Isaac Newton’s universal law of gravitation is an expansion of the planetary motion ideas developed by Johannes Kepler. One derivative of Newton’s universal law gives us a useful formula to find tidal forces on Earth caused by either the Sun or Moon. The tidal force depends on the mass m of the Sun or Moon, the radius r of Earth, and the cube of the distance d between Earth and either the Sun or Moon. (The G in the equation is known as the gravitational constant, and it doesn’t change.) Based on the equation and your knowledge of the Sun-Earth-Moon system, which celestial body (the Sun or the Moon) has a greater influence on Earth’s tides? Justify your answer.

Which of the following birds remained ancient looking in the miocene epoch? a. crows b. owls c. grouses d. none of the above

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

All eukaryotic cells contain small bodies called