Text A. The Largest Organism on Earth Is a Fungus

NATURALLY SPEAKING

Учебное пособие

по развитию навыков чтения

и устной речи

Данное учебное пособие предназначено для студентов 2-3 курсов и аспирантов биохимических специальностей биологических факультетов университетов и имеет своей целью дальнейшее совершенствование уже полученных навыков чтения и устной речи. Пособие содержит оригинальные тексты на английском языке, взятые из научных журналов (Science, Scientific American, New Scientist). Тексты и задания, представленные в пособии, рассчитаны на обучающихся продвинутого уровня и содержат задания для обсуждения и вопросы, предполагающие значительный уровень как лингвистической подготовки, так и знаний в сфере биологии.

Введение

Данное учебное пособие предназначено для студентов биологического факультета 2-3 курсов и аспирантов биохимического отделения и имеет своей целью совершенствование уже полученных навыков чтения и устной речи. Тексты и задания, представленные в пособии, рассчитаны на обучающихся продвинутого уровня и содержат задания для обсуждения и вопросы, предполагающие значительный уровень как лингвистической подготовки, так и знаний в сфере биологии.

Учебное пособие состоит из 3 разделов (section) по 5 уроков (unit) в каждом в соответствии с возрастанием объема и сложности текстов и заданий. Каждый раздел рассчитан на один семестр, а каждый урок – на 3-4 занятия. Тематическая подборка текстов и их расположение определяются помимо прочего и информированностью студентов: некоторые темы в полном объеме и с достаточным знанием фактического материала они могут обсуждать только к 3 курсу.

Чтение в данном учебном пособии представлено не только как цель, но и как средство обучения, выступая в качестве содержательной базы при совершенствовании навыков говорения. В каждом уроке представлены тексты, направленные на развитие трех основных видов чтения – просмотрового чтения (reading for general information), чтения с выборочным извлечением нужной информации (reading for specific information) и чтения с полным пониманием (reading for detail). После текстов даются задания, развивающие навыки монологического и диалогического высказывания, ведения беседы и аргументации, для совершенствования которых и предназначено учебное пособие. По этой же причине в него не включены упражнения по грамматике. В плане формирования грамматических навыков чтения задачи данного учебного пособия ограничиваются лишь увеличением количества легко распознаваемых грамматических явлений и развитием на этой базе механизма структурной антиципации.

В ходе обучения осуществляется совершенствование умения говорить как в диалогической, так и в монологической форме. При развитии диалогической формы речи акцент сделан на диалоге-обмене мнениями и информацией. При обучении монологической форме речи большое внимание уделяется работе над рассуждением, выражением своего отношения, сравнительной оценкой мнений и позиций, интерпретацией и выражением причинно-следственных связей.

В пособии представлены оригинальные неадаптированные тексты (в некоторых случаях – фрагменты текстов или их сокращенный вариант), взятые из авторитетных научных изданий и их интернет-версий – Nature, Scientific American, New Scientist, а также научной колонки The New York Times. Необходимо отметить, что приведенные в текстах точки зрения зачастую имеют провокационный характер и могут вызвать сильную реакцию учащихся – несогласие, неодобрение и даже полное отрицание заявленных фактов. Некоторые тексты прямо противоречат друг другу. Такая стратегия выбрана автором вполне сознательно и представляется оправданной, поскольку напрямую отвечает целям пособия – на основе прочитанного совершенствовать навыки устной речи, ведения научной дискуссии и аргументации. В задачи автора входило сделать каждый урок учебного пособия познавательным и интересным для студентов всех специальностей, сталкивая альтернативные мнения, и создавая тем самым условия для взаимообогащающего общения.

При отборе текстов пристальное внимание уделялось и их терминологической насыщенности; освоение лексики подчинено методическому принципу «снежного кома», когда лексика предыдущих уроков и текстов снова встречается и отрабатывается в последующих. Некоторые темы также перекликаются друг с другом, и уже проработанные ранее вопросы расширяются в следующих уроках. Так, например, нарушения сна и их причины (урок Sleep) позднее рассматриваются при обсуждении воздействия алкоголя на организм человека (урок Alcohol). Основные термины урока Human Genetics пересекаются с терминами урока Human Evolution.

