Lesson video

Hello and welcome.

My name is Mr. March and I'm so excited to be learning with you today.

Today we're going to be learning about plant and animal adaptations, as well as issues affecting biodiversity.

So grab everything that you need for this lesson and let's get going.

Now, by the end of today's lesson, you will understand that plants and animals are well adapted to the physical conditions in hot deserts and that there are issues related to biodiversity.

The keywords for today's lesson are adaptation, nocturnal, biodiversity, and ecosystem.

Now, adaptation refers to evolutionary changes that improve an organism's chance of survival in its environment.

Nocturnal refers to species that are active at night and resting during the day.

Biodiversity refers to the variety of different types of life found in a particular area.

And finally, ecosystem refers to a community of living organisms and their interactions with their environment.

Now, we have three learning cycles for today's lesson, and of course we will start with learning cycle one, where we identify and look at how have animals adapted to hot desert condition? Now, hot deserts are extreme environments that most plants and animals cannot survive in due to the lack of precipitation and of course the extreme heat that we find there.

The animals and plants that we do find in hot deserts are highly specialised and highly adapted to those extreme conditions.

Those biotic components live in hot deserts due to those adaptations.

Now, an adaptation is an evolutionary change that improves an organism's chance of survival in its environment.

And animals in the hot desert have adapted in many ways.

For example, some animals have adapted thermoregulation.

These are adaptations, such as large ears, for example, the fennec fox, which allows animals to release body heat to deal with those extreme temperatures.

We also have species which are very water efficient, for example, famously a camel.

Camels can tolerate high rates of dehydration and can take on large volumes of water.

This is, of course, extremely important in the hot desert where water sources are at an extreme minimum.

Finally, there are species which are heat avoidant, be it through nocturnal behaviour, by which I mean being active at night and resting during the day.

Also, some animals' behaviour has them burrowing deep underground where it is cooler just to avoid that daytime heat.

Therefore, we can see that through these adaptations, animals in the hot deserts have become specialised at avoiding and dealing with those extreme temperatures and that extreme lack of precipitation.

So, here's my first learning check for you.

Which three of the following are adaptations of hot desert animals to thermoregulate or avoid heat? Pause the video here whilst you consider and make your answer.

Okay, so let's have a look at the three correct answers.

The three correct answers were nocturnal behaviour, thereby being active at night and resting during the day, having larger ears to release heat, and finally, burrowing underground, yet another adaptive behavioural change which sees animals escape heat during the daytime.

Okay, so let us begin by looking at an animal which is synonymous with the hot desert.

That being of course the camel.

Let us see how a camel has adapted to its hot desert environment.

The first place we should start is with its famous hump.

Now, a lot of people wrongly assume that the camel's hump stores water.

As I said, this is incorrect.

It actually stores fat, which can act as an energy reserve.

Next, we need to know that also camels have adapted thick leathery lips to allow them to eat spiny cacti.

This is, of course, extremely important in hot desert environments where vegetation can be very minimal.

So being able to eat spiny cacti can potentially be a real life saver, a real game changer.

Next, they have long eyelashes and hairy ears, and this is to protect them from the strong winds that sometimes you can find in hot deserts and that sand and dust, which can be blown through the air.

Next, they have very wide feet in order to spread their weight across the sand and not sink in, therefore reducing the amount of energy that they need to expend to walk effortlessly through the sand.

Camels can actually tolerate extreme temperatures, of course, very useful for the hot desert, and they can tolerate temperatures of up to 42 degrees.

And finally, they're able to conserve water by producing highly concentrated urine.

Again, obviously very, very important in the hot desert where water is at real minimum.

So, here is my next learning check.

Which one of these is a way in which camels conserve water? Is it A, by drinking constantly? Is it B, by producing concentrated urine, or is it C, by storing water in their humps? Pause the video now whilst you consider and make your answer.

Okay, how did you get on? Let's have a look at the correct answer.

The correct answer is of course that camels conserve water by producing concentrated urine.

Well done.

Okay, so here is my first practise task for you to attempt.

And what you need to do is you need to match the sentence beginning to the correct sentence end.

On the left you can see the sentence beginnings and on the right you can see the sentence endings.

For example, on the left you can see that the sentence beginnings are high daytime temperatures can be avoided by, animals that burrow during the day can avoid, an adaptation is a change in structure or function that, the fed fox uses its large ears to, and finally, camels store fat in their humps, which.

And then moving to the right hand column, we can see the sentence endings.

And these are becoming nocturnal, help release heat and stay cool, the intense heat of the day, improves an organism's chance of survival in its environment, and finally, helps them survive long periods without food.

Okay, so pause the video here whilst you attempt this answer.

Good luck.

And now on to our second practise task.

And this time I'm asking you to specifically look at the camel.

