A heat engine gives greater efficiency when run with a large temperature difference. In the oceans the temperature difference between surface and deep water is greatest in the tropics, although still a modest 20 to 25 Â°C.
A blastocyst is a cellular mass that forms early in the process of embryo development in mammals. In humans, this stage of embryogenesis occurs five days after fertilization, when there are fewer than 100 cells in the mass.
The blastocyst is made up of cells from the inner cell mass and the blastocoel. There are two types of blastomere cells: 1  The inner cell mass, also known as the embryoblast, gives rise to the primitive endoderm and the epiblast.