Lesson video

Hello and welcome.

My name is Ms. Harrison.

I'm so excited to be learning with you today.

Today's lesson is called "Nutrient cycling and biodiversity in the tropical rainforest." Grab everything you might need for today's lesson and let's begin our learning.

By the end of today's lesson, you'll be able to understand that tropical rainforests have a high rate of nutrient cycling and support high levels of biodiversity and complex food webs.

Before we can begin this learning, we need to define the keywords that we'll be using throughout today's lesson.

The keywords are biodiversity, nutrients, and interdependent.

Biodiversity.

This is a measure of how many different species live in an ecosystem.

Nutrients.

These are the chemical substances found in all biotic features which are important for survival.

Interdependent.

This is when two or more biotic features like plants or animals depend or rely on each other to survive.

Now that we've defined these keywords, we can begin our learning.

The first question we're going to explore is, what is biodiversity? Biodiversity refers to the variety and number of different species that live in an ecosystem, and tropical rainforests are some of the most biodiverse places on Earth.

Despite covering only 6% of Earth's land surface, tropical rainforests are home to an astonishing 50% of the world's species of plants and animals.

This incredible concentration of species make rainforests essential for maintaining global biodiversity.

The plants, animals, insects, and other organisms in these ecosystems interact in complex ways, supporting the balance and health of the environment.

For example, rainforests play a crucial role in pollination, seed dispersal and maintaining genetic diversity, all of which are key to the survival of species across the planet.

The tropical rainforest has a high biodiversity for several reasons.

The climate.

It has warm temperatures all year and high rainfall, which means plants grow continuously.

Nutrients.

The climate conditions create abundant plant growth and all these plants create lots of food for lots of animals.

Time.

Rainforests are ancient.

The Amazon rainforest is at least 33 million years old.

Lots of different species have evolved.

Habitats.

The different layers of the rainforest have different conditions and different species have evolved to live in them.

In the tropical rainforest, plants and animals are closely connected.

Many species rely on each other to survive.

This is called interdependence.

For example, some plants need animals to spread their seeds, helping new plants grow in different areas.

In some cases, this relationship is even more specific.

Imagine an animal that can only eat one type of plant.

If that plant disappears, the animal could struggle to survive.

These connections make the rainforest a delicate and balanced ecosystem where every species plays an important role.

Alex has cleverly said, "I guess this means if one plant species dies out, it might mean that an animal may not have any food to eat." What does interdependent mean in terms of tropical rainforest ecosystems? Is it A, all species in the rainforest compete for the same nutrients; B, different organisms rely on each other to survive; or C, tropical rainforests are independent of other biomes? Pause the video here whilst you decide and press play when you're ready to continue.

Fantastic, the answer is B, different organisms rely on each other to survive.

Well done if you identified that correctly.

True or false? The tropical rainforest is home to only 10% of the world's species, making it one of the least biodiverse ecosystems on Earth.

Pause the video here whilst you decide if this statement is true or false and press play to continue.

Fantastic, this statement is false.

I would now like you to explain why.

Pause the video here and press play to continue.

Fantastic, the reason why this statement is false is because the tropical rainforest is home to about 50% of the world's species, making it one of the most biodiverse ecosystems on Earth.

Well done if you managed to explain that correctly.

I would now like you to explain the high biodiversity of the tropical rainforest.

Andeep has said he's going to start his answer with the definition of biodiversity.

Pause the video here whilst you attempt this task and press play when you're ready to continue.

Fantastic, let's check our answers.

Your answer may have included some or all of the following points.

Biodiversity in the tropical rainforest refers to the wide variety of plant and animal species found in the ecosystem.

The tropical rainforest is home to around 50% of the world's species, making it one of the most biodiverse places on Earth.

The tropical rainforest has a high biodiversity for several reasons.

Warm temperatures all year and a heavy rainfall means plants can grow continuously, and its abundant plant growth creates lots of food for lots of animals.

Another factor is that rainforests are ancient.

The Amazon rainforest is at least 33 million years old, which means there's been time for thousands of different species to have evolved.

The rainforest also contains many different habitats, and this encourages high biodiversity too.

For example, the different layers of the rainforest have different conditions, and so different species of plants and animals have evolved to be specially adapted to those habitats.

Well done if you managed to explain that correctly.

