问题 选择题

在观察蚯蚓运动的实验过程中,需要用滴管不断的往蚯蚓身上滴水,这是为了(  )

A.减小运动时的摩擦,以便于观察

B.不断的给蚯蚓刺激,促使其运动以便于观察

C.便于刚毛在运动中发挥作用

D.使体表保持湿润,进行呼吸

答案

蚯蚓呼吸的是空气中的氧气,氧气先溶解在体壁的粘液里,然后渗透到体壁内的毛细血管中的血液里,血液中的二氧化碳也通过体壁排出体外.因此蚯蚓是用湿润的体壁进行呼吸的.所以,观察蚯蚓时,要经常用浸水的棉球轻轻擦蚯蚓的体表,使体表保持湿润,其目的是维持蚯蚓的正常呼吸.

故选:D

选择题
单项选择题

You really do have to wonder whether a few years from now we’ll look back at the first decade of the 21st century—when food prices spiked, energy prices soared, world population surged, tornados plowed through cities, floods and droughts set records, populations were displaced and governments were threatened by the confluence of it all—and ask ourselves. What were we thinking How did we not panic when the evidence was so obvious that we’d crossed some growth, climate, natural resource and population redlines all at once "The only answer can be denial," argues Paul Gilding, an Australian environmentalist, in a new book called The Great Disruption. "When you are surrounded by something so big that requires you to change everything about the way you think and see the world, then denial is the natural response. But the longer we wait, the bigger the response required."

Gilding cites the work of the Global Footprint Network, an alliance of scientists, which calculates how many "planet Earths" we need to sustain our current growth rates. G. F. N. measures how much land and water area we need to produce the resources we consume and absorb our waste, using prevailing technology. On the whole, says G. F. N. , we are currently growing at a rate that is using up the Earth’s resources far faster than they can be sustainably replenished, so we are eating into the future.

This is not science fiction. This is what happens when our system of growth and the system of nature hit the wall at once. We are now using so many resources and putting out so much waste into the Earth that we have reached some kind of limit, given current technologies. The economy is going to have to get smaller in terms of physical impact.

We will not change systems, though, without a crisis. But don’t worry, we’re getting there. We’re currently caught in two loops: One is that more population growth and more global warming together are pushing up food prices, causing political instability in the Middle East, which leads to higher oil prices, thus to higher food prices and more instability. At the same time, improved productivity means fewer people are needed in every factory to produce more stuff. So if we want to have more jobs, we need more factories. More factories making more stuff make more global warming, and that is where the two loops meet.

But Gilding is actually an eco-optimist. As the impact o the imminent Great Disruption hits us, he says, "our response will be proportionally dramatic, mobilizing as we do in war. We will change at a scale and speed we can barely imagine today, completely transforming our economy, including our energy and transport industries, in just a few short decades. " We will realize, he predicts, that the consumer-driven growth model is broken and we have to move to a more happiness-driven growth model, based on people working less and owning less.

It can be inferred that the happiness-driven growth model is characterized by()

A. higher economic productivity

B. slower economic growth

C. less dramatic political change

D. constant technological innovations