If a person has lost a significant amount of blood but still maintains a normal blood pressure it does not necessarily mean that the person is maintaining adequate perfusion. which of the following best explains why this is so?
blood vessels are constricting causing greater peripheral resistance.
the heart has increased its rate to increase cardiac output.
the sympathetic nervous system has increased its nervous impulses.
the heart has increased its contractile force increasing cardiac output.

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

Approximately what portion of the foods that we eat have been genetically modified in some way? a.fewer than 10% b.about 50% c.nearly 100%

Amarine ecologist has constructed the conceptual model shown in the diagram. what predictions can be made from using this model? where the tertiary consumers get their energy how often primary producers are able to reproduce when bacteria and fungi initiate the process of decomposition whether other secondary consumers are present