1. Amniotic Egg
Suite of special membranes (we went over these) with various jobs (store nutrients, gas exchange, waste storage)
Shell (in some) for protection + waterproofing, can lay eggs in more exposed locations
Birds evolved hard shell
Mammals dispensed with shell and embryo avoids desiccation by developing within mother.
Shell
Yolk sac
contains nutrients
Embryo
Figure 34-16

2. Dino EGGS
Dino rookery-nests 23ft apart
Lots of parental care
Communal nesters

3. Early mammals split from Synapsids Mammals only surviving lineage of
Rest of Synapsids went extinct at end Permian extinction event (250mya)
Reptiles
ANCESTRAL AMNIOTE Amniotic egg
Synapsids
Mammals

4. Eutherians=Placentals Marsupials Monotremes
WITHIN MAMMALS..
Eutherians=Placentals
Marsupials
Monotremes
Mammals have…Mammary glands... nourish offspring with milk-Ramifications….????
Offspring can grow fast and over a long period...
Don’t have to feed themselves (offspring can be born in locations that don’t support them directly)
Not dependent on abundance of prey
Mom can store energy in the form of fat to feed young

5. Monotremes
Eggs w/ soft shells
echidnas incubate their eggs in their pouch
platypuses incubate eggs in nest
Milk-oozes out of skin onto fur
Highly altricial

6. Marsupials
Born at very premature stage…(highly altricial-equivalent to 8-10 wk old human embryo) (no precocial young)
Shorter period of diffusion of materials between mom and baby
Pouch with nipples inside-permanently attached at start..ex utero development (NOT ALL HAVE POUCHES)

7. Marsupials are much less diverse than placental mammals in terms of range of lifestyles, range of body shapes and where they live.
One hypothesis for why no fully aquatic or flying species has to do with reproduction….

9. Thylacosmilus (left / source) and Borhyaena (right / source).

11. Marsupials reached Australia 50 mya
Placentals were there in Australia but went extinct
Left Marsupials as only mammals

12. One group of mammals=Eutherian=Placentals have a Placenta
One group of mammals=Eutherian=Placentals have a Placenta! Very specialized membranes for transfer of nutrients….transfer of nutrients is high!
Mother’s uterus
Placenta
Allantois
Yolk sac
Embryo
Amnion
Chorion
Figure 34-17

13. Placentals or Eutherians
Chorioallantoic placenta
“even more specialized tissues”-provide nutritional, respiratory and excretory exchange between mom and offspring

14. What cool pouch facts did you learn about (open up pouch paper)??
Gas exchange through skin! Ectothermic! Immune system underdeveloped! No lymph system!
Note:
Is a kind of yolk sac which delivers nutrients
In some species there ARE placenta like organs but not clear whether nutrients are transferred.