Many north american animal species migrated to the south during pleistocene ice ages and returned to the north during interglacial periods. these observations are consistent with
a. expanded physiological tolerance.
b. distribution shift and habitat tracking.
c. migration barriers.
d. range expansion by adaptation.
e. declining habitat size.

The correct answer is option b. "distribution shift and habitat tracking".

Explanation:

Distribution shift is a common adaptation, at which species migrate to a different location looking for better living conditions. Habitat tracking is a very similar concept, but it refers to species either adapting or migrating in response to an environment detrimental. These two phenomenons explain why many North American animal species migrated to the south during Pleistocene ice ages and returned to the north during interglacial period. Pleistocene ice ages were a very challenging time for the species for being a period of repeated glaciations, therefore species had to adapted by distribution shift and habitat tracking.

osteogenesis imperfecta (oi) refers to a congenital ailment of bones. in the condition, the bones become brittle or fragile. this ailment is a general result of the defect or mutations in the genes (colia1 or colia2). this mutation results in imperfect collagen formation either in quantity or quality wise.  

there are eight kinds of oi defects, and each kind varies with certain distinctions in symptoms. the usual symptoms include frequent bone fractures, loss of hearing in infants, protruding eyes, discoloration of the white in the eyes, respiratory issues, loosening of the joints, short stature, and other symptoms.