POLI 2057 Chapter : The Elements Of International Relations Cont. 2
Document Summary
Gill slits (grooves) contribute to the formation of the lower jaw: as an example, observe a five-week-old human embryo picture, invertebrate chordates. Lancelets are fishlike filter-feeders: adults and larvae exhibit all key chordate features. Protects nerve cord and brain: vertebrate adaptations, several adaptations have allowed vertebrates to successfully invade most habitats. Endoskeleton that can grow and repair itself. Jaws to allow these animals to exploit a much wider range of food sources. Increased size and complexity of the brain and sensory structures: major vertebrate groups, earliest vertebrate fossils were found in 530-million-year-old rocks. Resembled lancelets with a brain, skull, and eyes. Present-day vertebrates include lampreys, cartilaginous fishes, ray-finned fishes, coelacanths, lungfishes, amphibians, reptiles, mammals: jawless fishes. Jawless: have eel-shaped bodies and smooth scale-less skin. Marine forms must return to fresh water to spawn: some species are parasites of larger fish. Rasping teeth on tongue used to suck blood and body fluids.
