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-2

It can't be explained by evolution, at least not very well. There is zero evolutionary advantage for an organism to have half of the characteristics needed for vision, in fact, multiple half formed mechanisms would be a huge detriment. That said, consider the hundreds of the complex systems present within humans? Adding time to the equation does not solve ...


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Well, you've already mentioned Alexei Kondrashov. Here's his talk (in russian unfortunately): http://www.youtube.com/watch?v=YsgO8JTN7KE To summarize it: Yes, that decay is happening and at a pretty catastrophic rate. As of 2012, he estimated the rate of fitness decay to be within the range of 1% and 10% per generation. The former is ok according to him, ...


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The interesting thing about evolution is that Mother Nature does not go back to the drawing board and start with a completely new design. Evolutionary changes happen in tiny increments. Faced with a problem like the appearance of oxygen in the atmosphere, evolution did not redo the whole genetic structure of plants. It tinkers. So we ended up with a wasteful ...


3

In a population of mice, the presence of black spots is the result of a homozygous recessive condition. If the frequency of the allele for this condition is 0.15, what is the approximate percentage of heterozygous genotypes in this mouse population? (Assume that the population is in Hardy-Weinberg equilibrium.) We know the frequency of the allele (0.15) ...


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My point in stating what is below is to emphasize even when polyploidy is present in closely related species there is a question of why an organism can survive one ploidy event but not another and why tolerance of polyploidy varies among similar organisms? Several species of deciduous azaleas are tetraploid. Closely related diploid deciduous azaleas are ...


3

pure randomness does not seem like something that can survive in a long evolutionary process. I think this is because you don't quite understand (no offense) the interplay between mutations and natural selection. You should have a look at Understanding Evolution. The overall discussion of mutagenesis I can find focuses entirely on "damage" This is ...


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Did you hear about the historical Luria-Delbrück experiment where they demonstrated that in Escherichia coli mutations conferring resistance to antibiotics are essentially random? Also, discussions and some references on the phenomenon of (directed) adaptive mutagenesis, which I think you are asking about, is mentioned in the Wikipedia article. But I don't ...


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That is an evidence that all the creatures share a same ancestor from evolution. About the origin of the genetic code, scientists proposed some hypotheses to explain it. Chemical principles: From the experiments, scientists found that some amino acid have a selective affinity to certain triplet codons. Biosynthetic expansion: The original creatures may ...


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Preamble Any answer regarding the origins of our biochemical evolutionary origin will be reasonably speculative given that this is a very hard question to scientifically test and this field is generally understudied to say it is pretty much the most fundamental biochemical question. But there are a few reasons why RNA makes sense as the prime genetic ...


1

I believe that the answer to this question would be that we cannot tell for certain that there were multiple origins of life. In order to determine that there were multiple origins of life, we would almost certainly need to look into the molecular biology side of these organisms, since convergent evolution makes it extremely likely that these differently ...


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It is interesting that all forms of life use the same genetic code. The nucleotides composing DNA and RNA are universal. Eric Lander, geneticist from Harvard/MIT cites this as evidence for evolution from a single ancestor. I think your instructor may be saying that it's possible alternative adaptations for initiation of life may have occured and perhaps not ...


0

The genus Rhododendron has been divided into some 900 plus species. Often these species hybridize in nature creating what are called hybrid swarms. Although most Rhododendron species are diploids there exists tetraploid, hexaploid, octaploid, and decaploid Rhododendron species. Contact zones between Rhododendron species containing diploid and tetraploids ...


1

Could not fit in a comment.... Northern Africans and Indonesians have pretty much the same skin color (to my first impression). Sub-Saharan African (that you don't talk about) are darker. And Northern Africa in not an equatorial region (not more than Los Angeles) as it is right under the tropic of cancer. Also I am a little confused about who you call "we" ...


