Lesson video

Hello, my name is Mrs. Mehrin, and I'm so excited to be learning with you today.

We are going to be learning about how living things have changed over time.

Let's begin.

Your lesson outcome for today is; I can use fossil evidence to describe how living things have changed over time, and this is from the unit "Evolution and Inheritance." Now, I know that sometimes learning can be a little bit challenging, but that's okay, because it just means that we're going to work really hard together, and we're going to learn lots of fabulous new things.

Now, here are your five key words for today.

You don't need to pause the video and write these down, because I am going to be going through these throughout the lesson.

However, if you feel that it does help you, you can pause the video now and have a go.

Fantastic, well done.

And here are the definitions for those five keywords.

Again, you don't need to write these down.

However, if it does help you, you can pause the video now and do that.

Fantastic, well done.

Now, today, your lesson has been split into three parts.

Let's begin with the first part, "Rock Layers." Now some children are looking at a picture of mountains.

So we've got Aisha, Izzy, and Jun.

Aisha says, "Why does it have layers like that?" So if you look closely at the picture, you can see that there are different colours throughout the mountain, it looks like there are layers there.

Izzy said, "I think it's because some of it used to be underwater." And Jun said, "I think it's because the layers are different types of rocks." What do you think? I'll give you five seconds to think about your answer, off you go.

Fantastic, well done.

Now the mountain is made of something called sedimentary rock.

And sedimentary rock is made when layers of sediment, which is small pieces of rock, sand, and minerals, it's when they build up over time.

And the different combinations of different types of sediment often make each layer look different.

And each layer of sediment is built up on top of the one beneath it.

And this means that the layers at the bottom of the rock are the oldest, and the layers at the top are the newest.

So here we've got some arrows to help here.

So those ones that are older are the ones at the bottom, and then the newer rock is at the top.

Now, the layers that we can see above earth's surface were formed over millions of years underwater.

And as the earth changed over time, these rocks have been pushed upwards to become mountains or cliffs.

There are also layers in the sedimentary rock beneath our feet, just like the mountain, but they're hard to observe.

So sometimes these layers can be seen when we dig down into the ground.

So here we have a picture of archaeologists digging for evidence.

Now let's do a quick check-in of your learning so far.

Which of these is the oldest layer of rock? Is it A right at the very top, B in the middle, or C at the bottom? I'll give you five seconds to think about your answer.

Off you go.

Fabulous, well done, the answer is C.

The rock that's at the bottom, the layer of rock at the bottom is always the oldest.

Now geologists are scientists who study rocks to learn more about our planet and its history.

And so we have a geologist here inside a cave.

Now, how might these rock layers be useful to them? So if they were going to be looking at the rock layers, how might they be useful for geologists who wants to study rocks and learn more about the planet and our history? What do you think? I'll give you five seconds to think about your answer.

Fantastic, well done.

So by looking at the composition, so how something's made up.

So by looking at the composition of different layers of rock, geologists can learn about what is happening on earth at different times.

And evidence can be found inside the sedimentary rock.

And they can tell us about major events that might have happened such as a volcano erupting, or there being some floods or meteorite impacts.

So within this sedimentary rock, geologists can work out what might have happened, which I think is absolutely incredible.

Now, let's do a quick check-in of your learning.

Why are rock layers useful to geologists? Is it because A, they can be used to predict weather patterns? B, they can be used as evidence about what happened on earth at different times, or C, because they can be used to create medicines? So again, I'm going to give you five seconds to think about your answer, off you go.

Fantastic, well done, the answer is B.

They can be used as evidence about what has happened on earth at different times.

So remember things like volcanic eruptions, meteorite impacts, all of those kind of things, flooding as well.

All of this evidence can be found inside sedimentary rocks, which might tell geologists what's happened.

Now we can work out the age of a fossil by looking at the age of the rock layer it was discovered in.

Older fossils are discovered in deeper rock layers, while newer fossils are in rock layers closer to the surface.

So here we have the older fossils towards the bottom, and the newer fossils at the top.

Now, geologists can use layers in rock to learn about life on earth at different times throughout history.

So they can look at the layer in which fossils are found to work out roughly when that organism was alive.

So fossils that are found in the deepest layers, so those right at the very bottom were formed by living things that were around long, around longer than those that were found on the top layers.

So if we have a look at this illustration of rock layers, we can see that all of those layers are showing different fossils, which geologists can use to help them work out when these animals or when these organisms were alive.

True or false? A fossil found in layer A would be older than a fossil found in layer C.

Is that true or false? So fossil found in layer A, so at the very top, would be older than the fossil found in layer C, which is right at the very bottom.

I'll give you five seconds to think about your answer.

off you go.

Fabulous, well done, the answer is false.

Now let's see if you can justify your answer.

Is it because A, the lower layers of rock are older than the higher ones? Or B, the lower layers of rock are around the same age as the higher ones? Again, I'll give you five seconds to think about your answer, off you go.

