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1

What do you mean by gene-centric view of evolution I am not totally sure you know what really means the gene centric view of evolution. Everybody agrees that selection (also) acts on genes and that selfish genetic elements exist. I think that what one calls the gene centric view of evolution is nothing but the modern synthesis of evolution (following the ...


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First, you need to recognise the difference between Natural selection and Artificial selection. As a basic definition, you can say that in natural selection, selection is done on fitness (overall, long-term success of reproduction) and is determined by the complete living environment of the species. In artificial selection, selection is done by humans on a ...


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Selection is a mechanism of evolution which favours specific forms of traits over others, this can cause the spread of beneficial mutations through a population. Natural selection is the spread of beneficial traits/genes through populations as a result of the natural variance in their effect on reproductive output (a function of life history traits like ...


0

In principle, eugenics is just like selective breeding of animals and plants. For example, dogs have been bred for a variety of traits to fit into several niches, and corn has been bred to produce large yields in several climates. Eugenics would attempt to do the same for humans. However, no one agrees on how to "improve" the human gene pool, and far too ...


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As I have already mentioned in my other post, the most important role of urea synthesis by humans is blood pH regulation and urine concentration, so it is not just about excreting a waste product... I don't think human body is very special in this case, so I think most of the urea excreting mammals use urea for the same purposes. The urea is created from ...


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Our knowledge about the sexual transmission of mitochondria and plastids (hereafter organelles) in isogamous eukaryotes comes mostly from studies of the yeast Saccharomyces cerevisiae and the green alga Chlamydomonas reinhardtii which are both unicellular species. To investigate organelle inheritance in a multicellular organism with ...


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This just got too big for a comment and I think might actually qualify as an answer. Can you give me a source for what you're reading? According to this, which matches the definitions you are using, K=(Nu)/N=u where K is the substitution rate, u is the mutation rate in the population, Nu is the individual mutation rate, and N is the population size. I went ...


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Suppose a gene performs two distinct functions 1 and 2, both of which are essential. We'll call this gene A, for ancestral gene. A duplication copies A to another locus. Now there are two genes, A and B, that perform the same two functions. At this point, if either A or B is deleted, the organism is fine. Over evolutionary time, A and B undergo genetic ...


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LUCA was the LAST universal ancestor not the first. Naturally it competed with other extinct species. My reseach suggests that LUCA was resulted from the fusion of 2 genomes. The evidence for this is that on reconstructing the amino acid sequences for LUCA enzymes we find some contain no cystine but do contain tryptophan or the opposite.


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There are many different ways to do this, depending on what assumptions you make on e.g. stable age structure, distribution of offspring, haploidy/diploidy, population growth etc. As you probably know, there are also two main approaches to effective population sizes, namely ones based on; 1) the rate of inbreeding ($N_{e,i}$) and 2) the increase in variance ...


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From Conner and Hartl's A primer of ecological genetics: "Any variance in reproductive success among individuals greater than random expectations, a commonplace concurrence in natural populations, reduces effective population size." So yes, selection does reduce the effective population size and for the reason you suggest - it removes some ...


2

You can't predict the evolution of anything because evolution is driven solely by the environment. It is the environment that squeezes species into to specific forms. We have has a much say in our shape and form as a whirlpool does and for the same reasons, both humans and whirlpools result form powerful outside forces. In order to have shot at even making ...


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There are multicellular organism which do not actively eat other organisms, however, there are no organisms period who do not kill other organisms. Trees, and other vertical plants, evolved in the first place in competition for sunlight. For plants, being in the shade is like smother or starving a human since they literally use sunlight to create and ...


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Yes, plants! Plants are autotrophs. While Animals and fungi are heterotrophs. Have a look to the wikipedia articles. In short, autotrophs organisms are organisms that synthesize their own compounds from inorganic compounds. Heterotrophs organisms are organisms that synthesize their own compounds from organic compounds. Therefore, any multicellular plants ...


2

I don't fully understand how your model works I don't fully understand how you model your population. Is it a standard $oop$ (object-oriented programming) where you simulate each individual? Or is it a simulation where you already use some mathematical model? You could eventually copy-paste your code. it is probably not very long, right? What language did ...


1

If rates of meiotic recombination DIDN'T vary across species - THIS would require an explanation! After all, evolution creates diversity, not homogeneity. I can only wonder that more recombination would allow for a faster diversification. The more DNA you shuffle, the more distinct each individual offspring may be (though I'm not 100% sure). The ...


1

Could not fit in a comment... This post (and the excellent answer from Richard Smith-Unna) lists the species that have the smallest genome that we are aware of in different clades. Yes we can/could sequence these tiny genomes and try to understand what each sequence does. I think that to understand the minimum requirements for life you will mostly be ...


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You can have a look to the most basal branches and you may get a pretty good idea of what those early plants looked like. What we call plants is what we call plantae or Archaeplastida in Latin. This clade contains the red algae and the green algae. Within the green algae are the land plants. In the land plants are the embryophyta which contain all what you ...


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I don't think it is a clever thing to group all types of decussation and look for a general explanations. I would tend to think that different decussation have different explanations. It is like asking what are the hypothesis to explain evolution of body size. There is no general answer to that but only a list of case specific impact of different factors on ...


