Fish Evolution Part 2. * Fish were the first vertebrates * Tunicates link the invertebrates and...
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Transcript of Fish Evolution Part 2. * Fish were the first vertebrates * Tunicates link the invertebrates and...
Fish Evolution
Part 2
Fish Evolution
Part 2
* Fish were the first vertebrates* Tunicates link the invertebrates and vertebrates
TunicateAnatomy
WaterIn
WaterFecesOvaOut
Ganglion
GillBars
HeartWaterTo Exit
Gonads
Tunicate Life
Cycle
MouthEyeSpot Nerve
Cord
Notochord
GillSlits
Egg
Free-SwimmingLarva
Metamorphosis
Neotany
Egg
Egg
Arm Feeder Gill Feeder
AncestralTunicate Modern Tunicate
AmphioxusModernFish
Primitive ChordateVia Neotany
Fish Evolution
Amphioxus Fish FirstsAmphioxus Fish FirstsAmphioxus Fish FirstsAmphioxus Fish Firsts
• Notochord–Prevents “telescoping”
• Notochord–Prevents “telescoping”
Amphioxus Notochords
No Notochord
With Notochord
Blue MuscleContraction
TelescopedAmphioxus
SwimmingAmphioxus
Amphioxus Fish FirstsAmphioxus Fish FirstsAmphioxus Fish FirstsAmphioxus Fish Firsts
• Notochord–Prevents “telescoping”
–Hanger for organs
• Notochord–Prevents “telescoping”
–Hanger for organs
Notochord
Amphioxus Fish FirstsAmphioxus Fish FirstsAmphioxus Fish FirstsAmphioxus Fish Firsts
• Notochord–Prevents “telescoping”
–Hanger for organs
• Hollow nerve cord
• Notochord–Prevents “telescoping”
–Hanger for organs
• Hollow nerve cord
Nerve Cord Evolution
Starfish: A simple network of nerves.
Earthworm: A network of nerves connected to ganglia
Fish: Hollow nerve cord (spinal cord) and a brain
Amphioxus Fish FirstsAmphioxus Fish FirstsAmphioxus Fish FirstsAmphioxus Fish Firsts
• Notochord–Prevents “telescoping”
–Hanger for organs
• Hollow nerve cord
• W-shaped myotomes
• Notochord–Prevents “telescoping”
–Hanger for organs
• Hollow nerve cord
• W-shaped myotomes
W-Shaped Myotomes
More Efficient Swimming
Amphioxus Overview
MouthGills
Fin-Like Flap
EyeSpot
NotochordNeuralTube
No JawsJunky Fins
Are they Are they Fish?Fish?
•Relict species very similar to the first fish-like animal.
•Most important innovations– Notochord– Hollow nerve chord– W-shaped myotomes
Ostracoderms•500-370 MYA•Single nostril•No paired fins•No jaws•Notochord and rudimentary
vertebrae •Lungs!•Armor for protection
Cephalaspids: Organs for hearing or electrical fields?
Drepanaspis
Cephalaspis
Logania
Logania
Logania
Ostracoderms•500-370 MYA•Single nostril•No paired fins•Notochord and rudimentary
vertebrae •Lungs!•Armor for protection•No jaws
Relict SpeciesHagfish
Lamprey
Ostracoderms Hagfish/Lamprey
•Single nostril•No paired fins•Notochord/vertebrae •Lungs!•Armor for protection•No jaws
Relict SpeciesHagfish
Lamprey
The Opposition
The Home Team
•No jaws for catching prey•Primitive fin arrangements•Stiff armored
bodies
Invertebrates !
Invertebrates Stepped it up a
notch
Opponents got Tougher
Really Tough…
Parastylonorus
Modern Fish
Early Fish
Modern Inverts
•The neighborhood got rougher!
•Most ostrachoderms were out-competed
•Only those in specialized niches survived
Lamprey, Hagfish, Ostracoderms
Jaws Evolved from Gill Arches
Dunkleosteus (placoderm)
Placoderms•Ancestors of Sharks, rays, chimeras
•300-400 mya•Jaws, paired fins, lungs, gill arches
RelictsSeven Gill Shark
Ratfish
Fancier Jaws
There are many relict shark, ray,
and chimera species because…• Jaws and teeth help make
them better able to hunt and defend themselves, then and now
• Paired fins make them better able to hunt and defend themselves, then and now
• It worked 350 MYA and it still works now!
Acanthodians• 440 mya
• Bony skeleton, jaws, gills
• Paired fin evolution
Lobefins: Coelacanth
Acanthostega
AcanthostegAcanthostegaa
Late Devonian (350 Late Devonian (350 mya)mya)
eight fingers and toeseight fingers and toesFish-like features
– Gill-bars like a fish
– No true elbows, knees, wrists or ankles (not weight-bearing)
– Long fin rays around the tail
Tetrapod-like features– Head not joined to shoulder girdle
– Ear-bone (stapes) fits into fenestra (ovalis/vestibuli) in braincase
– Large pelvic girdle, sacral rib
– Femur as large as humerus
– Tibia and fibula attached to ‘ankle’ bones
– Digits on each limb
Major moments in fish evolution
• Amphioxus, the un-missing link– Hollow nerve cord– Notochord– W-shaped myotomes
• Ostrachoderms, the first true fish• Placoderms and Acanthodians
– Jaws – Fancier and fancier– Paired fins – Fancier and fancier
• Descendants of the lobefins conquer land
Ancestral
Tunicate
Amphioxus
Ostracoderms
Placoderms
Acanthodians
Lobefins
reptiles
(Neotany)
HagfishShark
Ray
Bony
Fish Coelacanth
600 mya
400 mya
150 mya
Notochord
Nerve Chord
Fins
Eyes
Armor
Lungs
Paired fins
Jaws
Bony skeleton
•Neotany: What is it, how did it give rise to the first primitive fish-like critter (Amphioxus)•Amphioxus: What are the important fish-like innovations (w-shaped myomeres, hollow nerve cord, notochord)•Ostracoderms: Characteristics and where they fit in fish evolution•Placoderms: Characteristics and where they fit in fish evolution•Acanthodians: Characteristics and where they fit in fish evolution•Fish evolution slide