Let's Talk About Comparative Reproduction Baby, It's All About Comparative Reproduction Baby.
Yes, if you're reading the title you might be wondering......"what is going on here?" Well, since I'm a new masters student now, I need to be focusing most of my effort on biology and paleontology. Sadly I will be forced to neglect some theological reading, but in the long run, I'll still learn some and be able to disucss it.
If anything, now Lutherans who read this (and anyone else for that matter) can get an inside look into how a scientist works and thinks (even though I reject evolution, I use it in my research, so this is the disclaimer). My thesis will be focusing on (as the title might have pointed out) comparative reproductive systems in animals. You might think, "who cares?" Well, it becomes fascinating when you look at animal groups and wonder why there are so many darn exceptions to all those rules you learned in introductory biology class.
Let's look at it this way: Of the vertebrates, you're always told in high school or college that there are five groups:
1. Mammals-Give birth to live young, except monotremes which lay eggs (termed ovaparous).
2. Birds (Aves)-Lay eggs outside of water
3. Reptiles-Lay eggs outside of water
4. Amphibians-Lay eggs in the water
5. Fish-Lay eggs in the water
Now, for the exceptions: You alread know about the monotremes in mammals, but what about the others? As far as we know, no bird (or dinosaur for that matter) gave birth to live young (termed viviparous). However, squamate reptiles (such as the skink) do give birth to live young, and the character seems to jump around within the different species as one examines their phylogeny (evolutionary history). Similarly, there is a famous Icthyosaur fossil which died during a breached birth, and it is thought (though not completely agreed upon) that plesiosaurs and mosasaurs were viviparous as well because of their inability to come up on land or to descend without oxygen to the depths of the ocean. It is interesting that these ancient marine reptiles were also squamates. There are also snakes which have live young inside of them (see Indiana Jones and the Temple of Doom's famous dinnertable scene if you don't think it's true....cause that's a measure of truth :-/). Finally, sharks lay eggs......or have a yolk in them and give birth to live young after they've developed in that egg (termed ovaviviparity)......or they give birth to live young....complete with a placental structure.
My question is........of the vertebrates (and my advisor hinted that this could be applied to invertebrates.......God help me with the work that's going to be :-(), can a pattern be seen as to why there is sporadic jumping of the character trait of viviparity in these animals? Surely a minor pattern already can be seen: of Reptiles-no archosaurs have viviparity, many squamates do. Some have hypothesized that cold climates contribute to this character.....I would add marine environments for obligate air breathers (such as many of the ancient marine reptiles). Aside from patterns, what tissues do the placenta come from in these different animals......are they the same? How about the umbilical cord and the nutrients it exchanges? Are they the same (or roughly the same) and is the mechanism the same? As you can see, I have a lot of work to do, including dissection and photographing or sketching of vertebrates to see for myself the internal anatomy of many animals (including marsupials and reptiles).
It should prove to be a fun and exciting project, with possible PhD results (if I pursue the ancient marine reptiles) in the future.......yay beer!
If anything, now Lutherans who read this (and anyone else for that matter) can get an inside look into how a scientist works and thinks (even though I reject evolution, I use it in my research, so this is the disclaimer). My thesis will be focusing on (as the title might have pointed out) comparative reproductive systems in animals. You might think, "who cares?" Well, it becomes fascinating when you look at animal groups and wonder why there are so many darn exceptions to all those rules you learned in introductory biology class.
Let's look at it this way: Of the vertebrates, you're always told in high school or college that there are five groups:
1. Mammals-Give birth to live young, except monotremes which lay eggs (termed ovaparous).
2. Birds (Aves)-Lay eggs outside of water
3. Reptiles-Lay eggs outside of water
4. Amphibians-Lay eggs in the water
5. Fish-Lay eggs in the water
Now, for the exceptions: You alread know about the monotremes in mammals, but what about the others? As far as we know, no bird (or dinosaur for that matter) gave birth to live young (termed viviparous). However, squamate reptiles (such as the skink) do give birth to live young, and the character seems to jump around within the different species as one examines their phylogeny (evolutionary history). Similarly, there is a famous Icthyosaur fossil which died during a breached birth, and it is thought (though not completely agreed upon) that plesiosaurs and mosasaurs were viviparous as well because of their inability to come up on land or to descend without oxygen to the depths of the ocean. It is interesting that these ancient marine reptiles were also squamates. There are also snakes which have live young inside of them (see Indiana Jones and the Temple of Doom's famous dinnertable scene if you don't think it's true....cause that's a measure of truth :-/). Finally, sharks lay eggs......or have a yolk in them and give birth to live young after they've developed in that egg (termed ovaviviparity)......or they give birth to live young....complete with a placental structure.
My question is........of the vertebrates (and my advisor hinted that this could be applied to invertebrates.......God help me with the work that's going to be :-(), can a pattern be seen as to why there is sporadic jumping of the character trait of viviparity in these animals? Surely a minor pattern already can be seen: of Reptiles-no archosaurs have viviparity, many squamates do. Some have hypothesized that cold climates contribute to this character.....I would add marine environments for obligate air breathers (such as many of the ancient marine reptiles). Aside from patterns, what tissues do the placenta come from in these different animals......are they the same? How about the umbilical cord and the nutrients it exchanges? Are they the same (or roughly the same) and is the mechanism the same? As you can see, I have a lot of work to do, including dissection and photographing or sketching of vertebrates to see for myself the internal anatomy of many animals (including marsupials and reptiles).
It should prove to be a fun and exciting project, with possible PhD results (if I pursue the ancient marine reptiles) in the future.......yay beer!
posted by Chris | 9:11 PM
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