Phylogenetic Mysteries: Crash Course Zoology #12 - Free Educational videos for Students in K-12

Phylogenetic Mysteries: Crash Course Zoology #12 - By CrashCourse

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00:0-1	you might not know this about me , but I
00:01	adore puzzles . So I guess my career makes sense
00:05	. And sociology is like one big wonderful jigsaw puzzle
00:09	. Well except that there are no helpful edge pieces
00:13	and lots of pieces can fit in more than one
00:15	place . Oh and we don't have the picture on
00:18	the box as a guide towards the right answer .
00:21	Just some blurry snapshots of different sections from fossils .
00:25	It's fun today . In 2021 we've gotten pretty far
00:29	in solving the zoology puzzle and have a general idea
00:32	of what the medicine family tree looks like , but
00:35	it's not perfect . Some species were and probably still
00:40	are misidentified and there are a lot of gaps and
00:43	missing details . But that's part of what makes psychology
00:46	so thrilling . All the times when evolution has stumped
00:50	or surprised us . The mysteries were still trying to
00:54	solve all of the animals that defy our human brains
00:57	and refused to be put in a neat little box
01:00	labeled carnivore , a or Parisot de castilla or whatever
01:04	. There's so much we have to learn so grab
01:06	some fossils . Fire up the DNA sequence er and
01:09	bring your best hypotheses . It's time to solve some
01:13	file a genetic mysteries . I'm Ray Wynne Grant and
01:16	this is crash course zoology . Yeah . Mhm .
01:27	You might remember from our first episode that fill a
01:30	chinese or file a genetic trees are diagrams that scientists
01:34	use to describe the evolutionary relationships between different animals ,
01:39	but they can also show where there are gaps in
01:41	what we know . Like . There are lots of
01:44	cases where we don't know or only very recently found
01:47	out exactly how a group of animals with a common
01:50	ancestor or clade fits on the Meadows . Oh and
01:53	file a genie . We call these file a genetic
01:56	mysteries . Animals whose traits could place them in multiple
02:00	groups or in groups that aren't actually related to each
02:03	other . And studying and solving file a genetic mysteries
02:07	tells us not just about that particular animals evolutionary history
02:12	, but also about how we've understood and studied animals
02:15	in the past . So being a zoologist can be
02:18	like being a detective , we get pieces of evidence
02:21	like what an animal looks like or what genes it
02:24	has and then have to figure out the series of
02:27	evolutionary events that explains that evidence . But we have
02:32	to be really crafty like Sherlock Holmes level , crafty
02:36	because that evidence isn't always super reliable . Lots ,
02:40	maybe most animals have wildly different body shapes and lifestyles
02:44	from their larval form early in their lives to their
02:47	adult form . And it can be really hard to
02:50	match the two if there aren't a lot of opportunities
02:53	to observe its whole life cycle . Like maybe that
02:56	animal is hard to find in the wild or maybe
02:58	it can't be kept in captivity . These are called
03:01	within lifetime . File a genetic mysteries and one of
03:05	the most enduring examples of baby animals going undercover and
03:09	fooling zoologists is the case of the missing baby eels
03:14	. Let's go to the thought , but people have
03:16	been catching and eating eels for a long time .
03:19	Like back in medieval England , monks often paid their
03:23	landlords with eels , which is very on brand for
03:26	months . Eels were church approved because at the time
03:30	no one had ever seen an eel engage in the
03:32	type of scandalous carnal relations that happened when animals make
03:37	other animals . Instead . Zoologist thought they formed from
03:42	mud and rain water or that adult eels just popped
03:45	out of other eel looking animals like hell pouts and
03:48	this eel mystery went on for a long time .
03:52	Even famous psychologist Sigmund Freud got involved dissecting hundreds of
03:57	eels in the spring of 1876 , trying to find
04:00	their gammy producing organs to prove eels used sexual reproduction
04:05	, but the baby eels had been there all along
04:08	. They were tiny , transparent flatfish called Leptis syphilis
04:12	. A decade after Freud's futile attempts , sociologists managed
04:16	to grow some captive Leptis syphilis into juvenile eels and
04:21	others observed the same thing in the wild . The
04:24	case of the missing baby heels was solved to be
04:27	fair , Eels have a really complicated life cycle with
04:31	five forms that look and act so different . It's
04:34	pretty easy to mistake them as separate species . Plus
04:37	eels move around a lot so you don't see babies
04:41	and adults together . It wasn't until 1904 that we
04:45	figured out European Eels breed in the Sargasso Sea thousands
04:49	of miles from their adult homes . Thanks about bubble
04:53	eels are just one example of an animal that goes
04:56	through big changes and lives in unknown places as part
05:00	of their life cycle , this type of knowledge gap
05:03	is really common in ocean living creatures because the ocean
05:06	is so big , it's difficult to not only know
05:09	how well the populations are doing but also how to
05:13	better conserve them for future generations , but for the
05:16	eels at least the case is closed , which brings
05:20	us to across sexes file a genetic mysteries with some
05:25	animals . The differences aren't so much due to age
05:28	, but sex Sculley and molder , cagney and lacey
05:32	. Agent K . And Agent J . Detective Media
05:35	loves to have two very different people work the same
05:39	case for drama , but at least they're both clearly
05:43	people . Some animal pairs are so different that they
05:47	don't even seem to be part of the same species
05:49	. Sexual demort is um is one . Different sexes
05:52	of the same species have physical differences beyond what gambits
05:56	they make , or sex organs they have . Sometimes
05:59	it's straightforward , like the female being much larger or
06:02	the male being more brightly colored , and sometimes the
06:05	differences between sexes aren't so much in how they look
06:08	, but how they act and behave , which can
