The illustration below shows simplified models of two different circulatory systems.

Diagram at left shows a single loop of blood vessels, including a heart with 1 ventricle and 1 atrium and two capillary beds. At right, a heart with 2 ventricles and 2 atria, and a double loop of blood vessels to two capillary beds.

In both models, which is one way that the real circulatory system is more complex than the model shows?

A. The heart has several additional chambers for receiving and pumping blood.
B. Arteries and veins divide and branch many times to serve all of the body capillaries.
C. A capillary bed interfaces with the digestive system, where gas exchange occurs.
D. Twenty wide arteries extend directly from the heart, each carrying blood to a separate capillary bed.

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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

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