Каждый урок (unit) открывается эпиграфом, отражающим его основную мысль. В первом упражнении предлагаются вопросы для обсуждения по теме урока (What do you know about…), а также в некоторых уроках даны основные термины, которые студенты должны объяснить.

Разделы различаются не только по объему и степени сложности текстов, но и по их количеству и предлагаемым упражнениям. В первом разделе даются самые простые небольшие тексты, а также упражнения на отработку лексики, которые далее уже не встречаются. Во втором и третьем разделах тексты становятся сложнее и длиннее с нарастающей степенью терминологической насыщенности. Предлагаемые к текстам задания в форме вопросов множественного выбора (multiple choice), вопросов «верно-неверно» (true/false), задания на заполнение пропусков (blank filling) и соотнесение информации (matching information) проверяют умение студентов извлекать информацию из текстов, выявлять причинно-следственные связи, интерпретировать отношение говорящего.

В связи с тем, что учебное пособие полностью построено на аутентичных текстах разного характера, большое значение придается самостоятельному обращению учащихся к словарям и справочным изданиям, тем самым у студентов и аспирантов формируется потребность и развивается умение использования одно- и двуязычной справочной литературы и источников.

Последним заданием каждого урока является составление краткого обзора всех рассмотренных в его рамках вопросов. Данное задание направлено на развитие навыков анализа, реферирования и устных презентаций.

В конце каждого из трех разделов учебного пособия (section) приводится список рекомендуемых тем для устных докладов и презентаций студентов.

Contents

Section 1

Unit 1. Human body ……………………………………………………………………..…..3

Unit 2. Water ………………………………………………………………………………….6

Unit 3. Fungi …………………………………………………………………………………..9

Unit 4. Bacteria ……………………………………………………………………………….12

Unit 5. Domesticated animals …………………………………………………………..…15

Recommended Report and Presentation Topics ………………………………………18

Section 2

Unit 6. Brain ………………………………………………………………………….…………19

Unit 7. Sleep …………………………………………………………………………………….22

Unit 8. Coffee …………………………………………………………………………………...25

Unit 9. Human Genetics and Diversity …………………………………………….……….28

Unit 10. Animal adaptations ………………………………………………………….………31

Recommended Report and Presentation Topics …………………………………………34

Section 3

Unit 11. Human Evolution ………………………………………………….……………….35

Unit 12. Alcohol ……………………………………………………………………………….39

Unit 13. Sex and Gender …………………………………………………………………….43

Unit 14. Aging ………………………………………………………………………...……….47

Unit 15. Food ……………………………………………………………………….………….51

Recommended Report and Presentation Topics ………………………………………..57

Section 1.

Unit 1. Human Body

Any lover of humanity who looks back on the achievements of medical science must feel his heart glow and his right ventricle expand with the percardiac stimulus of a permissible pride.

Stephen B. Leacock, Canadian economist and humorist

Exercise 1. What do you know about the human body?

1. How is our body prepared for the physical stresses and wear of human life? Speak about each system of organs.

2. What are the most surprising abilities of the human body?

3. What is the adaptive significance of four-chambered heart and greater and lesser circulation?

4. How does the human body adapt to changes?

5. What medical achievements have most significantly changed human life and health care?

Exercise 2. Match the terms which will be used in the text (1-6) with their definitions (A-F).