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From jzx's answer, I thought of a possible answer to my own question. Maybe not producing identical twins all the time is a paradoxical evolutionary stable strategy for the following reason: Until recently in evolutionary history, the population remained constant when parents only had enough food to feed 2 children. Siblings didn't evolve to be fully ...


2

What you describe could have happened under the right conditions. However, there are a few things you haven't considered. Because humans are especially altricial, always having twins would double the cost of children on parents. The benefit of sexual reproduction is immune diversity. So a population like this could be far more vulnerable to disease. So ...


-1

If we produced identical twins all the time then we'd completely lose genetic diversity which would, I assume, overwhelmingly compromise our adaptive capabilities. Don't forget, those identical twins then need to reproduce with other identical twins of others families. Moreover, and this is the more obvious explanation, as a consequence deleterious recessive ...


5

General overview. Each toxin and poison probably has it's own evolutionary "arms race". Generally an organism contains a compound that is a bit harmful to other species. As a predator or prey species becomes tolerant to low doses of this compound through natural selection, the compound efficacy could be increased (again by natural selection) on a molecular ...


3

Sortof. Just as every adaptation is the product of a small change in something the species already expressed, all toxins start out as something the organism just happens to produce as part of its life. Then there are two evolutionary paths for useful toxins: Poisons - "If you eat me, you will be sorry." These typically begin as metabolites that happen to ...


0

The amount of recombination events does not have anything to do with homologous recombination repair and meiotic homologous recombination, protein-wise. Homologous recombination repair is a "very safe" repair system, especially compared to the alternative option, Non Homologous End Joining, which is really prone to indels. On the other hand, meiotic ...


0

Perhaps customs (and culture as a whole) arises to some extent as a result of relationships between individuals of the same species. For example, I think a good example of a custom is how elephants bury their dead. This does not benefit the surviving elephants in any noticeable way, and is a "waste" of energy and time. If customs do arise because of a group ...


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From the way I have read what you have written z(1-z) translated into a sentence would be the frequency of the neutral variant (z) times the frequency of all other possible variants (1 - z) at the particular time t. Nucleotide diversity is then the average of 2 times the sum of all of the frequencies of neutral variants (z) times the the frequency of all ...


2

The term allelic class is defined in Innan and Tajima (1997) Suppose that there are two nucleotides, say A and T, in a particular site.Then, we can divideDNA sequences into two classes: one class includes sequences with A and the other includes sequences with T in this site. We call such a class an allelic class Two elements that were misleading (for ...


1

I agree with some comments that have been made on the validity of the wording used by OP. However there is a legitimate thrust to the question. What could drive Lion sociality? Females are the base unit of lion social groups. Males are generally the nomadic sex. Male lions will try to take over a group of females by killing the current cubs and mating with ...


1

This doesn't directly answer your question but my current research is on building models that combine ecological and evolutionary processes. Thompson (1998) is one of the earliest papers to talk about rapid evolution on ecological time-scales. And also a recent paper highlighting the interactions was Schoener (2011). Perhaps reading through these two ...


2

You are right. Consider a population at some point back in time and ask how many of the individuals left descendants that are still alive today?, the answer will be between 1 and N (inclusive), where $N$ is the population size. We call this process coalescence A tiny introduction to coalescence Consider a population of constant size $N$ and to the previous ...


5

Regarding the reference to Lynch, actually reading this paper is illuminating (http://www.pnas.org/content/107/3/961.full). What Lynch is saying with regards to degeneration is that he and others feel that modern technological advances may relax selection pressures, thus allowing the survival and reproduction of many who would otherwise be selected against, ...


2

A small addition to what March Ho has mentioned in their answer. Fitness is not absolute; it is dependent on the present environment. Fitness has no meaning when the selection factor is not defined. You can consider a commonplace example: Can you, by just looking at an individual say how fit they are (of course I am not talking about those who are ...


7

If I understand the question correctly, you are asking why random mutations (most of the non-silent ones are deleterious) cannot create information and improve the overall fitness of the organism. This is a common creationist statement, and has been shown to be incorrect in many different ways. The best way this can be shown to be false is by simply ...


