Lesson video

Hello and welcome to the first lesson in the unit Ecosystems. My name's Mr. Jarvis and I'm excited to be teaching you today.

In this first lesson, we are going to be learning all about food chains.

By the end of today's lesson, you should be able to describe what producers and consumers are and be able to explain what a food chain diagram shows.

But first we're gonna be looking at some of the key words that we're going to be using in today's lesson.

Those key words are producer, consumer, food chain, population, and model.

You may have heard of some of those words before, but just to make sure, here are the definitions that we are going to be using.

I'll explain them all as we go through today's lesson.

Just pause the video at this point so you can read what each of the words mean before we begin.

Today's lesson is divided into three parts.

First, we'll look at how different organisms get the food that they need to survive.

Then we'll look at what food chains are, and finally we'll look at how populations of organisms change as a result of things that might have had an effect on the food chain.

So if you're ready, then let's begin with the first part where we look at feeding relationships, let's go.

So you may remember that living things carry out life processes such as movement, respiration, sensitivity, growth, reproduction, excretion, and nutrition.

The last of these processes, nutrition, is the way that organisms get the food that they need to survive.

Organisms do this in different ways.

Some organisms are like factories and are able to make their own food, like the sunflowers in this picture.

Some organisms need to eat other organisms to get the food that they need.

For example, the iguana in the picture is eating a leaf from a plant, and the kingfisher is eating a fish that it's caught.

All organisms use food as fuel for cellular respiration.

This provides them with the energy that they need to carry out life processes such as movement.

Plants use the light and chemicals from their surroundings to make the food that they need to survive.

This is by a process called photosynthesis.

All organisms that are able to make or produce their own food are called producers.

Animals can't make their own food.

They rely on other organisms to get the food that they need to survive.

An organism that eats other organisms to get the food that they need are called consumers.

The zebra is consuming grass, which is able to make its own food.

The bear has caught and is consuming a salmon.

The salmon is also a consumer as it relies on eating other animals and plants in the river to get the food that it needs.

All animals and plants are linked together by food.

Animals, including humans, rely on plants for food.

In the pictures, the animals are eating plants, the pig is eating grass and the human is eating a coconut.

Just take a few seconds to think about the plants that you have eaten either today or in the last couple of days.

I'll give you five seconds.

There are lots of examples that you might have thought about.

You may have thought about the vegetables that you've eaten, like carrots, potato, broccoli, or peas.

You may have thought about the cereal that you ate for breakfast or the bread that made up a sandwich.

Both of these have come from wheat.

You might have eaten rice.

All of these foods come from plants.

If you eat meat, you still rely on the plants.

If you eat chicken, where did the chicken get its food from? It's come from the grains of wheat.

Beef burgers come from a cow and the cow gets its food from grass.

Fish get their food from the plants and algae in the water.

All of our food links back to plants.

Without plants, animals would not be able to get the food that they need.

Okay, so let's check what you've understood so far.

Here are a couple of questions.

The first question is, which of the following is a producer? Is it A, a frog, B, grass, or C, a badger? I'll give you five seconds to think of your answer.

You can pause the video if you need longer.

The correct answer is B, grass.

Grass is a plant and plants produce their own food.

The frog and the badger cannot make food for themselves.

They rely on eating other organisms for food.

Let's try another.

Is the following statement true or false? Animals can be producers and consumers.

Once you've decided, look at the sentences A and B, decide which, which of the two reasons is the one that explains your answer.

You may need to pause the video at this point while you think about your answers.

When you're ready, then restart the video and we can check to see how well you've done.

So how did you do? The answer to the first part of the question is false, animals cannot be producers and consumers.

This is because only plants are able to make their own food.

So you should have answered B.

Well done if you got that right.

We are now going to move on to a task for you to complete.

This slide shows some organisms. I'd like you to sort the organisms into two groups.

One group should contain the producers.

The other group should contain the consumers.

You may have been provided with some printed cards of the organisms shown in the video.

You can use these cards to physically sort the organisms into groups, but if you haven't got these, it doesn't matter.

Just draw a table with the headings producer and consumer and make a list of the organism names under the headings.

Before you do the task, you'll need to pause the video.

Once you are done, then come back and we'll check your answers, good luck.

So how do you think you did? Are you confident that you've got them all right? Well, let's see.

Let's look at the producers first.

Remember, these are the organisms that make and produce their own food.

You should have got grass, cress and wheat.

These are all plants and produce food for themselves using photosynthesis.

