0:03 [Music]
0:07 well hi there this is a tiger and this
0:11 is a tiger and this is a tiger and this
0:16 is a tiger and this is a tiger and this
0:20 is a tiger and this is a tiger and this
0:25 is a tiger and this is not a tiger and
0:28 neither is this are all of these the
0:30 same species
0:33 or many species if there are many
0:36 species how many species which ones are
0:40 the same and which ones are different
0:44 and what is a species anyway that last
0:46 question seems like an easy one I think
0:48 that if you ask moderately informed
0:50 people the majority will tell you that a
0:53 species is defined as a group of
0:55 organisms that can breed with one
0:57 another and produce viable offspring
0:59 that themselves can reproduce and this
1:01 is a great definition it's
1:05 straightforward coherent and intuitive
1:07 as always like And subscribe and we hope
1:14 soon but wait this tiger the the first
1:16 one we saw is a wild tiger from
1:20 Southeast Asia and this tiger is a
1:24 captive tiger in North America they will
1:26 never encounter one another let alone
1:29 breed are they the same species or
1:34 different species this tiger is extinct
1:36 as is this one probably we do have a
1:39 whole video about that one but are they
1:43 the same species as this tiger or a
1:45 different species this is a tiger
1:48 whiptail and this closely related lizard
1:50 is a New Mexico whiptail it's a female
1:52 you can tell that it's a female because
1:55 the females have stripes like this one
1:57 and the males don't exist that's right
1:59 the entire species is female they
2:02 reproduce asexually via parthenogenesis
2:05 which means that none of them breed with
2:07 one another is each
2:10 individual therefore a separate species
2:12 this is a tiger salamander and this
2:15 salamander is an entina and so is this
2:18 and so is this and so is this you might
2:20 notice that there is some pretty great
2:24 variation in inas now here's the crazy
2:27 thing tinas live at relatively high
2:31 elevations but not extreme elevations as
2:34 a result 19 populations are found in the
2:36 mountains that encircle California's
2:39 Central Valley all together these 19
2:41 populations form kind of a horseshoe
2:43 around the valley they don't form a
2:45 complete circle because the mountains on
2:48 one side are just a little bit too tall
2:50 for them now here's the thing each
2:52 population is capable of breeding and
2:54 producing viable offspring that
2:56 themselves can reproduce with the
2:59 neighboring population so it is possible
3:01 for beans from one end of the Horseshoe
3:04 to make their way all the way to the
3:06 other end of the Horseshoe but
3:10 individuals from one end can't reproduce
3:13 with individuals from the other end so
3:18 are they one species or many species if
3:21 many how many and why and this is a lion
3:23 it can breed with a tiger and produce a
3:25 viable Offspring called a liger or a
3:28 taigon depending on who was the lady and
3:31 who was the fella well these lion tiger
3:32 hybrids are viable and that they can
3:35 survive just fine but they're sterile
3:38 usually at least males are females can
3:41 potentially reproduce with a male lion
3:45 or a male tiger so are lions and
3:49 tigers the same species or different
3:51 species hopefully by now you are no
3:53 longer as confident that you know what a
3:56 species is as are the moderately
3:58 informed and you have entered the
4:00 uncomfortably uncertain position of the
4:02 highly informed because as comfortable
4:05 as it is to divide life into discrete
4:08 boxes called species it turns out that
4:11 life is an everchanging Continuum and
4:14 finding a way to divide continuous data
4:17 into discrete categories is not always
4:19 easy to do in an objective and intuitive
4:21 manner but we're going to try anyway so
4:23 now that we've lost all sight of what a
4:24 species might
4:28 be let's talk about what a species might
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6:16 the species concept that we discussed
6:19 earlier the top answer in Family Feud is
6:21 called the biological species concept
6:24 like all species Concepts it has
6:26 strengths and weaknesses species
6:28 Concepts that have no strengths are
6:31 called garbage ideas not species
6:32 Concepts and if we had one with no
6:35 weaknesses we would call it the species
6:38 concept but there are enough weaknesses
6:40 with the biological species concept for
