[填空题]The short-lived, rapidly dispersed species are often called ______.

[填空题]The short-lived, rapidly dispersed species are often called ______.

[填空题]Plant species are dispersed over a large area with the help of ______.

[单项选择]Endangered Species 　　Endangered species are plants and animals that are in immediate danger of extinction. Extinction is actually a normal process in the course of evolution. Since the formation of the earth, many more species have become extinct than those exist today. These species slowly disappeared because of change of climate and their failure to adapt to such conditions as competition and predation. Since the 1600s, however, the process of extinction has greatly accelerated as a result of both human population growth and technological encroachment on natural ecology systems. Today the majority of the world’s environments are changing faster than the ability of most species to adapt to such changes through natural selection. 　　Species become extinct or endangered for number of reasons, but the primary cause is the destruction of natural habitats. Drainage of wetlands, cutting and clearing of forests, growth of cities, and highway and dam construction have seriously reduced avail
A. Human beings are not aware of the importance of preserving endangered species.
B. Some endangered species have already reached the end of their life span in evolution.
C. The development of human society has greatly affected natural ecology systems.
D. The world’s climate has changed greatly that most species cannot survive.

[填空题]Like all animal species, plant species must spread their offspring to suitable areas
where they can grow and pass on their parent’s genes. Young animals generally spread by (1) ______
walking or flying. Because plants don’t have that ability, they may somehow hitchhike. (2) ______
Some plant seeds scatter by blowing in the wind or floating on water. Many other plant
species, though, trick an animal into carrying their seeds. How do they do They enclose
them within a tasty fruit and advertise the fruit’ s ripeness by its color or smell. The hungry
animal collects and swallows the fruit, walks or flies off, but later spits out the seeds some- (3) ______
where far from its parent tree. Seeds can thereby be carried thousands of mi]es. It may (4) ______
surprise you to learn that plant seeds can resist digestion. In fact, some seeds actually
require passage through an animal’ s body before they can grow. Wild strawberries offer a
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