1. Whales, Dolphins and Porpoises
Whales, dolphins and porpoises are cetaceans (Class Mammalia, Order Cetacea)
Of all the marine mammals, cetaceans (and sirenians) have made the most complete transition to aquatic life
Spend their entire lives in the water
The bodies of cetaceans are streamlined and look remarkably fish-like; an example of convergent evolution

2. Convergent Evolution: Streamlining
Convergent evolution is the process by which unrelated species evolve similar physical characteristics because they have similar lifestyles

3. Whales, Dolphins, and Porpoises
Cetaceans have a pair of front flippers, but the rear pair of limbs has virtually disappeared
Remain in adults as small, useless bones
Most cetaceans have a dorsal fin, like fishes
Their muscular tail ends in a pair of fin-like, horizontal flukes

4. Whales, Dolphins, and Porpoises
Blubber provides cetaceans with insulation
Cetacean nostrils are on top of the head, forming a single, or double opening called the blowhole

5. Whales, Dolphins and Porpoises
There are ~90 species of cetaceans
All are marine, except for 5 species of freshwater dolphins
Cetaceans are divided into two groups:
Toothed whales – includes dolphins & porpoises
Baleen whales; toothless, filter-feeding whales
Photos property of the Riverhead Foundation

8. Cetaceans: Toothed Whales
The majority of cetaceans are toothed whales
Toothed whales use their teeth only to catch and hold prey, not to chew it
Toothed whales have a single blowhole (one opening) on the top of their head
Though they are all whales, most of the small toothed whales are called dolphins or porpoises
Photo property of the Riverhead Foundation

9. Is it a dolphin or a porpoise?
The six species of porpoises are blunt-nosed whales, having flattened teeth
The many more species of dolphins possess a distinctive snout or ‘beak’ and have conical teeth
Porpoise
(Family Phocenidae)
Dolphin
(Family Delphinidae)

10. The Toothed Whale Whales
The toothed “whales” include the sperm whale, beluga, pilot whales, beaked whales, and orca, each divided into their own families

11. A bottlenose whale? Yes!

12. Echolocation All species of toothed whales are capable of echolocation
Marine mammals echolocate by emitting sound waves, and listen for the echoes reflected back from surrounding objects
The brain then analyzes the echoes
The time it takes the echoes to return tells the animal how far away the object is
A type of biological sonar!

13. Echolocation

14. Baleen Whales Toothless whales are best known as baleen whales
Instead of teeth, they have rows of flexible plates, or baleen, which hang down from the upper jaws
Baleen is made of keratin
The inner edge of each plate consists of hair-like bristles that overlap and form a dense mat

15. Baleen whales

16. Baleen Whales

17. Baleen Whales
Baleen whales are characterized not only by their baleen, but by the double opening of their blowholes (double blowhole)
Baleen whales can be further divided into the rorquals; rorquals feed by gulping up schools of fish and swarms of krill
The lower portion of the throat expands during feeding, along distinctive grooves
Photo property of the Riverhead Foundation