未知题型 为了研究鸡的卵泡(egg follicle)数目的差异是否与遗传有关,是否能够通过鸡的产蛋量预测卵泡的数目,得到了如下的实验数据: 计算相关系数(correlation coefficient)。对上述数据作图,计算回归曲线的斜率以及y轴的截距,在同一个坐标图上画出回归曲线。
单项选择题 The Exploding Lakes of Cameroon What comes to mind when youthink of a lake? You probably imagine a pretty scene with bue water, brds, and fish. FOr the people in the northwestern Cameroon, however,the image is very different. For them, lakes may mean terdble disasters. In 1984,poisonous gases exploded out of Lake Monoun and came down into the nearby villages,killing thirty-seven people. Two years later, Lake Nyos erupted. A cloud of gases rolled down the hills and into the valleys and killed 1,700 people.Lake Nyos and Lake Monoun are crater (火山口) lakes. They were formed when water collected in the craters of old volcanoes. The volcanoes under Lake Nyos and Lake Monoun are not active anymore. However, poisonous gases from the center of the earth continue to flow up through cracks in the Bottom of the lake. This is normal in a crater lake.In most crater lakes, these gases are released often because the water 'turns over'regularly. That is, the water from the B.ottom of the lake rises and mixes with the water at the top, allowing the gases to escape slowly.However, in Lakes Nyos and Monoun, there is no regular turning over. No one knows the reason for this fact, But as a result, these lakes have more gases trapped at the bottom than other crater lakes. In fact, scientists who have studied Lakes Nyos and Monoun have found 16,000 times more gases. When a strong wind, cool weather, a storm, or a landslide(滑坡) causes the water to turn over suddenly, the gases escape in a violent explosion.In the past, no one knew when the gases might explode, so there was no way for the Villagers to escape disaster. Now scientists from the United States, France, and Cameroon have found a way to reduce the gas pressure at the bottom of Lake Nyos.They stood a 672-foot plastic pipe in the middle of the lake, with one end of the pipe near the bottom and the other end in the air. Near the top of the pipe, the team put several holes that could be opened or closed by a computer. Now, when the gas pressure gets too high, the holes are opened and some of the gas-filled water shoots up through the pipe into the air like a fountain. With less pressure, a disastrous explosion is much less likely. However, the scientists are not sure that one pipe will be enough to prevent explosions. They hope to put in others soon and they plan to install a similar pipe and a computer system at Lake Monoun as well.To protect people nearB.y until all of the pipes are in place, the scientists have installed early warning systems at both lakes. If the gas pressure rises to a dangerous level, computers will set off loud sirens(警报) and bright lights to warn the people in the villages. That way, they will have time to escape from the dangerous gases. 第 41 题 What will happen when Lake Nyos and Lake Monoun explode?A.Water will flow down the hills.B.Poisonous gases will bereleased suddenly. C.A strong wind will rise from the lakes.D.The volcanoes will come to life.
未知题型 在一个大的牛群中,检测了3个表现连续分布的不同表型特征,它们的方差如下表: (1)计算上述性状的广义遗传率和狭义遗传率。 (2)哪个性状与选择最为相关?为什么? (3)计划减少牛群中的平均脂肪含量,目前这个值为10.5%。脂肪含量为6.5%的亲本杂交得到的后代中平均脂肪含量为多少?