Tag Info

New answers tagged

1

As you say yourself, biological molecules are usually available in both chiralic possibilities, yet nature uses only one of the two possibilities. At some point in our molecular evolution (and at a very early one) L-amino acids were stochastically "chosen" over their D-equivalents (I think that the choices would have been equiprobable). There is no reason ...


-1

I saw a program recently that said that foods that have a close to 50/50 ratio of fat to sugar are much more appealing than mostly sugar or mostly fat. It is very hard to find this ratio in nature but when people started cooking (i.e. mixing different foods together) it was discovered that this combination was "tastier" or more desirable. This is why ...


3

This is a common misunderstanding from newcomers in evolutionary biology. Not every trait is the result of an adaptation. Evolution is way more than just natural selection and is not as deterministic as you may think. There is stochasticity inherent to mutational processes and there is stochasticity in reproductive success (called genetic drift). This ...


0

Sure. When the Europeans settled the Americas, 90%+ of the native American inhabitants were wiped out due to diseases like smallpox that the Europeans clearly had developed resistance to. Clearly, the surviving native americans had resistance, and the Europeans had gone through some similar event previously in history. The bubonic plague that was the ...


0

I am just summarizing ddiez's answer with a small addition. Robustness is the ability of the system to maintain its steady state or at the very least qualitative nature of the steady state with minor changes in the parameters of the system. This is different from stability which actually means the ability of the system to return to its steady state when ...


3

I think robustness and plasticity are different concepts, although related to each other. I would define plasticity as the property of a system to adapt to external changes. As defined in the wikipedia page for phenotypic plasticity: Phenotypic plasticity is the ability of an organism to change its phenotype in response to changes in the environment. ...


1

I think that the claim "different drugs properties come from different part of the world" is an illusion due to statistical mis-considerations. More accurately, there are 3 statistical issues here. Your sample size is too small to draw any conclusion. You only have 3 observations in one group and 2 in the other group. Your observations are not ...


2

Modern humans are continuing to evolve. Let me give you an example. Before cattle were domesticated over 99% of all adults were lactose-INtolerant (i.e., they did not produce the enzyme needed to break down lactose (lactase) and could not digest it, i.e. got diarrhoea if they drank milk). All infants produce this enzyme, but in lactose-intolerant people the ...


1

While its possible humans could speciate into two distinct groups at some point in the future, it hasn't happened recently (100 kya) and it doesn't seem to be happening now. If it were happening we would see two or more distinct populations that didn't interbreed and over time accumulated increasing differences. These skin colors track most of the evolution ...


4

Recap of the question: Looking at a single locus trait ($A$) controlled by two alleles, $A_1$ and $A_2$, the phenotypic mean is only affected by inbreeding depression, $f$ (Wright's inbreeding coefficient), if there is some degree of dominance, $d$. Why? Answer: If we take inbreeding as a higher than expected frequency of homozygotes, such that if the ...


4

Not all cat predatory behavior is innate. Researchers found that cats predatory behavior for birds vs. mice depends to a significant degree on training by the mother: if the mother taught predatory behavior with birds, the kittens grew up to be better at catching birds than at catching mice and vice versa. Supportive data shows that aside from monkeys and ...


5

As part of your question, you ask if other animals can create sound without continuous airflow. Many insects (e.g. cicadas and moths) do exactly this by using tymbals. A tymbal/timbal is an external membrane organ that is controlled by muscles or wing movements, that cause the membrane to flip back and forth, creating clicks or other sounds. So in many ways ...


3

Tracing it backwards this was the earliest reference I found via google scholar, it's from 1988 and uses the $r B C$ notation in the format we are used to. Hamilton's rule states that for a social action to be favored under natural selection, rb - c > 0, where c is the cost to the actor in terms of the effect on (usually a reduction in) his expected ...


4

Here is a list of woodwind instruments. Do you know of any (non-open) reed instrument that produces a note without anyone blowing air through them? Imagine a clarinet being played on someone's lap pouring out a melody. That would be very, very remarkable indeed. Our ability to produce sound from our throats is in theory like a reed instrument in music. ...


3

The time before Darwinism, people believed life as an entity which is created rather evolved. But there were great biologists interested in the relationship between species, who deliberately thought of evolution ideas and some of them believed in ape-human similarities and placed humans and apes in same group. In 1699, Edward Tyson, an English anatomist, ...


5

First of all, here is a program which simulates the evolution of the G-matrix over multiple generations, it's a few years old (they seem to have stopped developing it) and I've only played with it briefly. This could solve how to model the evolution of the G-matrix. Fisher's fundamental theorem is a great place to start off with the theory of this: The ...


2

This post is very related to your question and is definitely worth reading. I hope your teacher didn't really say that! It is really not as easy as he's suggesting. There are a number of studies that address the question on whether Sexual Selection (SS) and Natural Selection (NS) have opposite or antagonist effects. The subject is not easy and as SS is not ...


3

I am presenting a speculative approach since nobody has mentioned about any existent models yet. Assuming that selection is based on performance in certain tasks; performance is a function of traits which in-turn is a function of genotype. Performance is a non-linear function of genotype and selection imposes a cutoff/bandpass filter on the performance ...


