Nonflowering Plants

Plants that do not use flowers for reproduction include conifers, ferns, mosses, and seaweeds (the last are not true plants). Conifers reproduce by means of cones. A male cone is usually smaller than а female cone, and both are usually carried on the same tree. Conifers have needlelike leaves, whose small surface area prevents the plant losing too much water. This helps conifers survive in the cold, dry places they often live in. Many conifers are evergreen - they do not shed their leaves in the fall.

11. Read the text find English equivalents to the Russian words and expressions:

1. Лепестки, 2. опыление, 3. оплодотворение, 4. разбрасывание семян, 5. однодольные, 6. двудольные.

Flowering Plants

Using flowers to reproduce is so efficient that flowering plants are the most widespread of all ants. Flowers carry the reproductive organs within a ring of petals. After pollination and fertilization, the flowers produce seeds, which are enclosed and protected by fruits. These have clever ways of scattering their seeds. Some flowering plants, such as maize, make seeds in one part; they are monocots. Others, such as bean plants, make seeds in two parts; they are dicots.

Read the text and match the sentences in A with the Russian equivalents in B

Fungi

A

1. Although some fungi, such as yeasts, are one-celled and microscopic, most are multicellular (made up of many cells) and visible. 2. The cells are linked together in a thread called a hypha.3. Lots of hyphae make up a mycelium. 4. This is the main part of the fungus. 5. Most fungi are saprotrophs, ' which means that they feed on dead and decaying materials. 6. Some are animal or plant parasites.

7. Mushrooms and toadstools are probably the most well-known fungi. 8. Their hyphae grow under the soil and send up fruiting bodies (such as mushrooms), that produce spores. 9. Spores are one-celled reproductive structures that grow into new fungi.

B

a) Большое количество таких нитей составляет мицелий.

b) Хотя некоторые грибы, такие как дрожжи, одноклеточные и микроскопических размеров, большинство из них многоклеточные (состоят из многих клеток) и видны невооруженным глазом.

c) Их нити разрастаются под слоем почвы, от них на поверхность выходят плодоносные тела (такие как съедобные грибы),

d) Большинство грибов сапротрофы, т.е. питаются вымершими или гниющими материалами.

e) Споры - это одноклеточные воспроизводящие структуры, которые вырастают в новые грибы.

f) Клетки соединены вместе в виде нитей.

g) Некоторые из них паразитируют на животных или растениях.

h) Это основная часть гриба.

i) Съедобные грибы и грибы-поганки, вероятно, известны лучше всех остальных.

UNIT 4

1. Read the text and answer the questions:

What are cells?

What are their types?

What are cells composed of?

Cell is the fundamental structural unit of all living organisms. Some cells are complete organisms, such as the unicellular bacteria and protozoa; others, such as nerve, muscle cells, are specialized components of multicellular organisms. Small numbers of cells may be associated in colonies. Cells are range in size from the 0.1 micron to the 8 cm in diameter. Cells are of two different types, procaryotes and eucaryotes; thus, living world is divided into two broad categories. Many eucaryotic cells are further divided into compartments by internal membranes in addition to nuclear envelope, whereas procaryotic cells never contain completely internal membranes. The procaryotes include the mycoplasmas, bacteria and blue-green algae. In general, plant cells differ from animal cells in that they have a rigid cell wall exterior to the plasma membrane; a large vacuole and chloroplasts that convert light energy to chemical energy for the synthesis of glucose.

Cells are composed primarily of oxygen, hydrogen, carbon and nitrogen. The most important organic compounds in a cell are proteins, nucleic acids, lipids and polysaccharides. Water makes up 60 to 65 percent of the cell, because water is favorable environment for biochemical reactions.

What do cells consist of?

Cells consist of many components. The plasma membrane, a continuous double layer of phospholipid molecules, constitutes the boundary between the cell and its external environment. In addition to lipids, the plasma membrane has protein components. The structure as a whole is selective permeable. The plasma membrane contains receptors that selectively receive nerve and hormone signals and transmit them to the interior of the cell. Direct cell-to-cell interactions can occur through specialized regions of plasma membrane known as junctions.

Exterior to the plasma membrane of most plant and bacteria is a cell wall, a cell product made largely complex of polysaccharides. The cytoplasm is the water-rich matrix within a cell that contains and surrounds the other cellular contents. Nucleus is the membrane-bounded structures contained within the cytoplasm of eucaryotes are referred to as organelles. DNA, combined with protein, is organized inside the nucleus into structural units called chromosomes, which usually occur in identical pairs. Genes contain the coded instructions for the assembly of polypeptides and larger proteins. The nucleus is surrounded by an envelope of two concentric membranes. The nucleus also contains a specialized region, the nucleolus, where nucleoprotein particles are assembled

What are ribosomes?

Ribosomes are the "factories" where the instructions encoded in the DNA of the nucleus are translated to make proteins. Among the other membranous structures are extensive membrane systems that make up the smooth and rough endoplasmic reticulum. The rough endoplasmic reticulum is one of the sites of protein synthesis in the cytoplasm. Similar in appearance to and perhaps continuous with the endoplasmic reticulum is a region of smooth, stacked membranous sacks known as Golgi apparatus. The apparatus modifies proteins after they are synthesized and packaged on the rough endoplasmic reticulum-by linking them with sugars or other molecules.

What are lysosomes? What are mitochondria?

Lysosomes are membrane-bounded vesicles, containing digestive enzymes. Their normal function is digestion of complex nutrients and broken-down organelles. Mitochondria are the powerhouses of the animal cell, where the products of the metabolism of nutrients are converted into energy in the form of molecule ATP. Plants possess, in addition to mitochondria, similar organelles called chloroplasts. Each chloroplast contains chlorophyll which is used to convert light energy to the ATP. This process is called photosynthesis.

All animal and some plant cells contain a pair of centrioles. Centrioles control the arrangement of microtubes in cytoskeleton.

What is the process called meiosis?

All cells are the products of division of preexisting cells. Simple cell division, or asexual reproduction, normally results in the production of two identical daughter cells. Sexual reproduction is the mingling of the DNA of two different organisms of the same species to produce cells with a new combination of genes. In multicellular organisms sexual reproduction requires the production of male and female germ cells by a process called meiosis.

In higher plants and animals the cells are organized into tissues, or groups of cells with similar structure and functions. Combinations of tissues make up organs with more or less distinct functions. In the animal; the organs are associated in systems that are responsible for certain functions.

Date: 2015-04-23; view: 712; Нарушение авторских прав