Hello, how are you doing? I'm Mr. Jarvis, and I'm gonna be teaching you this lesson today.

The lesson comes from the unit biodiversity, and today we are learning all about ecological sampling using a quadrat.

By the end of today's lesson, you should be able to know how to use a quadrat to sample populations of organisms. There are three key words to today's lesson.

They are quadrat, species, and bias.

The definitions are coming up on the screen now.

I'll give you a little bit of time to read through them.

You can pause the video if you need more time.

Today's lesson is broken down into three parts.

First of all, we're going to be learning all about how to use a quadrat.

Then we are going to look at sampling methods using a quadrat.

And finally, we are going to be looking at how sampling helps to support the conservation of species.

So if you're ready, let's get started with our first part, which is all about using quadrats.

So, a sampling is a survey about organisms that helps to give information about the populations within a habitat.

So we've got a picture on the right hand side of the screen, which shows a population of bees.

Now you can see that would be really difficult to count and sampling is a useful way to help us estimate the size of a population.

It's so much easier, cheaper, and faster to do than it would be if we tried to count all of the individuals.

Quadrats are one method that scientists use to survey or sample populations of organisms. They're square frames that are either made of wood or metal and they can be placed on the ground.

They vary in size, but each side is usually half a metre, and that means that the area of a quadrat is half a metre multiplied by half a metre, and that's an area of 0.

25 metres squared.

Quadrats are only useful for sampling plants and animals that are slow moving or sedentary.

And some of the examples of animals that can be sampled include things like sea anemones, mussels, barnacles, and starfish.

You can see all of those animals are found on rocky shores.

Other animals that could be sampled include things like snails and slugs.

So, here's a check.

Which of the following organisms might you use a quadrat to sample? We've got A, snails, B, dandelions, C, sparrows and D, cows.

I'll pause for five seconds and then we'll reveal the answer.

So, the correct answer is snails and dandelions.

The snails are slow moving animals and so they're something that you can use a quadrat for.

And dandelions are plants.

Well done if you got that right.

So quadrats can be used to sample populations in some habitats.

They can be used to help us estimate the different species that live within a habitat.

That's called a measure of biodiversity.

Remember, biodiversity is the number of different species that live in a particular area, and they can also be used to estimate the percentage coverage of a species within a habitat, and that's helpful when plants are small and difficult to count.

Quadrats are usually divided into smaller squares, and that depends on the type of quadrat that you're using.

You might have one that's divided into three by three big squares, or five by five small squares.

They can even be divided into a hundred squares, so 10 by 10, and that makes it really easy for percentages.

The idea of the squares is that it helps us to count the organisms that are present.

So when using a quadrat, there are two important things to remember.

First of all, sample size.

The sample size is really important.

The more the samples that you take, the more valid your results will be.

And secondly, samples must be chosen at random.

This avoids something that we call bias.

And bias was when a person carries out an investigation which affects an outcome.

So an example of bias is spotting a clump of brightly coloured flowers in a field that you're sampling and deciding to put the quadrat down over those flowers to count them.

That's bias.

There are several ways that we can ensure that samples are taken out at random.

Some examples include spinning round with your eyes closed and then walking ten paces forward and placing the quadrat on the ground.

Another is to use a random number generator to decide the number of steps that you'll take before placing the the quadrat on the ground and those random number generators could be using a computer or an app, or it could be simply drawing out some number counters from a bag.

The main thing to remember is that you should never throw a quadrat, especially when you're spinning around with your eyes closed.

It's really dangerous and it could actually hurt someone if you throw a quadrat and it hits them.

Here's an example of using a random number generator to sample plants using a quadrat.

We're gonna watch a short video.

So you've watched the video.

Now let's do a check.

In the context of a science experiment, what does the word bias mean? Is it A, not being organised and recording data accurately? Is it B, collecting random samples for an experiment? Or C, when a person carries out an investigation and affects the outcome? I'll give you a five second pause and then we'll check your answer.

The correct answer is C.

When a person carries out an investigation and affects the outcome, we call that bias.

Well done if you got that right.

Let's move on to our first task of today's lesson.

You've been told that you're going to carry out an experiment on the school field to see how common daisies are.