1. corpus callosum 2. cerebral hemispheres 3. stroke 4. cerebrospinal fluid 5. seizure[1] 6. congenital

A. A pair of structures, originating from the forebrain, that contain the centers concerned with the major senses, voluntary muscle activities, and higher brain functions, such as language and memory. B. Describes phenotypic character or condition recognizable at, and usually before, birth. The term usually refers to hereditary or inborn conditions that are most often harmful. C. A clear watery fluid containing glucose, salts, and a few white blood cells, that is found in the internal cavities and between the surrounding membranes of the central nervous system. It cushions and protects nerve tissues. D. A paroxysmal event due to abnormal, excessive, hypersynchronous discharges from an aggregate of CNS neurons. Epilepsy is diagnosed when there are recurrent numerous events due to a chronic, underlying process. E. A thick band of nerve fibers that connects the two cerebral hemispheres in the brain of placental mammals. It enables coordination of the functions of the two hemispheres. F.A rapidly developing loss of brain function(s) due to disturbance in the blood supply to the brain, caused by a blocked or burst blood vessel.

Exercise 3. Now read the text about a unique brain operation.

Strange but True: When Half a Brain Is Better than a Whole One

You might not want to do it, but removing half of your brain will not significantly impact who you are

By Charles Choi

The operation known as hemispherectomy—where half the brain is removed—sounds too radical to ever consider, much less perform. In the last century, however, surgeons have performed it hundreds of times for disorders uncontrollable in any other way. Unbelievably, the surgery has no apparent effect on personality or memory.

The first known hemispherectomy was performed on a dog in 1888 by German physiologist Friedrich Goltz. In humans, neurosurgeon Walter Dandy pioneered the operation at Johns Hopkins University in 1923 on a brain tumor patient. (That man lived for more than three years before ultimately succumbing to cancer.) The procedure is among the most drastic kinds of brain surgery—"You can't take more than half. If you take the whole thing, you've got a problem," Johns Hopkins neurologist John Freeman quips.

One side effect Canadian neurosurgeon Kenneth McKenzie reported in 1938 after a hemispherectomy on a 16-year-old girl who suffered a stroke was that her seizures stopped. Nowadays, the surgery is performed on patients who suffer dozens of seizures every day that resist all medication, and which are due to conditions that mostly affect one hemisphere. "These disorders are often progressive and damage the rest of the brain if not treated," University of California, Los Angeles, neurosurgeon Gary Mathern says. Freeman concurs: "Hemispherectomy is something that one only does when the alternatives are worse."

Anatomical hemispherectomies involve the removal of the entire hemisphere, whereas functional hemispherectomies only take out parts of a hemisphere, as well as severing the corpus callosum, the fiber bundle that connects the two halves of the brain. The evacuated cavity is left empty, filling with cerebrospinal fluid in a day or so. The strength of anatomical hemispherectomies, a specialty of Hopkins, lies in the fact that "leaving even a little bit of brain behind can lead seizures to return," Freeman says. On the other hand, functional hemispherectomies, which U.C.L.A. surgeons usually perform, lead to less blood loss. "Our patients are usually under two years of age, so they have less blood to lose," Mathern says. Most Hopkins hemispherectomy patients are five to 10 years old.

Neurosurgeons have performed the operation on children as young as three months old. Astonishingly, memory and personality develop normally. A recent study found that 86 percent of the 111 children who underwent hemispherectomy at Hopkins between 1975 and 2001 are either seizure-free or have nondisabling seizures that do not require medication. The patients who still suffer seizures usually have congenital defects or developmental abnormalities, where brain damage is often not confined to just one hemisphere, Freeman explains. Another study found that children that underwent hemispherectomies often improved academically once their seizures stopped. "One was champion bowler of her class, one was chess champion of his state, and others are in college doing very nicely," Freeman says.

Of course, the operation has its downside: "You can walk, run—some dance or skip—but you lose use of the hand opposite of the hemisphere that was removed. You have little function in that arm and vision on that side is lost," Freeman says. Remarkably, few other impacts are seen. If the left side of the brain is taken out, "most people have problems with their speech, but it used to be thought that if you took that side out after age two, you'd never talk again, and we've proven that untrue," Freeman says. "The younger a person is when they undergo hemispherectomy, the less disability you have in talking. Where on the right side of the brain speech is transferred to and what it replaces is something nobody has really worked out."

