Now let's look ourselves as a species in relation to ecosystem balance.Modern scientists believe that humankind, like other animals, evolved(进化) through millions of years of changes and adaptations to the environment and that our most direct evolutionary ancestor was probably an earlier species of the primate(monkey, ape) group. Despite this similarity with other creatures, however, the evolution of humankind differs from that of other species in one important and unique way.
In other species, evolution has led to specialization, both in the species abilities and in its place within the environmental structure. For example, the giraffe is much adapted to feeding on treetops, but it is also specialized and thus limited to feeding on trees and shrubs. Only with great difficulty can it bend down to graze on the ground. Similarly, the anteater is extremely well adapted to eating ants but is unable to catch or eat other animals. The same is true for countless other species.
For humankind it is opposite. Our evolution had led to a very generalized ability. Our highly developed intelligence and ability to make and handle tools mean that we can do almost anything. Humans evolved in such a way that we are able to move into every environment on Earth and even into space. No natural competitor offers great resistance, and other natural enemies such as disease have been controlled.
Said another way, we see in humankind a great imbalance between biological potential and environmental resistance. The result is the rapidly increasing world population, frequently referred to as the population explosion. Further, to support our growing population, natural ecosystems are being increasingly displaced by human habitations, agriculture, and other human supporting activities.
From the passage we can infer that in the course of evolution _______.

A．humankind is very important to earlier species, such as the primate group

B．human beings are limited by the environment while animals are not

C．human beings become more and more different from each other

D．humankind has experienced a generalization rather than specialization in ability

According to the passage, primate includes such animals as _______.

A．monkeys and anteaters	B．tigers and apes
C．apes and monkeys	D．monkeys and giraffes

According to the passage, evolution has made it possible for humans to _______.

A．increase the population

B．resist natural offers

C．go to the moon

D．cure all diseases

According to the author, imbalance between biological potential and environ mental resistance has resulted in _______.

A．the population explosion

B．the destruction of human habitations

C．the growth of natural ecosystem

D．the specialization of humans