Lesson video

Hi, everybody.

It's Miss Simkin back again for your science lesson.

Thank you so much to all the children and parents who sent me pictures of you doing work or the work that you completed last week.

It was really great to see everybody working so hard! I'm very excited for our lesson today.

Today, we are going to be learning all about fossils.

And the lesson question that we're going to answer is this one.

We are going to answer the question: how do fossils provide evidence for evolution? So, last week we learned what evolution is and this week we're going to learn how fossils give us evidence that evolution is something that actually happened.

Before we start, we're going to do some recap from last time.

And when we do that recap, we'll go through the kinds of things that you were asked in your pre-lesson quiz.

So, well done if you had a go at that and well done if you got the answers right.

If you didn't, don't worry.

It's quite hard to remember something that you might have learned a week ago or maybe even longer, depending on when you were watching these videos.

So, don't worry if you didn't get the answers right 'cause we're going to go through the answers now.

So, before we start, these are the things that you will need for this lesson.

You will need a piece of paper or an exercise book; you'll need a pencil; a colouring pencil if you want to mark your work in a different colour; and you'll need a ruler, so that you can be really neat when we're drawing tables and labels.

If you don't have those things, then you can pause the video and go and get them now before we start.

Great, when you're ready, we're going to have a look at the structure of our lesson today.

So, this is what we will be covering today.

We're going to start with our star words: our key vocabulary like we always do.

Then, we're going to recap our learning from last lesson.

Then, we're going to look at how fossils are formed.

Then, we're going to think about what fossils tell us and then we're going to think about the things that are missing from the fossil record.

So, these are our star words for today.

The star words that are underlined on top are the ones that we will go through now.

And then by the end of the lesson, we will be able to define what the fossil record is.

Let's start with our first star word: species.

A species is a group of organisms that can breed together.

Lots of different types of organisms can be species, so we can have species of plants, species of animals, species of microorganisms. Our second star word is fossils.

Fossils are the remains of organisms that have been preserved in rock and we're going to learn how those are made today.

Our next star word is evolution.

This is a word that we learned last lesson.

So if you remember the definition for evolution, say it to your screen now.

Evolution is the process by which living things gradually change over time.

Well done if you got that right! And there's a little picture here to remind us but we're going to go through that in a second in more detail in our recap section.

So, last lesson we learned that all organisms have their own characteristics.

If you can remember the definition for characteristics, say it to your screen now.

A characteristic is a physical feature of an organism.

So, for example, hair colour or fur colour, like these little puppies in the picture.

They all have different coloured fur, which brings us on to the next thing we spoke about last lesson, which was variation.

If you can remember the definition for variation, say it to your screen.

Variation is.

? Variation is the differences between organisms of a species.

Next, we spoke about adaptation.

If you can remember the definition of an adaptation, say it to your screen.

An adaptation is.

? A characteristic that helps an organism to survive in its environment.

And last lesson we learned about different finches' beak sizes and how some finches were adapted to have different shaped beaks in order to survive and to get particular types of food.

And then we looked at evolution.

We've already recapped this definition this morning.

If you can remember it, say it to your screen.

Great! Evolution is the process by which living things gradually change over time.

Now, we learned the steps of evolution last week.

So, we're just going to go through them again now.

So, step one was not all individual species, or not all the individuals of a species are exactly the same.

There is variation between them.

So, with our example last week, the variation between the finches was that they had different size beaks.

Step two: the individuals who are best adapted to their environment are most likely to survive.

So, in our example last week, our finches that had the long thin beaks were most likely to survive because they could get the food out of the box.

Step three: these individuals are more likely to reproduce and pass on the useful adaptation to their offspring.

So, those finches are more likely to have babies that have the same adaptations as them: the long thin beaks.

And then step four: the individuals that were poorly adapted were less likely to survive.

So, the finches with the big thick beaks were less likely to survive on that island because they weren't very well suited to that type of food.

Then, step five: over time, the characteristics that help survival become more common and a species gradually changes.

Step six: given enough time, these small changes add up to the extent that a new species all together can evolve.

