BIO 201 Lecture Notes - Lecture 24: Cestoda, Coelom, Evolutionary Arms Race
27 Apr 2017
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Animal body plan: 5 key characters (1) symmetry (states: absent, radial, bilateral) (2) body cavity type (states: coelom absent, present) (3) segmentation (states: absent, present) (4) external appendages (states: absent, present) (5) nervous system (states: absent, net, central) Porifera: sponges: no symmetry, no tissues, no coelom, no nervous system, no appendages. Cnidarian ecology: tropical beaches are often made by cutting down mangrove forests. Bilaterians: protostomes: bilaterally symmetrical, two triploblastic monophyetic groups: protostomes and deuterostomes, protostomes have far more species and individuals. In protostomes, the embryonic blastopore becomes the mouth as the animal develops. What factors could explain protostome success: factors that have contributed to protostome species diversity: Parasitism: evolved repeatedly; protostomes parasitize plants and animals. Diverse feeding structures: allow species to take advantage of many food sources. Hard body coverings (exoskeletons and shells): evolved independently in many groups. Better locomotion: allowed prey to escape and predators to capture prey.