1

You can see the wikipedia article on meristem. The apical meristem differentiates into floral meristem that gives rise to flowers. From this the cells specifically expressing APETALA3 (AP3), PISTILLATA (PI), AGAMOUS (AG) and SEPALLATA (SEP) would give rise to the stamen [ref]. CRC gene is essential for female development and plants lacking this will not ...


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The problem with Intelligent Design is that it doesn't appreciate that the forces that shape species (and individual organism) have to be constant and ongoing or the species disappears. The past matters little, it's what happens right here, right now that keeps species in any particular form. Biological system are not static structures like a building. You ...


1

"I imagine that turtle looking up at that food, and sub-consciously wishing to get to it, constantly straining, for it's entire life time. It seems plausible to me that we (advanced life) could have a biological mechanism to "write" needed alterations into either our own DNA or our reproductive DNA over time, triggering the very specific ...


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Evolution is about descent with modification. Spontaneous generation doesn't have that. It's about modern organisms emerging from raw molecules. If flies spontaneously appeared from rotting cow meat, why would they have DNA that made them look like they were evolutionarily related to other insects?


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You are right in the sense the evolutionary biology doesn't try to explain the origin of life as it is not within its scope. Other fields of biology investigate the question of origin of life (abiogenesis). Now, there is a very important difference between spontaneous generation and evolution. Life originated at some point and the through repetitive ...


2

Here is a more morphologic, less genetic answer: According to this article, the 2 sets of paired appandages (shoulder and pelvic) was set in stone when agnathans transitioned into gnathostomes (ie. when the first vertebrate organisms began to evolve jaws, an anatomic change that allows for classification of different stages of history found in the fossil ...


1

This article claims to be a new level of evidence for group selection. Its a little early to tell at this point whether the critics will be moved. They have not been in the past! sorry if this is a bit short - its late, but i'll try to come back and do more later..


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The answer by Remi.B is excellent, I'll just attempt an explanation by way of gene networks: In genetics we see new genes "linking" to the older genome by regulation pathways and by being "fit" only in the context of the existing genome. This has the effect of making the older genes indispensable. Change them and you rupture the whole mesh. If you want to ...


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I think I might interpret your question as asking, not just why don't mammals have more than four limbs, but why arthropods have more variety. Insects have six, but others have eight, ten, or more. Partly there are just many more species of arthropods. 80% of animal species are some sort of arthropod, and some lineages of arthropods are distantly related ...


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Number of legs in terrestrial vertebrates Not only mammals have four legs but actually all terrestrial vertebrates (which include mammals) have four legs. There are slight exceptions though of lineages that have lost their legs. Typically snakes have no legs anymore. Apesteguia and Zaher (2006) discuss the evolution of snakes legs reduction and report a ...


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Remember, evolution says things don't initially develop "for a reason" -- they develop at random, non-harmful mutations are kept in the gene pool, and eventually a selection event occurs (opportunity to exploit another food source or avoid a hazard) which selects for the mutation in some subset of the population. Over the kind of timescales evolution works ...


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The main reason for bats to "develop" their echolocation system was the avalability of an almost empty niche: Hunting insects at night. Birds are not able to hunt without light and here is where the bats come in. They are able to hunt at night and also to live and orientate in environments where they are protected over the day: Caves. Bats at night are also ...


2

As canalization is defined in your question (also in wikipedia) it means robustness. Semantically it is possible to differentiate the two. Robustness of a system refers to its sensitivity to perturbations. In other words small differences in parameters would not affect the steady state of the system (parameter changes in a physically plausible range ...


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Thanks to the other answer for pointing me in the right direction with some references. It seems that two biologists in the early 1990s had a back-and-forth over this topic in The Quarterly Review of Biology.1,2 A statement of the problem: The function of menstruation is a cen tral enigma of mammalian, and especially primate, reproductive physiology. ...


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If you are interested in this question, I highly recommend you look at the work of Jack Szostak - Nobel Prize winner at Harvard who is currently doing some of the best work in this area. His work is grounded in good experiments that point to how abiogenesis could have happened.


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I think that it started like this: First stage: Chemicals like Na, Cl, O₂, O₃, CO₂, CO, HCN, and H₂SO₄ react to form small molecules. Second Stage: Next those small molecules react to form macromolecules. Third Stage: DNA, being the most stable was first to replicate. A membrane eventually enveloped this and formed the nucleus Fourth Stage: Via ...


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It is a very nice question. From wikipedia: Though there is some disagreement in definitions between sources, menstruation is generally considered to be limited to primates. Overt menstruation (where there is bleeding from the uterus through the vagina) is found primarily in humans and close evolutionary relatives such as chimpanzees. It is common in ...


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Lots of interesting questions! Let me try to address a few of them as I don't think I am qualified to answer them all but hopefully I can get this thread started. I am a graduate student in the biophysical chemistry field and have been following a little bit of the Crispr Cas9 craze in the last couple of years. So I am not an expert on Cas9 by any means but ...


0

Hansen (2006) says (middle of page 19): A link between genetic and environmental robustness is plausible, because genetic en environmental disturbances ay often affect the same functional pathways in the organism, and any increase int he robustness has been fund in studies of RNA folding (Ancel & Fontana 2000), in the effects of heat-shock proteins ...


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With all due respect, a few of these answers, although good examples of selection at work, were voted too high given the specific question asked: “documented examples of by evolutionary leaps being made, over the course of just a few generations?” Sometimes we’re better being honest and identifying something as an ‘unknown’ or ‘yet to be observed’ than to ...



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