Now remember, when we learned about evolution, there were two things that we needed to make sure we didn't fall into the trap of thinking.

The first is that no organism chooses its adaptations.

The finches didn't get to choose what kind of beaks they have.

They were just lucky if they had the beaks that were well adapted.

And the second thing is that evolution happens over a really long period of time.

Thousands and thousands and thousands of years.

It's a slow, slow process.

In this part of our lesson, we are going to look at how fossils are formed.

So, I have some pictures up here on the screen and these represent the steps of fossilisation.

So, we're going to start with number one.

What I would suggest is that while I'm explaining this, you get your piece of paper and your pencil ready, and you write down some notes next to each step.

So, let's start with step one.

Have a look at the picture.

What do you think is happening in that picture? So, in step one, we can see that our dinosaur in this case has died.

Okay? So, we don't just have dinosaur fossils but the dinosaur is the example that we have for this one.

It looks a bit to me like a Tyrannosaurus Rex 'cause I can see its small arms. So, in step one, our animal dies and then its flesh decays So, in step one, our animal dies and then its flesh decays and its skeleton starts to be buried by sediment.

Okay, that's what's happening in step one.

So if you haven't already, I would now pause the video and make some notes on step one.

So, animal dies, flesh decays, and the skeleton starts to be buried by sediment.

Then, in step two, the sediment that's surrounding the skeleton starts to thicken and turn to stone.

So you can see in this picture, you can still see part of the skeleton poking out but the sediment around it is starting to thicken and turn to stone.

Then, in step three and step four, you have two pictures that look really similar and in those pictures, we have more and more layers of sediment being added we have more and more layers of sediment being added and then more rock forming.

This is how sedimentary rock is made, which you might remember from your learning of the rock cycle but there's something else going on in picture three and picture four that we can't see from those pictures.

So, I'm going to model to you using some objects that I have So, I'm going to model to you using some objects that I have what's actually going on there to see if it can help us understand it a little bit better.

So, in order to do that, I'm going to need to get my science box.

Let me go and grab it.

So, let's see what we have in our science box today.

So, let's see what we have in our science box today.

Ooh, actually, before we start, I've got a fun fact about penguins for you.

A new one today.

Did you know that penguins swallow lots and lots of saltwater by accident when they're diving for fish, so they have a special gland behind their eyes that helps them to filter that out.

So, it filters the salt out of the water and then they get rid of the salt by sneezing it's out.

So, penguins sneeze salt, which is really cool.

Okay, back to fossilisation, let's see what we've got in our box to help us demonstrate this.

So, I've got a hair scrunchie, I've got some cupcake cases, So, I've got a hair scrunchie, I've got some cupcake cases, and I've got a cookie cutter mould, okay? And those things are going to help me, hopefully, explain what is happening here a little bit better, okay? Like always when we do a science demo, you're going to have to use your imagination and imagine that the objects that I'm using are something else, okay? So, we're going to start off with this being my animal that has died, okay? with this being my animal that has died, okay? So, we can imagine that this is my dinosaur.

Okay, the outside - the scrunchie - is the dinosaur's flesh, so the soft parts of its body and this cupcake case that I've just put inside, that represents its skeleton, so the hard parts of its body, okay? In step one, the flesh decayed from my animal, okay? In step one, the flesh decayed from my animal, okay? So, the flesh is gone.

I've taken the scrunchie off.

Then in step two, the sediment builds on top of it, so we've got our layers and our layers and our layers, and they start thickening and turning to stone.

Now, this is what's happening in step three, which we can't see clearly from our picture.

In step three, the skeleton dissolves and we're left with a mould.

the skeleton dissolves and we're left with a mould.

So, a hole basically, a gap, that is the shape of the skeleton.

So in this case, my skeleton was circular, so I've been left with a circle hole or mould but if it was an actual dinosaur, then its skeleton would be dinosaur shaped and we'd be left with a dinosaur-shaped hole or mould, okay? So, this is step three.

We have a mould that's in between all my layers of rock.

Then, in step four, something really cool happens.

The minerals in the rock start to crystallise inside the mould and they form a cast, start to crystallise inside the mould and they form a cast, so we're now inside the space where my skeleton was, have a cast made of hard solid minerals that's the shape of the original mould.

