Hello and welcome to this lesson from the unit Reproduction in Plants.

The title of today's lesson is Seed Dispersal: Practical.

So today is a practical lesson, and I hope you get the opportunity to take part in it.

You just need some paper and scissors.

We're first gonna look at seed dispersal and why plants need to do it, and then we're gonna have a go at setting up a practical and carrying out a practical into this mechanism.

My name's Mrs. Barnard, and I'm going to be taking you through today's lesson.

So by the end of today's lesson, you should be able to explain why this is important to a plant, that its seeds can be dispersed over a wide area, and also you're gonna carry out an experiment to measure seed dispersal.

So we've got some key words for today's lesson, and those key words are seed dispersal, adaptations, variable, repeats, and mean.

Now we will be going through each of these words in the lesson, but if you'd like to write down the definitions, then you can do that now just pause the video.

So our lesson today is in three parts.

The first part is seed adaptation, so what they are and why they are important.

The second one is setting up our practical for seed dispersal.

So looking at the different variables we could investigate.

And finally, we're gonna carry out that practical, and we're gonna collect our data.

So let's get started with the first part of today's lesson, which is seed adaptations.

So just a little bit of a reminder for you, seeds are living organisms, they are made of cells.

Now, they don't carry out all of the common processes of living organisms, but they will do at some point in their lifecycle.

So a seed is formed from the fusion of gametes in the ovary, and then a seed will be formed, and eventually that seed will grow in the ground and it will become a seedling and then a plant.

And then eventually, that plant will resemble its parents.

So a seed has the same basic structure.

They all contain an embryo, they contain a food store, and they have a seed coat.

So here, you can see that on this pistachio seed here.

I know sometimes we call them pistachio nuts because we eat them for food, but they are actually seeds of the pistachio tree.

And you can see inside there's a little embryo there.

The bulk of the seed is the food store.

And then finally, we have the seed coats around the outside.

Now, if you get the opportunity to look at these seeds at home, you can do, just need to soak them in water overnight, and then you can cut 'em open and you can see that embryo inside the seed.

So seeds must spread far away from their parent plant and also away from each other.

So a plant is gonna produce lots of seeds, and it's important that all of those seeds have the opportunity to grow into new plants.

And the best chance of that is that if they can find their own space, and that is because all seeds are going to compete with each other and they're going to compete with space.

So space to grow, so for their roots, for their leaves, water and sunlight that are required for photosynthesis, and minerals that are required for growth and other processes in the plant.

So in order to reduce competition, they need to spread away from their parent plant and away from each other.

And when seeds are spread away from their parent plant, this mechanism is called seed dispersal.

So seed dispersal can occur by the following mechanisms. So first of all, we can use animals.

So animals may have the seeds catch on their fur, or they may eat them, and they may pass through their digestive system and out in waste in a different location.

The wind can disperse seeds.

They can disperse by explosion.

So this is a balsam.

So you might see this sometimes if you're walking in woodland or near water, and it's got these little pods.

And if you flick them, then they explode, and the seeds come out, and the pod curls up.

It's pretty cool.

And then finally, by water.

So this is a lotus flower.

So it seeds here, you can see they're waterproof.

They're often have very low density, so they're very light, so therefore they can float.

So seeds have adaptations that increase their chance of dispersal.

So here's an example of a seed that has hooks on it, so lots of hooks, so therefore it'll catch on the fur of passing animals, and they'll be dispersed that way.

And here's an example of a seed that would be dispersed by the wind.

So it's got those wings, got a shape, a large surface area in order for it to be able to be caught by the wind.

Then we've got lots and lots of plants produce fruit with seeds in, and that encourages animals to eat them because the fruit is a food source for them.

And then their seeds will pass straight through the digestive system of those animals.

And then finally, we've got some seeds that will be dispersed by water and they have a waterproof coating, and they often very light or hollow so that they can float.

But what we're gonna do is we're gonna focus on seeds that are wind dispersed this lesson, and they will have common adaptations.

Can you think of what common adaptations a seed would have to have in order to be dispersed by the wind? Perhaps talk to the person next to you while you think about the answer.

Okay, so here are a few examples of seeds that are dispersed by the wind.

So we've got dandelions.

That might be quite a familiar one to you all.

Got hogweed, milkweed, and sycamore, and you can see that some of them look more similar than others.

You've got the dandelion and the milkweed that look quite similar with those light, feathery structures that come out so they can catch the wind by increasing the surface area and being very light.

The hogweed there are very light, they don't have the same projections that come out of them, but they're sort of papery and light, so they can float on the wind.

And then finally, we've got the sycamore, with its large surface area and wings, so that it also can be dispersed by the wind.

So wind-dispersed seeds must be light, and they may have a large surface area.

So time for a quick check.

Choose the adaptations that you think would help a seed to be dispersed by the wind.

So pause the video while you decide, and then we'll come back and check how you got on.

Okay, so the correct answers are they have a large surface area and they have a low mass.

Those things help them to be dispersed by the wind.

So if you've got those correct, then well done.