We're now going to explore the second question of today's lesson, what is the nutrient cycle? The nutrient cycle is a vital process in ecosystems where essential nutrients like nitrogen, phosphorus, and carbon are recycled and reused by plants and animals and microorganisms. In tropical rainforests, this cycle is particularly important due to the unique conditions of the environment.

The rainforest's warm, humid climate creates ideal conditions for rapid nutrient breakdown.

When plants and animals die, their remains decompose quickly, releasing nutrients into the soil.

These nutrients are then absorbed rapidly by plants, helping to support the diverse and lush vegetation of the rainforest.

This vast nutrient turnover supports the high biodiversity of rainforests as plants and trees grow quickly and sustain the complex food webs that depend on them.

The cycle also helps to maintain soil fertility, making it easier for new plants to take root and grow.

Let's break this down a bit more.

Nutrients enter the ecosystem through weathering and from the atmosphere.

Plants take up nutrients from the soil and use them to grow.

Animals obtain nutrients by eating plants or other animals that have eaten plants.

And when plants and animals die, decomposers break down their tissues, releasing nutrients.

This is then recycled back into the cycle and the process continues.

In the tropical rainforest, the largest store of nutrients is the biomass store, which refers to all living organisms in the ecosystem, plants, animals, and microorganisms. These organisms play a crucial role in the rainforest nutrient cycle with nutrients being constantly exchanged between them.

Nutrients are introduced into the biomass store when animals eat plants or when predators consume prey.

Through this process, nutrients like nitrogen and phosphorus and carbon are transferred through the food chain, supporting the growth and survival of organisms at each level.

However, nutrients are lost from the biomass store when plants or animals die.

As decomposition occurs, the nutrients from the dead organisms are broken down by microorganisms and returned to the soil where they can be taken up by plants and continuing the cycle.

The rapids recycling of nutrients in the biomass store is what allows rainforest to sustain such high levels of biodiversity.

This process also ensures the ecosystem remains fertile, supporting new plants and animal life.

The litter store in the tropical rainforest refers to all the dead organic material in the ecosystem such as fallen leaves, dead plants, and animals that have died.

This store is much smaller than the biomass store as it contains organic matter that has not yet been broken down or decomposed.

When leaves and plants fall into the forest floor, they begin to decompose and release nutrients into the soil.

This process is carried out by range of decomposers such as fungi, bacteria, and insects, which break down the organic material into simpler nutrients that can be reabsorbed by the plants.

However, because the litter store is primarily made up of dead organic matter, it contains less stored energy compared to the biomass.

It plays a crucial role in returning nutrients to the soil which supports the rainforest's high productivity.

As a result, the rainforest remains lush and biodiverse.

The litter store is small because nutrients do not stay here long enough to build up.

Warm, wet conditions are perfect for decomposition, so this process happens quickly.

Decomposition releases nutrients from dead organic material and these enter the soil store.

The heavy rainfall washes nutrients out of the litter as runoff.

What is the largest store in the tropical rainforest nutrient cycle? Is it A, soil; B, biomass; C, litter? Pause the video here whilst you decide and press play when you're ready to continue.

Fantastic, the largest store in the tropical rainforest nutrient cycle is B, biomass.

What role does litter play in the nutrient cycle of the tropical rainforest? Is it A, because the rainforest has no seasons, trees do not lose their leaves and so there is very little litter; B, litter accumulates on the forest floor, storing nutrients for long periods because it is too damp for decomposition; C, litter decomposes rapidly in the humid conditions, releasing nutrients back into the soil for plant uptake; D, litter does not play a significant role in the nutrient cycle of the tropical rainforest.

Pause the video here whilst you decide and press play when you're ready to continue.

Excellent, the answer is C.

Litter decomposes rapidly in the humid conditions, releasing nutrients back into the soil for plant uptake.

Well done if you identified that correctly.

The soil store in tropical rainforest is often considered the least nutrient-rich store compared to others, like the biomass or litter stores.

This is because tropical rainforest soils do not hold nutrients for long periods.

While they do gain nutrients from decomposers which break down organic material, and from the weathering of rocks and nutrients which are quickly leached away due to heavy rainfall that is typical in these ecosystems. Tropical rainforest soil is often red in colour because it contains high levels of iron and aluminium.

These elements are a result of the high temperatures and constant weathering of rocks in the region.

