It is important to study polar bears to assess the health of the ecosystem on the Arctic, because（） A: they are on the edge of extinction. B: they are on the top of the ecosystem. C: the food chain on the Arctic depends on them. D: there are no other big animals on the Arctic.

What are the characteristics of a food chain? A: It is made up of 3 to 5 links. B: It begins with a green plant, belonging to the producer of ecosystem. C: Other links are usually predatory animals, belonging to the consumers of ecosystem D: The carrot, the corn and the trees are usually producers.

The return of a biome/habitat to its original condition is also called A: restoration ecology. B: ecosystem maintenance. C: ecosystem replacement. D: ecosystem restoration. E: ecosystem rehabilitation.

Mount.Huangshan has limited resources in ecosystem.

Mercury is a metal pollutant that can disrupt the ecosystem. Why is mercury so disruptive to the ecosystem? A: Organisms excrete the mercury out as waste. B: Organisms use mercury as an enzyme to speed up reactions in an organism's body. C: Mercury slows down the respiration rates of primary consumers. D: Mercury can become concentrated in the tissues of organisms.

Study shows that excessive use of _____ may damage the ecosystem.

什么是生态系统(ecosystem)？

The Windows Store app ecosystem of Windows 10 can run ________.

_________ environmental damage is done, it takes many years for the ecosystem (生态系统) to recover.

The main body of the community ecosystem business model value creationthe is community.