Chapter 33 - Introduction to Vertebrates

Characteristics of Vertebrates

  • Vertebrae (individual segments of the backbone)
  • Segmentation
  • Bilateral Symmetry
  • Dorsal Nerve Cord (spinal cord)
  • Two pairs of jointed appendages
  • Organ Systems (see elephant anatomy)
  • Ectothermic ("cold-blooded") or Endothermic ("warm-blooded")

Timeline of Vertebrate Evolution

About When Age Animals
550 million years ago Ordovician Period

First vertebrates
jawless fishes
400 million years ago

Devonian Period

"Age of Fishes"

 Acanthodians
jawed fishes
350 million years ago

Carboniferous Period (and Permian)

"Age of Amphibians"

 Amphibians
240 million years ago

Triassic Period
Jurassic Period

"Age of Dinosaurs"

reptiles appeared

dinosaurs dominated the land for 150 million years - sauropods, theropods, etc..
60 million years ago

Tertiary Period

"Age of Mammals"

Dinosaurs extinct

Mammals appeard
340,000 years ago Quaternary period Humans appeard

Evolutionary Trends

Acanthodians - first jawed fishes, jaws thought to have evolved from gill arches

Lobe- finned fish (coelocanth) - thought to be the link between fish and amphibians, fins had leg-like characteristics

Note the bones located in this lobe finned fish, there are similarities to bones found in land vertebrates

See http://www.dinofish.com/

Archaeopteryx - the link between dinosaurs and birds. Archeopteryx had several featurs in common with bird and dinosaurs

Like a Bird

Feathers
Furculum (wishbone)

Like a Reptile

Solid bones
Claws on wings
Long tail
Teeth

Therapsid - the link between reptiles and mammals - the legs of the therapsid resemble the legs of mammals, they were pushed under the body rather than to the sides of the body

 

Vertebrate Classification

Kingdom Animalia
-----Phylum Chordata
----------Subphylum Vertebrata

Class Examples
Agnatha Jawless fishes; lamprey & hagfish
Chondrichthyes Cartilage fish, sharks and rays
Osteichthyes Bony fish; salmon, catfish, goldfish
Amphibia Amphibians; frog, salamander
Aves Birds
Reptilia Reptiles; snakes, lizards, dinosaurs, turtles
Mammalia

Mammals; dogs, cows, humans, kangaroos

Marsupials - pouched mammals
Placentals - mammals that develop young in uterus
Monotremes - mammals that lay eggs

 

Chordates and Vertebrates

The phylum chordata contains all the vertebrates plus curious creatures that have a notochord, but not a backbone. These include the lancelet and the sea squirt.

Vertebrates make up the largest group of chordates, those that have both the notochord and the backbone.

Sea Squirts

Lancelet