Biology Stack Exchange
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1500 questions
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4 answers

Why can't the human eye focus blue light?

I recently noticed that it is hard to focus on blue light sources, especially at night. When observing a blue light source, e.g. a neon sign, it looks somewhat blurry. A sign with a different colour right beside it looks sharp. I already know about…
max0r
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What is the most difficult feature to explain evolutionarily?

I wonder what are examples of organs/structures/behaviours/cooperation that evolutionary biologists themselves find most difficult to explain -- to explain how they could appear evolutionarily -- within known mutation rates, generation frequency,…
Andrei
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How Do White Blood Cells Learn? Or Do They?

So I get the concept that a vaccine is a weakened form of a virus so that the body can "learn" to fight it and make a person immune to that disease, but how exactly does this learning take place? What learns? The white blood cells? Do they have…
CodeMonkey
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3 answers

Are there cats with black skin?

Some mammals can have a black, pink or spotted skin, depending on race - see for example humans or pigs. But I recently learned that this is not the case with mice. Even black furred mice have pink skin, and there is a rare mutation which produces…
rumtscho
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How does evolution produce complex organs

I've been wondering lately how evolution manages to produce complex organs. It is pretty obvious to me how evolution would select some minor traits like size, resistnce to illness or climate. There is a mutation where some organisms are slightly…
Stilgar
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Are human bodies programmed to die?

Following from this question: What is the evolutionary advantage of death?: Is there any evidence that human bodies have systemic self-destruction built into their developmental program? I'm not talking about the cell death response, which I know is…
Dave Gerrard
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1 answer

What is the most condensed form of (stored) energy used in biology?

When considering how organisms store energy for later use, I was wondering what substance known in Biology is best for compacting the most energy in the smallest space(volume-wise). With my (limited) knowledge, I would guess that it would be what we…
DoubleDouble
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How many people's DNA were involved in the compilation of the reference human genome?

I know that the reference human genome is complied from DNA portions from different people, most of whom were European. Do you know how many of them were involved? Do you know which ones were involved? Perhaps scientists like James Watson and George…
Gergana Vandova
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Why does sex last so long?

I wonder why (especially human) sex lasts longer than just a few seconds? My thought is that the shorter it takes a man to ejaculate, the lesser is the risk that he gets interrupted by a rival or a predator. Therefore, men who ejaculate quickly get…
MaxD
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How fast can a human run?

I'm a runner (cross country) and I'm always amazed at how fast Olympic sprinters are. There's a lot of hype about those in the 100-meter dash being the fastest in the world, and we're constantly seeing the 100-meter time dropping. But is there a…
HDE 226868
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Do gene expression levels necessarily correspond to levels of protein activation?

I have seen a lot of research into molecular mechanisms of diseases/phenotypes use measures of RNA as a 'proxy' for the level of protein available in the cell. Is this actually valid? My problem with the assumption that RNA levels correlate with…
Luke
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How did the human brain evolve?

A common question posed is, "how did the eye evolve?", because the eye is so complex. However, this has been answered rather clearly and there are several examples around the world of animals in which the eye has evolved independently. The human…
Jez
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3 answers

Why do some trees have a life span, while some don't?

I have heard that there is no limit on the growth of trees, but then why do some trees, such as boxelders and poplars, tend to live shorter than redwoods, for example? Some advertisements for improved lombardy poplars state that their trees have an…
J. Musser
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Is there any relationship between heartbeat rate and life span of an animal?

Is there any relationship between heartbeat rate and life span of an animal? Do they belong to a cause-and-effect relationship or are they both caused by some phenomenons or a common cause?
hello all
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What kind of skull is this?

We found this skull on a beach in southwestern Sweden, and are curious as to what kind of animal it was.
Eirik Jensen
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