Single mums are better at raising their kids than two parents 一 at least in the bird world. Mother zebra finches ¹ have to work harder and raise fewer chicks on their own，but they also produce more attractive sons who are more likely to get a mate.

    The finding shows that family conflict is as important an evolutionary driving force as ecological factors 2 such as hunting and food supply. With two parents around, there"s always a conflict of interests 3，which can have a detrimental effect on the quality of the offspring.

    In evolutionary terms 4，the best strategy for any parent in the animal world is to find someone else to care for their offspring，so they can concentrate on breeding again. So it"s normal for parents to try to pass the buck 5 to each other. But Ian Hartley from the UniversityofLancasterand his team wondered how families solve this conflict, and how the conflict itself affects the offspring.

    To find oiit 6，they measured how much effort zebra finch parents put into raising their babies. They compared single females with pairs, by monitoring the amount of food each parent collected, and removing or adding chicks so that each pair of birds was raising four chicks，and each single mum had two — supposedly the same amount of work.

    But single mums, they found, put in about 25 per cent more effort than females rearing with their mate. To avoid being exploited, mothers with a partner hold back from working too hard if the father is being lazy, and it"s the chicks that pay the price. “The offspring suffer some of the cost of this conflict, ” says Hartley.

    The cost does not show in any obvious decrease in size or weight, but in how attractive they are to the opposite sex. When the chicks were mature, the researchers tested the ” fitness" of the male offspring by offering females their choice of partner. Those males reared by single mums were chosen more often than those from two-parent families.

    Sexual conflict has long been thought to affect the quality of care,given to offspring, says zoologist Rebecca Kilner atCambridgeUniversity, who works on conflict of parents in birds. ” But the experimental evidence is not great. The breakthrough here is showing it empirically. ”

    More surprising, says Kilner, is Hartley"s statement that conflict may be a strong influence on the evolution of behaviour, clutch size and even appearance. “People have not really made that link," says Hartley. A female"s reproductive strategy is usually thought to be affected by hunting and food supply. Kilner says conflict of parents should now be taken into account as well.

词汇：

evolutionary /,i: və"lu:ʃənəri/adj．进化的

detrimental /detrimentəl/adj．有害的

offspring /"ɔfspriŋ/n．（单复数同形）儿女，子孙，后代

empirically /em"pirikli/adv．以经验为根据地

ecological /i:kə"lɔdʒikəl/adj．生态的

reproductive /,ri:prədʌktiv/adj．生殖的

experimental /eks,peri"mentəl/adj．实验的，根据实验的

clutch /klʌtʃ/ n．一次产的或孵的卵

注释：

1.zebra finch：斑胸草雀，一种澳大利亚小鸟，它有黑白色条纹，而且是受欢迎的笼养鸟。

2.family conflict is as important an evolutionary driving force as ecological factors：家庭冲突是与生态因素同样重要的进化推动力。

3.a conflict of interests：利益冲突

4.in evolutionary terms：从进化的角度讲。in... terms, in terms of...：从……方面来讲，就……而言。例如：It has been a terrible year in terms. of business．就生意而论，这是很糟糕的一年。

5.pass the buck (to)：推卸责任，把为难的事推给别人。例如：Bus companies are just passing the buck by saying their drivers are responsible for delays．公交公司说司机应该对误点的事负责，这只是在推卸责任。

6.find out：这是一个承上的短语，从逻辑上讲，它的宾语应该是：how families solve this conflict, and how the conflict itself affects the offspring.  

According to the passage, in what way does family conflict affect the quality of the offspring?

A:The young males get less care B:The young females will decrease in weight C:The offspring will become lazy fathers or mothers in the future D:The offspring will not get mature easily