Now, let's look at the consumers.

Remember, consumers have to consume or eat other organisms to get the food that they need.

Here are the answers.

So sparrows need seeds for food, snails eat leaves, owls eat mice, thrushes eat slugs and snails, mice eat grains such as wheat, cows eat grass, humans eat lots of different foods from both plants and animals, and cats eat birds and mice.

So how well did you do? Did you get them all right? Well, I hope so.

Let's move to the next part of the lesson, which is going to look at food chains.

Are you ready? Then let's go.

So in the first part of the lesson, we've looked at the ways that organisms get their food.

Organisms are either producers, where they make their own food, or they're consumers, where they have to eat other organisms to get the food that they need.

We use a food chain diagram to show how food passes from one type of organism to another.

Here's an example.

Grass, a producer, makes the food that it needs.

Grass is food for rabbits.

Rabbits eat or consume the grass to get the food they need.

A rabbit is food for foxes.

Foxes eat or consume rabbits for food.

The arrows in a food chain show the direction in which food passes from one organism to another.

You need to make sure that you always draw the arrows pointing the right way as it's a common mistake that's made.

The arrows always point to the organism that gets the food.

Food chain diagrams are often simplified.

As you get more confident in what food chain diagrams show you, you don't need to draw them in detail.

You can make them much more simple by writing the names of the organisms and drawing an arrow to show how the food moves from one organism to another.

The example on the screen shows how a simple food chain diagram can be written.

So let's do a quick check on what you can remember.

Look at the simple food chain diagram.

Corn, mouse, owl.

Use the grid to decide whether each of the answers are right or wrong.

You can also decide how confident you are with your answers.

So what do the arrows represent in the food chain diagram? Statement A says the arrows mean eats.

Is that right or wrong? How sure are you? Statement B says, the arrows mean is food for, is that right or wrong? Statement C says that the arrows show the direction that food moves along the food chain.

What do you think? How sure are you? Pause the video, decide whether the answers are right or wrong, and how confident you are with your answers and then come back to check on how well you did.

Let's check those answers.

Statement A, the arrow means eats is wrong.

Statement B, the A means is food for is right.

And statement C, the arrows show the direction that the food moves along the food chain is also right.

So the arrows in a food chain show how the food moves along a food chain.

For example, corn is food for the mouse.

The mouse is food for the owl, let's move on.

So we've looked at producers in the first part of the lesson.

All food chain diagrams start with a producer.

This is because these organisms make their own food.

We've already looked at the food chain that shows grass, a producer, is food for a rabbit, a consumer, and that the rabbit is food for a fox, also a consumer.

We've also learned about how important producers are as they make all of the food for organisms in the rest of the food chain.

Let's look at the organisms on this slide.

We have a lion, a tree, and a giraffe.

Which of the organisms is the producer? I'll give you five seconds to think.

That's right, it's the tree.

The tree makes its own food and is the producer, and this means that the tree will begin the food chain.

The lion and the giraffe both eat other organisms to get their food, so these are both consumers.

The giraffe gets its food from the tree, it eats the leaves and the branches, as you can see in the picture.

The giraffe is a consumer.

Because the giraffe is the first consumer in the food chain, it's called the primary consumer.

Think about your first main school being your primary school.

Primary means first.

So we can start to draw our food chain diagram.

The tree, a producer, is food for the giraffe, the primary consumer, and I'm going to simplify my arrow as we talked about before.

Now let's look at the lion in this food chain.

The lion eats other organisms, and so it too is a consumer.

Giraffe is food for the lion.

The lion is eating a primary consumer.

This means that the lion is the second organism to eat another organism in the food chain.

We call this the secondary consumer.

Again, think of secondary school being the second school that you attended.

So let's look at the food chain diagram.

The giraffe, the primary consumer, is food for the lion, the secondary consumer, and again, we've simplified the arrow.

This example is a simple food chain.

Food chains can be longer than this.

If we get another consumer in the food chain, a third consumer, we call this a tertiary consumer.

So let's do another quick check.

Here's a food chain from the Atlantic Ocean.

You may not have heard of these organisms, but that doesn't matter.

We're looking at the food chain and seeing what you understand.

A group of pupils were spoken to about this food chain diagram and they had the following views.

Which of the views do you agree with? Andeep says that phytoplankton must be producers.

Laura says that phytoplankton could be producers or consumers.

Jacob says it's not possible to decide from the food chain diagram.

