You might know that the domesticated (驯化的) dogs came from wolves. But you might not know how this process of transformation occurred. Wolves domesticated themselves 【小题1】 (actual).

Surprisingly, wolves were domesticated not by the selection of humans, but by the 【小题2】 (amaze) adaptation of the wolves themselves to the human settlements that provided them with food. This made 【小题3】 advantageous for wild wolves to be friendly to humans, as the friendly wolves got more food and bred more. Eventually, those friendly wolves became what we know 【小题4】 dogs.

But while they gained safety and food, they lost independence. For example, if a dog 【小题5】 (present) with a locked box, it will look for human help, while a wolf will attempt 【小题6】 (open) it. And that’s not all that changed about the animal; this process even transformed their appearance.

Experiments on foxes in Siberia have found a genetic link between 【小题7】 (friendly) and floppy ears and curled tails. The friendly foxes were those most selected by humans, and therefore had more offspring, 【小题8】 (make) floppy ears and curly tails more common.

However, 【小题9】 we know about domestication is still quite limited. Just think of how some people assume dogs are stupid because they are loyal even when 【小题10】 (abuse). The truth is that the dog simply knows that being loyal to the one that feeds it will help it survive.

Some deer in Minnesota rely on a team of bats to eat up biting flies 【小题1】 typically trouble them. Researchers observed this 【小题2】 (previous) unknown symbiotic (共生的) relationship between white-tailed deer and an unidentified bat species at the Cedar Creek Ecosystem Science Reserve.

“These bats appear 【小题3】 (attract) by all the flies around the deer,” says study leader Meredith Palmer. Symbiotic relationships between mammals (哺乳动物) and birds are better known, she says, but “【小题4】 is very rare for mammals to help each other like this.’’

This bat-deer 【小题5】 (associate) is a positive interaction that benefits at least one, perhaps even both 【小题6】 (partner). Bats may save search time and energy by 【小题7】 (feed) on the flies, and this feeding could bring the deer much needed relief in the summer months. The study 【小题8】 (publish) in March in Ethology.

Craig Willis, a biology professor at the University of Winnipeg in Manitoba, says, “If the bats are reducing biting insects for deer, maybe they can also do the same for humans.”

Ecological research seldom 【小题9】 (focus) on the positive ways in which animals help one another, Palmer notes. 【小题10】 it comes to beneficial symbiotic relationships, she says, “there’s just a big gap out there.”

The Northeast China Tiger and Leopard National Park, bordering Russia and the North Korea, 【小题1】 (cover) an area of 14,100 square kilometers. It is the major habitat of the country’s Siberian tigers and Amur leopards and is 【小题2】 model for cross-border wildlife conservation.

Located in the central zone of the mixed coniferous (针叶的) and broad-leaved forest ecosystems in the temperate (温带的) zone of Asia, the park possesses splendid and attractive scenery 【小题3】 different seasons. In addition, there are plentiful plant species well 【小题4】 (preserve) in the park, including thousands of medical plants, eatable wild herbs, wild fruit trees and bushes. Some of them are 【小题5】 (endanger) plant species and under state protection.

The park is a perfect place for the reproduction and 【小题6】 (survive) of birds. Every spring, various forest birds start returning from the south to prepare 【小题7】 (lay)eggs. The rich soil of the park also provides a favorable living environment for cold-blooded animals. At present, a community of flesh-eating animals and a community of plant-eating animals make up a complete food chain in the national park, 【小题8】 is extremely rare to see in China. The national park will 【小题9】 (effective) protect Siberian tigers and Amur leopards, 【小题10】 (help) them continue to reproduce and live in harmony with nature.