Lesson video

Hello, my name's Mrs. Harking, and today we're going to be exploring the tropical rainforest biome together.

It is my favourite biome to teach bouts and that's because it's full of life.

It appears in lots of TV and film sets because it's such an interesting place and we're going to find out why it is like that today.

Today's lesson is the tropical rainforest biomes lesson.

It's taken from the forest biomes unit, which asks why are forests so important.

Our outcome today is to describe and explain the location of tropical rainforest and identify their key features.

We've got some keywords that will be useful to know before you start the lesson today.

I'm going to read them through, but if there's any that you would like to take a note of, please pause the video and take some time to do that.

That's absolutely fine.

So our first word today is biome.

A biome is a large region of the world with places that have similar climates, vegetation, and animals.

We have climates.

So climate is an average of the weather conditions in a place taken over a long period of time, so it's normally 30 years or more they work out climate for.

Tropics are the regions north and south of the Equator between the Tropic of Cancer and the Tropic of Capricorn lines of latitude.

And solar radiation is the energy radiated from the sun via electromagnetic waves.

It's the energy from the sun, the heat and light from the sun.

For our lesson outlined today, we're first going to look at the location and climate of tropical rainforests and we are then going to move on to looking at the features of the tropical rainforest.

So let's start with the location and climate of the tropical rainforest first.

Tropical rainforest biomes consist of dense forests.

If you have a look at the image here, we can see that there is green leaves covering the whole photograph.

We've got lots of plants growing on the forest floor here, but also tall trees, which we can just see the trunks of, and also vines growing up in spur the higher canopy so it's full, full of leaves and life these forests.

The reason for that is their climate.

They're hot, humid, and they receive heavy rainfall all year round and we're going to have a look at that in a little more detail.

First of all, I'd like you to select the correct words to describe the climate of the tropical rainforest.

So the tropical rainforest is.

Can you have a look at those words at the bottom? Which one should fit in here? And it receives.

What rainfall? Right, I'll give you a moment to decide which words go into these gaps.

Well done.

So the tropical rainforest is hot and receives heavy rainfall.

Tropical rainforests are located in the equatorial climate zone.

We can see on the map below that the dark orange colour shows the equatorial climate zone, and this is located around the equator, which is the line of latitude around the widest part of our planet.

Temperatures are higher in the equatorial climate zone as the solar radiation has to eat a smaller area.

This is due to the curvature of the earth.

Let's have a look at the diagram below.

This isn't to scale.

The sun would really be a lot bigger and further away.

We can see that the orange lines show solar radiation or the heat from the sun.

At A, the solar radiation is spread over a greater area and this is shown by the yellow circle.

At B, the solar radiation is more concentrated, therefore the equator is hotter.

There is a lot of convectional rain in tropical rainforests as the hot temperatures in the tropics evaporate a lot of water.

This is something that confuses a lot of students because in some countries such as the UK, the type of rainfall we receive tends to fall when it is cooler.

That is not the case across the whole world.

And in tropical regions, there is a lot of convectional rainfall, which is triggered by hot weather.

Let's see how that works now.

So high temperatures cause a lot of liquid water to evaporate into water vapour.

Hot air rises.

Water vapour within the air cools.

And the vapour condenses to form water droplets and cloud, which then rain.

So this is how convectional rainfall works and it's actually triggered by high temperatures.

So the hotter it is, the more likely it is for this to happen.

Between the tropics, it is warm all year round and receives heavy rainfall.

The climate for Kampala in Uganda is shown in the climate graph here.

Can you remember what's the bars and lines show on a climate graph? Well, Lucas remembers that the lines show the temperature and the bars show the rainfall on a climate graph.

So I remember this by the line being like a red line on a thermometer, which obviously measures temperature in the same way that's the line on the climate graph records temperature.

So what we can see here on this climate graph is that we have got temperature on the left hand axis and we have got precipitation in millimetres on the right hand axis.

Precipitation means rain, snow, et cetera.

In this case, in the rainforest it just means rain.

So we have got at the bottom our months of the year.

The months of the year are shown by the first letter of each month.

So we have January shown by a J on the left hand side, then February shown by an F, et cetera.

We can see that this climate graph shows generally that's the climate is very hot and very wet.

So heavy rainfall all year round is shown by our blue bars and we can read that off the precipitation axis on the right hand side.

So there are sun months with higher rainfall than others.

It does fluctuate a bit.

For example, if we go to April shown by the A at the bottom, we can see that that is actually the month where we could have the most rainfall, about 225 millimetres in that month on average.

