Lesson video

Welcome to this first lesson in the unit living organisms and their environments.

My name's Mr. Jarvis, and I'm gonna be taking you through the lesson today.

Today's lesson is all about components of an ecosystem.

By the end of today's lesson, you should be able to describe how changes in abiotic and biotic factors affect organisms in an ecosystem, and that's going to include how the size of predator and prey populations are cyclical.

There are five key words to today's lesson.

They are ecosystem, community, population, biotic and abiotic.

Here are the definitions coming up on the screen.

You can pause the video if you'd like to read through them, but don't worry, we will go through the definitions as we go through the lesson.

Today's lesson is broken down into three parts.

First, we're going to look at understanding ecosystems. Then we'll move on to talk about the living and non-living components of ecosystems. And finally, we'll talk about predator-prey relationships.

So if you're ready, let's get started with our first section, which is all about understanding ecosystems. So an ecosystem is made up of all the living organisms in a place, and those living organisms all interact with each other, and they interact with the non-living parts of the surroundings.

Ecosystem can be broken down.

Eco relates to the environment, and a system is how a group of things work together.

So ecosystem relates to the environment and talks about how all those parts of the environment work together.

The study of ecosystems is what we call ecology.

Ecosystems can be of any size.

The planet is the largest example of an ecosystem.

Oceans are another large ecosystem, they cover about 70% of the Earth's surface.

But there are many much smaller ecosystems that we can talk about.

For example, a bottle garden can be described as an ecosystem.

Let's do a quick check.

Who has the correct meaning of the word ecosystem? Is it Aisha who says it's the number of one type of organism in a specific place? Is it Sam who says it's all the interacting living organisms and non-living parts in a place? Or is it Jacob, the interacting populations of living organisms in a place? I'll pause for a few seconds and then we'll check to see whether you got the answer right.

The correct answer was Sam, an ecosystem is all the interacting living organisms and non-living parts of a place.

Well done if you got that right.

The living parts of an ecosystem are made up of communities, and a community is the interaction of populations of different species that live in a specific area.

So here's some examples.

You can see all the different plant species that are interacting within this rainforest community.

I'm sure there's many different populations of different animals that are living in that community too that are not shown in the photo.

Here's an African grassland community.

You can see some bushes, some plants in the background, and we've got a number of different types of animals, different populations that are interacting.

And here's a coral reef community.

We've got the coral, which is a living animal.

We've got the seaweeds that are living plants, and we've got all the different populations of different species of fish.

Communities are made up of populations of organisms, and a population is a group of organisms of the same type that live in the same place.

So here again are some examples of populations.

Here we have a population of fruit bats that are living in a tree.

Here is a population of puffins that are living on a clifftop.

And here are a population of poppies that are living in a field.

Ecosystems are complex.

All of the organisms that live within a community rely on each other.

We say that they're interdependent.

Dependent means to rely on, inter relates to between different things, so international is between different nations.

Interdependent are how different species rely on each other.

And organisms within the community interact in different ways, and we've got some pictures on the screen that show different organisms interacting in different ways.

We've got a bee pollinating a strawberry flower.

The strawberry flower is giving food to the bee in the form of nectar.

We've got a frog using the weed in a pond as camouflage, and a snake hunting the frog as food.

We've got dung beetles that rely on animals to produce waste.

They use that waste as places where they can reproduce and also use it as food.

And we've got the ox and the oxpecker that rely on each other.

The oxpecker helps to clean parasites from the skin of the ox and help to keep it healthy.

Plants produce food by photosynthesis.

And remember, plants produce all of the food for the rest of the food chain.

Animals are consumers.

They eat plants, which are producers.

Animals, the consumers, eat other consumers.

Animals pollinate plants and disperse seeds.

Animals use plants for nests and shelter.

And decomposers return nutrients back to the soil that can be used by plants for healthy growth.

All of these are examples of how organisms can be interdependent.

So let's have a check.

Whose idea about ecosystems is correct? Aisha says, "Ecosystems can be of different sizes.

The planet is an ecosystem, but so is a pile of logs." Sam says, "Ecosystems are the communities of living organisms in a place." And Jacob says, "Ecosystems are made up of living things in a place, their interactions with each other and their non-living surroundings." I'll pause for a few seconds and then we'll check to see whether you got the right answer.

The correct answer is Aisha and Jacob.

Ecosystems can be different sizes, and the planet is an example of an ecosystem and so is a pile of logs.

And ecosystems are made up of the living things in a place and their interactions with each other and their non-living surroundings.

Well done if you got that.

Let's move on to our first task of today's lesson.

I'd like you to describe what a community is.

I'd like you to give an example of a community and some of the organisms that you might find within that community.

There's a picture on the screen to help you, if you can't think of a community for yourself.

And secondly, I'd like you to tell me how an ecosystem is different to a community.

You'll need to write down your answers, so you'll need to pause the video, and then when you're ready, press play and we'll check to see how well you've done.

Good luck.

So how did you do? I asked you first of all to describe what a community is, and I'd ask you to give an example of community and some of the organisms that you might find within that community.

A community is made up of all of the organisms that live in the same place.

