Task2. Fill in the gaps with appropriate articles, if necessary.

Most algae are … eukaryotes. … important organelle found in eukaryotic algae is … chloroplast, which contains … light-absorbing pigments responsible for capturing … energy in sunlight during … photosynthesis. In … most algae … primary pigment is … chlorophyll, … same green pigment used in … plants.

Like plants, most algae have … rigid cell walls composed largely of … cellulose. … exception is … diatom, whose cell wall is composed primarily of … silica. Many eukaryotic algae have … whiplike appendages called flagella attached to … their cell walls. By beating flagella in … rotary movement, these algae are able to move through … water with considerable speed. A few algae that are devoid of … rigid cell walls are able to protrude … one part of … body ahead of … other to crawl on … solid surfaces in … amoeba-like fashion.

Task3. These are the answers. Write questions.

1. A higher level of organization known as tissues.

2. The largest and most conspicuous organelle.

3. It is regulated by the plasma membrane.

4. They absorb the nutrients in food through the plasma membrane.

5. Some single-celled eukaryotes, such as amoebas.

6. About 3.5 billion to 3.8 billion years before present.

Task4. Change the sentences using for + noun (pronoun) + infinitive. See the model.

Example: I cannot understand his pronunciation. – It is difficult for me to understand his pronunciation.

1. She cannot come to me tomorrow.

2. 2. We cannot accept your invitation.

3. I can read your articles easily. I study a similar problem.

4. You must read more scientific writing to keep abreast with the modern thought.

5. Scientists are interested in the origin of life on Earth.

Task5. Find mistakes in these sentences.

1. The complexity of eukaryotic cells are reflected in their size.

2. Eukaryotes house an assortment of structures, calling organelles, within the cytoplasm.

3. Plants, seaweeds, and microscopic algae are specializing eukaryotes that carry out photosynthesis.

4. Most eukaryotic cells divide with mitosis, a process that produces two cells with the same genetic information.

5. Eukaryotes evolved much later prokaryotes, whose origins date to about 3.5 billion to 3.8 billion years before present.

6. Eukaryotic cells are thought to have been evolved from primitive prokaryotes.

Task6. Render the following text into English.

Дрожжи – одноклеточные эукариотные микроорганизмы. Наиболее распространенный способ размножения дрожжей – почкование. Дрожжи являются аэробами со сформированным аппаратом дыхания, но в анаэробных условиях получают энергию за счет субстратного фосфорилирования. Конструктивный метаболизм дрожжей основан на их хорошо развитых биосинтетических способностях. Есть виды дрожжей, развивающиеся на простых синтетических средах; эти дрожжи способны синтезировать все необходимые им сложные органические соединения. Добавление к питательной среде веществ, содержащих комплекс витаминов, аминокислот, сахаров приводит к заметному стимулированию роста дрожжей.

Существует ряд отраслей промышленности, основанных на жизнедеятельности дрожжей. Сбраживание дрожжами виноградного сока лежит в основе виноделия, сбраживание пивного сусла специальными пивными дрожжами – в основе пивоварения. Дрожжи незаменимы также в производстве спирта и в хлебопекарном производстве.

ADDITIONAL TEXT

Task1. Read the text about the giant squid, up to 18 m (60 ft) long, which is one of earth’s most mysterious creatures. As of 1997, scientists had never seen one in its native habitat. Clues to the giant squid’s strange love life only add to the intrigue.

Scientists Discover New Clues About Squids’ Mating Habits

Scientists in Australia have discovered evidence that may help explain the mating behavior of the giant squid, a solitary and mysterious creature about which little is known, according to an October 16, 1997, report in the journal Nature.

Zoologists Mark D. Norman and Chung Cheng Lu of the University of Melbourne believe the male giant squid mates with a female by using its muscular penis to deposit sperm into a shallow wound beneath the skin of its female partner. The scientists theorized that the sperm, contained in capsules called spermatophores, is injected into the female’s skin “potentially under hydraulic pressure,” suggesting that the male reproductive organ functions something like a syringe.

The females of several smaller species of squid are known to store sperm in healed wounds under their skin. But scientists believe the wounds are made by the male squid’s beaklike mouth and are then filled with spermatophores. The mating behavior of the giant squid, which can grow to 18 m (60 ft) and weigh 2000 kg (4400 lb), is thought to be unique.

The discovery was reported after Norman and Lu examined a female giant squid 15 m (50 ft) long captured off the coast of southern Australia by a commercial fishing trawler. Spermatophores, several centimeters long and filled with millions of sperm, were found deposited in a small wound in one of the giant squid’s forward arms. On another forward arm, more spermatophores were found under a patch of torn skin, suggesting “deliberate placement,” the scientists said.

The scientists speculated that female giant squid may stockpile the sperm for long periods, an adaptation to a dark world where “encounters with male giant squid are infrequent.” Scientists believe giant squid live mainly at depths of 300 to 600 m (985 to 1970 ft), where sunlight does not penetrate. It is unknown how the female uses the sperm to fertilize her eggs.

Source: Nature, 1997

Task2. Make a report on the basis of this article.

