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May 19

DOMINANT and RECESSIVE

1. What is a dominant traits and their example 2. What is a recessive traits and their example 3. 1.a If the mother is curly hair and the father is straight hair the baby is? 2.b If both parents are dominant the children is? 3.c If both parents are recessive the children is? —Preceding unsigned comment added by Syoregem (talk • contribs) 07:02, 19 May 2011 (UTC)[reply]

Please do your own homework.

Welcome to Wikipedia. Your question appears to be a homework question. I apologize if this is a misinterpretation, but it is our aim here not to do people's homework for them, but to merely aid them in doing it themselves. Letting someone else do your homework does not help you learn nearly as much as doing it yourself. Please attempt to solve the problem or answer the question yourself first. If you need help with a specific part of your homework, feel free to tell us where you are stuck and ask for help. If you need help grasping the concept of a problem, by all means let us know. I have slightly reformatted your question Richard Avery (talk) 07:11, 19 May 2011 (UTC)[reply]

You seem to be asking about Mendelian inheritance. -- CS Miller (talk) 08:20, 19 May 2011 (UTC)[reply]

Pay special attention to the heterozygous vs. homozygous traits. ~AH1 ^(discuss!) 00:36, 20 May 2011 (UTC)[reply]

Most efficient way to convert heat to electricity

Is heating water, producing stream and running the turbines with steam (as done in a nuclear power plant) the most efficient way to generate electricity from heat ? What other methods can be used to convert heat to electricity ? I am looking at ways of converting solar (heat) energy into electricity for household use (like lighting a bulb or charging a battery). - WikiCheng | Talk 11:36, 19 May 2011 (UTC)[reply]

I suspect the task can be divided into mechanical and solid state approaches. Steam turbines, or even wind turbines driven by rising columns of heated air are mechanical methods. So too are Gas turbine plants which use the burning of gas to drive a turbine directly. The photovoltaic approach used in solar panels, or thermocouples, are solid state approaches. Each finds a place in the spectrum of electricity generation. My knowledge is limited, but I'm of the impression that photovoltaic methods tend to be used in small scale solar gathering, whilst steam tends to be used in larger solar installations, and in coal, and nuclear generation. Gas, for all I know, goes either way - either steam conversion or direct turbine drive. --Tagishsimon (talk) 12:05, 19 May 2011 (UTC)[reply]

An engine that turns thermal energy into mechanical work (e.g. by driving a generator to produce electricity) is called a heat engine. The maximum theoretical efficiency of a heat engine is 1 - T_c/T_h where T_c is the temperature of the cold sink and T_h is the temperature of the hot source. In practice, a real heat engine will operate some way below this maximum efficiency because of energy lossses. However, the most efficient heat engines tend to be those that operate at the highest temperatures. According to our article on solar thermal energy, the most efficient type of solar powered heat engine is a solar dish that concentrates solar energy to produce high temperatures at its focus and uses this heat to drive a Stirling engine. Gandalf61 (talk) 12:08, 19 May 2011 (UTC)[reply]

It's best if you can avoid turning the energy into heat in the first place. Living organisms for instance are very efficient in extracting energy from food without needing the high temperatures of a generating station. Dmcq (talk) 12:40, 19 May 2011 (UTC)[reply]

Yes, but that food is either plants or other animals in a food chain that ends in plants. According to our article on energy conversion efficiency, the efficiency of photosynthesis is only "up to 6%", and as you go up the food chain there are more and more energy losses and hence even lower efficiency. So the efficiency of living organisms as a mechanism for extracting energy from solar power is not at all good. (If it were, every forest would be a power station). Gandalf61 (talk) 13:17, 19 May 2011 (UTC)[reply]

But, does it matter being efficient, if the energy comes from the sun? If you catch 5% in a plant of $x or 50% in a plant of $10 * x is irrelevant. Being efficient regarding sun energy and being efficient regarding fossil energy has a quite different dimension. Quest09 (talk) 15:37, 19 May 2011 (UTC)[reply]

