Vertebrate Evolution

Transcription

1 Vertebrate Evolution Torsten Bernhardt Redpath Museum, McGill University This teaching resource was made possible with funding from the PromoScience programme of NSERC. McGill University 2010

2 History of the Earth Origins of Bacteria Origins of Eukaryotes Phanerozoic (Billions of years) (Millions of years) Paleozoic Mesozoic Cenozoic

3 Chordates archive-day/ Pikaia Tunicates (sea squirts)

4 The First Fish? Haikouichthys

5 Agnathans: Jawless Fish (i) Ostracoderms -armoured, jawless fish -used gills only for respiration -no paired fins, so probably poor swimmers Endeiolepis aneri

6 Agnathans: Jawless Fish (ii) Cephalaspis Ostracoderms went extinct in the Devonian, most likely due to the placoderms (who we ll get to in a minute )

7 Agnathans: Jawless Fish (iii) A modern agnathan: the lamprey

8 Placoderms: Jaws Evolve (i) -Still armoured -Jaws are a major advantage -First live birth -Paired fins phics/page/retail/large/bothriolepis.jpg Bothriolepis

9 Placoderms: Jaws Evolve (ii) Dunkleosteus No teeth

10 Cartilaginous Fish (Chondrichthyes) (i) -Sharks, skates, rays, chimeras -Skeleton is made of cartilage instead of bone -Don t fossilize well -Are thought to have evolved from placoderms Manta ray Great white shark Chimera Fish/chimaera_fish1.jpg

11 Cartilaginous Fish (Chondrichthyes) (ii) Stethacanthus (~360 Mya) Megalodon (~1.5 mya)

12 Bony Fish (Osteichthyes) Nile Perch Betta

13 Bony Fish Ray-finned Fish (Actinopterygii) species, 99% of all fish today -Fins are supported by bony rays Clown fish Brook trout Homalacanthus

14 Bony Fish Lobe-finned Fish (Sarcopterygii) Eusthenopteron -Fins have bones and muscle -Live on the bottom -Not especially diverse, as fish Coelacanth

15 From Fish to Amphibians We think that amphibians evolved from sarcopterygian (lobe-finned) fish. Why is this? One group of sarcopterygians, the osteolepiforms, had nostrils that led to an opening in the roof of its mouth. This allowed air to pass into the mouth and then to paired swim bladders (similar to our lungs). Lungfish, which are modern sarcopterygians, can crawl over land from one water body to another. The sturdy fins of the sarcopterygians have bones much like those in our limbs. Other anatomical features, such as skull bones and teeth, also point to a relationship.

16 From Fish to Amphibians /chap_tut/images/nw0276-nn.jpg Amphibian limb (left) and lobe-finned fish fin (right) /deadanimalblog/pf_tiktaalik.j pg Early amphibians had as many as eight toes; this was eventually reduced to five, or four

17 Amphibians hyostega.jpg Ichthyostega -Early amphibians didn t look like modern amphibians -Three-chambered heart -Had lungs, but also breathed through their skin -Were tied to water for reproduction -Dominant predators in the Carboniferous Acanthostega s/101/eryops1db.jpg Eryops

18 Amniotes Outer envelope Yolk Inner envelope e:chroniosuchusdb126.jpg Amphibian egg Chroniosuchus, which may be an ancestor of amniotes Amniote egg -Amniotes eggs allowed them to reproduce away from water and expand to drier areas -They diverged into two lineages: one would eventually become mammals, the other would become reptiles and birds

19 Mammal-like reptiles (Synapsids) Dimetrodon Gorgonopsids -Ancestors of true mammals -Regulated their temperature -Different types of teeth -Very successful until the end of the Permian

20 The Permian Extinction -The most severe extinction event in the Earth s history -May be related to the Siberian Traps, the largest volcanic eruptions on Earth -96% of species in the oceans go extinct, 70% of vertebrates on land go extinct, 99.5% of all living creatures die -The mammal-like reptiles are severely affected

21 Reptiles -Many different groups -Scales, 3.5 -chambered heart -Almost all lay eggs -Extremely successful in the Mesozoic (which is known as the Age of Reptiles) Scutosaurus views/1519/ jpg saurs/mesosaurus jpg Mesosaurus, one of the first reptiles to return to the sea Coelurosauravus, a gliding reptile aures/coelurosauravus.jpg

22 Crurotarsi -The group that today includes crocodiles -Ruled the world in the Triassic, after the mammal like reptiles were severely affected by the Permian extinction -Were themselves severely affected by the extinction event at the end of the Triassic Postosuchus

23 Other Reptiles een-sea-turtle.jpg s/tokay_gecko.jpg phis_tigrinus_06toad.jpg Green sea turtle Snake Tokay gecko Tuatara /02/henry.jpg

24 Dinosaurs -Were around for 160 million years -Two groups, based on hip structure -May have been warm blooded -Advanced features bones, gait Triceratops Gorgosaurus

25 Dinosaurs

26 Not Just Dinosaurs! (i) Turtles 07/11/sarcosuchus_and_nigersaurus.jpg efeditor/world%27s-biggest-snake-picture.jpg Snakes Crocodylimorphs Lizards Tuatara

27 Not Just Dinosaurs! (ii) as/05/dinosaures/images/pteranodon.jpg Ichthyosaurs Pterosaurs - the first flying vertebrates Mosasaurs Plesiosaurs resfromthedeep/creaturesimages/plesiosaur_4_large.jpg

28 True Mammals -Evolved from the synapsids (mammal-like reptiles) -Vaguely rodent-like, small -Showed up not too long after the dinosaurs -Didn t amount to much in the Mesozoic; lawnmower ecology

29 Archaeopteryx Birds -Evolved from dinosaurs; specifically, the meat-eating deinonychosaurs, which includes Dromaeosaurus -Are technically dinosaurs -Feathers evolved before birds did; T. rex may have been fuzzy -May have outcompeted the pterosaurs and helped drive them to extinction -The second vertebrate group to fly

30 Cretaceous Extinction -Ends the reign of the dinosaurs -Flying and swimming reptiles also go extinct -Many other groups suffer as well -Mammals step into the empty niches!

31 Mammals Take Over (i) nita_bokeron/myfiles/elephant.indricotherium.h uman.jpg umb/7/7a/panochthus_frenzelianus.jpg/800px- Panochthus_frenzelianus.jpg Indricotherium Glyptodont s/images/arsinoitherium1.jpg Arsinoitherium Saber-toothed cat Leptictidium eptictidium_1.jpg

32 Mammals Take Over (ii) Humpback whale Bat