New answers tagged

2

But cyanobacteria do not seem to use polysaccharides in the same way as plant cells do (building materials, for example) The Calvin-Benson cycle produces glucose which is the starting material for a lot of biosynthetic pathways including that of the nucleotides (ribose from the pentose-phosphate pathway). Glycolytic intermediates are also involved in ...


0

There are a lot of theories about how homosexual behavior might be maintained in a population or provide some evolutionary advantage. One thing to remember though is that there is a big difference between homosexual behavior and obligate homosexuality. One could quite easily confer benefits, like any other intra-sex social interaction. The other carries a ...


1

Why do you think that the only benefit from photosynthesis is polysaccharide synthesis? Photosynthesis allows an organism to convert photons into chemical energy. That chemical energy can be stored as polysaccharides and used as a building material, but it can also just be converted into some other compound, or just used to run the organisms metabolism, ...


1

Another source of developmental noise is due to diffusion. Diffusive processes are stochastic and induce noise in morphogen gradients and results in the concentration as being "jagged". Recent results have directly measured the noise in morphogen gradients of the developing zebrafish. In fact, when you think about the low copy numbers of transcription ...


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I know of an example in development biology. Here is an example where noise in retinoic acid gradients is required for the boundaries in the developing hindbrain to sharpen. A related result is that the zebrafish hindbrain has a protein to modulate noise, but does not reduce the noise to zero. Together these results show that noise in the retinoic acid ...


1

Fitness of the colony vs fitness of a single worker Bees have a division of reproductive labour (they are eusocial). Only a queen reproduce (and the males called drones) while the workers dedicate their existence to ensure the survival of the colony. If committing suicide will be of any help to the colony then one would expect a bee to do so. What I just ...


0

Does this mean that the interspecific hybrid is fertile? Yes But is it possible, that an interspecific hybrid is fertile? Yes You might be confused by the idea that by definition two species should not be able to interbreed. If so, then you should have a look at How could humans have interbred with Neanderthals if we're a different species?.


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It's a very simple answer. "Unhealthy" foods, for example potato chips, sugary drinks, and other fatty, cheesy or sugary edible items, have only been around a few hundred (at most) years. In prehistoric times (before agriculture, when the primary source of food was hunting and gathering), when food was scarce, fatty and sugary foods would be of great ...


0

I assume this topic has been discussed elsewhere on Biology SE, but I’ll add something specifically about the beta chain in my answer, as this was specifically mentioned in the question. Briefly, you are correct. Haemoglobinopathies affecting the beta globin chain are found in malarial regions of the world. Two major examples are Sickle Cell Anaemia in ...


1

Both are correct. From Wikipedia, the causes of genetic change within each now-separate population are: (a) they become subjected to different selective pressures, (b) they independently undergo genetic drift, and (c) different mutations arise in the gene pools of the populations. It is possible that factors a, b, and c cause the emergence of 2 new species ...


0

Absolutely! The only limitation animals face on eating substances or objects is the size of the opening to their oral cavity, so if there is something on another planet that will fit in your mouth then you can definitely eat it. Whether one would be able to derive energy from the exo-material is an entirely different question.


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Short Answer- No, chances are negligible. Long Answer- Digestion is a chemical process which is mediated by enzymes. Enzymes are highly choosy molecules so that they only perform the work they're made for. In digestion, enzymes like proteases (for breaking down proteins), lipases (for breaking down lipids), amylases (for breaking down starch), DNAses (for ...


3

The short answer is NO. Here, very briefly (since it would take to much to properly analyze all the aspects of this topic), is why: First of all, the environment is constantly changing so there will be no such thing like 'the end of evolution'. Even if you try to stabilize the environment artificially (a lab setup) the organisms will continue to interact ...


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An issue in the question that I will ignore You say Does the evolution head to some optimum that in future we will have only one species which will be superior to all other extinct form of life? Firstly, it is a little bit weirdly phrased. By "superior" I suppose you would refer to a species that could outcompete all the other. This sounds very ...


1

I am just repeating @emhart answer but wanted to highlight the semantic. There are several ways an individual can inherit from its parents. Genetics Through transmission of DNA. An acquired trait cannot affect DNA sequence directly and therefore cannot be inherited genetically by the offspring (this sentence is the answer to your question). Note ...


0

-Bacteria 1 is least related to Eukaryote 4 (the furthest branch is always the least related as there common node is furthest away, correct?) In terms of relative relationships, eukaryote 4's least-related relative is Bacteria 1. Bacteria 1's least-related relative is the entire rest of the tree -The most related organisms are Bacteria 2 and 3, and ...