Here's a picture of some daisies in the school field.

I'd like you to list the equipment that you'll need to carry out the experiment and write a short method of what you might do.

You'll need to pause the video at this point, write down your answers, and then when you're ready, press play, and we'll see how well you've done.

Good luck.

So I asked you to list the equipment that you would need to carry out an experiment to sample daisies in your school field and to write a short method.

Things that you might have considered.

First of all, for your equipment, you'd have needed a quadrat.

You'd have also needed a notebook and pen.

You might also have decided that you needed a tape measure and an identification guide so that you knew what the daisies looked like.

You could have even considered a random number generator, so it could have been that you included some counters with numbers on to select where you were going to sample.

In terms of the method, first of all, you needed to make sure that you select where the samples will be made randomly so that you avoided bias.

You'd use the numbers to pace out or measure the location of the first quadrat.

You'd lay the quadrat on the ground and you'd count and record the number of daisies inside the quadrat.

You'd repeat it until such time as you had enough results to make your results valid.

Well done if you got all of those things right.

That brings us to the second part of the lesson today and this part of the lesson is all about sampling methods using a quadrat.

So if you're ready, let's move on.

We need some rules for counting when we use a quadrat and we need that rule for counting so that we don't count an individual twice.

There are lots of different methods that you could use and there's no fixed way of doing this, but you need a rule so that you make sure that you don't count those organisms more than once.

One example method that we use is to count an organism if it's fully within a quadrat or if it's touching the top or the left edges.

You can see the green line showing those edges that we would count the organism in.

If the organism touches the bottom or right edges and is not fully within the quadrat, then we don't count it.

So let's test whether we would count organisms by having some examples.

So, which flowers will you count? How about number one? Would you count this one? Yes, you would.

And you'd count it because it's fully within the quadrat.

What about this one? Again, yes, because it's not fully within the quadrat, but it's touching the top edge of the quadrat.

And our rule says that if an organism is within the quadrat or it touches or crosses the top edge, then we count it.

What about the third example? This organism we wouldn't count, and we wouldn't count it because it's not fully within the quadrat and it's touching the bottom edge.

And our rule says if an organism is not fully within the the quadrat and it touches the bottom of the right edges, we don't count it.

Well done if you've got those three right.

So, to help us identify species when we use quadrats, we can use a classification key.

And the key uses a series of questions based on an organism's physical features.

Here's an example on the screen.

We've got a picture of a yellow flower.

Our first question is, are the flowers yellow? The answer to that is yes, and that takes us down a pathway.

Our next question says, do the leaves have jagged edges? Now, the picture isn't that clear in terms of the focus of the leaves, but we can see that the leaves are smooth, they're not jagged in terms of our edges, and so the answer to that is no, and that identifies the organism as a buttercup.

We can use our answers to correctly identify the picture or the species that we have in front of us.

Here's a check.

Which features of an organism do classification keys use to identify them? Is it A, how common the organism is? B, their physical features? Or C, their genetic features? I'll pause for five seconds and then we'll check your answer.

So the correct answer is B, we use their physical features.

So, classification keys use physical features to help identify an organism.

Well done if you got that right.

So when we use a quadrat to sample, there are two main methods that we use.

First of all, we use random sampling and this is used to sample the number of a species in different habitats or locations.

The second method is sampling along a line, and we call that line a transect.

This method is used to see how numbers of species change.

It's usually linked to an abiotic factor such as distance up a seashore, or where there's a path where there's lots of trampling.

So, physical damage to the the environment.

Let's look at random sampling.

The quadrat here is placed randomly on the ground and the number of organisms within each quadrat is then counted.

We can then use that data to calculate the mean number of organisms per quadrat or per metre squared.

So let's look at some example data.

We're going to be counting the number of green flowers in each 0.

25 metre squared quadrat that we place on our school field example on the right hand side of the screen.

So let's place our quadrats and count the number of green flowers that we have within them.

Here's our first, and there are no green flowers within this quadrat.

There is one flower within this one.

There's one here.

In this quadrat there are two because we've got one of the green flowers within the quadrat in the top right hand corner and one of the flowers crossing our left hand side edge of the quadrat.