While the soil may be rich in these minerals, it often lacks nutrients like nitrogen and phosphorus and potassium, which plants require for growth.

As a result, rainforest plants tend to rely on the rapid recycling of nutrients from the litter and biomass stores to meet their needs.

Because nutrients are not retained in the soil for long, they're continually replenished through decomposition and the rapid recycling of nutrients from dead organic material.

However, when tropical rainforests are disturbed or cleared, the soil loses its ability to support plant life due to the loss of nutrients and the disruption of the natural cycles.

Soil in tropical rainforest loses its nutrients in several ways.

First, the enormous biomass of fast-growing plants rapidly absorbs available nutrients.

Second, leaching occurs when heavy rain washes nutrients deep into the ground beyond the reach of plant roots.

Lastly, runoff from frequent rainfall carries nutrients away from the soil's surface.

These processes make rainforest soil surprisingly poor in nutrients despite the lush vegetation it supports.

The nutrient cycle in tropical rainforest is highly sensitive and relies on a delicate balance between the biomass, litter, and soil stores.

Any disruption to the cycle such as deforestation can have serious consequences for the ecosystem.

When forests are cleared, organic matter which then normally replenishes the little layer is no longer added to the soil.

This results in a significant decrease in the nutrients available for plants, further depleting the soil store.

Without plant cover to protect the soil, heavy rainfall can quickly wash away the remaining nutrients in the soil through runoff.

Normally, the dense vegetation helps absorb water and reduce the amount of water that reaches the soil directly.

Without this protective cover, the soil becomes exposed, making it vulnerable to erosion and nutrient loss.

As nutrients are washed away, the soil fertility declines and the rainforest becomes less able to support plant and animal life.

The loss of nutrients from the soil also disrupts the entire nutrient cycle, which can lead to soil degradation and further damage to the ecosystem.

True or false? In the tropical rainforest, nutrients in the soil are rapidly replenished by heavy rainfall, ensuring that soil remains fertile.

Pause the video here whilst you decide and press play when you're ready to continue.

Fantastic, the answer to this question is false.

I would like you to explain why.

Pause here and press play when you're ready to continue.

Fantastic, the reason why this false is because in the tropical rainforest, heavy rainfall leaches nutrients out of the soil.

If the tropical rainforest is deforested, this process is intensified, as the soil is not protected by vegetation.

The soil loses its fertility.

Well done if you explained that correctly.

Why are nutrients recycled quickly in the tropical rainforest? Is it A, the soil in tropical rainforests is nutrient-rich and retains nutrients for long periods; B, warm temperatures and heavy rainfall promote rapid decomposition of organic material; C, tropical rainforests have fewer plants, so nutrients are not heavily used; or D, animals in tropical rainforests consume all nutrients, leaving none to be stored? Pause here whilst you decide and press play when you're ready to continue.

Brilliant, the answer is B.

Warm temperatures and high rainfall promote rapid decomposition of organic material, well done.

I would now like you to complete the grid explaining how different stores gain and lose nutrients in the tropical rainforest nutrient cycle.

We're focusing on the biomass, litter, and soil.

You're talking about how it gains nutrients and how it loses nutrients.

Pause here whilst you attempt this task and press play when you're ready to continue.

Excellent work, let's check our answers.

Your answers may have included some of the following points.

Biomass.

Plants absorb nutrients from the soil, animals get nutrients by eating plants or other animals.

Nutrients are lost from the biomass store to the litter store when plants and animals die and when plants shed leaves.

Litter.

Litter gains nutrients from dead organic matter, including dead plants and animals, and also leaves that fall onto the forest floor.

Nutrients are lost when decomposers break down organic matter, transferring nutrients to the soil.

Runoff also washes nutrients out of the litter store.

Soil.

Soil gains nutrients from decomposing litter and from weathering of rock underneath the soil layer.

Nutrients are lost to the biomass store as plants take up nutrients.

Runoff and leaching also wash nutrients out of the soil store.

Well done if you managed to include those points in your answer.

We're now going to explore our final question of today's lesson, what is a food web? A food web shows how energy and nutrients move through an ecosystem.

It connects different biotic features based on what they eat.

Aisha has said, "Nutrients are being transferred on nitrogen and carbon, is that right?" Yes, Aisha, that is correct.

And Jacob says, "Biotic means living things like plants and animals." A food web shows the relationship between biotic components of an ecosystem.

