Lesson video

Hi, everyone!

I'm Mrs. Horan and I'm so pleased you've come to join me because we've got some really interesting stuff to learn about today.

Today's lesson is part of the unit on "Human development.

" The lesson is called "Finding out about human height.

" And guess what we'll be doing.

We will be finding out about human height, including getting some measuring done ourselves.

The outcome for our lesson today is to take accurate measurements and compare human height.

The lesson builds on what you already know about human development, particularly how our height changes at different development stages, and is part of our big learning question, "How do living things grow and reproduce?

" These are the keywords that we're going to be focusing on today.

We have puberty, growth rate, average, measure, and result.

You're probably quite familiar with some of these and less familiar with others.

We're going to look at each one in detail when we come to it in the lesson so we'll have a really good understanding of them all by the time we finish.

Here are some explanations of the keywords.

We're not going to look at these in detail now though because each one will be explained when we come to it during the lesson.

It's useful to have them here anyway because that way, you can look back at them later if you need to double-check anything.

Our lesson today comes in three parts.

Let's get started with the first part, Human growth rate.

Some children are talking about how humans grow until they reach adulthood.

Aisha says, "I think we grow taller on our birthdays.

" Andeep says, "I think we're always growing.

" Izzy says, "I think I grow a bit every time I eat a healthy meal.

" What do you think?

You might want to pause the video here to have a think about this or discuss it with someone.

Andeep's idea is the most scientifically accurate.

Until we reach adulthood, we are always growing.

The humans grow continuously from birth until the end of puberty.

You've probably spotted one of our keywords at the end of that sentence.

Puberty.

Do you remember what that means?

Puberty is the period of time during adolescence when our bodies go through lots of changes to become adults that are capable of reproducing.

It usually happens around the age of 10 to 14 years old for girls, and 12 to 16 years old for boys, but every human is different and there are lots of people who go through puberty before or after this.

Once we reach the end of puberty, we are at our full adult height and do not grow any taller.

Let's do a quick check for understanding before we move on.

Which of these statements is true?

A, humans grow in short bursts from being a toddler to the end of childhood.

B, humans grow on their birthdays from birth to the end of puberty.

C, humans grow continuously from birth to the beginning of old age.

Or D, humans grow continuously from birth to the end of puberty.

Which one do you think is true?

It was D.

Humans grow continuously from birth until the end of puberty.

Well done!

Let's keep going.

The speed at which something grows is called its growth rate.

You can see growth rate is part of our keywords today and it just means the rate or speed at which something grows or gets bigger.

Do you think human growth rate is the same at every stage of development?

And you can see some of the human stages of development there from baby up to adult.

When you're trying to decide what you think about this question, think about what you know about each stage and how we change as we move through them.

Human growth rate is the fastest during the time humans are infants, which is nought to three years old, when we are babies and toddlers and during puberty.

Let's find out a little bit more about each of those development stages.

Did you know babies grow around 25 centimeters taller during their first year?

I think that's amazing.

Don't you?

To help you picture how big that is, think about a ruler, like this one.

A ruler is around 30 centimeters long, so babies grow nearly this much in a single year after they were born.

Let's have a look and see how much.

Zero to 25 centimeters.

Babies grow this much in their first year.

That's amazing!

You can also see this big difference in the clothes in the photo there.

One of those jumpers is for a one month old and the other is for a one year old.

You probably know that clothes sizes for children your age tend to come in groups of years.

So for example, eight to nine years old or 10 to 11 years, and that's because you're still growing, but you aren't growing incredibly quickly.

For babies, clothes tend to come in chunks of three-month periods instead.

So, nought to three months or three to six months, and that's because they grow so quickly that it would be impossible to have something that would fit a one month old and a one year old.

The human growth rate is the most rapid during this stage.

It is the fastest.

You will never again grow 25 whole centimeters in a single year.

During puberty, which takes place during the adolescent stage, humans grow around eight centimeters per year.

