Hello, my name's Mr Jarvis and I'm gonna be taking you through today's lesson from the unit living organisms and their environments.

Today's lesson is all about estimating population size and distribution using transects and it's a practical-based lesson.

By the end of today's lesson, you should be able to investigate the effect of a factor on the distribution of a species using a transect.

There are five keywords to today's lesson.

They are quadrat, transect, abiotic factor, abundance, and distribution.

The definitions are up on the screen at the moment, but you can always pause the video so that you've got more time to read through the definitions if you want to.

I will, however, be going through those definitions as we cover the content in the lesson.

Today's lesson is broken down into two parts.

First we're gonna look at factors that affect a species' distribution and then we're gonna move onto the practical activity of investigating distribution using a transect.

So if you're ready, let's get started with the first part of the lesson which is all about factors that affect a species' distribution.

Quadrats are one method that scientists use to sample populations of organisms. And quadrats are square frames that are made of wood or metal.

Here's a picture of a quadrat.

They vary in size, but often each side is 0.

5 metres and that means that the area of the quadrat is 0.

5 multiplied by 0.

5 and that's 0.

25 metres squared.

Quadrats can be used to gather information about the abundance, that's the number of species in a habitat.

They can be used to estimate the number of different species that live in a habitat and that's a measure of biodiversity, the number of different species that are found in one place.

And they can be used to estimate the percentage cover of a species in a habitat and that's really helpful when plants or organisms are really small and difficult to count.

Using random sampling methods, quadrats can be used to estimate populations of plants and slow-moving or sedentary animals.

Daisy plants are commonly found in places such as parks and gardens and playing fields and limpets are molluscs that live on rocky shores.

They're an example of an animal that doesn't move very far, they only move when the tide's in and so when the tide's out, limpets are really good organisms to sample using a quadrat.

Quadrats can also be used to investigate the impact of changes of physical conditions that occur within a habitat, and these physical conditions are known as non-living or abiotic factors.

An abiotic factor is a factor that is not living.

Some examples of abiotic factors include light intensity, the soil type or soil pH, temperature, and soil moisture or rainfall.

There are others.

Abiotic factors in a habitat can be measured using various equipment such a light metre for light intensity, a pH metre to determine the acidity of a soil, a temperature probe to measure the temperature of a habitat, and a soil moisture probe can be used to work out how much moisture there is in soil.

Here's a check.

Which of the following are abiotic factors in a habitat? First of all, A, plants competing for space to grow, B, the volume of rainfall, C, the type of soil, or D, animals competing for a mate.

I'll pause for a few seconds and then we'll check your answer.

The correct answer is B and C.

The volume of rainfall is a physical or abiotic factor and so is the type of soil.

Plants competing for space to grow and animals competing for a mate are both examples of living factors or biotic factors.

Here's another check.

Which of the following is an abiotic factor that you might measure while sampling clover plants in a school field? A, the intensity of light, B, the number of herbivores feeding on the clover plants, or C, the number of clover plants that show signs of disease.

Again, I'll pause for a few seconds and then we'll check your answer.

The correct answer here is A, the intensity of light is an abiotic factor that might affect clover plants that are growing in a school field.

The other factors might also affect the clover plants in the field, but they're both examples of living factors.

The number of herbivores or the number of animals that are eating the clover plants is a biotic factor as is disease.

Abiotic and biotic factors can impact the distribution of a species and the distribution is the geographical area in which a species is found.

And scientists sample rare species using quadrats as part of conservation efforts in local habitats.

For example, sampling bee orchids which are really rare in the UK.

They monitor the abundance, how many of the species there are, and the distribution, the geographical area in which they're found, in the local habitat and they see whether their conservation work is successful.

Scientists working across the country looking at the same species can monitor the distribution or the geographical spread of a species and that information is often plotted as dots on maps.

Here's an example of a distribution map that looks at a species from 2013 and one that compares the distribution in 2023, and we can see the number and the distribution of dots has increased over time.

These maps can be used to show whether conservation efforts are helping the species to increase in both abundance and distribution.

Random sampling is not useful when we're investigating the effect of an abiotic factor on a species.

When investigating abiotic factors, a more systematic sampling is appropriate and that means having a system in place.

So, systematic sampling is not random but uses a system or rule to place quadrats.

So for example, every five metres, every five steps, every two metres, that's an example of systematic sampling.

Systematic sampling using a quadrat often takes place along a transect and a transect is a straight line between two points across a habitat.

And we use this transect to make observations and measurements.

A transect can be made using a tape measure and the quadrat is placed at one end of the transect.

The numbers of plants are counted and the abiotic factors, for example, light intensity, is measured.

Then, we systematically sample.

So, for example, we could measure two metres along the transect and take quadrat number two, or we could flip the quadrat over and over again and use that point as sample two.

Flipping again for sample three and again for sample four, and again for sample five.