Remember, we count the top edge and the left hand side edge of the quadrat.

There's one here.

There are two here, again, we've got one at the top edge and one crossing the bottom edge and one fully inside.

So we count the flower that's crossing the top edge.

We don't count the flower crossing the bottom edge.

There's no green flowers in this quadrat and there's one here.

So we've taken eight quadrat samples.

We can then calculate the mean by summing the number of green flowers within the samples and dividing by the number of samples.

So the number of green flowers that we've sampled within our eight quadrats are 8 in total, so 0+1+1+2+1+2+0+1.

And the number of samples taken is also 8.

And so 8 divided by 8 is 1.

There is an average, or a mean, of 1 flower per 0.

25 metre quadrat.

We can now take that data and work out how many flowers there are in each metre squared.

There are four 0.

25 metre squared quadrats in one square metre.

So we need to multiply up our answer by four to give us a number of flowers per metre squared.

And so there are 4 flowers per metre squared.

Now let's look at sampling along a line and a straight line between two points is called a transect.

We have a straight line between points A and B along the transect, and a quadrat is put on the transect right at the start.

And the plants in that quadrat are recorded in the same way as we did in the previous example.

Then what we do is we take samples at regular intervals along the transect.

That can be every metre along the line, or it can be at a set number of paces.

I'm gonna just flip the quadrat over.

So I'm going to flip the quadrat over twice and sample.

So I'm going to flip.

And there's my sample two.

I'm going to flip again.

Here's sample three.

Flip again, and there's sample four.

And flip again, sample five.

And flip again, and I've reached the end of my transect.

The method's useful for looking at how population changes along that line.

So for example, if you have a path running through the middle of the school field or if the school field's on a slope, that's also another really useful way of using sampling along a line or a transect.

Here's a video showing us how to use a quadrat to sample along a transect.

Let's do a check.

It's more useful to use a transect to survey species than random sampling when you want to.

Which of the following completes that sentence? A, estimate the population of species in a habitat? B, see how the population of species changes as a result of an abiotic factor? Or C, to survey a population of animals that move around quickly? I'll pause for five seconds and then we'll check your answer.

So, the correct answer is B.

It's more useful to use a transect to survey species than random sampling when you want to see how the population of a species changes as a result of an abiotic factor.

Well done if you got that right.

Let's move on to task B.

Jacob has sampled the school field.

He's used the classification key to be able to identify clover plants, and there's a picture of the clover plant on the right hand side of the screen.

He's used random sampling to gather the data to avoid bias, and he's used a 0.

25 metre squared quadrat for all his samples.

Use the data in the table to work out the mean number of clover plants per metre squared in the school field and show you're working in the answer.

And as a hint, there are four 0.

25 square metre quadrats in one square metre.

Here's the data that Jacob recorded.

He's recorded the number of clover plants in each 0.

25 square metre quadrat.

You need now to pause the video, work out the mean number of clover plants per square metre in the school field, and then when you're ready, press play, and we'll check to see how well you've done.

How did you find that? I hope that you got on okay.

You were asked to use the data in Jacob's table of results to work out the mean number of clover plants per metre squared in the school field.

You needed to show your working in your answer.

So, let's see what you should have done.

First of all, you needed to work out the mean number of clover plants per quadrat per 0.

25 square metres.

So, we needed to use the equation.

The mean is equal to the sum of the samples divided by the number of samples.

So the sum of the samples is 3+3+5+6+3+7+4+2+3+4, and the number of samples is 10.

So if we work that equation out, it's 40 divided by 10.

40 divided by 10 is 4.

So there are 4 clover plants per 0.

25 metre squared, or 4 clover plants per quadrat.

So if there are 4 plants per 0.

25 metre square quadrat, and there are four of those quadrats in a metre square, it's 4 multiplied by 4.

And that gives us the answer, 16 clover plants per metre squared.

Well done if you've got all that correct.

That brings us to the final part of today's lesson, and in this part the lesson, we're going to be looking at supporting the conservation of species using our ecological sampling.

So if you're ready, let's move on.

Quadrats help to monitor populations as part of conservation activities.

