Hello, and welcome to this lesson from the Oak National Academy.

Today's lesson is taken from the unit, adaptations, competition, natural selection and evolution, and the lesson title is Understanding Time Scales.

We're gonna be talking about some really big numbers today, and at first you might be surprised.

Why are we talking about numbers in the science lesson in a biology lesson of all things.

Biology is the study of living things.

What do huge numbers like million and billion have to do with biology? Well, this lesson supports the other lessons of the unit because the other lessons in this unit will be discussing events in biological history that happened millions and billions of years ago.

Numbers that are really, really, really big are very difficult for us to get our brain around.

We can hear huge numbers every day.

Maybe such and such a country are in billions of pounds of debt, billions of dollars of debt.

What does that actually mean? What's a billion? What's a billion dollars? Today's lessons, there's some context to those numbers, so hopefully when you hear them, especially when we're talking about periods of time, you'll have a sense of, right, okay, that happened in the millions of years ago, that happened in the billions of years ago.

I'm Mrs. Wheat, and I'll be your teacher for today's lesson.

By the end of today's lesson, you'll be able to describe key events in the history of Earth and distinguish between billions, millions, and thousands of years ago.

Let's have a look at our keywords for our lesson.

There are four keywords for today's lesson, billion, thousand, million and evolution.

Before I show you the definitions for those keywords, I just wanna make sure that you knew that you don't need to try and memorise all these definitions right now.

I'll stop talking for five seconds so that you can read them through if you want, or if you'd like to copy them down, maybe pause the video and then click play when you're ready to resume the lesson.

So here are the definitions.

Today's lesson is in two parts.

First of all, we'll talk about those numbers there, thousand, million and billion.

And I'll try and give you some context for just how big those numbers are.

And then in the second half of the lesson, we'll talk about the history of Earth.

So some key events in the history of Earth.

But first of all, let's talk about thousand, million, billion, Based on the evidence available, scientists believe that the Earth is 4.

5 billion years old, and we'll talk about in the second half of the lessons, some of the evidence that scientists have for that belief.

So 4.

5 billion, that's such a large number.

It's really difficult to actually comprehend, to wrap your head around what that means.

So we're gonna spend some time now in the first half of the lesson, thinking about how big is that number? What does that mean? Let's start with the smallest and work our way up.

So let's go with 1,000.

So 1 with three zeros at the end of it, we split it up, it's 10 x 10 x 10, a hundred times bigger than 10, 10 cubed.

There's lots of different ways of expressing 1,000.

But in terms of the history of the Earth, thousands of years, how long ago was that? Is that recent? Compared to the age of the Earth? We can often think about ancient civilizations as being a very long time ago.

So the ancient Greeks, the ancient Romans, the ancient Egyptians, but compared to the age of the Earth, 4.

5 billion years, all those civilizations are very recent indeed, the earliest human civilizations came into existence roughly 6,000 years ago.

So the Parthenon, you'd find this in Athens in Greece, was built roughly 2,500 years ago.

The Great Sphinx in Egypt built roughly 4,000 years ago.

This is a preserved writing on a wall from an ancient civilization called the the Sumerians, and they're one of the first civilizations that we have evidence of assisting around 6,000 years ago.

So all of these civilizations, all of civilised human history occurred in the last few thousands of years.

That's not really that much time compared to we're saying that the Earth is 4.

5 billion years old.

So let's go back now before human civilization, but still talking about human beings.

So modern humans, our species, Homo sapiens, first appeared approximately 350,000 years ago, and scientists know this from studying fossils of human skeletons.

So what is 250,000 compared to 4.

5 billion? It really doesn't feel like that much.

We're gonna do a little bit of maths to help us get more of an understanding and context for how different these numbers are.

So how many minutes would it take to count to 100? We'll start small if you said a number every second.

So it would take 100 seconds.

Every 60 seconds is 1 minute.

So 100 divided by 60 equals 1.

7, which means there are 1.

7 minutes in 100 seconds.

So it would take just under 2 minutes to count to 100.

Okay, so we've been talking about thousand and thousands.

How long would it take to count to 1,000 if you said a number every second, look through my work example on the other side of the screen and have a go at calculating how long it would take to count to 1000 if you said a number every second, I'm not gonna say anything now for five seconds, but if you want some more thinking time, pause the video and click play when you're ready to see the answer.

Okay, let's go through the answer.

It would take 1,000 seconds.

Every 60 seconds is 1 minute, which means that there are 16.

