Lesson video

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

The title of today's lesson is "Fruits and seeds." And that's what we're going to be looking at today, how fruits are formed and what they are, and what those seeds are inside fruits, what's inside those seeds, and what their role is.

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 how fruits are formed and how the structure of a seed enables germination.

So in today's lesson, we've got some key terms, and those key terms are seed, ovary, fertilisation, embryo, and fruit.

Now, we will be going through those in each part of the lesson, but if you want to write them down, I'll put the slide up now for you.

Okay, so our lesson today is in three parts.

Part one is seeds, part two is fruit, and part three is seed dispersal.

So we're gonna start by looking at what seeds are now.

So here we go.

So seeds are a development stage in the offspring of a plant.

So we've got two parent plants here, and therefore they are both involved in producing this offspring.

It is produced by sexual reproduction.

And sexual reproduction is when the DNA of both parents is joined together in fusion during fertilisation in order to form a new offspring.

Now, that offspring forms through various developmental stages.

So we can see here that the gametes, the sex cells of the parent plant, are pollen, which is the male gamete, and an ovum, which is the female gamete.

And in their nuclei there, they've got DNA.

And that DNA is stored in chromosomes, which you will have learnt about before.

And when those two come together during sexual reproduction, we make a seed, and that seed is going to be the offspring of both of those parent plants.

So seeds are living organisms. Sometimes people don't think that they are because they don't seem to really do very much, but they are living organisms, they're made of cells.

Now, it might be that in this part of their lifecycle, they don't carry out all of the common processes of living organisms, but at some point in the plant's lifecycle, they will carry out all of those common processes.

So seeds is the first stage in the development of the offspring of a plant, and we can see the stages that it goes through here.

So they are formed from the fusion of gametes to start with, and then they'll develop and grow into offspring which resembles the parents.

So we start with gametes, and then they come together in fertilisation, and that happens in the ovary of a plant.

So we've talked about pollination and fertilisation in earlier lessons.

And then a zygote will be formed in the ovary of the plant, which then develops into an embryo.

It then goes on to form a seed, and that seed will be in the ovary of the plant.

And then when that seed is eventually planted, it will sprout if the conditions are correct.

Through germination, a sprout will form.

And then we move on to a seedling being able to grow and develop.

So let's have a little look close up inside the ovary of a plant here.

So as we've said, seeds form in the ovary of a plant after fertilisation.

So if we zoom in here on the ovary of a plant, we can see through the cross-section of this flower here.

Then this first stage here is the zygote, so that's when your gametes fuse together.

And then we move on to the next development stage, which is the embryo.

And then we move on to the seed there, which forms inside the ovary.

So, let's see if you can put the development stages of the seed into the correct order.

So we've got embryo, seed, zygote, and gametes.

So have a little go at this, pause the video, and then we'll see how you've got on.

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

So the first stage is the fusion of the gametes there at the bottom.

And then the second stage is a zygote, so when those gametes fuse together.

And then we get to embryo, and then finally we get to a seed.

So if you got those right, then well done.

So the seed is made from the embryo of a plant and its food supply.

So this is a cross-section through a seed so you can see what's inside it.

So you can see most of the seed is actually made up of this food store.

So the scientific name for this food store is the endosperm, but you don't need to recall that.

You just need to know that there's a big food store in there.

You can see the embryo, which is sort of the starter of a new little plant.

It's not a true plant, but it does have some tissue that is going to become leaves and roots.

And then you've got a seed coat around the outside, which is a tough outer coat which protects the seed.

Often, it's waterproof as well.

Now, on most seeds, you'll see that they've got a little scar on them, and that's why they were attached to the ovary inside the plant.

It's called the hilum.

Again, it's not a key word that you necessarily need to recall, but it's an interesting thing to look out for when you see seeds because then you know where they're actually from.

So let's look at this in some real seeds.

So we've got here a cashew seed.

So this is the tree that it's from, the cashew tree.

