All Questions

68
votes
8answers
14k views

Why do some bad traits evolve, and good ones don't?

If a trait would be advantageous to an organism then why hasn't it evolved yet? Conversely, if a trait is not advantageous or mildly disadvantageous, why does it exist? In other words why does ...
23
votes
4answers
3k views

Why is a heritability coefficient not an index of how “genetic” something is?

On his blog, Eric Turkheimer writes: [T]aken as a number, a unit of analysis, heritability coefficients are funny things to aggregate on such a massive level. What exactly are we supposed to ...
80
votes
5answers
24k views

How could humans have interbred with Neanderthals if we're a different species?

To be clear, I'm not doubting that homo sapiens and homo neanderthalensis did interbreed: of that much I'm convinced. Within the past few years I've seen an upcropping of pop-sci articles discussing ...
28
votes
4answers
5k views

Books on population or evolutionary genetics?

I have recently been involved in collaborations that require me to model the population genetics of eukaryotic populations. I fear I may either be "re-inventing the wheel" or making conceptual ...
46
votes
7answers
8k views

Why isn't a virus “alive”?

The recent news about a new supermassive virus being discovered got me thinking about how we define viruses as non-living organisms whilst they are bigger than bacteria, and much more complex than we ...
3
votes
2answers
640 views

Why do the ancestors of birds still exist? [closed]

If I am not mistaken, scientists believe that birds are evolved from reptiles. Why do the ancestors of birds (that is, reptiles) still exist?
56
votes
5answers
35k views

Why don't mammals have more than 4 limbs?

Arthropods have 6 or more limbs and arthropods with 6 limbs appear to move faster than arthropods with 8 limbs so I wonder whether this might have something to do with fast and efficient locomotion. ...
60
votes
8answers
10k views

Why does evolution not make our life longer?

Why does evolution not make life longer for humans or any other species? Wouldn't evolution favour a long life?
26
votes
7answers
5k views

What prevents predator overpopulation?

I've often heard that a population, human or otherwise, will continue to grow as long as there is food available (assuming nothing else is killing them off). It makes sense: if you have food you can ...
21
votes
2answers
2k views

If dinosaurs could have feathers, would they still be reptiles?

I just finished watching a video where it was mentioned that nowadays birds are dinosaurs and non-avians dinosaurs could have feathers. I confirmed this from wikipedia: Birds are highly advanced ...
35
votes
7answers
12k views

Is evolution a fact? [closed]

Richard Dawkins in one of his videos says that Evolution is a fact and not just a theory. He goes on to say that man and chimpanzees both evolve from apes. Is this correct (Is evolution a fact and ...
19
votes
2answers
4k views

Do males of all sexual species have Y chromosomes?

I know for instance some cells are sexual, so, this got me wondering, do the males of all species that have distinct sexes have Y chromosomes?
7
votes
2answers
2k views

Why is the strength of genetic drift inversely proportional to the population size?

I saw a concept on the Internet that says "the strength of genetic drift is inversely proportional to the population size". I don't know why they are inversely proportional? Can somebody explain? ...
16
votes
2answers
10k views

Solving Hardy Weinberg problems

I really fail to understand Hardy-Weinberg equilibrium and can't find an easy enough source of information. Can you help me to understand Hardy-Weinberg equilibrium? My goal is to be able to solve ...
36
votes
1answer
7k views

Does it make sense to classify all humans in a single species?

For what biological reasons do we consider that all human beings belong to the same species? A Thai and a Nigerian share a common ancestor that is 140,000 years old (see Gravel et al. 2010 and this ...
33
votes
1answer
5k views

Insect identification - Is this a bedbug?

This bug was found on a couch in Cape Girardeau, Missouri. The couch, and the two beds in the room show no signs of other bugs. Is this a bed bug that I should worry about or something harmless? It ...
36
votes
5answers
46k views

Do humans have enough biological differences to be grouped into races or subspecies?

After my online research on the subject, I learnt that, biologically speaking, many scientists believe that there is no such thing as a race. Homo sapiens as a species is only 200,000 years old, which ...
41
votes
5answers
6k 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, ...
35
votes
3answers
13k views

Why do parasites sometimes kill their hosts?

It's bothered me for a while now. I understand why a parasitoid would do this, as it only temporarily requires the host, and that not all parasites kill their hosts. There seems to be no evolutionary ...
25
votes
6answers
2k views

How is evolution possible in contemporary humans?

I would like to know if evolution is continuing to happen in modern humans, assuming things like existence of the nuclear family structure, fidelity to one partner, etc. It seems to me the answer ...
103
votes
8answers
18k views

Why do plants have green leaves and not red?

I know plants are green due to chlorophyll. Surely it would be more beneficial for plants to be red than green as by being green they reflect green light and do not absorb it even though green light ...
25
votes
3answers
24k views

Why is saltatory conduction in myelinated axons faster than continuous conduction in unmyelinated axons?

How does spacing apart sodium and potassium channels allow the action potential to travel faster down the axon? This is the reason always cited for saltatory conduction and myelination, but my mental ...
30
votes
7answers
3k views

How can homosexuality evolve despite natural selection?

