Terrestrial Vertebrates Section 32.2

Early Reptiles Important adaptations to terrestrial life that amphibians do not have: 1. Water tight skin 2. Water tight eggs

Dinosaurs Beginning 235 million years ago Pangaea broke up and provided many different habitats for dino evolution Reasons for dino success: 1. Leg structure – position directly under the body 2. Drought resistance 3. Extinction of other competing animals

Dino debate Ectotherms – ‘cold-blooded’; body temp changes with surroundings  need less food; modern fish, amphibians, reptiles Endotherms – ‘warm-blooded’; body temp remains the same  need more food; modern birds & mammals Debate about dinos – which one? Reason(s) for dino extinction?  Climate became cooler  Asteroid hit earth and caused loss of plant life  Success of other species  Some combination…

Evolution of Birds Archaeopteryx – oldest bird fossil; basically a dinosaur with feathers Key feature of birds – feathers Today there are more bird species than any other terrestrial vertebrate They live in a wide variety of habitats and are adapted to many different lifestyles

Modern Reptiles Only 4 remaining orders of reptiles: 1. Turtles 2. Snakes & lizards 3. Tuatara 4. Crocodilians – crocodiles and alligators

Along came mammals Appeared about 220 million years ago Key features: fur and mammary glands Three groups of modern mammals: 1. Monotremes – egg laying mammals; spiny anteater and duck-bill platypus 2. Marsupials – pouched mammals; kangaroo, koalas, wombats, possum 3. Placental mammals – young develop attached to the placenta within mother