What is an Animal? Crash Course Zoology #1 - Free Educational videos for Students in K-12

What is an Animal? Crash Course Zoology #1 - By Math and Science

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00:0-1	Some of our earliest records of humanity are 40,000 year
00:03	old cave paintings that show what was important to our
00:07	ancestors . There are handprints and little people figures ,
00:10	but there are also or rocks , bison , giant
00:14	sloths and camels . Thousands of years later , one
00:17	of the most significant cultural and technological revolutions occurred when
00:22	farmers in the fertile crescent , domesticated sheep , pigs
00:26	and other livestock . For as long as there have
00:28	been humans , there have been creatures sharing our lives
00:32	, planet and history And together in this series will
00:35	walk , crawl , fly and swim through the animal
00:39	kingdom , tracing the evolution of the over 1.5 million
00:43	different creatures we know about and what the lives of
00:46	both the animals and the zoologists have studied them are
00:49	like . But before we can do that , we
00:52	need to figure out what it means to be an
00:55	animal . I'm ray Wynne grant and welcome to crash
00:58	course zoology . Yeah . Animals have always been part
01:10	of our lives , but there's still so much to
01:13	learn . Even just about one particular animal . Take
01:17	this bear . We could study how it's related to
01:20	other bears , like polar bears or how and why
01:23	it can smell food miles away , or we could
01:27	track where this bear lives and what happens when it
01:29	crosses paths with humans . All of these questions are
01:32	part of zoology , which is basically the scientific field
01:36	dedicated to asking and answering questions about animals . Today
01:41	, zoologists are many different things scientists , veterinarians ,
01:45	biomedical engineers , conservationists and so much more . So
01:50	really the question isn't who is a zoologist ? But
01:54	what is an animal ? We're pretty sure beetles or
01:58	fish are animals , but amoebas or sea sponges drawing
02:03	the line can be surprisingly difficult to organize the chaos
02:07	of life on earth . So ologists , ecologists and
02:10	other ists rely on taxonomy , the branch of science
02:15	dedicated to naming , describing and classifying organisms . It's
02:19	tricky work because no two types of animals are exactly
02:23	the same , even though some features like eyes are
02:27	shared by lots of animals . So it's not unusual
02:30	for an animal to be re categorized and renamed over
02:34	time . Zoologists have a long tradition of proposing different
02:38	ways to categorize life with varying degrees of success .
02:42	Like to Aristotle , the greek , philosopher and influential
02:46	. Early zoologist . Plants were sort of the baseline
02:50	. They grew and produced new baby plants , but
02:53	that's it . Animals also grew and reproduced , but
02:56	they were separate from plants because they moved and sensed
02:59	their environment . And while we now know humans are
03:03	a type of animal , Aristotle grouped us separately because
03:07	we're capable of deep thought and reflection . Well ,
03:10	sometimes Aristotle and his plant animal human system influenced generations
03:16	of zoologists , including carl linnaeus who developed binomial nomenclature
03:22	the system of giving all animals a unique to part
03:25	latin name . We remember both Aristotle and Lenny's as
03:29	important men , but no matter what we're studying ,
03:32	scientists are people making choices about what's worth paying attention
03:37	to and they're not always right or fair . Some
03:41	of lenny's is other work is considered scientific racism ,
03:44	a debunked pseudo science that categorizes humans into varieties based
03:50	on their skin color and stereotypes . These views are
03:53	widely discredited , but there's still a lot of work
03:56	to do in dismantling racism in science . In his
03:59	work on binomial nomenclature , Lenny is set up a
04:03	similarity hierarchy where we move from most similar groups to
04:08	least similar groups . So on one end we divide
04:11	by species which is a group of all the animals
04:14	of the same type that can breed together over multiple
04:17	generations than in the next level . Different animals that
04:21	are the most similar they can be without being part
04:24	of the same species are grouped into a genius and
04:28	we build up from there to bigger ranks like family
04:31	class all the way up to kingdom . The genus
04:35	species combo is how we identify animals in modern binomial
04:39	nomenclature , because no two types of animals have the
04:42	same one . So Ursus americanus is the north american
04:46	black bear and denies plex opus is a monarch butterfly
04:50	. Distantly related animals always have a different genus ,
04:54	but they could have the same species name . Some
04:57	words are just useful descriptors like elegance meaning elegant or
05:01	vulgaris which means common , but scientists are an efficient
05:05	bunch . And given the chance we abbreviate almost anything
05:10	Sosa printed on elegance . Sarah Kozmus elegance , caenorhabditis
05:15	elegance and cycle enormous elegance are all C elegance .
