Even if we have an extremely healthy diet and lifestyle, the human body is programmed to wear out at a maximum of about 120 years, and usually less. We all have a biological clock inside us which determines the moment when our organs cease to function properly. This is because our cells have stopped renewing themselves and our body can no longer repair itself. This is also the moment when we are more likely to begin to suffer from the diseases of old age such as arthritis and Alzheimer’s. However, rapid advances in DNA research are beginning to throw light on the secrets of the ageing process. By the end of this century we could literally have the power of life over death.
Although it has long been accepted that humans have a fixed lifespan, it is also a fact that certain other organisms, such as reptiles and amphibians, appear to live indefinitely. The only reason we do not see 500-year-old alligators is because in the wild their lives are always in danger, from man, from pollution and from other animals. When they are kept in zoos they do not seem to age at all after they are fully grown. The same is true of some species of fish, which grow indefinitely and show no signs of ageing. The existence of animals with no fixed lifespan seems to indicate that an age gene really does exist. It is this gene which scientists are searching for, which may delay or repair damage to the body caused by ageing.
Another new area of research involves the oxidation（氧化） theory, which says that ageing is caused by the same process that makes iron rust. In controlled experiments, the lifespans of certain animals were shown to be lengthened with anti-oxidants; for example, the lifespan of mice can be increased by 30%. Antioxidants are already being used in face creams and other cosmetics, and they are likely to play an important part in keeping people physically young.
Perhaps the most immediate advance we are likely to see in the battle to halt（停止）the ageing process will be organ replacement. By the year 2020 it is likely that we will be replacing injured bones or even organs like livers and kidneys with ones “grown” in laboratories. By 2050 perhaps every organ in the body, except the brain, will have become commercially available. Recent experiments also show that it may one day be possible to “grow” new organs inside our body to replace worn-out ones, something which lizards and alligators already do.
Suddenly immortality（不死，不朽） seems within reach. We can begin to imagine a future where we are born, we grow to maturity, but we never grow old and die. But do we really want to live forever?
【小题1】 When all humans reach a certain age,         .

A．they suffer the effects of their diet and lifestyle

B．the organs stop to perform appropriately

C．their cells continue to renew themselves

D．they develop arthritis and Alzheimer’s

【小题2】 The purpose of showing the case of alligators is to prove         .

A．alligators are in danger in the wild because of the threat from man, pollution and other animals

B．it is widely accepted that humans have a fixed lifespan

C．there exists an age gene which may control ageing

D．the age gene damages the body

【小题3】The underlined phrase “live indefinitely” in Paragraph 2 probably mean         .

A．live for a period of time without a fixed end

B．live without a clear aim

C．live in an uncertain way

D．live without being fully grown

【小题4】It can be inferred from Paragraph 4 that         .

A．by 2050 we might have most of our worn-out organs replaced with new ones commercially

B．never can the ageing process be avoided

C．livers and kidneys are sure to be grown in laboratories by the year 2020

D．lizards and alligators grow new organs inside their body to replace worn-out ones

【小题5】 What is the main topic of this passage?

A．DNA researches show how our cells renew themselves.

B．Anti-oxidants are likely to play an important part in keeping people young.

C．How our biological clock works?

D．Eternal（永恒的） youth: new developments in anti-ageing research.

【小题6】By saying “But do we really want to live forever”, the author may probably mean         .

A．a future where we are born, we grow to maturity, but we never grow old and die is on its way

B．he is uncertain whether we can live forever

C．it remains to be seen whether immortality is a blessing or a curse

D．immortality is no longer a dream

Even if we have an extremely healthy diet and lifestyle, the human body is programmed to wear out at a maximum of about 120 years, and usually less. We all have a biological clock inside us which determines the moment when our organs cease to function properly. This is because our cells have stopped renewing themselves and our body can no longer repair itself. This is also the moment when we are more likely to begin to suffer from the diseases of old age such as arthritis and Alzheimer’s. However, rapid advances in DNA research are beginning to throw light on the secrets of the ageing process. By the end of this century we could literally have the power of life over death.

Although it has long been accepted that humans have a fixed lifespan, it is also a fact that certain other organisms, such as reptiles and amphibians, appear to live indefinitely. The only reason we do not see 500-year-old alligators is because in the wild their lives are always in danger, from man, from pollution and from other animals. When they are kept in zoos they do not seem to age at all after they are fully grown. The same is true of some species of fish, which grow indefinitely and show no signs of ageing. The existence of animals with no fixed lifespan seems to indicate that an age gene really does exist. It is this gene which scientists are searching for, which may delay or repair damage to the body caused by ageing.

