Lesson video

Hello, and welcome.

My name is Mr. Marsh.

I'm here today to teach you all about the interdependence of biotic and abiotic components in the hot desert.

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

So by the end of today's lesson, you'll be able to explain how biotic and abiotic components in the hot desert, such as soil, climate, animals, plants, and people are interdependent.

Now, four key words for you today.

The first of which is biotic, then abiotic, interdependence, and evapotranspiration.

Now, biotic refers to the living elements of an ecosystem, for example, the plants and animals.

Meanwhile, the abiotic refers to the non-living components of an ecosystem, for example, water and nutrients.

Interdependence refers to the connections between different components of the environment where each component depends or influences the others.

And finally, evapotranspiration refers to the transfer of water to the atmosphere through evaporation from surfaces and transpiration from plants.

So we have two learning cycles today, and we shall begin with the interdependence of hot desert components.

Now, hot deserts are global biomes, by which I mean large-scale ecosystems. And in any ecosystem, there are biotic and abiotic components.

Biotic components then referred to the living components of an ecosystem such as the plants, bacteria, fungi, and animals.

Meanwhile, the abiotic components refer to the non-living components such as soil, climate, water, nutrients, and sunlight.

So looking closely now at this image in front of you, we can begin to try and identify the different biotic and abiotic components.

First of all, we can identify the abiotic component, the non-living component of the sunlight.

We can also see the Joshua tree as a biotic component.

Another abiotic component then is the soil.

Remember, this refers to the non-living component.

And finally, then we can also see another type of vegetation, the grasses in the foreground, which, again, is a type of biotic component.

It is living.

So learning check, which of these components are biotic? I'd like you to select the two correct answers and pause your video here whilst you make your answer.

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

So the two correct answers, the two biotic components from the list are B, animals, and D, bacteria.

Our next learning check asks you now to identify the two abiotic components from the list below.

So pause the video here whilst you read through the four options and you select your two correct answers.

Pause the video here.

Okay, let's have a look at the two correct answers, and those were water and nutrients.

And I have a follow-up question, which is why then are plants not considered abiotic? Pause the video here whilst you consider your answer.

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

So plants are not considered abiotic because they are, of course, a biotic, a living component, as Alex says.

Thinking specifically about the hot desert and the key biotic and abiotic components that exist there.

Well, in terms of biotic, we need to know that there are plants, for example, cacti, most famously, animals, most famously, the camel, and the people are all biotic components, whereas the abiotic components may refer to the soil and also the climate there.

Now, biotic and abiotic components are interdependent on one another.

But what does interdependent mean? Interdependence means that they depend on or are affected by each other.

Now, what I'd like you to do right here is pause the video whilst you consider this question.

How might the climate of a hot desert affect plants, animals, soil, and people? So pause the video here whilst you consider your answer.

So how then has the hot desert climate affect the people, animal, plants and soil of the hot desert? Well, first of all, the plants have adapted to deal with those extreme conditions of high temperatures and low rainfall.

Likewise, the people have adapted their agricultural lifestyle and habits to this extreme climate, becoming much more nomadic.

Now the soil will likely dry out and be exposed to wind erosion due to, again, the lack of rainfall and increased evaporation.

Finally, animals such as the camel need to survive those extreme temperatures and low precipitation, and therefore have also adapted physically and behaviorally to those extreme conditions.

Time now for a learning check, I would like you to decide which of the following statements is true.

So read through the three statements, pause the video and decide your answer.

And the correct answer was C, animals need to be able to withstand extreme temperatures and low rainfall.

Really, really well done, if you've got that answer correct.

So the climate may actually be affected by other components.

What I'd like you to do right here is pause the video whilst you consider how you think the climate may be affected by other components such as soil, plants, animals, and people.

So pause the video here whilst you consider your answer.

So let's see how the hot desert climate can be affected by those different components mentioned earlier.

It all comes back to evapotranspiration.

