BIOL 121 Lecture Notes - Lecture 24: Saber-Toothed Cat, Comparative Embryology, Blastula
Document Summary
Superficially looks similar: stiffened membrane supported by chitinous veins. Bat wings: internal body skeleton covered by membrane of skin; muscles. Homologous, analogous and homoplasic characters are not mutually exclusive. Only homologous characters are used to infer evolutionary relationships of organisms. Thylacosmilus & homoplasious = similar appearance analogous = same function homologous = possessed by their common ancestor . ** saberteeth: homoplasic & analogous but not homologous structures: comparative anatomy (cont. ) Homologous structures (derived from a common ancestor) => infer evolutionary relationships. Vestigial characters (structures of no apparent function) Why have functionless structures in so-called perfectly created animals: (cid:862)rudi(cid:373)e(cid:374)tary orga(cid:374)s(cid:863) Examples of vestigial structures: tail bone (coccyx) & appendix in humans, evolved from organisms which had use for these structures. Other examples of vestigial structures: bones of pelvis & femur in snakes & whales, snakes - no limbs but have vestigial leg bones, evolved from organisms which had use for these structures.
