Hard proposes that the major problem with molecular approaches is that conservation units may be identified without seriously addressing whether these units represent adaptive variation, and he suggests an emphasis on quantitative genetics
. Part Five addresses ecosystems and habitats, and how the ESU concept may overlook biotic integrity as an important component of conservation biology.
The authors begin with material suitable for students, including the molecular basis of inheritance in terms of genome organization, gene structure and regulation, transmission genetics, genetic markers, population genetics and quantitative genetics
, genetic variation in natural populations, including variation within populations, geographic variation, evolutionary genetics and gene conservation, and tree improvement, including the structure and concepts of tree improvement programs, base populations, phenotypic mass selection, genetic testing, data analysis methods, deployment, and advanced-generation breeding stages.