BIOL-1040 Lecture Notes - Lecture 19: Thumb, Hominini, Platypus
Document Summary
Vertebrate evolution: vertebrates have a backbone, vertebral column, and are known as craniates. Aquatic animals have gills that trap suspended food particles and filter water: chondrichthyans have a flexible skeleton made of cartilage. Most have flattened scaled covering their skin and secrete a coating of mucus that reduces drag during swimming. On each side of the head is a protective flap known as an operculum, which covers a chamber housing the gills: lobefins are a series of rod-shaped bones in their muscular pectoral and pelvic fins. Amphibians: these include salamanders, frogs, and caecilians. Most are found in damp habitats, while their moist skin supplements their lungs for gas exchange. Many have poisonous glands that may play a role in defense: a frog lays its eggs in water, and during the larval stage, the tadpole, which is a legless, aquatic algae-eater with gills, that undergoes metamorphosis. Amphibians were the first vertebrates to colonize the land.
