The amphibian heart has a single, undivided ventricle, two atria, a sinus venosus, and a Conus arteriosus. Their sarcopterygian ancestors had hearts with all of these chambers, but the ventricle was partially divided and probably aided in separating pulmonary and systemic circulatory circuits. Check the following statements that could help us understand why amphibian evolution resulted in the loss of the partial ventricular septum. A .The loss of the ventricular septum probably occurred because blood returning to the heart of amphibians bypasses the ventricle being shunted from the sinus venasus and right atrium directly to the pulmonary artery and lungs.
B. Loss of the partial ventricular septum reflects the fact that blood returning to the heart from the systemic circuit is often highly oxygenated because many amphibians rely on cutaneous and buccal gas exchange, as well as pulmonary gas exchange, much of the time.
C. Mixing of blood from the lungs with blood from the body in the ventricle is not a problem. Loss of the partial ventricular septum is not a problem because the spiral valve keeps systemic and pulmonary blood separate within the ventricle.
D. The Conus arteriosus of the amphibian heart receives blood from the right atrium and passes the blood on to the pulmonary circulation. This keeps oxygenated and nonoxygenated blood separate.
E. The slightly asynchronous contraction of left and right atria help keep systemic and pulmonary circuit blood separated in the ventricle.

Cell division is important to single celled organisms because it allows the cells to reproduce. through cell division, cells make exact copies of themselves. when single celled organisms go through cell division, they make exact copies of themselves which is how they reproduce.

Mantle convection  is the slow  creepingmotion of earth's solid silicate  mantle  caused by  convection  currents carrying  heat from the interior  to the planet's surface.[1][2]  the earth's surface  lithosphere, which rides atop the  asthenosphere  (the two components of the  upper mantle), is divided into a number of  plates  that are continuously being created and consumed at their opposite  plate boundaries. accretion occurs as mantle is added to the growing edges of a plate, associated with  seafloor spreading. this hot added material cools down by  conduction  and  convection  of heat. at the consumption edges of the plate, the material has thermally contracted to become dense, and it sinks under its own weight in the process of  subduction  usually at an  ocean trench.[3]this subducted material sinks through the earth's interior. some subducted material appears to reach the lower mantle,[4]  while in other regions, this material is impeded from sinking further, possibly due to a phase transition from  spinel  to  silicate perovskiteand  magnesiowustite, an  endothermic reaction.[5]the subducted oceanic crust triggers  volcanism, although the basic mechanisms are varied. volcanism may occur due to processes that add buoyancy to partially melted mantle causing an upward flow due to a decrease in density of the partial melt.secondary forms of convection that may result in surface volcanism are postulated to occur as a consequence of intraplate extension[6]  and  mantle plumes.[7]it is because the mantle can convect that the  tectonic plates  are able to move around the earth's surface.[8]mantle convection seems to have been much more active during the  hadean  period, resulting in gravitational sorting of heavier molten  iron, and  nickel  elements and  sulphides  in the core, and lighter  silicate minerals  in the  mantle.

The last option water because it is slow