Producers, plants, are the foundation of the food web, converting sunlight into energy through photosynthesis.

Consumers, animals, depend on plants or other animals for food and include herbivores, carnivores, and omnivores.

Decomposers are fungi and bacteria.

They break down dead matter, recycling nutrients back into the ecosystem.

Producers are at the bottom of the food web in the tropical rainforest.

These include plants and trees which play a crucial role in supporting the entire ecosystem.

Producers use sunlight to make their own food through the process of photosynthesis.

In photosynthesis, plants take in carbon dioxide from the air and water from the soil, and using energy from the sun they produce glucose, a type of sugar, and oxygen.

This glucose serves as energy for the plants themselves, while the oxygen is released into the atmosphere which is essential for the survival of other organisms like animals and humans.

By converting some into food, producers provide the energy base for the rest of the food web.

They're eaten by primary consumers, herbivores, which in turn are eaten by secondary consumers, carnivores, and so on.

The energy flow is vital for sustaining the biodiversity and ecosystem balance in tropical rainforests.

Some examples are coconut trees, banana trees, and bamboo stems. Primary consumers are herbivores in the tropical rainforest and they feed directly on plants and trees to gain energy.

These include insects like leaf cutters and caterpillars as well as larger herbivores like sloths and deer.

By eating plants, primary consumers obtain energy stored in the plant's tissue from photosynthesis.

These herbivores play an important role in the ecosystem by controlling plant populations and serving as food for high-level consumers such as carnivores.

Some examples are macaws, sloths, and grasshoppers.

Secondary consumers in the tropical rainforest are typically carnivores or omnivores.

Carnivores, such as snakes and big cats like jaguars, primarily eat other animals, while omnivores like iguanas or certain small mammals eat both plants or animals.

These secondary consumers feed on primary consumers such as herbivores like insects or sloths.

When secondary consumers consume these primary consumers, the energy stored in the herbivore's body is transferred to the carnivore or omnivores.

This energy is essential for their survival and allows them to grow and reproduce.

Tertiary consumers are the top predators in the rainforest, often referred to as apex predators.

These animals, such as jaguars, harpy eagles, and pythons, are at the highest level of the food chain and have no mutual predators.

Tertiary consumers feed on secondary consumers such as smaller carnivores or omnivores, and transfer the energy from these animals into their own bodies.

This energy helps sustain them, allowing them to grow and hunt and reproduce.

Decomposers like fungi, bacteria, and earthworms play a vital role in the Earth's ecosystem.

By breaking down dead plants and animals, these organisms die, decomposers break them down into their basic nutrients such as nitrogen, carbon, and phosphorus.

This process releases valuable nutrients back into the soil, making them available for plants to use for growth.

Without decomposers, nutrients would be locked in dead organic matter and would not be recycled, which would disrupt the entire nutrient cycle in the ecosystem.

What is the role of a decomposer in a food web? Is it A, to capture sunlight and use it to produce nutrients for herbivores; B, to break down dead organisms and return nutrients to the soil; C, to consume plant tissue and convert nutrients into the litter? Pause the video here whilst you attempt this task and press play when you're ready to continue.

Excellent, the answer is B, to break down dead organisms and return nutrients into the soil, well done.

Identify the correct order of the flow of energy in the tropical rainforest food web.

Is it A, primary consumers to secondary consumers to producers; B, secondary consumers to tertiary consumers to producers; or C, producers to primary consumers to secondary consumers to tertiary consumers? Pause the video here whilst you decide and press play when you're ready to continue.

Excellent, the answer is C, producers to primary consumers to secondary consumers to tertiary consumers.

Well done if you identified that correctly.

All the energy in a food web comes from the sun.

That energy is then transferred through the food web.

Sunlight is the main source of energy for the entire food web.

Producers capture sunlight and convert it into food.

For example, banana trees.

Primary consumers eat the plants to get energy.

For example, fruit bats.

Secondary consumers eat the herbivores.

For example, iguanas.

Tertiary consumers eat both primary and secondary consumers.

For example, fruit bats and jaguars.

And then decomposers break down dead organisms and recycle nutrients back into the soil for plants.

For example, fungi.

The food web in the tropical rainforest is highly complex due to the biodiversity of the ecosystem.

In the rainforest, some consumers like omnivores eat a wide range of plants and animals, which creates multiple links in the food web.

