserting the gene that codes for luciferase into the genome of the TB bacterial culture taken from the patient. The gene is introduced through a viral vector and once incorporated, the bacteria produces the luciferase. When luciferin i s added to the culture, light is produced. Since less than 10,000 bacteria are needed to code for enough luciferase to produce a detectable amount of light, the culture time is reduced to only 2-3 days. Since the luciferase-luciferin reaction requires ATP, the resistance of the strain in the culture can be tested by adding a drug and watching for light. This will indicate which of the 11 drugs therapy's will be effective in treating Tuberculosis. By reducing the time needed to prescribe the correct drugs for treatment, this application of bioluminescence will someday be ready to save some of the 3 million killed each year by tuberculosis (Patel 1997). Biosensors Bioluminescence has also been used for several years as a biosensor of many substances. As seen in the tuberculosis example, bioluminescence can be used a sensor for the presence of ATP because ATP is needed in the light producing reaction. Other techniques have been used for detecting ions of mercury and aluminum, among others, by using bacteria with light genes fused to their ion-resistant regulons. For example, if a bacteria that is resistant to Hg is in the presence of Hg, the genes coding for its Hg resistance will be activated. The activation of that gene will also activate the luciferase gene fused to it, so the bacteria will produce luciferase whenever Hg is present. Adding luciferin and testing for light production with a luminometer reveals the presence of the metal ion in the solution. This technique is especially useful in testing for pollutants in the water supply when concentrations are too low to detect by conventional means(Herring 1978, and Patel 1997). Other areas that are currently using bioluminescence in scientific research include evolution, ecology, histology, physiology, biochemistry, biomedical applications, cytology and taxonomy. Any area that involves a living organism can utilize bioluminescent technology as a biosensor. Conclusion The glow light generated by bioluminescent Fungi has for centuries generated interest from philosophers and scientists and has benefited science by providing problems to solve -How does it work and does it have a practical application? The answers to those basic problems that have been discovered today and have resulted in benefiting mankind, by bettering our lives especially in regard to it's biomedical applications. Further research with bioluminescent Fungi is being conducted on a world wide scale and include North America, Japan, and Europe. Future research may lead to new discoveries and uses from bioluminescent organisms such as the Fungi group.

Bubonic Plague

The disease is called the Bubonic Plague. It is caused by the bacteria Bacillus. Also now known as the "Bubonic plague". It is a plague because of its widespread fatality throughout history. The cause of this disease is the Yersinia petis bacterium. The Bubonic plague is transmitted from fleas to humans. You can contract the disease either by being bitten by the oriental flea, Xenopsylla Cheopis, or be exposed to plague infected tissue. The "Bubonic Plague" has an incubation period of 2 to 6 days. Within a week the body's temperature rises to 104 degrees F. Shortly after they show signs of a fever other symptoms come about which are delirium, mental disorganization, shivering, vomiting, headache, giddiness, intolerance to light, and a white coating on your tongue. The symptoms become worse as the disease spread through the bloodstream and lymphatic system. The later symptoms, as you begin to experience the last stages of the disease, are your back starts to hurt and painful swelling of your lymph nodes. Hard lumps filled with blood and puss called "boboes",from which the disease gets it name, form on various parts of your lymphatic system, such as your neck, inner thigh, groin, and armpits. This stage is the most painful. Blood vessels break and later the dry blood turns black underneath your skin. The treatment for the plague is a vaccine that lasts 6 months. You can use the preferred vaccine Streptomycin, or gentamicin, teracyclines, or chloramphenicol are all good substitutes. The treatment must start within 15 hours of the first symptom of death is inevitable. Some special characteristics of this disease are you can be any age to contract it, it is most common is unsanitary condition, or where there are an abundance of rodents and if untreated death will occur within 3 days. The most amazing fact about this disease is that it has killed over 75 million people over the centuries.

Forever young

Reversing The Aging Process, Should We? In the length of time measured as human lifetime one can expect to see a full range of differing events. It is assumed that during a lifetime a person will experience every possible different emotion. If one is particularly lucky, he will bear witness to, or affect some momentous change in humanity. However is it reasonable to ask what would be experienced by someone who lived two lifetimes? Up until recently the previous question would and could only be rhetorical. There is no answer, because no one has ever lived that long. Of course that was up until now. At McGill University, nematodes (tiny organisms) have experienced five lifetimes (Kluger). Through complex scientific experiments nematodes and fruit flies have had their lifespans increased not by fractions of life times, but by multiples of lifetimes (Kruger). Mankind is using the discovery of DNA as an opportunity to play G-d by changing the aging process. Man has a natural tendency to play the role of G-d. Man has a an inherent need to affect others, be it through the vises of war, power, manipulation or politics. However man's natural tendency to play G-d has reached it's final manifestation. By attempting to slow down the aging process man is using himself as the ultimate canvas, to play the role of the omnipotent. Research into the process of aging began in 1961(Rose, Technology Review:64). Since then a great deal of time, money and effort have been appropriated into discovering the causes of aging, it can therefore be inferred that humanity has an almost "personal" interest in aging. Of course the culmination of discovering how we age, is discovering how to stop it. An intrinsic characteristic of Man is His obsession with superficiality. Superficiality is equated with appearance. The appearance of beauty can be equated with youth. Therein lies man's obsession with age, ceasing to age means being eternally beautiful. As usual man's actions are dominated by ego and self-preservation. Within the confines of youth there lies a certain fountain of power. Power which cannot be accessed once one ages. Things like physical and sexual prowess. The time of youth is often refereed to as the "prime of your life". It is therefore not difficult to understand and conceive of man's motivation to stay young and to wish that the immedia te people surrounding him stay young. If a mathematician wished to create a formula to describe the life of one man he would say that life is equal to a series of interchangeably quantized, experiences and emotions. With the advent of a retarded aging process, that which we know as life changes. While life is composed if those quantized properties there are a finite amount of them, therefore decelerating the aging process has major implications. First and foremost among them is what to do with all that extra time? In 1900 the average life expectancy of a baby born in the United States was 47 years. Conservative estimates place life expectancy of children born today in the united sates at 76, while less conservative estimates place the life expectancy at 100 years. Presently man is unable to cope with this extra time. Many septuagenarians spend days sitting around doing next to nothing. The term "waiting to die" has been applied in reference to such activities, or rather lack thereof. Even while the average life-span has increased, whose to say tha t the time added is quality time? Another general comment overheard in the population at large was "what's the point of growing old and having to suffer through ulcers, cataracts, hemorrhoids, and cancer. Isn't it better to die young and healthy then to die old, infirm and brittle?" The essential question being proposed is one of quality versus quantity. Is it better to live for a long time with much of that time spent in dialysis, or is it preferable to enjoy a short but "fun" life. Even if the scientists can cure humanity of the ailments of the elders, there still remains the question of how to manage one's time. "We're bored" has often been used as the battle cry of youth, people who haven't even lived two decades. What are people who have lived twelve decades supposed to do? These questions are stuck in the realm of rhetoric. There are no answers to these questions. It is altogether possible that there never will be. Scientists involved in the dissection of the aging process have made what they believe to be an important discovery (Gebhart,174). Scientists discovered a small area at the tip of the chromosomes that served no apparent purpose (Kluger). Dubbed a telomere, this area of the chromosome wasn't responsible for any physiological traits. What was discerned however was that whenever a cell divides to create two new cells each of the daughter cells has less telomere than the mother cell (Kluger). Once the cell has undergone a maximum number of divisions the telomere was reduced to a stub, exposing genes which initiated proteins that caused the deterioration of the cell (Kluger). The most applicable analogy would be that of a bomb. The telomere acts as the fuse to the bomb. The fuse is lit from the time of birth, and when the telomere\fuse runs out the bomb goes off. Only in this case instead of instantaneous death, the victim succumbs to the equivalent of radiation poisoning. The victims condition is terminal from the start and slowly degrades to the point of death . The conclusion is that life is just a case of terminal death. Or is it? Scientists also discovered an enzyme known as telomerase prevents the loss of telomere, essentially stomping the fire out (Rose, Technology Review: 64). There are many substantial and immediate implications raised by this. What are the ethics of immortality? Was humanity meant to be immortal? Are there benefits to being immortal? Are there consequences? While it seems like quite a neat thing to do immortality would place an incredible strain on our resources. Not only on social actions and mental coping but also on the resources of this planet. There are a limited quantity of resources available for consumption on this planet. As a result of human immortality, the first consequence would be overcrowding. No one ever dies, therefore there's no room to go "out with the old and in with the new". The next major problem would be a food shortage. With an ever-increasing population and a constant food supply, there wouldn't be enough food to feed everybody. Either the vast majority of the planet would be starving while a few noble class people feasted, or in general people would have to reduce the amount they eat. Which introduces the problem of waste disposal. Not only human and animal defecation but garbage, where would it go? A common complaint from a number of people, and most teenagers is that there parents place too much pressure on them, and that they're always trying to find out things that are none of there business. Well imagine the pressure placed on someone who has not only his parents, not only his grandparents, but also his great-grandparents, his great-great-grandparents, their parents, and their parents. A person would have an endless supply of ancestors, and would be constantly overseen. These are huge ramifications that would change the way humanity not only acts but also the way humanity perceives itself. Lastly there is the ethical aspect of increasing humanity's lifespan. Regardless of whether there is or is not a some omnipotent watchperson whom we in our rather limited capacity perceive as G-d there are ethical issues which must be dealt with. Humanity has always perceived itself as more than just the sum of its parts. However that isn't to say that if you change one of the parts humanity will stay the same. There is nothing more immediate than DNA to a human. What right does humanity have to go stumbling around down there. A baby doesn't change its own diapers does it? If humans were meant to live for a certain amount of time who are we to say we should live longer. On the other hand who's to say we shouldn't. Yes the human lifespan has been adjusted in the past, but those were all external stimuli, war, famine, disease and the CIA were all responsible for changing the definition of a lifetime. However adjusting DNA is an internal change. Changing our society and hygiene is light years away from control ling microscopic chemical reactions. Man is referred to as G-d's ultimate creation, the universe his canvas. But what happens when humans steal the canvas and decide to redecorate, would you want to recolor your Picasso? Is there any justification for living that long, does there need to be? These are not easy questions, and there not intended to be, but should scientists prove successful in their endeavors, all of these questions will have to be resolved. How can certain establishments which frown on cosmetic plastic surgery frown on the reorganization of protein strands? There is no doubt that the people in charge of those organizations would take advantage of these technologies (Rose, Melatonin,: 6). How are the two things different? There are no possible answers to these questions for now they must remain rhetorical. It is increasingly obvious that the repercussions of these technologies stretch across the board. As always the horizon of the future stretches before us, only revealing a glimpse of that which is to come. The resounding questions that will soon confront us can only be concluded with the passage of time, something apparently humanity will have a lot of.