It does matter, yes, but not as much as with a more limited resource like petroleum. Solar power, is, of course, also limited, in that only so much hits the Earth at any given time. This is way more energy than we actually need, of course, but the amount of sunlight that hits a small spot, like the roof of a building, can be quite limited, so efficiency at conversion becomes more critical there. There's also the cost of solar cells to consider. If the cost is fixed, it will be more cost effective if each solar cell produces more energy, due to increased efficiency, and hopefully will be a better deal than continuing to burn fossil fuels. StuRat (talk) 17:12, 19 May 2011 (UTC)[reply]

Dmcq does make a good point here. While photosynthesis doesn't come close to the theoretical limit, we still have to appreciate that most biologial processes are much more efficient than most man made devices. If you are producing 250 Watts of electricity on a hometrainer, you only burn energy at a rate of 1000 Watt, while your body temperature does not rise by more than 1 or 2 degrees C. Count Iblis (talk) 15:57, 19 May 2011 (UTC)[reply]

Thanks for your inputs. My question was about converting solar 'heat energy' into electricity. As far as I know, photovoltaic cells convert light energy into electricity. Gandalf61 came close to the answer I was expecting. Thermocouples seem to the simplest but they are very inefficient, aren't they ? - WikiCheng | Talk 17:17, 19 May 2011 (UTC)[reply]

While the questions is focussed on the practical side of things, it is also interesting is to compute the maximum theoretical efficiency you can get from solar power. So, we have a black body at temperature T from which we receive photons and the local environment is at temperature Te. The maximum possible efficiency is not given by the Carnot formula. You can see this by computing the entropy of a photon gas. This is most easily done by using the fact that the chemical potential of photons is zero. This implies that the Gibbs energy E - T S + PV is zero. Using that the pressure is 1/3 times the energy density, yields S = 4/3 E/T. Since this is more than E/T, converting this energy to work cannot be done at the Carnot efficiency. Instead, the maximum efficiency is (1 - 4/3 Te/T).

So, what is the physical difference between simply transferring heat from a black body and extracting photons that explains the lower efficiency? Using photons from a black body is equivalent to letting a small box with perfectly reflecting walls inside the black body and fill that with photons, and then bring that outside for use. When the box is brought outside, the photons that filled the volume V occupied by the box will be filled by the other photons in the black body. But this means that an amount of work of P V, with P the radiation pressure, that could have been extracted, will be dissipated inside the black body.

Now, P V = 1/3 E, so we could have obtained and extra 1/3 E from the black body without lowering the entropy of the black body. Now, we assume that we can only carry energy from the black body at temperature T, so the 1/3 E is not avalable as useful work. What we have is 1/3 E at zero entropy and E at a entropy of 4/3 E/T. At best we can preserve the total entropy of 4/3 E/T when the total amount of energy of E + 1/3 E gets combined and attains thermal equilibrium at temperature of T. So the entropy would then be (total energy)/T and thus we obtain the Carnot efficiency. Count Iblis (talk) 18:35, 19 May 2011 (UTC)[reply]

I've not read anything much there except that equation, but according to that one could not get any energy at all if the difference was small which just doesn't sound right to me. Dmcq (talk) 14:50, 20 May 2011 (UTC)[reply]

You won't be able to extract work from the photons, it is not difficult to see why that is the case. In fact, what the formula tells you is that dumping the photons in the enviroment would require some work, and that gives away a hint as to what is going on here. Of course, if you see what is going on, you can argue that in reality, you can work around this by making appropriate assumptions about the environment. However, this doesn't affect the conclusion about what happens when Te << T. Count Iblis (talk) 20:04, 20 May 2011 (UTC)[reply]

Quantitative Analysis and Sex offender registration

Hi. I assume this is a criminology question, and thus belongs in the science section.

Have there been any attempts to subject sex-offender registries to quantitative-analysis techniques e.g. "Static-99"? Have such techniques been found to be useful in helping police decide who on the registry needs the heaviest monitoring, and who can be safely ignored or even removed from the registry?

