BIOL1030 Lecture Notes - Lecture 6: Appendicular Skeleton, Chondrichthyes, Gnathostomata
Lecture 6 notes- History of Life on Earth
The Vertebrates
First appeared in fossil record about 530 mya during Cambrian Explosion (Palaeozoic Era)
Had a basic fish-like body plan with an internal axial skeleton, based around a skeletal rod
(notochord)
Were jawless (agnathans- no jas)
Filter feeders
AGNATHANS
Modern representatives:
Hagfish
Lamprey
Highly modified forms of feeding
Jawed vertebrates
Mid-Palaeozoic- appearance of jaws and appendicular skeleton (pectoral and pelvic)
Diversification/radiation of the fishes
Significant evolutionary innovations:
- Greater diversity in body shape and size
- New feeding modes
- New modes of swimming/better control
DEVONIAN- Age of the Fishes
CHONDRICHTHYES- the cartilaginous fishes
Sharks, rays, skates, ratfish (chimaeras) and sawfish
Cartilaginous skeleton
find more resources at oneclass.com
find more resources at oneclass.com
Actinopterygii- ray finned fishes
Bony endoskeleton
Vast array/diversity of body shapes and sizes
Huge biomass
FIRST LAND VERTEBRATES
Colonisation of land by vertebrates (375 mya)
Fins evolved into limbs
Strengthening of pectoral and pelvic girdles
Support weight of body on land
Sarcopterygii
Modern representatives:
LOBE-FINNED FISHES- the coelacanth, the lungfishes
Presence of muscular pectoral and pelvic fins, supported by extensions of body skeleton
EVOLUTION OF LUNGS- SIGNIFICANT EVENT IN VERTEBRATE EVOLUTION (diverticulum of the
oesophagus)
TETRAPODS
Three groups of modern amphibians:
1. Anurans (frogs and toads- no tail
2. Caudata tailed- salamanders and newts)
3. Apoda (caecillians)
Modern amphibians- representative of transition to land
Requirement to keep ties with water
Aquatic and terrestrial existence (amphibian= two lives)
Moist skin- prone to desiccation
Eggs- no protective covering to reduce desiccation
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Lecture 6 notes- history of life on earth. First appeared in fossil record about 530 mya during cambrian explosion (palaeozoic era) Had a basic fish-like body plan with an internal axial skeleton, based around a skeletal rod (notochord) Mid-palaeozoic- appearance of jaws and appendicular skeleton (pectoral and pelvic) Greater diversity in body shape and size. Presence of muscular pectoral and pelvic fins, supported by extensions of body skeleton. Evolution of lungs- significant event in vertebrate evolution (diverticulum of the oesophagus) Three groups of modern amphibians: anurans (frogs and toads- (cid:862)no tail(cid:863)(cid:895, caudata (cid:894)(cid:862)tailed(cid:863)- salamanders and newts, apoda (caecillians) Scales (layers of keratin) - a waterproof barrier. Arise of many new life forms including vertebrates. Colonisation of land- plants, simple animals and vertebrates. Continents were joined into pangaea by end of paleozoic era- ends with permian extinction. Continental drift- split of pangaea, laurasia and gondwana- promoted speciation as a consequence of geographic isolation.
