Chordates: Chordate Phylogeny
CBJ Ch. 34 - 1
sister taxon to chordates
basal chordates
Jawless vertebrates
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Chordate Phylogeny & Evolution of Gnathostomes and Osteichthyes, Lecture notes of Biology
A comprehensive overview of Chordate Phylogeny, focusing on the evolution of Gnathostomes and Osteichthyes. Topics covered include the sister taxon to Chordates, basal Chordates, Jawless Vertebrates, Gnathostomes, Chondrichthyes, Osteichthyes, and various fish lineages. Discussions include the development of skeletons, tooth structures, reproductive adaptations, and respiratory systems.
What you will learn
- How did the respiratory systems of Chondrichthyes and Osteichthyes evolve?
- What is the evolutionary history of Chordates?
- What are the differences between Chondrichthyes and Osteichthyes?
- How did the development of skeletons impact the evolution of fish?
- What are the various reproductive adaptations in Chondrichthyes?
Typology: Lecture notes
2017/2018
1 / 32
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Chordates: Chordate Phylogeny
CBJ Ch. 34 - 1
sister taxon to chordates
basal chordates
Jawless vertebrates
2
Gnathostomes: Chondrichthyes
• Chondrichthyes: cartilaginous fish
– All with skeleton of cartilage
• ancestors had mineralized bones
Gnathostomes: Chondrichthyes
- (^) bone minerals lost to reduce density
- buoyancy raised by liver oils & active swimming
CBJ Ch. 34 - 5
Gnathostomes: Chondrichthyes
- (^) Most are active predators, marine
CBJ Ch. 34 - 7
great white shark^ great white shark
hammerhead shark^ hammerhead shark
spiral valve increases surface area for digestion & absorption!
spiral valve increases surface area for digestion & absorption!
nostril^ nostril eye^ eye
bony teeth^ bony teeth
Gnathostomes: Chondrichthyes
- (^) but a few filter-feed; some live in fresh water
CBJ Ch. 34 - 8 whale shark , a filter-feeder whale shark , a filter-feeder
Gnathostomes: Chondrichthyes
- (^) Some ovoviviparous: egg retained within mother; embryo fed by egg yolk ;
live birth
CBJ Ch. 34 - 10
Gnathostomes: Chondrichthyes
- (^) Some viviparous: embryo fed directly by maternal tissue; live birth
“^ “umbilical cord”umbilical cord”
Gnathostomes: Chondrichthyes
• manta raymanta ray
sting ray^ sting ray
skate^ skate
skate teeth for grinding mollusks^ skate teeth for grinding mollusks
Gnathostomes: Chondrichthyes
CBJ Ch. 34 - 14
gill slits^ gill slits
mouth^ mouth
underside of manta ray
(filter-feeders)
underside of manta ray
(filter-feeders)
Gnathostomes: Chondrichthyes
sawfish underside^ sawfish underside
mouth^ mouth^ gillsgills
Gnathostomes
“bony fish”
ray-finned^ ray-finned
coelocanth
lungfish lobe-finned^ lobe-finned
Gnathostomes: Osteichthyes
- (^) first lungs helped fish in low-O 2 freshwater
- swallowed air into digestive tract
- outpocketing of esophagus increases surface area
- (^) later, lungs modified into swim-bladder for buoyancy
a swim bladder is a “lung derivative”
a swim bladder is a “lung derivative”
Gnathostomes: Osteichthyes
- (^) Skeletons remain mostly ossified (mineralized)