05:20	So now we've got C . Elegans , the pup
05:23	fish . C elegans , the tarantula , C .
05:26	Elegans , the nematode and C . Elegans , the
05:30	turtle , You know your zoologist When you start thinking
05:32	of worms , turtles , fish and tarantulas . As
05:35	elegant . Using the same abbreviation is confusing but it's
05:40	also an opportunity to explore just how related some animals
05:44	are with something called a taxonomic sandwich . Let's go
05:48	to the thought bubble . Think of our to see
05:50	elegance as our bread and the evolutionary time or the
05:54	years since the two species last shared an ancestor as
05:57	the filling . But calculating evolutionary time and organizing animals
06:02	isn't easy . Originally scientists like linnaeus grouped animals based
06:07	on their looks . Many animals have similar traits because
06:10	they're related called homologous traits but they can also have
06:14	similar traits that evolved completely independently which are called analogous
06:19	traits . So if we thought the wings of insects
06:22	, bats and pterosaurs were homologous traits , we group
06:26	them together and we might think it hasn't been too
06:29	long since the animals were related . But if wings
06:31	are an analogous trait , we can't use them to
06:34	tell how closely related the animals are figuring out .
06:37	If a trait is homologous or analogous can be really
06:41	hard . So to get more information , scientists also
06:45	look at an organism's DNA . To suss out evolutionary
06:49	relationships , like we can use the molecular clock approach
06:52	, which estimates how long ago two species diverged by
06:55	comparing their DNA sequences basically in the molecular clock approach
07:00	, we assume that DNA sequences mutate or change over
07:04	time at predictable rates . By combining the information about
07:07	mutation rates with the fossil record . We can then
07:11	estimate how long ago to animals shared an ancestor using
07:15	observations and DNA zoologists estimate the tarantula turtle . See
07:20	, elegant sandwich has 600 to 800 million years of
07:25	filling , While the Turtle Fish Sandwich has only 443
07:30	million years . That's when these animals last shared a
07:33	common ancestor , which likely had traits the two have
07:36	in common . Thanks , that bubble will make more
07:39	taxonomic sandwiches throughout this series to explore animals , often
07:43	surprising evolutionary relationships and to help us decide what's really
07:48	an animal . It's taken centuries of exploring evolutionary time
07:53	, but scientists generally agree that four key traits make
07:57	animals special animals are eaters , movers , sexual re
08:02	producers and multicellular earth like this . Lioness is made
08:06	of millions of cells . Her cells work together as
08:10	she hunts and digest her prey and her cubs are
08:13	born by combining her genetic information with her mates .
08:16	But nature loves to break rules . Some animals only
08:20	do these things for part of their life , like
08:23	may flies that feast as larvae but lack mouths and
08:27	guts as adults . And even some non animals have
08:30	animal traits like carnivorous plants that trap and eat bugs
08:35	. So to resolve these tricky edge cases , we
08:38	need more information about where these traits come from .
08:41	We have to look back in time . A living
08:44	things evolutionary history is like a genetic record of how
08:48	it came to have all the traits it has today
08:51	. It describes the living things , relationships with any
08:54	living relatives and extinct ancestors and how they've all evolved
08:59	or changed over time . By studying evolutionary histories through
09:03	fossils and DNA 19th and 20th century zoologists figured out
09:08	that there was one ancestor species that had multiple cells
09:11	and eight moved and sexually reproduced . Zoologists have deduced
09:16	this first animal was probably a blob with a mouth
09:19	, but we don't have a fossil of it or
09:21	anything to know just how blobby it was , but
09:25	from it came everything we call an animal , even
09:28	if they've lost some traits over time . So those
09:30	non eating may flies aren't still animals because their evolutionary
09:35	histories traced back to that original animal ancestor . But
09:38	carnivorous plants aren't animals because they aren't descended from the
09:43	original animal ancestor . Studying homologous and analogous traits ,
09:47	evolutionary history and other relationships among living things is called
09:52	phyllo genetics , keeping track of who's related to who
09:55	can get messy . So we study animal relationships using
09:59	a diagram called a philology or file a genetic tree
10:03	in a file , a genie , individual species or
10:05	groups of species sit at the tips of the tree
10:08	and the branches represent all the different lineages that diverged
10:12	from common ancestors . Branch lengths also show how related
10:16	species are , The longer the branch , the more
10:19	distantly related to groups are . So using observations and
10:23	the molecular clock approach , we can decide which traits
10:26	will help us group animals into clay beads or a