Flourescence InSitu Hybridisation and its advantages

Flourescence in-situ hybridisation is a great advancement in technology because there are fewer chances of a miscarriage, the parents receive faster results, and the tests are easier to do. In the future, FISH will be able to decrease the chances of a miscarriage by using samples of maternal blood instead of amniotic fluid. The problem with amniocentesis is it uses a hollow needle to take fluid from the mother's uterus. The needle could damage the developing fetus if not inserted properly. Another advantage of FISH is that the parents get a much quicker test result than amniocentesis. After the sample is taken, amniocentesis can take up to three weeks before a test can be administered. With FISH, a same day result is given, which is much more convenient to the parents. Additionally, FISH is a simpler process. It uses specially prepared molecules which bind to specific regions of DNA. To find a particular gene, the examiner just looks for the flourescent coloured molecule that bonds to that specific gene. In amniocentesis, test cells are cultured for three weeks and then tested. The chromosomes are then counted manually, and compared to a chart of normal chromosomes. This can be difficult, as the tester is looking for an extra chromosome 21. So because the test is much simpler, quicker, and reduces the risks of miscarriages, flourescence in-situ hybridisation is an incredible discovery in the field of genetics.

Design of a Psychological Experiment

Experiment Problem: Suppose you are a psychologist who is interested in the effects of caffeine on the eye-hand coordination of students enrolled at UMCP. Design an experiment to test the hypothesis that caffeine enhances a student's ability to hit a baseball. Describe your experiment by answering the following questions: 1) What are the independent and dependent variables? The independent variable would be the caffeine. The results of the students' hitting of the baseball would be the dependent variable. 2) What are the experimental conditions and what are the tasks for the experimenter, the participants in your experiment, and any other people you might ask to help? The experimental conditions would be the same for all participants, probably in an indoor stadium so the weather won't affect the students. The task for the experimenter would be to make sure to have a control group, to have a wide variety and different types of participants, to make sure all participants use the same equipment, and have controlled amounts of caffeine. The tasks for the participants would be to carefully follow the instructions of the experimenter, that is to hit the baseball. 3) Will you treat all the participants in the same way? No, I would not treat all the participants in the same way. The control group would not be given caffeine. However, I would treat all experimental groups the same because that will give more accurate results. If the participants were not treated the same I would not be able to accurately measure how much or how little the caffeine affected the students. 4) How will you select the participants of your study so that they are representative of the students enrolled at UMCP? I would randomly chose participants of different ethnic groups, ages, weights, and sexes. 5) What factors must be controlled when using the experimental method in this manner? The factors that must be controlled in this experiment would be the amount of caffeine consumed, the equipment used (must have same bat and baseball), and the environment in which they will perform their assigned task. The environment should be indoors so that weather will not affect the results. 6) Suppose your experiment provided evidence that caffeine enhances eye-hand coordination. Would it be reasonable to expect, based on your results, that a pilot would be better able to land an airplane if given caffeine? No, since landing a plane and hitting a baseball are two very different skills. Landing a plane requires more skill and the side effects of caffeine which are not evident in the above experiment might show up in a pilot. Caffeine may cause some people to become nervous and shake and that would not help a pilot land a plane. The only way to find out would be to setup and experiment about the effects of caffeine on pilot landing planes.

Cystic Fibrosis

CYSTIC FIBROSIS ONE OUT OF EVERY 2,500 BIRTHS IN THE UNITED STATES WILL BE DIAGNOSED WITH CYSTIC FIBROSIS. THIS FACT MAKES CYSTIC FIBROSIS ONE OF THE MOST COMMON GENETIC DISEASES IN THE NATION. ABOUT 30,000 AMERICANS HAVE THE DISEASE, BUT EVEN THOUGH CYSTIC FIBROSIS IS THE NATIONS MOST COMMON GENETIC DISEASE THE MAJORITY OF AMERICANS KNOW LITTLE ABOUT IT. CYSTIC FIBROSIS IS RELATIVELY COMMON IN CALCASTION PEOPLE BUT RARE IN AFRICAN-AMERICAN. THE DISEASE IS VERY UNCOMMON IN MONGOLIANS. FIVE PERCENT OF THE POPULATION IN THE UNITED STATES ARE CARRIERS OF THE GENETIC DISEASE. CYSTIC FIBROSIS, SOMETIMES CLASSIFIED AS MUCOVISCIDOSIS, IS A DISORDER IN WHICH THE EXCRORINE GLANDS SECRETE ABNORMALLY THICK MUCUS. THIS LEADS TO THE OBSTRUCTION OF THE PANCREAS AND CHRONIC INFECTIONS OF THE LUNGS, WHICH GENERALLY CAUSES DEATH IN CHILDHOOD OR EARLY ADULTHOOD. SOME MILDLY AFFECTED PATIENTS MAY SURVIVE LONGER. PATIENTS WITH PANCREATIC INSUFFICIENCY TAKE PANCREATIC ENZYMES WITH MEALS. THOSE WITH RESPIRATORY INFECTIONS ARE TREATED WITH ANTIBIOTICS, MOSTLY WITH AEROSOLS THAT RELIEVE CONSTRICTION OF THE AIRWAYS. PHYSICAL THERAPY IS USED TO HELP PATIENTS COUGH UP THE OBSTRUCTING MUCUS. INTESTINAL OBSTRUCTION, WHICH OCCURS MOSTLY IN INFANCY, MAY REQUIRE SURGERY. IN 1989, RESEARCHERS FOND THE ABNORMAL GENE THAT CAUSES CYSTIC FIBROSIS. THIS GENE IS LOCATED ON CHROMOSOME 7 . A PERSON WHO HAS TWO CYSTIC FIBROSIS GENES HAS THE DISEASE . A PERSON THAT CARRIES ONE OF THE GENES DOES NOT HAVE THE GENETIC DISEASE, BUT IS A CARRIER. THE SYMPTOMS OF CYSTIC FIBROSIS SOMETIMES OCCUR IMMEDIATELY AFTER BIRTH. MUCUS SECRETIONS MAY APPEAR IN THE BABY'S INTESTINES, WHICH CAN CAUSE OBSTRUCTION IN THE INTESTINES. IN ALL CASES, THE CHILD WILL GAIN LITTLE WEIGHT RIGHT FROM BIRTH, BECAUSE THE PANCREAS IS NOT PRODUCING ENZYMES. LITTLE TO NO NUTRIENTS ARE ABSORBED IN THE CHILD'S SYSTEM. A CHILD WITH CYSTIC FIBROSIS MAY HAVE REOCCURRING RESPIRATORY INFECTIONS, ALONG WITH COUGH AND FEVER. THIS MAY BE MORE SEVERE AND PERSISTENT THAT NORMAL THIS IS A RESULT OF THE THICK, STICKY MUCUS THAT WILL HOLD AND TRAP GERMS IN THE BRONCHIAL TUBES. IT SHOULD BE TAKEN IN TO CONSIDERATION THAT CHILDREN WITH CYSTIC FIBROSIS HAVE LARGE APPETITES AND EAT A GREAT DEAL. IN SPITE OF THEIR MALNUTRITION, THEY ART NOT IN PAIN AND DO NOT GENERALLY FEEL IT. EXTRACTS OF ANIMAL PANCREAS, IN POWDER OR GRANULE FORM, ARE PRESCRIBED TO REPLACE THE MISSING ENZYMES FROM THE PANCREAS, AND THE AMOUNT OF FAT IS DECREASED IN THE CHILD'S DIET. WITH THIS TREATMENT THE CHILD BEGINS TO GAIN WEIGHT. TO KEEP THE LUNGS FREE OF AS MUCH MUCUS AS POSSIBLE , THE PATIENTS MAY NEED TO HAVE DAILY RESPIRATORY PHYSICAL THERAPY. ANY RESPIRATORY INFECTION THAT ARISE ARE TREATED WITH LARGE AMOUNTS OF ANTIBIOTICS. CYSTIC FIBROSIS CAN NOT YET BE CURED. ALTHOUGH THE IDENTIFICATION OF CHROMOSOME 7 HAS PAVED THE WAY FOR GENE THERAPY. ANTIBIOTICS AND ENZYMES ARE NOT THE ONLY TREATMENTS FOR CYSTIC FIBROSIS. ONE RELATIVELY NEW TREATMENT IS A BIOTECH DRUG THAT THINS THE MUCUS, WHICH HELPS THE LUNGS FUNCTION BETTER AND REDUCES THE RISK OF INFECTIONS. GENE THERAPY IS STILL IN EXPERIMENTAL STAGES.

