Task3. Choose between Participle I and Participle II .

1. Prokaryotic cells are relatively small, (to range) in size from 0.0001 to 0.003 mm (0.000004 to 0.0001 in) in diameter.

2. Photoautotrophs, (to include) the cyanobacteria, and the green sulfur and purple sulfur archaebacteria, derive their energy from light.

3. Early bacteria were the cyanobacteria, formerly (to know) as blue green algae.

4. Cyanobacteria are the foundation for aquatic ecosystems, (to provide) food for protozoa and other aquatic organisms.

5. Mild cyanobacteria toxins in lakes and oceans cause a rash (to know) as swimmer’s itch, while powerful neuromuscular toxins (to release) by other cyanobacteria can kill fish (to live) in the water or the animals that drink the water.

Task4. Find a mistake.

1. In both prokaryotes and eukaryotes, the plasma membrane is composed from two layers of phospholipid molecules interspersed with proteins.

2. Prokaryotes, like all organisms, should build complex molecules from simple molecules.

3. The environment of the archaebacteria lacked in free oxygen, which did not accumulate in the atmosphere or water.

4. Cyanobacteria color varies such as blue-green and red or purple and is determined by the proportions of two secondary pigments.

5. Certain bacteria, included the soil bacteria Actinomycetes, produce antibiotics.

Task5. Fill in the gaps with appropriate articles.

1. Archaebacteria consist of … small group of primitive … anaerobes that do not require … oxygen.

2. Certain prokaryotes move independently by using … flagella, … long structures that rotate in … propeller-like fashion.

3. Most prokaryotes multiply by … asexual process of … binary fission, in which … DNA replicates in … cytoplasm.

4. Heterotrophs are … organisms that rely on … ready-made organic compounds such as … glucose or… alcohol for their carbon source.

5. … photosynthesis occurring in … cyanobacteria still contributes substantial amounts of … oxygen to … atmosphere.

6. While higher plants have … two kinds of … chlorophyll, called a and b, cyanobacteria contain only … chlorophyll a.

Task6. Render the following text into English.

^{Для прокариот характерна способность существовать в гораздо большем диапазоне условий внешней среды, чем для эукариотных организмов. Среди прокариот есть организмы, которые могут расти в подводных вулканических источниках (температура до 300С), кислой (рH 1 и ниже) и щелочной (рH 11 и выше) среде, при давлении 1000 атмосфер, высоких концентрациях тяжелых металлов, высоких уровнях радиации. Обязательным условием для этого является наличие водной среды. Прокариоты не могут расти в аэрозолях и во льду. Отношение к молекулярному кислороду у прокариот различно. По этому признаку они делятся на несколько групп. Прокариоты, для роста которых кислород необходим, называют облигатными аэробами. К ним относится большинство прокариотных организмов. Известны прокариоты, для метаболизма которых кислород не нужен, то есть конструктивные и энергетические процессы у них происходят без участия молекулярного кислорода. Такие организмы получили название облигатных анаэробов.}

^{Описаны прокариотные организмы, которые могут расти как в аэробных, так и в анаэробных условиях. Такие организмы получили название факультативных аэробов, или факультативных анаэробов. Представителями этой физиологической группы прокариот являются энтеробактерии.}

^{ADDITIONAL TEXT}

Task1. Read this article about the earliest creatures on Earth.

Fossil: Evidence Points to Early Life Forming on Deep-Ocean Floor

June 2000

An Australian geologist has reported finding fossil evidence for the existence of heat-loving microorganisms that lived near submarine hot springs about 3.2 billion years ago, some 2.7 billion years earlier than previously believed. The microbes lived under extreme conditions of heat and darkness near volcanic vents on the deep-ocean floor where sunlight could not penetrate.

The researcher’s findings could lend support to the theory that life on Earth first originated on the deep-ocean floor in extreme heat, rather than in warm pools of water on the surface of Earth as many scientists have long conjectured. According to this theory, the earliest creatures derived their energy through a process known as chemosynthesis by metabolizing inorganic chemicals such as sulfur, rather through the process of photosynthesis, which converts sunlight into energy.

Geologist Birger Rasmussen of the University of Western Australia in Nedlands reported the discovery in a letter in the June 8, 2000, issue of the journal Nature. Rasmussen described finding threadlike microorganisms in a volcanogenic massive sulphide, a type of metal deposit of volcanic origin that is usually formed on the seafloor, in a region known as the Pilbara Craton in northwest Australia. The volcanic rock deposits in this region date from the Archean Eon, a period that lasted from 3.8 billion years ago to 2.5 billion years ago. The Pilbara Craton region and a rock formation in South Africa are the only two places in the world where rocks from the Archean Eon are known to have preserved fossils.

The fossilized filaments were 1 to 20 mm (0.04 to 0.8 in) in length and only a thousandth of a millimeter in diameter. Rasmussen based his finding of a biological origin on the filaments’ wavy form, uniformity in length, and similarity to other known fossils of microorganisms from the Archean Eon. He also found that the filaments were completely dissimilar to threadlike structures that are known to be of nonbiological origin.

