问题 问答题

有一位同学在做模拟酸雨影响植物种子的萌发实验。

提出的问题是:酸雨对种子的萌发有影响吗?

作出的假设是:酸雨使种子不能萌发。

他用食醋和清水配制成了“模拟酸雨”,并且把PH值控制在4.0以下。

他设计的方案是:

①在培养皿底部垫上几层吸水纸,加入少量的水使纸湿润,在纸上放10粒大豆种子,种子上面覆盖潮湿的纱布,把培养皿放在温暖的地方培养。

②每天在纱布上淋几次“模拟酸雨”。

③观察大豆的发芽状况。

④换用其他几种的种子进行同样的实验。

请回答:

(1)如果这些种子都没有发芽,就能说明是酸雨的影响吗?为什么?

(2)请你帮他完成设计。 

(3)结合所学知识谈谈酸雨对生物的危害。

答案

(1)不能说明,影响种子的萌发的条件很多,如种子要有完整的,有生命力的肧;种子萌发的外界条件是适宜的温度,充足的空气和足够的水。

(2)设计的方案必须是对照实验,种子数量要100粒,多做几组实验且符合种子萌发的条件。(答案合理即可)

(3)酸雨的危害很多:酸雨对人眼和呼吸道产生刺激作用;酸雨降落到地面,会影响农作物的生长,可使水呈现酸性,影响鱼类和水生植物等的生长,腐蚀建筑物,雕塑等。(答案合理即可)

多项选择题
单项选择题

Most towns up to Elizabethan times were smaller than a modern village and each of them was built around its weekly market where local produce was brought for sale and the town folks sold their work to the people from the countryside and provided them with refreshment for the day. Trade was virtually confined to that one day even in a town of a thousand or so people. On market days craftsmen put up their stalls in the open air whilst on one or two other days during the week the townsman would pack up his loaves, or nails, or cloth, and set out early to do a day’s trade in the market of an adjoining town where, however, he would be charged a heavy toll for the privilege and get a less favourable spot for his stand than the local craftsmen. Another chance for him to make a sale was to the congregation gathered for Sunday morning worship. Although no trade was allowed anywhere during the hours of the service (except at annual fair times), after church there would be some trade at the church door with departing country folk.

The trade of markets was almost wholly concerned with exchanging the products of the nearby countryside and the goods sold in the market but particularly in food retail dealing was distrusted as a kind of profiteering. Even when there was enough trade being done to afford a livelihood to an enterprising man ready to buy wholesale and sell retail, town authorities were reluctant to allow it.

Yet there were plainly people who were tempted to “forestall the market” by buying goods outside it, and to “regrate” them, that is to resell them, at a higher price. The constantly repeated rules against these practices and the endlessly recurring prosecutions mentioned in the records of all the larger towns prove that some well-informed and sharp-witted people did these things.

Every town made its own laws and if it was big enough to have craft guilds, these associations would regulate the business of their members and tried to enforce a strict monopoly of their own trades. Yet while the guild leaders, as craftsmen, followed fiercely protectionist policies, at the same time, as leading townsmen, they wanted to see a big, busy market yielding a handsome revenue in various dues and tolls. Conflicts of interest led to endless, minute regulations, changeable, often inconsistent, frequently absurd. There was a time in the fourteenth century, for example, when London fishmongers were not allowed to handle any fish that had not already been exposed for sale for three days by the men who caught it.

Craftsmen might prefer to trade in their own town because()

A. there they could easily find good refreshment

B. there they could work in the open air

C. there they could start work very early

D. there they could have the well-placed stalls