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. The biological fitness of an organism is dependent on its ability to survive and reproduce in a given environment. If different traits or alleles increase the fitness of an organism, those alleles will consequently increase in the gene pool, and that trait will increase in the population.
The statement that highlights and describes in detail the key features of an aquatic animal would be produce qualitative data analysis as we will describe its external features such as color size etc.
Passive transport moves molecules from one side of the membrane to the other with the energy of the chemical gradient (or concentration gradient). Otherwise, active transport uses the hydrolyzation of ATP to gain energy in order to move molecules across the membrane without taking into account the gradient.