And if you cut open a cashew seed, you can see, inside we've got the embryo there, and then we've got a food store, and then round the outside, we have got a seed coat.

And then we've got a pistachio tree here.

Some of you might recognise these nuts.

And it's got an embryo here, and it's got a food store, and it's got a seed coat.

Now, you might call these nuts a cashew nut or a pistachio nut.

In scientific terms, these are actually seeds.

They're seeds because they form inside a fruit, and they have all of the key identifiers that make them a seed.

So they have the food store, the embryo, and the seed coat.

And if you've got any of these at home, you could have a go at doing this yourself as long as you soak them in water for 24 hours beforehand.

And you need to make sure that you have somebody who can check on your safety if you're cutting them open.

And then you can have a little look at these things inside the seed.

So let's have a look at another two examples.

So we've got the almond tree here, and that's the fruit of the almond tree, and inside that is the seed of the almond.

And again, you can see its embryo, you can see its food store, and you can see its seed coat.

And finally, we've got pumpkin seeds here from a pumpkin plant.

They've got really big fruit.

We see them all at Halloween.

And we've got here the embryo in there, and the food store, and finally the seed coat around the outside.

So maybe you can look out for this in some seeds that you might have in your kitchen or out and about.

So true or false? Let's do a quick check.

The seed is the embryo of the plant.

So I want you to decide whether that's true or false.

And once you've decided, which of the statements, A or B, do you think best justifies your answer? So pause up while you decide, and then we'll see how you've got on.

Okay, so let's see what you chose then.

So the correct answer is false, and the statement that best justifies why that is false is because the seed is the development stage of the plant which contains the embryo and food stores.

So it's not just the embryo, it also contains the food stores.

So next task for you to do is to match the key terms to the correct definition, okay? So the definitions are already written there for you.

Maybe start with the ones that you definitely know first and then work backwards from there.

Again, pause the video while you have a go at this, and then we'll check back on your answers.

Okay, let's see how you got on.

So the hilum there is the scar where the seed attaches to the inside of the ovary.

And the embryo is the early stage of growth and development of the offspring.

And the seed coat is the tough outer layer that protects the seed.

And the endosperm is the food store to provide nutrients for the embryo.

So if you got those right, then well done.

And then let's move on to our next practise task.

So we've got some pupils who are talking about what they think a seed is.

And Laura says, "I think most of the seed is a food store that is used to germinate and grow." And Jun says, "If you cut the seed open, you will find more seeds inside." And Sam says, "I think the seed contains a smaller version of the plant which gets bigger." And Sofia says, "I think the seed contains the embryo plant, which has a small root and leaves so it can germinate." So what I would like you to do is choose the pupil, or the pupils, that you think are correct and explain why their answers are better than the others.

So it'll take you a little bit of time to write these sentences.

So pause the video, and we'll come back and have a look at your answers after.

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

So the first task was to choose the pupils that you think were correct and explain their answers and why their answers were better than the others.

So Sofia and Laura had correct ideas.

The seed does contain the endosperm, which is the nutrient store, and the embryo plant has root and leaf tissue ready to germinate.

Sam understands that some different plant organs are formed but not what an embryo really is.

And Jun has not understood that one seed grows into one plant.

So if you got some answers that were similar to those, then well done, particularly if you picked the right students who had the correct ideas.

So it's time now to move on to the second part of today's lesson, which is fruit.

The seed forms in the ovary of a flower after fertilisation.

So you can see here a cross-section through a flower, and we've got the ovary and the seed forming in there after fertilisation has taken place.

So that's when the pollen cells and the ova have fused together.

The ovary contains the ovules and the ova.

So the ova are the female gametes of a plant, a flowering plant, and it's where the seed develops and grows.

So again, you can see a cross-section through a daffodil here.

And you can see the ovary, and those little blobs there, those are the ovules, and they contain the ova.

Once fertilisation has taken place, the flower is no longer needed.

