There were all kinds of
teeny-tiny animals skittering and slithering
around our planet. But have you ever stopped
and wondered what actually is the smallest animal on Earth? Let's find out on today's
episode of Colossal Questions. [music playing] In order to answer
this question, we first need to
decide on an answer for a much more basic question. What actually is an animal? Seems simple, right? Well, as it turns
out, the answer actually gets a bit murky. Scientifically
speaking, an animal is any living organism that's
made up of multiple cells, eats organic material,
breathes oxygen, can move, and can reproduce. Humans fit the bill. We're made up of trillions
of different cells. But there are lots of
things out there so small that they're made up of just
a few cells clumped together. There are some living
things out there that are made up of just one
single cell, like bacteria. Well, that means they're
not considered animals but prokaryotes instead. That's just a fancy
science way of saying they're a super basic,
single-celled organism. In fact, their cell doesn't
even have a nucleus, which is what controls a cell. More complex cells, like
animal cells, have a nucleus. Inside that nucleus
is all the DNA that helps make us into
something much more complex than a single cell. These types of organisms
are called eukaryotes. Almost all living organisms
you can see on Earth are eukaryotes, including
plants, and, yes, all animals. In 2011, the smallest known
animal was discovered, a jellyfish called a Myxobolus. They can be really small, like
less than 9 micrometers long. That's around 1/1000 of an inch. Really tiny. Of course, this is just
the smallest animal we currently know about. New discoveries are
made all the time. So who knows? Before long there could
be an even smaller critter crawling around somewhere. OK, so this little
jellyfish might technically be the smallest animal
we know about today. But it does beg the
question, what's the smallest known
animal you can actually see with the human eye? The answer to that
question is found on the second largest island
in the world, New Guinea. That's where
scientists back in 2009 discovered the smallest known
vertebrate in the world hopping around the jungle,
a tiny little frog called Paedophryne amauensis. The average adult only grows
to be about 8 millimeters long from end to end, which is only
slightly bigger than the eraser on the back of your pencil. Then there you have it, a
seemingly simple question with a surprisingly
complex answer. So for now those
microscopic little jellyfish will remain the smallest
animal on Earth. And our little frog
friend will continue to be the world's smallest
known vertebrate, that is, until we find something
smaller, of course. Over eons of time, there have
been tons of titanic creatures who have walked the Earth,
soared through the sky, and swam in the oceans. But have you ever
stopped and wondered what actually is the largest
animal to ever exist? Let's find out on today's
episode of Colossal Questions. [music playing] Many of the biggest
animals to ever exist live hundreds of thousands or
even millions of years ago. Take Gigantopithecus,
for example. The largest ape to ever
live was a distant relative of modern day orangutans,
who stood somewhere between 8 and 10 feet tall. That's mighty big to us humans. But it pales in comparison
to the biggest animals ever. The largest creature
living on land today is the African elephant,
which can weigh up to 7 tons, which is about the
same as your average delivery truck. A full grown
African elephant can be up to 35 feet
from trunk to tail and stand about 12 feet tall. OK, that's the largest
land animal on Earth today. But what's the
biggest animal ever? Well, believe it
or not, it's not a dinosaur or a woolly
mammoth or any kind of colossal creature
from the past. That's right. It turns out the largest animal
ever is actually living today. But it doesn't live on land. It thrives deep in the
ocean, quietly bigger than any massive meat
eater who ever lived. It's the blue whale. And it's not even that close. Blue whales can be anywhere
between 75 and 100 feet long when they're fully
grown and can weigh well over 100 tons. To put that into
perspective, that's about as long as three school
buses lined up and heavier than a space shuttle. Their heart is about
the size of a small car. And their arteries are
big enough for a human to actually climb through. They're so big that
a group of 50 people can stand together on
a blue whale's tongue. Even baby blue whales are big. A newborn calf is
about 25 feet long and already weighs more
than an African elephant. This makes blue whales not just
the biggest creature on Earth but the biggest
by a wide margin. You might imagine that
the mighty dinosaurs who lived millions of
years ago were bigger. But, nope, maybe the
largest known dinosaur is the Argentinosaurus,
which only weighed around 180,000 pounds
or about half the weight of a blue whale. It might seem surprising to us. But it actually
makes a lot of sense that the world's biggest
creatures live underwater rather than on land. Land animals have to be able
to support all that weight. But sea creatures
get some extra help from the water,
which makes it easier to grow nice and,
well, colossal! There's plenty of
creatures on Earth that can do all kinds of damage. But who is the most
dangerous of them all? Let's find out on today's
episode of Colossal Questions. [music playing] We have lots of good candidates
for deadliest animal on Earth. Take elephants for example. They're the largest
land animals on Earth and can be fiercely
aggressive when provoked. They have no problem dribbling
people or other animals or even entire villages
when they're angry. And if that wasn't
destructive enough, elephants also have
excellent memories, which means they might even
hold a grudge if they're really wronged. Hippos are another of Earth's
most aggressive animals. Even though they
mostly eat plants, hippos are huge and more
than willing to fight even for no reason at all. And yet, the deadliest
animal of them all is also one of the smallest-- mosquitoes. These bothersome little bugs
are so deadly because they can spread viruses
from person to person when they suck your blood. Expert's report that nearly
700 million people each year get a disease from a
mosquito bite, which leads to somewhere between
two and three million deaths. Malaria, dengue,
and Zika are three of the many diseases that you
can get from mosquito bites if you live in high-risk areas. But before you start
building a bunker to hide in, there is some good news. Since the year 2000,
medical advancements have led to an almost 40%
drop in malaria deaths. And unless you live
in certain areas, there's no real risk of
getting a deadly disease. So next time you're on a safari,
