All elements are made of "atoms", and an atom is made up from 3 basic particles: Electrons are particles with a negative charge :)
The answer is cancer.
Cancer is an uncontrolled division of cells. The regulation of cell cycle is necessary for normal cell division. The first phase of the cell cycle is the G1 phase. If the G1 phase is affected, mistakes in this process lead to the uncontrolled division of cells called cancer.
The answer is no, high biological fitness in one environment doesn’t have to be high in another environment.
Biological fitness is a term used in evolutionary biology and it is the quantitative representation of how a genotype (or phenotype) is successful (reproductively) in a certain environment. Fitness depends on environment so it changes if the environment changes. The fitness of a genotype is manifested through its phenotype, which is affected by the environment.