Fern Life Cycle

Introduction: This essay will discuss the fern life cycle as taught in biology lab. The essay will cover the basic process which we used to grow a fern. I will discuss the methods and the results of the lab exercise. Finally, I will discuss the evidence of the methods and results that were obtained . Methods and Results: To begin our experiment we obtained a petri dish from our lab instructor which contained fern spores and the food they needed to survive. We then look at the spores through the micro scope. It was to soon to see anything but little green dots. We then put our petri dishes under a light until next week. When we came in next week we observed our fern spores through the dissecting microscope. We looked to see if we could find anything germinating. We quickly noticed something that appeared like an air bubble squirting out something green. This was our fern spore which was germinating. Next, we removed a few of the germinating spores from the petri dish and put them under a compound microscope scope. We found the spore wall and observed how the developing gametophyte had broken through the wall, as instructed by our lab manuals. One could also identify the chloroplasts with in the cell. We then put up our dishes for another week. The third week of our fern lab we identified the difference between male and female gametophytes. We did this by taking a culture from our petri dish and placing it under a dissecting microscope. Due to the male and female being both located on the same prothallus it was necessary to obtain the exact location of the antherium and the archegonium from the lab book or the instructor. Once this was done it was fairly easy to tell the difference between the male gametophyte or (antheridium) and female gametophyte (archegonium) on the prothallus. The antheridium was located around the perimeter of the prothallus, near the rhizoids. The antheridium was located near the growing notch on the under side of the prothallus. To me the growing notch seem to like red dots set up like bowling pins. We also observed sperm swimming around the archegonium. We then put our fern lab petri dishes back under the light until next week. By the forth week of our fern lab experiment our gametophytes had grown quite a bit. We briefly looked at them under a compound microscope, but there was no valuable information learned from this. The gametophytes would be large enough in the next couple of weeks to transplant them into three liter soda bottles to grow into full size fern plant. This would complete our fern life cycle experiment. Discussion: In this section I will talk a little about what I learned from the fern life cycle from first germination to final result, a full grown fern plant. I will begin by saying that I had to learn a lot of specific terms to be able to follow the experiment. It is imperative to understand the basics get a handle on the whole. Anyway, I will start from the beginning. I learned that their were several different stages in which a fern had to go through in order to grow into an adult plant. I will describe the fern life cycle as learned in biology lab and the lab manual. First the fern was given to us as a gametophyte. The gametophyte contains an antheridium, which is the male sex organ that produces the sperm, and the archegonim, the female sex organ were fertilization takes place. This allows the fern gametphyte to fertilize itself. Once this happens the gametophyte will give rise to a sporophyte. Then the sporophyte will produce more spores and the spores will produce more gametophytes, thus completing the cycle of life once again. I learned a lot by watching the experiments through a microscope. The hands on experience really help to understand what was going on in the gametophyte. When one could actually see the archegonium and the anteridium on the prothallus it seem to help make sense of the lab experiment. One could even see the sperm going to the aechegonium, which lead to fertilization. I can remember looking into the microscope and seeing the green ooze squeezing out of the cell wall. In conclusion, all of this combined lead me to believe the fern life cycle did indeed happen as the lab book and instructor had taught. The experience of studying the fern life cycle did spark my curiosity in the development of life from cells. It really amazed to see an adult fern grow from something I had to look at through a microscope.

How nutrients get in and wastes get out

Science 10 Assignment -- Part B How Nutrients get in, and wastes out. In a human being, nutrients are necessary for survival. But how are these nutrients obtained? This report will go into depth on how the food we eat gets into our cells, and how the waste products that we produce get out of the body. Also, the unicellular organism Paramecium will be compared with a human being, in terms of all of the above factors. Dietary Nutrients The chief nutrients in a diet are classified chemically in four groups: carbohydrates, proteins, vitamins (Which do not require digestion) and fats. Carbohydrates in the diet occour mainly in the form of starches. These are converted by the digestive process to glucose, one of the main nutrients needed for cellular respiration to occour. Starch is a large molecule, a polymer of glucose. Dextrin and maltose are intermediate products in the digestion of starch. Some foods contain carbohydrates in the form of sugars. These are the simple sugars, such as sucrose (cane sugar) or lactose (milk sugar), that must be processed into smaller units. Occasionally, the simplest form of sugar, a monosaccharide such as glucose, is present in food. These monosaccharides do not require digestion. Proteins are polymers composed of one or more amino acids. When they are digested, they produce free amino acids and ammonia. Vitamins are a vital part of our food that are absorbed through the small intestine. There are two different types of vitamins, water-soluble (All the B vitamins, and vitamin C) and fat-soluble (vitamins A, D and K). Neutral fats, or triglycerides, are the principal form of dietary fat. They are simple compounds, and within digestion are broken down into glycerol and fatty acids, their component parts. Ingestion Intake of food in the Paramecium is controlled by the needs of the cell. When food is sensed, the organism guides itself towards the food, and guides it into the oral groove, then enclosing it in a vacuole. Enzymes are then secreted to digest the food, which is then absorbed into the cytoplasm and made available to the various organelles. But, a Paramecium has to be able to move to its food source, while a human cell has his food brought to it through the circulatory system. In man, a much more complicated system exists than that of a unicellular organism, for the size of the animal and the fact that all of the cells within the animal must be able to absorb food and get rid of wastes, just like the Paramecium does. Digestion in the Mouth Upon entering the mouth, the food is mixed by mastication with saliva, which starts the digestive process by making contact with the food particles with the salivary enzyme ptyalin, dissolving some of the more soluble matter within the food. It also coats the food mass with mucin, to aid in swallowing. The chemical phase of digestion in the mouth begins when the salivary amylase, ptyalin, attacks the cooked starch or dextrin, converting some of this starch into dextrin, and some of the dextrin into maltose. The salivary glands can be activated when food is thought of, while the actual presence of food will produce a continuous flow. Since food remains in the mouth for a very short period, very little of the digestive process actually occours in the mouth. Following digestion in the mouth, the semisolid food mass is passed by peristaltic movements of the esophagus, a long muscular tube that connects the mouth to the stomach. The food then reaches the esophageal sphincter, a ring of muscle at the upper end of the stomach. This sphincter then opens to let the food into the stomach. Digestion in the Stomach Here, salivary digestion continues until the acid of the gastric juice penetrates the food mass, and destroys the salivary amylase. The food mass is then saturated with gastric juice, and the gastric phase of digestion is initiated. The gastric phase of digestion is chiefly proteolytic, or protein-splitting. Within this process, the gastric glands secrete the enzymes pepsin and rennin. These enzymes, aided by gastric acid, converts a fairly large amount of the proteins to smaller forms, such as metaproteins, proteoses and peptones. There also may be a small amount of fat digestion in the stomach, since a small amount of lipase is present in gastric juice. This enzyme causes hydrolysis of the triglycerides into glycerol and fatty acids. The digestive action of these enzymes, combined with the action of the gastric juice results in the solution of most of the food material. In the final stages of gastric digestion, the fluid mass, propelled by peristaltic movements, passes into the small intestine through the pyloric sphincter. Here, the chemical phase of digestion is initiated. Digestion in the Small Intestine The fluid product of gastric digestion mixes with the intestinal secretion, and two other fluids, namely the pancreatic juice (produced by the pancreas) and the bile (produced by the liver). Both of these fluids are secreted near the pyloric valve, which separates the stomach from the intestine. These secretions neutralize the acidic gastric juice, causing the gastric digestion phase to end. The enzymes within the pancreatic juice, and those of the intestinal juice start the final digestion phase. The pancreatic juice contains powerful amylase, protease, and lipase, that attack the starch, protein and fat that escapes the actions of the salivary and gastric phases of digestion. The intestinal secretion contains enzymes that attack the intermediate products of proteolytic and amylolytic digestion, as well as some smaller food molecules. The pancreatic amylase converts both the raw starch and the cooked starch that was not digested by the two previous phases. Cooked starch is converted to dextrin, and the dextrin to maltose. The pancreatic lipase hydrolyzes the neutral fat to glycerol and fatty acids. The bile has an important role here, as it, along with the alkali content in the secretions, emulsifies the fat, producing many fat surfaces on which the lipase can act. The pancreatic proteases convert any remaining protein to proteoses and peptones. These intermediate products are then attacked by enzymes known as erepsins, and converted slowly into their individual amino acids. The intestinal enzymes, maltase, sucrase, and lactase hydrolyze their respective disaccharides (maltose, sucrose and lactose) into their component monosaccharide units, and finally into glucose. After all of these processes, carbohydrates have been broken down into glucose, proteins have been broken down into amino acids, and fats hydrolyzed into fatty acids and glycerol. These nutrients are absorbed by the villi, finger-like microscopic projections that line the inside of the small intestine. The sugars and amino acids take a direct route, and pass into the capillaries of the villi, taking them directly into the bloodstream. Glycerol and fatty acids, however, are first resynthesized into triglycerides, they then enter the lymphatic system and then into the bloodstream. Digestion in the Large Intestine The last part of the digestive system, the large intestine is where all of the wastes enter. It holds the wastes and reabsorbs some of the remaining undigested material. The first part of the intestine is mainly responsible for reabsorbing. The materials reabsorbed are water, bacterial vitamins, and sodium and chloride ions. Within the last half of the intestine, wastes are stored. These wastes are made up of undigested food, and dead bacteria. The wastes then become feces, and are released through the anus. The food is moved down the small and large intestine by peristalsis, much like how food moves down the esophagus. Circulatory System After the food molecules within the villi diffuse into the bloodstream, the blood carries the nutrients into the liver. There, the sugar is removed from the blood and stored for later use as glycogen. After the liver, the blood travels to the main provider of motive force, the heart. It is then pumped out through the arteries into the body. The blood vessels become smaller and narrower until they reach their 'target' tissue. The blood is now within the smallest vessels called capillaries. The capillary walls are only one cell think, enabling diffusion of the nutrients carried in the bloodstream into the individual cells, and diffusion of waste products back into the bloodstream from the cells. At this level, the systems regulating and governing the maintenance of homeostasis are similar in both man and the Paramecium. Absorption and excretion are basically governed by the concentration of fluids inside the cell, as compared with the fluid concentration outside the cell. Excretion When the blood takes the nutrients to the cells, it receives cellular waste products as well, such as carbon dioxide, urea, and surpluses of other chemicals, such as glucose. From the cells, the blood (with the waste products) goes to the kidneys. It enters the kidney through the renal artery, and branches out into many capillaries. Here, there is a slowdown of circulation. as a result of this, pressure increases, and much of the plasma is forced out of the blood. Renal tubules (nephrons) number about one million in each kidney. There tubules are responsible for the production of the fluid that is eventually eliminated as urine. They filter out many of the chemicals, particularly urea (which is poisonous) and nitrates which are the by-products of protein digestion. This process is called pressure filtration. As the fluid moves down the tubule, many of the nutrients that escaped the cell such as sodium ions and glucose are reabsorbed so that the body can use them, and will not become short of these sub stances. The fluid is now urine, and collects in a hollow region of the kidney. From the kidney, the urine enters the urinary bladder, a storage container for the urine. When this bag fills, a sphincter opens to the urethra, and the urine is let out of the body from an external opening. Excretion also takes place in the lungs when a person breathes out, and also though sweat. But, these parts of the excretory system are not controlled as well as the kidney, and can lead to loss of salt. Nervous System The nervous system controls a large part of the activity of the digestive and excretory systems. The control is exercised through the autonomic nervous system, of which there are two parts. The first part, controlling increase in activity, is called the sympathetic system. And second, controlling decrease in the level of activity is the parasympathetic system. Both systems are unconscious, only chewing, swallowing and the anal and uretheral sphincters are under conscious control. Endocrine System The endocrine system deals with hormones, which regulate the metabolic rates of cells and organs. They are much like nerves, but target only certain parts of the body. They are essential to maintain homeostasis. The gastrin hormone is found in the stomach, and controls the amount of gastric juice produced. They also regulate excretions such as saliva. The hormones controlling the digestive and excretory systems are located some distance away from the cells that they have to control, therefore some method of transport must be utilized. This method is the bloodstream. The hormonal glands secrete their hormones into the bloodstream. These hormones then travel to the target organ or cell, and regulate the activity of that organ or cell. This system is slower to respond than the nervous system.