1

Great question! Christiaan's comment is the best way to start thinking about this; why should the virus care? In other words, what determines the selection pressure to increase or reduce virulence? The most common definition of virulence in ecology is the reduction in host fitness resulting from infection by a pathogen. If reductions in host fitness also ...


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It's very complicated to know how a trait would have been selected for or against in the ancestral environment. Tendency to gain weight does seem to have been selected for in some populations - e.g. pacific islanders. Presumably the decreased chance of dying from starvation was enough to compensate for any increased risk of heart disease, if in fact health ...


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You're confused because you're failing to distinguish between 'identical' and 'identical by descent'. Some pairs of alleles would still be identical even in the absence of inbreeding. We model the inbreeding by classifying allele pairs as IDB - always homozygous - or not IDB - distributed according to Hardy Weinberg. The frequency of a pair of alleles ...


3

From Wikipedia: Anagenesis, also known as "phyletic transformation", is when the new morphospecies is a result of rapid evolution in the ancestral form without speciation taking place, such that there are no remaining other populations of the ancestor species and the species can be considered extinct. [...] Anagenesis is in contrast to the branching ...


1

There is generally a pressure for parasites to be harmless towards their hosts (apart from the drain in resources), especially if those two species have co evolved for a long time. This sets them apart from parasitoids. Though those terms are sometimes used interchangeably, a parasite requires its host to live on while a parasitoid aims to ultimately kill ...


3

While the attempt to consider this in a mathematical framework perhaps isn't so useful, it seems that the biological essence of your question is along the lines of: Does a Batesian mimic initially need to be initially quite similar in morphology to the different species which it evolves to mimic? The answer is no, morphology does not need to be ...


1

The main reason is that there really isn't any one "cold," but rather the word is used to describe many different infections that simply have the same symptoms. The reason for these same symptoms is that almost all of the symptoms that one experiences in a cold are actually the immune response to said infection. For instance, a fever is used to make the body ...


32

There are (at least) three important factors to consider here; evolution under selection requires genetic variation upon which to act, selection can act on covarying traits causing trade-offs, and adaptation also occurs in the predator. A lot of this is covered elsewhere on this site (including the effects of the other mechanisms of evolution), but little ...


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There are two reasons for this: evolutionary trade-offs and coevolution (the "Red Queen hypothesis", as mentioned in the comment above by Luigi). Evolutionary trade-off describes situations where one trait cannot increase without a decrease in one or more others. Some hypothetical examples: longer legs may help run faster but past a certain point will ...


2

Generally speaking, predators will always be faster than prey at a certain given level of biological (or technological) evolution. This, indeed, follows from the obvious observations: Herbivores consume food with low energy density. This means: a. Substantial percentage of their time is spent eating and processing food. b. Substantial fat and water ...


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There are both costs and benefits to being able to run faster, both as a predator and as a prey animal. In short, maintaining the large muscles necessary to outrun a cheetah every time is metabolically expensive. So it isn't a matter of being able to always outrun a predator--it's a matter of how to optimally allocate precious resources either to ...


1

Predators always have to be much better hunters than the prey - they must eat every few days after all. But they can only get so good. Predator/prey population balance will tend to look like a competition where if the predators are too efficient they will kill off the prey. If that happens they start to starve to death. If the prey outrun the predators ...


8

The reason that chlorophyll is green is because it absorbs other colors of light such as red and blue, so in a way the green light is reflected out since the pigment does not absorb it. Because life might have been purple: It is possible that the very first life form to process light may have been purple colored. This would mean it was reflecting red ...


1

This example proves IMHO that migration is largely nature and not nurture: In the Netherlands, white storks were bred / reintroduced. A large part (about one third?) of the reintroduced birds do not migrate, but their offspring usually does migrate see. They couldn't have learned it from their parents, that's for sure.


1

Is there a difference? Yes, they are quite different things. What is group selection? Group selection is an view of evolution where selection acts at the level of the group, rather than the individual. It suggests that selection is mediated by fitness of the population, and leads to conclusions of things occurring for "the good of the species". It is ...


2

The concepts are very similar but there are a few differences. Firstly, fitness is usually applied to alleles or genotypes, reproductive success to individuals. Secondly (and partially as a consequence of this), fitness is an average or idealised/expected property across a population; but actual reproductive success per individual is stochastic. ...


12

The whole point of Darwin's theory was that transition from one species to another is extremely slow and gradual. There are plenty of quotes in "Origin of Species" stating this, and also affirming that there is no clear boundary between species and subspecies, or "races". Quotes from Origin of Species > Variation under Nature (Chapter 2) Quote 1 ...