10:29	group with all the descendants of the same common ancestor
10:32	and fit those clouds together into a file . A
10:35	genie now clade aren't a rank like species or phylum
10:39	. They're a type of group and can work kind
10:41	of like nesting dolls claims can be very large like
10:45	the clay that includes all animals called med , Isoa
10:48	or tiny . Like the happier include of monkeys ,
10:51	tar , Sears and apes . And we could have
10:53	clade within plaids with incl AIDS . It just depends
10:57	on which common ancestor we focus on to actually build
11:01	Arqule AIDS . The simplest approach is to go for
11:03	maximum parsimony where the file , a genie with the
11:07	fewest number of gains or losses of a trait winds
11:10	like it's more parsimonious to assume that a single dinosaur
11:14	evolved feathers and past feathers onto its descendants , including
11:19	birds . It's less parsimonious to assume that the ancestors
11:23	of ostriches , chickens and songbirds all evolved feathers independently
11:27	. So as zoologists using maximum parsimony , we'd choose
11:31	the file , A genie that shows feathers evolving once
11:35	. Another . Popular approach is to focus on maximum
11:37	likelihood , which predicts evolutionary relationships by calculating the probability
11:43	of the thousands of mutations needed to change one sequence
11:46	of DNA into another . Using the maximum likelihood approach
11:50	, we'd end up with a file A genie where
11:52	the sequence of events has the highest probability file a
11:55	chinese are complicated because they're tracking many different traits ,
11:59	animals and time all at once , and they can
12:02	rotate around their notes . So this file , a
12:05	genie , this file , a genie , and even
12:08	this file . A genie are exactly the same .
12:10	Visuals can be misleading , and so can words like
12:13	advanced or primitive because no living species is more evolved
12:18	than any other . Instead , zoologists used terms like
12:22	early diverging plaids to describe splits that happened a long
12:26	time ago and late diverging plaids which split off more
12:30	recently . There is no best way to make a
12:32	file a genie and one file a genie really is
12:35	just a hypothesis for all the evolutionary relationships between species
12:40	. Orcl AIDS based on specific traits or groups of
12:43	traits . So zoologists will often make several file a
12:46	chinese using different approaches . If we keep getting the
12:49	same answer , we know our file . A genie
12:51	is a good guess for how different animals are related
12:54	to each other and we can use it to help
12:57	answer our big question . What is an animal like
13:01	these little creatures called Cohen ? A fragile ? Its
13:04	first on our checklist , we know animals move well
13:08	. Conan o fragile . It's have little flat gela
13:10	that whip back and forth to move them from place
13:13	to place check next animals eat cohen oh fragile .
13:18	It's eat bacteria . They catch themselves . Check Animals
13:22	sexually reproduce . So do cohen a fragile . It's
13:26	another check . And finally animals are multicellular as we
13:31	can see , kona flagellating are single celled organisms .
13:34	But we know animals don't always have all four animal
13:38	traits . So let's go to the file a genie
13:40	. Unlike animals , Cohen oh , flagellating can't trace
13:44	their lineage back to the last common ancestor of all
13:47	animals . This is according to many in depth studies
13:50	into the genetics of these organisms . So cohen oh
13:53	, flagellate aren't animals but by making fila genies and
13:57	examining DNA , we do know they're the closest non
14:01	animal relative we've got . Well that's just fascinating .
14:04	Ultimately zoology is asking and answering questions about animals and
14:10	hopefully busting some myths along the way . All living
14:14	animals have been evolving for the same period of time
14:18	since the common animal ancestor first existed . This is
14:22	why knowing an organism's evolutionary history is so important .
14:27	But now that we have a good handle on what
14:29	an animal is next episode will tackle how many of
14:33	them there are . Want more zoology . Then you'll
14:37	want to check out PBS's newest show animal like you
14:40	hosted by Trace Dominguez Animal I . Q . Features
14:43	deep dives on animal minds to find out just how
14:47	smart the animal kingdom really is . We know that
14:50	humans are clever . But can you find your friends
14:52	in a crowd as well as a baby penguin ,
14:54	drive a car as well as this rat . To
14:57	see full episodes of animal . Like you click the
14:59	link in our description below and be sure to tell
15:02	them Ray wants more bear content . Thanks for watching
15:05	this episode of Crash course ideology which was produced by
15:08	Complexly in partnership with PBS and Nature . It is
15:12	shot on the Team Sandoval Pierre stage at porchlight studios
15:15	in santa barbara California and made with the help of
15:17	all these nice people . If you'd like to help
15:20	keep crash course free for everyone forever , you can
15:23	join our community on Patreon .

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