Who do you think is right? I'll pause for five seconds, but remember, you can pause the video if you need more time.

When you are ready, we'll check your answer.

So the correct answer was from Andeep.

Although we don't perhaps know what phytoplankton are, we do know that all food chains start with a producer, the organisms that make the food for the rest of the organisms in the food chain.

As the phytoplanktons start the food chain, we know that they're producers.

How did you do? Now let's see how you get on with two tasks.

In the first task, you need to look at the organisms on the slide.

These are a blue tit, a cabbage, and a caterpillar.

I'd like you to draw the food chain diagram for the three organisms and label it with the correct words from the box.

These are producer, primary consumer, and secondary consumer.

For the second task, you'll need the cards that you sorted into groups from earlier.

Don't worry if you haven't got the cards.

You can look at the images and write the organisms down on a piece of paper.

What I would like you to do is to use the cards to construct food chain diagrams for yourself.

There are lots that you can choose from, so you may want to do a few.

When drawing your food chains, label the producers and consumers, and if you're feeling really confident, you might want to decide whether the consumers are primary consumers, secondary consumers, or even tertiary consumers.

Pause the video and then come back so we can check to see how well you've done, good luck.

Well done for having a go at those two tasks.

The food chain diagram that you should have drawn is cabbage is food for the caterpillar is food for the blue tit.

A food chain always starts with the organism that makes its own food.

So the cabbage is a producer and the caterpillar is a primary consumer, the first organism to eat another organism in the food chain, and the blue tit is the secondary consumer.

Well done if you've got got that right.

Moving on to question two.

There are lots of answers that you could have given here, so your answer might not be one that comes up on the screen.

Let's start with the short food chain diagram.

One example is cress is food for humans.

The cress is the producer and the humans of the primary consumers.

There are lots of examples that you could have chosen, but here are some.

Again, you might want to pause the video and see whether you got them all right.

How did you get on? Did you get any other examples? Well done if you did, and a special well done if you managed to label your primary, secondary, and tertiary consumers correctly.

This brings us to the final part of the lesson.

Now we've learned about how different organisms get their food and how to construct and label food chain diagrams, we're going to look at how food chains are impacted by changes to the population.

So are you ready? Then let's begin, and we'll start by reminding ourselves about what a population is.

At the start of the lesson, we looked at this key word.

A population is the number of individuals of one type of organism in a specific place.

Populations relate to all types of organisms. For example, the population of daisies in a field and the population of fish in a pond.

All of the examples describe the size of populations, the number of one type of organism in a given area.

The size of a population is therefore constantly changing.

This is a result of reproduction, death, and migration, moving into and out of the area.

The pictures on this slide represent reproduction, death and migration.

So here's a quick check.

What is the size of the population of humans in the classroom? I'll give you a few seconds to think.

So the population is six.

The population is the number of organisms of one type in a specific area.

If two pupils move or migrate from the classroom, what's the population of humans then? Again, I'll give you a few seconds to think.

That's right, the population of humans in the classroom is now four.

The food chain diagram is what we call a model.

A model is something that makes something easier to explain, and a food chain diagram shows how food moves between populations of different organisms. Although the images that you can see show just one individual at each level, in reality, the individual represents a population of that organism.

For example, here is the population of lettuces in the field.

So let's do a quick check.

Here's a food chain diagram.

I'm going to simplify it by just saying cabbage, slug, hedgehog.

Now I'm going to give you four statements.

For each, I want you to decide whether the statement is right or wrong.

Decide how confident you are in your answers.

Choose the box on the screen that best suits your answer.

I'll give you five seconds between each statement.

Okay, so let's go.

Let's start with statement A.

There must only be three individual organisms in this food chain.

Is that right or wrong? How confident are you? I'll give you some time to answer.

Here's statement B.

There are three populations of organisms in this food chain.

Here's statement C.

The diagram does not show us how many slugs are part of this food chain.

And statement D, the total population size of organisms in this food chain is three.

Okay, so how was that? I hope you didn't find it too tricky.

So statement A is wrong.

Remember, the food chain is a model that represents a population of each type of organism.

Therefore, there are many more than three individual organisms than are represented by this food chain.

Statement B is right.

There are three populations that are shown in the food chain, a population of cabbages, a population of slugs, and a population of hedgehogs.

Statement C is also right.

Although the food chain represents the population of slugs in the food chain, it does not tell us how many individuals there are in this population.

And finally, statement D.

The food chain does not tell us the population sizes.

It just represents the population of each organism.

