[Broca]

Ahhh another science adaptation question...critical curriculum in the 4th grade.
Penguins are able to slow the blood supply to their feet keeping the temperature of them above freezing. Their feet might be really cold, but they will not succumb to frost bite.

[bezoar]

But it would seem like slowing the blood supply to their feet would cool the feet, making them more susceptible to freezing.

[Donnah]

Don't they cover their feet with their pot bellies when they are not moving?  So I'm guessing their feet are kept thawed by movement and/or fat-belly cover.

[cuso4]

Now I got another theory.

May be cells of penguins feet are surrounded with networks of cappilaries and this enables oxygen to be transported to the cells in the feet. So that energy can be generated by respiration to keep their feet warm.

Angel

[bezoar]

Seems like this would have to do with some type of mechanism or anatomy that keeps both the venous and arterial blood above freezing.  And obviously, the venous blood would be the greater problem.

Bezoar

[Ians Daddy]

I'm going to stray a bit, because this is where I am. Does anyone know what happened to "Nilmot" / Tom / "The Riddler"? Haven't seen him in quite awhile.

[Qing]

quote:Originally posted by cuso4

Now I got another theory.

May be cells of penguins feet are surrounded with networks of cappilaries and this enables oxygen to be transported to the cells in the feet. So that energy can be generated by respiration to keep their feet warm.

Angel

I came up with this idea as well, but this might not be enough.i mean, penguins feet are in direct contact with freezing enviornment,and the tempearture is really low. so there might be other adaptations e.g. like Donnah said,"they cover their feet with their pot bellies when they are not moving". just a thought.

Qing

[NakedScientist (OP)]

ANSWER TO : WHY DON’T PENGUINS FEET FREEZE ?
Part of the reason is that penguins are birds and are warm blooded so they keep their feet from freezing by pumping warm blood from their body into them. But that’s only half the story because penguins live in such a cold environment that they would very quickly lose all of their body heat if they continuously pumped hot blood around their feet. Instead they have hit upon an ingenious solution which saves heat and keeps their feet just above freezing. In the penguin’s legs the arteries, which carry hot blood from the body, are wrapped around the veins bringing cold blood back from the feet. The cold blood in the veins removes most of the heat from the arteries, warming up as it does so, so that the blood entering the feet is just above freezing, but the blood in the veins, by the time it reaches the body, is back up to body temperature. So the penguins feet receive blood just warm enough to keep them from freezing, but are not so hot that the penguin melts into the ice.

[NakedScientist (OP)]

HERE'S THIS WEEK'S "QUESTION OF THE WEEK" :

"HOW, AND WHY, DO CHAMELEONS CHANGE COLOUR ?"

Fire away.

TNS

[Qing]

that's an interesting question. i know that chameleons change colour to protect themselves. their colour changes according to the environment. but how do they change it.

Qing

[Ians Daddy]

Surely it's chemical. Maybe it detects the light rays emmiting from a surface and can balance itself to that. It's probably automatic, the same way that I turn so red when embarrassed or angry. When frightened, they "balance" themselves with their surroundings. [?]

[Exodus]

I've always considered myself to have chameleon properties... If i drink too much i turn green too, what help that does i dont know, when your in that state you want to be found, not blend in with the grass! LOL

As for th answer, i don't really know, well i have an idea...

Resident Tour Operator - The Naked Scientists

[cuso4]

quote:Originally posted by NakedScientist

ANSWER TO : WHY DON’T PENGUINS FEET FREEZE ?
Part of the reason is that penguins are birds and are warm blooded so they keep their feet from freezing by pumping warm blood from their body into them. But that’s only half the story because penguins live in such a cold environment that they would very quickly lose all of their body heat if they continuously pumped hot blood around their feet. Instead they have hit upon an ingenious solution which saves heat and keeps their feet just above freezing. In the penguin’s legs the arteries, which carry hot blood from the body, are wrapped around the veins bringing cold blood back from the feet. The cold blood in the veins removes most of the heat from the arteries, warming up as it does so, so that the blood entering the feet is just above freezing, but the blood in the veins, by the time it reaches the body, is back up to body temperature. So the penguins feet receive blood just warm enough to keep them from freezing, but are not so hot that the penguin melts into the ice.

Just found out that human (and other mammals) keep their hands and feet from freezing the same way as penguins. Because we are all HOMEOTHERMS.

Angel

[cuso4]

quote:Originally posted by NakedScientist

HERE'S THIS WEEK'S "QUESTION OF THE WEEK" :

"HOW, AND WHY, DO CHAMELEONS CHANGE COLOUR ?"