But we have a lower rainfall in July, which is shown by the third J along the bottom, and that is a lot lower, more like 85 millimetres.

Okay, however, we have got a huge amount of rainfall all year round compared to a lot of other climates around the world.

The temperature shown by the left hand axis and the red line is over 20 degrees all year rounds, which is actually warmer than our summer temperatures in the UK often.

Right, let's have a quick check to make sure that we do understand this graph properly and we can actually use this graph ourselves.

So how much rain does Kampala receive in December? So if we need to read the rain statistics off the graph, we need to have a look at the bars.

If we look at the bars, we need to make sure that we are reading off the correct axis.

So the left hand axis shows temperature, but the right hand axis shows precipitation.

That's where we need to be reading off.

So make sure you do look at the right hand side.

Then we need to think about looking at the month December, remembering that our months are shown by the first letter of each month.

So December is shown by the D at the bottom of the graph.

So if we look at the bar for December, how much precipitation is there? Excellent.

Well done.

I'm going to accept any answers between 140 and 145 because it is quite a vague graph, which is fine.

The exact answer is actually 142 millimetres, but I very much doubt you'll have got that exactly spot on and that's fine.

So we're now going to have a look at the temperature.

The average UK temperature in August is around 17 degrees C.

August is a summer remember in the UK.

Does the tropical rainforest temperature go as low as that? So does the temperature ever drop as low as summer UK temperatures in the tropical rainforest? Let's have a look at the Ugandan rainforest climate graph to help us.

We need to be making sure that we look at the temperature symbol on the graph.

Is that bars or the line? And we need to be thinking about reading off the correct axis.

Is that on the left hand side or the right hand side? Well done.

The temperature does not get as low as it does in the UK.

So even in the summer, the hottest time in the UK, the temperature on average in the rainforest is always higher than the average UK summer temperature.

There'll be some days where things are different, but on average that is the case.

The largest tropical rainforest is the Amazon in South America, but they can be found in five different continents on and either side of the Equator between the tropics.

Can we remember that the tropics and the equator are all lines of latitude? These are imaginary lines that wrap around planet earth.

You can see on the map that the equator is on the widest part of earth in the middle, and then we've got the Tropic of Capricorn and the Tropic of Cancer either side.

The region between these is called the tropics, and we can see that our tropical rainforests are generally found on and around the equator between these tropics.

The five continents that they're found down are North America, Asia, Oceania, Africa, and South America.

Can you check it for me? Tropical rainforests are normally found.

Which is the correct end to this sentence? Is it A, on and either side of the tropics between the poles, B, on and either side of the equator between the tropics, or C, on and either side of the tropics but not on the equator? Well done.

It's B, on and either side of the equator between the tropics.

We are now going to do our first task, so we need to answer these three questions.

Where are tropical rainforests located? What is the climate of the tropical rainforest like? You should include temperature and rainfall in your answer.

If you can give a specific example, that'd be brilliant.

And can you name five continents that tropical rainforests are found in? There's a map on the screen here to help you.

Well done.

Let's take a look at some answers.

Question one, where are tropical rainforests located? It's between the Tropic of Cancer and the Tropic of Capricorn.

You could have also added either side of the equator or in the equatorial zone, all of these would've been good answers.

Describe the climates of the tropical rainforest, include the temperature and rainfall.

So the tropical rainforest is hot.

For example, over 20 degrees C in Uganda and receives heavy rainfall all year.

Name five continents that tropical rainforests are found in.

North America, South America, Africa, Asia, and Oceania.

Well done.

Excellent effort.

Right, let's have a look at our second section to the lesson now.

We are going to cover the features of a tropical rainforest.

Tropical rainforests are important habitats for millions of plants and animals.

The climate of the tropical rainforest impacts on the number of species of plants and animals.

Hot temperatures and heavy rainfall lead to the vegetation thriving as plants need water and sunlight to survive.

This then means that we get a high density of trees and plants and then habitats are formed for millions of species of mammals, reptiles, insects, amphibians, fish and birds.

And that's because there's food and shelter for all of these species.

Let's do a quick check.

Which statement comes after hot temperatures and heavy rainfall in the process that we just discussed? Is it A, vegetation thrives as plants need water and sunlight to survive? Is it B, habitats for millions of species of mammals, reptiles, insects, amphibians, fish, and birds? Or is it C, high density of trees and plants? Well done.

Yes, it's A.

So vegetation thrives as plants need water and sunlight to survive.

Rainforests can be divided into four main layers.

The forest floor, understory, canopy, and the emergent layer.

Which layer is missing on this diagram? Well done.

The canopy layer.

