Amniote embryos develop in a fluid-filled sac. • The amniotic sac contains everything an embryo needs to grow. • some develop inside mother’s body • some develop inside a tough, semipermeable shell
AllantoisHolds waste materialsas the embryo grows Embryo AmnionProtects andsurrounds theembryo Yolk sac Contains the nutrient supply for the growing embryo Chorion Allows gas exchange with outside environment • The amniotic egg allowed vertebrates to reproduce on land.
Anatomy and circulation differ among amniotes. • The first animals walked in a sprawl. • Other amniotes, including dinosaurs, evolved a more upright stance.
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
THREE-CHAMBERED HEART FOUR-CHAMBERED HEART • Amniotes have a three- or four-chambered heart. • reptiles hearts have three chambers • birds and mammals hearts have four chambers
Amniotes can be ectothermic or endothermic. • 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.
Reptiles are a diverse group of amniotes. • Reptiles share several characteristics. • ectotherms • covered with dry scales • reproduce by laying or retaining amniotic eggs • three-chambered heart • cloaca
Reptiles have two reproductive strategies. • Oviparous reptiles deposit eggs into an external nest. • Viviparous reptiles retain eggs and give birth to live offspring.
Reptiles have been evolving for millions of years. • Over time, amniotes evolved into three different groups. • synapsids • anapsids • diapsids
The diversity of ancient reptiles led to the evolution of modern reptiles, birds, and mammals.
There are four 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
brain Jacobson’s organ tongue • 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. • diapsids • semi-aquatic predators • 23 species
Birds evolved from theropod dinosaurs. • Birds and many theropods 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
lung gizzard kidney crop small intestine pectoral muscle large intestine cloaca sternum(keel) liver heart A bird’s body is specialized for flight. • 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
Wings are structures that enable birds to fly. • airfoil shape • covered with feathers
Birds have spread to many ecological niches. • The shape of a bird’s wing reflects the way it flies. • short and broad • long and narrow
lung gizzard kidney crop small intestine pectoral muscle large intestine cloaca sternum(keel) liver heart • The shape of a bird’s wing reflects the way it flies. • stout and tapered • wide and broad
Bald eagle green woodpecker blue-footed booby • Differences in the shape of a bird’s beak reflects how it eats. • spearlike • hooked • chisel-shaped
blue-footed booby bald eagle green woodpecker • Birds show great diversity in their foot shape. • webbed • heavy claws • different toe location
KEY CONCEPT Evolutionary adaptations allowed mammals to succeed dinosaurs as a dominant terrestrial vertebrate.
All mammals share several common characteristics. • Mammals are active, large-brained, endotherms with complex social, feeding, and reproductive behaviors.
All mammals share four anatomical characteristics. • hair to retain heat • mammary glands to produce milk
All mammals share four anatomical characteristics. • a middle ear with three bones to hear higher-pitched sounds • chewing jaw to break up food quicker
A set of adaptations in the mammalian jaw makes chewing possible. • secondary palate closes off air passages • muscles move jaw side-to-side
Modern mammals are divided into three 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.