USABO Biosystematics Final Exam Questions 2024.

USABO Biosystematics Final Exam Questions 2024. Calcarea, Silicea (sponges) - ANSWER Lack true tissues; have choanocytes (collar cells-flagellated cells that ingest bacteria and tiny food particles) Cnidaria (hydras, jellies, sea anemones, corals) - ANSWER Unique stinging structures (nematocysts) housed in special cells (cnidocytes); diploblastic, radially symmetrical, gastrovascular cavity Plathyhelminthes - ANSWER Dorsoventrally flattened, unsegmented acoelomates; gastrovascular cavity or no digestive tract Rotifera (rotifers) - ANSWER Pseudocoelomates with alimentary canal (digestive tube with mouth and anus); jaws (trophi) in pharynx; head with ciliated crown Lophophorates: Ectoprocta, Brachipoda - ANSWER Coelomates with lophophores (feeding structures bearing ciliated tentacles) Mollusca (clams, snails, squids) - ANSWER Coielomates with three main body parts (muscular foot, visceral mass, mantle); coelom reduced; most have hard shell made of calcium carbonate Annelida (segmented worms) - ANSWER Coelomates with segmented body wall and internal organs (except digestive tract, which is unsegmented) Nematoda (roundworms) - ANSWER Cylindrical, unsegmented pseudocoelomates with tapered ends; no circulator system; undergo ecdysis Arthopoda (crustaceans, insects, spiders) - ANSWER Coelomates with segmented body, jointed appendages, and exoskeleton made of protein and chitin