Chordata. Phylum Chordata Bilateral, Deuterostomate development Notochord Dorsal hollow nerve cord...
-
Upload
augustine-charles -
Category
Documents
-
view
216 -
download
1
Transcript of Chordata. Phylum Chordata Bilateral, Deuterostomate development Notochord Dorsal hollow nerve cord...
Chordata
Phylum Chordata
• Bilateral, Deuterostomate development
• Notochord
• Dorsal hollow nerve cord
• Pharyngeal slits
• Muscular Post-anal tail
• Segmented musculature– Repeating units called somites
Chordate features
• Oldest group ( ancestral) Urochordata
• The Tunicates, Sea Squirts
• Chordate Features found in larval phase
• Aid in dispersal, adults are sessile.
• Today’s sessile tunicates are derived trait
Chordate Phylogeny
Subphylum Urochordata
• Only larva has chordate characteristics
#63-x-section #65
Tunicates
Tunicate larvae
Tunicates
Fig. 24.3, p. 385
nerve cord notochord
gut
oral opening
atrial opening (water that passed through pharynx leaves this way)
pharynx with gill slits
Subphylum Cephalochordata
• Come about by Paedogenesis (?)
• Precocious sexual maturity in larvae
• Adults now have all the chordate traits, and are motile
• The lancelets have only a slight swelling , “anterior ganglia’ brain?
Subphylum Cephalochordata
# 66
Amphioxus
Chordate Phylogeny
• Cephalized Chordates– Brain, eyes, etc.– Skull
• Two sets of Hox genes• Neural Crest –
– Infolding of ectoderm– Cells spread through developing body– Form neurons and other features
• Teeth, facial bones,
• Pharanygeal slits paired with muscles & nerves that pump water through slits
• More active metabolism
Subphylum Craniata
Jawless craniate
• Mixini – the hagfishes (not a fish)– Have cartilagnous, skull and notochord
Class Mixini
Super Class - Vertebrata
• More extensive skull
• Backbone composed of vertebrae
• Originally prongs of cartilage dorsally along nototchord protecting nerve chord
• Later took over mechanical role of notochord
• Later fins and other appendages form along vertebrae
Chordate Phylogeny
ClassCephalaspidomorphi
• Lampreys
• Have cartilaginous vertebrae-like extensions along notochord
• Still jawless
Gnathostomes• Vertebrates with true jaws• Additional Hox gene cluster• Larger brains, better sense of smell sight• Lateral line system to sense water
movement • Mineralized endoskeleton• Two sets of paired appendages.
• these paired appendages first functioned in swimming.
• In tetrapods, the appendages are modified as legs on land.
Class Chondrichthyes
What’s New in Bony Fish
• Bony Skeleton
• Single Gill Opening – Operculum bellows water over gills
• Swim bladder – gas from blood fills bladder, released to control buoyancy
Swim Bladder
Gas Gland
Muscular Valve
Lobed-finned fish vs. Amphibian Bones
Class Amphibia
REPTILIA - Amniotes
MAMMALS
Monotremes
• Warm blooded
• Have hair
• Lay eggs
• Young hatch and live outside mother
• Make milk in glands, no nipples
• Live birth to underdeveloped young. Placenta forms, but not a long a time.
• Young crawl to pouch• Physically attach to nipple in pouch
and feed off milk, finish development while nursing.
• Stay with mother in pouch until able to survive outside
Marsupials
Eutherian mammals
• “Placental mammals”- live birth
• Young held inside past egg feed development
• feed trough an umbilical attachment to the placental
• Born more developed than marsupials
• Feed off milk from breast- Not physically attached to nipple