By analyzing the chemical composition of the rock in which the microfossils were found, Rasmussen concluded that the ancient microbes inhabited a world where the temperature was near 100°C (212°F). This temperature is similar to that near hydrothermal vents (hot springs) found today on the floor of the Pacific and Atlantic oceans. Rasmussen noted other similarities between the fossilized microbes and the microorganisms that live near present-day hydrothermal vents and derive their energy from chemosynthesis. Scientists first discovered these vents in 1995 and were amazed to find a diverse marine community living under such extreme conditions.

In a commentary in Nature on Rasmussen’s article, geologist Euan Nisbet of the University of London in England wrote that “although Rasmussen’s work does not show that deep-water hydrothermal life came before photosynthetic life, it does lend circumstantial support to the argument that steps in the early history of life took place around hydrothermal systems.”

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

UNIT III

PROTISTA

Task1. Read and translate the text about protists.

Protista, group of comparatively simple organisms, called protists, that have characteristics of both plants and animals. Most protists are unicellular (consisting of a single cell) and can only be seen with a microscope, although there are some that are composed of more than one cell. There are a wide variety of protists, and they inhabit many different environments—fresh water, seawater, soils, and the intestinal tracts of animals, where they perform crucial digestive processes. Like plants, many species of protists can make their own food by the process of photosynthesis. Like animals, many protists can move around under their own power. Unlike plants and animals, however, protists do not have cells organized into specialized tissues.

The protists include such familiar organisms as seaweeds, amoebas, and slime molds. The kingdom Protista contains many economically important members, including organisms that cause diseases, such as malaria. Biologists theorize that members of the kingdom Protista gave rise to the kingdoms Plantae, Animalia, and Fungi about 600 million years ago.

All protists are eukaryotes. This means that their cells contain a nucleus, a membrane-bounded structure that encloses the cell’s genetic material. (Organisms without nuclei—the bacteria and cyanobacteria, or blue-green algae—are called prokaryotes.) Although most protists have a single nucleus, protists are unique in that some contain multiple nuclei—up to ten thousand in a single cell—and others, such as ciliates, have two different-sized nuclei in a single cell. The deoxyribonucleic acid (DNA) of protists (like that of other eukaryotes) is organized in long molecules called chromosomes within the nucleus. When the cell divides, these chromosomes replicate (duplicate themselves) and then divide in a process called mitosis. Among some protists, the nuclear membrane (the thin layer around the nucleus) stays intact during mitosis, whereas in plants, animals, and fungi the nuclear membrane breaks down.

Protists vary greatly in size and shape. Many are minute: The green alga Nanochlorum is only 0.01 mm (0.0004 in) long. Giant kelps can grow to 65 m (210 ft) or more in length.

Some protists form structures known as spores that are resistant to chemicals and drying and that disperse in the environment. Spores are often the infectious stage of organisms that cause diseases in humans when ingested.

Task2. Answer the questions.

1. What characteristics of plants and animals do protists have?

2. What environments do they inhabit?

3. What organisms do protists include?

4. What makes some protists unique?

5. What is the average size of protists?

6. What structures do some protests form?

Task3. Fill in the necessary words.

1. Most protists are … and can only be seen with a microscope.

2. Protists inhabit many different environments—…, …, …, and … .

3. The kingdom Protista includs organisms that cause diseases, such as … .

4. Most protists have a … nucleus, but some contain … nuclei.

5. The deoxyribonucleic acid (DNA) of protists is organized in long molecules called … .

6. When the cell divides, chromosomes … and then divide in a process called … .

7. Spores are often the … stage of organisms that cause … in humans.

Task4. Are these sentences right or wrong? Explain your point of view.

1. Most protists are multicellular organisms, although there are some that are composed of only one cell.

2. Some protists inhabit the intestinal tracts of animals and people, where they perform crucial digestive processes.

3. Members of the kingdom Protista gave rise to the kingdoms Plantae, Animalia, and Fungi about 600 million years ago.

4. Some protists are eukaryotes and some are prokaryotes.

5. The nuclear membrane is a thick layer around the nucleus.

6. All protists are of the same size and shape.

Task5. Sum up the information about protists.

Task6. Read the text about anatomy and physiology of protists.

 Most protists contain many mitochondria, membrane-bounded organelles (cellular parts) that break down complex organic molecules and, in the process, release the chemical energy that powers the rest of the cell. The physiology of these protists is very similar to the cellular physiology of plants, animals, and fungi. Mitochondria require oxygen. Protists that live in environments without oxygen—for instance, in black muds or inside the digestive tract of animals—generally do not have mitochondria, and they create cellular energy by processes unique to the kingdom Protista.

