25
votes
1answer
3k views

What causes morning wood?

Sometimes men wake up with an erection in the morning. Why does this happen?
14
votes
3answers
504 views

What is the most difficult feature to explain evolutionarily? [closed]

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 -- ...
13
votes
4answers
2k views

Why is the Hydra Biologically Immortal?

I have heard that the Hydra organism is biologically immortal (later I found that there are more immortal organisms). Now I know that its immortality is related to its telomerase. The thing is that we ...
13
votes
1answer
716 views

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 ...
12
votes
9answers
7k views

Why have humans evolved much more quickly than other animals?

Humans have, in a relatively short amount of time, evolved from apes on the African plains to upright brainiacs with nukes, computers, and space travel. Meanwhile, a lion is still a lion and a ...
12
votes
10answers
820 views

A good book for history of biology/biotechnology for lay people

I have many friends who are interested in Biology and want to know more about the subject in general (like a history of biology, from Darwin's theory, to DNA structure discovery, to the human genome ...
10
votes
1answer
389 views

Supercomputer Vs Human Brain

With supercomputers doing calculation in petaflops ($10^{15}$ Calculations per Second), have we crossed the speed of Human Brain?
10
votes
1answer
148 views

Does stress physically age our body?

Going by the assumption that stress eventually triggers a flight/fight response, and the subsequent realization that flight/fight puts the body in a system of readiness to use it's available resources ...
7
votes
2answers
270 views

What does fitness really mean?

Fitness is certainly the most important concept in the theory of evolution. My question does not have to do with practical measures of fitness but with the theoretical definition of it. I am a bit ...
7
votes
1answer
218 views

On average how many genes / alleles do people share?

I am curious about how much more a child can be alike to one parent than the other. If a child were to inherit all the alleles that are shared between both parents from one parent, but inherit all ...
6
votes
2answers
103 views

How are Genetic Circuits Modelled?

I've read a recent Nature Methods paper by Moon T.S. et al, in which a synthetic genetic circuit consisting of layered logic gates was created. For example, the paper, a circuit is modelled in Figure ...
30
votes
2answers
1k views

How do cockroaches resist the effects of ionizing radiation?

Cockroaches are very hardy insects. It is known that, among other things, they are able to withstand bursts of ionizing radiation that would kill a human being. The explanations of this observed ...
28
votes
1answer
598 views

What is itching?

What exactly at the molecular level is itching? What physiological function does itching serve, if any? I cant remember the reference but a PLCb3 null mice lost the itch phenotype, so presumably it is ...
19
votes
1answer
245 views

Evolutionary origin and exogenous cues of ~28 day infradian rhythm?

The most obvious example of an approximately monthly biological cycle is the human menstrual cycle. My questions are the following: Is it known when and where this cycle or one like it arose? What ...
17
votes
1answer
2k views

What is the criticality of the ribosome binding site relative to the start codon in prokaryotic translation?

In prokaryotic translation, how critical for efficient translation is the location of the ribosome binding site, relative to the start codon? Ideally, it is supposed to be -7b away from the start. ...
16
votes
3answers
269 views

How is the blood volume of a living organism measured without killing it?

How is the blood-volume of an organism measured without killing it? NOTE: The blood-volume of an organism is defined as the total volume of blood present inside that organism.
15
votes
4answers
2k views

Why do the two hemispheres of the brain control the opposite sides of the body?

Why does the left hemisphere control the right and the right hemisphere control the left? I googled it but didn't find a good answer regarding this. Could someone explain? Does this adaptation help ...
14
votes
4answers
2k views

Height and natural selection in humans?

I watched the documentary "Evolve" recently and in the segment on "size" Scott V. Edwards, Harvard evolutionary biologist mentioned the idea that humans might evolve to be 7' tall in 'hundreds of ...
12
votes
3answers
149 views

How are long time periods measured in biological systems?

Biological systems are pretty good at measuring fairly long times, for example, menstrual cycles (month), or puberty (years). Counting days or years seems to be implausible, and chemical concentration ...
10
votes
1answer
165 views

What are the functions of magnetic bacteria?

I'm trying to understand why are bacteria "equipped" with magnetosomes and why/what for do they need such organelles.
9
votes
2answers
295 views

How does the genetic code evolve?

After looking at this question, some other questions poped in my mind. The DNA code is redundant, there are 20 amino acids for 64 possible nucleotide combinations. Therefore some amino acid are coded ...
9
votes
1answer
269 views

When does weak selection produce qualitatively different results from strong selection?

In evolutionary game theory, it is typical to model organisms as having a base fitness that is modified slightly by the game interaction. The ratio of the game effect versus the base fitness ...
8
votes
1answer
879 views

Disadvantages of unihemispheric sleep

Is is well known fact that marine mammals and some birds can sleep with one brain hemisphere at a time, since it's essential for their survival. However, at least in my opinion, such mechanism would ...
5
votes
1answer
78 views

Hill-Roberston effects and effective population size

From this article, first page, middle of the second column: Even if harmful alleles do not become fixed, they can still reduce the efficacy of selection on neighbouring loci through a process ...
5
votes
1answer
409 views

Smallest unit on which selection can act

Traditionally, the individual was considered to be the smallest unit on which Natural Selection (NS) acts. Today, we usually consider the gene as being the unit of NS. Of course, we should also ...
4
votes
1answer
136 views

How does “inheritance of methylation” of DNA and/or histones work?

