Allopatric and sympatric speciation | Biology | Khan Academy
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Allopatric and sympatric speciation
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8:20 for polyploidy
8:03 was a good start for me.
Thanks
Good explanation. Thanx.
It's amazing how well you write with mouse
quqquqqqu he doesn’t. You can connect a tablet to the computer and write on the tablet. There’s a pen you use on the tablet!
Dh
he is not!
Great video. Good explanation
thanks budy !
Wonderful lecture 😀
Thanks
thank you, this was very helpful!
Did the previous "evidence for evolution" get taken down?
yes i saw the video!!
great video
U r really good man..I like ur xplaination n writing technique
I was wondering do you really need a tetraploid to create a triploid or can it be just one plant with an error mixing with a haploid that can make a triploid
Yes! This should also be possible in theory. It can also be a regular diploid plant having an error in meiosis and this would form a triploid as well!
7:57
You should have taken the example of the wheat to explain this. More over you should explain endoreduplication to show how the allopolyploid species arise.
Shrkomalumae
bs mjaa aa giyo... 🙏 🙏 🙏 🙏
So a random event kickstarts speciation causing a pre zygotic form of isolation to develop, which carries the subgroups of one species from the random event into fully speciating into different species, which by then would have made the species genetically different enough to be post zygotically isolated, where any attempt at producing viable fertile offspring would fail, while during pre zygotic isolation / during speciation, at some points the subgroups can be different enough to be called different species but not fully speciated that they can not have viable, fertile offspring? Dang... thanks KHAN ACADEMY
Thanks for the help, I have an exam tomorrow. lol
Is it possible that a human subgroup that consistently vegan or meat eater for thousands of years would eventually form a new species? If yes, how long would it take the speciation to occur?
... start eating from now... lets see how long it takes to occur speciation 😂😂☺️
In terms of the two types of squirrels, could the difference in geography from the two sides of the canyon really be sufficient in diversifying the two's genes to the point where they were no longer compatible in producing any fertile offspring? The idea seems cloudy to me on this one, on how life on either side of the canyon could be drastically different.
DNA mutates over time, yous is mutating right now (slowly). Over subsequent generations, enough diversity in mutated genes could arise to prohibit genetic recombination during zygote formation.
Isa Faghihi
If that is what the examiner wants to hear... Then we shall. 💂
6 years is a long time to wait for an actual answer, but here it is, from a biologist.
Both sides of the canyon are basically similar in ecology (sure, there could be small differences, but essentially a squirrel on one side would do just fine on the other side IF it could get there). The divergence that leads to speciation in the squirrels is not because they would adapt to different conditions, instead it is the non-adaptive evolutionary mechanisms of mutation and drift that will cause these squirrels to speciate.
Imagine a game of telephone being played where the original message is sent split from the starting player to both the person to the left and right. Eventually the messages will reach the person on the other side of the circle, where they get to hear 2 versions of the measage from both paths. In most games not only is the original message sent now changed, but both paths are ALSO different from each other (having a separate history of accumulating changes in the message). In this way we can understand how genetic differences accumulate over time independently in 2 populations of squirrels separated by the canyon. While both squirrels started as the same species (read: message) once split by a barrier like the canyon, each population can no longer reproduce with individuals on the other side (read: the 2 separate telephone paths) over time genetic changes through mutation, and change frequency changes due to drift will arise and cause each population to evolve (read: the message being passed from person to person) now when we compare the squirrels on each side of the canyon we find that they can no longer reproduce even if they are brought together (read: the last person who gets both messages and can see how different each are to one another and the original message). Because the squirrels are now genetically incompatible we would classify them each as a separate species.
Can any one tell me the difference between reproductive isolation in sympatric speciation and allopatric speciation?
The molecular mechanisms behind the reproductive isolations are the same, and it's that they have became too genetically different to produce fertile offspring. But when you are talking in relation to "allopatric", it means that they turned reproductive isolated while (and likely faster because) they were physically isolated. Sympatric just means they still lived side by side when turning reproductive isolated.
Idk if this helps like 4 years lataer 😂, but reproductive isolation basically means 1 species that cannot intervreed anymore. Now this can be due to geographic seperation or other reasons. So therefore it is part of allopatric speciation.
+Khan Academy So how do some modern peoples' genomes contain up to 3% Neanderthal DNA? Wouldn't that have to mean that at some point a Homo sapiens and a Neanderthal would have mated to produce a fertile offspring, which was then able to further mate with other H. sapiens? If so, doesn't that question the interbreeding definition of 'species'?
Every definition of species has some kind of special case that goes against it. It's is difficult thing to pin down.
+RCRhythms He asked a perfectly good question, if you can't accept that people have the right to ask questions without being told to stop studying the subject, then perhaps you should create a field of science where you are the only acceptable authority.
+RCRhythms Did it take you a long time to formulate this reply? Must have been very taxing for your brain.
This is why there are different criterion of identifying species. What you are talking about is biological species concept. Other ways of identifying species are morphological species concept (based on distinct physical features), ecological concept (based on the resources a population consumes and its predators. It also enforces the idea of natural selection) and phylogenetic species concept (using the tree of life to find the smallest monophyletic group). Also, because of hybradization the definition of biological species concept has been changed to "species as group of genotypes that remain distinct despite potential or actual hybridization". Hope that answers your question
There are exeptions in this rule, though it does mostly hold true. One example could be the liger, Ligon, zonkey, or other non fertile off spring of species.
Why is not a simple gene expression? Why is it evolution? If you can interbread the species it means that you are interbreading variations of the same species.
You can still try to create new variations of dogs... It will still be dogs and not directional selection that is evolution in one direction. As we learn in school.
Does this have any epigene involved in this?
One of the definitions of species is that they are sexually isolated and therefore can not interred (have fertile offspring, hybrids do not count)
Dogs have a many different races but are one species, thus can interbreed.
@@maeve7038 exactly. we have different *breeds* of dogs, but not different *species*. this is even better showcased by the fact that wolves can still produce fertile offspring with dogs.
7:35 so.......... when these species begin to diverge, does a common ancestor still exist? If so, who can it breed with?
Theoretically yes! There might be a generation that could interbreed with both of the species that still exists (due to having similar enough genes). Yet overall the two species at this point in time will no longer be able to interbreed
I don't get how these two examples of speciation fit into the larger basic phenomenon of speciation
They are both ways that speciation can occur. Think of it like Speciation is like saying I have a pen. And these types are describing it more like the color
Turkish subtitles?
i have to say i am disappointed that you didn't mention anything about how a tetraploid becomes a hexaploid.
The explanation of the squirrels is not correct. They separated only about 10,000 years ago and the Grand Canyon (which started about six millions years ago) was already an insurmountable barrier by then. It is not like it suddenly appeared in the past few thousand years. More likely is that the original single population lived elsewhere upstream where it was possible to cross the river. The population moved southwards and now the canyon was a barrier that stopped gene flow and led to speciation. The Grand Canyon is a barrier, but the forming of the canyon is NOT what separated this population of squirrels.
I kinda think he is just trying to make a point on how Allopatric speciation works, correct me if I am wrong.
You don't actually explain how speciation happens....
Different video
And you don't know how to properly use an ellipsis.
unless you want the specific genetic reasons, yes he does
so you wanna tell me that plants reproduce using sperm and egg cells😂
yes