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Physiology & Medicine / Re: Need help finding a humorous mapped Y chrom. in Science

« on: 23/08/2012 06:06:10 »

Ha!  That must be it (or a facsimile).

You're the best!  Thanks.

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Physiology & Medicine / Need help finding a humorous mapped Y chrom. in Science

« on: 21/08/2012 23:42:59 »

I was reading Matt Ridley's book Genome, in it he mentions that Science published a humorous image of a Y chromosome mapped for genes pertaining to quintessential male behaviors.  Of course it was fictional and meant to be funny.  In Matt's book he hints that this was published somewhere between 1990 to potentially 2005.  I've done some searching but can't come up with it.  If anybody knows exactly when this was published, please let me know!  I'd love to share it with my students, who are mostly female, to inject a bit of levity into one of my lectures.

thanks!
matt

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Plant Sciences, Zoology & Evolution / Re: Temp-dependent sex determination in reptiles - whole generations the same sex?

« on: 18/08/2012 00:27:01 »

A "whole generation" is just 1 year. If the animals expect to live much longer than that it doesn't matter much.

Yes, I know.  That is why I originally said "for short-lived species"

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Plant Sciences, Zoology & Evolution / Re: Temp-dependent sex determination in reptiles - whole generations the same sex?

« on: 17/08/2012 23:32:27 »

But has anybody ever quantified this (looked at sex ratios per generation)?

I would think that these microclimates/microhabitats wouldn't have a large effect, because the animals have a very specific requirement for nesting sites.  Some aren't going to nest in the shade while others nest in the sun.  Furthermore, many reptiles will nest in burrows underground, where temperatures are remarkably stable. 

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Plant Sciences, Zoology & Evolution / Temp-dependent sex determination in reptiles - whole generations the same sex?

« on: 17/08/2012 17:40:06 »

If sex is determined by temperature in reptiles, wouldn't whole generations of a species be the same sex, at least at the local scale?  For example, lets imagine lizards living in a particular stretch of flat desert.  Presumably, this area will be experiencing the same temperatures, and the lizards will be choosing the same type of areas to lay their eggs.  Because these eggs are all incubating at the same temperature, wouldn't this entire generation be of the same sex?  This would seem to complicate the search for appropriate mates in the future, especially for short-lived species.

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Physiology & Medicine / Is the bony labyrinth of the inner ear really a separate bone?

« on: 17/08/2012 17:28:00 »

The bony labyrinth of the inner ear consists of the cochlea, vestibule, and semi-circular canals. It is important in hearing and equilibrium.  In anatomical models and diagrams, it is depicted as a hollow bone nestled inside the temporal bones of the skull.  But I'm wondering, is it really a bone nestled within another bone, or is the bony labyrinth actually just a hollowed-out chamber inside the temporal bone? Can someone with expertise shed some light on this?  Especially, someone with first hand experience from dissection.

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The Environment / Re: Why has CO2 increased in ancient atmospheres?

« on: 12/08/2012 07:20:19 »

thanks for your replies

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The Environment / Re: Why has CO2 increased in ancient atmospheres?

« on: 11/08/2012 17:53:06 »

But that seems to imply that temperature changes are driving changes in CO2.  Climate scientists are arguing the opposite, that changes in CO2 are driving change in temperature.  So CO2 levels are first to change, not temperature, right?

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The Environment / Why has CO2 increased in ancient atmospheres?

« on: 10/08/2012 22:10:20 »

Measurements from ice cores indicate that atmospheric CO2 levels have widely fluctuated in the past (going back 600,000 years, see http://climate.nasa.gov/evidence/).  What has caused these changes - especially the increases in CO2?  (keep in mind that I'm not talking about the current increase in CO2).

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Question of the Week / Re: QotW - 12.08.12 - Is making vitamin D akin to human photosynthesis?

« on: 10/08/2012 08:01:27 »

Photosynthesis is a special biochemical process that uses solar energy to create relatively complex and energy-rich sugar molecules from CO2, a simple and low-energy source of carbon.  Essentially, solar energy is stored in the chemical bonds of sugars.  Because of this, plants are able to make their own food.

The creation of vitamin D in humans is not similar to photosynthesis for two reasons.  First, we are not converting solar energy into chemical energy, and second, we are not using these molecules for food.   

In humans, vitamin D is created from a precursor molecule that is already present in our skin.  The sun's energy is used to slightly change this pre-existing precursor molecule into a form that is more usable to our cells.  Once modified by solar rays, this early form of vitamin D will be later modified in the kidneys before becoming functionally mature. 

UV light is especially important in this process.  Using sun block reduces the amount of UV reaching your skin cells, so it would reduce vitamin D production.  However, if you spend several hours in the sun, it is likely that enough UV radiation is penetrating this protective layer and enabling your body to make sufficient quantities of vitamin D.
-Matt F, Washington State