BIOL3030 Lecture Notes - Lecture 31: Placenta, Matrotrophy, Yolk Sac
18 Apr 2017
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Squalus acanthias: eggs develop from own yolk and born live. Oxygen: placenta, low partial pressure from mother. Maxilla: move mandibula in flapping motion to get oxygen. Nutrition from mother but born as eggs. After birth they get lactose from mom. Egg develops trophonomata: pokes out of gut and attaches to inside of uterus. Sac surrounding yolk penetrates wall of uterus: Oophagy: eating eggs, first embryo start eating later embryos. Placental matrotrophic viviparity in amniotes through placenta. Adhere to mother: vitelline: develop within tissues. Cells and tissue fuse: develop envelope to fuse cell boyd/dna with another cell. Oxygen: membranes are so close and exchange everything. But no evolution in birds or reptiles. When depleted: yolk penetrates tissue of mother. Indirect: mature form is different from larva form. Selective advantage: transition into different life form. Tadpoles got fed thyroid, up regulated all growth and matured. Responses to thyroid hormones during amphibian metamorphosis. Can turn off and on to delay development: tadpole.
