Well quiet naturally both animal and human testing are both very controversial and involve great deal of ethics.
Answer:
The physical conditions are necessary for nuclear fusion and formation of stars are given below.
Explanation:
Nuclear fusion emitted high amount of heat energy which increases the temperature of the surrounding environment while formation of stars absorb heat energy and finally lower the temperature. The force of gravitational attraction is lower in nuclear fusion while the force of gravitational attraction becomes higher in formation of stars. Nuclear fusion does not promote stellar formation while formation of stars promotes stellar formation.
The two haploid hyphae containing nuclei that do not fuse produces 2 cytoplasms. This happens during the sexual reproduction of fungi. However, in general, sexual reproduction of fungi involves uniting two sex cells wherein the nuclei of these sex cells fuses.
If the cornea were to work alone, the image formed would be blurred as the point of image formation would be behind the retina. Therefore, with the help of the lens in the eye, the focal length is reduced to 1.7 cm so that the image forms on the retina.