2

Cooked food is a learnt trait rather than an evolutionary one. On a certain psychological level its a society norm so you would be hard pressed to find an individual who wouldn't mind eating completely raw meat/steak. But, say if you chuck a few humans into the wilderness at an early age and not teach them how to cook meat they may not actually cook their ...


2

Could not fit in a comment.. Welcome to Biology.SE! Here are a bunch of comments. The sentence until it evolves into a new species and / or the old ones become extinct sounds weird and there seems to be some confusion between evolution and speciation. Also it seems that you have a very static view of what is a species, as if species were predetermined ...


3

A mutation is a change in the genetic code - this can either be in the DNA or for viruses also in the RNA which carries their genetic information. This can either happen due to external influences (chemicals, radiation) or internal (mistakes while copying the information) reasons. See the figure below which shows the principle: DNA based lifeforms usually ...


-1

I can't check the sources, but I think they must estimate the relative energy of a threshold-sensitivity signal. I don't think the energy of a sound wave can be assigned an arbitrary value the way a photon can...certainly only a photon can propagate in a vacuum... Both light and sound waves scatter less, as they propagate, if they're higher ...


2

Pigmentation in most animals which is between black, brown, red, yellow and which is made up by the mixture of two pigments: Eumelanin (yellow to red) and Pheomelanin (black to brown). The ratio between these two makes a color. These are pigmental colors which are made by a special kind of cells in the skin, in mammals they are called melanocytes (and I will ...


1

Cloning of animals typically involves: Taking nucleus from healthy adult cell of animal to clone Taking a healthy egg and replace the egg's nucleus with nucleus from source animal. Implanting egg in female, stimulating the pregnancy process. This same process should work on humans BUT: "Is it really possible to create humans in lab?" No. Animal cloning ...


2

There was a paper that attempted to assess this published in 2010 There’s plenty of time for evolution - Herbert S. Wilf and Warren J. Ewens There is also a layman's explanation of this here Basically when we account for the fact that genes evolve in parallel under a number of simultaneous trials, it appears that there is indeed enough time for species to ...


1

I think there is some misunderstanding there, natural selection does act on an individual and can be determined by its genes (assuming there is genetic variance underlying the variance in trait). Those with more favourable genes will have more favourable phenotypes and thus be more likely to survive/reproduce. However, (genetic) evolution does not occur ...


2

I think you have misunderstood the passage. Here is a larger section (found at google books): Natural selection can also occur at the level of species, for certain characteristics enhance the rate of origin of new species or diminish the likelihood of species extinction. For instance, the number of species in lineages of herbivorous insects has generally ...


1

I assume that the figure comes from a section on genetic drift (since this seems likely), and it shows how the allele frequency will change over time under drift in a diploid population. So in short, each line represents the distribution of allele frequencies in different hypothetical populations, that all started with the allele frequencey p=0.5. As for ...


0

This is not a proper answer. Bear with me. I'm in a hurry; will edit the answer to a decent form when I find time. From the abstract of this paper: Of the 80% of oxygen consumption coupled to ATP synthesis, approximately 25-30% is used by protein synthesis, 19-28% by the Na+-K+-ATPase, 4-8% by the Ca2+-ATPase, 2-8% by the actinomyosin ATPase, ...


5

If you with 'humans' refer to our genus Homo (which is often the case), we do have multiple species, see wikipedia for an overview. The difference to many other organism groups is just that all species except Homo sapiens are extinct. Also, taxonomic ranks below the species level - such as breed, subspecies, population and race - are very poorly definined ...


0

Humans are a species and within our species we, arguably, have races. Although the term 'race' is highly controversial and ill-defined, as pointed out by @fileunderwater in his elegant answer, I just want to express that races can be, in a way, compared to breeds and hence that the human species does have some of the species-subdivisions you are addressing. ...


0

If you have the budget for it, I highly recommend Geneious for topology work. It was a real saver for me on an epi paper last year. Anyway, they allow for testing per-log likelihood without adjusting edge length. If you want to throw up some dummy data somewhere I can throw up an example. I have no connection or stake with the company, just happy with ...


1

Fruit being eaten is a very useful attribute for a plant, just like pollenisation through provision of nectar is often better than wind dispersal. Seeds contain startch and sugar, so seeds are always attractive to animals, so plants with fruit actually dissuade animals from eating the seeds, and encourage the fruit to be eaten in such a way as to be ...


0

From the statistical point of view, this question is rather vague. One would need a mathematical definition for the term "genetic variance". In one extreme, if the "genetic variance" merely means the categorial variations of nucleotides (i.e. ACTG) in the pooled genomes of interest, then the distribution of total "genetic variance" vs. loci variation is ...


2

There are plenty of animals with brief procreative periods, as you suggest. In chimps, sex takes 10 to 15 seconds - much less time than humans. So the question is really why have humans evolved to be different? I don't think any of the answers based on fitness are particularly compelling. It's not like sex feels like running a marathon or less physically ...


1

I can think of an example for the 3rd picture in your image "Common Agent With Multiple Symbiotic Relationships." We have: 1.) a species of parasitoid wasp 2.) a species of plant and 3.) a species of moth. The moth provides pollination activity for the plant. The plant provides a place for the moth to lay its eggs, and a food source for caterpillars once ...



Top 50 recent answers are included