All Questions
29
votes
4answers
727 views
Can scientists create totally synthetic life?
This particular question has been of a great deal of interest to me, especially since it dives at the heart of abiogenesis.
29
votes
4answers
1k views
Life without DNA?
I'm by no means an expert in the field, merely a curious visitor, but I've been thinking about this and Google isn't of much help. Do we know of any lifeforms that don't have the conventional ...
15
votes
2answers
1k views
How do the brain and nerves create electrical pulses?
I have heard that information is sent between the brain and peripheral nerves via electrical pulses or signals, but I don't understand how they create them in the first place.
25
votes
3answers
921 views
Why is polyploidy lethal for some organisms while for others is not?
Polyploidy is the multiplication of number of chromosomal sets from 2n to 3n (triploidy), 4n (tetraploidy) and so on. It is quite common in plants, for example many crops like wheat or Brassica forms. ...
11
votes
4answers
385 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 ...
10
votes
1answer
107 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
3answers
156 views
Mathematical Modelling of Natural Selection
I'm a math undergrad looking for some papers on modelling the process of natural selection. The only paper I've been able to find is by the pre-eminent mathematician Herbert Wilf from 2010,
There's ...
19
votes
1answer
184 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 ...
16
votes
3answers
210 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.
16
votes
3answers
513 views
Are single-celled organisms capable of learning?
I've read that the amoeba is capable of learning. Since these protists have no nervous system, it's safe to assume that even highly simplified learning mechanisms of the Aplysia are miles off in the ...
13
votes
3answers
394 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 -- ...
4
votes
1answer
75 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 ...
23
votes
1answer
374 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 ...
17
votes
3answers
424 views
How many times did endosymbiosis occur?
According to the endosymbiont theory, mitochondria and chloroplasts originated as bacteria which were engulfed by larger cells. How many times is it estimated that this occurred in the past? Are there ...
14
votes
2answers
1k 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 ...
14
votes
2answers
643 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
309 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 ...
12
votes
3answers
104 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 ...
12
votes
2answers
1k 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
3answers
745 views
When has an organism evolved enough to be called a new species?
Imagine that we take a population of horses, split them in half and place them in completely different environments. The two species will evolve separate from each other and because the environment is ...
11
votes
1answer
332 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 ...
11
votes
10answers
475 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 ...
8
votes
2answers
903 views
Why are not all species hermaphrodites?
If a hermaphrodite animal (like slug, snail, etc) finds a partner they can mate immediately.
If another animal with "normal" reproduction (lets say a mouse) finds a partner they can only mate if they ...
8
votes
1answer
1k views
Effects of Polyphasic vs Monophasic sleep in humans
Why do humans practice monophasic sleep cycles?
When altering one's circadian rhythm to a Polyphasic sleep schedule, how much would that affect development?
Is Monophasic sleep (once per day) ...
6
votes
1answer
67 views
Do adjacent axons in a nerve influence each other?
Suppose I have a nerve fiber consisting of several axons all running in parallel to each other. When an action potential is generated in a certain axon, this will alter the concentration of sodium ...
5
votes
1answer
204 views
How do neurons form new connections in brain plasticity?
I've been reading about brain plasticity and how the brain can "rewire" itself.
One of the things that is not clear to me - how neurons can establish new connections. Does this rewiring mean that ...
17
votes
3answers
306 views
Good source that explains the evolution of single-celled organisms “from scratch”
Are there any books or sites that detail, step-by-step, the evolution of the first single-celled organisms (bacteria, archaea) from a Miller-Urey-like beginning? That is, assumes only amino acids, ...
16
votes
1answer
1k 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. ...
14
votes
2answers
247 views
Why Is Most Life Symmetrical Externally But Not Internally?
Mammals, reptiles, arachnids, insects, etc are all as far as I am aware symmetrical in appearance.
Take a human for instance, make a line from the top of our head right down the middle. However, ...
14
votes
1answer
180 views
What is the lowest pressure at which plants can survive?