Mathern and his colleagues have recently conducted the first functional magnetic resonance imaging study into hemispherectomy patients, investigating how their brain changes with physical rehabilitation. Probing how the remaining cerebral hemispheres of these patients acquire language, sensory, motor and other functions "could shed a great deal of light on the brain's plasticity, or ability to change," Freeman notes. Still, having half a brain—and therefore only the use of one hand and half a field of vision in each eye—is a condition most would prefer to avoid. (From Scientific American Online, May 24, 2007)

Exercise 4. The words on this list are all verbs (some of them were used in the text). What are the corresponding noun forms? Write them in the second column. The first one has been done for you as an example.

1. to diagnose - diagnosis

2. to examine - _______________

3. to prescribe - ______________

4. to suffer - _________________

5. to operate - _______________

6. to cure - __________________

7. to recover - _______________

8. to analyse - _______________

9. to infect - _________________

10. to carry - ________________

11. to replace - ______________

12. to degenerate - ___________

13. to paralyse - ______________

14. to treat – _________________

15. to affect – ________________

16. to damage - _______________

Exercise 5. Rewrite the sentences below, changing the verbs (which are in bold) to nouns. Do not change the meaning of the sentences, but be prepared to make grammatical changes if necessary. The first one has been done for you as an example.

1. I diagnosedthat the patient had a heart condition.   2. I examinedthe patient fully. 3. I prescribeda course of antibiotics. 4. He sufferedvery little. 5. Ten per cent of the population are thought to carrythe bacteria. 6. This disease cannot be cured. 7. He has recoveredfully. 8. The lab analysedthe blood sample. 9. We found that the tissue was infected. 10. We operatedimmediately. 11. We replacedthe patient's hip. 12. His condition has degenerated. 13. His arm was paralysedafter the stroke

1. My diagnosis was that the patient had a heart condition. 2. I made a full 3. I wrote a 4. He experienced very little 5. Ten per cent of the population are thought to be   6. There is no 7. He has made a full 8. The lab made an 9. We found an 10. The 11. The patient was given a hip 12. There has been a 13. He suffered

Exercise 6. Now make up your own sentences with the following verbs and corresponding nouns: to treat, to affect, to damage.

Exercise 7. Using the information from the text in Exercise 3 speak on the following:

1. History of hemispherectomy.

2. Surgical indication.

3. Difference between functional and anatomical hemispherectomy.

4. Positive and negative consequences of hemispherectomy.

5. Implications of the operation for fundamental science.

Exercise 8. Prove that the human body has unique adaptive abilities. Use the information from the text in Exercise 3 and additional facts, if necessary. Combine all the information into one report.

Unit 2. Water

Water, thou hast no taste, no color, no odor; canst not be defined, art relished while ever mysterious. Not necessary to life, but rather life itself, thou fillest us with a gratification that exceeds the delight of the senses.

Antoine de Saint-Exupery, The Wisdom of the Sands

Exercise 1. What do you know about water?

1. What are the functions of water in human organism? What processes is water involved in?

2. What is the function of water in photosynthesis?

3. Can water produce negative effect on the human body?

4. What is dehydration? What negative consequences can it cause?

5. Why does daily water consumption of different classes of animals – amphibians, reptiles, birds, mammals – differ?

6. Do freshwater and saltwater kinds of fish have any difference in metabolism?

7. Why can’t we use distilled water for drinking?

Exercise 2. How long can the average person survive without water?

Now read the explanation given by Randall K. Packer, a professor of biology at George Washington University, and check if your answer was correct.

It is impossible to give an answer to this seemingly simple question because many variable factors determine a person's survival time. Under the most extreme conditions, death can come rather quickly. For example, a child left in a hot car or an athlete exercising hard in hot weather can dehydrate, overheat and die in a period of a few hours. An adult in comfortable surroundings, in contrast, can survive for a week or more with no, or very limited, water intake.

To stay healthy, humans must maintain water balance, which means that water losses must be made up for by water intake. We get water from food and drink and lose it as sweat and urine. Another major route of water loss usually goes unnoticed: because we exhale air that is water saturated, we lose water each time we exhale. On a cold day we see this water in the air as it condenses.