Remember, the job of the flower is to attract pollinators so that the pollinators come to the flower and they drop off the pollen on the stigma so that it can go down a pollen tube into the ovary.

So once those pollinators have been and gone, then that means that the flower isn't needed anymore.

So the flower will die, but the seeds will be stored in a pod that is made from the ovary of the flower.

So we can see the flower dying here, and then the seeds of the daffodil will be stored here.

Now, daffodils are interesting 'cause they also form bulbs, but they can form seeds as well.

So in some plants, the ovary becomes the fruit.

So the fruit is the ripened ovary of seed-producing plants.

Now, it can be fleshy or dry.

So you can see in these examples here, we've got a pomegranate and a kiwi and an apple.

And we can see the ovary there, and it's become very fleshy, often quite sweet because that also attracts animals to eat it in order to disperse seeds, which we'll talk about later.

And we can see inside that fleshy ovary the seeds of those fruits.

So those are inside there, ready to develop into a plant per seed if they meet the right conditions.

So the scientific definition for a fruit is actually different to the ones that we use in food.

So some food that we would call vegetables is actually a fruit.

So here are some examples here.

So we've got an avocado, we've got a pea pod, and a pepper.

And we can see here, that is the ovary.

So the fleshy section there is the ovary that has ripened.

And inside that seed, so we've got the avocado seed, we've got the peas, which are seeds, and we've got the seeds inside a pepper.

So time for a quick check.

Select the images here that contain fruit.

So we're looking at the scientific definition for a fruit.

So pause up while you make your decision.

You might want to discuss it, and then we'll come back and see how you've got on.

Okay, so the correct answer is, a cucumber is a fruit, as is a conker.

I'm sure lots of you have seen these lying around in the autumn.

Both of these are fruits because they've got seeds inside and the ovary has become fleshy, although in some cases, the ovary becomes more fleshy and sweet than in other cases.

And the carrot is not a fruit because the carrot grows in the ground, so it's part of the root system of a plant.

So that one is a vegetable.

So we've got a practise task for you here.

So we've got two students, Aisha and Lucas.

And Aisha says that she has made a side salad from vegetables to go with my main meal.

And Lucas says he has made a fruit salad for dessert, but he says, "Your salad also does actually contain fruit." Now, Lucas is correct, scientifically speaking.

So could you explain to Aisha why all of her side salad is not made of vegetables? So while you decide how you would explain that to Aisha, please could you pause the video, and then we'll come back and we'll see if you've got the right understanding.

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

So Aisha and Lucas were using fruits and vegetables in their meals.

And Aisha said that she'd made a side salad from vegetables, and Lucas said he'd made a fruit salad, but he said that Aisha's salad also contained fruit.

So let's see if we can explain to Aisha why her side salad isn't just made of vegetables.

There are cucumbers and tomatoes in that side salad there, and they contain seeds.

The flesh of the cucumber and the tomato is the fleshy, ripened ovary of the plant.

So therefore, scientifically speaking, cucumbers and tomatoes are fruits.

So Lucas was right.

Okay, it's time to move on to the third part of today's lesson, which is seed dispersal.

So seeds must be spread away from the parent plant after they're formed, and they must be spread away from each other.

The reason for this is to reduce competition because when those seeds land and they start to develop and grow, they need to be somewhere where there's enough space and water, minerals, sunlight.

And if they're too close to the other seeds or their parent plant, then they're gonna be competing for those resources, so they're less likely to germinate and grow to form a successful plant.

When seeds are spread away from their parent plant, this is called seed dispersal.

And plants have lots of mechanisms in order to make sure that their seeds are dispersed as far as possible to give them the best chance of survival in growing into offspring.

So we can see in this example here, something that we see all the time is these dandelions, and that's the parent plant, and its seed there floating away is being carried by the wind.

So seeds can be dispersed by the following mechanisms. So by animals, by wind, by explosion.

I don't if you've ever seen some of these balsam where sometimes if you just flick them a little bit, then they burst open and the pod peels back and the seeds fire out.

