VERTEBRATES, FISH → LAND, REPTILES

Chordate characteristics

Notochord, dorsal hollow nerve cord, pharyngeal slits, post-anal tail, segmented muscles

Jaws evolution

fusion of skeletal rods supporting pharyngeal slits

Fish characteristics

Gills, lateral line, fins, scales, streamlined body

Chondrichthyes

Cartilage fish (sharks, rays); jaws, paired fins, must swim to avoid sinking

Osteichthyes classes

Actinopterygii (ray finned)
Actinista (lobe finned)
Dipnoi (lungfish)

Tetrapod evolution

From lobe-finned fish with lungs and muscular fins

Adaptations for land

Limbs with digits, lungs, stronger skeleton, neck, pelvic girdle attachment

Amphibian characteristics

Moist skin, external fertilization, water-dependent reproduction

Amphibian orders

Apoda (no legs)

Anura (frogs)

Urodela (salamanders)

Amniotic Eggs

Protects embryo from drying out, allows land reproduction, includes membranes for gas exchange and waste

Amniote phylogeny

Split into synapsids (mammals) and diapsids (reptiles + birds)

Reptile Characteristics

Keratinized skin, internal fertilization, amniotic egg, strong kidneys, cloaca

Lepidosaurs

Lizards, snakes; overlapping scales, no upright posture, attached teeth

Turtles

Shell formed from fused ribs; anapsid (no skull openings)

Dinosaur Groups

Sauropods (long neck herbivores), Theropods (carnivores → birds), Ornithischians (herbivores with large guts)

Marine Reptiles

Ichthyosaurs (fish-like swimmers),
Plesiosaurs (flipper swimmers),
Mosasaurs (giant, predatory, sea lizards)

Warm blooded evidence

Feathers, bone growth rates, active metabolism

Warm blooded groups

Birds + mammals

Endothermy vs Homeothermy

Endothermy = produce heat
Homeothermy = maintain constant temp

Bird Characteristics

Feathers, hollow bones, air sacs (one way air flow), 4-chambered heart, high metabolism, no teeth, one ovary, highly social

Synapsid

1 opening behind eyes (mammals)

Diapsids

2 openings behind eyes (reptiles/birds)

Anapsid

no openings behind eyes (turtles)

Vertebrates

Chordate with backbone (vertebrae), skull, and more complex nervous system

Eurypterid

Extinct sea scorpions; early arthropods that first moved onto land

Echinodermata

Deuterostome phylum (starfish, sea urchins); radial symmetry as adults

Pharyngeal Slits

Openings used for feeding/respiration in early chordates

Lampreys

Jawless vertebrates that attach to fish and feed on blood

Hagfish

Jawless scavengers; have skull but very simple vertebrae

Cyclostome

Group of jawless vertebrates (lampreys + hagfish)

Gnathostome

Jawed vertebrates; includes most vertebrates

Lobed finned fish

Fish with muscular fins; ancestors of tetrapods

Air bladder (swim bladder)

Gas-filled organ for buoyancy control

Lateral Line

Sensory system detecting water movement and pressure

Archosaurs

Group including crocodiles, birds, and dinosaurs; upright posture + socketed teeth

Plesiosauria

Marine reptiles with long necks and flippers; swam like sea turtles

Ichthyosaurus

Marine reptiles with torpedo-shaped bodies; swam like fish using tail propulsion

Pterosauria

Flying reptiles (NOT dinosaurs); had wings supported by elongated finger

Dinosauria

Group of reptiles that dominated Mesozoic; includes theropods, sauropods, ornithischians

Archaeopteryx

Transitional fossil between dinosaurs and birds; had feathers + teeth

Subclass Ave

Modern birds; flying dinosaurs with feathers and air sacs