So the statement's wrong.

I hope you did well.

So how does a population size affect other populations in the food chain? Well, let's remind ourselves that a food chain shows how food is passed from one population of organisms to another.

Look at this food chain diagram.

Here's our population of lettuces that are growing in a field.

These lettuces are being farmed by a farmer, and when they're ready to sell, the farmer harvests the lettuces and leaves only the small number of lettuces behind that can't be sold in the shops.

The food chain shows us that the lettuces are the producer, and we know that the producer makes all of the food for the rest of the food chain.

So if the farmer harvests all his lettuces, what do you think will happen to the populations of other organisms that are found within the food chain? I'll give you some time to think.

Let's look at the numbers of lettuces.

If we start with a high population of lettuces and the lettuces are harvested, the number of lettuces will start to go down.

This is until the point that only the lettuces that are left behind in the field remain.

And you can see that the population of lettuces is much smaller.

Our food chain diagram showed that slugs were the primary consumer.

They ate lettuces.

As the population of lettuces in the field reduces, there is less food for the population of snails in the field.

And so, their population decreases too.

This is a result of them dying because they haven't got enough food or because they might migrate somewhere else, where there is food for them to eat.

So the less food for snails means that the population of snails will decrease also.

Let's look at the two populations together on the same graph.

The lettuce population is shown with the blue line and the snail population with the red line, and we can see how the populations impact on each other.

You can see that as the lettuce population reduces, the snail population reduces too because there is less food for the snails to eat.

Our food chain diagram showed that lettuce is are food for snails.

Snails are food for thrushes, and thrushes are food for hawks.

So what will happen to the population of thrushes and the population of hawks? You can pause the video if you need some additional time.

So the fewer snails mean that there is less food for the thrushes, which mean that the population of thrushes will also decline.

If there are less thrushes, then there's less food for the hawks and their numbers will decline too.

So by reducing the size of the producer population, we are impacting the whole of the food chain.

So a food chain diagram is a model that helps us to understand things more simply.

We can use this model to help us make predictions.

Let's think about the population of hawks in the same food chain.

What do you predict would happen if the population of haws increase in size? Firstly, think about the population of thrushes.

What do you predict will happen to the size of the thrush population? So if there are more hawks, more thrushes will be eaten for food and as a result of this, the population size of the thrushes will decrease.

How will this affect the population size of the snail? So if there are fewer thrushes, there'll be less snails that get eaten.

As a result, the population of snails will increase in size.

And finally, what about the population of lettuces? What do you think will happen to them? So the more snails there are, the more lettuces will be eaten.

This means that the size of the lettuce population will decrease.

Let's move on to our final check of what we've learned in this lesson.

This is a multiple choice question.

Choose the answer that completes the following sentence.

If a disease decreases the population size of primary consumers in a food chain, A, the population of producers will increase, B, the population of secondary consumers will increase, or C, the population of producers will decrease? If you want to pause the video to give you more time, you can do so.

The answer is A, if the disease decreases the population size of primary consumers in a food chain, the population of producers will increase.

This because is because there are less primary consumers and that means less of the producers will be eaten.

Well done if you got that one right.

Now it's time for our final task.

I'd like you to look at the food chain diagram.

Flowering plants, bees, birds, the population of bees is getting smaller very quickly.

The class has different views.

Aisha says it will not affect any other organisms. Lucas says it will only affect the birds.

Sophia says it will only affect the flowering plants.

Jacob says it will affect the birds and the flowering plants.

Who do you agree with? Write down an explanation as to why you've chosen that person.

Pause the video and come back when you're ready to check your answer.

So how did you do? The person with the right answer was Jacob.

If the population of bees reduces, then it will affect the birds and the flowering plants.

Here are some of the key points that you might have included in your explanation of why it's the right answer.

You may have some other points which are valid.

Add any points to your own answer if you didn't include them.

You've worked really hard today, well done.

We've reached the end of the lesson.

The last thing for me to do is to just go through what we've learned today in our lesson about food chains.

So we've learned that food chain diagrams are models which show how food passes from one type of organism to another.

We know that the arrows in a food chain diagram show the direction of food as it moves through the food chain.

We've learned that food chains always start with a producer, such as a plant, and producers make their own food.

We've learned that consumers rely on other organisms as their source of food, and we've learned that a change in the size of a population in any part of a food chain will affect other populations within that food chain.

Well done today, I hope that you've enjoyed the lesson and thank you for all the hard work that you've done, bye.