1. Order Cetacea

3. Cetacea
Fossil evidence suggests that cetaceans share a common ancestor with land-dwelling mammals that began living in marine environments around 50 million years ago.

4. Characteristics The forelimbs are modified into flippers
The tiny hindlimbs are vestigial
they do not attach to the backbone and are hidden within the body
The tail has horizontal flukes
Nearly hairless
Insulated from the cooler water they inhabit by a thick layer of blubber

5. Cetacea
Cetaceans breathe air. They surface periodically to exhale carbon dioxide and inhale a fresh supply of oxygen
Myoglobin, by nature, has a higher oxygen affinity than hemoglobin. The higher the myoglobin concentration in skeletal muscle, the longer the animal can stay underwater.
white rabbits have 0.08 grams
northern bottlenose whale has 6.34 grams

6. Cetacea
Increased body size also increases maximum dive duration. Greater body size implies increased muscle mass and increased oxygen stores.
Cetaceans also obey Kleiber's law, which states that mass and metabolic rate are inversely related, i.e., larger animals consume less oxygen than smaller animals per unit mass.

7. Sub Orders Suborder Odontoceti: Suborder Mysticeti:
sperm whale, beluga, dolphins and porpoises, have teeth they use for catching fish, squid or other marine life
they do not chew, but swallow prey whole
Suborder Mysticeti:
blue, humpback, bowhead and minke whales have baleen plates
these plates filter small animals (such as krill and fish) from the seawater

8. Odontoceti

9. Mysticeti