And by carrying out surveys, scientists can see whether their efforts to help species numbers to increase are being successful.

Here's one example.

Bee orchids are really rare in the United Kingdom and populations of these endangered orchids are often monitored by scientists as part of conservation activities, and they would be monitored using a quadrat.

Monitoring helps scientists to see whether populations are increasing in number and whether the populations are spreading to other areas.

And often scientists will use information to plot what we call distribution maps of species.

So, here's an example of a distribution map.

It shows how conservations efforts are working for a particular species.

And what happens is that we divide the country into lots of small grids, and when it's present we put a dot down to show that the species is found in that area.

And you can see in 2013, this particular species that we're looking at has been found in a number of different parts of the United Kingdom.

2023, through surveying, we can see that the population has spread, and so the maps can be used to show that conservation efforts are helping to increase the spread of the population, the distribution of the population.

Sampling information can also be used to track the spread of unwanted or introduced species that we are calling invasive species.

And here's an example.

Japanese knotweed that's in the picture was introduced into the UK as a garden plant, but it's an invasive species.

It grows rapidly and causes problems. It's a pest species, and that's because it out competes the native species and it can cause the native species to become endangered as their habitats changed.

Sampling techniques play an important role in conservation, whether we use pitfall traps, pooters, nets, or quadrats, the information that we get helps scientists to estimate the size of populations of species within a habitat.

It helps them to measure biodiversity, the number of species that are found within a habitat, and it can help to estimate the percentage coverage of a species when we use a quadrat.

Wildlife surveys don't, however, always have to be scientific.

There are lots of conservation organisations that ask the public to send in sightings of organisms or observations as part of citizen science projects.

There's some examples coming up on the screen.

Garden Birdwatch, Big Butterfly Count, or Nature's Calendar, which looks at the change of species over a calendar year.

The information helps organisations and scientists to monitor the populations of different species in different areas of the country and that informs conservation activities.

So here's a check.

Why are citizen science projects a useful way of sampling organisms to help with conservation? Is it A, that they help scientists to monitor populations of species? Is it B, they tell scientists exactly how many organisms of each species there are in an area? Or is it C, that they tell scientists whether a species is extinct? I'll give you five seconds and then we'll check your answer.

The correct answer is A, citizen science projects are a useful way to help scientists to monitor populations of species.

Well done if you got that right.

Let's move to our final check of the lesson today.

Sampling is an important part of conservation and one example is the conservation of the habitat of a rare UK orchid.

Scientists have sampled populations using quadrats to find out where the orchid is found, and the results have been plotted on distribution maps.

Here is the map of the orchid distribution in 2000, and here is the map of the distribution of the same orchid in 2020.

I'd like you to write a paragraph to explain what scientists need to consider when sampling, and what the distribution maps tell you.

You'll need to pause the video, write down your answer to the question, and then when you're ready, press play, and we'll check your answer.

Good luck.

So, how did you get on? Let's check your answer.

I asked you to write a paragraph to explain what scientists need to think about when they sample, and what the distribution maps of this rare orchid tell you.

So first of all, when you are sampling, you need to make sure that you're sampling randomly to avoid bias.

And importantly, we are not throwing the quadrats.

Secondly, you need to consider how many samples you need to improve the validity of your data.

And in terms of the distribution maps, they tell you that the orchids are dispersing, or increasing in their their commonness around the country, and that means that the conservation efforts are working and the orchids are reproducing.

The orchids are also being moved into new areas of the country.

For example, the Scottish borders and the Isle of Wight.

If you compare the two maps, you can see that the species has spread, the distribution is now much wider.

Well done if you got that correct.

That brings us to the summary of today's lesson.

Today we've seen that quadrats can be used to sample plants and slow moving animals, and that the information that we gather can be used to help us estimate the population of species and to measure biodiversity.

Classification keys can be used to help us identify species that we find within quadrats.

When we use quadrats, it's important that a sample should be taken randomly to avoid experimental bias.

And when we sample organisms, it helps to provide important information about species and that information can be used to support conservation efforts.

It's been great having you learn with me again today, and I look forward to seeing you all again in the future.

Bye-bye for now.