Hello, I'm Mr. Jarvis.

Good to see you again, I hope you're doing okay.

Today's lesson is all about ecological sampling of living organisms, and it forms part of our unit on biodiversity.

By the end of today's lesson, you're going to be able to describe and choose suitable methods to sample populations of plants and animals.

There are five key words to today's lesson.

They are sampling, quadrat, pooter, pitfall trap, and mark-release-recapture.

Here are the definitions of those words coming up on the screen now.

You can have a read through them, but don't worry because we will go through all of the definitions as we go through the lesson.

I'll pause for a few seconds to allow you some time to read through them.

So today's lesson is divided into three parts.

First of all, we're going to talk about why it's important to estimate population size.

Then we are going to move on to talk about different ways to sample organisms in their habitats.

And finally, we are going to look at why it's important to sample organisms. So if you are ready, let's get started with our first part of the lesson, estimating populations.

So a population is a number of organisms of one species that live in a particular habitat.

And here in the picture, you can see a population of fruit bats in a tree.

You can see that actually counting that population would take a long time to do, and it would also be really tricky.

If we just look at the picture, how easy is it to count the population from a still image? But all those bats are moving around all the time.

So we use sampling as a method to survey the organisms to help us get some information about populations within a habitat.

And here is a picture of a scientist sampling a population of reeds.

Sampling is a really useful way to help us estimate the size of a population.

And it's also much easier, much cheaper, and much faster to do than trying to count all of the individuals within a population.

Sampling is also useful because populations are constantly changing.

And they're constantly changing because of three things.

That's births, deaths, and migration, moving into and out of a habitat area.

So let's check to see how well you've understood that first section.

True or false? Sampling is when you count every organism in a population.

And then, can you justify your answer? Is it because A, sampling is a survey of organisms that helps to give us information about the populations in a habitat? Or is it B, we must count all of the organisms to help us estimate the size of a population? I'll pause for a few seconds to give you some time to think, and then we'll check your answer.

So the correct answer is that it's false.

Sampling is not when we count every organism within the population.

And the reason for that is A, that sampling is a survey of organisms that helps to give us information about the populations within a habitat.

Well done if you got that right.

So scientists who study living things in their habitats are called ecologists, and they use different methods to sample organisms in different types of habitat.

And it's important that organisms and their habitats are disturbed as little as possible when we sample them.

So let's do another check.

What's the best way to work out the size of a population of organisms? Is it A, to count all of the individuals in a population, B, make a guess, or C, sample a habitat and use the data to estimate? I'll give you five seconds to think about your answer, and then we'll check to see how well you've done.

So the correct answer is C, we sample a habitat and use the data to estimate our population.

Well done if you got that one right.

We're going to move on to a practise task.

Laura is struggling to understand why sampling is important, and you have been asked to help her understand.

You need to briefly explain why sampling is a better way of finding out the size of a population of a species.

You're gonna need to write a short paragraph for this, so you'll need to pause the video, write your paragraph, and then press play to check your answer.

Good luck.

So how did you get on with that? You were asked to briefly explain to Laura why sampling is a better way of finding the size of a population of a species.

Things you might have included in your written answer to help Laura are that it would take a long time or be almost impossible to count all of the individuals within the habitat.

You might also have said that sampling is quicker and easier to do and gives a good estimate.

It's actually also cheaper to do as well, 'cause it takes less time.

And finally, you could have included that the population is always changing because of births, deaths and migration.

Well done if you got any or all of those answers.

That brings us to the second part of today's lesson, which is all about ways of sampling different organisms. So if you're ready, let's carry on.

Ecologists use lots of different ways to sample organisms, and it depends on two main things.

First of all, the type of habitat that we're surveying in.

And secondly, the species that are being sampled.

Here are two examples of ways that ecologists and scientists use to sample organisms in different habitats.

We've got a quadrat that's often used in grassland and rocky shores.

And we've also got nets that are used in aquatic habitats but also in grasslands to sample insects and other invertebrates.

Quadrats are square frames, they're used to survey plants and sedentary or slow-moving animals.