Fantastic, well done, the answer is A.

The lower layers of rock are older than the higher ones.

Now, here is your first task.

I want you to read each statement, and I want you to decide whether it's correct or incorrect.

So A, layers in rock are caused by sediment building up over time.

B, the top most layers of rock are the oldest.

C, geologists can use the different rock layers to learn about what earth was like millions of years ago.

And D, fossils can only be found in the top layers of rock.

So I'd like you to read through A, B, C, and D and decide whether or not you think it's correct or incorrect.

So I'd like you to pause the video here now and have a go at that activity, off you go.

Fantastic, well done.

So let's go through the answers.

So A was correct, B was incorrect, C was correct, and D was incorrect.

Well done.

Now, the second part of your activity, I want you to rewrite these statements so that they're correct.

So I'd like you to rewrite these statements so that they're correct.

So B, the top most layers of rock are the oldest.

So I want you to rewrite that so that it's correct.

And D, fossils can only be found in the top layers of rock.

So again, I'd like you to rewrite that too so that it's correct.

So I'll give you some time now, I'd like you to pause the video and have a go at that activity, off you go.

Fantastic, well done.

So you may have written something along the lines of the deepest layers or the ones at the very bottom of the rock are the oldest, and fossils can be found in different rock layers.

Well done.

So now we are on to the second part of our learning, which is, "Life on earth throughout time." So geologists can work out the age of a fossil by looking at the age of the rock layer it was discovered in.

And fossils found in deeper layers, so those at the bottom, are older than those found in layers that are nearer the top.

And this helps us to understand which living things were alive at the same time.

So for example, Stegosaurus fossil is always found in much deeper layers than a Tyrannosaurus Rex fossil.

And this tells us that the Stegosaurus existed a long time before the Tyrannosaurus Rex.

Which is really interesting, isn't it? Now the layer or layers that a fossil appears in can tell us when the living thing was alive, and if and when it became extinct.

So dinosaur fossils are found in deeper layers of rock because they've been extinct for a very long time, around 66 million years.

And woolly mammoth fossils are found in high layers of rock because they lived and became extinct only more recently.

So it's only been about 4,000 years since the woolly mammoth became extinct.

Now, as more and more fossils are discovered, scientists noticed a pattern in the types of organisms that were alive at different times.

And this diagram here shows some examples of the types of fossils that they found in each of the layers.

So I want you to think really carefully, what do you notice about the types of fossils that have been found in each of the layers? So if you need to, you can pause the video here so that you can have a really good look at this diagram here.

Off you go.

Fantastic, well done.

So scientists notice that fossils of the simplest organism were found in the oldest rocks.

And the more complex organisms in the newest rock.

And you can see that when you look at the diagram, and you look at how these organisms were made up, you can have a look at the skeleton, for example, you can really see how they are getting more and more detailed, and more complex the higher up you go.

Now let's do a quick check-in of your learning so far.

Which of these statements about fossils is correct? A, fossils of the simplest organisms are found in the oldest rocks.

B, fossils of the most complex organisms are found in the oldest rocks, or C, fossils of the simplest organisms are found in the newest rocks.

So I'll give you five seconds to think about your answer, off you go.

Fantastic, well done, the answer is A.

Fossils of the simplest organisms are found in the oldest rocks.

Well done.

Now, animals with simple structures such as invertebrates like trilobites and ammonites were found much deeper in rock than animals with more complex structures, such as mammals and reptiles.

So here we've got an ammonite shell fossil and the woolly mammoth skeleton fossil.

And you can see just how much more complex the woolly mammoth skeleton fossil is, compared to the ammonite shell fossil.

Now, what do you think that this tells us about how a life on earth has changed over millions of years? So if you were a geologist and you're going to think like a geologist now, think really carefully, what does it tell you about how life on earth has changed over millions of years? So I'll give you five seconds to think about your answer, but if you need longer, just pause the video here and then come back once you are ready.

Off you go.

Fantastic, well done.

So millions of years ago, living things on earth had simpler structures and over time they became more complex.

So for example, only recent fossils of plants have flowers, which tells us that earlier plants didn't actually have flowers, which is incredible.

And mammals have more complex structures and body systems than all other types of animals.

Mammal fossils only appear in the very top most layers of rock, telling us that they are the most recent type of animals to have developed on earth.

Now let's do a quick check-in of your learning so far.

So it says, complete the sentence.

Living things have developed- A, more complex structures over decades.

B, simpler structures over decades, C, more complex structures over millions of years, or D, simpler structures over millions of years.

So I'll give you five seconds to think about your answer, off you go.

Fantastic, well done, so the answer is C, more complex structures over millions of years.

Okay, so here is task B.

I want you to order the layers of rock and fossils correctly and then explain why you've chosen this order.

So there's invertebrates, reptiles, and dinosaurs, and mammals, and fish, and amphibians.

Now what I'd like you to do is to pause the video here.

