Ch. 4: Teeth Everywhere

Chris OConnor · Posted: Sat Apr 26, 2008 6:56 pm Post subject: Ch. 4: Teeth Everywhere

Ch. 4: Teeth Everywhere

Please use this thread for discussing Ch. 4: Teeth Everywhere.

President Camacho · Posted: Wed May 21, 2008 11:42 am Post subject:

If they know what goes into bones to make them super hard - hydroxyapatite- why don't they start making human bones even harder? This must go against some government regulation. I wouldn't mind going back in time and havng my DNA changed around so that my bones have a little more hydroxyapatite in them. Why can't they do this for women with weak bones?

I wish Shubin in this chapter really stressed the reptile/mammalian break. I know there probably wasn't just one break but several instances where breaks manifested themselves. Listing them would have been cool. I also know that mammal/reptile is just nomenclature war but showing the gradient would have helped me to picture how one became the other.

I like how teeth seem to be the first bones ever created - to eat! Wow. Very cool to know this. Then they moved back and became a defense (scales, shell plates)! Then I guess they moved inside and became vertebrae. Now where are they going to go? hahaha Are we going to become bone people? Awesome.

Ostracoderms and conondonts were found at about the same time period - I believe 500 million years. If this is so then how could they know which came first - teeth for eating or bones for protection?

Saffron · Posted: Fri May 23, 2008 9:03 pm Post subject:

Camacho:

Saffron · Posted: Fri May 30, 2008 4:23 am Post subject:

It is incredible that what makes each specie different from each other and in fact males from females is the genetic switches. I've always been fascinated by human sexuality and gender differences. I took a class in college on human sexuality (I still have the textbook, written by the professor that taught the class, Janet Shibley Hyde) and one of the very first topics we covered was prenatal sexual differentiation. All life begins as female. The only difference between a fertilized egg that will become female and the fertilized egg that will become male is the sex chromosome. The embryos of males and females remain undifferentiated until about 7 weeks post conception. At this point all the basic structures that will become the sex organs are in place. What I find amazing is that the structures are identical in males and females, until the switches (testosterone) are activated. What this means is that for every part of the male reproduction system there is a corresponding part in the female. You can match the genitalia of males to females duct by duct and nerve ending by nerve ending. Some of the structure matches are obvious, gonads and ovaries, male glans (head of the penis) and female glans (clitorides). Some not, the tissue that becomes the shaft of the penis is the same tissue in the female that becomes the lining of the vagina (all the internal duct work and the nerve networks match as well).

Interestingly, if the cells of a male (XY) embryo are androgen (testosterone) insensitive the embryo will develop into what appears to be female fetus. People with Androgen insensitivity syndrome are genetically male, but can present externally as completely female or as hermaphrodites . Actually, even more than just female - super female. These women tend to be tall, large breasted, narrow hipped, perfect complexion (high levels of testosterone is associated with acne) and facially beautiful - think super model. These women are also infertile.

Robert Tulip · Posted: Fri May 30, 2008 3:32 pm Post subject:

Saffron · Posted: Fri May 30, 2008 8:19 pm Post subject:

Robert Tulip wrote:

President Camacho · Posted: Fri May 30, 2008 8:27 pm Post subject:

I have a couple Ostracoderms in my back yard and if they were to see that comment they would be pretty pissed. Don't worry, I don't let them play on my computer. Lucky for you.

Robert Tulip · Posted: Sat May 31, 2008 12:57 am Post subject:

Robert Tulip · Posted: Sat May 31, 2008 1:07 am Post subject:

Indigo · Posted: Sat May 31, 2008 9:19 am Post subject:


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