That's organisms that stay mainly in one place.

They look like this.

and they're often divided into smaller squares that help us with counting organisms. Quadrats can be used to sample individual populations within a habitat.

They can be used to estimate the number of different species that live in a habitat as a measure of biodiversity.

And remember, biodiversity is the number of different species that live in a habitat.

And finally, they can be used to estimate the percentage coverage of a species in a habitat.

And that's really helpful when there are plants that are really small and really difficult to count.

Usually, quadrats are placed randomly on the ground, just like this.

The species that we are then sampling are counted.

And usually, you have a rule for counting the species in a square so that you don't count the individuals twice.

Now it doesn't really matter what that rule is as long as you stick to it during your sampling.

So the rule that we are going to use for this quadrat is we're going to count any organism that is fully within the square, but we're also going to count any organism that crosses any part of the left-hand side or the bottom edges of the small squares.

We're not going to count any organisms that are not fully within the square that cross the top or the right-hand side edges.

So how many squares is the purple-edged white flower found in? I'm going to pause for a few seconds to give you a chance to have a look.

Remember, we're counting the flowers that are fully within the square or that cross the left-hand side or the bottom edges of the squares.

But we're not counting any organisms that are not fully within the squares that cross the top or the right-hand edges.

I'll pause now, and then you can have a count, and we'll check to see whether you've got the right answer.

So, how many purple-edged white flowers do you think you would count in this quadrat? Well, using our rule of counting any of the flowers that are fully within the square or crossing the left-hand side or the bottom edges, let's see.

We're going to start at the top left-hand corner.

There's nothing there.

In the second square, however, there is a white-purple-edged flower, but it's not fully within the square and it's crossing our top edge.

And remember our rule, we're not counting anything that's crossing the top or the right-hand edge, so that doesn't count.

There are no other white flowers in the top row of our quadrat.

As we move to the second row, there is a white flower within our square here, and it is crossing the left-hand edge, so we count that square.

There are no other white flowers in the second row.

If we get to the third row, there's nothing in the first two squares.

And in the middle square, we've got a flower that's crossing the bottom edge.

And remember, we said we'd count anything that was in the bottom edge.

So there is a count there.

There's nothing else on the third row.

And so we're now going to move to the fourth row, and there's nothing in the first two squares.

But in the third square, we've got that white flower again, but this time it's crossing our top edge and we've already counted it, so we are not going to count it again.

There's no other white flowers in our quadrats.

So the answer is that there are two squares out of the 25 that we found our flower in.

Well done if you got that right.

So quadrats can also be used to estimate the percentage cover of a species where it would be difficult to count them.

So one example is grass.

So what do you think the percentage cover of grass is in this quadrat? I'll pause for a few seconds.

So the grass is found in all of the quadrat squares, so the percentage cover is 100%.

Well done if you got that right.

Let's move on to a check.

Which of the following organisms might you use a quadrat to sample, A, daisies, B, shield bugs, C, barnacles, D, bull finches? I'll give you five seconds and I will check your answer.

So a quadrat could be used to sample daisies and barnacles.

Daisies, because they're plants and they stay in the same place.

But barnacles attach themselves to rocks on a rocky shore, and so they're sedentary, they don't move.

They're really ideal organisms to sample using a quadrat.

Well done if you've got both of those answers.

We're now going to use another type of sampling equipment, and that's called a pooter.

And a pooter is used to sample very small animals such as insects.

We've got a mouthpiece, a tube that's protected by muzzling, a jar, some collected specimens, some specimens out in the habitat.

And it works a little bit like a mini vacuum.

You suck up the animals into the jar.

So we suck from the mouthpiece, that creates a vacuum, and that basically sucks in the specimens into our collecting jar, just like this.

And once the organisms have been identified and counted, then they need to be returned to their habitat safely and securely and humanely.

Let's look at a pooter being used.

Pitfall traps are another way of sampling organisms, and often pitfall traps are used to sample ground-living animals.

Food is often used to lure animals into the trap, and once they fall in, they're not able to escape.

