1. Ch 26 A Closer Look at Amniotes 26.1 Amniotes
The amniotic sac contains everything an embryo needs to grow.
some develop inside mother’s body
some develop inside a tough, semipermeable shell
The amniotic egg allowed vertebrates to reproduce on land.

2. Anatomy Differences:
The first animals walked in a sprawl.
Other amniotes, including dinosaurs, evolved a more upright stance.

3. All amniotes have two circuits of blood vessels.
pulmonary circuit moves blood from the heart to the lungs
systemic circuit moves blood from the heart to the rest of the body

4. Amniotes have a three- or four-chambered heart.
reptiles hearts have three chambers
birds and mammals hearts have four chambers
FOUR-CHAMBERED HEART
THREE-CHAMBERED HEART

5. Amniotes manage body heat in different ways.
Ectotherms have body temperatures determined by the surrounding environment.
Endotherms use metabolic heat to keep tissues warm.
Endotherms can live in a wider range of climates than ectotherms.

6. 26.2 Reptiles Reptiles were the first amniotes
Reptiles share several characteristics.
ectotherms
covered with dry scales
reproduce by laying or retaining amniotic eggs
three-chambered heart
cloaca

7. Reptiles have two reproductive strategies.
Oviparous reptiles deposit eggs into an external nest.
Viviparous reptiles retain eggs and give birth to live offspring.

8. Over time, amniotes evolved into three different groups.
synapsids
anapsids
diapsids

10. 4 Modern groups of reptiles:
Turtles, tortoises, and terrapins are the remaining anapsids.
bony shell encases body
200 species
Sphenodonts are closely related to lizards.
diapsids
primitive characteristics
two species

11. Snakes and lizards are very closely related and share a number of features.
diapsids
shed skin at regular intervals
flexible skull
Jacobson’s organ
Crocodilians are more closely related to birds than other diapsids.
semi-aquatic predators
23 species

12. 26.3 Birds
Birds and many theropod dinosaurs share anatomical features.
hollow bones
fused collarbones that form V-shaped wishbone
rearranged muscles in the hips and legs
“hands” that have lost their fourth and fifth fingers
feathers
The oldest undisputed fossilized bird is Archaeopteryx.

13. Birds have several unique features that allow them to fly.
wings to produce flight
strong flight muscles to move the wings
active metabolism that provides energy to the muscles
hollow bone structure to minimize weight
gonads active during only part of year

14. Wings are structures that enable birds to fly.
airfoil shape
covered with feathers
Air sacs help a bird meet its oxygen demand during flight.
The shape of a bird’s wing reflects the way it flies.
wide and broad
stout and tapered

15. Differences in the shape of a bird’s beak reflects how it eats.
Spearlike
Hooked
chisel-shaped
Birds show great diversity in their foot shape.
Webbed
heavy claws
different toe location

16. 26.4 Mammals
Evolutionary adaptations allowed mammals to succeed dinosaurs as a dominant terrestrial
Mammals are:
active
large-brained,
endotherms with complex social, feeding, and reproductive behaviors.

17. All mammals share four anatomical characteristics.
hair to retain heat
mammary glands to produce milk
a middle ear with three bones to hear higher-pitched sounds
chewing jaw to break up food quicker

18. A set of adaptations in the mammalian jaw makes chewing possible.
secondary palate closes off air passages
muscles move jaw side-to-side

19. 3 Main Groups:
Monotremes lay eggs.
duck-billed platypus
echidna
Marsupials give birth to live young that grow to maturity inside a pouch.
opossum
kangaroo
wombat
koala
Eutherians give birth to live young that have completed fetal development.
most familiar mammals
Humans
Eutherians filled many niches after the extinction of the dinosaurs.