Now, the lack of vegetation in a hot desert will mean less evapotranspiration, which means less moisture rising into the atmosphere, and therefore, less rainfall.

Similarly, global warming caused by human activities, be it regionally or more globally, can cause the climate to become more extreme, much more hot, but also much more dry.

Again, evapotranspiration.

The limited soil reduces the amount of vegetation that can exist in a desert, which means less evapotranspiration, and again, means less rainfall.

And finally, again, if vegetation decreases due to grazing animals, again, linking back to human activities, this will lower evapotranspiration, which, again, will lead to less rainfall.

Understanding the interdependence between biotic and abiotic components in hot deserts then helps us understand the physical processes and how human pressures can affect them.

Looking at the diagram below, we can see then how the abiotic component of climate is really affected by biotic components such as plants, as discussed earlier with evapotranspiration.

And similarly, how biotic components such as plants is dependent on the climate, of course, for its growth.

So humans can have huge damaging effects on the hot desert interdependencies.

For example, overgrazing of livestock can cause vegetation loss.

Again, removing biomass and leading to soil erosion, as well as, of course, a reduction in evapotranspiration, which can therefore lead to a drop in rainfall.

Similarly, with excessive water absorption taken from underground water sources, this can lower the water table and can mean that plants are no longer able to survive in an even drier climate.

So a practise task, I would like you to complete the diagram to show how soil affects and is affected by plants, animals, climate, and people in a hot desert.

So read through the sentence and complete those sentences.

Pause the video here whilst you write your answer, and best of luck.

Now for some feedback.

So climate affects soil because of high temperature and low rainfall can dry out the soil and leave it vulnerable to wind erosion.

Soil affects climate because of a lack of soil, reduces the amount of vegetation that can be supported there, and this can lead to less evapotranspiration.

Less moisturising into the atmosphere causes a drop in rainfall.

Plants can affect the soil because the lack of vegetation in a desert leads to less soil being created.

And finally here, soil affects plants because a lack of soil means that less vegetation can indeed survive.

Animals can also affect the soil because they eat vegetation, which means that soil creation is reduced.

Soil affects animals because the lack of soil reduces vegetation, which limits the number of animals that can actually survive within that ecosystem.

And people affect soil because they often remove vegetation, be it through agriculture or overgrazing of livestock, which, again, leaves the soil very much vulnerable to being eroded.

Soil affects people because they struggle to grow crops when there's a lack of soil.

So really, really well done if you are able to get any of those answers.

We're on now to our second learning cycle, which is regarding the interdependence within physical systems. Now, physical systems are often governed by the interdependence between biotic and abiotic components.

Three examples, what we find in an ecosystem are food chains, where we can clearly see which species is being consumed by another in a linear manner, food webs, a much more complex way of seeing how species are consumed by other species, and finally, the nutrient cycle, where we can see how and where nutrients are being stored and transferred through the system.

A food chain is a physical system that shows how different components are dependent on each other.

And here, we can see where it begins with the producers which produce the energy for the rest of the ecosystem.

These producers then are plants using photosynthesis from the sun to be able to create that energy for the rest of the ecosystem.

Following this then are the primary consumers, those herbivores, the ones which eat the producers, those species of vegetation.

Following this, following this, we may have more carnivores, meat eaters, animals which are secondary consumers, which consume the primary consumers.

Following this, we have the tertiary consumers.

These are really your apex predators, and these consume the secondary consumers.

Finally, we have the decomposers such as bacteria, fungi, and insects.

And these are species which break down dead organic matter.

So we can now begin to identify exactly what these different species are interdependent on, beginning with the producers, the plants, a biotic component.

These are dependent on abiotic components such as the sun, water, and the nutrients found in the soil.

Next, along with the primary consumers, of course, a biotic component being that they are animals, typically herbivores, and these depend on plants being another biotic component, but also abiotic components such as soil and water.