Have there been any studies into how sex-offender registries can be best used? When a registry starts including all kinds of flotsam and jetsam who pose little or no risk (e.g. soliciting for adult prostitutes, consensual sex between teenagers), it arguably becomes less effective, and wastes police resources. These are obvious examples, but I'm sure there are many other low-risk individuals on registries. Have there been any studies as to applying our knowledge of recidivism factors and rates to sex-offender registration laws? Have any jurisdictions reformed their sex-offender registration laws in line with any such findings (to allow better targeting of police and corrections resources)?

(Unfortunately, sex-offenders make easy political prey. Any attempts to "water down" the laws and make registries more focused on those who pose actual risk would no doubt be exploited by moral panic. People find it hard to accept Napoleon's statement that "he who protects everything protects nothing". But this is merely opinion).

Other than giving Judges discretion in deciding who gets put on the register, have any approaches been tried in fine-tuning registration laws? Who goes on? Who doesn't? For how long? Or is this politically impossible?

Note: I hope this question doesn't raise a storm, or make people accuse me of trolling, or sympathy with child-molesters and rapists. Child molestation and sex crimes have a way of doing that. I'm not making any moral judgments here, or discussing civil-liberties concerns. I'm merely seeking studies on how sex-offender registration laws can be best written and used. And for the sake of this particular question, I'm not focusing on whether such registration schemes should even exist at all. That's a separate issue. Eliyohub (talk) 13:56, 19 May 2011 (UTC)[reply]

My limited knowledge of the UK situation - the Violent and Sex Offender Register - is that the registry is just that; a list, with some details, of offenders. ViSOR has the capacity to hold the results of various sort of risk assessments, such as Offender Assessment System and others. But assessments are not used to fine-tune the membership of the registry. There does not seem to me to be an immediate problem in listing a person because they satisfy entry requirements (such as a conviction for a sexual or violent offence) and then holding, within the record, risk assessments from tools such as Static 99 or OASys. Not least, it is not beyond the competence of users of ViSOR to use the risk information within ViSOR when seeking to draw conclusions about individual or groups of offenders. I'd opine that it is possibly more problematic to list people based only on the output from a tool, rather than based on an event such a conviction. I'm not aware of any moves to try to "fine tune" the membership of such lists. Finally, I note that ViSOR does include a number of individuals who have not been convicted of violent or sexual offences. I'm uncertain of the basis of their listings, and so cannot comment on them one way or anther. --Tagishsimon (talk)

(from the original asker) I'm not sure about ViSOR, but firstly, I don't see how you could "list people based only on the output from a tool" without any conviction. Simple reason being, Static 99 (and presumably OAS) are considered pretty useless at measuring future risk on non-offenders. They were simply not designed with this population in mind. If you wanted to measure the chance of someone who is not known to have sexually offended starting to do so, you would need other tools or methods. And indeed, such a list would be highly problematic. I do know that the U.K. has List 99, and you can get on that for "sexual misconduct" in the course of one's profession or volunteer duties. These individuals do not need to register - they may, however, not work in child-related fields. Eliyohub (talk) 15:08, 19 May 2011 (UTC)[reply]

Another classic example is somebody incorrectly listed for a conviction on "public urination". Part of the problem is having a single list. This inevitably requires "drawing a line", with people endlessly complaining about exactly where the line was drawn and elected officials always tending to put more people on the list, so they can't be accused of being soft on crime. What's needed is different grades. Yes, there will still be lines drawn between each grade, but those won't be as critical as a simple "on the list"/"off the list" line. Also, the name of the lists would need to vary, as being "on the sexual and violent offenders list, grade 9" wouldn't convey that all they did was public urination, so can still be hired.

