EEB386H1 Lecture Notes - Lecture 9: Arms Race, Precocial, Anseriformes
Document Summary
Once successful in mating, need to reproduce. Oviparity as a reproductive strategy: only strategy, eggs outside body. Cleidoic egg: shelled egg, feature of birds but also turtles and crocodiles. Developmental variation: birds develop quickly relative to mammals. Challenges for oviparity: protect embryo, keep it warm so it develops, eliminate wastes, maintain water balance (and oxygen balance) In some ways, thoughts that oviparity isn"t as efficient (i. e. why don"t they just retain the egg inside) Maybe some constraints: flight? (can"t have live birth? but doesn"t hold in terms of bats) Not necessarily better or worse than viviparity. Birds don"t retain eggs at all in bodies. How they solve challenges of oviparity: egg incubation (sit on it to keep warm, nest construction. Behavioural skills + tools (beak) to do this: albumen provision. Ensuring there"s enough water for embryo development. So pre-pack water into egg (= egg white: calcareous eggshell. Get around problem of toxic things in embryo by excreting uric acid.