That's about this much.

This is the second-fastest period of human development after our first few years.

Time for another quick check for understanding.

At which stages of development is human growth rate the fastest?

We have A, baby and toddlerhood.

B, childhood.

C, adolescence.

And D, adulthood and old age.

You can pause the video here if you need a little bit of thinking time for this one.

Did you say A and C?

Baby and toddlerhood and adolescence are the stages of development with the fastest growth rate.

Let's put our learning to work now with a practice task.

Jacob has been writing about human growth rate.

Can you spot his mistakes?

Here is what he has written.

Humans grow continuously until the end of adulthood.

Humans grow very slowly during the time that they are babies.

They grow around 25 centimeters taller during their first month.

Adulthood is also a period of rapid growth for humans.

They grow around eight centimeters a month during puberty.

Pause the video to have a go at finding his mistakes and come back when you think you have spotted them all.

Welcome back.

Let's see how you did.

So, humans grow continuously until the end of puberty, that should be, not adulthood.

Humans grow very rapidly, or you could have quickly, or fast maybe, during the time they are babies.

They grow around 25 centimeters taller during their first year, not their first month.

And the final one.

Adolescence is also a period of rapid growth for humans.

They grow around eight centimeters a year, not a month, during puberty.

Thank you for your careful work on that task.

Let's move on to the second part of our lesson.

Differences in growth rate and height.

Some children have been talking about height differences in men and women.

Aisha says, "My dad is taller than my stepmum.

I think men are always taller than women.

" Izzy says, "I am taller than my friend Lucas.

I think that women are sometimes taller than men.

" Andeep says, "I think men grow more quickly, so they are usually taller.

" What do you think?

Do you agree with any of these children?

Or do you have a different idea?

Now, have you noticed any differences in height between the boys and girls in your class?

Girls and boys do actually have different growth rates over time.

Girls usually experience rapid growth a little earlier than boys.

Between the ages of 12 to 14 years old, girls are generally taller than boys of the same age.

Of course, we know all humans are different, so not all girls will be taller than all boys, but as scientists, we can look at patterns like this and identify trends that are true for many people.

Generally, by the time humans reach adulthood, men are taller than women.

The average height for a man in the UK is 178.

2 centimeters, and for women, it is 164.

3 centimeters.

We have another keyword there, average.

And we find the average of a set of numbers by adding together all the numbers and then dividing by the amount of numbers we had.

Averages can be useful to help us understand large amounts of data.

And to find the average height for men, we add together all the men's heights, then divide by the number of heights we had.

Of course, lots of people will be taller or shorter than this number, but the average gives us a general idea about the whole population.

And of course, we know all humans are different, so this is not the same for every single man and every single woman.

Time for another quick check-in on your understanding.

Look at this statement and decide whether you think it's true or false.

Usually, boys are taller than girls at all stages of development.

Do you think that's true or false?

Great!

That statement is false.

Now, can you justify how you know it's false?

Is it false because, A, boys are never taller than girls?

Or is it false because, B, girls are generally taller than boys from the ages of 12 to 14 years old?

What do you think?

So, it is false because girls are generally taller than boys from the ages of around 12 to 14 years old.

The rest of the time, boys are generally taller than girls.

Izzy has a question about human height.

She asks, "Have humans always been around the same height, or was it different in the past?

" That is a really interesting question.

What do you think about this?

How could we find out?

Archeologists are scientists who learn about the past by exploring artifacts and remains that have been dug up from the ground.

Doesn't that sound like an interesting job?

It's a great crossover between history and science.

You can see an archeologist uncovering some bones there in the photograph.

It has to be done very carefully because old bones can be very fragile.

By carefully studying the human skeletons that they have found from different time periods, they can work out the average heights of people in the past.

Isn't that amazing?

Izzy has been doing some research using secondary sources to find out more about this.

This is what she has found.

So she has found that the average male height in centimeters was around 177 in the year 2000.