For comparison, imagine if hurricanes weren't given grades, but we reacted to all the same. Since evacuating each city whenever any hurricane approaches would be an extreme over-reaction, likely nobody would ever evacuate, if they weren't able to distinguish an F1 from an F5. StuRat (talk) 16:59, 19 May 2011 (UTC)[reply]

I was curious how this would be done, so I tracked down the method to [1]. I should note several problematic criteria such as:

Age at release
Ever lived with a lover for >2 years
Number of charges (in addition to convictions) for prior offences.
Any male victims

Now any good civil libertarian should object to different sentences for people of different age, even though unfortunately I know this has become a routine practice in the U.S., and at least this one would favor the old for a change. Likewise the fact that someone has had a live-in relationship should be private rather than a reason for punishment. And of course it should be a bedrock principle that charges not leading to prosecution should not lead to punishment - even though, as I recall, there was some decision that created a loophole in that. And naturally we would like to see a system that treats the rape of women as seriously as the rape of men. So I think there's a strong basis in principle and law to reject the use of Static 99 to decide who is stigmatized as a sex offender. Wnt (talk) 00:56, 20 May 2011 (UTC)[reply]

I think you have the cart before the horse. Measures such as Static 99 and OASys are risk assessment tools used on convicted offenders. The questions in them lead to conclusions about risk based on studies of the re-conviction rates of large cohorts of offenders. Whether or not you like it from a PC point of view, large numbers of charges, or low age at release likely correlate positively with re-offending, and thus are markers of increased risk. Static 99 is not used to "decide who is stigmatized as a sex offender". Your court conviction for rape is the thing that does that. Static 99 assists by indicating - if only on an actuarial basis - the relative risk associated with the individual. And I highlight the actuarial element since that is of interest. The static 99 score or the OASys score indicates you are a member of a class of offenders who have such-and-such a reconviction rate. They do not indicate that you, personally, are likely to reoffend, but merely that you're a member of a group in which, say 68 out of 100 reoffend within five years. --Tagishsimon (talk) 01:40, 20 May 2011 (UTC)[reply]

Well, the OP asked about people being ignored or removed from the registry. I think that would be as inappropriate as giving people different prison terms according to the race of the offender and the statistical likelihood of people of that race reoffending. There are ways in which we just don't want justice to be more efficient; principle matters more. Wnt (talk) 02:00, 20 May 2011 (UTC)[reply]

As courts are not sentencing based on measures of re-offending by ethnic group, you are here in straw man territory. I agree with your first point, somewhat. I tend to think the OP is confusing membership of the list - a Boolean sort of a thing - with risk assessments such as Static 99 which provide an actuarial risk assessment arguably useful in sentence planning. The list, and risk assessment, though complementary, serve different purposes. The OP talks of "When a registry starts including all kinds of flotsam and jetsam who pose little or no risk ... it arguably becomes less effective, and wastes police resources." That is to suppose that a police user of the list would not also avail herself of the previous conviction and risk assessment information within the list. Meanwhile you talk about the importance of principles, and state that "any good civil libertarian should object to different sentences for people of different age". I consider myself a good civil libertarian, and I could easily countenance different sentences based on age, if there was an underlying evidence base to show that recidivism rates are best minimised by such a sentencing policy. The principle, for me, is effectiveness in diminishing reoffending rather than some faux equality of punishment. And, in reality, the principle is the cost-effectiveness of sentences, since the public purse is not unlimited and can dedicate only finite resources to punishment and rehabilitation. How is society best served by wasting resources on offender of class X and skimping on offender of class Y if the evidence base suggests that less resource (i.e. shorter sentences) for X and longer for Y leads to better outcomes (i.e. lowered overall recidivism? --Tagishsimon (talk) 02:26, 20 May 2011 (UTC)[reply]

This would be better placed at the Humanities desk... I think there might be aspects of rule utilitarianism to this, but more specifically the principle of equality under the law. Ethnicity is only one factor controlling recidivism rate - others might be genotype, or whether the defendant once went on the record as a victim of sexual abuse (which some say increases the risk), evidence of psychiatric illness, etc. No matter what factor I can think of that influences the rate, it seems grossly unfair to consider it, except for the simple facts of criminal record which, though part of the Static 99 scoring, are also already taken into account by the judiciary in its own way. Also the purpose of jail is not really to prevent recidivism - for example, we could carry out the much-proposed idea of "sending them all to an island" and, without children present, prevent recidivism entirely, while keeping them a damn sight safer than they are in typical prisons (thus helping the murderers and aggravated assaulters keep their recidivism rate down). I don't see any reason why such a system of internal exile couldn't be introduced, with great savings for the public. I'm not entirely clear on what the purpose of jail is, but it seems to be rooted in some eye-for-eye sense of retribution for a certain type of transgression, which is or should be the same no matter who does it. Wnt (talk) 11:54, 20 May 2011 (UTC)[reply]