How changes in the atmosphere eukarotes and multicellularit

About 2.5 billion years ago, oxygen began slowly to accumulate in the atmosphere, as a result of the photosynthetic activity of the cyanobacteria. Those prokaryotes that were able to use oxygen in ATP production gained a strong advantage, and so they began to prosper and increase. Some of these cells may have evolved into modern forms of aerobic bacteria. Other cells may have become symbionts with larger cells and evolved into mitochondria. As the amount of oxygen and other atmospheric gasses increased, they started blocking out deadly u.v. rays from the sun. The sun's rays made life outside of water nearly impossible. These changes made life on land possible and evolution occurred as prokaryotes gave rise to land living eukaryotes. The microfossil record indicates that the first eukaryotes evolved at least 1.5 billion years ago. Eukaryotes are distinguished from prokaryotes by their larger size, the separation of nucleus from cytoplasm by a nuclear envelope, the association of DNA with histone proteins and its organization into a number off distinct chromosomes, and complex organelles, among which are chloroplasts and mitochondria. Scientists believe that eukaryotic organisms such as the protists evolved from the prokaryotes. There are two main theories which describe how this transition may have occurred. The first is the endosymbiotic theory, or enosymbiosis, and the other is the autogenous theory, or autogenisis. These two theories are not mutually exclusive, meaning one or the other could account for different parts of eukaryotic cells. The endosymbiotic theory states that the formation of eukaryotic cells were symbiotic associations of prokaryotic cells living inside larger prokaryotes. The endosymbiotic hypothesis accou nts for the presence in eukaryotic cells of complex organelles not found in the far simpler prokaryotes. Many modern organisms contain intracellular symbiotic bacteria, cyanobacteria, or photosynthetic protists, indicating that such associations are not difficult to establish and maintain. Endosymbiosis is said to be responsible for the presence of chloroplasts and mitochondria in eukaryotes. Autogenisis, the alternative to the endosymbiotic theory is specialization of internal membranes derived originally from the plasma membrane of a prokaryote. Autogenisis could be responsible for structures like the nuclear membrane and endoplasmic reticulum in eukaryotes. There are two scenarios for which multicellularity may have occurred. The first is unicellular organisms came together to form a colonial organism, then some tissue developed specialized functions and the cells became differentiated, forming a multicellular organism. The other scenario starts with a coencytic organism forming cellulorization with individual cells developing membranes, then tissues became more specialized forming a multicellular organism. There are some advantages of multicellularity such as having specialization of cells which creates a division of labor, leading to greater efficiency. Another advantage is multicellular organisms have a larger size which provides protection from predators. Fungi are large and have a large surface area to volume ratio, allowing them to absorb nutrients more efficiently.

Hammerhead Sharks

Sharks are one of the most feared sea animals. They live in oceans across the world but are most common in tropical waters. There are over three hundred fifty species of sharks. They can be broadly categorized into the following four groups: Squalomorphii, Squatinomorphii, Batoidea, and Galeomorphii. The shark family Sphyrnidae that includes the Hammerheads are part of the Galeomorphic classification. They are probably the most easily recognizable of all the sharks. The Hammerheads are among the strangest looking sharks. As the name indicates they have a flattened head which resembles the head of a hammer. Their eyes and nostrils are at the ends of the hammer. There are many species of Hammerheads. There are eight living species of hammerheads. The following four are the main categories: 1. Scalloped hammerhead (Sphyrna lewini)-Pectoral fins are tipped with black this grey shark. The maximum length is about 12 feet. 2. Bonnethead (Spyrna tiburo)-With a head shaped like a shovel the bonnethead rarely grows more than four feet long. This shark is commonly seen inshore. 3. Smooth hammerhead (Sphyrna zygaena)-Bronze with dusky fin tips, it can grow to thirteen feet. 4. Great hammerhead (Sphyrna mokarran)-Attaining a length of a possible 18 feet, this is the largest and most dangerous of all the hammerheads. One of the most interesting things about the hammerheads is the unique shape of their heads. Ever since scientists started to study the hammerhead they have speculated about the use of the hammer. The hammer is a complex structure and probably serves more than one function. The most important function of the hammer according to scientists is increased electroreceptive area and it's sensory perception. This means that the hammerhead has a remarkable sensory ability to detect the small electrical auras surrounding all living creatures. Under certain conditions, such as in searching for wounded animals, the electrical activity increases helping the hammerhead to feed. It is also believed that the hammerhead may be able to use the Earth's magnetic field as a source for navigation. Some hammerheads migrate a lot and may rely on this built in compass sense to guide them in the open ocean. Another use for the hammer is to enhance maneuverability. The hammer's similarity to a hydrofoil seems to explain its u sefulness for maneuverability and improved lift. However, this theory has not been tested. Sharks generally have a small brain in comparison to their body weight. Among sharks hammerheads have a relatively large brain-body weight ratio. Sharks differ form most other fish in several ways. Sharks have a boneless skeleton made of cartilage that is a tough elastic substance. Most sharks have a rounded body shaped like a torpedo. This shape helps them swim efficiently. Hammerheads are especially good swimmers because of the hydrodynamic function of their head. All sharks are carnivorous. Most eat live fish, including other sharks. Most sharks eat their prey whole, or tear off large chunks of flesh at a time. They also eat dying animals. Hammerheads have definite food preferences. Their elongated head may help them locate the prey they prefer. The Great Hammerhead likes to eat stingrays. This was observed when the stomach contents of a hammerhead were examined and stingray spines were found. Stingrays are usually difficult to detect because they are partially buried in the sediment. Yet, the hammerhead is capable of finding them because they can swim close to the bottom swinging their heads in a wide arc like a metal detector. Sharks reproduce internally. Unlike most fish sharks eggs are fertilized internally. The male shark has two organs called claspers which release sperm into the female where it fertilizes the egg. In many sharks the eggs hatch inside the female, and the pups are born alive. Other species of sharks lay their eggs outside. The hammerhead female has an internal pregnancy in which a placenta is formed around the embryo. The gestation period for most placental sharks is between nine and twelve months. The placenta appears about two to three months after ovulation when the embryos have consumed their yolk. Eggs are ovulated at intervals of a day or so, which explains why their may be considerable variations in the developmental ages of pups in a litter. It's not unusual to find embryos that have died during development. Hammerhead sharks tend to form schools of fifty to two hundred. They tend to congregate and swim at special sea mounts. Sea mounts are underwater mountains. In these sea mounts there are many other fish attracted by rich algae and invertebrate larvae. The hammerheads have no interest in these fish. So why do they gather at these underwater mountains? Recent research seems to indicate that hammerheads go there for mating purposes. Observations in these sea mounts show that the majority of hammerheads there are female. This indicates that its easy for the male to find a mate. However, researchers were surprised to find that there were many immature female hammerheads at the sea mounts. This led them to believe that in addition to reproduction there must be other reasons for coming to the sea mounts. It is believed that the sea mounts serve as navigational centers. Each evening the hammerheads begin a ten to fifteen mile swim away from the mount, always returning by dawn or the following day. It seems that they spend the night at distant deep water feeding grounds. The young females participate in these long distance swims. The sea mount serves as a navigational center helping them find their way back. The nightly swim help the young find nutritious food which helps them in their growth.