Exposure to a hot environment and vigorous exercise both increase body temperature. The only physiological mechanism humans have to keep from overheating is sweating. Evaporation of sweat cools blood in vessels in the skin, which helps to cool the entire body. Under extreme conditions an adult can lose between one and 1.5 liters of sweat an hour. If that lost water is not replaced, the total volume of body fluid can fall quickly and, most dangerously, blood volume may drop. If this happens, two potentially life-threatening problems arise: sweating stops and body temperature can soar even higher, while blood pressure decreases because of the low blood volume. Under such conditions, death occurs quickly. Because of their relatively larger skin surface-to-volume ratio, children are especially susceptible to rapid overheating and dehydration.

The combination of dehydration and overheating sends thousands of people to hospital emergency rooms each year, but diarrhea, excessive vomiting, and kidney failures of various sorts can also cause dehydration. A person can stay hydrated by drinking many different kinds of fluids in addition to water, with one exception. Drinking alcoholic beverages actually causes dehydration because ethanol depresses the level of the anti-diuretic hormone arginine vasopressin (AVP). As a result, urine volume increases such that more fluid is lost in urine than is gained by consuming the beverage.

Exercise 3. Give definitions to the following terms connected with water:

To dehydrate / to rehydrate, to condense, fluid, water balance, hormone, kidney, sweating, evaporation.

Exercise 4. According to the text in Exercise 2, what is more damaging for one’s health? Why?

a. hot weather

b. high blood pressure

c. sweating

d. drinking alcoholic beverages

e. low blood pressure

f. physical exercise

g. vomiting

Exercise 5. Now read the article about water overdose.

Strange but True: Drinking Too Much Water Can Kill

In a hydration-obsessed culture, people can and do drink themselves to death.

By Coco Ballantyne

Liquid H₂O is the sine qua non of life. Making up about 66 percent of the human body, water runs through the blood, inhabits the cells, and lurks in the spaces between. At every moment water escapes the body through sweat, urination, or exhaled breath, among other routes. Replacing these lost stores is essential but rehydration can be overdone. There is such a thing as a fatal water overdose.

Earlier this year, a 28-year-old California woman died after competing in a radio station's on-air water-drinking contest. After downing some six liters of water in three hours in the contest, Jennifer Strange vomited, went home with a splitting headache, and died from so-called water intoxication. There are many other tragic examples of death by water. In 2005 a fraternity hazing at California State University, Chico, left a 21-year-old man dead after he was forced to drink excessive amounts of water between rounds of push-ups in a cold basement. Club-goers taking MDMA ("ecstasy") have died after consuming copious amounts of water trying to rehydrate following long nights of dancing and sweating. Going overboard in attempts to rehydrate is also common among endurance athletes. A 2005 study in the New England Journal of Medicine found that close to one sixth of marathon runners develop some degree of hyponatremia, or dilution of the blood caused by drinking too much water.

Hyponatremia, a word cobbled together from Latin and Greek roots, translates as "insufficient salt in the blood." Quantitatively speaking, it means having a blood sodium concentration below 135 millimoles per liter, or approximately 0.4 ounces per gallon, the normal concentration lying somewhere between 135 and 145 millimoles per liter. Severe cases of hyponatremia can lead to water intoxication, an illness whose symptoms include headache, fatigue, nausea, vomiting, frequent urination and mental disorientation.

In humans the kidneys control the amount of water, salts and other solutes leaving the body by sieving blood through their millions of twisted tubules. When a person drinks too much water in a short period of time, the kidneys cannot flush it out fast enough and the blood becomes waterlogged. Drawn to regions where the concentration of salt and other dissolved substances is higher, excess water leaves the blood and ultimately enters the cells, which swell like balloons to accommodate it.

