II. Read the following text paying attention to the highlighted words. Explain or interpret the contextual meaning of the underlined phrases

Although a great deal is known about life, defining life turns out to be more difficult than one might suppose. There is no simple description that sets living organisms apart from nonliving matter. The most generally accepted definition of life describes it as the state of a material complex or individual characterized by the capacity to perform certain functional activities, including metabolism, growth, reproduction, and some form of responsiveness and adaptation. Life is further characterized by the presence of complex transformations of organic molecules and by the organization of such molecules into the successively larger units of protoplasm, cells, organs, and organisms.

Metabolism is the most obvious hallmark of life. Every organism carries out chemical reactions that release energy. The metabolismof an organism is the sum of all the chemical reactions it performs. Some organisms obtain their energy by taking up complex chemical substances (foods) from their environment and metabolizing these substances to release energy and to make chemical building blocks from which other substances may be made. Such organisms are called heterotrophs(other-feeders). The remaining species are autotrophs(self-feeders) and obtain their energy either from sunlight or, in a few cases, by taking up very simple mineral substances (but not foods) and carrying on energy-releasing metabolism based on changes in those substances. Modern-day heterotrophs obtain their energy directly or indirectly from the autotrophs.

Growth and reproductionare always associated with life. Unicellular organisms grow to a certain size and then divide. Some more complex organisms bud off small portions of their bodies to form new individuals. Most large organisms reproduce by means of special cells produced specifically for that purpose. The key is that these reproductive portions, however small, contain the information necessary to form an entire new individual.

Heredity and mutability are also essential features of life. When living things reproduce, they often produce offspring that are not exact copies of themselves. The difference between parents and offspring can, in turn, be transmitted to the next generation, usually with additional changes. It is this property of reproducing with changesthat makes possible the evolution of life and gives life one of its most distinctive features: adaptation.When we say that organisms are adapted to their environments, we mean that they have characteristics that enable them to survive and reproduce in those environments. It has long been evident that living organisms are adjusted to their environments in remarkably subtle ways, but people found it difficult to develop scientifically rigorous ways to study how organisms had become adapted. Biology could not and did not become a sophisticated science until scientific methods could be applied to the study of adaptation. This did not occur until a little over a century ago, when Charles Darwin proposed the first scientifically testable theory about adaptation.

Adaptation is a uniquely biological notion. It does not make sense to ask what the functionof the law of gravity is or what the adaptive significance of the relationships among temperature, pressure, and volume of a sample of a gas is. These are features of the nonliving world that we simply take as given, and the explanations of them are sought in purely mechanistic terms. However, in biology we do ask questions about function — for example, “What do wings do?” All studies of wings, even purely descriptive ones, are strongly influenced by thoughts about function. It is, in fact, difficult to describe a wing without referring to its function. Structure in biology is strongly linked to function, and biologists look at differences in structure to find out how they affect functioning.

Another specific feature of life lies in the fact that all the organisms on the Earth are extremely closely related, despite superficial differences. The fundamental ground pattern, both in form and in matter, of all life on Earth is essentially identical. This identity probably implies that all organisms on Earth are evolved from a single instance of the origin of life.

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II. Listen to the second fragment and complete the following sentences. Study the following words before listening	\|	Vocabulary notes

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