Next, along with the secondary consumers, carnivores, these are animals, again, biotic, which are dependent on other biotic components to consume, but also other abiotic components such as, again, soil and water.

Next along, we have our tertiary consumers, those apex predators, again, a biotic component, and they are dependent once again on those secondary consumers, which are a biotic component.

Once again, they're also dependent on abiotic factors such as the soil and water.

Finally, we have the decomposers, and they depend on a supply of dead organic matter, dead producers, and dead consumers.

Time now for a learning check.

I would like you to add those three terms that you can see in front of you on the screen into the correct place in the food chain, A, B, and C.

So pause the video here whilst you decide your answer.

Best of luck.

And the correct answers were producers are at the beginning of the food chain next along with the primary consumers, meaning next is the secondary consumers, next along with the tertiary consumers.

And finally, we have the decomposers.

Really, really well done if you've got those answers correct.

So plants and animals, both biotic components form complex food webs of interdependence in hot deserts.

And studying this food web further, we can begin to break it down, starting with the vegetation.

We can see the producers at the base of the food web.

These are the species which are producing the energy via photosynthesis, looking at that abiotic component of the sun in order to drive and create the energy for the rest of the ecosystem, the rest of the food web.

Now some examples as you can see are the cacti, desert grass, and shrubs.

Everything above then are the animals, be it the primary, secondary, or tertiary consumer that we can see in front of you.

The primary consumers that we can see right there are a species such as insects and rodents, being that they are the ones which consume those producers.

Secondary consumers we may identify as being a species such as the small bird or the lizard, but certainly, our tertiary consumer are our apex predators, which in the example of this hot desert food web are coyotes and hawks at the top of that food web.

So although not actually shown in this food web, these plants and animals all depend on abiotic components, such as the climate, the soil, and the water.

So learning check, true or false, a food web shows the interaction between biotic and abiotic components in an ecosystem.

So pause the video here whilst you decide your answer.

Now the correct answer is, of course, false.

But again, I would like you now to consider why it is false.

So once again, pause your video whilst you think and consider your answer.

And the reason why it is false is that a food web shows interdependencies between biotic components alone, biotic components only, but does not include abiotic components.

However, all the plants and animals do rely on abiotic components such as the climate or the soil or the water.

But the food web just doesn't show this.

It only shows those biotic components, by which I mean the plants and the animals.

So really, really well done if you are able to get those answers correct.

So let's turn our attention now towards the nutrient cycle.

And this diagram shows the nutrient cycle, and it shows the interdependence between biotic and abiotic components.

Now as you can see on the diagram, there are three different stores of nutrients.

These are found in the soil store shown with a circle with the S, in the biomass store shown with a circle and a B, and these are all the plants and animals combined.

And finally, we have the litter store.

These are the dead plant and animal matter.

Now, in a hot desert ecosystem, it goes without saying that the amount of nutrients in the system is very low due to the extreme climactic conditions we find that.

So once again, the soil store is an abiotic component, the nutrients found there are within a non-living component.

The biomass store though is a biotic component because it includes all the living plants and animals.

And finally, the litter store, referring to the dead organic matter, is an abiotic component.

So a learning check.

True or false? Litter in the nutrient cycle is considered biotic.

Pause the video here whilst you decide on your answer.

And the correct answer is, of course, false.

Again, I would like you to consider why it is false.

So pause the video here whilst you consider your answer.

Now, the reason it is false is because litter consists of non-living organic matter such as dead leaves, decomposing matter, and although it originated from living organisms, once it becomes litter, it is classified as non-living.

So really, really well done if you were able to get those answers correct.

Now, this is the nutrient cycle for a hot desert, and we need to try and break it down a little bit more.

Now, as we already know, precipitation in the hot desert is very, very low, under 250 millimetres, and this then is represented by the thin arrow as an input.

The lack of water then means that few plants can survive there, and as a result, the biomass store is very small as represented by a smaller circle.

Now, due to the arid conditions, there is little biomass, meaning the little store is also very small.