(from the OP) Whoa, guys! I'm not asking about sentencing of sex offenders. I'm asking about post-sentence monitoring. I presumed the purpose of sex-offender registries is (or should be) protective, not punitive? The idea (I thought) is to monitor convicted offenders, not "punish" or "stigmatize" them. Therefore, issues of risk are valid, if scientifically proven. These DO include the sex of the victim(s) and the like. I suppose (from this perspective) it's O.K. for the list to include the low-risk "flotsam and jetsam" as long as there is some system for categorizing those on the list by risk level (if only on an actuarial basis). Otherwise, resources are wasted monitoring the low-risk petty offenders. My question is, have any jurisdictions implemented programs to either keep reform their laws to keep obviously low-risk offenders (e.g. public urinators, consensual teenage relationships, soliciting adult prostitutes) off the register (a politically sensitive idea, no matter how logical!), or subject the register to actuarial analysis to give police priorities for the focusing of resources (allowing the low-risk to be pretty much ignored)? Eliyohub (talk) 10:33, 21 May 2011 (UTC)[reply]

To followup, I just saw news of just such an initiative at [2] (if the link fails, search "A faulty computerized risk-assessment program predicted the offenders could be released under the state's non-revocable parole law"). I stand by my opinion of such risk assessment. This could have been done fairly; instead it's a bias-fest inviting people to hack their way out of jail. Wnt (talk) 00:41, 26 May 2011 (UTC)[reply]

Speed of cough

What is the speed of the air from a persons mouth when they cough? I heard somewhere it was about 60mph but the article doesnt seem to say.--92.25.105.208 (talk) 16:42, 19 May 2011 (UTC)[reply]

By golly, that's about right. This study, catchily titled "Flow Field of a Human Cough", gives a maximum speed of 28.8 m/s or 64.4 miles per hour. Clarityfiend (talk) 19:31, 19 May 2011 (UTC)[reply]

Perhaps worth noting this is akin to a muzzle velocity. At a distance of an inch or so from the mouth, turbulence quickly dissipates the energy and drastically reduces forward speed the coughed air. SemanticMantis (talk) 20:14, 19 May 2011 (UTC)[reply]

Fortunately, otherwise we'd face a danger akin to that described in "Man of Steel, Woman of Kleenex". Clarityfiend (talk) 01:32, 20 May 2011 (UTC)[reply]

It's not a fair comparisson, even a modest air rifle has at least ten times the muzzle velocity. Plasmic Physics (talk) 12:23, 20 May 2011 (UTC)[reply]

Warm-blooded versus cold-blooded

I've often wondered why the best attributes of the two can't be combined, to make an animal able to withstand even wider environmental temperature extremes. Specifically, a warm-blooded animal's ability to control it's body temperature would be joined with a cold-blooded animal's ability to continue to function over a wider range of body temperatures. Why hasn't this combo evolved ? Is there some inherent contradiction between these two attributes ? StuRat (talk) 16:43, 19 May 2011 (UTC)[reply]

The combo has in fact evolved -- the example I know of is some members of Xenarthra such as the sloth, but I expect there are others. I don't think it reduces the viable temperature range, though -- for the sloth the function is probably to reduce metabolic demands. Looie496 (talk) 17:04, 19 May 2011 (UTC)[reply]

(ec)Who says it hasn't? See heterothermy. Matt Deres (talk) 17:10, 19 May 2011 (UTC)[reply]

Interesting, but not quite what I had in mind. That's talking about animals that are different temps at different times in the day, or in different parts of the body. What I picture is an animal (let's say a person), whose body tries to maintain a constant temperature, as now, but who can still function normally with a core body temperature of, say 10 degrees more or less than that. If cold-blooded animals can do this, why can't we ? (I concede that a person with a low blood temperature would need to move more slowly, as is true with cold-blooded animals.) StuRat (talk) 19:48, 19 May 2011 (UTC)[reply]