So we've got two pupils here, Izzy and Sam, and they are designing seeds from paper to test on a vertical fan.

Now you sometimes see these vertical fans in science museums if you've had the opportunity to go to any of those, and you can have a go at designing seeds and seeing how they float.

But we could just do this in the classroom with a fan that is facing upwards.

So first of all, out of Sam and Izzy's two models, which one do you think, from your knowledge of seed dispersal, will lift higher? And secondly, if you could get some paper and design your own seed and test it, see if you can get a seed to lift and disperse based on a design that you have come up with.

So you'll need a bit of time to do this.

So come back when you're finished, and we'll see how you've got on.

So in this example, Sam's seed would lift the highest as it has the largest surface area.

And for the second task, if you managed to make a seed that did lift up and disperse, then well done.

You've made a good seed model.

So now it's time to move on to the second part of our lesson.

So now we're gonna be looking at our practical, and we're gonna be looking at the variables we could investigate.

So in order to carry out our practical today, we're going to use the same seed model for everybody.

So even though you designed a seed model in the, in the first part of the lesson, we're going to use this template here.

So this is the template that you'll need.

And in order to make your seed models, you'll need to cut along the solid lines and fold along the dotted dashed lines.

So once you have cut and folded, your seed model is now ready to test.

So you need to drop your model seed, and you need to measure the distance that it has moved from the point where you dropped it.

So step one is to mark a cross on the floor.

Now you might want to use a piece of paper that's already got a cross on it, or you might have some chalk to mark the floor.

And then, number two, you're gonna drop the seed over the cross.

And then number three, you are gonna measure the distance that it has dispersed from that point.

Okay, so now we've got a working seed model.

It's time for us to plan our investigation.

So a variable is a factor that might affect the process that we are investigating.

And we are investigating how far a seed disperses, and therefore our dependent variable, the things that we are measuring, is the distance that the seed lands from the point that it was dropped, which is marked by the cross.

So that is our dependent variable for this investigation.

So therefore, there are a number of different variables that are going to affect that distance.

What do you think some of those variables might be? Now, in order to do that, you need to consider the method that you're using, so there's that picture there to help you.

And also, look at the seed template.

What things could we vary that might affect where the seed lands? So you might want to have a conversation about this, and then I'll give you some of my answers on the next slide.

Okay, so some of the variables that might affect where that seed lands, and this won't necessarily be them all.

So first of all, the height that the seed has dropped from.

So that's gonna affect, possibly, how far it disperses.

And then, looking at the seed template itself, the wing width may affect it, the wing length may affect it, the tail length may affect it, and we could add different layers of mass.

So you might want to add different masses of blue tape or paperclips, different numbers of paperclips to the bottom of the tail.

So there's different ways that you could add a measurable amount of mass to the tail.

Okay, so time for a quick check.

So you are going to investigate wing length and how it impacts seed dispersal.

So the dependent variable, therefore, is wing length.

Now, is that statement true or false? That's the first thing I want you to think about.

So just pause the video while you choose.

Okay, then.

So that statement was false.

Now which of these two descriptions below do you think best justifies the false answer to that point above? So is it the dependent variable is the distance the seed model travelled, or is it the wing length is the control variable? Which ones of those best justifies that false statement? Okay, so the correct answer is that the dependent variable is the distance the seed model travelled.

Okay, so if you got that right, then well done.

So let's move on.

So now you need to select a variable that you would like to be your independent variable.

So this is the thing that you are going to change in order to investigate its effect on where the seed model lands.

So how far the seed disperses.

Now all of the other variables that we looked at in the previous slides, therefore will become your control variables because those control variables are all the other factors that could affect where the seed disperses, but we are not investigating those, so we need to keep them the same.

So just a reminder of the other variables.

We've got height that it's dropped from, wing length, wing width, tail length, and any mass that might be added.

So time for a quick check.

I want you to select the possible control variables for this seed dispersal investigation.

So pause the video while you do that, and then we'll come back and we'll see how you got on.

Okay, let's see how you got on with that then.

So we've got width of wings.

That is a control variable.

Length of wings is a control variable, and number of wings is a control variable.

The distance the seed disperses is not a control variable because it is our dependent variable for this investigation.

So in this seed dispersal investigation, the dependent variable is the distance the seed has landed from the point it has dropped.

So the seed dispersal as we've already said.

And if this is only measured once, the result might not be reliable.

So to ensure that the first measurement is accurate, we need to take repeat measurements.

Repeating a measurement allows identification of any results that don't fit a pattern.

And these results are called anomalous results, or sometimes anomalies.

So here's an example here.

So in this table, it looks like, you can see, that the independent variable in the first column is length of wings, but we're only looking at one value for this one, for this example.

And the length of the wings was three centimetres.

So having made a seed with length of wings three centimetres, it was dropped and then measured five times, and you can see the results at the bottom.

So one of those results really looks like it doesn't fit the pattern.

And this is number five.

So you see, the other values are quite close to each other.

So number five doesn't quite fit the pattern.

It's 52, so we'd say it an anomalous result.

Now, when we have anomalous results, what we do is we don't include them in our mean.