They're often in the sort of woodland or near water.

So look out for them next time you're out and about.

And then we've got water, they can be carried by water.

This is a lotus flower, and this is its seed pod here.

So animals disperse seeds in three ways.

So animals are really important in seed dispersal.

So one, they might eat the seeds.

So particularly when those seeds are inside fruit and the fruit is tasty, the animals might eat it.

Or sometimes things like squirrels might pick them out from inside of fir cones.

So the seeds are very nutritious as well as the fruit itself.

And when they eat them, they'll move through the animals' digestive systems, and then they'll come out in their waste somewhere else.

They might also carry them on their surface.

This frog doesn't look very happy about being covered in seeds.

But also, some seeds have little hooks on them so they hook onto the fur of passing creatures.

So therefore, they will then transport them greater distances.

The other thing that animals might do, these squirrels again, is that they might bury seeds.

So they'll collect them, and then they bury them for the winter when there isn't enough food around, and then they can go back and find them again.

It's very clever.

So seeds will have adaptations in order to increase the chance of dispersal.

Remember, plants are adapted to ensure the survival of their offspring.

So these adaptations have happened over time in order to increase this chance of survival in their offspring.

So some seeds will have hooks on them, and they can catch onto the fur of passing animals.

Some will have a shape, like a large surface area like this, or little wings, in order to aid their movement by the wind.

Then some of them have fruit, which is tasty, and that encourages animals to eat them.

Small animals or birds eat them.

And then some of them have a really waterproof coating so that they can be carried away.

And they might be hollow inside, so that makes them float, so they've got really low density.

So looking at these examples here, time for a quick check, which of the seeds will be dispersed by the wind? So from what you can see of them and their adaptations, which ones will be dispersed by the wind? So have a quick discussion, pause the video, and then we'll check back.

Okay, how did you get on with that one? So hopefully you got that dandelion and milkweed are both dispersed by the wind.

So they're very light, and they've got those little wings on them so that they're carried easily.

This oak acorn is not dispersed by the wind.

It would be far too heavy to be carried by the wind.

Okay.

Squirrels help with that one, though.

So time for a practise task.

This is the picture of a strawberry.

It is the fruit of a strawberry plant.

So we can see on this strawberry fruit, we've got the seeds that are on the outside of that fleshy fruit.

And then we've got what remains here of the petal of the flower.

So use your knowledge of seed formation and dispersal to explain why there are petals attached to the top of this fruit and why there are seeds embedded in the flesh.

Now, this is quite a long piece of extended writing, so you should try to include the words pollination, fertilisation, and ovary in your answer.

And if you do, I'm sure that your answer will be very detailed.

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

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

So this is quite tricky.

It's a summary of everything that's been covered.

So explain why there are petals attached to the top of this fruit and seeds embedded in its flesh.

And we're gonna use these key words, pollination, fertilisation, and ovary, in the answer.

So, let's start with the petals are part of the flower that would have attracted the pollinators for pollination.

So we're using the key word there.

And the male gametes from the pollen fuse with the ovum during fertilisation in the ovary.

So again, we've used two of our key words there.

An embryo and then seeds are formed.

And then the ovary becomes the ripened fruit.

And then an animal will eat the fruit and digest the seeds, and then these will be dispersed in another place in the animal's waste.

So if you got all of those ideas correct, then well done 'cause there was a lot to include there.

And now we come to the summary of today's lesson.

So seeds are a development stage in the growth of a plant offspring.

Gametes fuse to form a zygote and then develop into an embryo and then a seed.

Seeds contain an embryo, food store, and a tough outer coat.

They are formed in the ovary.

A fruit is the mature and ripened ovary of a plant.

The flesh of a fruit is eaten by animals, which transport seeds as one method of seed dispersal.

Seed dispersal allows competition to be limited as all the seeds of a plant will need space, minerals, water, and light to germinate and grow.

Seeds are also dispersed on the surface of animals by wind and by water.

So well done for your work in today's lesson.