2022-2023年考博英语-北京师范大学模拟考试题(含答案解析)第41期
52页1、2022-2023年考博英语-北京师范大学模拟考试题(含答案解析)1. 单选题Why do some desert plants grow tall and thin like organ pipes? Why do most trees in the tropics keep their leaves year round? Why in the Arctic tundra are there no trees at all? After many years without convincing general answers, we now know much about what sets the fashion in plant design.Using terminology more characteristic of a thermal engineer than of a botanist, we can think of plants as mechanisms that must balance their heat budgets. A plant by day
2、 is staked out under the Sun with no way of sheltering itself. All day long it absorbs heat. If it did not lose as much heat as it gained, then eventually it would die.Plants get rid of their heat by warming the air around them, by evaporating water, and by radiating heat to the atmosphere and the cold, black reaches of space temperature is tolerable for the processes of life. Plants in the Arctic tundra lie close to the ground in the thin layer of still air that clings there. A foot or two abov
3、e the ground are the winds of Arctic cold. Tundra plants absorb heat from the Sun and tend to warm up; they probably balance most of their heat budgets by radiating heat to space, but also by warming the still air that is trapped among them. As long as Arctic plants are close to the ground, they can balance their heat budgets. But if they should stretch up as a tree does, they would lift their working parts, their leaves, into the streaming Arctic winds. Then it is likely that the plants could n
4、ot absorb enough heat from the Sun to avoid being cooled below a critical temperature. Your heat budget does not balance if you stand tall in the Arctic.Such thinking also helps explain other characteristics of plant design. A desert plant faces the opposite problem from that of an Arctic plant the danger of overheating. It is short of water and so cannot cool itself by evaporation without dehydrating. The familiar sticklike shape of desert plants represents one of the solutions to this problem:
《2022-2023年考博英语-北京师范大学模拟考试题(含答案解析)第41期》由会员枫**分享,可在线阅读,更多相关《2022-2023年考博英语-北京师范大学模拟考试题(含答案解析)第41期》请在金锄头文库上搜索。
2022年幼儿园环境创设年度工作总结报告
2023年国有企业改革现存问题及对策
中层干部任前廉政谈话内容三篇
【精品】沪科版九年级数学上21.3二次函数与一元二次方程3导学案
高考数学广东专用文科大一轮复习配套课时训练:第八篇 平面解析几何 大题冲关集训(五)含答案
BookV高三一轮复习知识梳理
应用AUTO LISP在南方CASS中批量处理图形数据毕业论文
教育质量提升行动总结
精选大连民族学院专业技术职务任职满考核登记表
房屋租赁信托合同范文(4篇).doc
安妮日记读后感例文1000字
文秘基础知识
【最新教材】人教版高中数学必修三随机事件的概率达标练习
车间主任年终总结样本(2篇).doc
历年高考试题成语测试情况统计表
全国农村中医药工作先进单位检查评价细则
诚信班会班主任总结
沪科版八年级下册物理期末复习-第八章---压强-计算题-练习(包含答案)
好用的散文的作文300字汇编7篇
年产xxx套胰岛素注射器械项目投资分析报告(参考范文)
2022-08-23 70页
2023-10-13 12页
2023-06-12 80页
2023-10-01 70页
2023-11-09 145页
2023-11-27 51页
2023-05-20 4页
2023-01-22 253页
2023-07-12 54页
2023-03-09 2页