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 platypus2. Marsupials – pouched mammals;

kangaroo, koalas, wombats, possum3. Placental mammals – young develop

attached to the placenta within mother