What’s the Most “Animal” Animal? Crash Course Zoology #2 - Free Educational videos for Students in K-12

What’s the Most “Animal” Animal? Crash Course Zoology #2 - By Math and Science

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00:0-1	Thanks to great courses plus for supporting PBS . There
00:03	are animals that can swim walk borough or fly .
00:06	There are plant eaters and animal eaters and everything eaters
00:10	, animals that spawn eggs when they're mates and fierce
00:13	contests or partner for life from that first animal ancestor
00:17	evolved a staggering variety of species over hundreds of millions
00:21	of years Today . In 2021 we know of about
00:25	1.5 million different animals out there , but there are
00:29	still so many to discover before we dive into the
00:32	wild diversity of how animals function , behave and interact
00:36	with each other in their environment . Let's start with
00:38	understanding just one . The animal that best represents all
00:43	of meadows o . A . In the animal kingdom
00:45	. I'm Ray Wynne Grant and this is crash course
00:48	zoology . Mhm . Yeah . Zoologists want to know
01:00	what's an average animal and what's a rare animal because
01:03	it helps us understand what the life of most animals
01:06	is like and make sense of all the wild variations
01:09	out there . Now , before we pick the most
01:12	animal animal , we have to decide how we're going
01:15	to judge . In statistics . We talk about the
01:17	mean median and mode as ways to decide on the
01:20	average of something . And I think we can try
01:22	something similar with animals may be to find the mean
01:26	animal . We try to average out the features of
01:28	all animals , like add up the number of legs
01:31	and eyes and divide by the number of animals we
01:34	included . But then we'd end up with something that
01:37	doesn't match reality at all , like an animal with
01:40	a body plan for three legs and that wouldn't tell
01:42	us anything about how real animals live . Or we
01:46	could try to find the median animal by ordering them
01:48	from the first to diverge from other animals to the
01:51	latest . Then we could pick one that diverged in
01:54	the middle , but that's also hard to do because
01:57	we don't know exactly when every animal group diverged .
02:00	So the easiest move that will still give us insight
02:02	into how most medicines live seems to be figuring out
02:06	the mode or most common type of animal . First
02:09	, we need to figure out how many different species
02:12	or different types of animals there are . In fact
02:15	, generations of zoologists have tried to calculate the total
02:19	number of species on earth or the global species richness
02:22	. One technique calculates a diversity ratio or how abundant
02:26	one group of species is compared to another , like
02:29	how many beetles there are compared to types of trees
02:32	. Counting all the species in an area would be
02:35	exhausting and probably would take forever . So instead zoologists
02:40	make really accurate counts of a group of species they
02:42	know well and assume that information is representative of all
02:47	the animals in the area . In 1982 , an
02:49	entomologist or a zoologist who focuses on insects named Terry
02:54	Erwin from What's now the Smithsonian National Museum of Natural
02:57	History Used the diversity ratio technique to estimate that there
03:01	were 30 million species of just tropical arthropods . So
03:07	30 million species of insects , crustaceans , Iraq needs
03:10	, but mostly Beatles . Let's go to the thought
03:13	bubble . Trudging through the Panamanian forest . Irwin smoked
03:17	out his quarry from the canopy with the aid of
03:20	a backpack insecticide cannon , Which doesn't sound great for
03:24	the Beatles , but the reality of studying animals is
03:27	that sometimes you also study dead animals and it's often
03:31	up to the zoologist to decide what she's okay with
03:33	though there are some regulations . After meticulously examining each
03:38	arthropod back in his us lab , Irwin estimated over
03:41	1200 beetle species lived in each tree that he sampled
03:46	from . Then he did the math . Irwin estimated
03:49	13.5% of beetles would be host specific . This meant
03:54	about 162 of the original 1200 species of beetle would
04:00	only live on the type of tree . He sampled
04:02	. A hectare of tropical forest can have 40-100 species
04:07	of tree . So Irwin decided his hypothetical hectare would
04:11	have 70 species on average . That would mean there
04:14	would be 11,410 host specific Beatles , plus the remaining
04:20	1038 beetle species that are willing to live in any
04:23	old tree altogether . That's over 12,448 species of beetles
04:29	in a single hectare of forest , since 40% of
04:32	arthropods are beetles . Irwin then estimated there would be
04:37	31,120 species of arthropods per hectare . He bumped that
04:42	up by a third to account for species on the
04:45	forest floor . That avoided his pesticide fog to get
04:48	41,389 total arthropods . This was just one hectare of
04:54	one forest , but Irwin then extrapolated his formula to
04:58	include other tropical forests , which is how Irwin concluded
05:02	there were 30 million species of arthropods in the tropics
05:06	alone . Who ? Thanks thought bubble . And since
05:10	the 19 eighties , Irwin's estimate has been recalculated to
05:13	make various improvements . Like not all forest communities are
05:17	the same . Not all trees host 100 and 62
05:20	unique species and not all forests have 70 types of
05:24	tree . Aside from diversity ratios , Zoologists also use
05:28	global trends in where species tend to live called macro
05:32	ecological patterns to estimate global species richness like that more
05:36	species live in the tropics than at the poles .
