Samantha Wright's Journal: Biology Help Desk

Thanks to the power of my silly sig, I've been getting a lot of biology questions lately. Most of these are fun to answer, but occasionally they pop up in totally inappropriate threads just out of the blue. Since Slashdot supports commenting on journal posts, it seemed like the best thing to do would be to make one and encourage people to ask here instead. So do that!

And I really will phrase things as car and computer analogies when possible. Although computer analogies are way more common.

For clarification, I've taken physiology and genetics courses, and can answer most geeky things about the human body and fundamental biology. I don't know much about pharmacology or ecology (because it is very, very, dry), and I am not a doctor. But I'll try to answer those questions, too.

skin absorbtion

[tryptogryphic]

Hi, I have a question about substances being absorbed through the skin and metabolized by the liver. Are 'all' chems / substances placed on the skin absorbed eventually into the blood stream and processed by your liver, or are certain chems / molecules too big to do so. I'm primarily asking because my 3 year old son likes to spend a lot of time at the beach, and his mother (we are not together) has his homeschool teacher take him like 4 times a week; he wears sunblock every time, and I have concerns about

Re:

[Samantha Wright]

Not all chemicals pass through the skin. In order to do so, the chemical usually must be fat-soluble (like oil) and of a certain size, although very small molecules like water are absorbed deliberately.

There is fairly strong evidence that a small amount of the chemicals from sunscreen can be absorbed into the skin, however. Because UV light is so high-energy, a lot of these chemicals can break down and create free radicals, which have a high potential for damaging DNA and potentially causing cancer. Several

What's the evolutionary advantage of....

[Pseudonym Authority]

What's the evolutionary advantage of living in 3 dimensions rather than 4 or 2 or something?

Re:

[Samantha Wright]

This one isn't quite an evolutionary advantage, but it works well with certain other physical properties of our universe to help set up a working system. I can't answer your question very well directly, but if I had to wager, I'd say that having gravity be a cubic function is the main one. It influences the way in which stars and planets coalesce, and the cycle of stellar novae is necessary to create heavier elements such as carbon and the metals. I'm not much of an astrophysicist, but I'm pretty sure that