What is the lowest pressure at which plants can survive? How the plants behave in a Martian-type atmosphere? Is there any plant that can survive such atmosphere?
Can a lichen grow at Martian ...
12
votes
1answer
514 views
Why do neurons die so quickly (relative to other cells) when deprived of oxygen?
This question could be considered a follow-up question to Why is a lack of oxygen fatal to cells?, although the top answer there does not address why damage starts to pop in.
The answer says this:
...
12
votes
2answers
319 views
How Do Galls Form?
I am curious how Gall Wasps, bacteria and other organisms induce galls to form.
Specifically, what chemicals induce gall formation?
12
votes
1answer
167 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 ...
12
votes
3answers
356 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.
11
votes
1answer
159 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 ...
10
votes
1answer
158 views
What elements are a possible basis for life?
I've been told that life on earth is carbon-based, Then I got curious about one thing: What are the possible bases for life and under which circumstances could lifr based on other elements exist?
If ...
10
votes
2answers
124 views
What can the timing of human urination tell about the human's physical condition and circadian rhythms?
I've noticed a peculiar phenomenon. A subject drinks 400 ml of water, then observes time until the urge to urinate is felt. The time is 15 minutes. The subject releases water. 14 minutes later another ...
10
votes
2answers
265 views
Could an “overactive” brain increase the chances of Alzheimer's Disease?
From Raichle ME. 2010. Two views of brain function. Trends in cognitive sciences 14: 180–90:
Alzheimer’s disease (AD) is the most common cause of progressive
cognitive decline and dementia in ...
10
votes
2answers
1k views
Why is a lack of oxygen fatal to cells?
In animals temporary anaerobic respiration leads to the breakdown of the pyruvate formed by glycolysis into lactate. The buildup of lactate in the bloodstream is accompanied by a large number of ...
10
votes
1answer
189 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 ...
9
votes
3answers
4k views
What is the difference between orthologs, paralogs and homologs?
These three terms are often misused in the literature. Many researchers seem to use them as synonymous. So, what is the definition of each of these terms and how do they differ from one another?
9
votes
4answers
760 views
Why can cones detect color but rods can't?
I don't know if this question applies to only humans but why can cones see much greater detail than rods? Is it possible to have a rod that can detect light intensity and color?
9
votes
3answers
1k 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 ...
8
votes
2answers
219 views
How much weight/volume do microbes occupy within the human body?
Microorganisms constitute the bulk of all the biomass on Earth. I weighed myself yesterday, and wondered how much less I would weigh if I were completely free of bacteria and microbes, inside and out. ...
8
votes
4answers
2k views
What is the armpit hair for?
Modern human beings, especially women, cut their armpit hair. It seems to me the armpit hair is trivial/useless. Shortly speaking, what is the armpit hair for?
8
votes
1answer
95 views
Why does the gender of the parent species determines the species of a hybrid offspring
I've read a little about hybrid animals, and have been amazed by the fact that the gender of the parent species determine the species of the offspring, in some hybrids.
A male horse and a female ...
8
votes
4answers
331 views
What is meant in biology by the term “evolved”?
A student asked me this the other day and I thought that I would ask it again here. If one organism is said to be "more evolved" than another, what exactly does this mean?
6
votes
3answers
137 views
Are there genes in humans from the common ancestor of all organisms?
How long ago can human genes be traced? Are there any genes that go back unchanged to the beginning of life on Earth? And if so, how many?
6
votes
2answers
990 views
Which shades/hues of color are easiest to distinguish for humans?
I'm trying to represent data graphically and am using a variation of hue/lightness to distinguish one data point from the next. I would like to use a color that would allow me to convey most ...
6
votes
2answers
153 views
Does becoming martyr have an evolutionary advantage?
This is related to
How does "be altruist to those who are similar to you" evolve?
Altruism that is
Not reciprocal
Not familiar
has little explanation. One possible explanation is that ...
