Evolution of Tetrapods and Amniotes

Lung-like sacs

Evolved to supplement gills in vertebrates.

Lobed-limb vertebrates

Developed muscular fins for shallow water support.

Coelacanths

Living fossils thought extinct 65 million years ago.

Lungfishes

Survive in mud; possess lungs and gills.

Tetrapods

Ancestral group adapted for terrestrial life.

Amphibians

7,000 species; tied to moist habitats.

Anurans

Frogs and toads; greatest amphibian diversity.

Neoteny

Retention of juvenile traits in adults.

Viviparous

Species giving birth to well-developed young.

Amniote eggs

Water-retaining eggs with protective membranes.

Extraembryonic membranes

Aid gas exchange and protect developing embryos.

Viviparity

Embryo develops inside the mother's body.

Reptiles

19,000 species; includes birds, dinosaurs.

Lepidosaurs

Includes squamates and tuataras.

Squamates

Lizards and snakes; mostly carnivorous.

Crocodilians

Carnivorous reptiles; build nests on land.

Dinosaurs

Dominated land for 150 million years.

Theropods

Bipedal dinosaurs; ancestors of modern birds.

Endothermic

Ability to regulate body temperature metabolically.

Palaeognaths

Flightless or weak flyers among modern birds.

Neognaths

Most modern birds capable of flight.

Feathers

Lightweight structures for insulation and flight.

Archaeopteryx

Early bird with claws; lived 150 million years ago.

Metabolic rates

High rates support energy-intensive flight.

Plant dispersal

Birds aid in spreading plant seeds.

Hollow bones

Lightweight structure in birds for flight.

Bird lungs

Allow continuous airflow for efficient gas exchange.