Some trees grow higher and emerge above the rest of the forest.

These form the emergent layer.

You can see it labelled on the diagram here at the top.

The name of this layer makes sense because the trees emerge above the other trees.

It's sticking their heads out at the top.

So the tallest known tree in the Amazon rainforest is 88.

5 metres high, about the same height as 20 double decker buses.

That's really, really high.

It is very impressive that a tree can actually grow to this height without falling and can support itself.

Emergence grow high because they want to reach the sunlight above the forest canopy, allowing them to access more light for photosynthesis.

You can see in the photograph here that this tree in the centre is one that is in the emergent layer.

There are less trees in the emergent layer.

They stick out from the top of the canopy.

How high is the tallest tree in the Amazon rainforest? This is a tricky one.

Can you remember it? Good guess is 88.

5 metres or the height of 20 double decker buses.

I'll accept either.

The dense canopy is the most biodiverse layer of the rainforest.

The majority of leaves, nuts, and fruit grow here.

This provides food for many insects, animals, and birds that call this layer their home.

So we can see in the photograph here a sloth, which is one of the many, many species that live in the canopy layer and they spend the majority if not all of their time in that layer rather than going down to the forest floor.

The layer is about 30 metres high, so they have to be adapted to living at that height.

The canopy layer is also interesting because it's so thick that it can take 10 minutes for rain to trickle through it and fall to the forest floor.

Which layer do most leaves, nuts, and fruits grow in? Well done.

It's the canopy layer.

The canopy above blocks the majority of sunlight making the understory very dark.

We can see in the photograph here that it is quite dark.

This is in the middle of the day, what you'd expect to see in the understory of a rainforest.

The top of the understory is about 20 metres high, to give you an idea of the scale we're talking about here.

The next layer we're going to discuss on our final one is the forest floor.

So the forest floor is home to many decomposers, which break down leaf litter that has fallen from above.

Nutrients are mainly in the top layer of soil as they are taken up by the trees very quickly.

Termites are an example of decomposers.

You can see these creatures here in the photograph.

And these decomposers take any of the leaf litter, the dead leaves that have fallen from the trees and they break them down, turn them into soil, and those nutrients are then taken up by the trees as we've discussed.

A quick check now.

Which layer has the most plants and animal life? Is it the emergent layer, the canopy layer, the understory, or the forest floor? Well done.

It's the canopy.

Right, your task now.

I would like you to complete the flow diagram.

Hot temperatures and what rainfall lead to vegetation thriving as plants need water and what to survive.

This leads to high something of trees and plants and something for millions of species of mammals, reptiles, insects, amphibians, fish, and birds.

What were those missing words? I'm going to pop up some missing words in no particular order to help you to work out which should fill the gaps.

Please feel free to pause the video now to give yourself some time to complete this task.

Well done.

Let's have a look at the answers.

So the flow diagram should look like this.

Hot temperatures and heavy rainfall lead to vegetation thriving as plants need water and sunlight to survive.

High density of trees and plants leads to habitats for millions of species of mammals, reptiles, insects, amphibians, fish, and birds.

Our second part of the task now, we've got question two and three here.

Can you label the layers of the rainforest? And then for each of these layers, could you add a short description? I'll let you pause the video now.

Well done.

Let's take a look at some answers.

So you should have labelled the diagram as you can see on the screen here.

At the bottom, we have forest floor, then understory above and then canopy.

And then right at the top, we've got a few emergent sticking out in the emergent layer.

Let's see what we can add to our description for each.

Say the emergent layer, trees grow higher and emerge above the rest.

Some grow as high as 88.

5 metres.

If you've got that facts in there, brilliant.

It's really good to add some specific evidence to your answers.

The canopy is a dense layer.

The majority of leaves, nuts, and fruits are located here, and it provides food for many insects, animals, and birds that call this layer home.

The understory is very dark as the canopy above blocks the majority of sunlight.

And finally, the forest floor is home to many decomposers, which break down leaf litter that has fallen from above.

Most nutrients are found in the top layer of soil.

If you'd like to pause the video now and add anything you need to your answer, feel free.

Well done.

Let's go through a quick summary of our lesson today.

So we have covered tropical rainforests.

Tropical rainforests are located on and around the Equator between the tropics.

Tropical rainforests are home to millions of species of plants, mammals, reptiles, amphibians, insects, birds, and humans.

And there are four layers to the rainforest, the emergent layer, the canopy, the understory, and the forest floor.

I hope you've enjoyed learning about tropical rainforest today.

I've certainly enjoyed teaching you, and I'll be looking forward to seeing you again next time.