2

If you take two modern species (let's denote them with A and B) you can't really say that A is an ancestor of B or vice-versa, but you can say that they are related to some extent, that is they have a common ancestor that lived X years ago. But then all eukaryotes are believed to have a common ancestor that lived an eon ago. Hence the notion of phylogenetic ...


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The theory developed by Cajal more than a hundred years ago hasn't been challenged, according to a recent article in Molecular Neuroscience. Making it simple: At a certain point in the phylogeny, decussation is favored for the optical pathways. Since the images are inverted on the retina, the crossing is necessary in order to build a coherent and ...


2

From what I understand, the answer is; it depends. As you point out in the comment to Remi.b, contrasts are standardized by branch lengths (which are assumed to be proportional to "evolutionary time") before they are analysed (to obtain standardized independent contrasts). However, branch lengths can be come from a number of different sources (divergence ...


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Change in genetic variance From what I have been taught, Natural Selection (or even Artificial Selection) is great for panning favorable genes from a species and bringing them to the fore, however, it does not introduce new genetic changes. Yes, you are pretty much right. In a given population, directional selection will ultimately reduce genetic ...


6

You're right that the mutation must be in a germ cell in order to be passed on. Most errors are introduced during DNA replication (at a rate of around 10-10), which occurs a number of times between the zygote stage and mature gametes. This book estimates that there are 24 divisions between zygote and egg and 23n+34 divisions between zygote and sperm, where n ...


6

Short answer The appearance of psychoactive compounds in plants has nothing to do with their addictiveness in man. Background Psychoactive plants were there long before humans. The question therefore should be: "Why would humans evolve brains that exhibit addictive propensity to poisonous compounds abundantly available in nature"? The answer is: because our ...


0

The genetic code of the tree of life is actively studied. So far, all the living beings have conformed to LUCA model. They are all RNA and DNA dependent, and no other life forms are known. All the RNA and DNA life forms share a tree like inheritance pattern with more simple organisms. Sometimes there is doubt about wether mushrooms are more closely related ...


0

There are indeed massive evolutionary control systems integrated into DNA. They constitute the major force for efficient change in living beings. Random DNA mutations are not as beneficial as controlled ones, you can see random single gene mutations at work in medical books: Anemia, cancer, cheese smelling sweat, no sweat glands, skin conditions, scales, ...


1

This answer can be from many different perspectives! I'll try to blend them all together as much as possible. First of all evolution did not choose to make us love sports. Evolution made us social animals. And sports is just one of the tools we use for that purpose. Think about it, because if evolution gave us sports, then you will play sports, your kids ...


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I am providing an example which somewhat contradicts the points mentioned in the other answers regarding toxicity of alkaloids to insects. Caffeine is a stimulant and is toxic at high doses (also for humans) but at low doses it has a stimulating pharmacological effect on the organism. The same principle applies to insects as well. A study by Wright et. al ...


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As someone commented earlier, chemicals such as nicotine and morphine were products of evolution meant to repel animals. It is explained in more details in this article here. Evolutionary biologists studying plant–herbivore interactions have convincingly argued that many plant secondary metabolites, including alkaloids such as nicotine, morphine and ...


56

It's a matter of perspective. Most of the chemicals that are addictive to us humans (particularly alkaloids), and may be addictive for some other animals as well, are also insecticides. Lots of plants that we consider poisonous are good food for other species, and lots of plants that insects would consider poisonous are treats for us. This is a great ...


0

In these two cases, what conclusions can we make in particular about the evolution of the protein itself? It's not clear to me that it is right to make any evolutionary conclusions based on function alone. DNA sequence would be a FAR better way to estimate evolutionary relatedness.


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A few details One of these species, species A, is close to the common ancestor of A and B, in terms of evolutionary distance, while B is farther although for both cases, it took two speciation events to end up with species A and species B. I have two issues here. I don't understand why this information matter for your question. There are several ...



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