4．
Directions：Read the passage carefully．Then answer the questions or complete the statements in the fewest possible words．
The internal greenhouse effect of a daffodil（水仙花）shui10
Early pollinators （授粉昆蟲） struggle with cold weather，so it's no wonder that late-winter flowers such as daffodil tend to have extended blooming times and long-lasting flowers，some of which remain open for more than two weeks．When the sun is out，they can offer a warm microenvironment for bees．
Although they usually start showing off in the Washington area by late February，blooming times for daffodil are highly variable，depending on variety，weather and planting location．Moisture，tree cover and mineral availability all affect flowering time，but soil temperature tends to have the greatest influence on early-blooming flowers．The microclimate of a south-facing slope will display blooms well before flowers appear in the shadow of a building that gets only a half-day of sun．
Once open，the flower can create a microclimate within itself．When sunlight hits a daffodilflower，its tube-shaped corolla acts as a tiny greenhouse，raising temperatures inside a flower as much as 15degrees higher than the surrounding air．
That's good news for small bees，which in late winter have trouble getting warm enough to fly．
Bumblebees and honeybees prepare to fly on cold days by exercising their flight muscles to generate heat．But mining bees，which nest in the ground，are less able to do that and are more dependent on surrounding temperatures to warm them up for takeoff．
Spanish ecologist Carlos M．Herrera studied the relationship between mining bees and native daffodil flowers．The bees he studied could fly only if their internal body temperatures approached 72degrees，yet they were able to forage（覓食） in 54-degree weather．Basking（取暖） in sunlight on the outside of a warm daffodil bloom was enough to get a bee airborne．Heat from flight muscles could then help keep bees in the air，but they still relied on blossom-basking to supplement their heat needs．Although a bee inside a flower has access to warmth and food，a bee basking atop a flower can more effectively raise its temperature by absorbing heat both from direct sunlight and from the flower below．
On those cooler days，bees spent most of their foraging time basking，but"flights between flowers were sometimes interrupted by sudden falls to the ground，"Herrera wrote in his 1995paper．"Fallen bees crawled into some nearby flower and basked before resuming normal foraging．"
（Note：Answer the questions or complete the statements in No MORE THAN 12WORDS．）
81．According to the passage，what can help early pollinators to survive cold weather？Late-winter flowers'extended blooming times．/Late-winter flowers'remaining open for long．
82．Flowers on a south-facing slope usually open earlier because ofhigh/soil/temperature．
83．What does the"good news for small bees"in paragraph 4refer to？The flower can create amicro climate within itselfonce open．/The temperatures inside flowers can be much higher than the surrounding air．
84．A bee can raise its temperature better at the top of a flower because both（direct）sun light and the flower below are its sources of warmth．
舉一反三單元同步過關(guān)卷系列答案