BSC 196 Lecture Notes - Lecture 12: Centipede, Myriapoda, Herbivore
Document Summary
By far the two most successful animal phyla. Mollusks were well-established by then, may have first appeared about 555 mya: cephalopod mollusks dominated the seas from 470-65 mya, and trilobite arthropods from 521- Second-(cid:373)ost spe(cid:272)iose a(cid:374)i(cid:373)al group (cid:894)85,000 exta(cid:374)t spe(cid:272)ies k(cid:374)o(cid:449)(cid:374)(cid:895). Na(cid:373)e (cid:373)ea(cid:374)s (cid:862)soft (cid:271)odies(cid:863): basic body plan has a head/foot (for locomotion), a visceral mass (contains organs), and a. Found in marine, freshwater, terrestrial habitats. mantle/shell (for protection and preventing desiccation). Likely the most ancestral group, resemble generalized mollusks. Deep sea (cid:862)li(cid:448)i(cid:374)g fossils(cid:863): gills provide an increase in surface area for gas exchange (respiration), univalve (1 shell), limpet-shaped, not contorted, most diverse mollusks (80% of all species). Exhibit 180 torsion of body: anus above the mouth, can withdraw head into shell easily. Slugs have reduced or lost their shells: nautiluses, cuttlefish, squids, octopuses. Led to their diversity: many are burrowers, using their muscular foot. Shell has two halves (hence bivalve), made of calcium carbonate with a hinge.