Task3. Read the article about the phenomenon called the red tide which in many cases presents a health hazard and causes extensive fish kills.

High Tide for Red Tide

A toxic strain of red tide in the Strait of Magellan, located off the coast of Punta Arenas, Chile, has led to 15 deaths and hundreds of hospitalizations, and has virtually shut down the once booming commercial fishing industry and the unrestricted harvesting of shellfish in the region. According to scientists, the Chilean experience is far from unique. Over the last two decades, red tides have been increasing worldwide. The phenomenon, can devastate a country's fishing and tourism industries.

Red tides result from a massive buildup of certain species of the microscopic sea organisms known as phytoplankton. Some of these tiny plankton organisms produce compounds that are toxic to fish that feed on them. In addition, the toxins accumulate in filter-feeding shellfish, such as clams, mussels, and oysters. The shellfish themselves are rarely affected by the toxins, but the poison can persist in their tissue for years and can be passed along to people who eat the contaminated shellfish. Of the more than one thousand species of phytoplankton, only about two dozen are toxic. Heavy concentrations of both toxic and nontoxic phytoplankton blooms can lend a reddish-brown tint to the surrounding water, but contamination can occur even without visible discoloration.

Different species of phytoplankton produce different types and combinations of toxins that build up in shellfish. People who eat the contaminated seafood can fall victim to various kinds of shellfish poisoning, depending on which poisons have accumulated. The most common types of shellfish poisoning are diarrhetic, paralytic, and neurotoxic. Diarrhetic poisoning affects the digestive system, causing diarrhea, vomiting, and nausea. Paralytic and neurotoxic types of poisoning attack the nervous system, causing a tingling or numbing sensation around the lips and tongue. At high levels, the paralytic toxins can lead to respiratory failure and death. The casualties of Chile's red tide suffered acute cases of paralytic shellfish poisoning.

Red tides, which usually bloom in spring and summer and can last from a few hours to several months, have been known for centuries. In recent years, however, the phenomenon, especially the toxic kind, has spread rapidly to harbors around the world. Since the 1970s, toxic red tides have been reported off the coasts of the United States, Sweden, Norway, Spain, Japan, and China. The tides are showing up in places where previously they had never been reported, and new types of organisms are being identified. Scientists do not know exactly what causes red tides, but they think rising pollution levels, natural changes in the environment, and climate may play a role in the increased incidence. Some scientists, however, caution against assuming the existence of a global epidemic of red tides. These scientists note that the apparent increase could be the result of using technologically advanced monitoring equipment and increased scientific awareness.

Scientists do know that red tide blooms occur in nutrient-rich waters that receive abundant sunlight. Under these conditions, phytoplankton rapidly multiply through a process of asexual reproduction. Many of the toxic species of phytoplankton depend on the nutrients nitrogen and phosphorous for growth. Wastewater runoff and other forms of coastal pollution contain an abundance of both elements and other nutrients favorable to plant growth. Although scientists have not proved conclusively that the increasing number of red tides worldwide is directly linked to rising pollution levels, studies strongly suggest a relationship.

In the absence of sunlight and nutrients, some species of phytoplankton are able to become thick-walled, dormant cells, known as cysts, that can survive for years on the ocean floor. When favorable growth conditions return, these dormant cells become swimming cells that can take advantage of the new conditions to produce a bloom. According to scientists, cysts account for the recurring and often perennial nature of red tides. A huge toxic red tide that stretched from the coast of Maine to Massachusetts appeared for the first time following a 1972 hurricane. Every year since, red tides have reappeared in the region.

Scientists believe that cysts, stirred up and swept along by ocean currents, are one of the ways by which red tides can appear in previously unaffected waters. In addition, as blooms of phytoplankton move with currents, they can leave a trail of cysts that will eventually bloom under favorable conditions. Ships carrying phytoplankton or cysts in their ballast water can introduce the organisms to a new region when they empty their ballast tanks at ports.

The amount of destruction caused by toxic red tides varies. In industrialized countries, where monitoring systems are more advanced, it is rare for human beings to become sick or die from shellfish poisoning. Instances of people suffering from illness and death as a result of toxic blooms are much higher in developing countries, especially those with long coastlines where seafood is a dietary staple.

Industrialized countries, however, are not immune to the consequences of red tides. Piles of fish killed by a toxic strain of red tide in the Gulf of Mexico have been washing up on Florida's shores for more than a century. The massive fish kills have caused millions of dollars worth of damage to the state's tourism industry. In 1987, 14 dead humpback whales washed ashore in Cape Cod Bay, Massachusetts. Scientists discovered that the whales had died as a result of feeding on mackerel that had ingested marine organisms that had, in turn, eaten a toxic strain of phytoplankton. The toxins became more concentrated at each step up the food chain, until they reached lethal levels in the humpbacks.

While industrialized countries are adept at monitoring red tides, they have not yet discovered a way to neutralize the harmful effects or to eradicate the toxic algae blooms. In addition, many scientists view the blooms as a natural part of the ocean environment and are reluctant to interfere with a phenomenon whose role in the ecosystem remains unclear. Countries around the world are forced to wait for the blooms to disappear and hope that, in the meantime, people heed official warnings against harvesting shellfish in affected areas.