It's really important when you are using a pitfall trap to check them regularly so that organisms are not trapped there for long periods of time.

We use a cover to protect the pitfall trap from rain.

The container has steep sides to stop the organism from crawling out.

And we have that food, that lure, inside the trap to attract the organisms in.

One of the really important aspects of a pitfall trap is to make sure that we've got some drainage holes to ensure that if it rains, the organisms that are within the trap don't drown.

Here's a pitfall trap in real life.

An ecologist is setting it up.

He's probably just put the lure, the food, inside the trap and now is putting a cover over the top.

But you'll also see that there are some screens along the side of it.

Why do you think the pitfall trap is set up like this? I'll pause for five seconds, and then we'll go through why the setup is as it is.

The pitfall trap has been set up like this so that ground-living animals can't actually walk through the habitat, they have to walk around.

And they walk along the screens, which actually mean that they are sampled by the pitfall trap, because there's only one way to get to the other side of the screens, and that's through the gap where the trap is.

So they walk along the screens, they get to the trap, and the ecologist is then able to sample the population before releasing them back into the wild.

Nets are another really useful way of sampling lots of different types of habitats.

A net can be used to sample ponds or rock pools.

A net could be used to sweep along the long grass for insects and other invertebrates.

Or it could be used to sample the organisms that are living within the stones and rocks of a riverbed, something that we call kick sampling.

So let's check to see how well you've understood that last section.

Which of the following organisms might you sample using a pooter? Is it A, dandelions, B, aphids, C, woodlice, or D, snails? I'll give you five seconds.

The correct answer is aphids and woodlice.

Well done if you've got both of those.

Here's another.

Which of the following organisms might you sample using a pitfall trap? Again, five seconds to get your answer, and then we'll check.

The answer here is woodlice and beetles.

Both of those organisms are ground-living animals, and so a pitfall trap is ideal for sampling them.

Let's move to a task.

Lucas wants to survey the school grounds to see what species of carnivorous beetles live there.

Explain, in a short paragraph, the method of sampling that Lucas should use and how this sampling method should be set up to ensure that he catches carnivorous beetles.

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

Good luck.

So you are asked to explain in a short paragraph the method of sampling that Lucas should use and how the sampling method should be set up to ensure that he catches carnivorous beetles.

The best method is using a pitfall trap.

Pitfall traps are great at catching ground-living animals.

How you would set up that pitfall trap up might've included to make sure that the trap was level with the ground, to make sure that the trap is covered, and to add food or a lure to attract the beetles.

Because the beetles that you're wanting to catch are carnivorous, it's a good idea to add some meat.

So your setup should look something like this in the diagram.

Finally, I hope that you included that you should regularly check the trap and release the animals that have been captured.

When we sample organisms, it's really important that we disturb the habitat as little as we can and we don't harm any animals that we're surveying.

Well done if you got those answers.

That brings us to the third and final part of today's lesson, which is all about why we sample organisms. So if you're ready, let's carry on.

So sampling is a useful way for ecologists to estimate the population size of a species within a habitat, to measure the biodiversity, that's the number of different species within a habitat, and to estimate the percentage cover of a species, when we use a quadrat.

That's particularly useful when we're counting small plant species.

Populations of plants are easier to estimate because plants stay in the same place.

Populations of animals are more difficult to estimate, and that's because most animals move around, and some animals only come out at certain times of the day.

For example, those organisms that are nocturnal.

The stag beetle on the picture on the screen, come out at dawn and dusk.

So if we were going to sample these beetles, we'd need to do our sampling at particular times of the day.

One method that ecologists use to estimate populations of animals is called mark-release-recapture.

And this involves capturing a sample of animals, carefully marking them, and we do that using non-toxic substances like a non-toxic paint or nail varnish, we release them back into the population, and then we recapture to see how many marked individuals there are.

It's really important that when we sample animals, we do so humanely, and this includes when we mark animals to make sure that they're not going to be harmed.

So let's look at the process and what it means.

We use a suitable sampling method to catch our animals.

