16
votes
3answers
943 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
1answer
1k 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 ...
24
votes
4answers
12k views

Is there any advantage to one blood type over another?

All humans can be grouped into ABO and Rh+/- blood groups (at a minimum). Is there any advantage at all to one group or the other? This article hints that there are some pathogens that display a ...
4
votes
1answer
1k views

Why are men stronger than women?

What are the evolutionary explanations for why women are weaker than men (on average), and is this difference adaptive? See figure one here. I suppose that something puts pressure on men to be ...
30
votes
5answers
1k views

Why do men have nipples?

I'd be tempted to call nipples in men vestigial, but that suggests they have no modern function. They do have a function, of course, but only in women. So why do men (and all male mammals) have them? ...
29
votes
4answers
69k views

What's the maximum and minimum temperature a human can survive?

This is a question that has been in my mind since I was a kid. I'm not a doctor, nor even a biology student, just a curious person. What is the minimum and maximum temperature a human body can stand ...
21
votes
4answers
779 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 ...
19
votes
3answers
406 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, ...
18
votes
5answers
5k 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 ...
16
votes
5answers
809 views

Pipetting damage on cells

I'm curious how much damage is potentially inflicted by shear stress by pipetting. I know that with syringes for stem cell injection cause a lot of damage. However, to what extend does this happen ...
15
votes
4answers
3k 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 ...
13
votes
3answers
3k 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 ...
12
votes
4answers
2k views

If body temperature is 37°C (98.6°F), why are most people more comfortable at around 21°C (70°F)?

It may be different for other people, but for me, anything above 32°C (90°F) is very uncomfortable, and my body is inclined to seek cooler temperatures. But I would think that at 32°C, the body would ...
11
votes
3answers
538 views

What does irregular heartbeat mean in simple language?

I bought a blood pressure monitor (A&D UA-851) which has the option to measure irregular heartbeat. I do understand what 'irregular' means, but why do irregular heartbeats happen and what are ...
10
votes
3answers
8k views

Do apes and humans share 99% of DNA or 99% of genes? What is the difference?

I made an answer on the Scifi.SE that can be read here. It is about how the characters in the story Jurassic Park might have gotten DNA for all the species shown. In my answer, I said this: Apes ...
8
votes
1answer
1k views

Can you consider a human as alive, or is it the cells on the body that are alive?

Sorry if this question seems strange, but in the recent time I have been interested in the question of what life is and how you can define life. My question: How long can individual cells live on a ...
7
votes
2answers
143 views

How does Natural Selection shape Genetic Variation?

Background Importance of the additive genetic variance As stated here, the fundamental theorem of Natural Selection (NS) by Fisher says: The rate of increase in the mean fitness of any organism ...
15
votes
3answers
589 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 ...
12
votes
2answers
31k views

How many human cells are there in our body, on average?

How many human cells are there in our body, on average? Wikipedia says 1013: Bacterial cells are much smaller than human cells, and there are at least ten times as many bacteria as human cells in ...
12
votes
1answer
2k views

Why does hair turn grey or white, and why does it happen later for some?

The question is pretty simple: what is happening molecularly when hair turns grey or white? I would imagine that it is due to the lack of a particular compound. I'm also interested in why some ...
11
votes
5answers
595 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?
8
votes
1answer
193 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
1answer
934 views

Does extracted DNA degrade after a certain time period?

For direct use as template in PCR runs. Chelex 100 5-10% w/v extraction. Without listing the whole protocol, in the end the supernate is decanted off and then stored at 4°C. I was under the impression ...
6
votes
2answers
123 views

Why is there no way to remove an immune response?

We've known for a long time now how to "add a new entry to the database," as it were, of immune responses. It's called vaccination, and it's been one of the greatest success stories in the history of ...
6
votes
2answers
1k views

Why do DNA and RNA have the functions they have?

I know that there are two most important directions of genetic information transfer in living organisms: DNA->DNA and DNA->RNA. The first is replication, and the second is transcription. I wonder if ...
4
votes
1answer
421 views

Is there any size limit to the amount of information a human (or other) brain can hold

Im not sure how this would ever be tested but is there a limit to how much the brain can 'hold' before it reaches capacity ? I guess this could also be interpreted in terms of memory, as how well ...
4
votes
3answers
970 views

Chromosome 2 fusion?

I read this article by Jeffrey Tomkins and Jerry Bergman claiming to debunk chromosome 2 fusion. Is there anything wrong with these conclusions? " 1.The reputed fusion site is located in a ...
3
votes
1answer
110 views

Elevated position effect on recovery times from upper respiratory infections at rest?