Most cells have room to stretch because they are embedded in flexible tissues such as fat and muscle, but this is not the case for neurons. Brain cells are tightly packaged inside a rigid boney cage, the skull, and they have to share this space with blood and cerebrospinal fluid, explains Wolfgang Liedtke, a clinical neuroscientist at Duke University Medical Center. "Inside the skull there is almost zero room to expand and swell," he says. Thus, brain edema, or swelling, can be disastrous. "Rapid and severe hyponatremia causes entry of water into brain cells leading to brain swelling, which manifests as seizures, coma, respiratory arrest, brain stem herniation and death," explains M. Amin Arnaout, chief of nephrology at Massachusetts General Hospital and Harvard Medical School.

Where did people get the idea that guzzling enormous quantities of water is healthful? A few years ago Heinz Valtin, a kidney specialist from Dartmouth Medical School, decided to determine if the common advice to drink eight, eight-ounce glasses of water per day could hold up to scientific scrutiny. After scouring the peer-reviewed literature, Valtin concluded that no scientific studies support the "eight x eight" dictum (for healthy adults living in temperate climates and doing mild exercise). In fact, drinking this much or more "could be harmful, both in precipitating potentially dangerous hyponatremia and exposure to pollutants, and also in making many people feel guilty for not drinking enough," he wrote in his 2002 review for the American Journal of Physiology—Regulatory, Integrative and Comparative Physiology. And since he published his findings, Valtin says, "not a single scientific report published in a peer-reviewed publication has proven the contrary."

Most cases of water poisoning do not result from simply drinking too much water, says Joseph Verbalis, chairman of medicine at Georgetown University Medical Center. It is usually a combination of excessive fluid intake and increased secretion of vasopressin (also called antidiuretic hormone), he explains. Produced by the hypothalamus and secreted into the bloodstream by the posterior pituitary gland, vasopressin instructs the kidneys to conserve water. Its secretion increases in periods of physical stress—during a marathon, for example—and may cause the body to conserve water even if a person is drinking excessive quantities.

Every hour, a healthy kidney at rest can excrete 800 to 1,000 milliliters, or 0.21 to 0.26 gallon, of water and therefore a person can drink water at a rate of 800 to 1,000 milliliters per hour without experiencing a net gain in water, Verbalis explains. If that same person is running a marathon, however, the stress of the situation will increase vasopressin levels, reducing the kidney's excretion capacity to as low as 100 milliliters per hour. Drinking 800 to 1,000 milliliters of water per hour under these conditions can potentially lead to a net gain in water, even with considerable sweating, he says.

While exercising, "you should balance what you're drinking with what you're sweating," and that includes sports drinks, which can also cause hyponatremia when consumed in excess, Verbalis advises. "If you're sweating 500 milliliters per hour, that is what you should be drinking." But measuring sweat output is not easy. How can a marathon runner, or any person, determine how much water to consume? As long as you are healthy and equipped with a thirst barometer unimpaired by old age or mind-altering drugs, follow Verbalis's advice, "drink to your thirst. It's the best indicator." (From Scientific American Online, June 21, 2007)

Exercise 6. Are the following statements true or false, according to the text? Why? Explain your choice.

1. Water is the basic substance in the human organism.

2. Drinking excessive amounts of water can lead to death.

3. Hyponatremia is a Latin word which means “water overdose”.

4. Hyponatremia is a serious disorder characteristic for sportsmen.

5. Liver filters water and plays the key role in excreting wastes.

6. Excessive amounts of water are particularly damaging for the brain.

7. A considerable body of evidence confirms the advice to drink much.

8. Excessive water intake combined with physical exercise may result in serious health problems.

9. It’s not recommended to drink while exercising.

Exercise 7. These sentences all give very good advice, but they have been divided into separate halves. Match the half-sentences in Column A with the half-sentences in Column B to make 14 sentences which are correct, complete and true.

Write five other pieces of advice for healthy life.

A 1. Regular exercise is... 2. A balanced diet should... 3. Medicines should... 4. A patient in shock should... 5. Not taking any exercise is... 6. Reading in bad light can... 7. You should do... 8. A normal adult should drink... 9. HIV can be transmitted... 10. Bad posture can... 11. People with fair complexions... 12. Surgical instruments must... 13. Babies should... 14. Hemorrhage control routinely should...

