phylum chordata
riploblastic: have three germ layers
* Coelomate: have a true body cavity
* Deuterostomes: mouth forms from second opening
* DEFINING CHARACTERISTIC OF CHORDATES
NOTOCHORD present during some stage of development
clades belonging to phylum chordata
clad urochadata - (the tunicates)
clade mixini -(hagfish)
clade cephalochordata - (the lancelets)
clade vertebrata -(the vertebrates)
The notochord has been modified into a vertebral
column (backbone.)
chordate characteristics
not all chordates are vertebrates
- All chordates display these structures at some point
in their life cycle:
- notochord
- dorsal hollow nerve chord
- muscular post anal tail
-pharyngeal slits or clefts
- endosytle or thyroid gland
distinguishing characteristics of clade vertebrata
-vertebral column
-cranium ( skull)
- well developed brain and nervous system
- endoskeleton ( internal skeleton)
- closed circulatory system
Clade Chondrichthyes
Cartilagenous skeleton
* Jaws
* Paired appendages
* Gills
* Internal fertilization
Clade Osteichthyes: Bony fish
Calcified skeleton
* Jaws
* Paired appendages
* External fertilization
* Gill respiration
Actinista
Coelocanth: a lobe-finned fish
Have muscular pelvic and
pectoral fins
Dipnoi (lungfishes)
Have lungs and gills
tetra pods characteristics
Have jaws
Have four limbs
clade amphibia
Frogs, toads, newts & salamanders
* Aquatic larval stage vs. terrestrial adult stage
* Tetrapods (4 limbs)
* Appendages for land movement
* Respire via lungs and/or gills
* Tied to water for reproduction
clade reptila
Lizards, snakes, turtles, crocodiles, and
birds
* Lizards, snakes, turtles, etc.
are ectothermic
* Birds are endothermic
* Skin has scales
* Respire via lungs
* Amniotes with shelled eggs
* Primarily adapted to live on land
birds
Feathers
* Tetrapods
* Wings (modified forelimbs)
* Amniotes with shelled eggs
* Endothermic (constant body
temperature)
Clade Mammalia
Monotremes (egg-layers)
* Marsupials (develop in a pouch)
* Placentals or Eutherians (develop in
a uterus)
* Tetrapods
* Hair
* Mammary glands
* Respire via lungs
* Endothermic
morphological data
Comparative Anatomy
* Extinct or Extant Taxa
* Limited in amount of data
* Subjective
molecular data
DNA
* Extant Taxa Only
* Not Subjective
* Data could be due to mutations (false similarities /
differences)
* Large Data Sets
character matrix
a table used in phylogenetics to organize traits of different organisms (taxa) to build a phylogenetic tree
common ancestor
an ancient species from which multiple present-day species have evolved through divergence.
outgroup
A taxon with an evolutionary lineage that has diverged from the rest
of the taxa in the cladogram or phylogenetic tree.
clade
A group of organisms that have evolved from a common ancestor.
branches
The horizontal branches represent an evolutionary lineage leading to
the taxon / taxa at the end of the branch.
sister taxa
Separate groups of closely related organisms that share an
immediate common ancestor that is not shared by any other group.
internal nodes
A hypothetical common ancestor from which two separate
evolutionary lineages have diverged.
terminal nodes
Individual groups of organisms (taxa) with their own
independent evolutionary lineage.
principle of parsimony
The principle of parsimony states that the simplest explanation to a problem is the
most likely answer. In phylogenetics, it is assumed that traits are more likely to arise
once and be passed down from a common ancestor than for multiple groups of
organisms to develop the same trait separately
