V. Read the following text and answer the questions in the Discusion section



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ЗНАЕТЕ ЛИ ВЫ?

V. Read the following text and answer the questions in the Discusion section



SHOULD WE DESTROY THE LAST SMALLPOX VIRUS?

In two freezers, one at the Center for Disease Control and Prevention in Atlanta and another at the Research Institute for Viral Preparations in Moscow, lie the last smallpox viruses on the planet. Infectious disease experts and virologists are debating whether or not to destroy the remaining smallpox virus, called Variola.

Smallpox is the deadliest infectious disease known to strike humans, in terms of numbers of people killed. Smallpox ravaged the Roman Empire and enabled the Spaniards to defeat the Aztecs in Mexico, whose immune systems could not handle the foreign virus. Survivors of smallpox often are left with severe scars. Luckiest were those few individuals who had mild cases and were left with relatively smooth skin plus immunity against reinfection.

English physician Edward Jenner's invention of the first vaccine in 1796, against Variola, was the beginning of the end of the scourge. It took many decades before the vaccine was improved and distributed widely enough to impact upon the dis­ease's prevalence. By 1967, when the World Health Organization (WHO) began its eradication campaign, some 10 million people in 40 nations still contracted smallpox each year.

The WHO campaign was remarkably successful, and in October 1977, the last victim in the general population, a Somali man, died of smallpox. A year later, though, a shocking case prompted public health officials and scientists to question the wisdom of maintaining samples of the virus. A photographer, Janet Parker, acquired smallpox while visiting a laboratory in England that kept the virus, obviously not sufficiently contained. Parker developed smallpox and died. The head of the laboratory, overcome with guilt, killed himself.

In 1979, the world was declared free of smallpox. The Global Commission for the Certification of Smallpox Eradication formed and requested that all Variola samples be destroyed or sent to appropriate facilities. In 1986, WHO raised the idea of destroying all samples, if the scientific and public health communities approved. In 1990, scientists request that the decision be postponed until they could learn the virus’s DNA sequence, so that they could continue to study it. Researches in the United States and the former Soviet Union collaborated and sequenced all 200,000 DNA bases that constitute Variola virus by 1993.

The remaining Variola samples are tentatively scheduled to be destroyed in the following years, though the debate over their fate continues. The "destroy" arguments tend to be political and practical; the "do not destroy" arguments are scientific in tone. The reasoning is as follows:

Destroy!

1. A terrorist could use the stored virus for biological warfare.

2. Damage to the freezers storing the virus — such as from a bomb, earthquake, or other disaster —could unleash a deadly smallpox epidemic.

3. Knowledge of the DNA sequence of Variola will enable researchers to continue studying the virus, without needing the actual virus.

Do Not Destroy!

1. Learning how the smallpox virus evades the human immune system will provide clues on how to combat HIV. Both Variola and HIV seem to infect only humans, and in many cases they defeat the human immune system.

2. Knowing the DNA sequence of a virus is not sufficient to understand how it causes symptoms and evades the immune system.

3. Viral infections reemerge. Should a new virus evolve to fit the niche that Variola occupied, or an existing virus (such as monkeypox) expand and change to affect humans, the lack of supplies of smallpox virus could hamper research.

4. Smallpox could reappear even if we destroy the frozen samples. Variola may have been stored in other laboratories, and smallpox victims buried in Soviet permafrost could some day thaw and release active virus.

A final note is more philosophical. Even though a virus is not technically alive, do we have the right to destroy it? In the words of one researcher, "It's taken millions of years for nature to make the Variola virus, and why should 10 guys sitting around a table say: 'Let's destroy it'?"

Discussion

1. What is smallpox?

2. When did mankind free itself from the scourge?

3. Is it safe to store a virus like that in laboratories?

4. What is your answer to the question: “Should we destroy the last smallpox virus?”?

VI. Solve the following crossword puzzle using the clues below

Across:

1a kingdom of unicellular, colonial, or multicellular organisms usually including the protozoans and most algae; 3 a preparation of killed microorganisms, living attenuated organisms, or living fully virulent organisms that is administered to produce or artificially increase immunity to a particular disease; 4 a kingdom of prokaryotic unicellular round, spiral, or rod-shaped single-celled microorganisms that are often aggregated into colonies or motile by means of flagella, that live in soil, water, organic matter, or the bodies of plants and animals; 6a category of taxonomic classification ranking above the family and below the class; 9 a category of biological classification ranking between the family and the species, comprising structurally or phylogenetically related species; 12 a major category in biological taxonomy ranking above the order and below the phylum or division; 13 a group that constitutes one of the usually primary divisions of the animal kingdom; 14 an organism that lives in the absence of free oxygen; 15 an organism capable of performing life functions only in the presence of oxygen; 16 a group of related plants or animals forming a category ranking above a genus and below an order and usually comprising several to many genera; 17 a category of biological classification ranking immediately below the genus or subgenus, comprising related organisms or populations potentially capable of interbreeding.

Down:

1a protein particle that lacks nucleic acid and is believed to be the cause of various infectious diseases of the nervous system; 2 an organism living together with another dissimilar organism in a mutually beneficial relationship; 3 a complete virus particle that consists of an RNA or DNA core with a protein coat sometimes with external envelopes and that is the extracellular infective form of a virus; 5 any of a major group of saprophytic and parasitic spore-producing organisms usually classified as plants that lack chlorophyll and include molds, rusts, mildews, smuts, mushrooms, and yeasts; 7 an organism living in, with, or on another organism and obtaining benefits from the host which it usually injures; 8 the DNA-containing area of a prokaryotic cell; 10 an organism living on dead or decaying organic matter; 11 any of various enzymes that promote hydrolysis of nucleic acids.

 

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VII. Using additional sources of information prepare a report on one of the following topics and present it to the class

  • Modern views on the problems of taxonomy and systematics in biology.
  • The role of bacteria in ecology and in human lives.
  • Modern virology. Recent investigations and discoveries.

 


Unit 4

Lesson 1

VASCULAR PLANTS

PRE-READING TASKS

I. Answer the following questions

· What do you associate a plant with?

· What features distinguishing plants from other living organisms can you name?

· What part do plants play in ecology?

II. Listen to the following words and practice their pronunciation

Vascular plant, xylem, phloem, fern, gymnosperm, angiosperm, conifer, monocot, dicot, taproot, fibrous root, meristem, lateral bud, internode, petiole, axil, axillary bud, leaf primordia, protoderm, epidermis, procambium, cuticle, pith, cortex.

READING COMPREHENSION AND VOCABULARY DEVELOPMENT



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