I don't think that could be achieved without making the animal less efficient when operating at its normal temperature. The advantage of being able to operate across a wider temperature range would be fairly small, since extremes of temperature are unusual, so the loss of efficiency probably isn't outweighed by the wide temperature range. --Tango (talk) 20:27, 19 May 2011 (UTC)[reply]

I think it would be quite beneficial. Deserts and arctic/antarctic zones like Greenland and Antarctica, now sparsely populated, might become widely populated. Also, what are the reasons for the lowered efficiency ? StuRat (talk) 21:12, 19 May 2011 (UTC)[reply]

I believe the way existing animals handle wide temperature ranges is to have multiple enzymes for the same reaction that work at different temperatures. That means that, at any given time, some of those enzymes are going to waste. That is inefficient. I don't see why arctic/antarctic zones would be more widely populated - they don't have wider temperature ranges than anywhere else, as far as I know, it's just that they vary between very cold and even colder. Deserts are a more interesting possibility, although the lack of life there is usually due to the lack of water rather than the big temperature changes. There are animals there already that handle the temperature changes by just burying themselves during the extremes. --Tango (talk) 00:50, 20 May 2011 (UTC)[reply]

According to this site, the temperatures extremes recorded in Antarctica are -129°F to +59°F: [3]. Of course, only a few spots there have weather stations, and most of those have only been operational for a relatively short time, so the actual variation is probably more. That range of 188°F is probably more than a similar-sized continent lacking either deserts or an arctic/antarctic region would have (if there were any). StuRat (talk) 01:47, 20 May 2011 (UTC)[reply]

Isn't this a simple matter of water freezing at 0°C? Mammals do fine everywhere on Earth, except were temperatures are too low. The whole point of being mammal is that you exploit an abundance of available food. Higher metabolic rate means that you can be more active to find more food. Using more energy relative to a cold blooded state yields you so much more food that you can pay off that higher energy bill and still have energy left (which allows you to afford energy expensive systems that cold blodded animals cannot afford).

But that requires living in a biosphere where there is plenty of food to find, and ultimately all food is based on photosynthesis. The farther from the equator you get, the less plant life there is and thus the more difficult it gets to be a mammal. At first mammals have an advantage over cold blooded animals, when temperatures are lower, but when there is still enough food to find. But once food becomes scarce, mammals have to hibernate during Winter to survive. Metabolic rate then indeed goes down, but they can't be active. Count Iblis (talk) 02:12, 20 May 2011 (UTC)[reply]

(Responding to the original question) There is a huge advantage in maintaining a constant body temperature. Many of the biochemical reactions involved in metabolism have a very steep temperature dependence -- a change of just a few degrees can double or halve the rate of a reaction. However, the temperature dependence for each reaction is somewhat different from the others. Thus, even a relatively small change in body temperature produces a large variation in relative reaction rates. Designed a reaction network that is robust in the face of such variations is quite a challenge. Thus, holding the core body temperature roughly constant allows for a considerable increase in the complexity of metabolic systems. Looie496 (talk) 04:42, 20 May 2011 (UTC)[reply]

Don't you mean a decrease in the complexity ? Also, I would see your point if warm blooded animals had evolved directly from something that lived in a constant temperature environment, like the bottom of the ocean. But warm-blooded animals evolved from cold-blooded animals, which already had all the mechanisms in place to operate over a wide range of body temperatures. So, why did we lose those attributes, as we gained the ability to control our body temp ? StuRat (talk) 04:54, 20 May 2011 (UTC)[reply]

Agree on "decrease". Having to maintain several different working metabolic pathways - each with its own (highly temperature-sensitive) enzyme(s), plus the extra genes necessary to code for them (which is one reason why amphibians have to have substantially larger genomes that physically more complex humans) - in order to achieve the same metabolic outcome, is in the long run more costly than having only the single pathway (and its genes) best suited to a particular constant internal temperature. When phenotype features become redundant, maintaining them becomes an unnecessary cost, and mutations that damage them are no longer selected against, so they tend to disappear and their once useful genes may become junk DNA, or may mutate further to perform some new and useful function.

