Day 7

Passage 7

Biodiversity and Ecosystem

① Biodiversity, or Biological Diversity, is the sum of all the different species of animals, plants, fungi, and microbial organisms living on Earth, and the variety of habitats in which they live. Scientists estimate that upwards of 10 million—and some suggest more than 100 million—different species inhabit the Earth. Each species is adapted to its unique niche in the environment, from the peaks of the mountains to the depths of the deep-sea hydrothermal vents, and from polar ice caps to tropical rain forests.

② A particular environment with its own array of living organisms, with the physical and environmental factors that affect them, is called an ecosystem. Healthy ecosystems are vital to life: They regulate many of the chemical and climatic systems that make clean air, water, and plentiful oxygen available. The numerous forests in nature are comparable to lungs in humans—regulating the amount of carbon dioxide in the air and producing oxygen as a byproduct of photosynthesis.【1】Ecosystems, in turn, depend on the continued health and vitality of the individual organism that compose them. Removing just one species from an ecosystem can prevent the ecosystem from operating optimally.

③ Local ecosystems, and the dynamic interplay and intricate network of different species present in between them contribute to a rich and diverse living world. This is what's called ecological diversity. An ecosystem consists of organisms from many different species, living together in a region, that are connected by the flow of energy, nutrients, and matter that occurs as the organisms of different species interact with one another. The ultimate source of energy in nearly all ecosystems is the Sun. The Sun's radiant energy is converted to chemical energy by plants. This energy flows through the systems when animals eat the plants and, in turn, are eaten by other animals. Fungi derive energy by decomposing organisms, releasing nutrients back into the soil as they do so. An ecosystem, then, is a collection of living components—microbes, plants and animals—and nonliving components— climate and chemicals—that are connected by energy flow.

④ Removing just one species from an ecosystem, damages the flow of energy of that system. For instance, in the late 1 th and early 20th centuries, sea otters were hunted to near extinction in many kelp forests, off the coast of the Pacific Northwest of the United States and western Canada, causing the entire ecosystem to suffer. Otters eat sea urchins, small, spiny organisms that share their habitat. When the otters disappeared, the sea urchins' population exploded and started to destroy the vast beds of kelp. Without the kelp, other species that lived in the ecosystem, including many species of fish and snails and other invertebrates, began to decline in number. Efforts to restore sea otter populations brought the kelp communities back to near normal in the late 20th century.

⑤ Yet, despite efforts, the world is now facing a diversity crisis all over. The survival of natural ecosystems around the world is threatened by many human activities: bulldozing wetlands and clear-cutting forests—the systematic cutting of all trees in a specific area—to make room for new housing and agricultural land; damming rivers to harness the energy for electricity and water for irrigation; and polluting the air, soil, water, and so on. Most biologists have accepted the estimate of American evolutionary biologist Edward O. Wilson that the Earth is losing approximately 27,000 species per year.

⑥ As the scope and significance of biodiversity loss become better understood, positive steps to stem the tide of the sixth extinction have been proposed and, to some extent, adopted. Several nations have enacted laws protecting endangered wildlife. An international treaty known as the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) went into effect in 1175 to outlaw the trade of endangered animals and animal parts. In the United States, the Endangered Species Act (ESA) was enacted in 1173 to protect endangered or threatened species and their habitats. The Convention on Biological Diversity, held in Rio de Janeiro, Brazil, in 1112 and ratified by more than 160 countries, obligates governments to take action to protect plant and animal species.

——2012年 3月 23日北美机经

The word“that” in Paragraph 3 refers to ______ .

A. ecosystem

B. organisms

C. species

D. region

词汇练习：

阅读下列句子，用所给单词（或词组）的正确形式填空：

radiant

vital

regulate

invertebrate

estimate

dynamic

decompose

compose

1. In order to understand ancient Egyptian art, it is ______ to know as much as possible of the elite Egyptians' view of the world and the functions and contexts of the art produced for them.（TPO-11：Ancient Egyptian Sculpture）

2. It subconsciously adjusts breathing rate and depth in order to ______ the levels of carbon dioxide (CO2) and oxygen (O2), and the acid-base ratio in the blood.（TPO-24：Breathing During Sleep）

1. We can say that the properties of an ecosystem are more stable than the individual organisms that ______ the ecosystem.（TPO-1：The Long-Term Stability of Ecosystems）

4. Most people consider the landscape to be unchanging, but Earth is a ______ body, and its surface is continually altering—slowly on the human time scale, but relatively rapidly when compared to the great age of Earth (about 4,100 billion years).（OG：Geology and Landscape）

5. The second factor is that ______ heat coming into the city from the Sun is trapped in two ways: (1) by a continuing series of reflection among the numerous vertical surfaces that buildings present and (2) by the dust dome, the cloudlike layer of polluted air that most cities produce.（TPO-21：Urban Climates）

6. Large concentrations of single-celled organisms with green pigments (coloring substances) occur along the edges of the ice shelves in this region, and the seawater is rich in their ______ organic material.（OG Test 2：Green Icebergs）

7. Indeed, unaltered shells of marine are known ______ from deposits over 100 million years old.（TPO-20：Fossil Preservation）

8. By measuring how many of these meteorites fall to Earth over a given period of time, scientists can ______ how long it might have taken to deposit the observed amount of Ir in the boundary clay.（TPO-8：Extinction of the Dinosaurs）

参考答案：

1. vital

2. regulate

3. compose

4. dynamic

5. radiant

6. decomposing

7. invertebrates

8. estimate

【1】与今日百句译（Sentence 7）相同的句型。