State briefly the general principles of classification of living organisms

Recent advances in biochemical and electron microscopic techniques, as well as in testing that investigates the genetic relatedness among species, have redefined previously established taxonomic relationships and have fortified support for a five-kingdom classification of living organisms. This alternative scheme is presented below and is used in the major biological articles. In it, the prokaryotic Monera continue to comprise the bacteria, although techniques in genetic homology have defined a new group of bacteria, the Archaebacteria, that some biologists believe may be as different from bacteria as bacteria are from other eukaryotic organisms. The eukaryotic kingdoms now include the Plantae, Animalia, Protista, and Fungi, or Mycota.

blood enters the heart through two large veins, the inferior and superior vena cava, emptying oxygen-poor blood from the body into the right atrium of the heart. as the ventricle contracts, blood leaves the heart through the pulmonic valve, into the pulmonary artery and to the lungs where it is oxygenated.