Another new area of research involves the oxidation（氧化） theory, which says that ageing is caused by the same process that makes iron rust. In controlled experiments, the lifespans of certain animals were shown to be lengthened with anti-oxidants; for example, the lifespan of mice can be increased by 30%. Antioxidants are already being used in face creams and other cosmetics, and they are likely to play an important part in keeping people physically young.

Perhaps the most immediate advance we are likely to see in the battle to halt（停止）the ageing process will be organ replacement. By the year 2020 it is likely that we will be replacing injured bones or even organs like livers and kidneys with ones “grown” in laboratories. By 2050 perhaps every organ in the body, except the brain, will have become commercially available. Recent experiments also show that it may one day be possible to “grow” new organs inside our body to replace worn-out ones, something which lizards and alligators already do.

Suddenly immortality（不死，不朽） seems within reach. We can begin to imagine a future where we are born, we grow to maturity, but we never grow old and die. But do we really want to live forever?

1. When all humans reach a certain age,         .

A．they suffer the effects of their diet and lifestyle

B．the organs stop to perform appropriately

C．their cells continue to renew themselves

D．they develop arthritis and Alzheimer’s

2. The purpose of showing the case of alligators is to prove         .

A．alligators are in danger in the wild because of the threat from man, pollution and other animals

B．it is widely accepted that humans have a fixed lifespan

C．there exists an age gene which may control ageing

D．the age gene damages the body

3.The underlined phrase “live indefinitely” in Paragraph 2 probably mean         .

A．live for a period of time without a fixed end

B．live without a clear aim

C．live in an uncertain way

D．live without being fully grown

4.It can be inferred from Paragraph 4 that         .

A．by 2050 we might have most of our worn-out organs replaced with new ones commercially

B．never can the ageing process be avoided

C．livers and kidneys are sure to be grown in laboratories by the year 2020

D．lizards and alligators grow new organs inside their body to replace worn-out ones

5. What is the main topic of this passage?

A．DNA researches show how our cells renew themselves.

B．Anti-oxidants are likely to play an important part in keeping people young.

C．How our biological clock works?

D．Eternal（永恒的） youth: new developments in anti-ageing research.

6.By saying “But do we really want to live forever”, the author may probably mean         .

A．a future where we are born, we grow to maturity, but we never grow old and die is on its way

B．he is uncertain whether we can live forever

C．it remains to be seen whether immortality is a blessing or a curse

D．immortality is no longer a dream

 

Most animals have 1ittle connection with animals of different kind．unless they hunt them for food．Sometimes，however，two kinds of animals come together in a partnership(伙伴关系) which does good to both of them．You may have noticed some birds sitting on the backs of sheep．This is not because they want a ride，but because they find easy food in the parasites(寄生虫) on sheep．The sheep allow the birds to do so because they remove the cause of discomfort．So although they can manage without each other，they do better together．

Sometimes an animals has a plant partner．The relationship develops until the two partners cannot manage without each other．This is so in the corals(珊瑚) of the sea．In their skins they have tiny plants act as “dustman”，taking some of the waste products from the coral and giving in return oxygen(氧气)which the animal needs to breathe．If the plants are killed，or are even prevented from light so that they cannot live normally(正常地)，the corals will die．

1．Some birds like to sit on a sheep because____________．

　 A．they can eat its parasites

　 B．they depend on the sheep for existence

　 C．they enjoy travelling with the sheep

　 D．they find the position most comfortable　

2．The underlined word “they” in last sentence of the first paragraph refers to_____________．

　 A．birds and parasites

　 B．birds and sheep

　 C．parasites and sheep

　 D．sheep, birds and parasites

3．It can be learnt from the text that the coral depends on the plant for________．

　 A．comfort　　 B．light　　 C．food　　　 D．oxygen

4．What does the second paragraph mainly discuss?

　 A．Some animals and plants depend on each other for existence

　 B．Some animals and plants develop their relationship easily．

　 C． Some plants depend on each other for food．

　 D．Some animals live better together．

5．What does this article talk about?

　 A．Two kinds of animals form a partnership．

　 B. Most animals only have connection with animals．

　 C．The connection between the living things．

　 D．Corals have some connection with plants．