The less biomass there, logically, the less litter, the less dead organic matter that is also found in the system.

The soil store in hot deserts is bigger than the biomass or litter stores because there isn't much water to actually leach or wash out those nutrients from the soil.

There aren't many plants to absorb and take those nutrients out the soil.

And decomposition takes a long time due to the lack of rainfall in a hot desert.

Now, decomposers depend on that water.

So the arid condition makes rates of decomposition extremely slow.

Therefore, litter takes a long, long time to decompose.

However, deserts do still have low nutrient soils because there are little biomass to actually add nutrients to them.

So yes, whilst it's true that the soil store is the largest store of nutrients in hot deserts, I don't want you to think that that means it has high nutrient soil.

This just is not the case.

So littering, dead material falling into the litter store from the biomass, has a large thick arrow in desert ecosystems, because this is the most important process for nutrient cycling.

And the runoff has an extremely small thin arrow because of the lack of precipitation that you get in hot deserts, meaning that there is very little leaching, very little washing out of nutrients from the soil.

It is true though that hot deserts do sometimes experience flash floods, which can wash nutrients out of the soil.

So a learning check, a lack of water means what for the nutrient cycle in a hot desert? I'd like you to read through the three correct options and decide on the answer.

So pause the video here whilst you decide your answer.

Best of luck.

And the correct answer was C.

A lack of water means a small biomass store due to the dry conditions and lack of nutrients.

Now, each individual plant or animal in hot deserts can be seen as a part of a nutrient cycle and part of the wider food web or food chain.

Now looking at the famous example of a cactus in a hot desert, it relies on the soil for its nutrients, but also stabilises the soil through its roots.

This add nutrients to the soil when plant matter falls to the floor and decomposes, and also, it provides food for animals as part of a complex food web.

So on now to our final practise tasks.

The fennec fox is an omnivorous animal that lives in the hot deserts of North Africa, meaning that it eats both plants and animals.

What I'd like you to do is suggest how it is part of a food web and a nutrient cycle.

For the second practise task, I would like you to select the correct option to complete the paragraphs below.

And the third and final practise task, I would like you to use the diagram to explain the size of the biomass, litter, and soil stores in hot deserts.

Try to use words from the diagram.

So pause the video here whilst you write those answers for those three practise tasks.

Best of luck.

So some feedback.

How is the fennec fox part of a food web? Well, it will eat both plants and small animals, but will also be preyed upon by larger animals.

How does it fit in a nutrient cycle? Well, it'll be a part, of course, of the biomass store, being a living species.

But when it dies, it will become part of the litter store before decomposing to add to the soil store.

In terms of the correct options within this paragraph, this is what it needed to read, as soils in the hot desert contain very low amounts of organic matter.

This is due to the biomass being so small.

Decomposition is also slow, which means nutrients take a long time to be released.

The soil store of nutrients in hot deserts is larger than the biomass and litter stores.

This is because of the lack of water to leach nutrients outta the soil, as well as the lack of vegetation uptaking the nutrients from the soil.

And finally, you were asked to use the diagram to explain the size of the biomass, litter, and soil stores in hot deserts.

Now, your answer may have included something like this.

The fact that the biomass is low, as the lack of rainfall means plant growth is severely limited.

The litter store then is small as the limited vegetation means that there will not be that much dead organic matter.

The soil store is bigger than the other stores as there is not much rainfall to leach or to wash those nutrients outta the soil.

And actually, there's just not that many plants to absorb or take those nutrients out of the soil.

So really, really well done if you are able to get any of those correct answers.

To summarise then, hot desert ecosystems exhibit interdependence of climate, water, soils, plants, animals, and people.

Food chains and food webs show how biotic and abiotic components are interdependent on one another in a hot desert.

And finally, nutrient cycles show how biotic and abiotic components are interdependent in a hot desert.

So really well done in today's lesson.

It was a pleasure teaching you, and I will see you again soon.