В a)... burn easily in the sun. b)... cause back pain. c)... be inoculated against diphtheria. d)... be kept out of the reach of children. e)... be kept warm and lying down. f)... about 2.5 litres of fluid each day. g)... good for the heart. h)... five minutes' exercise every morning. i)... be sterilised before use. j)... make the eyes ache. k)... provide all the nutrients needed, in the correct proportions. l)... an unhealthy way of living. m)... be by pressure and elevation. n)... by using non-sterile needles

Exercise 8. Summarize everything you now know about significance and effects of water into one report.

Unit 3. Fungi

Every man carries a parasite somewhere.

Japanese proverb

Exercise 1. What do you know about fungi?

1. What is a fungus? Why are fungi classified into a separate Kingdom?

2. Are fungi unicellular or multicellular organisms?

3. Are fungi stationary or moving organisms?

4. What is the difference between a fungus and a mushroom? Do all fungi have a fruiting body?

5. Are fungi hetero- or autotrophs?

6. What ecological functions are performed by fungi?

7. What cases of symbiotic relationship between fungi and other organisms do you know? Give examples of mutualism and parasitism.

8. What is the significance of fungi for humans?

Exercise 2. Explain the following terms in English:

chitin yeast mold hypha (hyphae) mycelium

extracellular digestion saprophyte mutualist parasite haustoria

asexual reproduction sexual reproduction spore fragmentation budding

Exercise 3. Can you believe that fungi are the largest and fastest organisms on Earth? Why? Why not?

Read the following two texts (Text A and Text B) to find out.

Text A. The Largest Organism on Earth Is a Fungus

The blue whale is big, but nowhere near as huge as a sprawling fungus in eastern Oregon

By Anne Casselman

Next time you purchase white button mushrooms at the grocery store, just remember, they may be cute and bite-size but they have a relative out west that occupies some 2,384 acres (965 hectares) of soil in Oregon's Blue Mountains. Put another way, this humongous fungus would cover 1,665 football fields, or nearly four square miles (10 square kilometers) of turf. The discovery of this giant Armillaria ostoyae in 1998 heralded a new record holder for the title of the world's largest known organism, believed by most to be the 110-foot- (33.5-meter-) long, 200-ton blue whale. Based on its current growth rate, the fungus is estimated to be 2,400 years old but could be as ancient as 8,650 years, which would earn it a place among the oldest living organisms as well.

A team of forestry scientists discovered the giant after setting out to map the population of this pathogenic fungus in eastern Oregon. The team paired fungal samples in petri dishes to see if they fused, a sign that they were from the same genetic individual, and used DNA fingerprinting to determine where one individual fungus ended.

This one, A. ostoyae, causes Armillaria root disease, which kills swaths of conifers in many parts of the U.S. and Canada. The fungus primarily grows along tree roots via hyphae, fine filaments that mat together and excrete digestive enzymes. But Armillaria has the unique ability to extend rhizomorphs, flat shoestringlike structures, that bridge gaps between food sources and expand the fungus's sweeping perimeter ever more. A combination of good genes and a stable environment has allowed this particularly ginormous fungus to continue its creeping existence over the past millennia. "These are very strange organisms to our anthropocentric way of thinking," says biochemist Myron Smith of Carleton University in Ottawa, Ontario.

All fungi in the Armillaria genus are known as honey mushrooms, for the yellow-capped and sweet fruiting bodies they produce. Some varieties share this tendency for monstrosity but are more benign in nature. In fact the very first massive fungus discovered in 1992—a 37-acre (15-hectare) Armillaria bulbosa, which was later renamed Armillaria gallica —is annually celebrated at a "fungus fest" in the nearby town of Crystal Falls, Mich. Myron Smith was a PhD candidate in botany at the University of Toronto when he and colleagues discovered this exclusive fungus in the hardwood forests near Crystal Falls. "This was kind of a side project," Smith recalls. "We were looking at the boundaries of [fungal] individuals using genetic tests and the first year we didn't find the edge."

