Ancestral & Weird Senses: Crash Course Zoology #8 - Free Educational videos for Students in K-12

Ancestral & Weird Senses: Crash Course Zoology #8 - By CrashCourse

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00:0-1	before sight hearing or even touched before they were even
00:04	animals living things developed chemo sensation or the ability to
00:09	sense chemicals in the environment . And we know this
00:12	because every life form we've ever found has some form
00:16	of chemo sensation . But other animals have come up
00:19	with even more specialist ways to interpret information in their
00:23	environments with senses straight from the pages of comic books
00:27	. So in this episode we'll talk about the many
00:30	ways animals have made their ancestral chemo sensation their own
00:34	and how they've solved some of the challenges of following
00:37	your nose . But we'll also see electric colors with
00:40	an unusual african fish and follow pigeons trying to make
00:44	their way home with magnets glued to their backs .
00:47	I'm Ray Wynne Grant and this is crash course Psychology
00:53	. Yeah . Mhm . Mhm chemicals are pretty much
01:02	everything . Water , sugar , air all those liquids
01:06	, solids and gases around and inside of us are
01:10	chemicals and recognizing different chemicals is chemo sensation , which
01:15	today we know better as our senses of smell and
01:18	taste specifically . Key male sensation is the ability to
01:22	recognize a chemical based on the molecule shape and electric
01:26	charge . Only some chemicals can fit into the proteins
01:30	in the body called receptors in the right way and
01:33	not get repelled , which triggers signals getting sent to
01:36	the brain , which means chema sensation tells animals about
01:40	the world around them a little differently than sight and
01:43	hearing because it requires a physical interaction between the animal
01:48	and the molecules . It's sensing like taste happens either
01:52	when a chemical binds to receptors on our tongue or
01:55	when parts of those chemical molecules enter taste cells .
01:59	In both cases , the cells end up sending a
02:02	bunch of signals to the brain like sour for lemon
02:05	juice or sweet for candy smell . Also known as
02:09	olfaction works in the same basic ways taste smelly particles
02:14	bind to receptors , which also sets off signals from
02:18	our knows that our brain interprets as flowers or peppermint
02:21	or whatever . While animals usually have a few types
02:25	of taste buds , they have hundreds or thousands of
02:28	olfactory sensors . The big difference between taste and smell
02:33	is that taste happens when the thing we are tasting
02:35	directly contacts the receptors . Whereas smell happens when molecules
02:40	travel through a fluid like air into our smell organ
02:44	like a nose . We'll use a lot of smell
02:47	examples in this episode , but remember both taste and
02:51	smell are chemo sensation , they're related and in some
02:54	cases use the same organ like insect antennae that both
02:58	taste and smell . Under the right conditions , smells
03:02	travel way further than light or sound and are harder
03:05	to block with things like dense forest or rocks .
03:08	Chemo sensation is dependable , so animals deploy it for
03:11	a variety of important tasks like animals , you smell
03:15	to find things , especially food that they can't see
03:18	or hear because it's hidden behind something or too far
03:21	away . Like if you ask me , bears are
03:24	amazing and their sense of smell is one important factor
03:27	in their amazing nous . They're such good spellers that
03:31	we've never been able to truly test their limits ,
03:33	but they can sniff out food like beer larvae and
03:37	seals from miles and miles away . So with the
03:41	right nose , smell can be a super long range
03:44	sense , which presents a new challenge because odors can
03:47	slip through the tiniest of openings , spread out and
03:51	be detected at very low levels , all of which
03:54	can make it really hard to tell where the smell
03:56	is actually coming from . Not to mention that the
03:59	one who dealt it might be long gone before the
04:02	next animal smelt it . So animals have evolved adaptations
04:06	to track where a smell is coming from . The
04:09	evolutionary solution is to have chemo sensation organs that provide
04:13	information about direction , especially in pairs to better pinpoint
04:17	the smell . It's so useful to have paired smelling
04:21	structures . They've evolved over and over again . In
04:24	another example of convergent evolution , there are paired nostrils
04:29	paired in 10 A . That can move to pinpoint
04:31	smells and sounds fan like peck teens and scorpions ,
04:36	forked tongues and reptiles like snakes and much more .
04:40	Many of these tracking adaptations also help animals more generally
04:44	explore their environment . Animals also incorporate smell into special
04:49	behaviors to communicate like to attract potential mates or scare
04:53	away rivals . Like moths and orchid bees will climb
04:56	up high in trees to make sure they're attractive scent
04:59	carries far in the wind . And some animals leave
05:02	pee scat and other smelly marks and well traveled places
05:07	that are like a short biography how healthy they are
05:10	if they're stressed and if they're looking for a mate
05:13	. But it's not just pee or scat that animals
05:16	are sniffing . A lot of animals release pheromones chemicals
05:20	secreted by one animal to influence the behavior or physiology
05:24	of another animal . Some pheromones act as alarm cues
05:28	, warning other animals away from dangers . Others attract
05:33	or guide friendly animals down a safe path . Some
05:36	Mark territories and others influence animal physiology and behavior like
05:41	pheromones that cause egg laying or mating behaviors . Pheromones
05:45	can even be used by predators like the bolas spider
05:48	who uses pheromones to lay a trap for their mouth
05:51	. Pray chemo sensation is the O . G .
05:54	Sense and it's become incredibly useful for animals tracking ,
05:58	exploring and communicating . But some animals have additional senses
06:02	that basically make them real life superheroes like electro reception
06:08	which is being able to sense the electric fields or
