Is there more than one definition of natural selection?

It's good - but its not all encompassing since it misses out the generation after the next generation. If individuals contribute poorly towards the offspring of the next generation, but contributed excellently towards the contribution of the offspring of the offspring of the next generation, that wouldn't be natural selection according to Wilson's basic formulation.I prefer something along the lines ofVariation in a trait + Heritability of the trait + Differential fitness conferred by the trait = natural selectionWhere fitness is the ability of the trait to assure its inheritance. Creating or helping to create more copies of the trait implies a higher fitness.This definition, such as it is, also allows us to discuss natural selection acting in a non standard biological setting. Natural selection can occur in man made entities or life or whatever. Natural selection is universally acknowledged as a cause of evolution. Hence why natural selection is one of the mechanisms under the umbrella of the theory of evolution. There maybe some disagreement on how best to word natural selection, but on its general definition there is no disagreement. The only debate I've seen is with regards to what exactly is being naturally selected. The problem with this is that differential reproductive success can exist without any natural selection existing. This occurs when the differential reproductive success is not caused by a heritable trait.Think of 1000 robots:- Each robot has 100 instructions in memory on how to create more robots, these 1,000 robots are all made from this same instruction set. There are 10 robots built with each instruction set. They are ranked in order of how many copies they are able to make. A robot built according to the instruction set 30 will be able to make 30 more robots itself before it dies.When it comes to building a new robot, the parent robot picks a random number between 1 and 100 and builds a robot to the corresponding specification. Clearly, there is a differential reproductive success here, but there is no natural selection - the frequency of each robot-type remains basically fixed at around 1 in 100.

The first term does actually pertain to different allele frequencies, when we are discussing biological evolution. It isn't a measure. You are confusing my formulation for an algorithm of sorts. It is not, all I am saying is that when the three conditions are met, natural selection results. Perhaps a better way of phrasing the last term would be 'The trait variations affect their own replication.' There is probably a better, less clumsy way of phrasing this. If I lost my legs in an explosion I'd have a trait of 'absense of legs'. If I keep my legs and exercise heavily I become very muscled, this is a trait. Acquired traits are non-heritable.

You can define traits in that fashion if you want - but it leads you to difficulty in discussing how Lamarckism compares to Darwinism. I think it easier to simply say that Darwinism is about genetic (and thus inheritable) traits, whereas Lamarckism implies that acquired traits can be inheritable (such as a stretched giraffe neck).Just for extra confusion (as Hawks mentioned) - we have epigenetics. Then we can include acquired traits which are hereditary.My hair colour is a trait - but I can change it using dye. I can wear clothes to blend in to the background. These things can convey a survival advantage but these traits are not heriditary traits.If you'd rather - mentally replace the word trait with 'characteristic'.Edited by Modulous, : No reason given.

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Nonrandom mating is not the same thing as sexual selection. Many people choose their mates from the pool that is their workplace. This is non random mating since not all potential mates have an equal chance of being chosen, since Japanese people are unlikely to be chosen by virtue of the distance it would take to meet them.This is nonrandom mating, but it is not sexual selection.Sexual selection occurs when some heritable trait helps an organism to attract or otherwise acquire a mate. This is certainly nonrandom mating, but not all nonrandom mating is sexual selection. And it is! Nonrandom mating is not shown in the diagram for a reason. Nonrandom mating can occur because of heritable traits, geography, chronology and other concerns.

Geography, timing, random events. Random mating means that every being has an equal chance of mating with any other being. The mating completely mixes up the alleles, and thus there is equlibrium.However, there maybe alleles that reside mostly in the USA or in India or what have you because people in India mostly select other Indians to mate with. Even an Indian who has a genetic predispostion towards attracting/being attracted towards red haired women with green eyes is more than likely going to mate with an Indian woman.Nonrandom mating upsets an equilibrium even if there is no sexual or indeed any other selection going on.

