Valves in veins are formed of the tunica media. cause venous blood flow to go in only one direction. are found only in the largest veins. make the use of a skeletal muscle pump unnecessary for venous blood flow. are the leading cause of high blood pressure.

How does photosynthesis show the conservation of mass and energy?

The double bond between a carbon atom and two oxygen atoms (a molecule of carbon dioxide) has two characteristics. what are they? a.an ionic bond is formed between the oxygen and carbon atoms. b.four valence electrons are shared. c.two valence electrons are shared. d.valence electrons are shared between oxygen atoms.

28. how many linkage groups will be formed by homogametic organism with 28 chromosomes?