06:11	currents that are pretty much everywhere in nature . In
06:14	fact , every time we use our nervous system ,
06:17	we're sending electrical signals through our body . So if
06:20	an animal can pick up on those tiny signals ,
06:23	they can sense other animals when it's hard to see
06:26	smell or hear them like in murky water . Plus
06:30	the earth's atmosphere has electricity in it too . So
06:34	electro reception can also tell animals about their environment .
06:37	Besides seeing the occasional spark or lightning strike , we
06:41	humans can't see or sense electricity . Almost all electric
06:46	sensing animals like duck billed platypuses , starters , moles
06:50	, sharks , and a lot of fish who have
06:52	this ability live in water because water conducts electricity much
06:57	better than air or Earth though , we've only really
07:00	looked for electro receptive animals with invertebrates . But starting
07:04	in the 1960s , scientists have been learning that several
07:08	arthropods react to electric fields , so electro reception is
07:12	a lot more common than we once thought . Some
07:14	electrically inclined animals go even further evolving special organs to
07:20	make their own electrical signals and actively sending them out
07:24	into the world around them . Either to find prey
07:27	or to chit chat with other electric fish . Less
07:30	experience a day in the life of one of them
07:33	. The elephant nose fish allow me to introduce the
07:37	peters , elephant nose fish of the dark and murky
07:41	waters of the rivers of West and central africa .
07:45	Her beautiful long schnoz isn't a nose at all ,
07:49	but an elongated chin covered in electricity sensing cells .
07:54	Each day she swims around , looking for snacks on
07:57	the riverbed and waving her chin around like a metal
08:01	detector on the beach and her electric organ , which
08:04	is made out especially adapted cells in the tale ,
08:08	sends out weak electric signals every few seconds , creating
08:12	an electric field objects like worms and rocks affect the
08:17	electric field , which she senses with her chin and
08:20	tells her where they are so she can root them
08:23	out from the gravel . Like most electric fish .
08:26	Her zepce aren't powerful enough to stun prey or scare
08:30	off Attackers , but rather they helped her understand the
08:34	world . What she's doing is similar to what bats
08:38	do with sound and Niko location , which is why
08:41	it's called electro location . And it basically lets her
08:46	see with electricity . Even a version of color as
08:51	she's looking for worms , snacks . The electricity sensing
08:55	cells in her nose . Chin respond to two major
08:59	characteristics as they sense electricity , how strong the signal
09:04	is and what shape it takes , which is kind
09:07	of how the cones in our eyes sense wavelengths of
09:10	light . The fish is brain then combines these signals
09:14	in very specific ways , just like lots of brains
09:18	combined signals from different photo receptors to perceive a color
09:23	, which gives each object an electric color . Certain
09:27	categories of objects like other electric fish or pray always
09:32	have the same electric color . Imagine if your favorite
09:36	food always glowed bright yellow , have a nice day
09:41	magnetism or the force exerted by magnets as they repulse
09:45	or attract each other is another fundamental property that some
09:49	animals can sense with magneto reception or the ability to
09:53	detect a magnetic field , which is usually the Earth's
09:57	while a surprising number of animals can shock you or
10:00	at least use electricity . No known animals make their
10:04	own magnetic fields . So magneto reception is entirely a
10:08	passive sense but useful . The Earth is a big
10:13	place and lots of animals like birds and flying insects
10:16	travel long distances to find mates food or to escape
10:20	inclement weather . And they need some kind of compass
10:24	. Other animals , like mole rats and cave salamanders
10:27	live underground where they can't see the stars or the
10:30	sun to tell them which way is east or west
10:33	. And that's where magneto reception comes in . It's
10:36	like a global compass that works in complete darkness .
10:40	Magneto reception is most well studied in migrating birds like
10:44	homing pigeons . In the early 19 seventies , a
10:47	zoologist at Cornell named William Keaton , glued magnets to
10:52	the backs of pigeons and observed that pigeons released on
10:56	sunny days could find their way home , whereas those
10:59	released on cloudy days got lost . Later on ,
11:02	scientists would find that pigeons had two major systems for
11:06	sensing magnetic fields during the day . They could use
11:09	proteins called crypto chrome's in their eyes that responded to
11:13	blue light in such a way that they reacted to
11:16	magnetic fields . And at night clusters of iron in
11:20	their beaks would be drawn vaguely north , kind of
11:23	like how a compass works , if that sounds mysterious
11:27	. Well , it is exactly how magneto reception actually
11:32	works is still something scientists are trying to work out
11:36	. For example , a lot more animals have cryptogram
11:39	in their eyes than we thought even us . So
11:42	there are some senses that are older than animals and
11:45	some that were just discovering because animals are always exploring
11:49	their environments with light , sound chemicals and even electricity
11:53	or magnetic fields to pick up crucial information . And
11:58	even though there are many different animals out there ,
12:00	we all sense and learn about the world in very
12:03	similar ways . Med Isoa really is one big happy
12:07	family so far in this course , we focused mostly
12:11	on single animals on their own . But next episode
12:15	we'll get into what happens when animals get together to
12:18	pass down their genes . I'll see you then .
12:21	Thanks for watching this episode of Crash Course ideology ,
12:24	which was produced by complexity in partnership with PVS and
12:27	Nature . It's shot on the team Sandoval Pierre stage
12:30	and made with the help of all of these nice
12:32	people . If you'd like to help keep Crash Course
12:34	free for everyone forever , you can join our community
12:37	on Patreon . Yeah .

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