You observe that mussels growing at Halibut Point State Park have much thicker shells than do mussels growing at the Plymouth pier.You also observe that there are many more predatory snails, which feed on mussels by drilling through their shells, present at Halibut Point than in Plymouth. Why might greater shell-thickness in mussels be an induced rather than a constitutive (always present) trait?

MCQs on how organisms evolve over time, with particular emphasis on natural selection, evolution, speciation, phylogeny and taxonomy, and aspects of genetics and inheritance. As well as the study of population ecology and ecosystems.