1. The Vertebrate Genealogy
Chapter 30

2. What is a chordate?
There are 4 anatomical structures that appear during some point during the animal’s lifetime:
1. Notochord – long flexible tube between the
gut and the nerve cord
- becomes gelatinous material
between vertebrae in humans
2. Dorsal, hollow nerve cord – becomes CNS
3. Pharyngeal slits
4. Muscular postanal tail – most chordates
have a tail that extends beyond the anus

3. What is a chordate?

5. Survey of Vertebrate Classes
Fishes: Agnatha, Chondrichthyes, Osteichthyes
Tetrapods: Amphibia, Reptilia, Aves, Mammalia
Amniotes: Reptilia, Aves, Mammalia
Have a shelled water-retaining egg

6. Class Agnatha Sample organisms: Jawless vertebrates
Hagfishes, lampreys
Jawless vertebrates
Feed by sucking blood after clamping onto prey or by scavenging
Do not have paired appendages

7. Class Chondrichthyes Sample organisms: sharks and rays
Cartilaginous fishes – have relatively flexible skeletons made of cartilage rather than bone
Most sharks are carnivorous and have acute senses

8. Class Osteichthyes Bony fishes Sample organisms: perch, trout
Have hard skeletons (due to ossification)
Sample organisms: perch, trout
Breathe by drawing water over 4-5 pairs of gills covered by operculum (protective flap)
Most bony fishes are oviparous
Females lays large numbers of eggs, fertilization occurs externally

9. Class Osteichthyes

10. Class Amphibia The first vertebrates (tetrapods) on land
Amphibians must deposit their shell-less eggs in water
Sample organisms: frogs & salamanders
Amphibian = “two lives”
Tadpole – larval stage
Metamorphosis occurs
Frog – legs develop
Salamanders – have tails
Frogs – do not have tails

11. The Amniotic Egg
The amniotic egg is a reproductive adaptation that allowed terrestrial vertebrates to complete their life cycles on land
The shell prevents the egg from drying out
4 layers of protection:
Amnion – prevents dehydration, cushions shocks
Yolk Sac – stockpile of nutrients
Allantois – disposal sac for certain metabolic wastes
Chorion – gas exchange

12. Class Reptilia Sample organisms: lizards, snakes, turtles, crocodiles
Reptiles have scales made of keratin that cover their skin
Obtain oxygen with their lungs
Fertilization occurs internally
Most reptiles lay amniotic eggs on land
Ectotherms – body temperature fluctuates with the environment

13. Class Aves Birds are tetrapods with feathers
Their forelimbs are modified as wings
Sample organisms: owl, sparrow, penguin, eagles
Lay amniotic eggs
Endothermic – regulate their own body temps.
Anatomy adapted for flight
Form & function

14. Class Mammalia Mammals have hair Endothermic
Mammary glands that produce milk
Most mammals are born, not hatched
Three major groups:
Monotremes – lay eggs
platypuses, echidnas
Marsupials – complete development in a maternal pouch
Kangaroos, koalas, opossums
Placental mammals – complete development within the uterus, joined to the mother by the placenta
Sheep, bats, elephants, humans

15. Paleoanthropology
Paleoanthropology is the study of human origins and evolution
Correcting misconceptions:
“Let’s first dispose of the myth that our ancestors were chimpanzees or any other modern apes. Chimpanzees and humans represent two divergent branches of the anthropoid tree that evolved from a common, less-specialized ancestor.”

16. Paleoanthropology 1974 – Ethiopia Homo habilis Homo erectus
“Lucy” is an Australopithecus skeleton
3.18 million years old
Homo habilis
2.5 million years ago
Enlargement of the human brain
Homo erectus
First hominid to migrate out of Africa into Asia and Europe
Taller than H. habilis and a larger brain capacity

17. Paleoanthropology
2 models of how Homo sapiens evolved

18. To think about…
“Of the many crises in the history of life, the impact of one species, Homo sapiens, is the latest and potentially the most devastating.”
- Neil Campbell, 4th ed.