Agreed - sexual selection may be happening at the same time (and often is), but it doesn't need to be. If the reason he picked that mate was nothing to do with genetics (it was all that was available (population very thinly spaced) or a good haircut or a healthy diet). Naturally these things can have genetic causes, but if we imagine a situation where genes are not affecting things (or they are affecting things equally), we can see that a model exists whereby nonrandom mating occurs without sexual selection.The point being, that just because a mate chooses its sexual partner based on some criteria, that criteria does not need to be entirely genetic. It can be entirely non genetic, or only partially genetic. The genetic parts constitute sexual selection. The non genetic parts constitute as just nonrandom mating. I agree that your example is sexual selection. Indeed, it is difficult to conceive of an example of evolution occurring in the real world which was entirely bereft of sexual selection - as indeed it would be to consider evolution without survival selection.Consider a sexually reproducing plant. It is successful because it utilizes the wind as its vector. First the wind blows around equally in all directions and we have approximately random mating taking place. Not all mating is succesful, so selection still acts to favour the better plants. We might even call this sexual selection. It doesn't matter though, since all plants equally mate with one another on average.If the wind patterns change and the wind predominantly blows north, then we have non random mating (plants tend towards mating those that exist south of them). The selection pressures also change you'll note. The northernmost plants will be selected for their spawn, and the southernmost plants will be selected for their receptivity...though this isn't particularly useful since they may end up being on the other end of the bargain in later generation. This isn't a perfect example for the same reason, but think of the populations in both space and time - an allele that is predominantly found in the centre of the population will tend to stay there, not mixing it up with the alleles far to the west. Yes, Sexual Selection is a mechanism of evolution. If one acquires a trait which has no genetic basis, then that trait will not be selected for. Its frequency will not increase over time.However, acquired traits that affect sexual attractiveness can certainly lead to nonrandom mating. They're very good questions.

And you'll probably be waiting a long time too! Sexual selection is definitely nonrandom mating. However, not all nonrandom mating is sexual selection. Just because all fast cars are red, does not mean that all red cars are fast. There is no need for HW equilibrium being a reference point for defining evolution. Any change in allele frequencies is defined as evolution, HW equilibrium is simply an unnecessary entity in defining it.I'm not entirely sure you've nailed the understanding HW equilibrium here, it seems you seem to using to mean an Evolutionarily Stable State. Any redistribution of allele frequencies is evolution, regardless of what resulted from it.

Yes - Evolutionary Stable State. No - better yet would be 'change in a population's allele frequencies over time'. If there is no mutation, no gene flow, random mating, no genetic drift and no selection we can calculate what the equilibrium of allele frequencies is (HW equilibrium).As such we can judge if evolution is occurring when the HW equilibrium is breached. However - this is not really practical, since we can never discuss a population with no selective pressures. They simply cannot exist.As such, trying to judge if evolution has occurred from the HW equilibrium point of view is basically impossible - it remains a concept based purely in theory. Any change in frequencies disturbs the equilibrium, so all we need to do is define evolution simply as a change in allele frequencies.

Then it isn't sexual selection. At least not sexual selection in the sense Darwin proposed, and later biologists perfected. You seem to be talking about a completely different phenomenon entirely. A thread (Sexual Selection, Stasis, Runaway Selection, Dimorphism, & Human Evolution) has been had, but perhaps it might be an idea to start a new thread dedicated to sexual selection and what it is?

So you are postulating that big noses are selected against. That is natural selection. Other selective forces (such as survival) may be acting against this selection and we see a compromise. We see this in reverse all the time. Female peacocks may favour even more extravagant tails - a selection pressure acting to increase extravagance, but the survival selection is acting to keep the tails as practical for survival as it can.Survival pressures act against one another - the cheetah would like to be able to run faster, but the costs of doing so may be too great - and thus the two pressures reach an equilibrium Sexual selection does not invoke natural selection. Sexual selection is natural selection. Sexual selection is just the selection for genes which code for a trait that directly increases the ability of an individual to attract a mate (or fight for mating rights etc etc). It is just natural selection with regards to a certain kind of trait. It gets special mention because of course, natural selection as you so often say, is about differential reproductive success - so any traits which directly help an organism influence their chances of reproducing would be sexual selection.

Not really. Your scenario neglected the entirely realistic point that good looking people would get laid more often than than the ugly ones. The ugly ones might get it sometimes, but not as often as the attractive ones. You essentially neglect that one attractive male, might date the entire cheerleader team because he can, and that one attractive female might date the entire football team. And, if we are talking about reproductive acts - there will be more attractive people born than unattractive people.Which would be sexual selection for attractive traits - one attractive member manages to either impregnate or get pregnant multiple partners as opposed to only one partner, or no partners at all.If it turns out that ugly people have as many children as attractive ones, but with fewer partners, then there would be no sexual selection. Individuals would still be selecting partners, but that isn't sexual selection (the biological term), that's just individuals trying to find 1 or more available mates.