Greenhouse Effect

The greenhouse effect, in environmental science, is a popular term for the effect that certain variable constituents of the Earth's lower atmosphere have on surface temperatures. These gases--water vapor (H2O), carbon dioxide (CO2), and methane (CH4)--keep ground temperatures at a global average of about 15 degrees C (60 degrees F). Without them the average would be below the freezing point of H20. The gases have this effect because as incoming solar radiation strikes the surface, the surface gives off infrared radiation, or heat, that the gases trap and keep near ground level. The effect is comparable to the way in which a greenhouse traps heat, hence the term. Environmental scientists are concerned that changes in the variable contents of the atmosphere (particularly changes caused by human activities) could cause the Earth's surface to warm up to a dangerous degree. Even a limited rise in average surface temperature might lead to at least partial melting of the polar ice caps and hence a major rise in sea level, along with other severe environmental agitation. An example of a runaway greenhouse effect is Earth's near-twin planetary neighbor Venus. Because of Venus's thick CO2 atmosphere, the planet's cloud-covered surface is hot enough to melt lead. Water vapor is an important "greenhouse" gas. It is a major reason why humid regions experience less cooling at night than do dry regions. However, variations in the atmosphere's CO2 content are what have played a major role in past climatic changes. In recent decades there has been a global increase in atmospheric CO2, largely as a result of the burning of fossil fuels. If the many other determinants of the Earth's present global climate remain more or less constant, the CO2 increase should raise the average temperature at the Earth's surface. As the atmosphere warmed, the amount of H2O would probably also increase, because warm air can contain more H2O than can cooler air. This process might go on indefinitely. On the other hand, reverse processes could develop such as increased cloud cover and increased absorption of CO2 by phytoplankton in the ocean. These would act as natural feedbacks, lowering temperatures. In fact, a great deal remains unknown about the cycling of carbon through the environment, and in particular about the role of oceans in this atmospheric carbon cycle. Many further uncertainties exist in greenhouse-effect studies because the temperature records being used tend to represent the warmer urban areas rather than the global environment. Beyond that, the effects of CH4, natural trace gases, and industrial pollutants--indeed, the complex interactions of all of these climate controls working together--are only beginning to be understood by workers in the environmental sciences. Despite such uncertainties, numerous scientists have maintained that the rise in global temperatures in the 1980s and early 1990s is a result of the greenhouse effect. A report issued in 1990 by the Intergovernmental Panel on Climate Change (IPCC), prepared by 170 scientists worldwide, further warned that the effect could continue to increase markedly. Most major Western industrial nations have pledged to stabilize or reduce their CO2 emissions during the 1990s. The U.S. pledge thus far concerns only chlorofluorocarbons (CFCs). CFCs attack the ozone layer and contribute thereby to the greenhouse effect, because the ozone layer protects the growth of ocean phytoplankton. would probably also increase, because warm air can contain more water than can cooler air. This process might go on indefinitely. On the other hand, reverse processes could develop such as increased cloud cover and increased absorption of CO2 by phytoplankton in the ocean. These would act as natural feedbacks, lowering temperatures.

Gregor Johann Mendel

Gregor Johann Mendel Gregor Mendel was one of the first people in the history of science to discover genetics. He independently discovered his work and lived in Brunn, Czechoslovakia. In Brunn he was a monk and later the Abbot of the church in Brunn. While he was in Brunn he performed many experiments with garden peas. With the information he observed he wrote a paper where he described the patterns of inheritance in terms of seven pairs of contrasting traits that appeared in different pea-plant varieties. All of the experiments he performed utilized the pea-plant, which in this case is the basis of the experiment. Mendels work was reported at a meeting of the Brunn Society for the Study of Natural Science in 1865, and was published the following year. Mendels paper presented a completely new and unique documented theory of inheritances, but it did not lead immediately to a cataclysm of genetic research. The scientists who read his papers of complex theories, dismissed it because it could be explained in such a simple model. He was rediscovered by Hugo de Vries in The Netherlands, Carl Correns in Germany, and Evich Tschermak in Austria all at the same time after 1900. They named the units Mendel described "genes." When the gene has a slighty different base sequence it is called an "allele." Mendel also developed 3 laws or principles. The first principle is called the, "Principle of Segregation." This principle states that the traits of an organism are determined by individual units of heredity called genes. Both adult organisms have one allele from each parent, which gives both organisms 2 alleles. The alleles are separated or "segregated" from each other with the reproductive cell formation. Mendel's second principle is the, "Principle of independent assortment." This principle states that the expression of a gene for any single trait is usually not influenced by the expression of another trait. Mendel's third and last principle is called the, "Principle of dominance." This principle states that an organism with contrasting alleles for the same gene, has one allele that maybe dominant over the other (as round is dominant over wrinkled for seed shapes in pea-plants). All the principles just stated are Mendel's Laws of genetics.

Excretion and Elimination of

Excretion and Elimination of Toxicants and their MetabolitesExcretion and Elimination of Toxicants and their Metabolites The first topic that was covered by this chapter was the excretion of wastes by the Renal system. The first step that occurs in the kidney deals with the nephron, which is the functional unit of the kidney. In the glomerulus the formation of urine begins with the passive filtration of plasma through the pores that are found in the glomerulus. The plasma is forced through these pores by hydrostatic pressure. The only things that determines if a molecule will pass through the pores of the glomerulus is it's molecular weight. The lower the molecular weight, the easier it will pass through the pores. Another determining factor will be if a molecule is bound to a large molecule. If this is true then passage through the pores will be hindered by the size of the larger molecule. Reabsorbtion of the many ions, minerals and other nutrients that escaped in the glomerular filtrate will need to be recovered.. Reabsorbtion begins in the tubules of the nephron. Anywhere from 65% to 90% of reabsorbtion occurs in these structures. Active reabsortion is used to recapture glucose, proteins, amino acids and other nutrients. Water and chloride ions are passively reabsorbed by the establishment of osmotic and electrochemical gradients. Both the Loop of Henley and collecting duct are used to establish these osmolar gradients. The tubule has a brush border that will absorb proteins and polypeptides through pinocytosis. These molecules are sometimes catabolised and converted into amino acids. and returned to the blood. Sometimes the accumulation of these proteins can lead to renal toxicity A second process that occurs in the tubules is tubular secretion. This is another mechanism used to excrete solutes. Secretion may be either passive or active. Secretions include organic bases, which occur in the pars recta of the proximal tubule. Secretions of weak bases and two weak acids occur passively. Other mechanisms involves the use of a mechanism that is called ion trapping. At a certain pH the compounds are more ionized. Outside of the tubule these compounds are non-ionized and are lipophilic. Thus they are able to diffuse across the membranes of the tubule. Once inside, the pH of the tubule will ionize them and render then unable to pass across the cell membranes. The removal of xenobiotics is dependant on many factors. First is the polarity of the xenobiotic. Polar compounds are soluble in the plasma water are more easily removed by the kidneys through the use of glomerular filtration. The faster the rate of glomerular filtration , the faster the polar xenobiotics are eliminated from the body. Other factors that affect the rate of elimination include: dose of the xenobiotic, the rate pf absorbtion, and the ability to bind to proteins as well as the polarity of the compound. In comparison lipophilic compounds will cross the cell membrane with more ease. Due to their lipohpillic properties they will follow the their concentration gradient across the membrane of the tubules and are ,therefore, easily retained by the body. If a lipophilic compound is metabolized to a more polar state then it is more easily metabolized. Another important factor that will determine excretion by the kidneys will be the pH of the environment. Those compounds that are effected by pH will have both an ionized and nonionic form. When in their nonionized form it will rebsorbed by the tubules and kept their because of their change to an ionized form. The liver is the second most important organ that is involved in the removal of wastes from the body. The primary methood of excretion involvrd the Hepatic cells of the liver. Both passive and active modes of transport are used. Bile is excreted by the hepatic cells. It is a concentration of amphipatic compounds that will aid in the transport of lipids from the small intestine. Before reaching the small intestine, via the common bile duct, it will be stored and concentrated in the gall bladder. The bile will then be reabsorbed by a process known as enterohepatic circulation. The more lipophilic or nonionized a compound is, the more readily it will be absorbed. Solubility is another factor that will determine absorbance. The rapid absorbance of these compounds does not mean that they will not be readily excreted. Some compounds are readily excreted after absorbtion. Most toxic xenobiotics are very lipophilic. This means that they will be easily ablorbed and dispursed among the tissue. Their liphilic characterizations also means that there excretion in either the urine or bile will be in very small amounts, unless they are metabolized ito more polar compounds. One of the methods used to dispose toxic lipophilics is by degradation of the large compounds into small polar fragments thatcan be eliminated through the urine or bile. Oxidative metabolism of toxic cyclic and polycyclic hydrocarbons is done with the introduction of a hyroxyl group into the ring structure. The excretion of halogenated hydrocarbons is extremely difficult. Their accumulation in the body occurs in both adipose tissue and lipid layers of the skin. They will stay there for the duration of theanimals life time. The molecular weight of a compound will determine if the compound will be excreted in the urine or feces. Any elimination of a xenobiotic will be done in association with the excretion of another compound that is normally eliminated by the body. Most gaseous and volatile xenobiotics are eliminated through the lungs. The rate of ecretion is based on how soluble the compond is in the blood, the rate of volume of respiration, and the rateof blood flow to the lungs. Asecond method used is the alveolobronchilar transport mechanism. Which will involve the use of the mucociliary bronchotracheal escalator that will end with the material being swallowed and passed out of th body. Sex linked elimination is restricted to the female.The milk excreted by the mother will contain the largest number of possible xenobiotics.The elimination of the xenobiotic is dependant on the half-lifeof the compound. Most of the compounds that are excreted are low in dosage and therefore are not lethal. Chronic exposure can be toxic to the nursing young. The type of materials that are excreted are lipophilic because they are not excreted by the other major pathways. In eggs the type of compound eliminated are also limpohpilic in nature. Fetuses are mostly effected by lipophilic compounds that are ablr to pass the placental barrier. There are cases of fatal exposure of xenobiotics to the fetus through the mother.