7 minutes in 1,000 seconds.

So it would take just under 17 minutes to counter 1,000.

Okay, have that in your heads.

We're gonna move on.

We're gonna start talking about millions now.

Okay, so all of human civilization has occurred within the last 10,000 years, and all of human history has occurred within the last 350,000 years.

So what happened millions of years ago? What was going on? Let's look at that word a million.

So 1,000,000, or 1 with six zeros at the end of it, if you're gonna express that in terms of other numbers, that's 1,000 times greater than 1,000.

What does that mean? First of all, we'll talk about some things and events that happened millions of years ago.

So over the past hundreds of millions of years, complex multicellular, that's organisms that have more than one cell that make up their whole bodies, so we are made of like trillions of cells, human beings.

So yeah, we're talking about plants, we're talking about animals, those kinds of things.

So complex multicellular life has appeared and evolved on Earth in the past hundreds of millions of years.

So some highlights over the last hundred, few hundred millions of years, plants, plants made their first appearance hundreds of millions of years ago.

Dinosaurs, about 200 million years ago, made their appearance on the planet.

And then about 65 million years ago, they all died out.

And then mammals have appeared in the last hundreds of millions of years.

So again, we're talking before human history began.

Before there were any Homo sapiens, hundreds of millions ago, these things were just starting to appear.

Hopefully now you're starting to get a context of how different 1,000 years ago, I mean 1,000 years ago was middle ages, right? They didn't have iPads, they didn't have iPhones, but they still, they still had books.

They still wrote things reasonably similar time to now compared to 70 million years ago there are no human beings and dinosaurs were in charge.

Yeah? Okay, let's see if we can put some more context behind that number a million.

If you said a number every second, it would take just under 70 minutes to count to 1,000.

We've done that, or we calculated that already.

So how long would it take to count to a million? So I'll stop talking for five seconds, or you can pause the video if you want some extra thinking time and click play when you're ready to the answer.

So is it approximately 11.

5 minutes? Approximately 11.

5 hours? Approximately 11.

5 days? Okay, I wonder what you thought it is.

11.

5 days! That's how different a thousand and a million are.

If it takes you 17 minutes to say a thousand seconds, it would take you 11.

5 days to say a million seconds.

These are hugely different numbers.

Hopefully you're starting to get that impression now.

Let's take a look at a billion and how different that is.

So 1 billion, or one with nine zeros at the end of it, expressed another way, that's 1,000 times greater than a million.

So let's think about these numbers in terms of things we might be familiar with.

So 1,000, the average school in the UK has about a thousand, secondary school that is, has about a thousand students.

A million, that's the size of a city.

So Birmingham, the second biggest city in the United Kingdom that's got around a million people in it.

Think about how much space your school, maybe around a thousand people, takes up, a thousand students that is, not even, that's not even including adults in a lot of situations.

So have that in your heads, and now think about how much space does a city take up? Huge, way, way, way, way bigger.

Okay, a thousand, around a school, a million around a small city, an average size city, a billion, well, there's just over a billion people in countries like India, countries like China.

So again, a thousand people, secondary school, million people, the space that a city takes up, a billion people, some of the biggest countries in the world have a billion people in them.

These are really, really, really different numbers.

I'm not gonna make you do the maths for this.

I'm just gonna tell you, if you were to count to a billion, so remember counting to 1,000, took 17 minutes, counting to a million took, what was it, 11.

5 days.

So if you count to a billion, if you're saying a number every second, it would take you 32 years.

Okay, 11.

5 days a million, 32 years, a billion.

We're talking about a really incomprehensible amount of time.

Billions of years ago.

So these are some events that happened over the last few billion years.

So the formation of the Earth and our solar system about 4.

5 billion years ago, the first appearance of unicellular single-celled organisms that are made up of just one cell.

So the first appearance of unicellular organisms.

And also, bit later, but still billions of years ago, the first appearance of cell that had a nucleus.

So all of these were kind of key events that were happening in the billions of years ago.

Let's see if we understood that.

Which of the following happened billions of years ago? Is it a, the first dinosaurs appeared? b, the first cells appeared, c, the first human civilization, or d, the first fish appeared.

You can take five seconds now or pause the video if you need some extra thinking time.

Click play when you're ready to see the answer.

Okay, let's see how you did, it is b, the first cells appeared.

So the first dinosaurs appeared around 200 million years ago, not billions.

The first human civilization was only 6,000 years ago.

