Irma

托福閱讀 練習小短文 - 生態多樣性和生態結構 (生物、環境學科) 

想要了解托福閱讀，國際性期刊、學刊或科學性雜誌一定要多看，不然很難很從托福文章的單字中完整地理解整篇文章，而且僅靠著單字去理解文章也會非常耗時，這是非常影響考試時間的，所以托福單字雖然很重要，因為沒單字就沒有辦法理解內容，但空有單字沒有任何知識背景的存在，也是會造成很大的影響。

  Biodiversity and Ecosystem

    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 mountains to the depths of deep-sea hydrothermal vents, and from polar ice caps to tropical rain forests.

 The array of living organisms found in a particular environment together 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 available clean air and water and plentiful oxygen. Forests, for example, regulate the amount of carbon dioxide in the air, produce oxygen as a byproduct of photosynthesis, and control rainfall and soil erosion. Ecosystems, in turn, depend on the continued health and vitality of the individual organisms that compose them. Removing just one species from an ecosystem can prevent the ecosystem from operating optimally.

   The rich diversity of the living world is closely connected in a way called ecological diversity, which is the intricate network of different species present in local ecosystems and the dynamic interplay between them. 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 isconverted to chemical energy by plants. This energy flows through the systems when animals eat the plants and then are eaten, in turn, 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, animals, and fungi—and nonliving components—climate and chemicals—that are connected by energy flow.

    Removing just one species from an ecosystem damages the flow of energy of that system. For instance, in the late 19th 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 urchin 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.

    Yet 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 theestimate of American evolutionary biologist Edward O. Wilson that the Earth is losing approximately 27,000 species per year.

    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 1975 to outlaw the trade of endangered animals and animal parts. In the United States, the Endangered Species Act (ESA) was enacted in 1973 to protect endangered or threatened species and their habitats. The Convention on Biological Diversity, held in Rio de Janeiro, Brazil, in 1992 and ratified by more than 160 countries, obligates governments to take action to protect plant and animal species.