1. What features the vertebrates?
Four features define chordates
A notochord
A dorsal hollow nerve cord
A pharynx with gill slits
A tail extending past the anus
All features form in embryos
May or may not persist in adults

2. Invertebrate chordates
Ancestors
Tunicates and lancelets (marine filter-feeders)
Adult and larva

3. Craniates Another ancestor
Chordates with a braincase of cartilage or bone
Hagfish (jawless fish): Simplest modern craniate

4. Vertebrate evolution
Key innovations laid the foundation for adaptive radiations of vertebrates
Vertebral column of cartilaginous or bony segments
Jaws evolved in predatory fishes
Gills evolved in water, then lungs for dry land
Paired fins were a starting point for other limbs

5. Jawed fishes Jawed fishes Cartilaginous fishes (sharks and rays)
Bony fishes
Gills present
Not free
Body plans adapted to life in water
Streamlined shape reduces drag
Swim bladder (in bony fishes) adjusts buoyancy

6. Bony fishes The most diverse vertebrates Lungfishes
Lobe-finned fishes (coelacanth)
Ray-finned fishes

7. Amphibians Frogs, toads, and salamanders Carnivorous vertebrates
First to evolve from aquatic Devonian tetrapods
Adapted to life on land (lungs, 3-chambered heart)
Nearly all return to the water to reproduce

8. Vanishing amphibians
Many amphibians now face extinction due to pollution and habitat loss

9. Amniotes
First vertebrates able to complete their life cycle on dry land
Water-conserving skin and kidneys
Amniote eggs (four membranes)
Active life-styles

10. Some amniote groups Sauropsids
Reptiles (including extinct dinosaurs) and birds
Anapsids
Turtles
Synapsids
Modern mammals and mammal-like species

11. Modern reptiles Major Groups Turtles (shell attached to skeleton)
Lizards (the most diverse reptiles)
Snakes (limbless)
Tuataras (some amphibian-like traits; third eye)
Crocodilians (closest relatives of birds)

12. Reptile characteristics
General characteristics
Live on land or in water
Cold-blooded
Have a cloaca (opening for wastes and reproduction)
Eggs are fertilized in the body, usually laid on land

13. Birds Birds are the only modern animals with feathers
Birds are warm-blooded amniotes

14. Adaptations for flight and migration
Feathers, lightweight bones, and highly efficient respiratory and circulatory systems

15. Mammals
Animals with hair, females that nourish young with milk from mammary glands, a single lower jawbone and four kinds of teeth

16. Modern mammals Three major lineages Egg-laying mammals (monotremes)
Pouched mammals (marsupials)
Placental mammals (eutherians), the most diverse and widespread mammals

17. Primate evolution Key trends Better daytime vision
Upright walking (bipedalism)
More refined hand movements
Smaller teeth
Bigger brains
Social complexity (extended parental care; culture evolved in some lineages)