How & What Animals Eat: Crash Course Zoology #4 - Free Educational videos for Students in K-12

How & What Animals Eat: Crash Course Zoology #4 - By CrashCourse

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00:0-1	The art of eating was passed down from the original
00:02	animal ancestor to all its descendants . But exactly what
00:06	and how that ancestor eight remains mysterious . Maybe it's
00:10	snagged tiny organisms that got stuck in its pores like
00:13	the periphery since the sponges or swallow their prey and
00:17	then liquefied it to circulate through their body with a
00:20	canal system , like a nutritious smoothie . Allah jennifer's
00:24	. We can look to these early diverging animals for
00:27	clues , but we know from the metas own ancestor
00:31	evolved all the feeding mechanisms and adaptations that we see
00:35	in today's animals . Now there are animal eaters ,
00:38	Plant and fungi eaters and both eaters , but also
00:42	would eaters . Bone eaters and decaying things eaters ,
00:46	each of which requires a suite of adaptations to turn
00:49	food into nutrients and energy . Animals evolved to eat
00:53	a lot of different things , even stuff that barely
00:56	passes for food and it shapes our entire lives from
00:59	what we look like to where we live . So
01:02	grab a snack because today's episode is gonna make you
01:05	hungry . Well , until we start talking about what
01:08	happens to food after you've digested it . I'm Ray
01:11	Wynne Grant and this is crash course zoology . Mhm
01:21	. The film along with moving sexually reproducing and having
01:27	multiple cells , eating is one of the key traits
01:30	we inherited from the original animal ancestor . And part
01:33	of the very definition of what makes something an animal
01:37	specifically animals are ingested hetero troughs , which means we
01:41	engulf food with our bodies and don't make it from
01:44	non living sources . Like I would love to gobble
01:47	up some fettuccine alfredo right now . But my little
01:50	desk succulent would prefer to make its own food by
01:53	absorbing sunlight , carbon dioxide and a hint of water
01:56	of course , even though fettuccine alfredo is delicious ,
01:59	I admit it might not be for everyone . So
02:02	to better understand how animals live , we're interested in
02:06	two major things what animals eat and how they eat
02:10	it , Both what and how have changed and expanded
02:14	over time . As more animals and food sources have
02:17	developed . One of the oldest diets is carnivorous or
02:21	eating other animals . Animal eating animals like those 10-4
02:25	. As we mentioned , that liquefy their prey probably
02:28	evolved long before plant eating animals . One piece of
02:31	evidence for this is that if we consult the animal
02:34	tree of life , the common ancestors of many fila
02:37	are carnivores , which means that animals in those groups
02:41	likely came from animal eaters . Plant eaters only show
02:45	up within the fila . Later . In fact ,
02:48	animals could have been eating other animals for over 600
02:51	million years , which means carnivorous developed many millions of
02:55	years before plants even existed on land , Though there
03:00	could have been some plant eaters in the oceans .
03:02	Today . About 63% of animals are carnivores , according
03:06	to a 2019 study by scientists at the University of
03:08	Arizona , which might be surprising considering there are lots
03:12	of plants around and plants don't run away or fight
03:15	back . Usually herb ivory or eating plants and fungi
03:19	requires a new set of adaptations to eke out calories
03:22	and to turn plant cells into animal cells like flat
03:26	teeth and special organs called gizzards , to grind them
03:29	up specialized gut bacteria to demolish the tough cellulose and
03:33	plant cell walls , and a lot of time to
03:36	chew . Re chew and digest huge volumes of food
03:40	. It's easier to be a carnivore . Carnivores get
03:43	a lot of energy from one serving and more easily
03:46	get protein and fats from their diet and their intestines
03:50	push food through more quickly because they can get away
03:52	with being less efficient at extracting nutrients . About 32%
03:56	of animals are herbivores , according to that same 2019
03:59	study and 3% are animals like bears , crows and
04:04	us . Humans who use omnivorous or eating both plants
04:08	and animals . Having a flexible diet sounds like a
04:11	bright idea , but it's kind of a catch 22
04:14	omnivores have lots of food options , but they also
04:17	have to maintain a lot more biological machinery than animals
04:21	that eat just one kind of thing . But it's
04:23	the remaining 2% of animals that really push the definition
04:27	of food beavers , ship worms , which are a
04:30	type of clam and insects like termites are Zyla Frazier's
04:34	or would eaters . Even the wood is a terrible
04:37	food . It's almost entirely made of hard to break
04:40	down cellulose and has very few nutrients and calories .