So repeat meanings can be calculated into a mean.

So a mean is an average.

So the length of the wings in this one, it was five, and three repeats were carried out.

And we can see that number two repeat was anomalous.

So we would discount this result.

So therefore, in our mean, we would only include two values.

So therefore, we would do at 10 plus 12, which is 22, and then we would divide it by two, which is the number of repeats we included.

So therefore, our mean is 11.

So let's have a go at doing that again.

You can do this one by yourself.

So in this one, I'd like you to calculate the mean for this set of repeats measurements.

Now this time there is five repeat measurements, and it's for a different length of wings.

So pause the video while you do that, and then we'll see how you got on.

Okay, so in this one we had anomalous result here, which was number three.

And you can see that that number five is quite different from the other four results.

So therefore, we are going to include four measurements in our mean.

So we add those four together and we divide by four, and our mean number therefore is 17.

So therefore, that's what we would put in our table.

So this gives us a more reliable result for the effect that changing the wing length has on the distance dispersed because we're repeating it, we're removing anomalous results, and we're calculating a mean from the other repeats.

So time for a task now.

So Izzy is going to change the length of the wings on her template, and this will be her independent variable, so therefore, it goes in the first column of the table.

She will test three lengths and she will carry out three repeats of each, and then she will calculate a mean.

So your first part of your task is to decide which variable will be your independent variable in your investigation.

And number two will be to draw a table which includes the values that you will measure.

So you can use Izzy's to help, so you know how to set out your table, but you need to decide what you want to have in that first column as the independent variable.

You need to decide which values you are going to measure underneath, and then you will need to decide how many repeats you're going to do before your mean, and then draw that table.

So you need a little bit of time to do this.

Make sure you use a pencil and a ruler, and try to use the full width of your paper so it's really clear and easy to read.

Okay, so come back when you're done, and we'll see how you've got on.

Okay, let's see how you got on with your table then.

So first of all, decide on your independent variable.

So just an example, width of wings, you might have done length of wings, mass, height dropped from, and then you should have drawn a table which included your independent variable as the heading at the top of your first column with the units.

So in this case, it would be width of wings in centimetres.

And those width of wings, the values that we decided on were 1, 1.

5, 2.

So whatever values you decided on.

You might have had three, or four, or five different values.

And then the number of repeats that you wanted to do would be underneath your title, which is the distance that the seed dispersed for our dependent variable in our second column.

And then we should have a mean also in there.

So if you've drawn your table correctly, then well done.

So it's time to move on to the final part of our lesson today, which is actually carrying out the practical and collecting the data.

So here is a method for your seed dispersal practical.

So make your seed models using the template, change the template as necessary to match your chosen independent variable.

Draw a cross on the floor with chalk, or you might wish to do it in a different way.

Stand with your feet on the floor, your hand out and over the cross, and drop the seed model.

Use a ruler to measure from the cross to where the seed model lands.

You need to repeat steps four and five two more times in order to get a mean.

You may wish to do it more.

And then repeat steps four to six with a new value for your independent variable.

So making a new seed model and repeating it again.

This information is on a sheet you can actually read, but also there is a video which I will show you now.

Okay, so hopefully that video clip made it clear about how you're going to carry out this investigation.

But let's just double check.

So from these images, can you select two where the method is not being carried out correctly? Okay, so just pause the video while you decide, and then we'll come back and we'll see if you've got it right.

Okay, so the incorrect images are B because she's standing on a stool and it says stand on the floor.

That's really important for health and safety.

If you want to change the height, you just need to move your hand up and down to a certain measured height.

And C is incorrect 'cause we can see that the ruler isn't measuring exactly to the point where the seed fell on the floor to the middle of the cross.

So we need to make sure that we are measuring accurately.

Okay, so while you carry out this investigation for your practise task, you're gonna need to collect the information in your table that you drew in your task earlier on in today's lesson.

So it's gonna take you a little bit of time to do this practical, so we'll come back at the end and we'll check that you filled in your table correctly and that you've got a full set of data.

Okay, I hope everyone had a chance to do that practical work.

So let's have a little look at your table and how you've set it all out.

So you should have your values that you measured and your repeats in the correct rows, and then you should have calculated a mean.

Now, if you have calculated a mean, have you removed any anomalous data that wasn't required in that mean before you did it? So if you did, then that's great.

Well done.

You've got a full set of data, and you have carried out the investigation correctly.

So now it's time for a summary of today's lesson.

So seeds are dispersed by different mechanisms to transport them away from the parent plant and each other to aid survival.

Seeds have adaptations to match the mechanism used for seed dispersal.

Wind-dispersed seeds will be light with a large surface area.

In a scientific investigation, factors that affect the process being studied are called variables.

In the seed dispersing investigation, the distance that the seed travels from the point it was dropped was the dependent variable.

The variable that is being changed is the independent variable, for example, length, width, mass.

All the other variables must be kept the same, the control variables.

Repeat measurements of a value ensure that the final result is reliable.

It allows anomalous results to be identified and for a mean to be calculated.

So well done for your work on today's practical lesson.