Mysterious Trilobites! | The History of Life! | SciShow Kids

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 anymore, they have relatives that we can see today? 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? They're birds! Birds are actually relatives of dinosaurs. 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? 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! 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! 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? 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! Okay, 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. 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 underwater. But the fort's not underwater anymore, thank goodness. 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. 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 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? 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-polies. In fact, we think they are part of a group called arthropods. Those are animals with segments and tough shells like insects, spiders, roly-polies, 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! 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!