What is the function of the veins, and how do these vessels compare with the arteries?
What will be an ideal response?
Veins function to move blood toward the heart, usually carrying blood low in oxygen. Pulmonary veins are an exception to this pattern; they carry oxygen-rich blood. In comparison to arteries, veins have thinner walls with less muscle and a larger lumen. Valves are located within veins; their function is to prevent backflow. Circulation is due mostly to contraction of skeletal muscles, which forces blood upward, and to pressure changes caused by breathing movements.
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Viruses contain DNA or RNA, but lack genes necessary for metabolism and reproduction. Why are viruses not considered to be alive?
A. Viruses are unable to reproduce independently of a host. B. Viruses do not have the ability to evolve in their environment. C. Viruses do not contain internal organelles. D. Viruses do not contain nucleic acids.
Which element is likely to be chemically unreactive?
a. chlorine (7 valence electrons) b. calcium (2 valence electrons) c. argon (8 valence electrons) d. carbon (4 valence electrons) e. potassium (1 valence electron)
Which of the following CANNOT be used to
describe some aspect of polysaccharides?
a. energy storage b. glucose subunits c. straight or branched chain d. insoluble in water e. complex
When the death of species is less imminent, but the population of a particular species is quite small, it is defined asbeing:a
extinct. b. extant. c. endangered. d. threatened. e. endemic.