In addition to mitochondria and nuclei, membrane-bounded organelles called plastids are found in protists that perform photosynthesis. Plastids capture the energy of sunlight and convert the energy into a chemical form available for use in the cell. Plastids are also able to capture inorganic carbon dioxide from the atmosphere and turn it into organic carbon useful for cell growth. Pigments, including chlorophyll, synthesized within plastids capture the sunlight and give photosynthetic protists their distinct colors: The brown algae contain brown plastids; the green algae, green plastids; and the red algae, red plastids.

In all likelihood, plastids and mitochondria were once free-living bacteria that became organelles through the process of symbiosis (an intimate and ongoing association of two or more different species). Once controversial, the theory of the symbiotic origin of plastids and mitochondria is generally accepted today. DNA molecules within present-day plastids and mitochondria are probably relics of the DNA of free-living bacteria ancestors.

Some protists are capable of movement. Protists known as flagellates move by means of flagella, long whiplike structures that the protists beat to propel themselves through water. Other protists use numerous and comparatively short structures called cilia. One group of protists, the ciliates, is distinguished by the great number and unusual arrangement of cilia along their surface. The single-celled amoebas and their multicellular relatives the slime molds are protists that use pseudopodia, temporary protrusions of the cell, both for movement and to engulf prey.

The vast majority of protists reproduce asexually—cells simply grow and divide. Sexual recombination (the production of gametes and the merging of DNA from two individuals to form a zygote) has been observed in some protists. However, many protists have been only poorly studied.

Task7. Fill in the table.

Group of protists	Organelles they possess	Functions of organelles

Task8. Speak about anatomy and physiology of protists.

Task9. Read the text about classification of protists.

 The first detailed descriptions of protists were made in 1676 by the inventor of the microscope, Dutch naturalist Antoni van Leeuwenhoek, who observed microscopic organisms that he called animalcules. Traditionally all organisms that moved had been considered animals, whereas all photosynthetic organisms had been considered plants. The term Protista was first used in 1862 by the German biologist Ernst Haeckel to describe microscopic organisms that were neither clearly animallike nor plantlike. Haeckel recognized that some organisms are both motile and photosynthetic. For almost a hundred years after Haeckel, scientists informally recognized three kingdoms: plants, animals, and protists. The Protista included all the microbes. In the 1930s, it was formally proposed that all single-celled organisms, including bacteria, be placed in their own kingdom, Kingdom Protista.

In 1959 American biologist R. H. Whittaker described a classification system of five primary kingdoms: plants, animals, fungi, protists, and bacteria. Because the Protista are so diverse in form, classification within the kingdom has proved difficult. The classification of the Protista is currently based largely on the structure and organization of the cell, the presence of organelles, and the pattern of reproduction or life cycles. The five-kingdom classification system divides the Protista into 27 distinct phyla. More recently, however, classifications based on comparisons of cell physiology and DNA sequences suggest that many protist phyla may be sufficiently large and diverse to be classified as kingdoms.

The plantlike protists include the golden algae (phylum Chrysophyta), dinoflagellates (Pyrrophyta), cryptomonads (Cryptophyta), and euglenoids (Euglenophyta). The animallike protists, which are also called protozoa, include the animal flagellates (Zoomastigina), amoeboid forms (Sarcodina), ciliates and suctorians (Ciliophora), and the parasitic, spore-producing sporozoans (Sporozoa). Funguslike forms include the hyphochytrids (Hyphochytridiomycota) and the plasmodiophores (Plasmodiophoromycota). The slime molds, which include several disputed phyla here treated as belonging to the Protista, have characteristics of both fungi and protozoans.

Task10. Answer the questions.

1. When were the first detailed descriptions of protists made?

2. What group of organisms was the term Protista applied to?

3. What is the classification of the Protista currently based on?

4. What phyla do the plantlike protists include?

5. What phyla do the animallike protists include?

6. What phyla do the funguslike protists include?

Task11. Prove the statement.

Classification of protists poses some difficulties to scientists.

Task12. Translate the following words and word combinations into English and memorize them.

кишечник

важные пищеварительные процессы

выдвигать теорию

иметь устойчивость к химическим соединениям

расщеплять сложные органические молекулы

фотосинтезирующие протисты

отличительная расцветка

слияние двух различных видов

быть способным к движению

захватывать добычу

подвижный

оказаться сложным

простейшие

GRAMMAR SECTION

Task1. Paraphrase these sentences.

Example: Protists are unicellular organisms and they can only be seen with a microscope.

Being unicellular organisms, protists can only be seen with a microscope.

1. Spores are the infectious stage of organisms; they cause diseases in humans when ingested.

2. Plastids and mitochondria were once free-living bacteria; they became organelles through the process of symbiosis.

3. Pigments are synthesized within plastids; they capture the sunlight and give photosynthetic protists their distinct colors.

4. Some microscopic organisms are both motile and photosynthetic; they are neither clearly animallike nor plantlike.

5. There are classifications based on comparisons of cell physiology and DNA sequences; they suggest that many protist phyla may be sufficiently large and diverse to be classified as kingdoms.