Hello, welcome to today's lesson.

My name is Mrs. Mehrin and I'm so excited to be learning all about changes in food chains with you, let's begin.

Welcome to today's lesson from the unit, more about food chains.

Your learning outcome is, I can explain why change to the population of one living thing can affect the population of other living things in the same food chain.

So we're going to be building on some of your previous learning all about food chains.

But I know that learning can sometimes be a little bit challenging, but that's okay because it just means that we are going to work really hard together and we're going to learn lots of fabulous new things.

And let's begin.

So here are your five key words for today's lesson, and alongside them are the definitions.

I am going to be referring to these throughout today's video.

However, if you find it helpful, you can pause the video here and jot these down.

Off you go.

Fantastic.

Well done.

So our lesson is split into two parts.

Let's begin with the first part, understanding food chains.

So Laura and Alex have been on a walk in their local environment looking for examples of food chains.

And Laura says, "Here is an example of a consumer eating a producer." And Alex says, "Here is an example of a predator eating its prey." Alex presents a food chain to show how some living things in the local environment depend on each other for food.

So a caterpillar depends on a leaf for food or a plant.

Robins depend on caterpillars for food.

And foxes depend on birds like robins for food.

Now, Alex says, "I wonder what would happen to the robin if the caterpillar wasn't there for it to eat." And what Alex means by that is if the population of caterpillars was to decrease, if there was to be less and less caterpillars.

Laura says, "I think the robin would survive because there will be other caterpillars for it to eat." What do you think? I'll give you five seconds to think about your answer.

Off you go.

Fantastic.

Well done.

So Laura and Alex are a bit muddled with their understanding of food chains.

Laura says, "The picture in the food chain is of one caterpillar, and the name says caterpillar, not caterpillars!" So the name or picture of each living thing in a food chain does not represent just one example of that plant or animal.

This food chain does not show that one plant is food for one caterpillar, which is food for one robin, which is food for one fox.

Each living thing named in a food chain represents a population of that type.

So a number of them or species of plant or animal within a habitat.

So your population is how many there are of that type or that species.

So true or false, each living thing named in a food chain represents only one individual of that plant or animal.

Is that true or false? I'll give you five seconds to think about your answer.

Off you go.

Fantastic.

Well done.

The answer is false.

Now can you explain why.

Again, I'll give you five seconds to think about your answer.

Off you go.

Fabulous.

Well done.

So the answer is each living thing in a food chain represents a population of that type, species, of plant or animal within a habitat.

Alex says, "I understand now that the robin in this food chain represents not just one robin, rather a population of robins that live in the local environment." Laura says, "If there were no caterpillars, what would happen to the population of robins?" What do you think? I'll give you five seconds to think about your answer.

Off you go.

Fantastic.

Well done.

So all living things in a food chain depend on each other.

A change to one living thing can affect other living things in the same food chain.

So if there were no caterpillars, there would be less food for the robins.

The population of robins would get smaller.

Now, Alex says, "What would happen to the population of foxes if all the robins in this habitat died?" What do you think would happen? I'll give you five seconds to think about your answer.

Off you go.

Fantastic.

Well done.

So if a whole population of plant or animal in a food chain dies, then other animals in the food chain could die too without their food supply.

So it all depends on populations of plants and animals being able to survive in order to keep that food chain going.

And Laura says, "If there were no robins, there would be less food for the foxes, so the population of foxes would get smaller." So the number of foxes would start to decline.

Let's do a quick check-in of your learning.

It says, what will happen if there is a change to the population of one living thing in a food chain? Is that A, the rest of the food chain will be affected? B, the rest of the food chain will not be affected.

Or C, the animals in the food chain will produce their own food.

I'll give you five seconds to think about your answer.

Off you go.

Fantastic.

Well done.

The answer is A, the rest of the food chain will be affected.

Now here is your first task.

It says, look at this food chain.

When gardeners want to stop insects eating their plants, they might spray a poison liquid called an insecticide onto their plants.

When the insects eat the plants, they also eat the insecticide.

What will happen to this food chain if insecticide is sprayed onto the hawthorne plants? So I'd like you to pause the video here and have a go at doing this activity.

Off you go.

Fantastic.

Well done.

So when insects like aphids eat the hawthorn plant, they may become poisoned and die.

If there is a decrease in the population of aphids, this may result in a smaller population of the pipistrelle bats who depend on aphids for food.

So now we are onto the final part of our learning, which is the impact of changes in food chains.

So Alex and Laura continue to talk about food chains, and Alex says, "I can see why it's called a food chain.

Each living thing is a link in the chain and they are all connected together.

And Laura says, "Yes, all living things in a food chain depend on each other.

A change to one plant or animal can affect the others." So Alex says, "If there were no foxes, the number of robins might increase, but the number of caterpillars in the food chain would not be affected." Do you agree with Alex? I'll give you five seconds to think about your answer.

Off you go.

Fantastic.

Well done.