Evolution

Essay on Evolution There are many mechanisms that lead to evolutionary change. One of the most important mechanism in evolution is natural selection which is the differential success in the reproduction of different phenotypes resulting from the interaction of organisms with their environment. Natural selection occurs when a environment makes a individual adapt to that certain environment by variations that arise by mutation and genetic recombination. Also it favors certain traits in a individual than other traits so that these favored traits will be presented in the next generation. Another mechanism of evolution is genetic drift. Genetic drift is a random change in a small gene pool due to sampling errors in propagation of alleles or chance. Genetic drift depends greatly on the size of the gene pool. If the gene pool is large, the better it will represent the gene pool of the previous generation. If it is small, its gene pool may not be accurately represented in the next generation due to sampling error. Genetic drift usually occurs in small populations that contain less than 100 individuals, but in large populations drift may have no significant effect on the population. Another mechanism is gene flow which is when a population may gain or lose alleles by the migration of fertile individuals between populations. This may cause the allele frequencies in a gene pool to change and allow the organism to evolve. The most obvious mechanism would have to be mutation that arises in the gene pool of a population or individual. It is also the original source of the genetic variation that serves as raw material for natural selection. Not only are there mechanisms of evolution, but there is also evidence to prove that these mechanisms are valid and have helped create the genetic variety of species that exists today. Antibiotic resistance in bacteria is one example of evolutionary evidence. In the 1950's, Japanese physicians realized that a antibiotic given to patients who had a infection that caused severe diarrhea was not responding. Many years later, scientists found out that a certain strain of bacteria called Shigella contained the specific gene that conferred antibiotic resistance. Some bacteria had genes that coded for enzymes that specifically destroyed certain antibiotics such as ampicillin. From this incident, scientists were able to deduce that natural selection helped the bacteria to inherit the genes for antibiotic resistance. Scientists have also been able to use biochemistry as a source of evidence. The comparison of genes of two species is the most direct measure of common inheritance from shared ancestors. Using DNA-DNA hybridization, whole genomes can be compared by measuring the extent of hydrogen bonding between single-stranded DNA obtained from two sources. The similarity of the two genes can be seen by how tightly the DNA of one specie bonds to the DNA of the other specie. Many taxonomic debates have been answered using this method such as whether flamingos are more closely related to storks or geese. This method compared the DNA of the flamingo to be more closely related to the DNA of the stork than the geese. The only disadvantage of this method is that it does not give precise information about the matchup in specific nucleotide sequences of the DNA which restriction mapping does. This technique uses restriction enzymes that recognizes a specific sequence of a few nucleotides and cleaves DNA wherever such sequences are found in the genome. Then the DNA fragments are separated by electrophoresis and compared to the other DNA fragments of the other species. This technique has been used to compare mtDNA from people of several different ethnicity's to find out that the human species originated from Africa. The most precise and powerful method for comparing DNA from two species is DNA sequencing which determines the nucleotide sequences of entire DNA segments that have been cloned by recombinant DNA techniques. This type of comparison tells us exactly how much divergence there has been in the evolution of two genes derived from the same ancestral gene. In 1990, a team of researchers used PCR(polymerase chain reaction) a new technique to compare a short piece of ancient DNA to homologous DNA from a certain plant. Scientists have also compared the proteins between different species such as in bats and dolphins. The oldest type of evidence has been the fossil record which are the historical documents of biology. They are preserved remnants found in sedimentary rocks and are preserved by a process called pretrification. To compare fossils the ages must be determined first by relative dating. Fossils are preserved in strata, rock forms in layers that have different periods of sedimentation which occurs in intervals when the sea level changes. Since each fossils has a different period of sedimentation it is possible to find the age of the fossil. Geologists have also established a time scale with a consistent sequence of geological periods. These periods are: the Precambrian, Paleozoic, Mesozoic and the Cenozoic eras. With this time scale, geologists have been able to deduce which fossils belong in what time scale and determine if a certain specie evolved from another specie. Radioactive dating is the best method for determining the age of rocks and fossils on a scale of absolute time. All fossils contain isotopes of elements that accumulated in the organisms when they were alive. By determining an isotope's half-life which is the number of years it takes for 50% of the original sample to decay, it is possible to determine the fossil's age.

Evolution of Immunity in Invertebrates

The complex immune systems of humans and other mammals evolved over quite a long time - in some rather surprising ways. In 1982 a Russian zoologist named Elie Metchnikoff noticed a unique property of starfish larva. When he inserted a foreign object through it's membrane, tiny cells would try to ingest the invader through the process of phagocytosis. It was already known that phagocytosis occurred in specialized mammal cells but never in something less complex like a starfish. This discovery led him to understand that phagocytosis played a much broader role, it was a fundamental mechanism of protection in the animal kingdom. Metchnikoff's further studies showed that the host defense system of all animals today were present millions of years before when hey were just beginning to evolve. His studies opened up the new field of comparative immunology. Comparative immunologists studied the immune defenses of past and current creatures. They gained further insight into how immunity works. The most basic requirement of an immune system is to distinguish between one's own cells and "non-self" cells. The second job is to eliminate the non-self cells. When a foreign object enters the body, several things happen. Blood stops flowing, the immunity system begins to eliminate unwanted microbes with phagocytic white blood cells. This defensive mechanism is possessed by all animals with an innate system of immunity. Innate cellular immunity is believed to be the earliest form of immunity. Another form of innate immunity is complement, composed of 30 different proteins of the blood. If these mechanisms do not work to defeat an invader, vertebrates rely on another response: acquired immunity. Acquired immunity is mainly dealt by specialized white blood cells called lymphocytes. Lymphocytes travel throughout the blood and lymph glands waiting to attack molecules called antigens. Lymphocytes are made of two classes: B and T. B lymphocytes release antibodies while T help produce antibodies and serve to recognize antigens. Acquired Immunity is highly effective but takes days to activate and succeed because of it's complex nature. Despite this, acquired immunity offers one great feature: immunological memory. Immunological Memory allows the lymphocytes to recognize previously encountered antigens making reaction time faster. For this reason, we give immunizations or booster shots to children. So it has been established that current vertebrates have two defense mechanisms: innate and acquired, but what of older organisms ? Both mechanisms surprisingly enough can be found in almost all organisms (specifically phagocytosis). The relative similarities in invertebrate and vertebrate immune systems seem to suggest they had common precursors. The oldest form of life, Protozoan produce these two immune functions in just one cell. Protozoan phagocytosis is not uncommon to that of human phagocytic cells. Another basic function of immunity, distinguishing self from non-self, is found in protozoan who live in large colonies and must be able to recognize each other. In the case of metazoan, Sponges, the oldest and simplest, are able to do this as well refusing grafts from other sponges. This process of refusing is not the same in vertebrates and invertebrates though. Because vertebrates have acquired immunologic memory they are able to reject things faster than invertebrates who must constantly "re-learn" what is and is not self. Complement and lymphocytes are also missing from invertebrates, but which offer an alternative yet similar response. In certain invertebrate phyla a response called the prophenoloxidase (proPO) system occurs. Like the complement system it is activated by enzymes. The proPO system has also been linked to blood coagulation and the killing of invading microbes. Invertebrates also have no lymphocytes, but have a system which suggests itself to be a precursor of the lymph system. For instance, invertebrates have molecules which behaving similarly to antibodies found in vertebrates. These lectin molecules bind to sugar molecules causing them to clump to invading objects. Lectins have been found in plants, bacteria, and vertebrates as well as invertebrates which seems to suggest they entered the evolutionary process early on. This same process occurs in human innate immune systems with collections of proteins called collectins which cover microbes n a thin membrane to make them easier to distinguish by phagocytes. And although antibodies are not found in invertebrates a similar and related molecule is. Antibodies are members of a super family called immunoglobulin which is characterized by a structure called the Ig fold. It is believed that the Ig fold developed during the evolution of metazoan animals when it became important to distinguish different types of cells wi thin one animal. Immunoglobulins such as Hemolin have been found in moths, grasshoppers, and flies, as well as lower vertebrates. This suggests that antibody-based defense systems, although only active in vertebrates, found their roots in the invertebrate immune system. Evolution seems to have also conserved many of the control signals for these defense mechanisms. Work is currently being done to isolate invertebrate molecules similar to the cytokines of vertebrates. Cytokines are proteins that either stimulate or block out other cells of the immune system as well as affecting other organs. These proteins are critical for the regulation of vertebrate immunity. It is suspected that invertebrates will share common cytokines with vertebrates or at least a close replication. Proteins removed from starfish have been found to have the same physical, chemical, and biological properties of interleukins (IL-1, IL-6), a common cytokine of vertebrates. This research has gone far enough to conclude that invertebrates possess similar molecules to the three major vertebrate cytokines. In the starfish, cells called coelomocytes were found to produce IL-1. The IL-1 stimulated these cells to engulf and destroy invaders. It is thus believed that invertebrate cytokines regulate much of their host's defense response, much like the cytokines of vertebrate animals in innate immunity. Comparative Immunology has also found defense mechanisms first in invertebrates only later to be discovered in vertebrates. Invertebrates use key defensive molecules such as antibacterial peptides and proteins, namely lysozyme, to expose bacterial cell walls. Thus targeting the invader. This offers great potential for medicinal purposes, because lysozyme is also found in the innate immunity of humans in it's defense of the oral cavity against bacteria. Peptides of the silk moth are currently being developed as antibacterial molecules for use in humans. Two peptides found in the skin of the African clawed frog actively fight bacteria, fungi, and protozoa. Antibodies which bind to these two peptides also bind to the skin and intestinal lining of humans. The potential of these peptide antibiotics only now being discovered is a rather considerable thing to ponder. For that reason it is surprising that such little attention has been paid to invertebrate immune responses. In the end, the complexity of vertebrate immune systems can only be understood by studying the less complex systems of invertebrates. Further studies look to explain immunity evolution as well as aid in the solving of problems of human health.