The question is to explain two adaptations that enable camels to survive in the hot desert.

And the question is really asking you to identify two adaptations and then explain how each adaptation helps the camel to survive in the hot desert.

Pause the video here whilst you make your answer.

Best of luck.

Okay, let's now look at the correct answers, starting with practise task one, and these are the correct sentences written out in full.

For example, the first one reads high daytime temperatures can be avoided by becoming nocturnal, animals that burrow during the day can avoid the intense heat of the day, an adaptation is a change in structure or function that improves an organism's chance of survival in its environment.

The fennec fox uses its large ears to help release body heat and stay cool.

And finally, camels store fat in the humps, which helps 'em survive long periods without food.

And finally, our second practise task for this first learning cycle asks you to explain two adaptations that enable the camel to survive in the hot desert.

And these are some of the answers you may have included.

Remember, we were just looking for two.

The first of which says highly concentrated urine conserves water.

This means that camels can survive the arid conditions of hot deserts for longer without drinking.

Leathery lips make it possible for camels to eat cacti and other spiky desert vegetation, which is often all there is to eat in the desert.

Hump to store fat means that camels can go for long periods without food, important in hot deserts where vegetation is very sparse.

And finally, wide feet to spread their weight in the sand.

This helps camels to move efficiently in sandy deserts, reducing energy loss.

Now, there were other answers available, but if you included any of those that I've just read out, really well done.

Okay, we're moving on to our second learning cycle now.

We're looking at how have plants adapt to hot desert conditions? Now, plans with adaptations which allow them to live in arid conditions are known as xerophytes.

Xerophytes have adapted to make efficient use of the little water that is actually available in hot deserts.

And we have three examples right here at the bottom of the screen.

We have the agave, we have famously the cacti, and then we've also got the Joshua tree, which we have looked at in a previous lesson.

Rainfall in hot deserts really happens rarely with the water, of course, evaporating extremely quickly due to the extreme heat there.

And as you already know, rainfall in hot deserts is less than 250 millimetres per year.

Therefore, vegetation in hot deserts needs to be able to use whatever rainfall they get in a very, very efficient way.

So, ephemeral plants have adapted to those conditions.

These are plants which grow flower and produce seeds within just a few weeks of rainfall.

Their seeds have very tough outer coatings which allow them to survive through long dry periods until the next rainfall when they germinate.

So they really take advantage of what little rainfall they receive in order to have this life cycle.

The Arizona desert poppy is an ephemeral which grows flowers and produces seeds all within about five weeks of rainfall, thereby really harnessing the limited rainfall that it receives in a hot desert.

So, my first learning check is true or false? Xerophytes are plans which grow quickly after rain and die when the water dries up.

Is it true? Is it false? Pause the video here whilst you consider and make your answer.

Okay, let's have a look at the correct answer together.

And the correct answer was of course, false.

And once again, I'm gonna be asking you as to why this is false.

So, once again, pause the video here whilst you consider your answer.

So, let's have a look at the reason why it was false.

Well, xerophytes are plants that have adapted to use and store the little water they receive, whereas ephemeral plants are those which grow extremely quickly after a rainfall event and die once the water dries up.

This is the difference between a xerophyte and an ephemeral plant.

Well done if you've got that correct.

Really well done.

Okay, so let's have a look now at xerophytes and its range of adaptations.

We are going to look specifically at the cacti here in front.

Now, cacti have adapted spines rather than leaves.

Why? Because spines have a smaller surface area.

This reduces the amount of transpiration and evaporation, thereby reducing the amount of water lost.

Spines also protect plants from grazing animals.

Succulents like cacti also store water in their fleshy stems, leaves, and roots, which it can call upon when it needs rather than waiting for additional rainfall.

It also has thick, waxy skin, which again reduces water loss.

And cacti and other phys have extremely wide but shallow roots to capture as much rainfall before it evaporates.

And also it secures the plant against extremely strong winds, which we find in hot deserts.

Finally, other desert plants have long tap roots, which can go seven to 10 metres deep into the ground.

This then is able to tap into those water supplies deep underground, thereby allowing their survival.

Again, here's my learning check.

Which two of the following are ways in which plants have adapted to the hot desert conditions? Is it a, tap roots reaching deep underground? Is it b, shallow roots spreading over a wide area? Is it c, broad leaves to maximise evapotranspiration, or is it d, green pigment to increase photosynthesis? So pause the video here whilst you consider and make your answer.

Okay, so let's have a look at the two correct answers.

And those were tap roots to reach deep underground.

Yes, as I said previously, some plants in the hot desert have tap roots which can reach seven to 10 metres underground to find water sources.

And the other answer was, of course, b, shallow roots spreading over a wide area.

Good job if you've got those two correct.

