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.
A common feature of a vertebrate blastula is that it consists of a layer of blastomeres, known as the blastoderm, which surrounds the blastocoele. In mammals the blastula is referred to as a blastocyst.The blastocyst contains an embryoblast (or inner cell mass) that will eventually give rise to the definitive structures of the fetus, and the trophoblast, which goes on to form the extra-embryonic tissues. blastula is a sphere of cells surrounding a blastocoele. The blastocoele is a fluid filled cavity which contains amino acids, proteins, growth factors, sugars, ions and other components which are necessary for cellular differentiation. The blastocoele also allows blastomeres to move during the process of gastrulation.