If you need to go back one slide to have a look at the other two, that's absolutely fine.

And then once you are ready, come back and we will carry on with our lesson today.

Off you go.

Fantastic, well done.

So here, Jacob has ordered them.

And he said, "I ordered them so that the simplest organisms were at the bottom, then each layer becomes more complex as you move upwards." So he's got the invertebrates at the bottom, followed by the fish and amphibians, the reptiles and dinosaurs, and the mammals.

Fantastic.

Now we are onto the final part of our learning today, which is "Modelling rock layers." Well done, you have been working so hard.

Now, scientists use models to help observe and explain things that are impossible for us to see or experience.

Some models can be 3D objects that we can touch or they can be diagrams. So this diagram of rock layers is a scientific model to represent the real thing.

And this model is useful because it helps us to understand and visualise the rock layers beneath our feet.

So Andeep says, "This model helps me to understand that there are lots of different layers of rock and each one has different fossils inside." And Lucas says, "I can see that the organisms become more complex, the higher up the layers are." Now let's do a quick check-in of your learning.

Why do scientists use models? Is it because A, they're fun to create? B, they're more interesting than just reading words.

And C, they help us to see and understand things that we can't see or experience for ourselves? So I'll give you five seconds to think about your answer, off you go.

Fantastic, well done, the answer is C.

They help us to see and understand things that we can't see or experience for ourselves.

Now, most models used in science are not perfect.

They may be very similar to the real thing, but there are still differences.

So I want you to think really closely here and think carefully.

What differences can you see between the diagram and a real picture of a cliff? So if you need to, you can pause the video here, otherwise I'll give you five seconds to think about your answer, off you go.

Fantastic, well done.

So Laura says, "You can't actually see the fossils in the real cliff." Sam says, "The layers in the real cliff are different sizes to each other." So if you looked at the model, all of the layers were of equal size.

And Alex says, "The real layers are not as clearly different from each other as the ones in the model." Now understanding how a model is different to the real thing helps us to understand the real thing itself.

Let's do a quick check-in of your learning.

It says, are these statements about scientific models true or false? A, models are identical to the real thing they represent.

B, models help us to understand things that are impossible to see.

C, models have to be objects that we can touch.

And D, we can use models to represent different fossils in layers of rock.

So I'll give you five seconds to think about your answer.

Once you're ready, you can come back and we can carry on with our lesson, off you go.

Fantastic, well done, the answer is false for A, true for B, false for C, and true for D.

Now, Jacob has created a 3D model to represent the different fossils that can be found in layers of rock.

And he has used different coloured paper to represent the rock layers, and sweets to represent the different types of fossils.

Now, what makes Jacob's model a good representation of the real thing, what do you think? I'll give you five seconds to think about your answer, off you go.

Fantastic, well done.

So Sam says, "I can see there are different layers containing different types of fossils." And Alex says, "The sweets on the older layers have a more simple structure than the sweets on the newer layers, just like fossils in real rock layers." Now, how do you think Jacob's model is different from the real thing? Again, I'll give you five seconds to think about your answer, off you go.

Fantastic, well done.

So Andeep says, "The layers wouldn't really be as evenly sized." And Jun says, "Real fossils are not made of sweets." Now here is task C, it says create a model showing layers of rock and the different types of fossils within them.

Your model could be a diagram, or it could be something that you make.

So Laura says, "I'm going to use collage materials to make my model." Sam says, "I'm going to draw a diagram," and Alex says, "I'm going to use sand and soil to make my layers and stick on animal toys to represent the fossil." So I'd like you to pause the video here and have a go at this activity, off you go.

Fantastic, well done.

So Sam drew a diagram, and she asks, "Does it have any similarities to your model?" So have a look at your model and have a look at Sam's diagram, what do you notice are the similarities? Off you go.

Fantastic.

So you may have said that yours also starts with the simpler organisms at the very bottom in the deepest layers, and then slowly work up and they become more complex.

Now I want you to explain how your model is like real rock layers and fossils, and explain how it's different to the real thing.

So I'll give you some time now to have a go at that activity.

Once you're ready, come back to our lesson and we will continue, off you go.

Fantastic, well done.

So Sam says, "My diagram is similar to the real thing because it shows different layers in the rock, with fossils of more complex organisms at the top, and less complex ones in the older layers.

It's different to the real thing because it's flat, it's a flat 2D image, and real rocks are 3D.

The real layers probably wouldn't be as evenly sized as mine, and there would be lots more different types of fossils than just the ones I've drawn." So we are now onto the summary of our learning for today's lesson.

Layers of sedimentary rock build up over time on earth.

Geologists can study these layers and the different fossils found in them to learn about the history of life on earth.

Fossils of the simplest organisms are found in the oldest rocks.

More complex organisms are found in the newest.

Models, can be used to represent different layers of rock, fossils in rock over time.

Well done for today, you have worked really, really hard, I'm so proud of you, and you have tried your absolute best, well done.