how could we tell if two populations represent different species?
411955
If the two different populations are unable to mate and create fertile offspring, then they are different species.
870300
Measuring chromosomes as a whole isn't a very good way of determining relationships between species. Although humans have 46 chromosomes (23 pairs) versus chimps' 48 (24 pairs), it's clear from looking at the structure of the chromosomes themselves that one of the human ones is composed of two of the chimps ones that have joined together. We can even see the end markers of the chimps genes in the middle of our joined one.\n\nIn terms of overall genetic difference between humans and chimps, it depends on exactly how you measure it but it's between 1 and 4 per cent. \n\nUnfortunately the answers given earlier about pigs being closer aren't accurate. They share large-scale physiological similarities, which is why heart ops may be possible, but this has nothing to do with DNA.\n\nA good reference for all this stuff is the Talk Origins archive at http://www.talkorigins.org
10461
There is no difference in spots. The male and female are hard to tell apart other than the female is slightly larger. Otherwise you have to use a microscope.
808019
you can pluck a feather and have genetic testing done, which is the only way to know for absolutely sure, but adult plumage is a very good indicator. so just be patient and youll be suprised
560885
You would think that the pecking itself or the usage pattern of (as it were) of the pecker would be enough to identify not only the sub-species but the individual, however, there is not scientific evidence to show that this is the case. \n\nIt is possible through the use of photgraphs of the peckers to identfy even beyond the sub-species to the invidual (there are a few famous cases of this).
808145
I think you might have a paper-worthy idea here. Not sure, like the first poster, of the amount of support you'll find to back your theory up, but I do find the comparison appealing, and I've never thought of that before!\n\nHope you can draw the similarities without too much painful, fruitless research! Good luck!
582344
Yes there are.  They have been here for thousands of years.  Some come and go, others stay.  Two such species look almost exactly like us because they are believed to be the ones who actually "created" us.  You should read the Earth Chronicles written by a group of archaeologists.  It  better explains it than I can in such a short space.  There are 7 books total beginning with "The 12th Planet" by Zecharia Sitchen.
28768
Here is a great website for that sort of research. It has a taxonomic chart with hyperlinks to information, pictures, sounds, and specimens. There are more than a dozen phylums of 'worms' represented with many photos to help with identification. \n\nhttp://animaldiversity.ummz.umich.edu/site/accounts/classification/Animalia.html
78253
Here are some pictures that can show you some differences. Just use your eyes. The first is a cow, the second a woman
844547
THE NICHE CONCEPT & ETHNIC DIVERSITY\n\n\nIntro\n\nOne of the striking facts about contemporary society, and indeed of much of recorded history, is the division of the human species into distinct ethnic groups, whose interrelations are sometimes antagonistic and sometimes mutualistic\n\nWhile there are many interesting ways social scientists analyze this phenomenon, ecological theory may provide some additional insights\n\nThis lecture approaches this topic as follows:\n\n1. What is ecological niche theory? (brief summary)\n2. How can we apply this theory to human ethnic diversity?\n3. Discussion of Swat case (Barth reading)\n\nCharacter displacement refers to the phenomenon where differences among similar species whose distributions overlap geographically are accentuated in regions where the species co-occur but are minimized or lost where the species’ distributions do not overlap. This pattern results from evolutionary change driven by competition among species for a limited resource (e.g. food). The rationale for character displacement stems from the competitive exclusion principle, also called Gause's Law, which contends that to coexist in a stable environment two competing species must differ in their respective ecological niche; without differentiation, one species will eliminate or exclude the other through competition.
377057
These differences are called variations and they were one of the key observations made by Darwin that helped him produce his theory of evolution.\n\nWithout these naturally occuring differences between individuals within a species, the species would be more apt to suffer extinction if its environment should suddenly change.\n\nIf a change in a species' environment should happen, these variations provide a greater possibility that some portion of the population is likely to be able to survive it.\n\nGreat question.