The larger a machine and the more numerous its parts, the greater likelihood of a breakdown and the more expensive to repair. What has been said about market forces and management was necessarily oversimplified. The economies of modern industrial nations are large and very complex. To be sure, there is management, and there are market forces at work, but there are also many other factors that help or hinder economic function.
In modern industrial societies, governments play a large role. There is a great amount of regulation, most of it meant for the protection of the public. All regulations affect the way businesses operate, often increasing their costs and reducing their profits. Lower profits, in turn, reduce the amount of money which is known as working capital that a company can use for expansion. Auto emission standards, for instance, have had a significant impact on the manufacture and pricing of automobiles. Other government policies such as taxation, budget deficits, and regulation of the money supply have an effect on how much money is available for people to spend on goods and services.
International crises and other conditions also affect the working of an economy. A severe frost in Brazil can ruin a coffee crop and raise the price of that commodity. War can cut off the supply of such resources as petroleum, chromium, or copper. In the United States environmental protests have slowed the development of nuclear energy capacity and the mining of vast tracts of protected land. Weather affects agriculture, a hot, dry summer can damage the wheat crop; floods can destroy thousands of acres of crops suddenly; and insect pests can devastate cropland with a rapid onslaught.
People’s attitudes also have an impact on the marketing of goods. Health-conscious individuals, for example, may stop smoking, curtail their intake of alcohol, and eat less of certain kinds of food. Advertising affects what people buy, and it can create a market where none existed. Style and fashion are significant for many consumers.
There are other economic problems that are more difficult to understand. For centuries economies have been subject to periods of prosperity followed by periods of decline. Although periods of prosperity can be explained rather easily, the reasons for panics, recessions, and depressions are of a complex nature. So many factors contributed to the Great Depression of the 1930s, for example, that no economist has ever been able to account for all of them.
Because the causes of decline are uncertain, the remedies are equally uncertain. In the late 20th century all industrialized societies through their governments have tried to stabilize economies, keep them prosperous, and reduce unemployment. None of the remedies has worked to the extent that was hoped. How economies work and what remedies can be found to keep them operating efficiently are the tasks of economists, who must work together with businessmen and politicians.
The chief purpose of the passage is ______.

A:to review the factors that affect economic operation B:to explore the causes of periodic economic decline C:to discuss the role governments play in modern industrialized societies D:to propose remedies for correcting economic recessions

The larger a machine and the more numerous its parts, the greater likelihood of a breakdown and the more expensive to repair. What has been said about market forces and management was necessarily oversimplified. The economies of modern industrial nations are large and very complex. To be sure, there is management, and there are market forces at work, but there are also many other factors that help or hinder economic function.
In modern industrial societies, governments play a large role. There is a great amount of regulation, most of it meant for the protection of the public. All regulations affect the way businesses operate, often increasing their costs and reducing their profits. Lower profits, in turn, reduce the amount of money which is known as working capital that a company can use for expansion. Auto emission standards, for instance, have had a significant impact on the manufacture and pricing of automobiles. Other government policies such as taxation, budget deficits, and regulation of the money supply have an effect on how much money is available for people to spend on goods and services.
International crises and other conditions also affect the working of an economy. A severe frost in Brazil can ruin a coffee crop and raise the price of that commodity. War can cut off the supply of such resources as petroleum, chromium, or copper. In the United States environmental protests have slowed the development of nuclear energy capacity and the mining of vast tracts of protected land. Weather affects agriculture, a hot, dry summer can damage the wheat crop; floods can destroy thousands of acres of crops suddenly; and insect pests can devastate cropland with a rapid onslaught.
People’s attitudes also have an impact on the marketing of goods. Health-conscious individuals, for example, may stop smoking, curtail their intake of alcohol, and eat less of certain kinds of food. Advertising affects what people buy, and it can create a market where none existed. Style and fashion are significant for many consumers.
There are other economic problems that are more difficult to understand. For centuries economies have been subject to periods of prosperity followed by periods of decline. Although periods of prosperity can be explained rather easily, the reasons for panics, recessions, and depressions are of a complex nature. So many factors contributed to the Great Depression of the 1930s, for example, that no economist has ever been able to account for all of them.
Because the causes of decline are uncertain, the remedies are equally uncertain. In the late 20th century all industrialized societies through their governments have tried to stabilize economies, keep them prosperous, and reduce unemployment. None of the remedies has worked to the extent that was hoped. How economies work and what remedies can be found to keep them operating efficiently are the tasks of economists, who must work together with businessmen and politicians.
The example of auto emission standards is here used to make it clear that ______.

A:it is harmful for a government to interfere with economic matters B:state policies tend to lower profits and discourage investment C:regulation may affect business operation by increasing the cost D:most regulations are not meant for the protection of the public

The rising unemployment may ______ affect the growth of economy.

A:favorably B:effectively C:greatly D:adversely

What may affect the accuracy of sounding with echo sounder?

A:Sea bottom B:Ship's speed C:Speed of current D:Water temperature and density

Which of the followings will affect the spray of fuel oil?

A:coke deposits B:cylinder water temperature C:asphalt in fuel oil D:lub oil

"______is not an external factorsthat affect manoeuvring of a ship that moves along the approach channels

A:The width B:The depth C:The alignment D:The draught"

______ is not a factor which will affect the accuracy of GPS receiver．

A:detective Availability B:local environmental conditions C:autonomous（自主式） mode versus differential correction mode versus RTCM mode D:the averaging of recorded locations"