So let's say, for example, we're going to capture some snails, and we've decided that we're going to capture the snails using a pitfall trap.

Here's our snails that we sample.

We then put a harmless mark on them.

There's our harmless mark.

And I've used a red mark, because it doesn't stand out too much, because what we don't want to do is to put something that will attract predators.

We want a mark that we can see and we can recognise but that doesn't stand out, so that it doesn't attract birds and other organisms that might eat the snails.

We then release them back into their habitat and give them a few days to mix back into the population.

And then we do a second sample.

Here's our second sample, and we can see how many of the marked are in that sample, and we can see that there are two there.

So let's look at the results.

We've looked in our first sample, we've sampled 10 organisms. In the second sample, we sampled another 10 organisms, two of which were marked.

So to estimate the population, we use an equation, and that is the number in the first catch multiplied by the number in the second catch divided by the number of marked animals in the second catch.

Let's go through that with our example on the screen.

So the number in our first catch is going to be 10, and we multiply that by the number in the second catch, which was also 10.

10 times 10 is 100.

The number of marked animals in the second catch was two.

So we're going to then use 100 divided by two to get an estimate of our population, which is 50.

Information that's gathered by sampling is important in conservation.

It can be the first step in helping to decide whether species are at risk of extinction.

For example, the tansy beetle is rare in the UK, and it's only found in a few spots in Yorkshire.

Scientists use sampling to monitor the population size.

By using the data, scientists can see where the conservation efforts are successfully helping populations of species to increase.

And in the case of the tansy beetle, they're able to show that the numbers of this beetle are slowly increasing.

So let's do a check.

Sampling organisms helps in the conservation of organisms because, A, it's a cheaper and quick way of knowing how many individuals there are in a population than just counting them.

B, it can help to monitor populations over time to see how successful the conservation work has been.

Or C, it can help to identify species that are at risk of extinction.

I'll give you five seconds to think about your answer, and then we'll check to see whether you got it right.

The correct answer is A, B, and C.

All three reasons are important reasons why sampling helps in the conservation of other organisms. It's cheaper and quicker than counting a whole population.

It helps us to monitor populations of organisms, and it can help to identify those species that might be at risk of extinction.

Well done if you've got all three of them.

Here's our final practise task of today's lesson.

Jacob has been sampling beetles on the school field using a pitfall trap.

He wants to estimate the population of one species of beetle.

He carries out a mark-release-recapture experiment to do this.

Here is the data that Jacob collected.

There were 50 beetles in the first catch, 30 beetles in the second catch, and the number of marked beetles in the second catch was 10.

How many beetles are in the population? Use the equation to help you work it out, and remember to show your working as well in your answer.

Remember, here's the equation: The estimated total population is equal to the number in the first catch multiplied by the number in the second catch divided by the number of marked animals in the second catch Pause the video at this point, work out your answer, and remember to show your working, and then we'll check to see if you got it right.

Good luck.

How did you get on with that? You were asked to tell me how many beetles there are in the population using the equation to help you work it out.

So let's go through what you should have done.

First of all, the total population is the number of the first catch multiplied by the number in the second catch.

That's 50 in the first catch and 30 in the second.

And we divide that by the number of marked individuals in the second catch, which was 10.

Let's do the top part of the equation.

50 multiplied by 30 is 1500.

And we've still got 10 individuals in our marked population.

So now we need to do 1500 divided by 10, and that gives us 150 individuals in our population.

Well done if you got that answer.

So that brings us to the summary of today's lesson.

We've looked at how scientists use sampling to help gather information about populations that live in different habitats, and that includes the estimation of population size.

We've looked at a range of different sampling techniques.

Different types of sampling are used for different types of organisms and habitats.

And some of those examples include quadrats, pooters, pitfall traps, and nets.

And we've seen how animal population sizes can be estimated using techniques such as mark-release-recapture.

Estimating population sizes is an important part of helping to monitor populations as part of conservation projects.

It's been great as always learning with you today.

Thank you for the work that you've put in, and I look forward to seeing you soon.

Take care.

Bye-bye.