I would imagine that the answer to this question would be population control, especially since even if one sibling is homosexual this does not necessarily mean that the other siblings will be too.
15
votes
2answers
11k views

Genetic linkage greater than 50 centimorgans

Classically, the linkage between two loci can be measured in centimorgans (cM), which represents the percent chance that these two loci will recombine an odd number of times (generating a recombinant ...
19
votes
6answers
5k views

Why are some genes dominant over others? What is the mechanism behind it?

If I have a brown eye gene which encodes the protein that is responsible for the brown color and have a blue eye gene as well, what is the reason that my eye color is brown? How does one gene maintain ...
8
votes
2answers
530 views

Human Evolution in Modern Times

I understand that evolution occurred to form the current hominids from a common ancestor millions of years ago. As evolutionary processes take a long time, is there proof of evolution occurring with ...
6
votes
2answers
1k views

The best free and most up to date phylogenetic tree on the internet?

I found phylogenetic tree in wikipedia is lacks of accuracy. It actually confusing with versions. Some terms was not scientifically accurate with dna analysis anymore So are there anyone know where ...
20
votes
2answers
975 views

Have we ever observed two drosophila lineages that evolved reproductive isolation in labs?

Background The standard definition of species refers to the concept of reproductive isolation. If two lineages are found to be reproductively isolated, then we consider these two lineages to belong ...
18
votes
2answers
867 views

Transitivity of Species Definitions

There are many definitions of "species" which usually take the form Two individuals are of the same species if ... An implied (rarely made explicit) property of any sensible species definition is ...
7
votes
3answers
3k views

Books for beginners [closed]

I want to study biology. I have zero previous knowledge of biology but I know Physics, Chemistry and Maths. From which book should I start? I have heard about Campbell Biology, but it is very costly ...
7
votes
1answer
269 views

Evolution of dominance of alleles

Can someone tell me where can I find detailed text about mechanisms of evolution of dominance? Or, if it is possible, I would be grateful if someone will tell me about them here.
23
votes
5answers
21k views

Why does hair grow after trimming but remains at a constant length after a while?

Some hair especially body hair regrows after trimming but stops growing after a while. What is the mechanism behind control of hair growth and how is the length limit determined?
34
votes
2answers
3k views

Why is menstruation in wild animals not a disadvantage to organismal survival?

When I watch wilderness specials for more than a few minutes, I notice a familiar pattern: predators are depicted as being alerted by the scent of blood. Wounded animals seem to make the best prey and ...
29
votes
7answers
5k views

Human evolution: Where *exactly* did the first human come from, whose parents were not?

Layman here. So I have never really quite understood this facet of human evolution, (or any other for that matter), in that, I understand the evolutionary process, but I get lost on the 'border' cases....
16
votes
2answers
1k views

Why do we have more male infants born?

For every 104 male babies, we have 100 female babies and there are statistics which are more reliable. (Those tell us that we have 997 female infants born per 1000 male infants born.) What is the ...
4
votes
1answer
1k views

How does temperature influence the rate of protein degradation?

For computer modeling purposes, I am looking for some referenced quantitative measurements of the effect(s) of temperature on biochemical reactions. Question In particular, my question is: How does ...
6
votes
2answers
1k views

Are mutations random?

The following claim Mutations are random or just the use of the expression Random mutations are very common among lay people. The claim is very common among lay people. The claim is often ...
5
votes
1answer
567 views

Why is it possible to calculate the equilibrium potential of an ion using the Nernst equation from empirical measurements in the cell at rest?

In trying to understand the Nernst and GHK equations, I've hit upon a snag somewhere deep in my understanding of the subject matter. Scenario 1: when calculating the membrane potential of a living ...
6
votes
1answer
2k views

Identify this smooth-cocoon worm from Southern India

I couldn't identify which species these worms belong to. I believe they're insect larvae. They measure approximately 5 to 10 mm in length, and are common in the southern states of India. They carry ...
24
votes
3answers
9k 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 ...
32
votes
4answers
4k 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 &...
11
votes
2answers
818 views

What insect is this? (India)

Can anyone tell me what kind of insect (if it is one) is this...!! Or is it the pupa of some insect? Well I don't think that the whole big thing is the insect itself, it appears to be just a kind of ...
10
votes
2answers
863 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 ...
14
votes
2answers
524 views

Seeing strange things in light

I have noticed that if you look directly at tubelight (I have only white ones in my home) and close your eyes little, you see little random shaped colourless things sometimes with slow speed and ...
13
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 ...
6
votes
1answer
483 views

Identification of an insect from midwest US

I have been seeing them more and more frequently indoors. I am currently in the Midwest United States, weather has been unusually warm for December, and there are many trees nearby. Can someone ...
4
votes
1answer
870 views

Assumptions of Hardy-Weinberg rule

The post Solving Hardy Weinberg problems offers an easy explanation of Hardy-Weinberg rule. The current top answer explicitly does not talk about the assumptions of Hardy-Weinberg. A model makes sense ...
145
votes
2answers
6k views

How many times did terrestrial life emerge from the ocean?

Evolution is often mistakenly depicted as linear in popular culture. One main feature of this depiction in popular culture, but even in science popularisation, is that some ocean-dwelling animal sheds ...
46
votes
4answers
11k 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. ...
17
votes
4answers
10k views

How do trees lift water higher than 10 meters?

The atmosphere pressure is 10 meters of water (approx). This means that it is impossible to lift water higher than 10 meters with vacuum or сapillary action (on Earth, under normal conditions). There ...

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