Source: Encarta Yearbook, August 1995.

Task4. Make a report on the basis of this text.

UNIT II

PROKARYOTIC CELL

Task1. Read the text about prokaryotes and give their brief description.

Prokaryote is a relatively simple unicellular organism lacking a nucleus and other features found in the more complex cells of all other organisms, called eukaryotes. In 1938 American biologist Herbert Copeland proposed that unicellular organisms lacking nuclei be classified in their own kingdom, Monera, also called Kingdom Prokaryotae. All bacteria were categorized in this newly established kingdom. This scheme was the first to establish separate kingdoms for prokaryotes (organisms without nuclei) and eukaryotes (organisms with nuclei).

In 1990 American microbiologist Carl Woese proposed that bacteria be divided into two groups, the archaea, or archaebacteria, and bacteria, based on their structural and physiological differences. In some classification systems, the archaea are considered prokaryotes; in others, they are classified in their own domain, the archaea. Archaebacteria consist of a small group of primitive anaerobes (organisms that do not require oxygen). They are found in a narrow range of habitats—often in extreme environments with high temperature, high salt, or high acidity. In contrast, bacteria live in a wide range of environments with or without oxygen, at various temperatures, and at various levels of acidity.

Task2. Answer the question: what is the difference between archaebacteria and bacteria?

Task3. Read and translate the text about the structure of a prokaryotic cell.

  Prokaryotic cells are relatively small, ranging in size from 0.0001 to 0.003 mm (0.000004 to 0.0001 in) in diameter. With the exception of a few species, prokaryotic cells are surrounded by a protective cell wall. The cell walls of archaebacteria and bacteria contain forms of peptidoglycan, a protein-sugar molecule not present in the cell walls of fungi, plants, and certain other eukaryotes. The archaebacteria cell wall has a more diverse chemical composition than the cell wall of bacteria.

Just inside the cell wall of prokaryotes is the plasma membrane, a thin structure that is both flexible and strong. In both prokaryotes and eukaryotes, the plasma membrane is composed of two layers of phospholipid molecules interspersed with proteins, and regulates the traffic that flows in and out of the cell. The prokaryotic plasma membrane, however, carries out additional functions. It participates in replication of deoxyribonucleic acid (DNA) for cell division and synthesis of adenosine triphosphate (ATP), an energy molecule. In some prokaryotes, the plasma membrane is essential for photosynthesis, the process that uses light energy to convert carbon dioxide and water to glucose.

In the interior of the prokaryotic cell is the cytoplasm, a watery fluid that is rich in dissolved salts, nutrients, enzymes, and other molecules. The great majority of the cell’s biochemical reactions, which number in the thousands, take place within the cytoplasm. Prokaryotic cells typically have a single molecule of DNA in a closed loop floating free in a region of the cytoplasm called the nucleoid. Many species of prokaryotes also contain DNA in tiny ringlets known as plasmids in the cytoplasm.

Ribosomes, tiny bead-like structures that manufacture proteins, are also located in the cytoplasm. The ribonucleic acid (RNA) in the ribosomes differs significantly between the archaebacteria and bacteria. With the exception of the ribosomes, prokaryotes lack organelles (specialized structures such as the nucleus, chloroplasts, mitochondria, lysosomes, and Golgi apparatus), which are present in eukaryotes. Some photosynthetic archaebacteria and bacteria have internal membranes, extensions of the plasma membrane known as chromatophores or thylakoids, which contain the pigments for photosynthesis.

Some species of prokaryotes form endospores, thick-walled, dehydrated structures that can resist extreme dryness and very high temperatures for long periods of time. Anthrax, tetanus, and botulism are diseases caused by endospore-forming bacteria.

Certain prokaryotes move independently by using flagella, long structures that rotate in a propeller-like fashion. Prokaryotic flagella consist of intertwined fibrils (small fibers) of the protein flagellin. A prokaryote may have a single flagellum, a group of flagella at one or both poles of the cell, or may be covered with flagella. Many species of prokaryotes also have pili (singular, pilus)—slender, hairlike extensions used for attachment to soil, rocks, teeth, or other structures.

Task4. Fill in the table:

Organelle	Characteristics	Functions

Task5. Answer the question: is there much difference between eukaryotic and prokaryotic cells? Why do you think so?

Task6. Read the text about reproduction of prokaryotes and describe the process.

Most prokaryotes multiply by the asexual process of binary fission, in which the DNA replicates in the cytoplasm and one DNA molecule passes to each newly formed cell. In addition, some prokaryotes undergo various processes of genetic recombination. For example, in the process called transformation, bacteria remove genes from the DNA released into the environment from the remains of dead cells, and incorporate the genes into their chromosome. In conjugation, genes pass from a donor bacterium to a recipient bacterium. In transduction, a virus transports bacterial genes from one cell to the next. Gene transfers account for the appearance of new biochemical traits.