What are the current models/ideas describing the mechanisms explaining inheritance of methylation on DNA resp. histone level? Is there evidance of this "setup" information being really ...
30
votes
4answers
644 views

How does the sensitive plant detect vibrations?

The sensitive plant (Mimosa pudica) is a remarkable little plant whose characteristic feature is its ability to droop its leaves when disturbed: Apparently, this ability to droop rests on the cells ...
25
votes
7answers
392 views

Has there been any observation of species adapting the evolution process?

I am very interested in the evolution of the evolution process itself. There are of course a lot of things that influence how evolution will work, but for this question, I am interested in things that ...
24
votes
3answers
7k views

Why do eukaryotic organisms have introns in their DNA?

We touched on introns and exons in my bio class, but unfortunately we didn't really talk about why Eukaryotes have introns. It would seem they would have to have some purpose since prokaryotes do not ...
20
votes
1answer
462 views

How, on a physical level, does ATP confer energy?

When ATP is used as the energy currency to make, say, reaction X + Y → Z happen, is what happens on a physical level down at the molecular scale that during the reaction ATP + H2O → ADP + Pi ...
18
votes
3answers
17k views

If the brain has no pain receptors, how come you can get a headache?

I've read many years ago in books, that the brain has no nerves on it, and if someone was touching your brain, you couldn't feel a thing. Just two days before now, I had a very bad migraine, due to a ...
15
votes
2answers
3k views

Why is glucose our primary source of energy?

Is there any evolutionary reason for glucose being the "main" molecule used as a source of energy, beginning with glycolysis and subsequently cellular respiration (after being converted to two ...
15
votes
3answers
397 views

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 ...
14
votes
2answers
821 views

Why is 'Grudger' an evolutionary stable strategy?

I am currently reading 'The Selfish Gene' by Richard Dawkins, which I am sure many here have read. The topic are evolutionary stable strategies (ESS) regarding cooperation. I apologise for the long ...
14
votes
2answers
1k views

How and where, in the human brain, are memories stored?

Background I am a computer programmer who is fascinated by artificial intelligence and artificial neural networks, and I am becoming more curious about how biological neural networks work. Context ...
14
votes
3answers
372 views

Are human fetuses more likely to be male?

Question: From a physiological point of view, when sex is determined in a human fetus, is it equally likely to be male or female? Studies in this area typically measure age at birth, where the data ...
14
votes
1answer
1k views

Why do some mammals not have testes in a scrotum?

Coming from an evolutionary approach, Is the only purpose of a scrotum to regulate the temperature of the testes? Knowing all mammals are warm blooded, shouldn't all mammals have testes in a ...
13
votes
1answer
189 views

What is the prehistory of amino acids in cells?

As a followup to Why 20 amino acids instead of 64? and What is the smallest number of amino acids required for life?, I am trying to understand the prehistory of amino acids in cells. All living ...
13
votes
3answers
658 views

How many human proteins have a solved 3D structure?

I was wondering how many human proteins have a solved 3D structure. Is there a database with only human proteins? I looked at pdb but couldn't find a filter.
12
votes
2answers
3k views

Do men have significant hormonal cycles?

I know there's a similar question here. But that discussion dissolved into lunar cycle and a correlation with it. I want to find more towards the original question of is there a periodic hormone ...
12
votes
2answers
1k views

How does a brain distinguish stimuli?

If all the brain ever "sees" is action potentials, how do we know that one set of action potentials denotes a flash of light, another one signifies a loud sound, etc ?
11
votes
1answer
426 views

How do CpG islands remain unmethylated?

In most of the genome CpG sites are pretty much always methylated, but CpG islands are instead often unmethylated. This has been linked to the fact that they often are associated to transcripted ...
10
votes
2answers
303 views

Why Do Most Humans & Cats Have Blue/Bluish Eyes At Birth?

I've read that the eye color at birth for most humans and for cats may not always be the the true genetic color at first. This is due to the lack of melanin in the iris. This makes sense as there is ...
9
votes
1answer
208 views

Did the eugenics program in Nazi Germany have a measurable effect? [closed]

Did the killing or sterilisation of people considered as living a "life unworthy of life" in Nazi Germany have any measurable effect on the "average health" of Germany? Is there any statistical ...
9
votes
1answer
376 views

What light intensity starts melatonin release in humans?

I'm interested in whether any studies have determined the intensity of light at eye level that starts melatonin release in humans. I know that: melatonin release is suppressed by blue light with ...
9
votes
2answers
127 views

What role does a protein's size have on protein-protein interactions?

Protein-protein interactions are when two or more proteins bind together, possibly for some important biological function. Recently, I'm starting to look more into proteins, and in particular, ...
9
votes
2answers
293 views

How is human biological clock modelled in modern science?

Im an engineer by education and i program a lot, so the question sounds weird to people from other disciplines. Im trying to better understand the human biological clock. Yet i do not really know ...
8
votes
1answer
125 views

Is it a limitation of the eyes, or the brain, that we can't see a moving bullet?

Are the photoreceptors in our eyes not fast enough to register the fast moving bullet, or is the brain not powerful enough to make sense of something happening that fast?
8
votes
2answers
137 views

Why is venom more common in fish and snakes than other vertebrates?

Reading this question, I wondered why is it that we associate vertebrate venoms so often with snakes and fish, and more rarely with lizards, amphibians, mammals, and birds (apparently never, in ...
8
votes
2answers
459 views

Do plant-animal cross races exist?

Plants and animals have the following distinct properties: Plants live from solar energy by photosynthesis, they use solar energy to make sugar and oxygen out of carbon dioxide, which gives them ...

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