In July 1994 the comet Shoemaker-Levy 9 collided with
the planet Jupiter, as scientists had
predicted. To be able to accurately
predict when a comet will collide with a
planet, it is essential to understand-
A. the composition of a planet's
atmosphere
B. the gravitational attraction that
exists between all bodies
C. the attraction of opposite poles of a
magnet to each other
D. the formation of comets

Read the following scenario to answer the following question. 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. when most populations of a wide-ranging amphibian species are lost and the few remaining populations are widely separated, we expect to see that a. the founder effect becomes increasingly important b. microevolution no longer occurs c. gene flow between populations is reduced d. artificial selection becomes a greater factor in microevolution

Environmental differences within ecosystems are generally caused by

What type of competition exsist between two species. turtles and fish