6:42 us to recognize that it's difficult to
6:45 apply objectively in some instances like
6:47 with lions and tigers tigers in
6:50 different places or with the salamanders
6:53 and downright impossible in others like
6:55 with fossils and asexual lineages so
6:58 while it can work certainly doesn't
7:00 always work and that is why it isn't the
7:04 species concept so what are the other
7:05 ones what are their strengths and
7:07 weaknesses let's talk about the most
7:10 frequently used species Concepts and if
7:11 you still haven't found one that you
7:12 like maybe we'll revisit this topic in
7:15 the future and let's start with another
7:18 one that is fairly straightforward the
7:20 morphological species concept do you
7:22 remember that fossil tiger well if you
7:25 do you might recall that I have no idea
7:27 if it could breed with any of the other
7:30 Tigers the lion the Jaguar or anything
7:32 else alive today heck I wouldn't even
7:34 know if two identical fossil tigers
7:37 found at the same place at the same time
7:40 with a bunch of babies could breed with
7:42 one another I could find two skeletons
7:45 in the act of mating and I wouldn't know
7:47 if they were able to produce viable
7:49 fertile offspring but I could carefully
7:51 study their skeletons and determine if
7:53 there are significant differences
7:55 between them are their skeletons
7:56 significantly different from those of
7:59 modern tigers or any other living
8:01 organism if they aren't meaningfully
8:03 different I can conclude that they're
8:06 the same species based upon the
8:08 morphological species concept that two
8:10 organisms are the same species if they
8:12 share many unique features and do not
8:14 differ significantly from one another
8:16 and this species concept has many
8:19 strengths it's broadly applicable much
8:21 more broadly applicable even than the
8:23 biological species concept I don't need
8:26 to know anything about reproduction it
8:28 works on asexual lineages extinct
8:30 organisms really anything I can observe
8:33 alive or dead it's basically the gold
8:35 standard of paleontology where
8:37 morphological features may be all that
8:40 we have and yet it's just about as
8:42 intuitive as the biological species concept
8:43 concept
8:48 but it isn't the species concept it has
8:50 many shortcomings for example look at
8:53 these two gorillas they have many
8:55 similarities but they aren't identical
8:57 so how different is two different seems
8:59 pretty subjective I mean who's making
9:01 making that call would you agree with
9:03 their standard and if the two
9:06 morphologies are significantly different
9:08 what's causing that difference these two
9:11 grasshoppers are the same species but
9:13 they don't look the same and why do they
9:16 not look the same because one of them
9:19 grew up in close proximity to other
9:21 Grasshoppers and the other did not these
9:23 grasshoppers have little hairs that if
9:26 bumped above a certain frequency caused
9:28 them to mol into longdistance flying
9:30 locusts instead of a grasshopper that
9:32 tends to stay prettyy much in one place
9:34 they will differ in coloration Wing
9:37 shape and size muscle composition fat
9:39 storage as well as Behavior but not
9:42 because their genes are different but
9:43 because their environment was different
9:46 triggering a different set of genes to
9:49 be activated this is called phenotypic
9:51 plasticity two grasshoppers with the
9:53 same genetics can develop to totally
9:56 different morphologies and their
9:58 morphology will not play a significant
10:00 role in determining which morphology
10:02 their offspring present and don't get me
10:05 started on green anacondas as we will
10:06 discuss next week in our featurelength
10:09 documentary about all of the boa species
10:12 we just discovered a new species of
10:14 green anaconda but the reason that we
10:17 didn't realized that there were two
10:19 species of green anacondas sooner was because
10:21 because
10:23 morphologically the two species are
10:25 nearly identical it wasn't Until We
10:27 examined their DNA that we learned that
10:29 the two species are reproductive
10:32 isolated from one another and highly
10:34 different genetically but
10:36 morphologically that's not the case
10:38 these two butterflies look identical too
10:40 they live in the same place but they
10:43 never mate why because under ultraviolet