It was around 176 centimeters in 1950, 169 centimeters in 1900, and 165 centimeters in 1850.

What do you notice about her results?

You might want to pause the video here to have a really good look at the data and give yourself a moment to think about what it showed.

Humans are generally taller now than they were in the past.

We can see evidence of this in old homes which have lower doorways and ceilings than the ones we have now.

Have you ever been to an old house that has lower doorways than the ones we're used to?

There are still quite a few around.

If you're ever lucky enough to visit Shakespeare's home in Stratford-upon-Avon or Isaac Newton's house in Grantham, then you'll notice that the doorways on those are much lower than we are used to because people who lived at that time were shorter.

Here's another really interesting question.

Why do you think humans in the past might have been shorter?

As scientific understanding and technology improves over time, human health also becomes better.

Let's think about Shakespeare since we've mentioned him already.

He was an adult in the 17th century, around 400 years ago.

What do you think we have access to now that makes our health better that we wouldn't have had access to then?

We now have access to more nutritious food and better care if we become unwell.

Because of this, humans generally now grow taller.

We have so much choice for fresh, healthy food in supermarkets, and it's free for us to see a doctor if we need to.

We also have a lot more knowledge about how to live a healthy life than we had in the past.

Izzy says, "I wonder if humans will be taller than us 100 years into the future?

" I wonder that too.

What do you think?

Now, we have another quick question to check your understanding.

Which of these factors contribute to humans generally being taller now than they were in the past?

The factors we have are, A, better diets, B, more access to healthcare, C, warmer climate, and D, larger homes.

What do you think?

Did you say A and B?

These other things that contribute to humans being generally taller now than they are in the past, better diets and more access to healthcare.

Let's try something a little more challenging now then.

Explain how each of these people's heights are likely to be different to each other and why.

So we have a 13-year-old girl and a 13-year-old boy.

How might their heights be different to each other?

We have an adult man and an adult woman alive now.

And we have a man alive in 2020 and a man alive in 1820.

Pause the video here to write your explanations.

They only need to be about a sentence long each.

Then, come back when you are done.

Let's see how you did.

Of course, you don't need to have exactly the same words as me to be correct, just the same ideas or information.

So number one.

If we have a 13-year-old girl and a 13-year-old boy, then the girl is likely to be taller than the boy because girls from the ages of around 12 to 14 years old are generally taller than boys.

If we had an adult man and adult woman alive now, then the man is likely to be taller than the woman because men are generally taller than women as adults.

And if we had a man alive in 2020 and a man alive in 1820, then the 2020 man is likely to be taller because humans are generally taller now than they were in the past due to better health.

Time for the third part of our lesson now, Measuring height.

Andeep would like to investigate the heights of humans who live locally to him.

Locally means nearby, so people in his city or town.

He plans to measure children of different ages.

Measure is another one of our keywords today, and you might remember that it means to use equipment to find numbers to describe a feature of something, such as its length, weight, size, or time.

Length or height can be measured in different ways.

For example, millimeters, centimeters, and meters.

What is the difference between these units of measure?

Which do you think will be best for measuring human height?

You might want to pause the video here for a moment's thinking time about this.

Millimeters would not be suitable for measuring human height because millimeters are too small.

Andeep says, "I could use centimeters for shorter humans and meters for anyone who is taller than a meter.

" Do you agree?

Now Andeep must choose the same unit for all of his measurements so he can make comparisons and analyze his results.

He says, "I am going to use centimeters because they will be more precise.

" There is a lot of equipment in the science cupboard for Andeep to choose from.

So we have a tape measure, a trundle wheel, weighing scales, ruler, meter stick, and a Newton meter is all equipment for making measurements.

What do you think he should use?

Explain why.

So pause the video here to describe what equipment you think will be best and explain your reasoning to a partner.

Andeep needs to choose equipment that will measure length longer than a meter.

