The phenotype describes the set of observable characteristics of an species. It depends on the expression of genes (genotype) and the environment. For example, humans having type 2 diabetes can be linked to both genetic predispositions and poor eating habits.
Epigenetic modifications can also modify a phenotype. Epigenetics is a process that explains how environmental factors (diet, smoking, stress ...) influence the expression of genes and therefore the phenotype.
Because those are traces of life meaning that there was life living there once, that life wouldn't have been able to survive there with how Antarctica is now.