10:45 light they look nothing alike and the
10:48 butterflies can see that but it took us
10:51 centuries to notice other nearly
10:53 identical organisms may not mate because
10:55 they use different pheromones or calls
10:57 or other things that are difficult or
11:00 impossible to observe morphologically
11:02 not to mention convergent evolution
11:05 where two highly unrelated organisms may
11:06 end up with a nearly identical
11:09 morphology and gosh look at these two
11:12 animals one is twice the size of the
11:14 other with a very different skull
11:16 morphology but they're both gorillas
11:18 just different Sexes this is called
11:20 sexual dimorphism which by the
11:22 morphological species concept could
11:25 easily cause us to assign each sex
11:27 erroneously to a different species so
11:29 it's not perfect okay I'm going to
11:32 preface this next one by telling you
11:34 that my Master's research was in
11:36 evolutionary ecology so I'm a published
11:38 ecologist but the ecological species
11:41 concept is in my opinion the most
11:43 garbage of the four most widely used
11:45 species Concepts I should also tell you
11:47 that ecology meetings make me question
11:49 my reason for being and evolution
11:52 meetings remind me exactly why I love
11:54 biology so much but the ecological
11:56 species concept considers organisms to
11:58 be the same species if they utilize the
12:01 same basic set of resources in the
12:03 environment the same ecological niche
12:06 which is historically the only correct
12:07 pronunciation of the word niche in
12:11 English and it's certainly a correct
12:12 English pronunciation today but the
12:15 ecological species concept defines a
12:18 species essentially by its Niche and the
12:20 adaptations that it has to utilize those
12:23 resources which is really about all that
12:25 keeps the II from being a woodpecker
12:27 according to the ecological species
12:28 concept and it also kind of plays into
12:31 this stereotype about ecologists that if
12:33 you go on a walk with an ecologist and
12:35 point to a plant and ask what it is
12:38 they'll say looks like a C4 grass
12:40 ecologists don't care what an organism
12:43 is they just care what it does in the
12:45 environment they don't care that new
12:47 world and old world vultures are not
12:50 closely related they perform the same
12:52 basic function in the environment so
12:54 they're the same thing and if an
12:56 organism's place in the Ecology of a
12:58 region is all that you care to know
13:00 about it then the ecological species
13:03 concept works just fine it works for any
13:05 organism about which you have
13:07 considerable ecological data but if you
13:10 care about almost anything else then
13:12 you're going to need a different species
13:13 concept not to mention other weaknesses
13:16 such as the fact that no two niches are
13:18 exactly the same and how similar is
13:20 similar enough what if the environment
13:22 changes and their Niche with it what
13:24 about generalists that lack a highly
13:26 specialized Niche what if you don't know
13:29 too much about its exact Niche and more
13:31 there's more but right now I want to
13:34 talk about my personal favorite species
13:37 concept and don't act too surprised the
13:39 philogenetic species concept because I
13:42 think that when we're talking about a
13:44 species we're talking about a group of
13:47 organisms with a unique recent
13:49 evolutionary history and philogenetic
13:52 Analysis unlike ecological analysis
13:55 teaches us a tremendous amount about
13:57 organisms that we didn't know when we
13:59 classified them it is Mass massively
14:02 predictive unlike basically all other
14:04 organizational systems that we have ever
14:07 devised for organisms for example I
14:09 could find an organism that has never
14:12 been seen by anyone before if I had
14:14 nothing but a genetic sample I could
14:17 determine its likely location in the
14:18 philogyny of living organisms it could
14:20 even be the case that I've never even
14:24 seen this organism myself and I have no
14:27 preconceived notions about what it is
14:29 like what it looks like or how it acts
14:31 but now all of a sudden because of phog
14:33 gentics I know that it's more closely
14:36 related to will than it is to Jason
14:37 knowing nothing more than that about it
14:39 but given what you know about Will and
14:41 Jason and their position in the