It's made up populations of different organisms. And one example that you could have chosen would be a woodland community.

And examples of the organisms that you might find include oak trees or elm trees, ferns, mosses and grasses, fungi, that's mushrooms and toadstools, shrews, foxes, rabbits, owls, thrushes, beetles, butterflies and moths, worms, woodlice, spiders, and many, many more.

The second part of the question was, how is an ecosystem different to a community? And an ecosystem includes all of the living things, so they include all of the communities and their interactions.

But it also includes all of the interactions with the organisms and non-living surroundings, and that's why ecosystems are different to communities, because ecosystems include the non-living parts that organisms interact with.

Well done if you got those correct.

That brings us to the second part of today's lesson, which is all about living and non-living components of an ecosystem.

So if you're ready, let's move on.

Ecosystems are made up of all of the living organisms that are in a place, their interactions with each other, and their non-living surroundings.

The living factors that affect communities are called biotic factors.

Biotic means living.

So here's an example of a biotic factor, deer fighting for a mate.

The non-living factors that affect communities are called abiotic factors.

Abiotic means non-living.

And here is an example of an abiotic factor that will affect living things, and that's the availability of water.

Some examples of biotic factors in an ecosystem include availability of food, disease and parasitism, competition within a population for mates, food and shelter.

And you can see here the sea anemones in the picture are competing for that space, that habitat space.

And competition for food and shelter between different species.

So here we've got two birds that are being very territorial and trying to protect their space.

We're going to look at the grey and red squirrel to see how biotic factors can play an important part in how different species are able to exist.

The grey and red squirrel are both different species.

The grey squirrel was introduced in the UK.

It lives in woodlands and eats seeds and nuts.

The red squirrel lives in the UK and has always been native to the UK, and it also lives in woodlands and eats seeds and nuts.

When the squirrels have offspring, the grey squirrel has three to four pups or kits in each litter.

That compares with the red squirrel that only has two or three kits or pups in the litter.

The grey squirrel is immune to the squirrel pox virus, which is a disease which impacts squirrel populations.

The red squirrel has a high death rate.

Grey squirrels are aggressive in their behaviour, whereas red squirrels are shy and tend to hide.

And as a result of all those different things, the grey squirrel, the introduced species is able and continues to out-compete the native species, and so the red squirrel is now endangered in the UK, whereas the introduced species, the grey squirrel is very common across the whole of the country.

Some examples of abiotic factors in an ecosystem include soil type, pH and mineral content, moisture or water levels, wind direction and intensity, carbon dioxide and oxygen concentration, light intensity, temperature, and then human impacted abiotic factors, such as litter and pollution.

As abiotic factors change, some organisms are no longer adapted to their environment, and being adapted means that they have features that help them to survive.

Here's an example a slight increase in sea temperatures has caused what we call coral bleaching, and the bleaching happens as organisms that form the coral die.

And in the picture, you can clearly see that the dark brown colour of living coral has been bleached, and you can clearly see that part of the coral that is no longer living because it's white, and that's a result of increased sea temperature.

So let's do a check.

Laura has been given cards listing some biotic and abiotic factors.

Can you help her to sort them into two piles? One containing the biotic factors and the other containing the abiotic factors.

Here are the cards, light intensity, temperature, competition for territory, parasitism, and moisture content of the soil.

I'll give you a few seconds to try and get your list of biotic and abiotic factors.

You can even pause the video if you need a bit more time, and then we'll check to see whether you've got the answer right.

So the biotic factors are parasitism and competition for territory, and the abiotic factors are the moisture content of the soil, light intensity and temperature.

Well done if you got those.

Changes in biotic or abiotic factors can impact communities and here's an example.

High numbers of yellow-tailed moth caterpillars eat more nettles.

There are fewer nettles to reproduce, so there will be fewer nettles for caterpillars to eat the following year.

And without that food, the moth will not reproduce successfully, and there'll be less food for the yellow-tailed moth's predators, and that's an example of how a biotic factor can impact a community.

Changes in biotic and abiotic factors can impact communities in different ways.

So as an example, changes in pH can impact organisms in communities.

Acid rain is one example of how the pH can change.

It's caused by humans and volcanic activity, and acid rain can kill producers.

Here we've got a picture of some acid rain killed trees that are in a forest.

It can make the soil too acidic for some plants to grow in.

And producers provide the food for all organisms in the rest of the food chain, and so if we kill off all the producers, the animals, the consumers won't have food to eat, and it's an example of how an abiotic factor can impact a community.

Here's another check.

I'd like you to look at the following factors found in an ecosystem, and for each factor decide whether it is either A, abiotic, or B, biotic.

There are four of these questions, and I'll pause between each one.

You need to decide whether the answer is A or B.

The first is competition for food, A or B? The answer is B, it's a biotic factor.

What about this one? Oxygen dissolved in pond water.

Again, biotic or abiotic? This one's an abiotic factor.

Well done if you got that.

What about disease, biotic, abiotic? The answer here is it's a biotic factor.

And the last one, pH of the soil, biotic or abiotic? The correct answer here is it's an abiotic factor.

Well done if you've got all four of those.

