Earth teems with a staggering variety of animals, including 9,000 kinds of birds, 28,000 types of fish, and more than 350,000 species of beetles. What explains this explosion of living creatures—1.4 million different species discovered so far, with perhaps another 50 million to go? The source of life's endless forms was a profound mystery until Charles Darwin brought forth his ... (展开全部)
免责声明:本网站所刊载信息,不代表本站观点。所转载内容之原创性、真实性、完整性、及时性本站不作任何保证或承诺,请读者仅作参考并自行核实。