[Apologies for the unnecessary complexity of that answer: I didn't have time to evolve a more elegant one!] {The poster formerly known as 87.81.230.195} 90.197.66.60 (talk) 07:40, 20 May 2011 (UTC)[reply]

Well, I did really mean increase. Adding a new mechanism to the system is much easier if it doesn't have to operate across a wide range of temperatures. Concerning the evolution, it is important to realize that no species is absolutely warm-blooded or absolutely cold-blooded. Warm-blooded species always tolerate some range of variation (especially in peripheral tissue); cold-blooded species usually make some effort to thermoregulate. Generally speaking, the more rigorously a species thermoregulates, the easier it is to add a new metabolic mechanism to the system. Looie496 (talk) 16:13, 20 May 2011 (UTC)[reply]

Never mind mammals - some sharks are homeothermic. Roger (talk) 11:23, 20 May 2011 (UTC)[reply]

Sexual reproduction in plants

Hi, I know that all flowering plants can reproduce sexually. Are there any other plants that do this too? Thanks, --T H F S W (T · C · E) 21:02, 19 May 2011 (UTC)[reply]

I thought that pretty much all plants could reproduce sexually (barring things like Navel oranges, which only arise because humans are around to graft them). Certainly most Embryophytes do. Seed plants, of which flowering plants are a subset, can reproduce sexually via seeds. Ferns reproduce sexually with spores. Algae, one of the simplest plants, also can reproduce sexually, I think by spores again. See Alternation of generations for more about the life cycle of plants. Buddy431 (talk) 21:35, 19 May 2011 (UTC)[reply]

You might find the Plant sexuality and Vegetative reproduction articles interesting. Vespine (talk) 22:48, 19 May 2011 (UTC)[reply]

Also see monoicous and anisogamy. ~AH1 ^(discuss!) 00:33, 20 May 2011 (UTC)[reply]

Finding article that cite a particular paper

This is probably an elementary question, so my apologies for that. How would one find which articles cite a particular article as a reference? The article that I wish to find more information about is PMID 20107369. NW (Talk) 22:24, 19 May 2011 (UTC)[reply]

If you were looking for Wikipedia articles linking to a specific Wikipedia article, just pick "What links here" on the left side, under "Toolbox". But, finding which Wikipedia articles link to a specific outside article is trickier. I used the search box at the top to look for both that number and the title, but didn't find either. So, it doesn't look like any Wikipedia article currently references that article. I'm not sure how to check the archives for old versions of Wikipedia articles which might have linked there. StuRat (talk) 22:32, 19 May 2011 (UTC)[reply]

My apologies for being unclear. I was looking for articles published in academic journals that cited that article. NW (Talk) 22:38, 19 May 2011 (UTC)[reply]

Try a Google search ? StuRat (talk) 22:46, 19 May 2011 (UTC)[reply]

More specifically, use Google Scholar. Underneath the brief abstract will be a link that says "Cited by N" (where N is the number of citations). Click that link and it will give you the articles that cite that paper. Your particular article is cited by three other articles. I don't know how comprehensive the tally is, but it will be a good start. --- Medical geneticist (talk) 22:56, 19 May 2011 (UTC)[reply]

Traditionally the way to do this has been using Science Citation Index, though they've tended to have a clunkier interface and are only going to make themselves available to registered academicians permitted access. Wnt (talk) 00:44, 20 May 2011 (UTC)[reply]

The ISI Web of Science is another such indexing service. --Mr.98 (talk) 00:46, 20 May 2011 (UTC)[reply]

Science Citation Index and ISI Web of Science (WoS) are products of the same company, and I believe the latter being more relevant to this question. I just searched WoS for citations of PMID 20107369 (by Shomaker), and there were only two: PMID 21112623 (Frenk et al in The Lancet) and an erratum (doi:10.1097/ACM.0b013e3181dc5007) in Academic Medicine by Shomaker. The Nora ref (one of the 3 that Medical geneticist's Google search retrieves) may not have been indexed by ISI yet. -- Scray (talk) 01:25, 20 May 2011 (UTC)[reply]