[♪ INTRO]
Hey there!
Squeaks and I are learning about things that lived in the past.
Squeaks made this pretend time machine, so we can imagine
what it’s like to go back in time and see things that lived long ago!
Our pretend time machine is fun to use.
But we can also look at the way things are right now
to understand what life was like in the past!
Did you know that even though many old forms of life aren’t around any more,
they have relatives that we can see today?
[Squeaks squeaks]
Yep! Like dinosaurs.
Even though dinosaurs went extinct a long time ago,
meaning there are none alive on Earth right now…
...they are related to animals that are still alive today!
Can you guess what they are?
[Squeaks squeaks]
They’re birds!
Birds are actually relatives of dinosaurs!
[Squeaks squeaks]
You’re right!
It is pretty cool. But it’s not the only example!
How would you like to see a very early relative of some of Earth’s bugs?
[Squeaks squeaks]
This is a fossil of an animal called a trilobite.
Fossils are clues left by animals and plants a long time ago.
And they can help us understand what life was like way back then.
From those clues, we know that trilobites lived on Earth
millions and millions of years ago, even before dinosaurs lived!
That’s a long time!
[Squeaks squeaks]
You’re right, Squeaks.
It’s hard to think about all the time that’s passed
between when trilobites lived, and today.
But I have an idea!
Let’s use our time machine!
[Squeaks squeaks]
And you can pretend, too!
Even though we can’t really travel
through time, we can use our imaginations.
Scientists use their imaginations all the time
to help them solve problems.
Okay, Squeaks, are you ready?
[Squeaks squeaks]
Then let’s go!
We’ll pretend to travel back to the time when most trilobites lived,
and imagine what it was like to live on Earth then!
Here we go!
[Time machine noises]
Ok, Squeaks, I think we’re there!
Scientists think that Earth was warmer
back then than it is now.
And almost all life at that time lived in the ocean.
In fact, scientists think that most of
the Earth at the time was covered in ocean.
So I hope you brought your snorkel!
[Squeaks squeaks]
Yes! The ocean certainly looked a lot
different when the trilobites lived.
A lot of land that’s dry now… including
where the Fort is... was under water.
But the Fort’s not under water any more,
thank goodness.
[Squeaks squeaks]
The Fort is on land now because the Earth is always changing.
The kind of change I’m talking about isn’t like what happens when wind
blows up a dust cloud… or water washes away some mud from a creek bank.
This change happens over a long period of time… and happens really slowly.
We couldn’t see this kind of change if we tried!
But those changes are why the Earth’s oceans look
a lot different today than they did when trilobites lived.
[Squeaks squeaks]
Good question, Squeaks!
Squeaks wants to know how we know all of this!
One reason we know trilobites existed at all is because of fossils like this one.
We can look at both the fossils themselves,
and the things we find near them, to understand the clues.
We’ve found fossils of other animals that lived in the ocean in
the rocks around the trilobites...so we know that trilobites lived in the ocean too.
Let’s take a look and see what we can learn from the actual trilobite fossil!
We can see how big it is.
This one is about as big as my hand.
But we’ve found all different sizes of trilobite fossils.
Some are about the size of a penny.
But others are much bigger:
just a little shorter than the size of two bowling pins laid end to end!
And we also see what it looked like.
It has lots of body structures called segments.
See these little sections, here?
That means the trilobite’s body was
divided into many parts that all worked together.
Notice anything else about the trilobite, Squeaks?
[Squeaks squeaks]
Yes, the segments look pretty tough, don’t they?
Kind of like they have a shell.
Soft body parts don’t usually make fossils that look like this one.
So we think trilobites had tough shells to protect them.
Scientists put together clues like these to figure out
what kind of animals trilobites are, and if they are related to animals we see today.
They look for patterns by trying to find out
how things are the same and how they’re different.
Some animals, like this roly poly, have
segments, and they have a hard outer shell.
These are reasons why we think that trilobites
are relatives of animals like insects and roly polys.
In fact, we think they are part of a group called arthropods.
Those are animals with segments and tough shells,
like insects, spiders, roly polys, and crabs.
There are other patterns we can see, too.
Like, arthropods have many legs.
It’s hard to see from this fossil,
but we think trilobites had many legs too.
So that’s another pattern.
[Squeaks squeaks]
Oh, fun idea!
We’re going to go outside to see if we can spot
any arthropods to compare to our trilobite fossil!
Thanks for joining me here at the Fort.
If you want to keep learning and having fun with Squeaks, me,
and all our other friends, be sure to hit the subscribe button,
and we'll see you next time on SciShow Kids!
[♪ OUTRO]