Let's move to task B.

We're going to look at this picture of the woodlice.

Here's some facts about woodlice.

They live in dark, damp places, for example, under logs.

They feed on leaf litter.

They breathe through gills, so they need damp conditions.

They have an outer skeleton to protect them from predators.

And they need to shed their exoskeleton, that outer skeleton, in order to grow.

I'd like you to provide examples of two biotic and two abiotic factors that could affect the woodlouse population size.

And secondly, I'd like you to explain how each of those factors that you've named would affect the population size.

You'll need to write down your answers, so you'll need to pause the video at this point when you've got your answer written down, then you can press play and we'll check your answer.

Good luck.

Let's see how you did.

I asked you to provide some examples of biotic and abiotic factors that would affect woodlouse population size, and then to explain how each of those factors would affect the population size.

So let's look at some of the examples that you could have chosen.

So for biotic factors, some possible answers include food, and more food or leaves will allow the population size to increase.

Predation, the more predation that there is, the population decline in size.

And disease and parasites, disease will cause the population to decrease.

Some abiotic factors might include water, because we saw that the woodlice needed damp conditions.

A lack of water will reduce the population, as they need those damp places to help them breathe through their gills.

The temperature, a higher temperature will reduce the population, as woodlice will die as the damp places will become less common.

Well done if you got those.

That brings us to the third and final part of today's lesson, which is all about predator-prey relationships.

So if you're ready, let's carry on.

Predators are organisms that hunt other organisms for food.

Prey are the organisms that they hunt.

Populations of predators and preys are therefore closely linked.

A large number of predators will cause the prey population to decline.

Predator-prey relationships are an example of a biotic factor.

As the number of prey reduces, there's less food for the predators to eat, and so their population decreases.

And as less prey eaten, because the population of predators is small, the more prey can reproduce and increase in number.

And in a stable community, the predator and prey populations rise and fall in linked cycles.

Let's look at an example of this.

As the prey population increases, there's more food for predators, and the population of predators begins to increase.

Then more predators eat more prey.

The population of prey starts to decrease quickly.

As less food is available for the predators, their population begins to decrease too.

A smaller predator population means less prey are eaten.

If there's food available, the prey population begins to increase.

And the predator population will eventually begin to increase again too, and the cycle begins and goes over again.

You might want to pause the video on this screen just to read through and understand the shapes of those graphs and the reason for them.

Then when you're ready, you can press play and move on.

Over a long period of time, both populations fluctuate in cycles, and this type of graph is what we know as a predator-prey model.

Here's an example of it in real life with some real data, and you can see here are the populations of an arctic hare.

The arctic hare population doesn't go up and down smoothly.

It erratically because there are other factors at play that affect the population size.

Here is the population of the Canadian lynx.

The Canadian lynx is the predator of the arctic hare, and you can see how the population of arctic hare also increases and decreases in a linked cycle.

Here's a question.

The rabbit population increases in the summer when the weather is warm.

This is because there's plenty of foods, and so the rabbits reproduce.

Rabbits are food for foxes.

Which of the following statements completes the sentence? As the population of rabbits increases, A, the population of foxes increase, B, the population of foxes stay the same, or C, the population of foxes decrease? I'll pause for a few seconds and then we'll check your answer.

The correct answer is A, as the population of rabbits increase, the population of foxes increases too, and that's because there's lots of food for the foxes to eat.

Well done if you got that right.

Here's our final task for the lesson today.

I'd like you to look at the food chain diagram, grass, deer, tiger.

Here's a graph that shows the size of the deer and the tiger populations.

The deer are in the purple line, the tiger in the pink line.

I'd like you to write a paragraph to explain what happened to the two populations between 2014 and 2016.

You'll need to pause the video, look at the graphs, and then write a paragraph to explain what you think is happening between the two populations of deer and tiger.

When you're ready to check your answer, just press play.

Good luck.

So I asked you to look at the graph of the populations of deer and tiger, and then explain what happened to the two populations between 2014 and 2016.

Grass is the producer in this food chain.

The deer is the consumer or the prey, and the tiger is a consumer and a predator.

Here's the period that I asked you to look at, 2014 to 2016.

What should you have written in your answer? Well, the deer population declined or went down between 2014 and 2016, and the deer population was high in 2014.

That meant that there was plenty of food for the tigers to be able to survive and reproduce successfully.

The tiger population as a result increased between 2014 and 2016.

And the tiger population peaked in 2016, and at this point, less food, a biotic factor, stopped the population from increasing further.

Well done if you got those answers.

That brings us to the summary of today's lesson.

We've seen that ecosystems are made up of all the living organisms in a place and their non-living surroundings.

We've talked about communities being formed by the interacting populations that live in a place, and the interactions between living things are called biotic factors.

Organisms also interact with their non-living surroundings, and these are called abiotic factors.

One example of a biotic factor is how populations of predators and prey in a community are related, and the number of predators and prey in a stable community rise and fall in cycles, and that's known as a predator-prey model.

Thank you for learning with me today.

I hope you've enjoyed the lesson, and I look forward to seeing you all again soon.

Bye-bye for now.