An open circulatory system __________.

Here is a blood sample that has been spun in a centrifuge. List, as completely as you can, the components you would find in the straw-colored fluid at the top of this tube and in the dense red portion at the bottom.

Physiologists speculate about cardiovascular adaptations in dinosaurs—some of which had necks almost 10 m (33 feet) long. Such animals would have required a systolic pressure of nearly 760 mm Hg to pump blood to the brain when the head was fully raised. Some analyses suggest that dinosaurs' hearts were not powerful enough to generate such pressures, leading to the speculation that long-necked dinosaurs fed close to the ground rather than raising their heads to feed on high foliage. Scientists also debate whether dinosaurs had a 'reptile-like' or 'bird-like' heart. Most modern reptiles have a three-chambered heart with just one ventricle. Birds, which evolved from a lineage of dinosaurs, have a four-chambered heart. Some scientists believe that the circulatory needs of these long-necked dinosaurs provide evidence that dinosaurs must have had a four-chambered heart. Why might they conclude this?

Which type of epithelial tissue would you suppose covers the gills of axolotls?

Which of the following is a function of the circulatory system?

Why do larger animals, such as a bullfrog, require a circulatory system, while animals such as a planarian do not?

In which animal does the circulatory system include a heart and a system of closed vessels?

The function of the pulmonary circuit in a dog is to __________.

In a fish, blood circulates through __________, whereas in a mammal, it circulates through __________.