Andeep says, "I could choose a meter stick because it is long and straight, so it will be easy to measure height.

" Or, "I could choose a tape measure because it is flexible, so I can be more precise.

" What do you think?

What will be best for measuring height?

If possible, it would be really good for you to get your hands on a tape measure and a meter stick here to examine them and help you make a decision about what will be best.

Pause the video here and come back when you have made your decision about the best piece of equipment for this job.

The meter stick will be best.

Is that what you decided too?

To measure height accurately, Andeep should ask his humans to stand up against a wall, then use the meter stick to measure the height of the point on the wall they reach.

So, if you take a look at the picture there, we can see Andeep's subject is standing against the wall.

Then he needs to use the meter stick to see how high up on the wall the top of the boy's head is.

For taller humans, Andeep may need to move his meter stick while measuring.

So if someone is more than a meter tall, he will need to place his finger at the height of one meter on the wall, move the meter stick up to that point, and then take his measurement.

Let's see how you're doing them.

Which of these pieces of equipment will be best for measuring human height?

Do you think it's A, a tape measure?

B, weighing scales?

C, a meter stick?

Or D, a ruler?

Great!

It's C, the meter stick.

The tape measure is too bendy, so it will be difficult to measure height.

The weighing scales will be good for measuring mass but not height.

And the ruler is too small.

Now Andeep is thinking about how he can make his results more reliable.

And results is another one of our keywords today.

It means the findings from an investigation or inquiry.

He says, "I think I can just measure one person of each age.

" Do you agree?

Scientists get more reliable and detailed results by taking multiple measurements.

Andeep's results will be improved if he takes measurements of more humans from each different age group.

So you'll probably know already that some people are taller than others and some are shorter.

If he only measures one person and that person happens to be really tall, then it might make it seem like everyone of that age should be that tall.

Taking lots of measurements means his results will be more reliable, because then he will probably have a mixture of people who are tall, short, and somewhere in the middle, and he'll be able to get a much better idea of people's heights in general.

Let's do another quick check for understanding before our last task of the lesson.

Why do scientists take multiple measurements when carrying out an inquiry?

Is it because, A, it makes them less likely to measure incorrectly?

B, to give everyone a turn at measuring?

C, it gives them more reliable data?

Or D, they need lots of practice to get measurements right?

What do you think?

So the answer for this one was C.

Scientists take multiple measurements when carrying out an inquiry because it gives them more reliable data.

Time for another task.

Measure at least six different humans of a range of different ages and record your findings in the table.

We have a table here with some data already filled in for you.

Your job is to take as many of the measurements as you can to fill in other boxes on the table.

Now you might not have enough time or even enough humans to complete the full table.

So for any that you can't do yourself, you can use Andeep's data on the next slide to fill in those boxes.

Pause the video now to go and carefully, accurately measure your humans and come back when you have done as many as you can.

Welcome back.

How did you find measuring people?

Was it difficult to be accurate, or did you find it quite easy?

It's definitely harder for people who are taller than one meter because you have to move your meter stick.

So, here are Andeep's results.

Remember, you can use these to fill in any gaps on your own table.

He measured different children to you, so his measurements probably won't be exactly the same as yours.

You might want to pause the video here to take a really good look at them and compare them to yours.

Are they about the same?

Are there any big differences?

Are there any results that really surprised you?

And that brings us to the end of our lesson.

What a lot we have achieved today!

Let's take a look back at the key learning from this lesson.

Humans continuously grow taller from birth through to the end of puberty.

Growth rate is at its fastest during the baby, toddler, and adolescent stages.

Girls are often taller than boys at 12 to 14 years old, but men are generally taller than women as adults.

Humans are taller now than in the past because they have healthier lifestyles.

And we can find out about changes in height by measuring humans of different ages.

Thank you so much for taking part in our lesson today, carefully measuring all those children and adding your results to the table.

I hope you feel like you were able to improve your measuring skills with all the practice you got today.

I'll see you again next time.