Next, the microbiologists developed a new way to tell an individual apart from a group of closely related siblings using a battery of molecular genetic techniques. The major test compared fungal genes for signs of inbreeding, where heterozygous strips of DNA become homozygous. That's when they realized they had struck it big. The individual Armillaria bulbosa they found weighed over 100 tons (90.7 metric tons) and was roughly 1,500 years old.

Ironically, the discovery of such huge fungi specimens rekindled the debate of what constitutes an individual organism. "It's one set of genetically identical cells that are in communication with one another that have a sort of common purpose or at least can coordinate themselves to do something," explains Tom Volk, a biology professor at the University of Wisconsin–La Crosse. Both the giant blue whale and the humongous fungus fit comfortably within this definition. So does the 6,615-ton (six-million-kilogram) colony of a male quaking aspen tree and his clones that covers 107 acres (43 hectares) of a Utah mountainside.

And, at second glance, even those button mushrooms aren't so tiny. A large mushroom farm can produce as much as one million pounds (454 metric tons) of them in a year. "The mushrooms that people grow in the mushroom houses - they're nearly genetically identical from one grower to another," Smith says. "So in a large mushroom-growing facility that would be a genetic individual—and it's massive!" In fact, humongous may be in the nature of things for a fungus. "We think that these things are not very rare," Volk says. "We think that they're in fact normal." (From Scientific American Online, October 4, 2007)

Text B. Seedy but Speedy: Fungus Spews Spores at 55 Mph

By Susannah F. Locke

In a finding that could help control harmful fungus, researchers have discovered a high-speed mechanism the germs use to project their spores into the air. Scientists from Miami University (M.U.) in Oxford, Ohio, and the College of Mount St. Joseph in Cincinnati report in the journal PLoS ONE that fungi may be one of the fastest land species, clocking speeds of up to 55 miles (88 kilometers) per hour and producing accelerations 180,000 times greater than gravity.

Fungi are the most common crop pathogens in the world. Most are fairly harmless to people, although like other allergens they sometimes exacerbate allergies and asthma. But certain varieties such as Stachybotrys chartarum, commonly referred to as black mold, that thrive in damp places like basements may also infect the lungs of people who have compromised immune systems or chronic bronchitis. Biologists once believed that mild air currents were enough to release fungi's spores, but are increasingly finding that molds employ elaborate methods to spew their seeds away from the nest. Using ultrahigh-speed video, the researchers calculated that some fungi use their own natural water pressure like squirt guns to eject their spores.

Lead study author Nicholas Money, a fungus biologist at M.U., studied fungi that grow on cow patties and other herbivore dung. These species play a critical role in the ecosystem by breaking down waste to recycle its nutrients into the soil. The fungi project their spores away from the resident dung because cows will not eat near feces. By shooting them up to eight feet (2.5 meters) away, a grazing animal will be more inclined to eat them, thereby spreading the fungal spawn via its own manure.

The research video camera shot 250,000 frames per second to capture fungi spurting their spores into the air, trailing glistening liquid behind them. The researchers used the video to clock the spores speeding along at 55 mph. The team also identified how several fungi build up water pressure to power a spore launch. First, the fungi accumulate sugars and other small molecules in their cells, which, in turn, brings in more water. Targeting the first step of this process could be a key to developing new fungicides. "By understanding the basic mechanism," he says, "you might find ways to remediate a mold-damaged home." (From Scientific American Online, September 17, 2008)

Exercise 4. Answer the following questions using the information from the texts:

1. What animal is generally considered the biggest organism on earth?

2. What extraordinary characteristics does the discovered Armillaria ostoyae fungus possess?

3. Why is Armillaria ostoyae characterized as a pathogenic fungus?

4. What conditions allowed the fungus to grow to such enormous size?

5. How can scientists distinguish an individual from a group of closely related siblings?

6. What effect do fungi produce on people and the environment?

7. What mechanisms does Stachybotrys chartarum black mold use to spurt its spores into the air?

8. Why do fungi have to employ such complicated techniques?

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