Sequences in mrna, such as uga, uaa, or uag, that tell a ribosome when to stop making a new protein are known as

Which phrase best describes surface currents? 1. up-and-down ocean movement caused by wind 2. waves that hit the shore at an angle and transport sand 3. streams of warm water flowing through the ocean and caused by wind 4. waves that approach the shore and cause their crests to fall into their troughs

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

Why is it important to reduce the number of chromosomes in half when forming gametes for sexual reproduction?