GENERAL SYSTEMS THEORY
1 The Greek word “systema” means union, and scientists use the word “system” to describe a collection of several components that are linked to one another by functional relationships. Everything outside the system is known as the surroundings. Most scientific literature is a description of the components of a system, their relationships with one another, and their relationships with other systems. Although each science has its own systems with their own subject matter and networks of relationships, the formal characteristics of systems are similar for all sciences. The scientific discipline called genera! systems theory formulates principles that are valid for systems in general, no matter the elements involved and the relations or forces among them.
2 Systems can be divided into two types: closed systems and open systems. A closed system receives no supply of energy from outside and transfers no energy outwards. An open system receives energy from its surroundings and transfers it out again.
3 A closed system is isolated from its surroundings. The energy supply of a closed system is limited and is progressively used up by the processes operating within the system. The ability of the system to function decreases as the available energy is exhausted. Without any additional energy supplied from the outside, the system’s processes stop altogether and no further change is possible in the system. A mill wheel supplied with water from a non-refillable container is a closed system. Once the container of water is empty, the wheel no longer turns because there is no water to turn it. In a truly closed system, the water would have to be collected below the mill wheel in a second container to ensure that the system did not supply any energy to the outside.
4 Some scientists argue that there are few truly closed systems in nature, and many define closed systems more broadly as those allowing energy but not mass to cross the system boundary. By this definition, the Earth system as a whole is a closed system. The boundary of the Earth system is the outer edge of the atmosphere, and except for the occasional meteorite, virtually no mass is exchanged between the Earth system and the rest of the universe, However, energy in the form of solar radiation passes from the sun, through the atmosphere to the Earth’s surface, which in turn radiates energy back out to space across the system boundary. Hence, energy passes across the Earth’s system boundary, but mass does not, making it a closed system.
5 In an open system, energy and mass can be transferred between the system and its surroundings. Living organisms are open systems. They absorb light energy or chemical energy in the form of organic molecules and release heat and metabolic waste products, such as carbon dioxide, to the surroundings. Generally, relationships exist between the components of a system and its surroundings, that is, other systems. Each open system is part of a larger system that receives and gives off energy. In an open system, the energy is continually resupplied from sources outside the system. In the example of the mill wheel, if the non -refillable water container is replaced by a reservoir fed continuously by a stream, it becomes an open system because the energy supply is renewed from the outside.
6 The natural environment is made up of open systems. These can behave as closed systems temporarily if the energy supply is halted for a period. If, for example, the stream to the reservoir supplying the mill dries up for a long period, the energy consumption of the mill wheel cannot be balanced by new energy supply. The water in the reservoir is used up, and if the dry period is long enough, the mill wheel stops turning. Eventually, the stream may flow again, filling the reservoir and turning the mill wheel again. This occurs bccause the stream-reservoir-mill system is itself a part of the Earth’s much larger systems of water circulation and water budget, which include condensation, precipitation, run-off, and evaporation. The water systems receive their energy supply from the Earth’s heat budget, which in turn receives its energy supply from the sun’s radiation.
14. According to the passage, the concept of systems involves all of the following EXCEPT
(X) the components of a collection
(X) the functional relationships among parts
(X) the links between different systems
(X) the origin of the scientific method
15. Which sentence below best expresses the essential information in the highlighted sentence in paragraph 1 ? Incorrect choices change the meaning in important ways or leave out essential information.
(X) Every science has a unique set of systems with characteristics and relationships that do not exist in any other science.
(X) The subject matter of systems is the same for all sciences, but the structure of system relationships can vary.
(X) System components and relationships differ for each science, yet systems in all sciences share similar properties.
(X) It is difficult to distinguish one system from another because all systems in all sciences have similar characteristics.
16. The word them in paragraph 1 refers to
17. The word exhausted in paragraph 3 is closest in meaning to
18. In paragraph 3, the author discusses the example of a mill wheel to illustrate what point about closed systems?
(X) The energy supply of a closed system is limited.
(X) Closed systems are rare in the natural environment,
(X) The Earth system as a whole is a closed system.
(X) Closed systems get energy from their surroundings.
19. According to paragraph 4, the Earth system as a whole is a closed system because
(X) the Earth receives no energy from outside the system boundary
(X) the boundary of the Earth system is clearly defined
(X) no mass crosses the system boundary, but some energy does
(X) the Earth system uses energy from solar radiation to support life
20. It can be inferred from paragraph 5 that living organisms
(X) are part of a larger system that receives and gives off energy
(X) can transfer energy but not mass across the system boundary
(X) do not have functional relationships with their surroundings
(X) can survive in a closed system only if there is a water supply
21. The phrase dries up in paragraph 6 is closest in meaning to
(X) slowly rises
(X) becomes warmer
(X) is polluted
(X) stops flowing
22. Which of the following statements can be inferred from paragraph 6?
(X) If a mill wheel stops turning, it will not start again until the following year.
(X) The mill wheel is temporarily a closed system during long dry periods.
(X) Condensation, precipitation, run-off, and evaporation act as closed systems.
(X) The Earth’s heat budget is a closed system because its energy supply is limited.
23. Why does the author mention water circulation and water budget in paragraph 6?
(A) To give examples of open systems that behave as closed systems
(B) To illustrate the point that open systems are part of larger systems
(C) To emphasize the importance of water in the Earth system
(D) To introduce a discussion of threats to the Earth’s energy supply
24. Look at the four squares [A], [B], [C], [D] which indicate where the following sentence could be added to the passage. Where would the sentence best fit?
For example, the hot tea in a vacuum bottle does not interact with the environment outside the bottle.
A closed system is isolated from its surroundings. [A] The energy supply of a closed system is limited and is progressively used up by the processes operating within the system. [B] The ability of the system to function decreases as the available energy is exhausted. Without any additional energy supplied from the outside, the system’s processes cease altogether and no further change is possible in the system. [C] A mill wheel supplied with water from a non- refillable container is a closed system. Once the container of water is empty, the wheel no longer turns because there is no water to turn it. In a truly closed system, the water would have to be collected below the mil! wheel in a second container to ensure that the system did not supply any energy to the outside. [D]
25. Select the appropriate sentences from the answer choices and match them to the type of system that they describe. TWO of the answer choices will NOT be used. This question is worth 3 points.
(A) It is a collection of things that have no relationship to one another.
(B) Its processes eventually use up all of its limited energy supply.
(C) Both energy and mass can pass across the system boundary.
(D) It is part of a larger system with which it interacts and exchanges energy.
(E) No exchanges of mass occur between the system and its surroundings.
(F) It is a large mass of a single element that cannot be changed in any way.
(G) The energy supply is continually renewed from the surroundings.