just keep a safe distance from the elephants and hippos. And definitely wear bug spray. [music playing] Every year more and more
animals are in serious danger of going extinct. But have you ever
stopped and wondered, what causes animals to go
extinct in the first place? Let's find out on today's
episode of Colossal Questions. [music playing] Of all the animals that
have ever lived on Earth, 99.9% are now extinct. The first and most common
way that animals go extinct is what we're going to call
extinction by natural causes. This is when a species dies
out naturally because of forces like climate change,
competition from other animals, a reduced food supply, or
most likely a combination of all three. Most natural extinctions happen
very slowly, over hundreds or even thousands of years. But every once in a while,
a catastrophic event can lead to a quick
mass extinction, like the meteorite that
killed the dinosaurs. Natural causes may have
been the main reason animals went extinct throughout
most of Earth's history. But over the last
couple hundred years, humans have given nature
a run for its money as the biggest
cause of extinction. That's right. Over the last 500
years or so, humans have hunted lots of
animals into extinction. Take the passenger
pigeon, for example. When European settlers first
arrived in North America in the late 1800s, there were 3
billion to 5 billion passenger pigeons living there. By the 1800s, hunting and
eating the poor pigeons was so widespread in US
that the very last passenger pigeon died in 1914. And that's just one example. Some species, like the
American bison, are luckier. Millions of bison
lived in North America until the Europeans arrived. Hunting was so intense that
only 541 were left by 1889. Sound familiar? Well, unlike the
passenger pigeon, this story has a happier ending. A handful of ranchers gathered
the remaining bison together to save them from extinction. Since then their
numbers have flourished. And more than 300,000
bison live today on farms and national parks
around the US and Canada. [music playing] Animals are also hunted for
body parts like fur, feathers, hides, or horns. And hunting isn't
the only way humans cause animals to go extinct. Habitat loss is a
huge problem too. When we build giant
farms to grow food, the natural land that
many animals rely on is destroyed, leading
to their extinction. Pollution can poison the land,
air, and especially water and has at least 700
marine species on the brink of extinction right now. So just remember, like
tigers, elephants, and rhinos, even the mightiest animals
are at risk of extinction if we're not careful. Have you ever stopped to
watch two animals interact with each other and wonder,
can animals actually talk to each other? Let's find out on today's
episode of Colossal Questions. Experts say that all
languages from cultures all around the world are
rooted in turn taking. One person talks. Then the other responds
back and forth. We just call that,
well, talking. And it might seem basic. But it forms the foundation
of all languages. And believe it or not, most
animals across the globe tend to turn take
with each other too. There's still lots
of research that needs to be done on how
animals talk to each other. But experts are confident
that animals definitely can communicate with each other. In fact, anyone who spent time
around a pet probably already knows this. Dogs and cats respond to
commands or even specific words that they can understand. They can also talk back to you. Most pet owners can tell when
their dog is hungry or tired or needs to pee
or wants to play. All of that is your
pet talking to you. All the different
sounds that animals make are a form of language-- barks,
meows, croaks, bleats, tweets, roars, and songs are all
ways for those animals to communicate. According to
experts, prairie dogs have one of the best
vocabularies of any animal out there. They don't just
use words or sounds to tell other prairie dogs
that there's a looming threat. They can also use more
expressive words that let the others know the
size, shape, threat level, and oncoming speed of
an approaching creature. In most cases, experts
are still trying to understand what animals
are saying to each other. But it's pretty clear
that animals everywhere are always talking. So do animals talk
to each other? Absolutely. It just might be a while before
we have any good idea what they're saying. [barking] [music playing] Ah, huh, what? Oh, sorry, guys. I was having a
dream about my dog. Speaking of dreams,
have you ever stopped and wondered what's
going on in your furry friend's head while it sleeps? Do animals have dreams
the same way humans do? Let's find out on today's
episode of Colossal Questions. [music playing] The hardest part about answering
this question for scientists is that, well, pets can't
tell us about their dreams. But, basically, everything we
do know about whether or not animals dream comes from what
we know about our own dreams. Each night about an hour or
two after you fall asleep, your eyeballs will
start darting around behind your closed eyelids. This stage of your
sleep cycle is called REM or REM sleep, which
stands for rapid eye movement. During this stage, your
body is powered down. But your brain is as active
as when you're awake. For humans, the REM stages
when dreaming begins. Many scientists have looked
at the brain activity of sleeping animals to try
and solve the mystery once and for all. What they found is that almost
all mammals and birds have a REM stage when they sleep. And cold blooded animals, like
reptiles, amphibians, and fish, don't. But the research
didn't stop there. Researchers at MIT
put rats on a track and measured their
brain activity while they move towards food
at the other end of the track. Once the same rats fell
into the REM stage of sleep, they measured their brain again
and saw identical patterns. This led scientists to
believe that the rats were dreaming about running
for food on the track. Many experts believe the
same thing is true for dogs. Like rats, pups likely
dream about their day to day lives and experiences. Pretty cool. Even cooler, the smaller
the dog, the more it dreams. Small dogs can have dreams
as often as every 10 minutes, while bull dogs can have an
hour or two between dreams. In another study, scientists
measured the brain activity of singing birds. Once the birds fell asleep,
the researchers measured again. And you guessed it,
the brain activity was almost exactly the same. The experts still
don't know for sure. But this has led many to believe
that the birds are either dreaming about singing or
they can hear their own song in their sleep. So does your little
pug muffin dream? Many experts think it's likely. So next time your dog
starts running in place while it's sleeping,
rest assured she's probably dreaming about
that great, fuzzy tennis ball in the sky. That's a good boy,
Mr. Sprinkles. [barks] [music playing]
