Phylum Chordata

it is present at some stage in development
At what stage is the notochord present?
gill slits
What kind of pharyngeal pouches do chordata have?
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postanal tail
What kind of tails do chordata have?
segmented muscles and unsegmented trunk
What kind of muscles and trunk do chordata have?
Do chordates have a complete or incomplete digestive tract?
Do most members of the phylum chordata have an endoskeleton of bone or cartilage?
-dorsal hollow nerve cord
-pharyngeal slits
-postanal tail
What are the key distinguishing innovation of the phylum chordata?
pharyngeal slits
What is located between the aortic arches?
it has a fibrous sheath and an elastic sheath
What is the structure of notochord?
-gas exchange across body surface
-usually sessile but can leave burrow and swim
Subphylum Cephalochordata
Are all the species in the subphylum cephalochordata marine filter feeders?
branchiostoma (amphioxus)
What is a popular species of the subphylum cephalochordata?
yes, the exhibit them at some time during development
Do all chordates exhibit all four characteristics?
tunicates (animal encased in tunic or test)
-3,000 marine species
-adult is sessile with only pharyngeal slits
-filter feeders with 2 siphons
Subphylum Urochordata
during the larvae tadpole-like stage
When does the subphylum urochordata exhibit all 4 chordate hallmarks?
yes, they are
Is the subphylum urochordata the closest relative of vertebrates?
to echinoderms
Cephalochordates are more closely related?
rudimentary circulatory system
What kind of circulatory system do tunicates have?
simple nervous system
What kind of nervous system do tunicates have?
Are tunicates hermaphroditic?
complete gut
What kind of digestive system do chordates have?
What kind of circulatory system do chordates have?
gills; lungs
What kind of respiratory system do chordates have?
What kind of excretory system do chordates have?
well-developed brain; dorsal hollow nerve cord
What kind of nervous system do chordates have?
sexual; rarely pathogenetic
What kind of reproduction system do chordates have?
endoskeleton of cartilage or bone
What kind of body support do chordates have?
animals with backbones
Which species in the Craniates doesn’t have a backbone?
-closed circulatory system with ventral heart of 2-4 chambers
-endoskeleton of cartilage or bone
-vertebral column that surround the dorsal nerve cord
-notochord only present during embryonic development
-2 pairs of limbs or fins in all except the jawless fish
Craniata (The Craniates)
-jawless, finless, marine fish that lack vertebrae but have a skull
-notochord and a cartilaginous skull
-essentially blind but with a keen sense of smell
-copious amount of slime
Class Myxini
-lack hinged jaw and true appendages (agnathan= jawless)
-have a notochord and rudimentary vertebral column
-found in marine and freshwater
-marine lampreys are parasitic as adults
Class Petromyzontida
jawed vertebrates
-hinged jaw developed from the pharyngeal arches
-evolution resulted in the modification of an existing feature to form the jaw
*some gill arches were lost, some modified
sharks, skates, rays (sub-class Elasmobranchii)

-have a skeleton of flexible cartilage
-derived character within the Chondrichthyes
-developmental change prevented ossification of cartilage
-sharks among earliest fish to develop teeth (but are not set into jaw)

Class Chondricthyes (cartilaginous fish)
because they have an oily liver
Why are sharks denser than water?
they must keep swimming to maintain buoyancy and breathing
If sharks are denser than water how do they float?
it is a pressure wave detection
What is a lateral line and why do sharks use it?
oviparous- lay eggs
ovoviviparous- egg retained in female, no placenta
viviparous- eggs developed in uterus, placenta nourishes young
What are the internal fertilization- after fertilization alternatives of the class chondricthyes?
fusiform (spindle-shaped, tapering at both ends)
-heterocercal (unequal lobes)
-caudal fin (tail)
What type of body form do the sub-class elasmobranch (sharks and rays) have?
Do the elasmobranch have a swim bladder?
2-chambered heart
How many chambered heart do elasmobranch have?
bony fish
actinopterygii- ray-finned fish
actinistia- coelancanths
dipnoi- lungfish
What are the three living class of Osteichthyes (bony fish)?
ray-finned fish
Coelacanths are grouped in Actinistia and the lungfish are grouped in dipnoi, but what other group can they be grouped in?
homocercal (equal lobes) tail
What kind of lobes do bony fish have?
Do bony fish have a swim bladder?
Is the fertilization of bony fish usually internal or external?
ray-finned fish
-includes all bony fish except coelacanths and lungfish
-fins supported by thin, bony, flexible rays
Actinopterygii characteristics
-believed extinct until 1938
-special joint in skull gives powerful bite
-swim bladder filled with oil rather than gas (still used for buoyancy)
Actinistia characteristics
-3 genera with 6 species
-live in oxygen-poor freshwater
-both gills and lungs (can drown if unable to breathe air)
-muscular lobes fins allow them to traverse land when lake dries out
Dipnoi characteristics
gnathostomes with four limbs
-vertebral column strengthened, hip and shoulder bones braced against backbone
-relatively simple changes in gene expression, especially hox genes
they evolved adaptation for locomotion, reproduction, and to prevent desiccation
How did tetrapods transition to land?
sturdy lobe-finned fishes
What led to the evolution of animals with four limbs?
limb formation from proximal to distal
Hox genes 9-13 work together to specify?
-specific hox genes are responsible for determining limb formation in mice
-mutation in the genes HoxA-11 and HoxD-11 resulted in the loss of the radius, ulna, and some of the carpals
-relatively simple mutations can control relatively large changes in limb development
What is the explanation for limb length in tetrapods (Davis and Colleagues case)
are the first of the tetrapod taxa
-amphibians, reptiles, birds, and mammals
Craniata- Class Amphibia
successfully invaded land but must return to water to reproduce
-buccal (mouth pumping to force air into lungs)
entirely freshwater or terrestrial
What kind of environment do amphibians live in?
-bony skeleton
-variable numbers of vertebrae
-ribs present or absent
-usually four limbs
*wide variety of body forms*
What kind of body do amphibians have?
-three-chambered heart
-double cirrculation
What kind of circulatory system do amphibians have?
-elongate, limbless, burrowing creatures found in tropical forests and streams
Order Gymnophiona (apoda) *amphibians*
salamanders and newts
-typically small
-usually aquatic larvae and terrestrial adults
Order Caudata (Urodela)
frogs and toads
-tails absent in adults
-head and trunk fused together
-6-10 vertebrae, with urostyle
-fertilization external, aquatic, amplexus
-egg >larva (tadpole) > adult
Order Anura (Salienta)

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