06:11	lead to one sex being a lot less well known
06:14	than the other . Like in the case of the
06:16	lonely spiders , subtitle , Eight legs , but only
06:20	one sex of the 46,000 species of spiders described so
06:25	far . Almost 50% of them are known based on
06:28	a single sex , probably because one sex tends to
06:32	get itself into situations where it'll get scooped up by
06:35	zoologist , like wandering around looking for a mate .
06:38	And when we finally do get a specimen of a
06:41	different sex , it can totally change our understanding of
06:44	a species like in Seoul . A few gits aka
06:47	camel spiders , some species have females that are a
06:51	darker color , have different shaped mouth parts and differently
06:54	arranged hairs than males . They look so different that
06:58	they were described as a separate species for years until
07:01	a group of researchers from Iran put things together .
07:04	Another case closed beyond developmental or sexual diversity in animal
07:09	form . Another frequent cause of file a genetic mysteries
07:13	is that some animals are just so bizarre compared to
07:17	everything else we've seen before . Like sometimes a behavior
07:20	and adaptation is just so amazing that early zoologists Tikrit
07:25	, it couldn't have possibly evolved more than once so
07:28	that all animals with that trait must be related .
07:32	But as we've seen several times in this course ,
07:34	convergent evolution happens all the time even for fairly complex
07:39	traits . One example is termites which are you social
07:43	and live in mounds with a reproductive queen and non
07:46	reproductive soldiers , workers , and other highly specialized roles
07:50	. For a long time , they were grouped alongside
07:53	ants and bees in the order Hyman Abdala . Because
07:56	you sociology requires so many coordinated changes in an animal's
08:01	body and behavior That early zoologists figured it probably only
08:05	evolved once , but starting in the 1930s , bits
08:08	of evidence suggested termites weren't quite like ants or bees
08:13	. They had different microorganisms in their guts and baby
08:16	termites look a lot like a very different insect .
08:19	By 2008 , genetic evidence confirmed that termites weren't closely
08:24	related to bees or ants at all . And we're
08:26	actually highly social cockroaches . Re categorizing the taxonomy of
08:31	termites really brought into question the idea that a trade
08:34	could be too complicated to evolve more than once .
08:37	Amazing . What evolution can do with a few 100
08:40	million years to experiment , even if everything is secretly
08:44	trying to evolve into a crab , One of the
08:47	many kind of crabs , horseshoe crabs is a key
08:51	figure in another mystery . The case of the land
08:54	living in Rechnitz , horseshoe crabs first appeared in the
08:58	fossil record about 450 million years ago , and zoologists
09:03	are still arguing about who their closest relatives are .
09:06	Until recently , the case seemed closed . Horseshoe crabs
09:11	are definitely an arthropod , and their mouth parts and
09:14	body plan put them somewhere in the class of callous
09:17	arata , which would make them distant cousins with the
09:20	more famous kaliska rates are rack needs like spiders and
09:24	scorpions . At one point in evolutionary time , all
09:28	Callister , it's lived in the water like horseshoe crabs
09:30	do today . But since all Iraq needs live on
09:33	land , their ancestor must have undergone one of life's
09:37	monumental evolutionary events , leaving the sea once and for
09:42	all . So horseshoe crabs must have split off from
09:45	the callous aerate family tree beforehand putting them in their
09:48	own very ancient order , Zef Okura . But in
09:52	2019 , a long overdue genetic study turned the case
09:56	upside down . Horseshoe crabs weren't distant cousins of Iraq
10:01	needs many parts of their D . N . A
10:03	matched that of hooded ticks , spiders and camel spiders
10:07	, which means rather than cousins they are Iraq needs
10:10	. So if horseshoe crabs didn't diverge from Iraq needs
10:14	before they moved onto land , that means either that
10:18	Iraq has evolved to live on land more than once
10:21	or that the ancestor of horseshoe crabs were on land
10:25	once and then re evolved all the adaptations to live
10:29	back in the ocean . We finally had horseshoe crabs
10:33	figured out for like two months . And then another
10:37	group of researchers published another genetic study that pulled an
10:41	epic zoology , you know , reverse card . They
10:45	made some corrections and poof horseshoe crabs were definitely back
10:50	out of the Iraq needs and never lived on land
10:53	. So again , we finally had horseshoe crabs figured
10:57	out for like four months , then double reverse ,
11:01	yep , another bigger genetic study that for the first
11:05	time tossed in three truly obscure Iraq needs . Micro
11:10	whip scorpions , a rare order of mites and short
11:13	tailed whip scorpions . Horseshoe crabs were aquatic . Iraq
11:17	needs once again and this back and forth , goes
11:21	on and on and on . No one really agrees
11:24	what a horseshoe crab is or if it once lived
11:27	on land . But plenty of zoologists are still working
11:31	on the case . Being a scientist really does take
11:34	some finely tuned sleuthing skills . You take all the
11:38	evidence you can get and use it to unmask the
11:40	truth in zoology . We make our best guesses about
11:44	how something evolved or why it works the way it
11:47	does , solving these types of file a genetic mysteries
11:51	. Sometimes takes a lot of time and new technology
11:54	and underscores the power of evolution . Next episode will
11:58	talk about another common culprit and file a genetic mysteries
12:02	, unexpected gene sharing between different animals and what that
12:06	means for our understanding of how we define what a
12:10	species even is . Thanks for watching this episode of
12:14	Crash course ideology , which was produced by complexity in
12:17	partnership with PBS and nature . It shot on the
12:19	team Sandoval Pierce stage and made with the help of
12:22	all these nice people . If you'd like to help
12:25	keep Crash Course free for everyone forever , you can
12:27	join our community on Patreon .

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