Fire away.

TNS

Here's the answer. This is not purely my knowledge because I did a bit of research.

Under a chameleon¡¯s outer skin are special skin cells with colour (or pigment) in them. These cells are called chromatophores. The top layer of chromatophores have red or yellow pigment. The lower layers have blue or white pigment. A chameleon changes colour when its brain sends a message to the cells. The message tells the cells to grow bigger or to shrink. When this happens, the cell pigments mix and the chameleon¡¯s colour changes.

Temperature affects the chameleon¡¯s colour too¡ªif it¡¯s cold, darker skin allows the chameleon to absorb more heat from the Sun. And, light from the Sun can signal a chameleon to change to a lighter shade, to reflect the sunlight.

Angel

[NakedScientist (OP)]

ANSWER TO "HOW DO CHAMELEONS CHANGE COLOUR ?"


If you’re not sure what a chameleon is, it’s a kind of lizard that lives in trees, usually in Africa or Madagascar. Most people have heard of chameleons because of their amazing ability to change the colour of their entire body within seconds. But it’s a myth that  chameleons change their colour to blend in with their surroundings. In fact the main reason that they change colour is so that they can communicate with each other. For example a calm chameleon is a pale green colour, an angry chameleon turns bright yellow and a chameleon who spots another chameleon it would like to mate with usually displays an explosion of different colours including reds, greens, browns, whites and blues. So how do they actually change colour. The answer lies in special cells buried in their skin called chromatophores. These cells are all wired up to the chameleon’s brain and contain different coloured pigments. When the chameleon wants to change colour, signals from the brain tell the skin cells to release their coloured pigment which spreads out in the cell and changes its colour, rather like giving the cell a coat of paint. The chameleon can make a range of different colours by switching on different coloured pigment cells at the same time, a bit like mixing red and yellow paint together to make orange.

WELL DONE ANGEL - HIT THE NAIL ON THE HEAD !

[NakedScientist (OP)]

HERE IS THIS WEEK'S "QUESTION OF THE WEEK" :

"WHY DO PEOPLE HAVE DIFFERENT COLOURED SKINS ?"

Have a go, answer next week.

TNS

[Ians Daddy]

Different levels of melanin?

[cuso4]

Yes Ronnie, I believe so.

I think different levels of melanin are due to human's adaptation to the environment. The pigment melanin can absorb UV radiation to prevent the damage to skin cells.

For example, people live in Africa are constantly exposed to strong sunlight during day time, so their ancester had evolved (not sure it's the right word to use) to have a dark skin to suit the environment.

However, people live in places like UK or Canada where the weather is colder and experience less sunlight had not adapted for exposure to sunlight but for the reduction of heat lost. Although pale colour absorb less heat they also radiate less heat.

Finally, people live in Asia especially with sub-tropical weather are adapted for medium level of sun exposure. This accounts for their tan-ish coloured skin.

Angel

[Quantumcat]

darn it cuso4, that's my kind of question!![!] I was too late[] lol only kidding I'm not mad !![]

I can add a little bit.

When humans have little or no pigment, that is, albanism, it's because there is a mutation in the gene for tyrosinase which is an enzyme that changes tyrosine into melanin in the melanocytes.

People with darker skin have extra genes (I think, correct me if I'm wrong!!!) that increase tyrosinase production so more melanin is converted from tyrosine in the melanocytes, then let out and distributed around the skin...

When the skin is exposed to UV light, tyrosinase production is stepped up so more melanin is made. This is an emergency response designed to protect the skin from further damage from the UV light (because UV radiation can change genes, therefore cause cancer)

Tyrosinase is being made all the time, melanin isn't permanent and if you get a tan then stay is a dark room for a while you'll see that the tan wears off in a month or so.

When people get freckles it's because the melanocytes are spaced far from each other and aren't very efficent at delivering the melanin into the surrounding skin (also correct me of I'm wrong there not so sure)

Anyway I didn't copy and paste that, I wrote it from my own head ... probably why some of it is probably wrong ... lol

Am I dead? Am I alive? I'm both!

[cuso4]

Sorry Quantum [|)], but my bit is quite simple and can be worked out logically whereas your bit is....very scientific (good on you []!) and thanks for the extra info as I didn't know melanin was made from tyrosine.

And...I'm certain that the bit about freckles is correct. People who get tan because they got even distribution of melanocytes.

Angel