Grolar Bears (the hybrid form of polar and grizzly bears) are an example of the problematic nature in defining a species. We know that polar bears diverged from brown bears around 400,000 years ago due to fluctuating ice ages. For this question, please explain:
A) The likely population structure of brown bears prior to the polar bear speciation (Possible Concepts: metapopulations, gene flow, genetic drift, geographic range, variation of habitat, morphology, and behavior, polymorphic traits, balancing selection)
B) How the brown bear adapted to new environmental conditions (Possible Concepts: gene flow, geographic barrier, allopatry, pre-zygotic, genes/alleles, polymorphic/monomorphic traits, selection (directional, stabilizing, or disruptive), mutation, behavioral flexibility)
C) Why brown bear and polar bear populations are able to successfully hybridize and the possible outcomes for the offspring (accepting that they are viable and fertile) (Possible Concepts: climate change, post-zygotic barriers, gene flow, environmental inviability, selection (directional, stabilizing, or disruptive), variation, meiosis, homologous chromosomes, mutation, speciation)
D) What does this mean about the biological species concept and Darwin's views of evolution being represented by a branching tree (Possible Concepts: reproductive continuity, reproductive isolation, reticulate evolution, genotype/phenotype, variation)