如图表示从南极（90°S）经过赤道（0°）到北极（90°N）纬度梯度上物种多样性的变化趋向．试分析说明：
（1）从极地向热带推移，物种的变化趋势是______．这表明某个地区物种的多少主要取决于______．
（2）试推断：随着海拔高度增加，物种的数量变化是______．
（3）试推断：污染环境的物种多样性的变化趋向是______．
（1）根据曲线，热带推移，群落中物种变化是逐渐增多；这表明某地区群落物种的多少主要取决于温度等生态因素．
（2）在高山植物群落，不同海拔地带的植物分布主要受温度制约，海拔高度越高，温度越低，物种的数量变化是逐渐减少，反之会增加；
（3）外界环境的污染也会此起物种的变化，会使许多物种灭绝或面临灭绝的危险．
故答案为：（1）逐渐增多，温度等条件（2）逐渐减少（3）污染程度越大，物种越少
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| I used to hate being called upon in class mainly because I didn't like attention drawn to myself. And 1 otherwise assigned (指定) a seat by the teacher. I always 2 to sit at the back of the classroom. All this 3 after I joined a sports team. It began when a teacher suggested I try out for the basketball team. At first I thought it was a crazy 4 because I didn't have a good sense of balance, nor did I have the 5 to keep pace with the others on the team and they would tease me. But for the teacher who kept insisting on my ' 6 for it', I wouldn't have decided to give it a try. Getting up the courage to go the tryouts was only the 7 of it! When I first started 8 the practice sessions, I didn't even know the rules of the game, much 9 what I was doing. Sometimes I'd get 10 and take a shot at a wrong direction-which made me feel really stupid. 11 , I wasn't the only one "new" at the game, so I decided to 12 on learning the game, do my best at each practice session, and not to be too hard on myself for the things I didn't 13 "just yet". I practiced and practiced. Soon I knew the 14 and the "moves". Being part of a team was fun and motivating. Very soon the competitive 15 in me was winning over my lack of confidence. With time, I learned how to play and make friends in the 16 -friends who respected my efforts to work hard and be a team player. I never had so much fun. With my 17 self-confidence comes more praise from teachers and classmates. I have gone from " 18 " in the back of the classroom and not wanting to call attention to myself, 19 raising my hand-even when I sometimes wasn't 100 percent 20 I had the right answer. Now I have more self-confidence in myself. | ||||
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