In nursing school, they advice for people with upper respiratory infections to be in a slightly elevated position at the head region when sleeping. My intuition of the reason is that the lymphatic ...
3
votes
1answer
219 views

Ventral stream pathway and architecture proposed by Poggio's group

Please can you give me a very brief explanation about all functions in the ventral stream architecture summarized in this figure: This figure is from Serre et al.'s A quantitative theory of ...
3
votes
2answers
625 views

What are gram negative and positive bacteria?

I've just finished a course of double antibiotics for Helicobacter pylori in my stomach. I looked up H. pylori and found that it was a gram-negative bacterium. I looked up gram-negative and didn't ...
19
votes
2answers
723 views

Why is rabies incurable?

I'm still not sure about the mechanics that lead to rabies being incurable. I know that it can be treated before any symptoms show up, but why is it that once symptoms show the person is a dead man ...
17
votes
1answer
221 views

Are there dextral/sinistral higher animals?

For example, almost every dog I've met in my life (more than 20 subjects) uses their right paw touching one while asking for attention. Can it be used as a criterion for calling them dextral? If not, ...
16
votes
2answers
386 views

Why would diffusion be faster across a non-specialised tissue?

The standard protocol for a person experiencing chest pains is to chew a 300mg aspirin tablet, the argument being that chewing rather than swallowing the tablet results in the aspirin entering the ...
14
votes
2answers
3k views

How many organisms have ever lived on Earth?

I've looked for some information on this, but couldn't find anything useful. Has there been any noteworthy attempt to estimate the sum amount of individuals of all species that have ever lived on ...
14
votes
4answers
2k views

Can two humans with 44 chromosomes produce viable offspring?

It is known that there are very few individuals having 44 chromosomes, not the usual 46 chromosomes. One example is a male in China: the first article, the second article. The other is a female in ...
14
votes
2answers
799 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?
13
votes
2answers
589 views

Are there neurons that can sense light shining in your ears?

I know someone who bought earphones that shine light in you ears. According to what he was told, there are neurons that sense light and then make you feel wide awake when activated, which seemed like ...
11
votes
1answer
214 views

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 ...
11
votes
2answers
217 views

Under what conditions do dendritic spines form?

I'm looking for resources or any information about the formation of dendritic spines and synaptogenesis, especially in relation to how new connections are formed on a daily basis. Does the ...
10
votes
2answers
624 views

Do insects with compound eyes have depth perception?

Do insects with compound eyes have depth perception? They fly as if they do, but their eyes are so close together it seems like the image would be 2 dimensional.
9
votes
3answers
2k views

Does a man contain all the genes needed to make a woman?

This question is brought on by a Sci Fi novel I am thinking about writing. The plot device involves a colonist in charge of building a population on a new planet who loses his supply of embryos and so ...
9
votes
3answers
219 views

What causes feeling of feet falling asleep to be delayed?

This answer explains the sensation of extremities "falling asleep" as a result of sustained pressure on a nerve. The answer links to an external web page that says that the feeling "quickly goes away ...
9
votes
2answers
876 views

Do identical twins have the same fingerprint?

When there is every thing same from their genes to their phenotype so then why they don't have same fingerprints?
8
votes
3answers
365 views

Long-term-potentiation and memory. Where do we stand?

I was reading the answers to the question: How and where, in the human brain, are memories stored? and, as expected, LTP and LTD came out. Every time I read about LTP/LTD there is always something ...
7
votes
2answers
182 views

Why do we have more male infant born?

For every 104 male babies,we have 100 female babies and there is a Statistics which is more reliable (we have 997 female infant born per 1000 male infant born). what's the reason? why do we have male ...
7
votes
1answer
4k views

Why is ATP the preferred choice for energy carriers?

Why is ATP the most prevalent form of chemical energy storage and utilization in most cells?
7
votes
4answers
479 views

Suitable introductory book on Bioinformatics for a computer scientist?

Do you have any suggestions on a suitable introductory text on bioinformatics for a computer scientist? Any recommendations with pros and cons of different books would be appreciated. I'm mainly ...
6
votes
3answers
1k views

Why does replication require primers while transcription does not?

In transcription, there is no need for any primer. I guess the basic mechanism of DNA polymerase & RNA polymerase is the same. So why does replication have the need for a primer?
6
votes
1answer
180 views

What exactly makes bananas go brown?

I know that often oxidation processes are mentioned when referring to the color change from yellow to brown in bananas (specifically: those that you get everywhere in supermarkets, with no seeds). ...
6
votes
3answers
736 views

Is there any kind of immortality in plants?

I asked a question about immortality of hydra and learned good things about senescence. Now I would like to know about immortality in plants, if there is some kind of immortality in plants and how ...

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