ISA Certified Arborist Practice Exam

Bark primarily provides protection for a tree's branches and trunk from injury. The outer layer of bark acts as a barrier against physical damage, diseases, and pests. This is essential for the tree's survival as any damage to these vital parts can impede its ability to transport water and nutrients, leading to further decline and potential death. While bark may also play a role in helping a tree grow taller and attracting insects, these are not its primary functions. Trees also utilize other mechanisms, such as flowers, for reproductive purposes, making option C incorrect. Option B is also incorrect as bark does not intentionally attract insects, although they may still be attracted to the warmth and shelter it provides.