The samples are taken continuously at regular intervals along the transect and this is called a belt transect because it looks a little bit like a belt that you put around your waist.

Here's a check.

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

A, estimate the population of a species in a habitat.

B, see how the distribution 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 a few seconds and then we'll check to see whether you got the answer right.

The correct answer here is B.

We use a transect and systematic sampling to sample species when we want to see how the distribution of species changes as a result of an abiotic factor.

Well done if you got that.

Here's our first task of the lesson.

Andeep carried out a belt transect on the school field.

He counted the number of daisy plants in each quadrat.

Daisy plants grow well in sunny spots.

He measured the light intensity using a light metre at each quadrat.

Write down a prediction of what Andeep's results might be and explain reasons for your prediction.

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

Good luck.

So you were asked to write down a prediction of what Andeep's results might be and to give some reasons for your prediction and I told you that daisy plants liked to grow in sunny spots.

So your answer might have included that the number of daisy plants will increase as samples get closer to B.

And the reason for this is that daisy plants grow well in sunny spots and the tree is shading samples one, two, and three so the light intensity, which is an abiotic factor, will be low and so daisies won't grow as well here.

Also, closer to B, the light intensity will increase so there should be more daisy plants growing there.

Well done if you got all or some of those points in your answer.

That brings us to the second part of the lesson today which is investigating the distribution by using a transect and for this you need to do a practical.

A transect can be used to study the distribution of organisms and you can see the impact as a result on the changes in the environmental conditions such as light intensity.

And we're going to investigate the distribution of a species of a plant using quadrats along a transect.

And you can see, as we pointed out in the first half of the lesson, we're using a tape measure in this picture as a transect line.

In terms of your investigation, what will you need? I'll pause for a few seconds to allow you to think.

Things that you might've come up with are, a quadrat, a tape measure that's at least 20 metres long, some pegs to hold down the tape measure so that you've got a nice straight line for your quadrat survey, a clipboard, paper, and pencil, and some apparatus for measuring an abiotic factor such as a light metre or an app on your phone.

You'll also need to decide which species of plant that you're going to survey.

And to help you, some of the common plants that you'll find in school fields or playing fields are included in the additional materials as a short identification guide.

Before you start, you need to decide what species you will study.

It's a good idea to choose a relatively common species so that you can see the impact of the abiotic factor.

You also need to decide which abiotic factor you'll measure.

Will you look at soil type, soil pH, moisture levels, or light intensity? How often will you measure along the transect? So remember, we're systematically sampling.

Will you measure every two metres, every five metres, every three steps? You need to choose.

What rules will you use for counting individuals in your quadrat so that you only count each individual once? Will you count all of the individuals that are within the quadrat and might touch the left-hand side or the top of the quadrat and not those that touch the right-hand side or the bottom of the quadrat? You need to make a rule and to follow it.

And finally, how will you record your results? You need to design a table.

You need to think about what you need to record.

It might be a good idea at this point to pause the video and think about the answers to those questions and the sorts of things that you might study in your own investigation.

We're going to investigate the distribution of daisy plants and see how this changes with the abiotic factor light intensity.

What will you need to include in your results table? What headings will you include in your results table? I'll pause for a few seconds to give you some time to think about what headings you might use.

So, you'll need to record the distance that you're travelling along the transect, the number of daisy plants that are present within the quadrat samples, and you'll need to take measurements of light intensity and include the units, and the light intensity unit is the lux.

Then we think about the method.

We're going to set out our transect.

Starting from the base of a tree, we're going to use a tape measure to make a transect and we're gonna use pegs to secure it in place.

I'm then gonna lay the quadrat with the top left-hand corner at the zero mark on the transect line a bit like this.

We're going to record the number of daisy plants within the quadrat and we're going to record the abiotic factor which in this case is the light intensity at the transect point.

We're then going to move the quadrat along the transect line a set distance, we're going to use systematic sampling.

So, for example, every two metres.

There, the quadrat's moved along the transect line by two metres.

When we've moved the quadrat, we need to record the abundance, the number of daisy plants in the quadrat, and we need to record the abiotic factor, the light intensity, at this transect point.

What we're then going to do is to continue to take measurements every two metres along the transect and it's a good idea to do this for a valid number of readings, so probably about 10 readings or 20 metres along the transect.

Here's a video to see the method in action in a field.

So from the video, here are the results, and these results are available in the additional materials.

We've got the distance along the transect, the abundance of daisy plants, and the light intensity at each transect point in lux.

We're going to move now to draw some graphs of our results.

First of all, we're going to focus on the number or the abundance of daisy plants along the transect.

What's the most appropriate graph to draw to show the number of daisy plants along the transect? I'll give you some time to think of what the most appropriate graph would be.

The most appropriate graph would be a bar chart because bar charts show data that's collected from groups.

