LIFESCI 1 Lecture Notes - Lecture 13: Convergent Evolution, Yolk Sac, External Fertilization
Document Summary
Most do external fertilization, but some do internal fertilization. Water to land transition: external vs. internal fertilization. On land, external fertilization does not work well. Water to land transition: the incredible amniotic egg! Amniotic egg: embryo surrounded by layers of fluid, one of which is yolk sac that provides nutrients to embryo directly. External membrane prevents dessication, but allows gas exchange. More waterproof skin holding in moisture in organism"s body. Skin has layer of keratin (keratin provides layer of waterproof mist) Sometimes bask in warm temperature to warm up their bodies or go to shade to cool themselves. Snakes lost their limbs based on vestigial traits (leg-bones that are no longer functional) Elastic skin helps them to prey on animals larger than themselves. Sea turtles do not lay eggs in water, go to beach to lay eggs vulnerable. No exam question on the video here. Flight evolved in vertebrate lineage three different times=convergent evolution.
