Predict the effect if injuries to the brainstem, cerebral cortex, cerebellum

If there were injuries to the brain stem, cerebral cortex, and/or the cerebellum then one possible injury could be a seizure or lead to a concussion. another affect could be memory loss, or worse case scenario being paralyzed

  It is oxygen. A plant takes in carbon dioxide and releases oxygen.

Based on the information provided within the question it can be said that this scenario is describing the term known as directional selection. This term refers to a type of natural selection in which a certain characteristic of the species moves to one extreme as opposed to another. Which in this case refers to the bears size.