Then, eventually in step five, the fossil is exposed at the surface.

So, over millions of years, the layers of rock build up and then over millions of years the layers of rock erode, and my fossil is exposed at the surface.

And that's when they get discovered by scientists who are fossil experts, so palaeontologists are the kind of scientists who go fossil hunting and that's when they get discovered, when they get exposed on the surface and then we can study them.

So, hopefully that demonstration shows a little bit more clearly what's happening in step three and step four.

Let's go back to those now, in case you didn't have time to make notes while I was explaining it.

So, in step three, that's when the skeleton dissolves, the skeleton dissolves and we're left with a mould.

Then, in step four, that's when the minerals crystallise and a cast is formed.

And then in our last step, step five, the fossil is exposed at our earth's surface.

Great! So, I hope you managed to make some notes on that.

If not, then just pause the video now and jot some down.

And when you're ready, we're going to have a look at this question.

I would like you now to put these steps in the correct order, so you don't need to write the whole sentence out.

You just need to write the letter.

So, if you think that C should be first, then you need to write C in the correct order.

No, actually, you need to write C first and then the letters afterwards.

I'm going to make my screen full, so that you can see it really clearly.

And you can now pause the video and answer the questions here.

Great! When you ready, we'll mark our answers.

So, let's see if you got these correct.

Well done if you did! This was the correct order of the letters: E-C-B-D-A.

So, the first step was the animal dies, its flesh decays, and its skeleton is buried by sediment.

Step two: the sediment surrounding the skeleton thickens and begins to turn to stone.

Then, step three: the skeleton dissolves and then it leaves behind a mould.

And then, our minerals crystallise inside the mould and a cast is formed.

And lastly, the fossil is exposed at the surface of the earth.

So, well done if you got those correct! That brings us to our next section.

Now we've learned how fossils are formed, let's learn what they tell us.

How do they give us evidence for evolution? How do they show that organisms change over time? So, Darwin's theory of evolution suggested that different species will change over time.

And fossils, they show us a range of living creatures from across different times in the past.

And this is known as the fossil record but how can we know when each fossil is from? How would we know how long ago those dinosaur fossils were formed? Well, rock often forms in layers, just like we saw in our example of the fossilisation process.

Rock forms in layers.

And a rule that can help us figure it out is that rock often forms in layers where the highest level of rock is the rock that's been most recently made.

So, the rock up here is new rock and the rock down here is old rock, which makes sense, doesn't it? Because if we're going to make our sedimentary rock like this, then we have to put down this layer first at the bottom, so this is going to be our oldest rock.

So, that means that the oldest fossils are in the oldest rock, so they're in the deepest rock down here and our newest fossils are in the newest rock, so they're up here.

That means that we can study and figure out when those fossils would have come from and which period of time those organisms would have been alive in.

So, this is our definition of the fossil record.

Say it with me because saying things out loud can help us to remember them.

So, the fossil record is a collection of fossils found across different ages of rock.

Great, good job! Now, I want you to have a close look at this picture.

In fact, I'm going to make it full screen, so that we can all see it really clearly.

This picture shows us how horses have developed over time.

This picture shows us how horses have developed over time.

So, you can see at the bottom we have the oldest fossils.

So, you can see at the bottom we have the oldest fossils.

You can see a picture of the fossil, which looks like the skeleton of the animal.

And then next to it, a picture of what we think the animal would have looked like based on its skeleton.

Then, you can see as we go up the picture to the newer fossils, the skeletons, and therefore the animals change slightly over time until we get to the top, change slightly over time until we get to the top, the most recent fossils, which look the most like horses that we have alive today.

I wonder if you can have a close look and think about what the similarities are between these oldest fossils and the animals represented by them and the newest ones.

What are the similarities and what are the differences? So, something I've noticed is that the older horses or the ancestors of horses are much, much smaller than the newer ones.

And if I look at the shape of their skulls over here, I can see that the shape is changing to become more elongated and more triangle.

Well done if you've spotted those things too or something else that was different! I'd like you to have a go now at answering these questions, please.