In the additional materials, there's some graph paper to allow you to draw a bar chart of the results for yourself.

Here's my bar chart that shows the number of daisy plants along the transect.

Along the transect, describe the change in the number of daisy plants.

I'll pause for a few seconds and then we're gonna do a check based on that.

So, here is that check.

Which of the following answers best describes changes in the number of daisy plants along the transect? Is it, A, there was no change in the number of daisy plants along the transect? B, the number of daisy plants increased as you moved along the transect? C, there was no pattern to the number of daisy plants along the transect? Or D, the number of daisy plants decreased as you moved along the transect? Again, I'll pause for five seconds and then we'll check your answer.

The correct answer is B, the number of daisy plants is increasing as we moved along the transect.

Well done if you got that.

Now we're going to think about the other results that we got from our transect line.

We looked at how light intensity changed, the abiotic factor, as we moved along the transect.

What's the most appropriate graph to draw to show how light intensity changed along the transect? I'll pause again for a few seconds to get you to think about what your answer might be.

The most appropriate chart or graph to use here is a line graph, and that's because line graphs show a change in something over a continuous range, and again, in the additional materials, there's some graph paper to allow you to draw your own graph of the results.

Here's my line graph showing the results from the experiment we did.

You can see that it's not a straight line, I've drawn a line of best fit to show how the light intensity changes over the distance of the transect.

Along the transect, describe the change in the light intensity readings.

Again, I'll give you a few seconds to look at the graph and to think about the change and then we're gonna do a check based on that.

So here is that check.

Which of the following answers best describes changes in light intensity readings along the transect? Is it A, light intensity decreased as you moved from the shade of the tree at zero metres? Is it B, that the light intensity stayed the same? Is it C, that the light intensity increased as you moved away from the shade of the tree at zero metres? Or D, that the light intensity didn't show any pattern? I'll pause for a few seconds and then we'll check your answer.

The correct answer is C, light intensity has increased as we moved away from the shade of the tree at zero metres.

Well done if you picked up that pattern.

Now we're going to look at our conclusion.

What correlation is there between the change in the distribution of daisy plants and the change in light intensity? And I've got both of the graphs up on the screen and we can compare them because the scales match.

So, as we go from one side of each graph to the other they correlate in terms of the distance along the transect.

What correlations can you see? Again, I'll pause for a few seconds and then we're gonna move onto a check that's based on those two graphs.

So here is that check.

What correlation is there between the change in the distribution of daisy plants and the change in the light intensity? Is it A, a positive correlation? B, a negative correlation? Or C, no correlation? I'll pause for a few seconds and then we'll see whether you got the right answer.

The correct answer is A, there's a positive correlation.

As the light intensity increases, the number of daisy plants increases too.

Both of the numbers are going upwards and so it's a positive correlation.

The two sets of data are clearly linked.

Well done if you got that right.

Here's another check.

Why might the change in light intensity have cause the change in the distribution of daisy plants? Is it A, that daisy plants grow best in shady conditions? B, daisy plants need light to help them grow well? C, too much light isn't good for daisy plants to grow healthily? Or D, more light means that daisy plants can get more nutrients from the soil? I'll pause for a few seconds and then we'll check to see if you got the right answer.

The correct answer is B, daisy plants need light to help them to grow well.

Well done if you got that.

That brings us to our final practise task of the lesson.

Alex investigated the distribution of cowslip plants.

He carried out a belt transect which started at the edge of a large lake and he measured soil moisture using a probe.

So soil moisture is our abiotic factor.

And the probe gives readings of 10 when the soil is waterlogged and zero when the soil is really dry.

His results are shown in the table below.

I'd like you to write a paragraph to explain what the results tell you about cowslip plants and soil moisture levels.

You'll need to pause the video at this point, you need to then write down your answer and when you're ready, press play and we'll check to see whether you got all of the points.

Good luck.

So, how did you do? I asked you to write a paragraph to explain what the results tell you about cowslip plants and soil moisture levels.

You might have included in your answer that as the soil moisture levels decrease, the number of cowslip plants decreases too.

There's a correlation between the results.

This tells us that cowslip plants can grow well in wet or waterlogged soils.

And that's because it may have adaptations that help it to survive in those conditions and as the soil dries out, other plants may be better adapted to outcompete the cowslip plants and so there's less cowslip plants that are able to survive and grow.

Well done if you got those answers.

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

We've seen that quadrats can be used to sample plants and slow-moving animals in habitats.

We've looked at how abiotic factors can impact the abundance, how common the species is, and the distribution, the geographical spread, of a species.

And we've seen how a transect, a straight line, can be used to investigate how the abundance and distribution of a species may be linked to an abiotic factor, for example, light intensity.

I hope you've enjoyed today's lesson, it's been great as always learning with you and I look forward to seeing you all again soon.

Bye bye for now.