And here is my next learning check.

So why is it that desert plans have a waxy skin? Is it a, to attract pollinators? Is it b, to increase photosynthesis, or is it c, to reduce water loss? Again, pause the video here whilst you consider and make your answer.

Okay, let's have a look at the correct answer, which was to reduce water loss.

Desert plants, such as cacti, has waxy skin in order to reduce that water loss.

Okay, we are onto our first practise task for the second learning cycle.

It is asking you to look at the adaptations which are labelled on that diagram of a cacti.

Now, for each of the adaptations labelled on the cactus, explain how it helps the cactus to survive in the hot desert.

And one label has already been explained as an example for you below.

So, for example, we can see the large, fleshy stem.

Now, your job is to explain how and why that large fleshy stem allows it to survive in the hot desert.

And as we can see on the screen, we have the explanation there.

A large, fleshy stem is used to store water.

This adaptation helps the plant survive for long periods without rain.

Now, you can see that you've got three additional labels on that diagram.

What I'd like you to do is pause the video at this point and try to explain how each of those adaptations allows it to survive in the hot desert.

Best of luck.

Pause the video here.

Okay, and now onto our second practise task.

I would like you to compare and contrast the adaptations of xerophytes and ephemerals in hot desert environments.

On the left, we can see we have our xerophyte, the agave plant, and on the right you can see we've got our Arizona desert poppy, that ephemeral that we looked at earlier.

I would like you again to pause the video at this point and compare and contrast the different adaptations that both xerophyte and an ephemeral has in the hot desert.

Best of luck.

Okay, so let's have a look now at some answers, starting of course with practise task one.

You were asked for each of the adaptations labelled on that diagram of the cactus, explain how it helps the cactus to survive in the hot desert.

Now, your answer may have included some of the following, spines on a cactus are to protect the cactus from being eaten by animals, but also spines have a smaller surface area than leaves, which reduces water loss from evaporation and transpiration.

Secondly, we have those shallow, widely spreading roots, and there are two functions of this, the first of which secures the plant into the soil against those strong desert winds, but also it maximises absorption of any rainfall which falls in the hot desert since those wide roots really maximises the absorption of that water before it evaporates from the hot temperatures in the hot desert.

Finally, there's the thick, waxy skin, which reduces moisture loss from plant tissues.

Well done if you got any of those.

Now, the second practise task was a real difficult question.

It was asking you to compare and contrast the adaptations of xerophytes and ephemerals in hot desert environments.

Now, your answer may have included some of the following.

Xerophytes like the agave plant are adapted to cope with the aridity of hot deserts while ephemerals, like the Arizona desert poppy, are adapted to only grow when rain has actually fallen in the desert.

So, to do this, xerophytes have adaptations that greatly reduce the amount of water that is lost and may also be able to store water in their tissues, whereas ephemerals have extremely rapid life cycles.

So they flower and seed within a period of just a few weeks, making the most of the available water for the short period of time before it all dries up.

That was a really difficult question, so really well done to you if you were able to get any of that correct answer right there.

Okay, our third and final learning cycle is what threatens the biodiversity of hot deserts? So biodiversity is naturally low in hot deserts because of the extreme climate we find there, the extreme high temperature, but also the lack of precipitation, less than 250 millimetres per year, remember.

There are high temperatures during the day and extremely cold temperatures at night.

There are also strong desert winds as well, and there are also very poor, low nutrient soil quality, as discussed in a previous lesson.

Only plants and animals that are really specially adapted to these extreme conditions will survive.

Now, let's look further at some of the other issues which is causing biodiversity to be extremely low in the hot desert.

So the adaptations of plants and animals cannot cope with changes in their ecosystem.

The plants and animals that we find in hot deserts are very vulnerable, and this is what makes the hot desert ecosystem and biome extremely fragile.

Now, as a fragile ecosystem, biodiversity is vulnerable to any changes that can be caused by human activities.

So, my first learning check is this question right here, which asks you, which of the following help explain low biodiversity in hot deserts? Answer all those which apply to answering that question.

So pause the video here and best of luck.

Okay, how did you get on? Let's have a look at the correct answers.

And there were two correct answers.

The correct answers were arid conditions, less than 250 millimetres of rainfall per year, and second of all, the low level of nutrients found in hot desert soil.

These are two reasons which explain the low biodiversity in hot deserts.

So, what is actually threatening the biodiversity of hot deserts? Well, this all comes back to, unfortunately, human activities, the first which is urbanisation, by which I mean the development of urban areas, such as cities and infrastructure, such as roads and communication.

These can all fragment and break up ecosystem, which then disturbs habitats and can actually lead to wildlife lots.

Second of all is a real growth in the tourism industry in hot desert environments.