04:43	So like more traditional herbivores would eaters have extra adaptations
04:47	to get their calories like their own cellulose busting proteins
04:52	and some would eaters cheat by sneaking other plant parts
04:55	and fungi into their diet . But osteo Frazier's take
04:58	it a step farther and eat bone , which is
05:02	pretty amazing when you consider that bone is basically biology's
05:05	best impression of a rock . There's a fair amount
05:08	of protein and bone marrow . So animals like bone
05:11	worms , a group of deep sea pollock , it's
05:13	secrete a bone dissolving acid out of their mouths to
05:17	burrow into whale bones where they find fats and proteins
05:21	. Even some herbivores , like giraffes and cows will
05:24	chew on bones to add phosphate and calcium into their
05:26	diet minerals , which are hard to come by and
05:29	plants . Well , I'm not going to add wood
05:32	and bone to my grocery list , but termites ,
05:35	bone worms and others might have evolved such weird tastes
05:39	because it can be advantageous to figure out how to
05:41	eat something . No one else can , even if
05:44	requires some bizarre eating habits . The animal menu has
05:48	lots of options , but how do different animals stuff
05:51	their faces or whatever they do to eat ? If
05:53	they don't have a face even within one ocean ,
05:57	there's a huge variety in the way animals eat many
06:00	whales , fish , barnacles , shrimp , jellyfish and
06:03	other animals . Large and small are filter feeders ,
06:07	which means they capture food suspended in water or air
06:10	in the ocean , filter feeders , filter water trapping
06:13	relatively tiny bits of food in bay leans modified gills
06:17	, feeding baskets woven with legs . Or if you're
06:20	a sponge holes , whether they let the food come
06:23	to them or find places where tiny bits of food
06:26	are plentiful , filter feeders don't bother with hunting anyone
06:30	target in particular . They just gulp in the general
06:33	area and let the filters do their job . But
06:35	there's a lot more to eat in the ocean than
06:37	just tiny food particles . Filter feeding is a pretty
06:41	simple strategy , So we see a huge variety of
06:44	animals doing it . But to eat larger and more
06:46	specialized food items , animals need to evolve a more
06:49	specialized structure , namely Ahead Heads can be optional for
06:54	filter feeders , but predators like octopus is out there
06:57	killing and consuming another organism to absorb its nutrients need
07:01	ahead . They combine the sense organs that find food
07:04	and the weaponry that clinches the food . In one
07:07	convenient package , dolphins , comb jellies , bob at
07:11	worms and other animal eating carnivores are also definitely predators
07:15	, but you don't have to necessarily be a carnivore
07:18	to be a predator . Even do dogs . Sometimes
07:22	called sea cows and other herbivores can be predators too
07:26	. Their plant predators if they eat and kill the
07:29	whole plant or eat things that are future , whole
07:32	plants like seeds and then there are the animals that
07:35	eat dead stuff . These are scavengers who wait for
07:38	something else to do the killing before they dig into
07:41	the carcass and Detroit divorce , who eat bits of
07:44	decaying plants and animals and their poop . And these
07:48	garbage eaters are really important because they recycle nutrients through
07:52	their animal communities so everyone can feed again . How
07:56	animals eat can intersect in many ways with what they
07:59	eat . Like predators can be herbivores and scavengers can
08:03	be carnivores or bone eating Osteo Frazier's and you might
08:07	start out eating one thing one way and completely change
08:10	over time , whether it takes millions of years or
08:13	just a lifetime . One mode of feeding we haven't
08:16	talked about yet is parasitism , which is a special
08:19	kind of predation entomologist . E . O . Wilson
08:22	put it best calling parasites predators that eat , pray
08:26	in units of less than one . Just hitch a
08:29	ride on or in your host and nibble at them
08:32	forever . We'll get you hooked on parasites in a
08:34	later episode . But as a little appetizer , let's
08:38	experience a day in the life cycle of a parasitic
08:41	filter feeding bloodsucker allow me to introduce the sea lamprey
08:47	or petra mizzen marinas , a creature so evolutionarily ancient
08:52	, it diverged from other fish before they developed jaws
08:55	and fish have had jaws for a long time ,
08:58	about 500 million years Until about 80 years ago .