These generalist consumers help connect many different levels of the food web, making the energy flow through the ecosystem more interconnected.

Other consumers are more specialised, depending on only a few specific plants or animals for their food.

For example, some insects may feed only on one type of leaf, or certain predators may only hunt a single species of prey.

These specialised consumers have more limited connections in the food web and their survival depends heavily on the availability of their specific food sources.

The structure of the rainforest food web reflect how each species plays a role in maintaining balance in the ecosystem.

The interconnections between producers, consumers and decomposers make the food web resilient, but also vulnerable to change if certain species are threatened or removed.

Alex has said, "Does that mean the food web shows which organisms are interdependent?" Yes, it does.

Let's place specific animals in a rainforest food web to better understand the interdependence.

At the bottom, we have producers, and then primary consumers, secondary consumers, and then tertiary consumers, which are apex predators.

Aisha has said that if aqua plants die out, this will affect the number of capybaras, and then anacondas, jaguars, and eagles.

This shows interdependence.

In the tropical rainforest, there is a strong interdependence between the abiotic, non-living, and biotic, living, components of the ecosystem.

For example, decomposers like fungi, bacteria and earthworms depend on the warmth and moisture provided by the environment to break down dead plant and animal matter.

If the rainforest becomes drier, the decomposition process would slow down, meaning fewer nutrients would be released into the soil, which could affect plant growth in the entire food web.

Similarly, plants, which are primary producers in the rainforest, rely heavily on regular rainfall.

If there were a reduction rainfall, this would directly impact plant growth.

As plants are the foundation of the food web, a change in their availability would also affect herbivores and other consumers that rely on the food.

This interdependence means that any disruption to the abiotic factors, like changes in rainfall, temperature, or soil quality, can have significant ripple effects throughout the entire ecosystem.

The stability of the rainforest depends on both its biotic and abiotic components working together in balance.

True or false? There is interdependence between biotic, living, elements of ecosystems, but not between biotic and abiotic components.

Pause here whilst you decide and press play when you're ready to continue.

Excellent, the answer is false.

I would now like you to explain why.

Pause here and press play when you're ready to continue.

Fantastic, the reason why this is false is because as well as interdependence between living things, for example, plants and animals, biotic elements also rely on abiotic factors such as sunlight, water, and nutrients.

Well done if you explained that correctly.

I would now like you to explain why tropical rainforest food webs are complex.

You could talk about biodiversity and interdependence in your answer.

Pause here whilst you attempt this task and press play when you're ready to continue.

Excellent work, let's check our answers.

Your answer could include some of the following points.

Food webs show the relationship between biotic components of an ecosystem.

One reason why tropical rainforest food webs are complex is because of the high biodiversity in this ecosystem.

This means there are very large numbers of relationships for food webs to show.

Another reason is interdependence.

While some consumers rely on a wide range of food sources, there are also a lots of relationships that are very specific in the rainforest.

For example, an animal is completely dependent on one specific plant for food.

This combination makes for complex food webs.

Well done if you explained that correctly.

We've now come to the end of our lesson on learning about the nutrient cycle and biodiversity in the tropical rainforest.

Before we finish this lesson, let's summarise everything that we've learned today.

The tropical rainforest is one of the most biodiverse ecosystems on Earth, home to about 50% of the world's species.

This incredible biodiversity is essential to maintaining the rainforest's delicate balance.

Most of the nutrients in this ecosystem are stored in the plants and animals.

When they die, decomposers like fungi, bacteria and earthworms break them down, returning the nutrients to the soil.

However, because the soil in the tropical rainforest is nutrient-poor, plants absorb these nutrients vary quickly, ensuring that the ecosystem continues to thrive.

The food web in the rainforest begins with plants, producers that are eaten by herbivores.

These herbivores are then consumed by carnivores, and the energy continues to flow through the system.

Decomposers play a crucial role in breaking down dead organisms and recycling nutrients back into the soil, which supports plant life.

All parts of the food web are closely interconnected, with each level relying on each other for survival.

This web helps to maintain the complex ecosystem of the rainforest, ensuring that nutrients are recycled, energy flows, and the biodiversity is preserved.

Any disruption to one part of the system can affect the entire ecosystem, underlying the importance of keeping rainforests intact.

Well done on your learning today, you've done brilliantly.

I look forward to learning with you again very soon.