Diffrences and Effects of Natural and Synthetic Fertilizers

At the core of the growth and germination of plants lie the nutrients they receive from the soil. The nutrients required for growth are classified into two groupings, macronutirents and micronutrients. Macronutrients are those that are needed in very large amounts, and whose absence can do a great harm to the development of the plant life. These nutrients include calcium, nitrogen, phosphorus, and potassium, and are very sparse in most soils, making them the primary ingredients in most fertilizers. The other, more common macronutrients are called secondary nutrients, as they are not of as much importance. Micronutrients, the other classification, consist of all the other elements and compounds required for sufficient growth, such as iron, boron, manganese, copper, zinc, molybdenum and chlorine. In some cases, these nutrients are found to be missing in soils, but it is extremely uncommon. As plants need to retrieve all of their nutrients from the soil, many methods have been developed in order to find ways to improve or change the soil to suit the plant's needs. Soil, in science as well as in common gardening, must undergo detailed inspection, to detect such things as the pH of the soil. A soil with a pH above 7.0 is called an alkaline soil, and will commonly kill plants. Mineral content, as mentioned above, is also a concern, and must be clearly monitored. After inspection, it is common for minor organic materials outside fertilizers to be applied, such as peat moss, ground bark, or leaf mold. It is after these steps that fertilization must occur, leading to a debate which has plagued gardeners and scientists alike: organic or chemical? Fertilizers, in both natural and synthetic breeds, are carriers of the primary and secondary nutrients that are found less often in even the most fertile soils. Fertilizers are mixtures that are mixed or applied to soil, thus greatly increasing its potency and maximizing plant growth. As mentioned before, however, there are both natural and inorganic fertilizers, all with varying effects. The compositional differences of these types are great, indeed. Natural fertilizers, as one would expect, are totally organic, and usually come from the manure of animals. These are the fertilizers that produced the forests of the world, among much other plant life in ecosystems, and have been used since ancient times. Chemical fertilizers are a more recent invention, consisting of carefully concentrated mixtures of nutrients, formulated for quick growth. These can take many forms, from powder, to "dirt", to even tablets! Natural fertilizers, as mentioned above, include the various types of manure and other animal waste products, as well as compost, which is a mixture of various decaying plant and animal products mixed together to form a variable "feast" of nutrients and minerals. Uncountable types of these nutrient boosters have been developed by agriculturists, involving such oddities as kelp parts, dish meal, blood meal, and even ground gypsum! These different fertilizers tend to work well with plants, and many scientific agricultural experiments have shown them to be very effective in long term stages, with the only drawback being a slow growth process. Crops grown this way have shown to become, in the long run, larger, healthier, and above all, 100% non-toxic. The other method of fertilization that of chemicals offers major advantages over organic, but just as undesirable complications. Chemical fertilizers have the major advantage of containing a near perfect mixture of all the nutrients necessary for growth, as well as being time-released to give the plant a steady flow of mineral supply. This causes extremely fast growth, with an initially healthy stock. Unfortunately these chemicals, which all their benefit, can easily cause what is called "fertilizer burn". This state is where fertilizer produces too many nutrients: this overloads the plants biological systems, and effectively kills the plant. Also, the chemicals often harm plants over time, causing ill health and quicker death than natural fertilizers, as soil organisms die out form over exposure, reducing the soil quality. Plants grown with chemical fertilizers have a greater chance of disease and toxicity, but the initial growth usually offsets these complications

