The evolution of Cetaceans
One of the most significant events in the evolution of vertebrate animals is the transition to living on land. During the Late Devonian period, approximately 370 million years ago, a lineage of lobe-fin fishes evolved the ability to move about on land. This led to the evolution of tetrapods (the group that terrestrial vertebrate animals – including ourselves – belongs to) such as Amphibia, Reptilia, Mammalia, and Aves. However, throughout the earth’s history, many groups of tetrapods such as Cetaceans (both living and extinct) have independently evolved to return to living in an aquatic environment.
ESSAY STRUCTURE
1) The diversity of form and ecology of Cetaceans (What kind of environments do/did they live in? What do/did they eat? How big are/were they?)
2) The anatomical adaptations that allow them to live in an aquatic environment.
3a) How many millions of years ago did their terrestrial ancestor live and describe what kind of animal it was.
or
3b) What are the earliest known species of that group? When did they live and describe what kind of animal it was
4) Described notable anatomical changes that are associated with the transition from the terrestrial ancestors/earliest known species to species which are more and more adapted to a fully aquatic life-style. Use transitional form species to illustrate these changes whenever possible.
