this cross, the F, generation, to self-pollinate, and then calculated the phenotypic ratios that he observed in the F2 offspring. From his monohybrid crosses, Mendel developed his first law, the This law states that each parent organism has two copies of cach discrete unit, or and that the two copies separate from each other during Mendel then performed dihybrid crosses, and as a result, developed his second law, the This law states essentially that the inheritance of one trait does not influence the inheritance of another trait. Man of Houghton Mifflin Company Mendel's second law applies to genes that are on separate chromosomes or to genes that are so far apart on the same chromosome that they have a strong chance of being separated by However, his second law does not apply to genes that exhibit because they are close together on the same chromosome. Unescue Bot www Vocabulary Practice 33

Over the past 60 years, many amphibian species have experienced significant population declines and some species have become extinct. scientists suspected that local human activities such as the destruction of wetlands, regional pollution, and deforestation were the main reasons for these losses. however, research over the past 20 years reveals significant amphibian population declines in protected areas of the world, such as nature preserves and parks. these global declines suggest widespread problems including increased ultraviolet radiation, acid rain, and disease. in switzerland, for example, 14 of the 20 native amphibian species are threatened with extinction. chytridiomycosis is a fungal disease first identified in 1998 as a cause of massive amphibian deaths. in some severely impacted populations, a few individuals have survived, perhaps because of some natural resistance. if these resistant individuals continue to survive and prosper, new resistant populations might emerge. this would be an example of the founder effect artificial selection genetic drift natural selection sexual selection

Development of new communities in disturbed environments, such as a burned or a clear cut forest, is called

This part insulates the reaction chamber from the transfer of heat to or from the surrounding environment