479338
Each of these common names refers to more than one species (sometimes several) and the extant or available data for each one may differ, therefore I suggest you look at this site: \nhttp://www.demogr.mpg.de/cgi-bin/longevityrecords/entry.plx\n\nwhere you can find well-recorded lifespan data for many species.  \nGood luck :-)
1079080
no they are a different species
861146
different kinds of people, mixed kinds of people with different temperaments, colors, etc
98550
Those are the charactistics by which a species is defined by taxonomists, the people who classify plants and animals.\n\nGenerally, a species is defined by those characteristics that the entire species has, not those that vary greatly among individuals.  They must also be characteristics that are different from other species.  So, for example, you might count the number of bones in a particular body part, or the position of the eyes relative to the rest of the face, or whatever.  Sometimes it is a behavior characteristic, but usually it is one shaped by a physical characteristic.  \n\nTry it on dogs, to see for yourself.  There are many breeds of dogs, and their hair, their shape and size, etc., vary greatly.  You can't use those.  They have four legs and a tail, but so do lots of animals other than dogs.  But dogs have a unique ventilation system, in that instead of sweating all over, they hang out their tongues and pant to get rid of excess moisture.  I am not enough of a taxonomist to give you all the details, but you could look them up.  Be prepared to discover, as I did when I read a book all about dogs, that several animals which have different names are also dogs in the scientific sense of being members of the species.  (Dang!  My cheap new dictionary does not give the Latin names.)
925661
What a fascinating question.  I'm no geneticist, so take my words with such forewarning.\n\nI think if one were to closely look at human evolution, one would find a different degree in evolutionary history.  \n\nHow does one best differentiate the degree between races? That is not so debatable. Most scientist, today, do not recognize race.\n\nOnce upon a time they did it with "discernible" qualities based on "eyeball" measurements.  \n\nSkin color demonstrates this old fashioned method quite well.  And still, it counts for something, despite its inaccuracy.  \n\nOur world wide communication has increased, and people of different skin colors have discussed (and seem to agree) that human nature seems to be same, no matter where we are.  \n\nThere are good and bad people out there, despite the preponderance of race you live amongst.  \n\nThis could be comforting in the sense that no race is better than the other,  or discomforting in the sense that there will always be "different" people out there, no matter where you live.\n\nThe debate on "degree" of human evolution, in my humble opinion, should be viewed in light of the environment in which the human is required to adapt to.\n\nYes the degree of evolution among Humans is different, and so is the environment in which Humans live in.\n\nA current trend for scientist is to observe closely the Human genome and how it may or may not change within different situations.\n\nI suppose the phrase of "genetic adaptation" is appropriate to use here.\n\nSpecifically, I'm thinking of the adaptation of the Human gene 'hemoglobin' has gone through, in an attempt allow Humans to survive.  \n\nIn some environments Plasmodium parasitism has changed the degree of evolution by favoring the level of genetic adaptation in those with an altered (or evolved?) globin genes.  Having those altered genes in an an environment where Plasmodium is prevalent is a plus. (Please google "genes, hemoglobin, parasites, Africa).\n\nHaving those altered globin genes in a part of the world where Plasmodium is NOT prevalent might mark you as different.  Just like skin color.\n\nI sometimes wonder if race might better be described by historic ability to survive genetic insults.  \n\nDo you have an Alu element in NM_94327343?\n\nOr better yet, are you evolving differently because your Alu element at NM_94327343 is no longer methylated?\n\nTake home points: (1) Skin color is not a current basis of race.  (2) Environment suggestively role-plays in our differences during Human evolution.  (3) According to experts every time the sperm and egg "dance", there is an opportunity for a degree for evolution (Sorry I didn't expound on this in my answer, but it can be googled.  Try 'XX', 'XY', 'meiosis' as a point in a good direction).  (4) There are probably other reasons that Humans evolve to different degrees, and they might be unmeasurable at the moment. However, current standard genetic measures on "old" populations seems to say "yes, there are degrees of difference in human evolution".  \n\nI had a lot of fun thinking about your question.  I can't wait to see your other replies regarding this topic.  Don't forget to pass on your good Karma!
377414
some can, depends on the species