1

Several proofs are given here (p. 9). My favorite comes from the genealogical argument: Consider the situation where there are $2N$ alleles: $A_1$, $A_2$, $A_3$ ... $A_{2N}$. By the genealogical argument, we may state that at $t = \infty$, all alleles at this locus will be direct descendants of one particular allele present at $t = 0$. Allelic variants at ...


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Well another (and less popular) theory called Panspermia says that life, actually, came from space, it was not originated here in earth. So this completely change everything, because the conditions where life would have been formed could be very different from our's planet, so we can't make any predictions with this considerations in mind. But thinking in ...


1

This question is a matter of discussions, but I'd like to mention that there's basically two viewpoints. The first viewpoint is that the symmetry breaking is global (in other words, there's a reason why exactly L-amino acids; if there are other planets with Life, L-amino acids should be "used" on all of them or at least on the major number of them). The ...


3

What is new in his theory? What problems in evolutionary theory does it address? No major problems really. The problem he is claiming, or at least how it is portrayed, doesn't really exist. To borrow from my answer to your since closed question (see that answer for more): "Wagner appears to suggest that Darwin's theory relies on novel mutation ...


10

Wagner does not propose any new theory. He uses the word innovation to mean evolutionary adaptations that manifest qualitatively different traits. In fact, he has himself not defined it properly in the mentioned book. This is what he has written about the term innovation: It may be difficult to define rigorously what an evolutionary innovation is ...


2

Are kin selection and group selection the same thing? Yes and no. Yes: These days people tend to use the "direct fitness approach" (Taylor and Frank JTB 1996). It turns out that this is based on EXACTLY the same equation as is contextual analysis, which is the currently favored approach for measuring multilevel selection in natural populations ...


7

The flaw in his argument, from what I can see in your quotes, is to equate evolution to natural selection. Natural selection was never proposed to explain all evolution, nor how advantageous traits arise, but was proposed to explain how advantageous traits spread. Ultimately, why adaptation is so prevalent? The modern theory of evolution is so much more ...


0

There's two parts to your post that I want to address, the first is the quote (because I want to make sure you understand it well), and the second is about general inference methods for estimating the genetic composition of ancestral populations. The Quote: Selective Sweeps A selected variant that increases rapidly in frequency in the past ~250,000 ...


1

"Toads", as commonly used, are not a monophyletic grouping - that is, all toads do not descend from a single common ancestor which only produced other toads. Instead, it's a polyphyletic grouping of those frog species which show common morphological characteristics related to a primarily terrestrial lifestyle. As a polyphyletic group, the parsimonious ...


0

There are really two ways to infer past genetics. Sample the past. Only really works if you have well-preserved uncontaminated archaeological samples, but works surprisingly well, considering. The accuracy and completeness goes down fairly quickly as you go back in time but thousands of years to hundreds of thousands of years is roughly possible. You ...


4

The methods that come immediately to mind are mostly related to next-generation sequencing. You can do deep sequencing on your sample, which is just increasing the coverage as much as possible to find rare events. You can do RNA-seq to look at the transcriptome, ChIP-seq to look at chromatin modifications, and single-cell sequencing (a form of deep ...


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Short answer Before the RNA world, mineral surfaces may have facilitated the prebiotic containment and organization of biomolecules. Minerals are believed to have promoted the transition from a dilute chaotic prebiotic “soup” to highly ordered local domains rich in key biomolecules. Background As pointed out by others, the transition from a hereditary DNA ...


13

So earth is estimated to be around 4.5 billion years old, and life has existed for about 3.4-3.9 billion years of that, around >75% the time. For a little perspective, Homo sapiens have been around for up to ~250,000 years, just 0.00005% of the time earth has existed. In that time the earth has changed massively, early earth was pretty hostile, but that ...


3

You can do without DNA, you need RNA to make proteins. Living organisms create and maintain a bubble that is very far removed from thermal equilibrium. So, you can speculate that at the origin of life, conditions existed where processes that are far from thermal equilibrium could still occur naturally without the support structures one finds inside living ...


1

I wonder whether it is just some sort of functionless drift. I don't know about bacteria, but think the example of some human viruses may be instructive. The human herpes simplex 1 virus (causes cold sores) has a very high GC content, whereas the quite closely related (in terms of gene repertoire and organization) human varicella zoster virus (causes ...


1

Interesting question. I think that bacterial GC content diversity boils down to a mix of mutational biases, such as using different polymerase and replication/repair gene isoforms, and environmental pressures, such as temperature and salinity, that have placed different selection pressures on the various microbes. I would read over the linked papers for ...



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