14:43 philogyny of life I bet that you can
14:45 make all sorts of accurate predictions
14:48 about this previously unknown organism
14:51 so philogenetic analysis rocks but how
14:53 do I use it to Define a species well in
14:55 a nutshell a philogenetic species is a
14:57 group of organisms that share unique
15:00 common ancestry and are genetically
15:02 similar within predetermined thresholds
15:05 as to insinuate recent if not current
15:08 gene flow is occurring within the group
15:11 but not with other groups basically each
15:14 tip of a philogyny is a unique species
15:16 at least if you include all of their
15:18 close relatives on that philogyny now if
15:21 you ask me the biggest downside to the
15:23 philogenetic species concept is simply
15:25 that philogyny is somewhat foreign to
15:27 most people the same people that
15:29 understand reproductive isolation unique
15:31 morphology and ecological niches may not
15:34 really understand what phog gentics is
15:36 how it works or why it's so powerful of
15:39 course my solution to this problem is
15:41 just to try my darnest to explain
15:43 phylogenetics to the world but it has a
15:46 ton of strengths for one thing it can be
15:48 applied based on any source of data that
15:50 can be used to generate a philogyny this
15:52 includes fossils morphology and
15:54 molecular analysis and often a
15:56 combination of these distinct sources of
15:59 data it works for living organisms
16:01 extinct organisms sexually reproducing
16:03 organisms and asexually reproducing
16:05 organisms the horizontal Gene transfer
16:07 in bacteria can throw a wrench and
16:10 things and it's far more objective and
16:13 free of bias than any other species
16:15 Concepts that we've discussed as long as
16:17 you clearly State your thresholds for
16:20 what constitutes a unique species any
16:22 researcher can evaluate your data set
16:24 and draw the same conclusions it isn't
16:26 based on what features the researcher
16:29 deems to be important but on actual
16:32 evolutionary history and diversification
16:33 from other groups because at the end of
16:36 the day species are a real thing and
16:38 phylogenetics is the best system we've
16:40 yet derived from modeling the real
16:42 relationships and history of organisms
16:45 on this planet that said it isn't
16:47 without it shortcomings for one thing it
16:49 generally requires large amounts of data
16:51 that can be expensive to collect and
16:52 difficult to analyze and while it is
16:54 super effective for organisms for which
16:56 we have extensive morphological and
16:59 genetic data it can be much harder to
17:01 apply to organisms known only from
17:03 limited and often incomplete fossil
17:05 evidence and knowing exactly where to
17:07 draw the line between species that can
17:09 still be difficult it's easy to
17:11 oversplit groups or have disagreements
17:14 about how much difference is Meaningful and
17:14 and
17:17 so you may walk away from this video still
17:18 still
17:20 wondering what's a
17:24 species and that's okay cuz nobody
17:27 really knows sorry as always like And
17:30 subscribe and we to see you real soon
17:31 and I just want to say a special thank
17:33 you to all of these people a video like
17:36 this is one that you know we know is
17:39 valuable but may not get that many views
17:42 and it's because of these people that we
17:43 can make content like this and we'll
17:45 continue to do so in the future and if
17:48 you want to support more videos of this
17:50 nature going forward please consider
17:52 checking out our patreon I could find
17:55 two skeletons in the act of mating and I
17:56 wouldn't know if they were able to
18:07 thank you CL
18:10 yes these are just the most broadly used
18:12 if they come from the same
18:14 kind that well that would be a big one
18:17 there you go that's uh baraminology is
18:23 what that's called baram baramin bman
18:25 baraminology and uh I can discuss that
18:27 one I understand that way better than
18:30 most creationists do okay I really do
18:35 like like you know people all the time
18:37 are asking for a definition of what a
18:39 created kind is I'm glad you asked this
18:41 question because this is a this is this
18:43 makes your patreon extra's video totally worth
18:51 it one day yeah just don't suck it up
18:55 too much it'll go straight in your LS
18:58 yeah flies out and you then you'll cough
19:01 it up and you won't have a meal
