BIOL 1004 Lecture Notes - Lecture 14: Mesoderm, Bivalvia, Archenteron
8 Dec 2017
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Animals (metazoan): 1. 3 million living species of animals. Shared derived characteristics: extracellular matrix, somatic division of labours, sperm and ova. Closest relatives of animals are choanoflagellates (due to their almost indistinguishable collar cells compared with sponges) Water flows in little holes and out big holes of inside of sponges. Current is caused by collar cells which performs all digestion of food particles inside the cell. Sponges are efficient suspension feeds (capturing food particles suspended in water passing through their body). Not (cid:272)o(cid:373)ple(cid:454), do(cid:374)"t ha(cid:448)e (cid:373)a(cid:374)(cid:455) (cid:272)ells, la(cid:272)k true tissues a(cid:374)d orga(cid:374)s. Spicules are like shards of glass in the body to protect it against predators, this is why not many species eat sponges. Bilaterialia (bilateral animals) shared derived characteristics: triploblastic, bilateral symmetry. Eumetazoa (true animals): all animals except sponges and few others belong to this clade with true tissues. Bilateral symmetry: can make a mirror image if split in half (these animals are more active and have a cns)
