题目

生活在同一区域内， _________的所有个体形成一个整体 —— 种群；所有种群相互作用形成更大的整体 ——________ ； ________ 与 __________ 相互作用形成更大的整体 —— 生态系统；地球上所有的生态系统互相关联构成更大的整体 ——____________ 。 答案：同种生物群落生物群落无机环境生物圈 【解析】 略Training for a marathon (马拉松) requires careful preparation and steady, gradual increases in the length of the runs. 【1】, buy the best-fitting running shoes you can find. No one can say which brand will work best for you or feel best on your feet, so you have to rely on your experience and on the feel of each pair as you shop. When you have found shoes that seem right, walk in them for a few days to double-check the fit. 【2】. As always, you should stretch (伸展) at least ten minutes before each run to prevent injuries.During the first week, do not think about distance, but run five minutes longer each day. 【3】, it is wise to take a day off to rest. But during the next week, set a goal of at least a mile and a half per run. 【4】. After two weeks, start timing yourself. 【5】. Depending on the kind of race you plan to enter, you can set up a timetable for the remaining weeks before the race.A. After six daysB. For a good marathon runnerC. Before you begin your trainingD. With each day, increase the distance by a half mileE. If they still feel good, you can begin running in themF. Time spent for preparation raises the quality of trainingG. Now you are ready to figure out a goal of improving distance and time