1. Vertebrate Anatomy – Unit 1
What is a Vertebrate?
Vertebrate Anatomy – Unit 1

2. FIRST: A Vertebrate is an ANIMAL
What is an Animal?
KINGDOM Level of Taxonomy
Includes all organisms that possess the following characteristics:
Multicellular
Heterotrophic
No cell walls around cells
Several other characteristics

3. SECOND: A Vertebrate is a CHORDATE
What is a Chordate?
PHYLUM level of Taxonomy
Includes all ANIMALS that possess the following characteristics:
Dorsal Hollow Nerve Cord
Pharyngeal Gill Slits
Notochord
Post-anal Tail
A few chordates possess ALL these characteristics at all life stages, but most only possess all of these during EMBRYONIC stages.

4. THIRD: A Vertebrate is a VERTEBRATE
What is a VERTEBRATE?
SUBPHYLUM level of Taxonomy
A level not normally addressed in intro bio classes
Includes all CHORDATES that possess the following characteristics:
A BACKBONE that protects the nerve cord and supports the body; replaces the notochord
This also generally implies the presence of a cranium (skull) to protect the brain.
Some animals have ONLY the cranium, thus they are not quite true vertebrates

5. TRUE or FALSE? All CHORDATES are VERTEBRATES.
All VERTEBRATES are CHORDATES.

6. The term Chordata comes from
The Notochord

7. About the Notochord In a Vertebrate Chordate,
the Notochord is present only during the EMBRYONIC stages of life.
The notochord is replaced by the backbone

8. About the Nerve Cord Dorsal Hollow
Anterior end enlarged to create the BRAIN

9. Pharyngeal Gill Slits Pharynx = throat Present in embryos
These slits in the throat area become the gills in fish and other vertebrates that breath water
In mammals and other land vertebrates they become structures of the lower jaw, face and throat.

11. Other Chordate Characteristics
Closed circulatory system
Blood always contained in blood vessels
Muscle blocks or segments called somites in embryos

12. Who are the Chordates closest relatives?
The closest INVERTEBRATE relative of the chordates are the members of Phylum Echinodermata
The Sea Stars
The Sea Urchins
The Sea Cucumbers
How can this be?
The embryonic development of echinoderms has a very important similarity to the embryonic development of chordates, even though the adult forms look very different.

13. Echinoderms and Chordates
The embryonic opening called a blastopore becomes an ANUS in both echinoderms and chordates.
In all other INVERTEBRATES it becomes the MOUTH.

14. Phylum Chordata – 4 subphyla
Subphylum Urochordata
Subphylum Cephalochordata
Subphylum Myxini
Subphylum Vertebrata

15. Subphylum Urochordata
The Tunicates
Also called Sea Squirts
The 4 Chordate characteristics are present in the larval form
The adult looks very different
Larva are free swimming with tails, etc.
Adult is sessile.

17. Phylum Cephalorchordata
A group called the lancelets
Most common member of this group is amphioxus
Swimmers
Possess all chordate characteristics in adult form

19. Phylum Myxini New Phylum
Once thought to be vertebrates, but they do not possess a true backbone – only a true cranium
Hagfish is the only member
Hagfish sliming video
More slime
More

20. Subphylum Vertebrata
WE are vertebrates; hence humans have studied phylum vertebrata a lot.

21. When did the 1st vertebrates arise on Earth?
Around 500 million years ago

22. What were the first vertebrates like?
The first vertebrates were DIFFERENT from vertebrates we know today.
They lacked JAWS.
Think lampreys which are the only vertebrates that remain today who lack jaws.
Jawed vertebrates did not appear until around 400 million year ago
lamprey video
One more

23. Where did vertebrates first evolve?
Ocean

24. Defining characteristic of a vertebrate?
Backbone
Though others are discussed.

25. Vertebrates and sex
All vertebrates have separate sexes – male and female

26. Some terms with regard to reproduction
Oviparous
Egg layer
Young are nourished from yolk inside an egg that is laid outside the mother’s body

27. Some terms with regard to reproduction
Ovoviparous
Young develop internally, but are nourished with YOLK as though they were inside an egg.
“Live birth”

28. Some terms with regard to reproduction
Viviparous
Young develop internally
Nourished directly from the mother’s bloodstream
NO yolk
Placenta and umbilical cord involved
icky picture warning…