Problems of South Florida ecosystems

1. Each member of an ecosystem belongs to the environment of every other part of that system, so any change in one alters the environment for all the others. And as those components react to the alteration, they in turn continue to transform the environment for the others.

2. Since human beings first walked the earth, they have affected each ecosystem they have inhabited. For example, a century ago the interconnected Kissimmee River – Lake Okeechobee – Everglades ecosystem comprised one of the most productive and stable wetland regions on earth. But marsh and slow-moving water stood in the way of urban and agricultural development. Intricate systems of ditches and canals were built and, since 1900, half of the original 4 million acres of the Everglades has disappeared.

3. The Kissimmee River has been channelized into an arrow-straight ditch, and wetlands along the river have been drained. Levees have prevented water in Lake Okeechobee from contributing sheet flow to the Everglades, and highway construction has deviled the region, further disrupting natural drainage patterns. Fires have been more frequent and destructive, and entire biotic communities have been eliminated by lowered water levels. During excessively wet periods, portions of the Everglades are deliberately flooded to prevent drainage canals from overflowing. As a result, animals drown and birds cannot rest and reproduce. South Florida's wading bird population decreased by 95% within a hundred years.

4. Without the natural pu­rifying effects of wetland systems, water quality in South Florida has deteriorated, and with lower water levels, salt water encroachment is a serious problem in coastal areas. Today, backed by regional, state, and 227 federal agencies, scientists are struggling to restore South Florida's ailing ecosystems. There are extensive plans to allow the Kissimmee River to meander again across its former floodplain, to return agri­cultural land to marsh, and to restore historic water flow patterns through the Everglades.

5. The problems of South Florida should serve as a useful lesson. Alterations of the natural environment should not be undertaken without serious consideration of all the consequences. All citizens of the earth must understand the effects of their actions on the complex earth system.

 

II Прочтите 4-ый абзац текста и письменно ответьте на следующий вопрос:

What plans do scientists have for restoring South Florida's ailing ecosystems?

 

Контрольная работа № 5

(для специальности ТД)

Вариант 1

I Прочтите и устно переведите с 1-го по 6-ой абзацы текста.

Перепишите и письменно переведите 3, 5, 6 абзацы текста.

ANNUAL RINGS AND WOOD RAYS

1. If you look at a cross-section of a log you will see rings that surround the pith. These rings are called growth rings (or annual rings). On the outer side of the log you can see the bark that protects the inside of the tree.

2. The older is the tree, the more growth rings it has. By counting the rings you can tell the approximate age of the tree. If you want to be more exact, you must cut the tree very near the ground orthe first year or two is missed.

3. In the temperate zones the trees grow only during the spring and summer months. During the colder seasons the cambium is dormant. Cambium is a very thin growing layer between the bark of the tree and the wood. Each year (in spring and summer) the cambium produces a layer of wood and bark between the wood and the bark. This layer of wood makes the new annual ring.

4. We can clearly see the annual rings because of the difference in the growth of the early-formed cells from the late-formed cells. During the early part of the growing season the tree grows more rapidly and the cells are larger and have thinner walls. This rather porous layer of wood is called earlywood or springwood. Later in the growing season the tree grows slower and the cells become smaller and thick-walled. This layer of wood is called latewood or summerwood.

5. On a cross-section of a tree you can also see thin lines going from the centre of the tree to the cambium at right angles to the growth rings. These are wood rays, they are made up of cells that are oriented horizontally (the majority of the cells in the tree are oriented vertically). The main function of the wood rays is to conduct materials to and from the cambium re­gion. The rays also serve as storage places.

6. In coniferous trees, such as pine, spruce, larch and Douglas fir there are also resin canals. They are passages between cells and are often filled with resin. In addition to the normal resin canals, you may find traumatic, or wound, canals not only in the species which usually have resin canals but also in some other conifers (such as fir and hemlock).

 

II Прочтите 4-ый абзац текста и исьменно ответьте на следующий вопрос:

Why can we clearly see the annual rings on a cross-section of a tree?

 

 

Контрольная работа № 5

(для специальности ТД)

Вариант 2