b. Skeleton of cartilage

c. Movable jaws with well-developed teeth

d. Placoid scales and paired fins

c. Viviparous

c. Lay shelled amniotic eggs.

d. Use behavior to regulate body temperature.- Ectothermic

b. Squamata (lizards and snakes)

c. Crocodilia (alligators and crocodiles).

lFour chambered heart is efficient in blood circulation.

lOne way air flow in respiratory track.

lLarge Keel to anchor pectoral muscles.
lLack teeth and use a gizzard to grind food.

lSome lack organs (having one ovary)

lHollow bones decrease weight.

lFeathers made of keratin. 

b. Ovoviviparous: retention of the eggs within the uterus but only the eggs nourishes the embryo.

c. Viviparous: placental formation in the uterus.
d. Cycloid scales have a smooth outer edge
e. Ctenoid scales have a toothed outer edge

•Sea otters inhabit nearshore environments and dive to the sea floor to forage on mollusks, crustaceans and echinoderms (sea stars and urchins)

–Must eat ~25-30% of their body weight per day

•They feed primarily on seals, which they stalk at breathing holes

•World’s largest land carnivore

•Thick blubber; translucent fur, black skin!

•Threatened by the loss of Arctic sea ice!

–Rear flippers cannot be moved forward

–No external ear flap

–Claws (and fur) on flippers

–Short, robust neck

–Rotatable hind flippers

–External ear flap

–Long, flexible neck

–No fur or claws on flippers

–Both male and female have tusks; can reach 1 meter in length!

–Used for defense, and anchoring onto ice

•Strictly Arctic!

•Benthic-feeder; feeds                                        primarily on clams

•They are predators, feeding mainly on fish and squid

•Streamlined bodies for swimming

•Thick layer of fat, or blubber for insulation, food reserves, and buoyancy  

Sea otter and the polar bear (order Carnivora):
•Sea otters and polar bears are marine mammals belonging to order Carnivora

•The sea otter is the smallest marine mammal, which lacks a layer of blubber

•Instead, the sea otter has extremely dense fur, which traps air against the body for insulation

–Hunted extensively for fur nearly to extinction

Manatees and dugongs (order Sirenia):
•Sirenians (order Sirenia) include the manatees and dugong

•Sirenians, also known as sea cows, have a pair of front flippers, but no rear limbs

•Swim with up-and-down strokes of their paddle- (manatee) or V- (dugong) shaped tails

•Closest land relative is the elephant!
•The Stellar Sea Cow was a large, herbivorous marine mammal formerly abundant in the North Pacific

•Described by naturalist Wilheim Stellar in 1741; hunted to extinction within 27 years of discovery!

–8 meters long

–Fed on kelp

–Did otter hunting                                                            play a role?

Whales, dolphins, and porpoises (order Cetacea): widely distributed and diverse clade of aquatic mammals that today consists of the whales, dolphins, and porpoises. Cetaceans are carnivorous and finned. Most species live in the sea, some in rivers.
120 species altogether

–Four-chambered heart

–Fur or hair (not feathers) to retain heat

–Mammary glands to produce milk for young
- Endothermy

- Live births

- Placenta: tissue developed to give nutrients to the embryo.

- Generally have larger craniums so more and complex behaviors.

Columbaves — turacos, bustards, cuckoos, pigeons, sandgrouse, and mesites.

Gruiformes — cranes, rails, crakes, Sungrebe, flufftails, and others.

Aequorlitornithes — shorebirds, flamingos, grebes, gulls, tropicbirds, penguins, and other waterbirds.

Inopinaves — all landbirds, including hawks, owls, toucans, falcons, parrots, and songbirds.

- Four chambered heart is efficient in blood circulation.

- One way air flow in respiratory track.

- Large Keel to anchor pectoral muscles.
- Evolution to flight dominates Avian characteristics.

- Lack teeth and use a gizzard to grind food.

- Some lack organs (having one ovary)

- Hollow bones decrease weight.

- Feathers made of keratin.

b. Squamata (lizards and snakes): distinguished by their skins, which bear horny scales or shields

c. Crocodilia (alligators and crocodiles): have four sprawling legs that can be used to gallop; they replace their teeth throughout life; they have strong jaws and a powerful bite