So if there were no foxes to eat the robins, there might be an increase in the populations of robins in this habitat.

But with more robins, there might be a decrease in the population of caterpillars because there's going to be more robins that are going need to eat caterpillars in order to survive.

And this shows how an increase or decrease in the population of a plant or an animal can have a huge effect on the rest of the food chain.

So let's do a quick check-in of your learning before we continue.

So a food chain will only be affected if the population of a plant or animal decreases, so gets less.

Is that true or false? I'll give you five seconds to think about your answer.

Off you go.

Fantastic.

The answer is false.

Now, why do you think this is? Again, I'll give you five seconds to think about your answer.

Off you go.

Fantastic.

Well done.

And it's because the food chain will be affected if the population of a plant or animal increases or decreases.

Now, Alex and Laura are worried about changes in food chains.

And Alex says, "If a population of plants or animals die out, does that mean it's gone forever?" And Laura says, "Well, changes in food chains may lead to animals or plants becoming endangered, or even extinct." So do you know what the words endangered and extinct mean? I'll give you five seconds to think about your answer.

Off you go.

Fantastic.

Well done.

So when a particular type of a plant or animal becomes extinct, this means there are no living ones left anywhere on earth.

So dinosaurs are an example of animals that have become extinct because we don't have dinosaurs roaming the earth anymore.

And scientists suggest that around 66 million years ago an asteroid crashed into earth and caused a huge cloud of dust and ash.

And this blocked out the sun for more than a decade, which affected the growth of plants.

So a decade is 10 years.

As the producers died, which are the plants, the herbivores had less food and their population decreased.

So these are the dinosaurs that relied on plants for food.

And as the herbivore population decreased, their predators were unable to find food and died, eventually becoming extinct.

So on earth today, some animals and plants are endangered, and this means that they are at risk of becoming extinct.

So a living thing is endangered if the population size becomes very small or if it's decreasing.

And scientists suggest that the population of earthworms in the UK has decreased due to the drier weather that we've been having.

And this has affected the population of starlings that depend on earthworms in the food chain.

So if an animal or plant is endangered, humans should do everything they can to protect them.

The British bluebell is a common flowering plant around the UK, however, its population is decreasing, and so it's endangered.

And the British bluebell is now a protected species, which means that it is against the law to uproot them in the wild.

So you can't go and just pick bluebells in the wild.

So who is correct? Alex says, "Changes in food chains can lead to only animals becoming endangered." And Laura says, "Changes in food chains can lead to animals and plants becoming endangered." I'll give you five seconds to think about your answer.

Off you go.

Fantastic.

Well done.

And Laura is correct.

Now let's do another check-in of your learning.

And it says which statement is correct.

A, animals or plants that have died out completely are endangered.

Animals or plants that have died out completely are extinct.

Or animals or plants that have died out completely are eroded.

Again, I'll give you five seconds to think about your answer.

Off you go.

Fantastic.

Well done.

The answer is, B, animals or plants that have died out completely are extinct.

So now we are on to the final part of your learning today, and it says, use the information on the next slide to explain whether you agree or disagree with Izzy.

So Izzy says, "Sea otters are an endangered animal, but this won't affect the kelp or sea urchins in this food chain." So let's go through the information.

So kelp is a type of seaweed that grows naturally in kelp forests in oceans.

Many animals such as sea urchins, small fish and crabs, eat kelp and use the kelp forest as a place to hide from predators.

Sea urchins are small spine animals that live in earth's oceans.

They use their sharp teeth to eat plants such as kelp, and also dead sea animals on the bottom of the ocean.

And sea otters are the smallest marine mammal.

They often entangle themselves in kelp forests to stop themselves from around in the ocean.

Their prey includes sea urchins, crabs, octopus, and fish.

So you're going to use that information on that slide to explain whether you agree or disagree with Izzy.

So let's have a reread of what she said.

She said that, "Sea otters are an endangered animal, but this won't affect the kelp or the sea urchins in this food chain." So I'd like you to pause the video here and have a go at doing this activity.

Remember, you can go back in this video to go and have a look at the information as well.

Off you go.

Fantastic.

Well done.

So I disagree with Izzy because all living things in a food chain depend on each other.

If the number of sea otters continue to decrease, then there will be more sea urchins because less of them are going to be eaten by sea otters.

A bigger population of sea urchins will eat more or all of the kelp, so the population of kelp will decrease.

This will leave less food for other animals, such as small fish and crabs, so their populations might decrease.

And with less kelp, there will be fewer safe places for other animals to hide from large predators.

So they may be eaten too.

So now we are on to the summary of your learning.

The name or picture of each living thing in a food chain does not represent just one example of that plant or animal.

A change to the population of one living thing can affect the population of other living things in the same food chain.

An increase or decrease in the population of a plant or animal can have an effect on the food chain.

Changes in food chains may lead to animals and plants becoming endangered or even extinct.

Well done for today, I am so proud of your fantastic learning.

You have worked really hard and you have thought very carefully, well done.