BIO 217 Lecture Notes - Lecture 10: Gnathostomata, Vertebrate, Myomere
Document Summary
Stated with a group of fishes 530 mya. Agnatha: jawless fish, developed scales, moved by tail fin, 1st fish that diversified, small # of species. Eurypterids: main predators, large arthropods, aka sea scorpion. Lamprey (classpetromyzontida): eel-like body, no limbs, no scales, teeth around mouth and on tongue, parasites, colonized in the great lakes and destroyed lake trout population. Hagfish (class myxini): scavengers of the sea , aka slim eels, produce slim from mucus sac, avoid predators by slim, tie themselves in knot, cleanup bottom of ocean (eat carcases) New group after agnatha brought in new adaptation: jaws. Jaws come from gill arches in agnatha that were modified and became jaw. Scales around mouth became modified as teeth. No more placoderms today, now the modern fish are Chondrichthyes: skeleton made up of cartilage instead of bones, sharks, rays, ratfishes, Subclass actinopterygii- majority of fishes, ray fin fishes. Movement: when you push on water, reaction force pushes back opposite direction.
