Wikipedia:Reference desk/Archives/Science/2015 May 31

= May 31 =

How many times has sex evolved?
How many times has sex evolved? For example, did it evolve independently in plants and in animals? Please use simple language as I am not a biologist. I suppose the answer will depend on what sex is, and the various stages of its development? 82.31.133.165 (talk) 08:14, 31 May 2015 (UTC)


 * As far as we know, once. See evolution of sexual reproduction.  Dragons flight (talk) 08:37, 31 May 2015 (UTC)


 * (EC) Unsurprisingly we have an article Evolution of sexual reproduction. While it's not always that simple, some parts should be understandable particularly "All sexually reproducing eukaryotic organisms derive from a common ancestor which was a single celled species" which seems to answer the basic question. If you have follow up questions from the parts of our article you don't understand, you should clarify what they are. Nil Einne (talk) 08:38, 31 May 2015 (UTC)


 * Agreed. However, there are some species which can reproduce either sexually or asexually. This is more common in plants, but some animals can do either, too.  So, in those cases, the species may "evolve" to either trigger those genes for sexual or asexual reproduction, depending on conditions (a lack of genetically diverse mates would tend to favor asexuality).  This change could also be triggered within a single individual, in which case it's not evolution, but adaptation. StuRat (talk) 15:57, 31 May 2015 (UTC)


 * Mitosis (simple cell division) is the basis for asexual reproduction, whether that be the simple splitting of one cell into two, or the splitting away of two halves of a worm, or medusae from a polyp in the cnidaria, or the dropping of clones by certain plants that produce rooted runners, etc.


 * Sexual reproduction occurs when a diploid organism or some of its cells undergoes meiosis, forming haploid gametes (almost always eggs and sperm) which then recombine, producing a new organism with its own unique genome.


 * Meiosis has only evolved once. Now the details of sex between animals, the mosses and their kin, versus higher plants and their complicated systems of pollenization, the Fungi, and the other eukaryote kingdom including the various types of algae vary quite extraordinarily. μηδείς (talk) 18:50, 31 May 2015 (UTC)


 * More times than you can imagine. -- Jayron 32 20:45, 31 May 2015 (UTC)

Are amphetamines proper a substituted amphetamine?
The article about substituted amphetamines claims that "Examples of substituted amphetamines are amphetamine (itself), methamphetamine, ephedrine, cathinone, MDMA ("ecstasy"), and DOM ("STP")." However, it sounds logical to me to not count amphetamine itself as a substituted amphetamine, since that's like saying it is a derivative of itself. Is the article using a standard definition? --Yppieyei (talk) 13:49, 31 May 2015 (UTC)


 * In general, when you see a -R in a chemical formula, -H is an option. I would say in a substituted compound, a substituent can be hydrogen.  But this is the sort of thing where I can picture opinions going more than one way. Wnt (talk) 16:22, 31 May 2015 (UTC)


 * I think you're concentrating too much on what the words mean and missing the point that the term isn't being used the way a simple intepretation of the words may suggest. If you read substituted amphetamines and amphetamine carefully, the point seems to be that substituted amphetamines is a class of compounds of which amphetamine (alpha‑methylphenethylamine) can be considered the parent. It makes sense to consider this class of compounds, including alpha‑methylphenethylamine together and for various reasons substituted amphetamines is the name for the class of compounds. It doesn't make so much sense to consider just the substituted ones without the "parent". The name may be a bit confusing, but the alternative seems to be just calling them amphetamines but that can be confusing given the name amphetamine is often used to refer to alpha‑methylphenethylamine. If you're still confused, try removing the word substituted from the term or just come up with your own term to refer to the class of compounds and perhaps it'll make more sense. Nil Einne (talk) 17:25, 31 May 2015 (UTC)