Evolution — practice question

Twenty million years ago, the area that is now Panama lay beneath an ocean. A gap existed between North America and South America, and the Atlantic and Pacific Oceans flowed through it without obstruction. The porkfish, Anisotremus sp., lived in this zone between North America and South America. Fig. 8.1 shows a porkfish. Around 3 million years ago, volcanic activity and sedimentation created a narrow land strip, Panama, that linked North America and South America. Fig. 8.2 shows the region 20 million years ago and at the present day.