These tourists can disturb habitats, cause pollution, and an over extraction of water.

With more people coming into hot desert environments, that really puts a stress on the limited amount of water present in those areas.

And this of course puts pressure on water resources for plants and animals as well.

Thirdly, we have overgrazing.

With a growth of human population in hot desert environments, this can lead to overgrazing, which is where livestock grazing really damages plants and reduces soil cover.

And this then can lead to increased soil erosion and a degradation of the soil, which naturally is already suffering from a low quality or a low abundance of nutrients.

And this overgrazing really exacerbates and makes the problem worse.

Finally is climate change.

So we already know hot desert environments are already extremely hot and lacking precipitation.

Climate change is really driving that and making the situation much, much worse.

So rising global temperatures are causing hot deserts to get even hotter and even drier, more arid, and this is causing then longer droughts.

A drought is a period with no rainfall, and therefore if the period is even longer, this puts even more stress and pressure on the biodiversity that we find in hot deserts, and unfortunately reducing it as well.

So, a learning check here, true or false, climate change has no effect on biodiversity in hot deserts? Pause your video here whilst you consider and make your answer.

Okay, let's have a look at the correct answer.

Really, really well done if you came up with the correct answer as being false.

Now, once again, I would like you to pause the video and consider why it is that it is false that climate change has no effect on biodiversity.

So pause the video here whilst you consider your answer.

Okay, let's have a look at the reason why it is false.

Well, the reason why it is false that the changing climate caused by global warming is leading to hot deserts becoming even warmer, even drier, with even longer droughts.

And this is leading to, yeah, less water available for plants and animals in that environment, which is causing a decrease in the biodiversity of hot desert ecosystems. Really, really well done if you were able to get those two answers correct.

Okay, we're onto our final practise task, and this time I'm asking you to categorise the causes of low biodiversity in hot deserts into physical, by which I mean natural, or human.

So looking at these causes, we need to categorise 'em into physical or human.

The first of which says an extreme climate, very high daytime temperatures, very cold nighttime temperatures.

The second talks about tourism.

Then we have poor soil quality due to limited nutrients, limited rainfall, less than 250 millimetres per year, climate change causing an even drier climate, overgrazing of livestock animals, and finally, strong desert winds.

Your task is now to pause the video and categorise those causes into physical, by which I mean natural, and human.

Best of luck.

Pause the video here.

Okay, and our second practise task is for you to explain two physical, by which I mean natural, reasons for low biodiversity in hot deserts.

In your answer, I'd like you to state the physical reason for low biodiversity and then develop your answer by explaining how this factor limits biodiversity.

Once again, really good luck with this question.

Pause the video here whilst you write your answer.

Okay, how did you do? These are the answers for practise task one.

We can see that an extreme climate with very high daytime temperatures and low nighttime temperatures, this is a physical reason.

Tourism is a human cause of low biodiversity.

Poor soil quality due to the lack of nutrients is a natural, it is a physical cause.

Limited rainfall with less than 250 millimetres per year is also a physical cause.

Then we have climate change, which is causing an even drier climate.

This is a human cause.

Overgrazing of livestock animals, so farm animals is a human cause of low biodiversity.

And then finally, those strong desert winds, this is a physical, this is a natural cause.

So really well done if you were able to correctly categorise those.

And then finally, the answer to question two, to explain two physical reasons for low biodiversity in hot deserts.

Your answer could include any two of the following, starting with that extreme lack of rainfall, which really means that few plants, and therefore animals are actually able to survive those hot desert environment, meaning of course that the biodiversity is low.

Hot desert, animals and plants are also challenged in other ways, such as the very high daytime temperatures, but also the very low nighttime temperatures as well.

And realistically, very few species have evolved the adaptations to be able to cope with those both extremes, which again leads to low biodiversity.

Finally, we have those hot desert soils really lacking in nutrients, which unfortunately just naturally means that there's not enough nutrients in order to be able to sustain enough life there, meaning that that there's just a low biodiversity as a result.

This obviously has a knock on effect to the amount of consumers that the ecosystem can support due to the lack of producers in the beginning.

So, again, that was a really difficult question.

Really well done if you had any of those answers that I've just read through.

Okay, finally, our summary.

So, key points from today's lesson.

An adaptation is an evolutionary change that improves an organism's chance of survival in its environment.

Some animals and plants have evolved adaptations that allow them to live in the extreme environments of hot deserts.

Now, although a range of animals and plants have adapted to live in the hot desert, the extreme conditions means that biodiversity is low compared to most other large scale ecosystems. Human activities though, such as climate change, are unfortunately putting increased pressure on hot deserts, which is leading to further biodiversity loss.

So, thank you very much for being with me today on today's lesson.

I hope you enjoyed it and I'll see you soon.

Thank you.