新托福阅读真题详解:Opportunists and Competitors机会主义者和竞争者

　　Growth, reproduction, and daily metabolism all require an organism to expend energy. Theexpenditure of energy is essentially a process of budgeting, just as finances are budgeted. Ifall of one’s money is spent on clothes, there may be none left to buy food or go to the movies.Similarly, a plant or animal cannot squander all its energy on growing a big body if none wouldbe left over for reproduction, for this is the surest way to extinction.

　　All organisms, therefore, allocate energy to growth, reproduction, maintenance, andstorage. No choice is involved; this allocation comes as part of the genetic package from theparents. Maintenance for a given body design of an organism is relatively constant. Storage isimportant, but ultimately that energy will be used for maintenance, reproduction, or growth.Therefore the principal differences in energy allocation are likely to be between growth andreproduction.

　　Almost all of an organism’s energy can be diverted to reproduction, with very little allocatedto building the body. Organisms at this extreme are “opportunists.” At the other extreme are“competitors,” almost all of whose resources are invested in building a huge body, with a bareminimum allocated to reproduction.

　　Dandelions are good examples of opportunists. Their seed heads raised just high enough abovethe ground to catch the wind, the plants are no bigger than they need be, their stems arehollow, and all the rigidity comes from their water content. Thus, a minimum investment hasbeen made in the body that becomes a platform for seed dispersal. These very short-livedplants reproduce prolifically; that is to say they provide a constant rain of seed in theneighborhood of parent plants. A new plant will spring up wherever a seed falls on a suitablesoil surface, but because they do not build big bodies, they cannot compete with other plantsfor space, water, or sunlight. These plants are termed opportunists because they rely on theirseeds’ falling into settings where competing plants have been removed by natural processes,such as along an eroding riverbank, on landslips, or where a tree falls and creates a gap in theforest canopy.

　　Opportunists must constantly invade new areas to compensate for being