Diversity of Plants

DIVERSITY OF PLANTS Plants evolved more than 430 million years ago from multicellular green algae. By 300 million years ago, trees had evolved and formed forests, within which the diversification of vertebrates, insects, and fungi occurred. Roughly 266,000 species of plants are now living. The two major groups of plants are the bryophytes and the vascular plants; the latter group consists of nine divisions that have living members. Bryophytes and ferns require free water so that sperm can swim between the male and female sex organs; most other plants do not. Vascular plants have elaborate water- and food conducting strands of cells, cuticles, and stomata; many of these plants are much larger that any bryophyte. Seeds evolved between the vascular plants and provided a means to protect young individuals. Flowers, which are the most obvious characteristic of angiosperms, guide the activities of insects and other pollinators so that pollen is dispersed rapidly and precisely from one flower to another of The same species, thus promoting out crossing. Many angiosperms display other modes of pollination, including self-pollination. Evolutionary Origins Plants derived from an aquatic ancestor, but the evolution of their conducting tissues, cuticle, stomata, and seeds has made them progressively less dependent on water. The oldest plant fossils date from the Silurian Period, some 430 million years ago. The common ancestor of plants was a green alga. The similarity of the members of these two groups can be demonstrated by their photosynthetic pigments (chlorophyll a and b,) carotenoids); chief storage product (starch); cellulose-rich cell walls (in some green algae only); and cell division by means of a cell plate (in certain green algae only). Major Groups As mentioned earlier, The two major groups of plants are The bryophytes--mosses, liverworts, and hornworts--and The vascular plants, which make up nine other divisions. Vascular plants have two kinds of well-defined conducting strands: xylem, which is specialized to conduct water and dissolved minerals, and phloem, which is specialized to conduct The food molecules The plants manufacture. Gametophytes and Sporophytes All plants have an alternation of generations, in which haploid gametophytes alternate with diploid sporophytes. The spores that sporophytes form as a result of meiosis grow into gametophytes, which produce gametes--sperm and eggs--as a result of mitosis. The gametophytes of bryophytes are nutritionally independent and remain green. The sporophytes of bryophytes are usually nutritionally dependent on The gametophytes and mostly are brown or straw-colored at maturity. In ferns, sporophytes and gametophytes usually are nutritionally independent; both are green. Among The gymnosperms and angiosperms, The gametophytes are nutritionally dependent on the sporophytes. In all seed plants--gymnosperms and angiosperms--and in certain lycopods and a few ferns, the gametophytes are either female (megagametophytes) or male (microgametophytes). Megagametophytes produce only eggs; microgametophytes produce only sperm. These are produced, respectively, from megaspores, which are formed as a result of meiosis within megasporangia, and microspores, which are formed in a similar fashion within microsporangia. In gymnosperms, the ovules are exposed directly to pollen at the time of pollination; in angiosperms, the ovules are enclosed within a carpel, and a pollen tube grows through the carpel to the ovule. The nutritive tissue in gymnosperm seeds is derived from the expanded, food-rich gametophyte. In angiosperm seeds, the nutritive tissue, endosperm, is unique and is formed from a cell that results from the fusion of the polar nuclei of the embryo sac with a sperm cell. The pollen of gymnosperms is usually blown about by the wind; although some angiosperms are also wind-pollinated, in many the pollen is carried from flower to flower by various insects and other animals. The ripened carpels of angiosperm grow into fruits, structures that are as characteristic of members of the division as flowers are. GYMNOSPERMS AND ANGIOSPERMS Gymnosperms Gymnosperms are non-flowering plants. They also make up four of the five divisions of the living seed plants, with angiosperms being the fifth. In gymnosperms, the ovules are not completely enclosed by the tissues of the sporophytic individual on which they are borne at the time of pollination. Common examples are conifers, cycads, ginkgo, and gnetophytes. Fertilization of gymnosperms is unique. The cycad sperm, for example, swim by means of their numerous, spirally arranged flagella. Among the seed plants, only the cycads and Ginkgo have motile sperm. The sperm are transported to the vicinity of the egg within a pollen tube, which bursts, releasing them; they then swim to the egg, and fertilize it. Angiosperms The flowering plants dominate every spot on land except for the polar regions, the high mountains, and the driest deserts. Despite their overwhelming success, they are a group of relatively recent origin. Although they may be about 150 million years old as a group, the oldest definite angiosperm fossils are from about 123 million years ago. Among the features that have contributed to the success of angiosperms are their unique reproductive features, which include the flower and the fruit. Angiosperms are characterized primarily by features of their reproductive system. The unique structure known as the carpel encloses the ovules and matures into the fruit. Since the ovules are enclosed, pollination is indirect. History The ancestor of angiosperms was a seed-bearing plant that was probably already pollinated by insects to some degree. No living group of plants has the correct combination of characteristics to be this ancestor, but seeds have originated a number of times during the history of the vascular plant. Although angiosperms are probably at least 150 million years old as a group, the oldest definite fossil evidence of this division is pollen from the early Cretaceous Period. By 80 or 90 million years ago, angiosperms were more common worldwide that other plant groups. They became abundant and diverse as drier habitats became widespread during the last 30 million years or so. Flowers and Fruits Flowers make possible the precise transfer of pollen, and therefore, outcrossing, even when the stationary individual plants are widely separated. Fruits, with their complex adaptations, facilitate the wide dispersal of angiosperms. The flowers are primitive angiosperms had numerous, separate, spirally arranged flower parts, as we know from the correlation of flowers of this kind with primitive pollen, wood, and other features. Sepals are homologous with leaves, the petals of most angiosperms appear to be homologous with stamens, although some appear to have originated from sepals; and stamens and carpels probably are modified branch systems whose spore-producing organs were incorporated into the flower during the course of evolution. Bees are the most frequent and constant visitors of flowers. They often have morphological and physiological adaptations related to their specialization in visiting the flowers of particular plants. Flowers visited regularly by birds must produce abundant nectar to provide the birds with enough energy so theat they will continue to be attracted to them. The nectar visited plants tends to be well protected by the structure of the flowers. Fruits, which are characteristic of angiosperms, are extremely diverse. The evolution of structures in particular fruits that have improved their possibilities for dispersal in some special way has produced many examples of parallel evolution. Fruits and seeds are highly diverse in terms of their dispersal, often displaying wings, barbs, or other structures that aid their dispersal. Means of fruit dispersal are especially important in the colonization of islands or other distant patches of suitable habitat. VASCULAR PLANT STRUCTURE Vegetative Organs A vascular plant is basically an axis consisting of root and shoot. The root penetrates the soil and absorbs water and various ion, which are crucial for plant nutrition, and it also anchors the plant. The shoot consists of stem and leaves. The stem serves as a framework for the positioning of the leaves, the principal places where photosynthesis takes place. Plant Tissue The stems and roots of vascular plants differ in structure, but both grow at their apices and consist of the same three kinds of tissues: 1. Vascular tissue--conducts materials within the structure; it consists of two types: (1) xylem--conducts water and dissolved minerals (2) phloem--conducts carbohydrates, mainly sucrose, which the plant uses for food, as well as hormones, amino acids, and other substances necessary for plant growth 2. Ground tissue--performs photosynthesis and stores nutrients; the vascular tissue is embedded 3. Dermal tissue--the outer protective covering of the plant Growth Plants grow by means of their apical meristems, zones of active cell division at the ends of the roots and the shoots. The apical meristem gives rise to three types of primary meristems, partly differentiated tissues in which active cell division continues to take place. These are the protoderm, which gives rise to the epidermis; the procambium, which gives rise to the vascular tissues; and the ground meristem, which becomes the ground tissue. The growth of leaves is determinate, like that of flowers; the growth of stems and roots is indeterminate. Water reaches the leaves of a plant after entering it through the roots and passing upward via the xylem. Water vapor passes out of the leaves by entering intercellular spaces, evaporating, and moving out through stomata. Stems branch by means of buds that form externally at the point where the leaves join the stem; roots branch by forming centers where pericycle cells begin dividing. Young roots grow out through the cortex, eventually breaking through the surface of the root. Propagation An angiosperm embryo consists of an axis with one or two cotyledons, or seedling leaves. In the embryo, the epicotyl will become the shoot, and the radicle, a portion of the hypocotyl, will become the root. Food for the developing seedling may be stored in the endosperm at maturity or in the embryo itself. NUTRITION AND TRANSPORT IN PLANTS The body of a plant is basically a tube embedded in the ground and extending up into the light, where expanded surfaces--the leaves--capture the sun's energy and participate is gas exchange. The warming of the leaves by sunlight increases evaporation from them, creating a suction that draws water into the plant through the roots and up the plant through the xylem to the leaves. Transport from the leaves and other photosynthetically active structures to the rest of the plant occurs through the phloem. This transport is driven by osmotic pressure; the phloem actively picks up sugars near the places where they are produced, expanding ATP in the process, and unloads them where they are used. Most of the minerals critical to plant metabolism are accumulated by the roots, which expend ATP in the process. The mineral are subsequently transported in the water stream through the plant and distributed to the areas where they are used--another energy-requiring process. Soil Soils are produced by the weathering of rocks in the earth's crust; they vary according to the composition of those rocks. The crust includes about 92 naturally occurring elements. Most elements are combined into inorganic compounds called minerals; most rocks consist of several different minerals. They weather to give rise to soils, which differ according to the composition of their parent rocks. The amount of organic materials in soils affects their fertility and other properties. About half of the total soil volume is occupied by empty space, which my be filled with air or water depending on moisture conditions. Not all of the water in soil, however, is available to plants, because of the nature of water itself. Water Movement Water flows through plants in a continuous column, driven mainly by transpiration through the stomata. The plant can control water loss primarily by closing its stomata. The cohesion of water molecules and their adhesion to the walls of the very narrow cell columns through which they pass are additional important factors in maintaining the flow of water to the tops of plants. The movement of water, with its dissolved sucrose and other substances, in the phloem does not require energy. Sucrose is loaded into the phloem near sites of synthesis, or sources, using energy supplied by the companion cells or other nearby parenchyma cells. The sucrose is unloaded in sinks, at the places where it is required. The water potential is lowered where the sucrose is loaded into the sieve tube and raised where it is unloaded. Nutrient Movement Apparently most of the movement of ions into a plant takes place through the protoplast of the cells rather than between their walls. Ion passage through cell membranes seems to be active and carrier mediated, although the details are not well understood. The initial movement of nutrients into the roots is an active process that requires energy and that, as a result, specific ions can be can be maintained within the plant at very different concentrations from the soil. When roots are deprived of oxygen, they lose their ability to absorb ions, a definite indication that they require energy for this process to occur successfully. A starving plant--one from which light has been excluded--will eventually exhaust its nutrient supply and be unable to replace it. Once the ions reach the xylem, they are distributed rapidly throughout the plant, eventually reaching all metabolical active parts. Ultimately the ions are removed from eh roots and relocated to other parts of the plant, their passage taking place in the xylem, where phosphorus, potassium, nitrogen, and sometimes iron may be abundant in certain seasons. The accumulation of ions by plants is an active process that usually takes place against a concentrations gradient and requires the expenditure of energy. Carbohydrates Movement Carbohydrate movement is where water moves through the phloem as a result of decreased water potential in areas of active photosynthesis, where sucrose is actively being loaded into the sieve tubes, and increased water potential in those areas where sucrose is being unloaded. Energy for the loading and unloading of the sucrose and other molecules is supplied by companion cells or other parenchyma cells. However, the movement of water and dissolved nutrients within the sieve tubes is a passive process that does not require the expenditure of energy. Plant Nutrients Plants require a number of inorganic nutrients. Some of these are macronutrients, which the plants need in relatively large amounts, and others are micronutrients, those required in trace amounts. There are nine macronutrients: 1. Carbon 2. Hydrogen 3. Oxygen 4. Nitrogen 5. Potassium 6. Calcium 7. Phosphorus 8. Magnesium 9. Sulfur that approach or exceed 1% of a plant's dry weight, whereas there are seven micronutrients: 1. Iron 2. Chlorine 3. Copper 4. Manganese 5. Zinc 6. Molybdenum 7. Boron that are present only in trace amounts. PLANT DEVELOPMENT Differentiation in Plant Plants, unlike animals, are always undergoing development. Their cells do not move in relation to one another during the course of development, which is a continuous process. Animals undergo development according to a fixed blueprint that is followed rigidly until they are mature. Plants, in contrast, develop constantly. The course of their development is mediated by hormones, which are produced as a result of interactions with the external environment. Embryonic Development Embryo development in animals involves extensive movements of cells in relation to one another, but the same process in plants consists of an orderly production of cells, rigidly bound by their cellulose-rich cell wall. The cells do not move in relation to one another in plant development, as they do in animal development. By the time about 40 cells have been produced in an angiosperm embryo, differentiation begins; the meristematic shoot and root apices are evident. Germination in Plants In the germination of seeds, the mobilization of the food reserves stored in the cotyledons and in the endosperm is critical. In the cereal grains, this process is mediated by hormones of the kind known as gibberellins, which appear to activate transcription of the loci involved in to production of amylase and other hydrolase enzymes. REGULATION OF PLANT GROWTH . Plant Hormones Hormones are chemical substances produced in small quantities in one part of an organism and transported to another part of the organism, where they bring about physiological responses. The tissues in which plant hormones are produced are not specialized particularly for that purpose, nor are there usually clearly defined receptor tissues or organs. The major classes of plant hormones--auxins, cytokinins, gibberellins, ethylene, and abscisic acid--interact in complex ways to produce a mature, growing plant. Unlike the highly specific hormones of animals, plant hormones are not produced in definite organs nor do they have definite target areas. They stimulate or inhibit growth in response to environmental clues such as light, day length, temperature, touch, and gravity and thus allow plants to respond efficiently to environmental demands by growing in specific directions, producing flowers, or displaying other responses appropriate to their survival in a particular habitat. Tropisms Tropisms in plants are growth responses to external stimuli. A phototropism is a response to light, gravvitropism is a response to gravity, and thigmotropism is a response to touch. Turgor Movement Turgor movements are reversible but important elements in adaptation of plants to their environments. By means of turgor movements, leaves, flowers, and other structures of plants track light and take full advantage of it. Dormancy Dormancy is a necessary part of plant adaptation that allows a plant to bypass unfavorable seasons, such as winter, when the water my be frozen, or periods of drought. Dormancy also allows plants to survive in many areas where they would be unable to grow otherwise.