Super recent in terms of the age of the Earth, the first fish appeared again that's something that happened a few last few hundreds of millions of years ago.

Well done if you got that right.

Let's have a go at our first practise task for today's lesson.

Place these events in the most suitable time periods in the table.

So we've got three columns to our table.

Did these things happen billions of years ago? Did these things happen millions of years ago or did they happen only thousands of years ago? So formation of the sun, pyramids were built, the earliest human civilization, the first unicellular organisms, the first cells with a nucleus, humans developed farming, the first dinosaurs, the first multicellular organisms, the dinosaurs went extinct, first land plants, the Earth was formed, and the appearance of modern humans, that's our species, Homo sapiens.

So put each of those bullet points, each of those events into the appropriate column.

Did those have things happen billions of years ago, millions of years ago? Or did they happen thousands of years ago? Pause the video to give yourself enough time to think through the question and to write down your answers.

Click play when you're ready to see the answers.

Good luck everyone.

Let's check your answers.

Okay, formation of the sun, did that happen billions, millions, or thousands of years ago? That was billions of years ago.

The pyramids were built, thousands of years ago.

That's something that happened in human history.

So had to occur in the last few thousand years or hundreds of thousands of years, the earliest human civilization.

Again, that's thousands of years ago.

The first unicellular organisms, that happened billions of years ago.

First cells with a nucleus, also billions of years ago, humans developed farming, thousands of years ago, the first dinosaurs, millions of years ago, first multicellular organisms, again, when multicellular, that means organisms like us that are made up of more than one cell.

That was millions of years ago.

Dinosaurs were extinct, millions of years ago, the first land plants also millions of years ago, the Earth was formed billions of years ago, 4.

5 billion years ago.

The appearance of modern humans, that was thousands of years ago.

Well done if you've got all of those in the right categories.

So we've talked about the numbers, thousand, million and billion, and hopefully now giving you some context for just how different those numbers are and just how big they are and some key events from the last few thousand through million through few billion years ago.

Now we're gonna look at a timeline of the history of the Earth and put some of those events into the correct order.

As I've already said, based on the evidence available, scientists believe that the Earth is 4.

5 billion years old.

We've talked about how huge that number is.

If you said a number every second you want to count to a billion, it would take you 32 years.

We're talking about a very long time ago.

You might be wondering, well, how do scientists know that? And if you are wondering that, you've got a curious and scientific mind, think about pursuing science at a further level than just GCSE.

So the reasons that scientists know this is 'cause they can work out the age of material such as rock or the fossils inside sedimentary rock through a method known as radiometric dating.

I'm gonna explain it really simply.

It's quite a complicated process.

So radiometric dating looks at the presence of radioactive elements to determine the age of material.

So radioactive elements have certain patterns to the way they behave, that help us to determine the age of materials like rock.

But let's see if we understood what I just explained.

Based on evidence of the age of rocks, how old do scientists think the Earth is? Is it 4.

5 billion years old, is it 4.

5 million years old or is it 4.

5 thousand years old? Take five seconds or pause the video and click play when you're ready to see the answer.

Okay, how did you do? 4.

5 billion years old.

Well done if you got that right.

So the Earth was formed 4.

5 billion years ago.

What about the first life on Earth? So the first living organisms were unicellular, one cell, single-celled organisms without nuclei.

And we've got a lot of evidence for this.

So these fossils called stromatolites are the oldest fossils that have ever been found, they were formed from layers of these early cells, and I've got a picture of them here.

The oldest stromatolites are 3.

5 billion years ago.

So using that and other evidence, scientists have estimated that the first cells appeared around 3.

8 billion years ago.

Let's move forward with our timeline.

So Earth was formed 4.

5 billion years ago, the first life on Earth around 3.

8 billion years ago.

Let's look at some other key events.

So eventually these unicellular organisms evolved, changed over time into more complex forms of life.

So the first fungi were 1.

5 billion years ago.

The first land plants were 500 million years ago, and the first mammals were around 200 million years ago.

Let's keep going further in time.

So I've already said modern humans have only been around for 350,000 years.

This is just a tiny fraction of the history of the Earth.

There's lots of fossil evidence to show how humans have changed over time also, or evolved.

And the youngest fossils that we found are about 10,000 years old.

Let's check to see if we understood that.

Starting with the oldest, put these events in the correct chronological order.

So a, first land plants, b, first mammals, c, first single-celled organism, and d, first fungi.