So, for these questions, you need to fill in the gaps.

So, I'm going to read them to you.

And then I'm going to ask you to pause the video and fill in the gaps.

So, the collection of fossils found across different ages of rock is known as the ____? Overall, the deeper in the ground we go, the ____ the rock.

This means that the fossils found are ____? And then overall, the closer the rock is to the surface, the ____ the rock is.

This means that the fossils found here are ____? You can now pause the video and complete the task.

Great! Once you're finished, let's check our answers.

Well done if you got these correct! You can give yourself a tick.

If not, it doesn't matter, mistakes are how we learn.

Just correct your answer using the answers on the screen, please.

So, the collection of fossils found across different ages of rock is known as the fossil record.

Overall, the deeper in the ground you go, the older the rock.

This means the fossils here are older.

And overall, the closer the rock is to the surface, the newer the rock.

This means the fossils found here are younger.

Well done if you've got those right! That brings us to the last part of our lesson.

What's missing from the fossil record? So, unfortunately we don't have a fossil So, unfortunately we don't have a fossil of every animal that ever existed.

It would be really great if we did but we don't.

There are lots of gaps missing.

And, in fact, we don't even have with all animals, a clear line of fossils from oldest to newest that show us how they changed, like those horse fossils we looked at.

There are lots of fossils missing from the fossil record and we're going to learn why that is.

So, this is a diagram of the rock cycle.

I'm going to make it a little bit bigger.

And you may have learned about the rock cycle in your science learning before.

If you haven't, don't worry.

There are just three main things that we need to know from this is that in the rock cycle, that we need to know from this is that in the rock cycle, rocks change and they get destroyed.

Rocks can be destroyed in three main ways: they can erode, which means they rub away; they can melt when they get heated; and they can fragment, they can break into little pieces.

Now, when those rocks get destroyed, if there are any fossils in the rocks, they will be destroyed as well.

So, fossils can be destroyed because they can erode, fragment, or melt.

Okay, so that's one reason why there are some fossils missing from the fossil record because they've been destroyed.

The other reason is that sediment The other reason is that sediment has to cover organisms' remains.

So, in our example, this dinosaur died and then it got covered by lots of layers of sediment but this has to happen before the organism has completely decomposed.

And that doesn't always happen.

Lots of animals will decompose before they are able to be covered with sediment and then their fossils don't get made because their skeleton isn't able to make that mould in the rock where the fossil will then take shape, okay? So, there are two reasons why we have gaps in the fossil record.

Number one: fossils can be destroyed.

And number two: not all organisms get covered by sediment before they decompose.

Let's see how well you were listening.

Can you answer these questions and fill in the gaps to explain why some organisms are missing from the fossil record? So, I'll make it full screen so it's really clear.

In the rock cycle, some rocks that contain fossils are ____? Most organisms that have lived in the past are not seen in the fossil record because ____? Pause the video and complete the gaps.

Great! When you're ready, let's go through the answers.

You could have written this in your own words, so if you've got the idea right, that's fine.

Give yourself a tick.

You don't have to have written exactly what I have.

In the rock cycle, some rocks that contain fossils are destroyed, or you could have written eroded, melted or fragmented.

Also, most organisms that have lived in the past are not seen in the fossil record because only a small amount of organisms become fossils because only a small amount of organisms become fossils and some fossils are destroyed, okay? Those are the two main reasons.

You can give yourself a tick if you've got either of those.

You might even have gone into more detail than me and written why some organisms don't get made into fossils because they don't get covered in sediment before they decompose, okay? Well done! That brings us to the end of our lesson.

So, just before we finish up and you go onto your post-lesson quiz, let's recap our key words from this lesson.

A species is a group of organisms that can breed together.

Fossils are the remains of organisms that have been preserved in rocks.

Evolution is the process by which living things change over time.

There's our picture to remind us.

Our finches' beaks changing over time.

And, the fossil record is a collection of fossils found across different ages of rock.

Well done for all your hard work today! I have had so much fun with this fossil lesson and I cannot wait until our lesson next week.

I hope you have a lovely day and see you soon.

Bye!.