09:03	It was impossible to find a sea Lamprey here in
09:07	lake michigan , but this lamb braised , enterprising ,
09:10	great , great great grandparents found their way inland as
09:14	human workers widened and deepened shipping canals in the great
09:18	Lakes region . And ever since generations of sea lamprey
09:22	like this one have feasted on trout , whitefish and
09:26	other smallish lake fish is latching onto them with their
09:30	sucker mouth filled with hooks like ancient vampires . This
09:34	sea lamprey is so large compared to the lake fish
09:37	and causes so much blood loss and damage that they
09:41	act more like a predator than a parasite in the
09:44	Great Lakes ecosystem . But once the sea lamprey has
09:48	grown large and become a mature adult by feasting on
09:51	nutrient rich fish , blood , she'll migrate upstream to
09:55	lay eggs . She won't live to see her larvae
09:58	grow up or make sure they get enough to eat
10:00	. But lamprey larvae can take care of themselves .
10:04	They're filter feeders , snacking on tiny plants , microbes
10:08	and other junk that they trap in mucus in their
10:10	throat . Eventually , these lamprey larvae develop into parasitic
10:15	juveniles , moving downstream in search of the big ,
10:19	tasty prey that nourished their parents years before their whole
10:23	digestive system shuts down for months as they turn into
10:27	a vampire and shift from a Detroit devore to a
10:30	parasitic carnivore . Once that's done , they can really
10:34	take advantage of the benefits of feasting on flesh as
10:38	they mature and get ready to have their own larvae
10:41	. It's a circle of lamb , prairie life ,
10:44	sea lamprey show how easily animals can flip between filter
10:49	feeder parasite and predator based on their life stage and
10:52	ecological context . They also show what and how an
10:56	animal eats , whether it's tiny scraps or the finest
11:00	fish in the great lakes has a huge influence on
11:03	other parts of the animals life like how it looks
11:06	and acts . But regardless of how they get it
11:09	, all animals have to digest or break down the
11:11	engulfed food in small molecules that can be absorbed by
11:15	the body . And then , well , it's poop
11:19	, we're talking about poop after the food is digested
11:22	waste . Excretion which is like taking out the biological
11:26	trash is essential . Otherwise all the bits that animals
11:30	can't eat build up , some of which are quite
11:33	toxic . Simple tiny animals like placa zones and rama
11:38	zones get rid of their carbon dioxide and ammonia waste
11:41	by just pushing it out through their cell membranes and
11:44	into the environment . More complex animals have a lot
11:47	more cells . So they have dedicated systems for liquid
11:50	waste excretion which can be stuff like uric acid ,
11:54	urea or ammonia depending on the animal's diet and biology
11:58	. Then there's this solid stuff which can be made
12:00	up of things that didn't get completely digested . Like
12:03	cellulose mucus and bacteria . We have to get rid
12:07	of it at some point . But some animals vary
12:10	the timing , like eyelash mites don't poop at all
12:14	. Instead they store all their waste in their bodies
12:16	until they die . which is after only a few
12:19	weeks while this may seem like a horrible and gross
12:22	adaptation , a few weeks is enough for the mites
12:25	to grow and reproduce and they don't need to use
12:28	any energy to grow an excretory system . And they're
12:31	super successful . Basically , every human has little poop
12:34	filled mites on their skin . So just like there's
12:37	a range of what and how animals eat , there's
12:40	a whole lot of ways for them to get rid
12:42	of it too . So to some extent , we
12:45	are , what we eat eating is a fundamental trait
12:48	to being an animal that's been passed down from the
12:51	earliest metas Owens and the food animals choose and how
12:55	they engulf . It dictate their role in the environment
12:57	and even how successful they and their descendants will be
13:01	. Next time we'll talk about a body system that
13:04	makes you feel hungry and the head honchos that coordinates
13:08	just about everything else in an animal body , the
13:11	nervous system and brains . Thanks for watching this episode
13:15	of crash course ideology , which was produced by complexity
13:18	in partnership with PBS and Nature . It is shot
13:21	on the team Sandoval Pierre stage at porchlight studios in
13:24	santa barbara California and made with the help of all
13:27	of these nice people . If you'd like to help
13:30	keep crash course free for everyone forever , you can
13:32	join our community on Patreon .

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