[填空题]i The biological clock
ii Why dying is beneficial
iii The ageing process of men and women
iv Prolonging your life
v Limitations of life span
vi Modes of development of different species
vii A stable life span despite improvements
viii Energy consumption
ix Fundamental differences in ageing of objects and organisms
x Repair of genetic material

Because of changes in the genetic material (mutations) these have new characteristics and in the course of their individual lives they are tested for optimal or better adaptation to the environmental conditions. Immortality would disturb this system--it needs room for new and better life. This is the basic problem of evolution.

[填空题]i The biological clock
ii Why dying is beneficial
iii The ageing process of men and women
iv Prolonging your life
v Limitations of life span
vi Modes of development of different species
vii A stable life span despite improvements
viii Energy consumption
ix Fundamental differences in ageing of objects and organisms
x Repair of genetic material

Our ’dead’ products are ’static’, closed systems. It is always the basic material which constitutes the object and which, in the natural course of things, is worn down and becomes ’older’. Ageing in this case must occur according to the laws of physical chemistry and of thermodynamics. Although the same law holds for a living organism, the result of this law is not inexorable in the same way.

[单项选择]Passage Four A biological clock is what tells plants, animals, and other organisms how to organize their time. This ‘clock’ helps plants and animals change their routine when they move to places with different climates and environments. Most biological clocks are based on the movement of the sun and follow a twenty-four hour cycle called a circadian rhythm. Some animals sleep only at night, making them diurnal. Animals that sleep during daytime are nocturnal. Flowers are diurnal because they close their petals at night but they open again in the morning. Bats sleep in the daytime so they are nocturnal. Some biological clocks also follow an annual cycle, especially in animals that have annual migrations. Animals that have annual cycles do different things at different times of year. Their actions are determined by the seasons. Different animals can live in the same area when their biological clocks make them look for food at different times of day. This process also
A. human
B. flowers
C. bats
D. cows

[单项选择]

Every living thing has what scientists call a biological clock that controls behavior. The biological clock tells (1) when to form flowers and when the flowers should open. It tells (2) when to leave the protective cocoons and fly away, and it tells animals and human beings when to eat, sleep and wake.
Events outside the plant and animal (3) the actions of some biological clocks. Scientists recently found, for example, that a tiny animal changes the color of its fur (4) the number of hours of daylight. In the short (5) of winter, its fur becomes white. The fur becomes gray brown in color in the longer hours of daylight in summer.
Inner signals control other biological clocks. German scientists found that some kind of internal clock seems to order birds to begin their long migration (6) twice each year. Birds (7) flying become res
A. prevented from
B. helped by
C. intruded on