05:39	We can also explore the species area relationship to calculate
05:43	the global species richness , like larger areas have more
05:46	species because there are more unique ecological roles to fill
05:50	and geographical features like mountains , rivers or oceans can
05:54	also affect species numbers by isolating populations from each other
05:58	. More recently , zoologists are turning to a new
06:01	technique called DNA Barcoding , to make their estimates of
06:04	species richness , comparing bits of DNA can identify unknown
06:08	animals or even check if what zoologists think is one
06:11	species Isn't actually two or 3 . So , using
06:15	all our different methods from diversity ratios and macro ecological
06:18	patterns . Two . DNA barcoding . In 2021 we've
06:22	counted 1.5 million animal species and estimate that the global
06:28	species richness is 8 to 10 million . And those
06:32	numbers will change with new information and techniques next to
06:36	decide on the most animal animal . We have to
06:39	look across all these millions and millions of animals and
06:42	figure out which traits are rare and which are common
06:45	, like being able to fly sound so cool ,
06:48	but flight is actually pretty common to keep track of
06:51	all the different traits . Remember , we use binomial
06:54	nomenclature and break animals up into a similarity hierarchy ,
06:58	starting by grouping animals of the same type together as
07:02	a species . At the very top of the hierarchy
07:05	is the entire animal kingdom . But just below that
07:08	zoologist collect species in large groups called fila or phylum
07:12	for just talking about one group based on their evolutionary
07:15	history and their body plan . A phylum is like
07:18	a genre of animals . They share some key characteristics
07:22	, but each lineage within a phylum is a little
07:25	bit different . Our mode animal probably belongs to the
07:28	most successful phylum , which for us means the phylum
07:32	that's made it all the way to the top of
07:34	the billboard . Top 40 ish of evolution and has
07:38	lots of different species with a wide variety of traits
07:41	diverse Fila are like the mainstream hits . They're unlikely
07:45	to go extinct because they have so many different species
07:48	spread across different habitats and niches and fill it with
07:52	just a few species are the hidden indie gems much
07:55	less successful and much more vulnerable to getting wiped out
07:59	. The top fila aren't who you think like so
08:02	far ? We know that there are 65,000 species of
08:05	core dates or animals with a flexible rod to support
08:08	their body called a note accord Which includes fishes ,
08:11	Amphibians , mammals , reptiles , and birds . That
08:14	sounds like a lot . But remember the global species
08:18	richness is between eight and 10 million . So they're
08:21	the pop music of the animal kingdom , super famous
08:24	and popular , but only about .03% of all animals
08:29	. And there are 35 ish different Philip . So
08:32	, despite what we might see and hear , most
08:34	other animals are well . Non coordinates phylum arthropod A
08:39	includes over 1.1 million different species , making them the
08:44	true rock stars of evolution . Named for their jointed
08:47	limbs . Arthropods have a segmented body covered in a
08:50	hard exoskeleton and include insects along with crustaceans . Mila
08:55	, incentive feeds , horseshoe crabs , spiders , scorpions
08:58	and other Kalis arr . It's so to narrow it
09:01	down and get into what our mode animal looks like
09:04	eats and where it lives . Let's live a day
09:07	in the life of the most animal animal . Allow
09:10	me to introduce you to the humble of mode animals
09:13	as insects are the biggest group of arthropods . Our
09:16	mode animal moves through life on six legs with three
09:20	body segments , compound eyes and 10 and a hard
09:23	exoskeleton that still just paints a vague insect shaped picture
09:29	. So the biggest order within class in sector is
09:32	Kolia . Qtera . The Beatles . Beatles diverged a
09:35	very long time ago , with the earliest fossils being
09:39	300 million years old , so they've had a lot
09:42	of time to split off into over 386,000 estimated species
09:47	Representing about 1/4 of all known animals . But all
09:51	these beetle cousins share a few key body parts .
09:54	So our mode animal definitely has front wings that form
09:58	a protective shell to find our average friend , one
10:02	need only lift up the nearest rock or sift through
10:06	the sand , as beetles can live almost anywhere .
10:09	With every new habitat comes a slew of specialized niches
10:13	that beetles have evolved to fill and with so many
10:16	different habitats , beetles have grown to eat all sorts
10:20	of things . So there's lots of local delicacies out
10:23	there to help lots of young larvae store up energy
10:27	. Our mode animal will be an average joe in
10:31	a wildly diverse family photo , like a carpet beetle
10:34	squeezed in between a weighty titan beetle and a cheery
10:38	ladybug . But today our friend is special because it's
10:42	so average have a great day , little beetle .
10:45	But just because beetles are popular now doesn't mean they
10:49	always will be as zoologists pay more and more attention
10:53	to things like nematodes and parasitic wasps , maybe one
10:57	of them will unseat the beetle as the mod animal
10:59	as we discover more and more species and revise our
11:02	estimates . Next time we'll continue exploring what it means
11:06	to be an animal and how they've evolved into so
11:09	many different shapes and sizes . Thanks to great courses
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12:01	to start your trial today . Thanks for watching this
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