Take five seconds or pause the video and then click play when you're ready to see your answer.

Okay, let's check and see what you got.

So the first thing that happened was the first single-celled organism, then the first fungi, then the first land plants, and after that, the first mammals.

Well done, if you got that right.

This is the final practise task for today's lesson, well done for getting here.

So Earth is approximately 4.

5 billion years old.

Imagine if those 4.

5 billion years were compressed into just one single year.

In this imagining year of Earth, so the Earth will be formed on the 1st of January, first day of the year, and the first of the organisms would appear around the 25th of February.

The present day is at the very, very end of the 31st of December, the last day of the year.

Put the other events into your year of Earth timeline, the one that's on your worksheet.

So here are the other events I'm asking you to put on the timeline.

So the first land plants, the first cells with a nucleus, the youngest fossils that have ever been found, the first modern humans, Homo sapiens, the first fungi, the oldest fossils ever found were formed.

The first mammals evolved and the first dinosaurs evolved.

So you'll need to pause the video now to give yourself enough time to think about where do all these events go on the timeline.

Click play when you're ready to see the answers.

Good luck everyone.

How did you find that? Okay, let's look at your answers.

So your answers should look something like this.

So I've already got on there the things that were included.

So the Earth was formed, that's equivalent to be happening on the 1st of January, the first single-celled organisms. that's equivalent to happening on the 25th of February.

So first thing that you should have put on would be, the oldest fossil that have ever been found from stromatolites around 3.

5 billion years ago.

And that's equivalent to have happened on the 21st of March.

Well done if you got that in the right ballpark.

Okay, the next thing that happened, so we're looking at the first cells with a nucleus.

So that happened around the 14th of July.

So we're already in the second half of the year.

The first six months are up until June.

We're July to December now, we're in the latter half of the year.

So in half of time that has existed is when we've had cells that have nucleus.

So already something that's really, really different to us but the building box of what makes us up, it's only existed for half of all time of the Earth.

The next thing, the first fungi would appear around the 1st of December, 1st of September, sorry, and the first land plants would occur on the 20th of November.

We still haven't got mammals yet and we're entering the last month of the year, the last 12th of time, of all you know of the whole history of the Earth.

Isn't that crazy? So we're into December now.

I've had to make this a lot longer 'cause a lot is happening in December.

So now we have the first dinosaurs in the 13th of December.

So that's just squeezed into the first half of the last month of the year of our timeline.

The first mammals, we just made it in the first half of the month around the 14th December.

Again, well done if you've been getting these close to the right dates.

And now we're on the last day of the last month of the year.

These are think, think about all the things that have happened in our timeline of the year.

We're now zooming in, a whole lot is gonna happen in this last little tiny section of time that's existed.

So we've got the first modern humans happening at, if you put times on this, well done, extra credit for that.

So at 11:19 PM would be the equivalent of when the first modern humans appeared on the scene.

If we were compressed the last 4.

5 billion years into a single year, at 11:58 PM we have the youngest fossils that have ever been discovered.

And then as we said already, 11:59 PM is present day.

Isn't that crazy? If we look at our timeline, hopefully you can see just how short a fraction of time that human beings have been on the planet.

Dinosaurs are around for like, close to 200 million years.

Modern humans have only been around for the last 350,000 years.

And again, hopefully now you've got a context with just how different the numbers a thousand and a million are.

We've really, really not been around for very long.

But look at the impact we've already had on the planet.

Lots of it good, but lots of it bad.

Isn't that fascinating? Only been here for such a short period of time in terms of the history of the whole Earth.

Hopefully this has given you some more context now for some of the really important kind of key biological historical events that happened, including over the history of the Earth.

So let's sum up what we've learned to help us remember it.

So one million is one thousand thousand, or 1 with six zeros at the end of it.

One billion is one thousand million, or 1 with nine zeros at the end of it.

Rocks and fossils provide evidence for the age of the Earth and the first appearance of various forms of life on Earth.

Evidence from rocks suggests Earth was formed 4.

5 billion years ago.

Evidence from fossils suggests that the first living organisms, microorganisms, appeared around 3.

8 billion years ago.

The first land plants appeared approximately 500 million years ago, and the first mammals approximately 200 million years ago, modern humans appeared approximately 350,000 years ago.

Great work today, well done on getting your head around some of those really huge numbers.

It's not really intuitive, they're really abstract, so well done for pushing through.

Take a bit of a break now and I'll see you back really soon for our next lesson.