The condenser lens, is placed between the light source and the specimen and it gathers and focuses the light rays in the plane of the microscopic field to view the specimen.
The blastocyst implants itself to the uterine wall during 2 week after conception
The heart, blood and blood vessels work together to service the cells of the body. Using the network of arteries, veins and capillaries, blood carries carbon dioxide to the lungs and picks up oxygen. From the small intestine, the blood gathers food nutrients and delivers them to every cell.
Answer:
All viruses are obligate parasites; that is, they lack metabolic machinery of their own to generate energy or to synthesize proteins, so they depend on host cells to carry out these vital functions.
